Orthopedics

ABSTRACT

Patellar instability in children and adolescents is a challenging subset to treat. Varied forms of instability, ranging from episodic dislocation to fixed dislocation, have been recognized. It is of utmost importance for the treating physician to recognize these different patterns of instability and their associated risk factors, as more complex patterns of instability would require more extensive surgical procedures. Medial patellofemoral ligament (MPFL) reconstruction, by itself, may not suffice or may not be appropriate for the more complex instability patterns. Appropriate and early treatment of such instability in children would allow for functional progression and possible remodeling of the trochlea. However, early treatment has the associated risk of growth disturbances when surgical procedures are performed around open physis or if adult-type bony procedures are performed in children. Recent knowledge about the relationship between trochlea, MPFL femoral attachment, and distal femoral physis could help to advance safe surgical care for these patients. This article reviews the pathophysiology, risk factors, and the existing classification systems for patellar instability in children and adolescents. It focuses on varied surgical techniques, which are unique to the pediatric population, and summarizes the outcomes of these surgical techniques.

Continue to: EPIDEMIOLOGY

EPIDEMIOLOGY

In a prospective 2-year study of Finnish children, the annual incidence rate of patellar instability was 43/100,000 pediatric population.¹ In patients 9 to 15 years of age, the incidence was approximately 1/1000.¹ In another study, patients at highest risk for a first-time patellar dislocation were females aged 10 to 17 years.² In a study in patients with traumatic hemarthrosis, 36% in the younger age group (10-14 years) and 28% in the older age group (15-18 years) had sustained patellar dislocation. In contrast, 22% in the younger age group and 40% in the older age group had sustained an anterior cruciate ligament tear.³

Approximately one-half of patients who dislocate their patella suffer from long-term complications.^4,5 These complications include recurrent instability, patellofemoral pain, osteochondral lesions, and eventual arthritis.^1,4,5 Young, active individuals are more prone to these issues.⁶ Also, 39% or more of patellar dislocation patients have an associated osteochondral fracture that might influence the management.¹ Thus, patellar instability in young patients is an area of concern.

DEVELOPMENTAL ANATOMY

At 4-week gestation, the patellofemoral joint is an ectodermal sac filled with mesenchyme of the somatic mesoderm.⁷ Mesenchymal condensations then appear at 4 to 5 weeks gestation, followed by chondrification of both the femur and patella.⁷ The joint space is present by 6 weeks, and the patellar and distal femoral condyles are present at 7 weeks gestation.⁷ By 8 weeks gestation, the basic knee anatomy resembles that of an adult with the chondroepiphysis forming the articular surfaces of the femur, tibia, and patella.⁷ By this time, the extensor mechanism is formed, and active joint motion has begun, facilitating the development of the trochlear sulcus.⁷ The secondary ossification center in the distal femoral epiphysis forms around 36 weeks gestation.⁸ Postnatally, both the patella and distal femur grow through endochondral ossification.^9,10

The patella is the largest sesamoid bone in the human body.¹¹ The patella begins as a dense consolidation of cells that differentiate as the quadriceps mechanisms develop.^12,13 The patellar anlage becomes distinguishable within the quadriceps tendon around 7.5-week gestation.¹² The morphology of the patella conforms to the distal femur.¹² The patella molds or re-models as the knee begins to move in response to mechanical stresses.⁷ The patella increases in relative size during the first 6 months of gestation, then enlarges proportionately to the rest of the bones.⁷ Ossification begins around 3 years of age for females and 4 to 5 years of age for males.^8,14 The ossification center may appear irregular as it rapidly expands.¹⁴ Ossification proceeds in a proximal to distal direction, thus giving a spurious estimation of patellar height on radiographs in children. The overall morphology of the cartilaginous patella during development is comparable to the final mature shape.¹⁴ Abnormal contact stresses on the articular surface of the patella during skeletal immaturity can lead to deformation.⁷

Ultrasonographic measurements in normal patients show that trochlear groove (TG) morphology is present early and becomes more radiographically apparent as distal femoral ossification is completed.¹⁵ Anatomic dissections of aborted fetuses have verified the morphology of the TG as it remains constant during growth and the groove morphology is the same for both fetuses and adults.¹⁶ An ultrasound study performed on patients aged 12 to 18 years showed the cartilaginous sulcus angle (CSA) remained constant throughout all age groups (146°).¹⁷ The CSA however, differed in patients who suffered a patellar dislocation (average, 164°; range, 154°-195°) compared with normal knees (average CSA, 145°; range, 131°-158°).^15,17,18 The osseous sulcus angle, on the other hand, appears flat at birth and the TG deepens with age. This increase in depth is more of a reflection of progressive ossification of a well-formed cartilaginous trochlea, rather than a true deepening of the sulcus.¹⁷ Thus, the axial radiographic view of the patella provides misleading information about the sulcus angle in children and should not be used to define trochlear morphology.

Continue to: MEDIAL PATELLOFEMORAL LIGAMENT ANATOMY

The medial patellofemoral ligament (MPFL) functions to limit the lateral translation of the patella.¹⁹ The attachment sites on the femur and patella for the MPFL have been studied in children.^20-23 Cadaveric dissections in specimens aged 2 to 11 years have noted the patellar attachment to be an average of 12 mm in length with the midpoint approximately 5 mm superior to the mid-pole of the patella.²² The patellar footprint of the MPFL insertion was a mean 41% of the entire patellar length.²²

It is important to be aware of the characteristic anatomy of the MPFL, as fixation points should mimic the anatomic insertion as best as possible while also avoiding violation of the nearby physis. The MPFL originates between the adductor tubercle and the medial femoral epicondyle just distal to the distal femoral physis and attaches to the superomedial aspect of the patella.^20-25 In relation to the physis in pediatric patients, the midpoint of MPFL insertion has been measured to be 4 mm to 9 mm distal to the femoral physis.^21,24,25 These measurements represent averages as cadaveric studies have reported that some part of MPFL femoral insertion extends proximal to the distal femoral physis.²¹ A recent report of physeal injury to the posterior distal femoral physis during MPFL reconstruction leading to femoral flexion deformity highlights the importance of physeal-respecting surgery.²⁶

TROCHLEA AND ANTERIOR DISTAL FEMORAL PHYSIS

The relationship between the proximal aspect of the trochlea and the anterior distal femoral physis has been recently studied in 175 knees with dysplastic trochlea.²⁷ Based on magnetic resonance imaging evaluation, the lateral aspect of the trochlea extended proximal to the anterior distal femoral physis in 13% of patients and was at the level of the anterior physis in another 13% of patients (Figure 1).²⁷ Hence, a cautious approach is recommended for any surgery to address trochlear dysplasia or trochlear bump in younger patients to prevent iatrogenic injury to anterior distal femoral physis and resultant genu recurvatum. The distance between the trochlea and the physis increased with increasing age.

LIMB ALIGNMENT

Physiologically, the quadriceps angle (Q angle) changes through the course of growth. As children begin standing and walking, they stand with their feet wider apart and in genu varum.²⁸ Physiologic genu varum can reach 15°.²⁸ This degree lessens during the first 1.5 to 2 years of life, transitioning to physiologic valgus of nearly 12° by 3 years of age.²⁸ Genu valgum, thereafter, gradually decreases to reach the adult value of around 7° to 8° by age 7 years.²⁸ Increased genu valgum is a risk factor for patellar instability. In skeletally immature patients, correction of genu valgum through guided growth may be desirable in patients undergoing patellar stabilization surgery (Figures 2A, 2B).²⁹

PATHOPHYSIOLOGY OF PEDIATRIC PATELLAR DISLOCATION

TROCHLEAR DYSPLASIA

Trochlear dysplasia is an abnormal shape and depth of the TG.³⁰ Up to 96% of patients with patellar dislocation have trochlear dysplasia.^30-33 In a study of patellar instability in children, at least 1 of the 3 signs of trochlear dysplasia (the crossing sign, supratrochlear bump, and double contour sign) was present on lateral radiographs.³⁴ In another study on the growth of trochlear dysplasia in children and adolescents, all grades of trochlear dysplasia were present at all ages (ie, the dysplasia was most likely present at birth and did not necessarily worsen with age and growth).³⁵ The linear dimensions of lateral and medial condylar height as well as trochlear bump increased with age but both the sulcus angle and shape of the trochlea did not change significantly.³⁵ Remodeling of a dysplastic trochlea can happen if the patella is stabilized and appropriately located at a younger age, preferably before 10 years of age.^36,37

Continue to: PATELLAR HEIGHT

The role of patellar height in patellar instability has been well established.³⁸ In patients with patella alta, the patella remains proximal to the TG during the greater arc of knee motion, which predisposes it to patellar instability. Calculation of patellar height in children could be challenging due to incomplete ossification, as well as asymmetric ossification of the patella and the tibial tubercle (TT). Since the patella ossifies from proximal to distal, most radiographic methods that measure the patellar height from the distal aspect of the patella provide a spurious elevation of the measurement.

The Caton-Deschamps (CD) method measures the length of the patellar articular surface and the distance from the inferior edge of the articular surface to the anterosuperior corner of the tibial plateau.³⁹ A ratio >1.3 signifies patella alta. The CD ratio has been verified as a simple and reliable index for measuring patellar height in children.⁴⁰ Two other methods have been described for determining patellar height in children.^41,42 Based on anteroposterior (AP) radiographs of the knee in full extension, Micheli and colleagues⁴¹ calculated the difference between the distance from the superior pole of the patella to the tibial plateau and the length of the patella. A positive difference signified patella alta. The Koshino method involves the ratio between a reference line from the midpoint of the patella to the midpoint of the proximal tibial physis and a second distance from the midpoint of the distal femoral physis to the midpoint of the proximal tibial physis on lateral knee radiographs.⁴² Normal values range from 0.99 to 1.20 with the knee in >30° flexion, in children 3 to 18 years of age.

HYPERLAXITY

In contrast to adults, children have increased levels of collagen III compared with collagen I, which is responsible for tissue elasticity.⁴³ Tissue elasticity leads to increased joint mobility, which is more common in children. Joint hypermobility or hyperlaxity has to be differentiated from symptomatic instability. The traditional Beighton score identifies individuals as having joint hypermobility with a score of 5/9 or higher in school-aged children.^44-46 Smits-Engelsman and colleagues⁴⁴ suggested using stricter criteria with scores of 7/9 or higher being indicative of hyperlaxity in school-aged children. A study of 1845 Swedish school children noted that females have a higher degree of joint laxity.⁴⁵ Maximal laxity was noted in females at 15 years of age.⁴⁵ Hyperlaxity has been demonstrated to be greater on the left side of the body⁴⁴ and can be part of generalized syndromes including Down’s syndrome, Marfan’s syndrome, or Ehlers-Danlos syndrome.

LIMB TORSION

Staheli and colleagues⁴⁷ described the normative values of a lower extremity rotational profile, including femoral anteversion and tibial torsion. Children normally have increased femoral anteversion, which decreases with growth. Miserable malalignment is a term used to denote increased femoral anteversion and increased external tibial torsion.^48,49 These rotational abnormalities can increase the Q angle and the lateral forces on the patella. Femoral anteversion or internal rotation of the femur of 30° significantly increases strain in all areas of the MPFL.⁴⁸ This increased strain may lead to MPFL failure and patellar instability.⁴⁸ Increased internal rotation of the femur also increases contact pressure on the lateral aspect of the patellofemoral joint.⁴⁸ Miserable malalignment frequently manifests following a pubertal growth spurt and may require femoral and tibial osteotomy.⁵⁰

SYNDROMIC ASSOCIATIONS

Several syndromes have patellar instability as a part of their manifestation. The more common syndromes include nail-patella syndrome, Kabuki syndrome, Down’s syndrome, and Rubinstein-Taybi syndrome.^51-54 Other syndromes less commonly associated with patellar instability include Turner syndrome, patella aplasia, or absent patella syndrome. Since many patients with syndromic patellar instability are functionally limited, they may not require an aggressive approach to treatment. When treating these patients, it is important to recognize the unique features of a specific syndrome, which may affect the anesthesia risk profile, management decisions, rehabilitation, and prognosis.

Continue to: MPFL TEAR PATTERN

The MPFL serves as an important constraint to the patella to prevent lateral dislocation, primarily during the first 20° to 30° of knee flexion.^55,56 Injury to the MPFL is noted in over 90% of patients who suffer a patellar dislocation.⁵⁷ The location of MPFL tears in pediatric patients is variably reported at the patellar attachment (10%-61%), femoral attachment (12%-73%), both (12%-35%) or mid-substance (2.5%-15%).^25,57 The most common tear patterns in pediatric patients are tears at the patellar attachment.^25,57 This tear pattern may be accompanied by an avulsion fracture of the medial rim of the patella, though this fracture, being extra-articular, seldom needs treatment.

CLASSIFICATION

While several authors have established extensive classification systems of patellar dislocation based on both clinical and radiographic presentation and reviews of the literature, a single classification system has not been recognized as the gold standard. In this section, in addition to presenting our preferred methods of classification, we will review some of the more recent and extensive classification systems for patellar dislocation and patellar instability.

Dejour and colleagues³¹ initially used both the presence of patellofemoral anatomic abnormalities and pain to define 3 types of patellar instability: major, objective, and potential patellar instability. Major patellar instability indicates that the patient has experienced more than 1 documented dislocation, objective instability involves one dislocation in addition to an associated anatomic abnormality, and potential patellar instability refers to cases in which the patient has radiographic abnormalities and patellar pain.³¹ Garin and colleagues⁵⁸ more simplistically divided patellar dislocation patients into 2 groups: major (permanent or habitual) dislocation of the patella and recurrent dislocation. Sillanpaa⁵⁹ stressed the distinction between first-time dislocation and recurrent dislocation specifically in the context of acute injuries. These classification systems were formulated with adults as the most relevant population; however, classifications targeted specifically to pediatric patients have recently been presented in the literature.

Historically, pediatric patella dislocations were simply categorized as traumatic or congenital.⁶⁰ In 2014, Chotel and colleagues⁶¹ focused on classifying patellar dislocation by extensively reviewing anatomic, biomechanical, pathophysiological, and clinical patterns seen most commonly in children. They included 5 categories: congenital dislocation, permanent dislocation, habitual dislocation during knee flexion, habitual dislocation during knee extension, and recurrent dislocation; however, they did not address traumatic dislocations.⁶¹ Congenital dislocation is a rare condition, typically presenting at birth, which produces a pattern of functional genu valgum.⁶² Permanent dislocation typically presents after the child has started walking, but before the age of 5 years.⁶¹ The 2 variations of habitual dislocation typically present between ages 5 and 8 years.⁶¹ The final category is the most common and typically occurs during pre-adolescence or adolescence as a result of an atraumatic or trivial traumatic event or sports injury.¹ Using more specific terminology, Hiemstra and colleagues⁶³ modeled a classification system based on the traumatic, unilateral, bankart lesion, surgery (TUBS)/atraumatic, multidirectional, bilateral, rehabilitation, inferior shift (AMBRI) for shoulder dislocation classifications. The patellar dislocation system is used to identify 2 distinct subsets of patients in the patellofemoral instability population. One subset is defined by the acronym WARPS (weak, atraumatic, risky anatomy, pain, and subluxation), the other is STAID (strong, traumatic, anatomy normal, instability, and dislocation).⁶⁴ Patients categorized by the WARPS acronym tend to experience atraumatic onsets of patellofemoral instability and demonstrate anatomic issues that increase this instability. These underlying anatomic issues include valgus alignment, ligamentous laxity, rotational abnormalities, shallow and short TG, and patella alta. On the other hand, STAID patients describe a traumatic dislocation event and do not have underlying anatomic abnormalities that predispose them to instability.⁶⁴

Taking into account these previous classifications, Frosch and colleagues⁶⁵ added specific pathologies including “instability,” “maltracking,” and “loss of patellar tracking,” in addition to both clinical and radiographic factors to define 5 types of patellar dislocation and their specific treatment recommendations.⁶⁵ Type 1 involves simple dislocation with neither maltracking nor instability and a low risk of redislocation.⁶⁵ Type 2 is defined as primary dislocation followed by subsequent high risk of dislocation and no maltracking.⁶⁵ Type 3 is divided into 5 subcategories of instability and maltracking issues involving soft tissue contracture, patella alta, pathological tibial tuberosity, and TG distance.⁶⁵ Type 4 is defined as the highly unstable “floating patella,” and type 5 involves patellar maltracking without instability ⁶⁵. In terms of treatment, conservative rehabilitation is recommended for type 1 whereas MPFL reconstruction tends to show positive outcomes for both types 2 and 3.^66-70

Continue to: Parikh and Lykissas recently published...

Parikh and Lykissas recently published a comprehensive classification system of 4 defined types of patellar dislocation in addition to voluntary patellar instability and syndromic patellar instability (Table).⁶⁰ The 4 types are Type 1, first-time patellar dislocation; Type 2, recurrent patellar instability; Type 3, dislocatable; and Type 4, dislocated. Type 2 is further subdivided into Type 2A, which presents with positive apprehension signs, and Type 2B, which involves instabilities related to anatomic abnormalities.⁶⁰ A distinction is also made between Type 3A or passive patellar dislocation and Type 3B habitual patellar dislocation.⁶⁰

The classification system proposed by Green and colleagues is more simplified with 3 main categories (Table) of pediatric patellar dislocation: traumatic (acute or recurrent), obligatory (either in flexion or extension), and fixed laterally.^71,72 The acute traumatic categorization refers to patients who experienced an initial dislocation event due to trauma whereas recurrent traumatic involves repeated patella dislocations following an initial incident. Studies report that between 60% to 70% of these acute traumatic dislocations occur as a result of a sports-related incident.^2,33,73 Obligatory dislocations occur with every episode of either knee flexion or extension, depending on the subtype. Obligatory patella dislocation in flexion typically cannot be manipulated or relocated into the trochlea while the knee is fixed but does reduce into the trochlea in full extension. Fixed lateral dislocations are rare, irreducible dislocations in which the patella stays dislocated laterally in flexion and extension. These dislocations often present with other congenital abnormalities. Each of these categories can be further specified as syndromic if the dislocation is associated with genetic or congenital conditions including skeletal dysplasia, Ehlers-Danlos syndrome, cerebral palsy, Marfan disease, nail-patella syndrome, Down syndrome, Rubenstein-Taybi syndrome, and Kabuki syndrome.^{51-54,61,74-76}

SURGICAL TECHNIQUES IN SKELETALLY IMMATURE PATIENTS

While nonsurgical, conservative treatment involving physical therapy and activity modification is recommended for most patients who experience first-time traumatic patellar dislocations, many patients experience complicating factors that indicate them for surgery. These factors include recurrent dislocation, risk factors for patellofemoral instability, underlying malalignment issues, and congenital deformities. When evaluating these factors, particularly patellofemoral instability, the authors recommend assessing osteochondral lesions, age, skeletal maturity, number of previous dislocations, family history, and anatomic risk factors.^2,5,77-79 Extra care should be taken when considering surgical treatment for skeletally immature patients at elevated risk for recurrent instability as the risk of cartilage damage in these cases is high.^80-82

Recently, there has been a reported increase in surgical treatment for patellar instability in the skeletally immature.⁸³ This finding may be attributed to heightened awareness of factors that indicate patients for surgical treatment and increased familiarity of surgeons with newer techniques.⁸³ Many surgical techniques have been described to address patellar instability involving both soft-tissue procedures and bony corrections.⁸⁴ In this article, we discuss the various surgical techniques for MPFL reconstruction, quadricepsplasty, and distal realignment. These procedures can be paired with any number of additional procedures including, but not limited to, lateral retinacular release or lengthening, chondroplasty, TT osteotomy (in skeletally mature patients), and removal of loose bodies.⁸³

There is a need for more comprehensive studies, particularly randomized controlled trials, to evaluate the outcomes for both surgical and nonsurgical treatments for first-time dislocations. In the current literature, only very recently have surgical treatments shown outcomes that are more positive. In 2009, Nietosvaara and colleagues⁸⁵ conducted a randomized controlled trial of nonoperative and operative treatment of primary acute patellar dislocation in both children and adolescents. After a long-term mean follow-up of 14 years, there was not a significant difference between the groups in recurrent dislocation and instability, subjective outcome, or activity scores.⁸⁵ In a subsequent review of 5 studies including 339 knees, Hing and colleagues⁸⁶ also found similar results in both the operative and nonoperative cohorts at risk of recurrent dislocations, Kujala scores, and reoperations. However, a recent systematic review comparing redislocation rates and clinical outcomes between surgical and conservative management of acute patellar dislocation reported more positive outcomes for the surgical cohort.⁸⁷ This review included 627 knees, 470 of which received conservative management, 157 of which received operative treatment. The conservative cohort was followed for an average of 3.9 years and had a 31% rate of recurrent dislocation while the surgical group was followed for a mean 4.7 years and experienced a 22% redislocation rate.⁸⁷ This study indicates that operative management for acute first-time dislocations may be the preferred treatment option.

Continue to: A potential reason some of these studies...

A potential reason some of these studies did not show any significant difference between the operative and nonoperative cohort could be that the surgical cohorts included a wide range of procedures including lateral releases and MPFL repairs. Recent publications have indicated that these techniques do not produce overall positive outcomes. While each surgical treatment plan is unique depending on the patient; recently, MPFL reconstruction has been shown to have better outcomes than both nonoperative management and simple medial repair and/or lateral
release.^67,88-90

MPFL RECONSTRUCTION

INDICATIONS/OVERVIEW

The MPFL is an important stabilizer for the knee that primarily resists lateral translation of the patella. Damage to the MPFL is very common in acute patellar dislocations with up to 90% of first-time dislocations resulting in injury to the MPFL.^91,92 Historically, simple medial and/or lateral MPFL repairs have not been shown to improve patellofemoral kinematics significantly and often result in recurrence.^90,93 To address this issue, during the past few decades, numerous MPFL reconstruction techniques have been developed to reconstruct a stronger ligament with the same kinematics as the anatomic MPFL.^{2,19,69,81,94-106} The ultimate goal of MPFL reconstruction is to reestablish the anatomic “checkrein” to guide the patella into the trochlea between 0° and 30° of knee flexion.^107,108 An essential secondary surgical goal in skeletally immature patients is to avoid damaging the distal femoral physis.

There are many variations in both the grafts used to replace the MPFL and the means by which to secure them. The ones discussed below include free semitendinosus or gracilis autografts or grafts constructed from a pedicled adductor, patellar, or quadriceps tendon.^69,105,109 While not used as frequently, allografts have also been used.¹¹⁰ Methods to secure these grafts in osseous tunnels include suture anchors or tenodesis screws. Incomplete osseous sockets or medial-sided bone tunnels have also been used as a method to decrease patellar fractures as they preserve the lateral patellar cortex.^111-114

DOUBLE-BUNDLE HAMSTRING AUTOGRAFT

The technique most often used by the author is a double-bundle hamstring autograft harvested from either the semitendinosus or the gracilis secured by short patellar and femoral sockets (Figure 3). After harvesting the hamstring graft from a posteromedial incision, an approximately 90-mm graft is prepared with Krackow stitches to secure 15 mm of the tendon in each socket.¹¹⁵ Lateral radiographs are used intraoperatively to ensure the guidewire for the femoral drill hole falls along the posterior cortex of the diaphysis of the femur while AP radiographs confirm placement distal to the physis. It is important to take both AP and lateral radiographs intraoperatively due to the concave curvature of the distal femoral physis. This unique anatomy can make a point that is located distally to the physis on the AP view appear on or proximal to it on the lateral cross reference view.^24,116 For the patellar socket, 2 short sockets are made in the superior half of the patella. Once the sockets have been drilled, the graft is adjusted so that the patella stays seated in the center of the trochlea between 20° and 30° of flexion. This anchoring is accomplished by securing the graft while the knee is kept at 30° of flexion. Proper tension is confirmed by ensuring that the graft does not allow lateral patella movement over one-fourth the width of the patella in extension while crepitation must not appear throughout the ROM.⁹²

QUADRICPETS TENDON TRANSFER

A combination of techniques by Steensen and colleagues,¹⁰⁵ Goyal,¹⁰⁹ Noyes and Albright,¹¹⁷ and Pinkowsky and Hennrikus¹¹⁸ describe an MPFL reconstruction in which the proximal end of a small medial portion of the quadriceps tendon is released and then attached to the medial epicondyle through a subcutaneous tunnel (Figure 4). This technique is particularly useful for cases in which the extra strength provided by the bone-quadriceps tendon is necessary to correct more severe dysplasia. Leaving the distal end of the quadriceps tendon intact at its patellar insertion, a graft of about 8 mm x 70 mm thickness is harvested from the tendon. The free distal end of the tendon is then run anatomically through the synovium and retinaculum to be either sutured to the medial intermuscular septum at the medial femoral epicondyle or fixed in femoral tunnel using interference screw.^105,109,118 The placement of the femoral fixation point is essential to ensure positive surgical outcomes. If the graft is secured too anteriorly, it may be too loose in extension and too tight in flexion, both of which can lead to postoperative pain, loss of normal kinematics, and overload of the medial patellofemoral cartilage.^119-121 Once the ideal placement of the femoral fixation point has been confirmed by intraoperative radiographs, the graft is secured with a small absorbable suture.^122,123 While this technique has good clinical results, the longitudinal scar that results from graft harvesting is cosmetically unappealing, and it is technically challenging to harvest a consistent strip of the quadriceps tendon. To address some of these concerns, Fink and colleagues¹²⁴ described a new harvesting technique that produces more consistent grafts and requires a smaller incision.

Continue to: ADDUCTOR MAGNUS TENDON TRANSFER

This technique is a double-bundle MPFL reconstruction that uses a pedicled graft of the distal adductor magnus tendon and suture anchors or incomplete osseous sockets to recreate the MPFL anatomically (Figure 5). Avikainen and colleagues⁹⁶ and Sillanpää and colleagues¹²⁵ described this procedure as a progression from the original single-strand adductor magnus transfer technique. First, maintaining the distal insertion, a graft of approximately 14 cm to 18 cm is harvested from the adductor tendon and then passed through a subcutaneous tunnel between the distal vastus medialis obliquus and the superficial joint capsule. The graft is then looped at the medial patella so that the distal bundle runs back to the adductor tubercle.¹²⁵ With the knee at 30° of flexion to assure proper tension, the graft is secured at both the patella and near the adductor tubercle with suture anchors.¹²⁵ Hambridge and colleagues¹²⁶ compared a similar adductor magnus transfer with other pedicled techniques including bone-quadriceps tendon autograft and bone-patellar tendon allograft and found positive results for all 3 methods of reconstruction.

HEMI-PATELLA TENDON TRANSFER

In a similar technique to the adductor tendon transfer, the medial section of the patellar tendon is harvested from the TT and run from its proximal insertion at the medial patella to the medial femoral attachment via a subcutaneous tunnel. The free end of the graft is then secured with suture anchors or incomplete osseous sockets with the knee at 30° of flexion.¹²⁷

HAMSTRING GRAFT WITH ADDUCTOR TENDON AS A PULLEY

Several techniques opt to use a more dynamic model of MPFL reconstruction in which the adductor tendon or medial collateral ligament (MCL) is used as a pulley for the hamstring graft (Figure 6).^128,129 The site of the pulley approximates the normal attachment of the MPFL to the femur and so acts as an effective anatomic replica of the MPFL origin. A semitendinosus graft is harvested and is prepared with continuous sutures, and 2 tunnels to secure the graft are drilled into the patella. The graft is then run subcutaneously from the medial side of the patella to the adductor magnus tubercle into which an osteoperiosteal tunnel is drilled at its distal femoral insertion. The graft is looped through the adductor tunnel and secured with sutures. Proper knee kinematics was ensured by placing the knee at 30° of flexion as the ends of the tendon are secured to the patella.^114,130

HAMSTRING GRAFT WITH MCL AS A PULLEY

The MCL can also be used as a pulley rather than the adductor tendon. The semitendinosus graft is harvested and prepared and the patella drilled as it is in the previous technique. The MCL was fashioned into a pulley by making a slit in its posterior one-third. The semitendinosus graft is looped through this slit, and both ends of the graft are held in place with suture anchors on the surface of the patella.¹²⁹

ADDITIONAL PROCEDURAL COMBINATIONS

Depending on the needs of the individual patient, MPFL reconstruction, and other patellar stabilization techniques can also be combined with additional procedures. Arshi and colleagues⁸³ conducted a review of 6190 adolescents surgically treated for patellar instability and reported the most common additional procedures performed at the time of the stabilization. They found 43.7% of the population underwent lateral retinacular release, which while not effective as an isolated technique to treat patellar instability, has often been used in combination with MPFL reconstruction.^131-133 There is currently a lack of consensus regarding the success of adding a lateral release to the reconstruction. Some studies report no difference while others report a decrease in stability after lateral release.^90,134-136 While lateral retinacular release has been shown to decrease the force required to displace the patella, it can be surgically indicated in certain patients undergoing MPFL reconstruction.¹³¹ The authors advocate that if the lateral retinaculum is tight such that centralized patellar tracking is inhibited following the reconstruction, or if the patella cannot be pushed passively from a laterally tilted position to the neutral horizontal position, lateral retinacular lengthening should be performed to improve kinematics.¹³²

Continue to: Arshi and colleagues...

Arshi and colleagues⁸³ also reported a high rate of cartilage procedures, with chondroplasty performed in 31.1% and chondral fragment/loose body removal in 10.2%. These statistics suggest that a significant level of cartilage damage has occurred by the time of surgery.⁸³

COMPLICATIONS

As MPFL reconstruction techniques have only recently been popularized and developed, there are not many comprehensive studies evaluating the outcomes and complications associated with these procedures. However, in the current literature, there is a general consensus that patients usually experience positive short-term clinical outcomes and relatively low complication rates.^68,77 In one of the largest retrospective cohort studies of pediatric patients undergoing MPFL reconstruction, Parikh and colleagues¹¹⁴ reported both the type and rate of complications. They found complications occurred in 16.2% of patients, and the most common complications were recurrent patellar instability, patellar fractures, patellofemoral arthrosis, motion deficits, and stiffness with over half classified as avoidable. Most of these complications were due to technical errors with episodes of recurrent instability only reported in 4.5% of patients.¹¹⁴ In a comprehensive meta-analysis of MPFL reconstruction studies, Shah and colleagues¹³⁷ reported a complication rate of 26% in both pediatric and adult patients. The cohort was not stratified by age, yet complications were similar to those reported by Parikh and colleagues,¹¹⁴ including pain, loss of knee flexion, wound complications, and patellar fracture.¹³⁷

As indicated by the frequency of technical complications reported by Parikh and colleagues,¹¹⁴ extra caution should be taken in the operating room to minimize potential errors. In techniques that require drilling of femoral sockets, proper length for and placement of the graft is essential to reestablish proper kinematics. Studies have reported that placing the femoral socket too proximally can result in loss of ROM during flexion and increased compressive forces across the patella.¹³⁸ A graft that is too short can have similar negative outcomes, and a graft that is too long can result in recurrent instability. Positioning the graft while the knee is in 30° of flexion can help ensure the proper length and tension is achieved. Once the graft is in place, it is important to ensure the ROM and isometry before completing the fixation.⁷² It is also essential to be vigilant about potential violation of the physes and subsequent growth disturbances. To establish the safest angles for drilling the distal femoral epiphysis for graft placement, Nguyen and colleagues¹³⁹ conducted a study using high-resolution 3-dimensional images of cadaveric distal femoral epiphyses. By recording which tunnels disrupted the physis before reaching 20 mm of depth, the authors concluded that it is safest to drill distally and anteriorly at an angle between 15° and 20°.¹³⁹ This technique should minimize damage to the physis, notch, and distal femoral cartilage and decrease potential complications.¹³⁹

OUTCOMES

In general, the literature reports positive outcomes for MPFL reconstruction—in both studies that address a specific technique and all-encompassing studies. Outcomes are typically reported as Kujala and Tegner scores, results from clinical examinations, and rates of subsequence recurrences. Several recent studies have also evaluated the ability of MPFL reconstruction to restore proper kinematics. Edmonds and colleagues¹⁴⁰ evaluated the difference in patellofemoral joint reaction forces and load experienced by 3 groups of adolescents: a cohort treated with MPFL reconstruction, a cohort treated with soft-tissue realignment of the extensor mechanism (the Insall method), and controls. While both surgical techniques were able to restore medial constraints to the patella, the study showed that only the MPFL reconstruction cohort experienced joint reaction forces that were analogous to the control group. In comparison, the cohort that was treated with soft-tissue realignment alone experienced higher patellofemoral joint reaction forces and did not regain normal joint mechanics.¹⁴⁰ These results can be used to advocate for the further use of MPFL reconstruction as an effective anatomic replacement of the native ligament. Radiographic studies have similarly reported MPFL reconstruction as an effective means to restore anatomic normality. Fabricant and colleagues¹⁴¹ conducted a radiographic study in which patella alta was corrected to normal childhood ranges in patients who underwent MPFL reconstruction technique using a hamstring autograft. Lykissas and colleagues¹⁴² corroborated these results with another radiographic study that reported small but significant decreases in the Blackburne-Peel index and CD index following MPFL reconstruction in 25 adolescents. As correction of patella alta allows the patella to rest in a deeper, more secure position in the TG, these results indicate that effective early MPFL reconstruction can correct for patellar anatomic abnormalities that could be future risk factors.^143,144 Several studies have also reported outcomes addressing specific MPFL techniques; these are reported and discussed in this article.

OUTCOMES BY TECHNIQUE

HAMSTRING AUTOGRAFT

Reports on outcomes following MPFL reconstructions using hamstring autografts have been particularly promising. A cohort of 21 skeletally immature patients who underwent MPFL reconstruction was evaluated pre- and postoperatively with an average of a 2.8-year follow-up. The authors of the study reported no redislocation events and significant improvement in the Kujala scores, and patients were able to return to athletic activities safely.¹⁴⁵ Previous studies report similar positive increases in Kujala scores, subjective patient reports, and lack of subsequent redislocation for patients who underwent either semitendinosus or gracilis autograft MPFL reconstructions. One such study further documented an average patellar inclination angle decrease from 34.3° to 18.6° following MPFL reconstruction.¹⁴⁶ However, while the literature typically reports positive Kujala scores and subjective outcomes for the hamstring autograft procedure, a study arthroscopically evaluating patellar tracking immediately following surgery and then at 6 to 26 months follow-up found that patellar tracking correction was not maintained for all patients who underwent this type of MPFL reconstruction.¹⁴⁷

Continue to: QUADRICEPS TENDON TRANSFER OUTCOMES

Studies specifically evaluating the quadriceps tendon transfer technique for MPFL reconstruction in children are sparse, but authors have reported positive clinical outcomes and low complication rates in adults. After following 32 young adults who underwent this MPFL reconstruction technique for 3 years, Goyal¹⁰⁹ reported a significant increase in mean Kujala scores from 49.31 to 91.25 and no complications or redislocation. He argues this type of quadriceps graft has a high success rate because it is anatomically more similar to the MPFL than other grafts and does not require additional patellar fixation.^101,109 Similar positive Kujala scores and minimal complications have been reported in adult patient populations.¹⁴⁸ Abouelsoud and colleagues¹⁴⁹ conducted one of the few studies in skeletally immature patients and reported similarly positive results with no redislocations and significantly improved Kujala scores at a mean follow-up of 29.25 months in their 16-patient cohorts.

ADDUCTOR MAGNUS TENDON TRANSFER

After initially describing this technique in 14 adult patients, Avikainen and colleagues⁹⁶ followed this cohort and reported positive subjective results and only 1 redislocation. In a more recent study in which the adductor tendon transfer technique was compared with the quadriceps tendon transfer described above and the bone-patellar tendon allograft, Steiner and colleagues⁶⁹ reported similarly significant improvement in all cohorts in Lysholm, Kujala, and Tegner scores with no redislocations. Additionally, Malecki and colleagues¹⁵⁰ followed a cohort of 33 children with 39 knees diagnosed with recurrent patellar dislocation, who underwent MPFL reconstruction using the adductor magnus tendon. After evaluating this cohort functionally and radiographically, the authors reported improvements in Lysholm and Kujala scores, patellar tilt and congruence angles, and peak torque of the quadriceps muscle and flexor.¹⁵⁰ However, this cohort did report postoperative redislocations in 36.4% of patients (4 of 11).¹⁵⁰

HEMI-PATELLA TENDON TRANSFER

In 2012, in the first randomized controlled trial, Bitar and colleagues⁶⁷ compared the outcomes of patients who underwent MPFL reconstruction via the hemi-patellar tendon technique with those who were managed nonoperatively with immobilization and physiotherapy after first-time patellar dislocation. At 2-year follow-up, the surgical cohort presented positive results with a significantly higher mean Kujala score (88.9 to 70.8) and no redislocations or subluxations. In contrast, 35% of nonoperative cases presented with recurrences and subluxations over the 2-year period.⁶⁷

MCL OR ADDUCTOR TENDON AS A PULLEY

Studies have reported good postoperative results and low complication rates for these dynamic techniques.^128,129 In terms of kinematics, while hypermobility and patellar height were not fully corrected, improvements in patellar tilt and lateral shift were reported in a cohort of 6 patients with a minimum 4-year follow-up.¹²⁹ To further evaluate whether the more dynamic pulley reconstruction technique resulted in better outcomes, Gomes and colleagues¹²⁸ compared the subjective reports, clinical evaluations, and complication rates of patients who underwent MPFL reconstruction with a rigid adductor magnus fixation vs a semitendinosus tendon dynamic femoral fixation. One case in the rigid cohort experienced a subsequent subluxation, while patients in the semitendinosus group had better subjective reports and a higher rate of return to sport.¹²⁸ More recently, Kumahashi and colleagues¹⁵¹ specifically studied the outcomes of the MCL tendon as a pulley in 5 patients aged 14 to 15 years. They reported similar successful results as no patients experienced recurrence, and all patients exhibited improvement in radiographic measures of patellar tilt and congruence angle, lateral shift ratio, and both Kujala and Lysholm scores.¹⁵¹

While there has yet to be a randomized controlled trial comparing all of these different techniques, there is a general consensus in the literature that patients tend to perform better following MPFL reconstruction vs MPFL repair.

OTHER STABILIZATION PROCEDURES, INCLUDING DISTAL REALIGNMENT

Patients with additional underlying deficits and malalignment issues such as significant trochlear dysplasia, increased TT-TG distance, patella alta, increased Q angle, and/or positive J sign may require stabilization procedures beyond MPFL reconstruction.^152,153 TT osteotomies are often used to correct alignment issues in the adult patient population; however, these procedures are typically contraindicated in skeletally immature patients. Alternative realignment procedures for the pediatric population include both proximal and distal realignment, with proximal realignment performed primarily in children under the age of 12 years.¹⁵³ Many variations on these procedures exist, some of which are no longer regularly performed due to poor reported outcomes. In this article, we discuss several of the techniques, focusing primarily on those that have demonstrated higher success rates.

Continue to: GALEAZZI TECHNIQUE

One of the first and most famous soft-tissue techniques to address patellar instability was the semitendinosus tenodesis, published by Galeazzi¹⁵⁴ in 1922 (Figure 7). This technique stabilizes the patella without altering the TT. In the original technique, a portion of the semitendinosus tendon is harvested with its tibial insertion left intact. The free end of the tendon is then secured with sutures at the periosteal groove of the medial patella.^154,155 Fiume¹⁵⁶ modified this technique by adding a lateral release and medial retinacular reefing. The most recent addition to this procedure was introduced by Baker and colleagues,¹⁵⁷ in which a tunnel is drilled from the medial to the lateral border of the patella. Tension placed on the grafted tendon is used to reposition the patella medially and draw it downward. Preliminary literature on this modified procedure reported fair clinical results with success rates of approximately 75%.^155,158-160 A recent study evaluating both the clinical and radiographic outcomes of this technique also indicated that while clinical results were excellent in 62.5% of patients, this technique alone was unsuccessful in fully addressing patellar instability in patients with underlying anatomic abnormalities such as patellar alta.¹⁶¹ In light of these less than ideal reports, the authors no longer recommend this technique for patellofemoral instability cases.

ROUX-GOLDTHWAIT PROCEDURE

The Roux-Goldthwait procedure, first described by both Roux¹⁶² and Goldthwait¹⁶³ in 1888 and 1895 respectively, was later modified in 1985 to involve a lateral release, plication of the medial retinaculum, medial transfer of the lateral patellar tendon without advancement, and advancement of the vastus medialis (Figure 8).¹⁶⁴ More recently, Marsh and colleagues¹⁵² introduced an addition to aligning the extensor mechanism with the femoral shaft better. In this technique modification, the patellar tendon is split longitudinally, and its lateral half is detached and transferred distally beneath its medial half. The free end is then sutured to the periosteum on the medial side of the tibia.¹⁵² With a mean long-term follow-up of 6.2 years, Marsh and colleagues¹⁵² reported excellent results in 65%, good in 11%, and fair in 3% of the knees operated on with this modified technique. Of the patients in this cohort whose strength was evaluated, 80% had their strength returned to 90% of preoperative levels in the operated leg.¹⁵² While this study and others report improved outcomes, an increasing body of literature has found high rates of recurrence, patella infera, and other complications following the modified Roux-Goldthwait procedure.^36,165-171 Also, a study comparing MPFL reconstruction using adductus magnus transfer with the Roux-Goldthwait procedure reported that patients in the MPFL cohort reported less pain postoperatively.¹⁵⁰ In addition, whereas the Kujala and Lysholm scores, recurrence rates, patellofemoral angles, and apprehension test results did not demonstrate significant differences between these 2 groups, the MPFL group had significantly fewer abnormal congruence angles, better patellar medialization, and higher peak torque of the hamstring.¹⁵⁰

COMBINED MPFL AND MEDIAL PATELLOTIBIAL LIGAMENT RECONSTRUCTION

While the medial patellotibial ligament (MPTL) has not received much attention with regard to patellar stability, recent studies have indicated its role during higher degrees of both flexion and extension.¹⁷² The MPTL acts as a secondary restrictor ligament which helps release stress on the MPFL by decreasing the Q angle and further normalizing patellar kinematics.¹⁷³ Patients who present with hyperlaxity or knee hyperextension combined with extension subluxation and flexion instability could be indicated for this additional stabilizing procedure. Both Nietosvaara and colleagues⁸⁵ and Brown and Ahmad¹⁷⁴ have described a dual MPTL and MPFL reconstruction technique using a semitendinosus hamstring graft. More recently Hinckel and colleagues¹⁷² described a combined MPFL and MPTL reconstruction, using a graft from the quadriceps tendon to reconstruct the MPFL and one from the patellar tendon to reconstruct the MPTL. In this technique, once the respective grafts have been harvested, a femoral insertion for the graft recreating the MPFL is fluoroscopically established so that an anchor can be inserted distal to the femoral physeal growth plate. For the MPTL insertion, attachment to the tibia below the joint line and 2 cm medial to the patellar tendon is established fluoroscopically just above the physeal growth plate on the proximal epiphysis.^19,175 The MPTL graft is sutured first with the knee at 90° of flexion to establish tension similar to that of the patellar tendon.¹⁷⁶ Then, the knee is placed in 30° of flexion to fix the MPFL graft to the medial patella to prevent excessive lateral translation of the patella.

PATELLAR TENDON TRANSFER

Patellar tendon transfer with proximal realignment is a technique used in particularly young patients to address cases of patellofemoral instability involving concomitant bony or anatomic abnormalities. This procedure is effective for young children with substantial amounts of remaining growth as it better mimics native anatomy than other realignment procedures and does not require bony remodeling.^152-154 It is important to familiarize with surgical techniques to address malalignment issues in young patients as neglected alignment issues can lead to worsening of trochlear dysplasia and instability, which are very difficult to treat later on when patients are older.¹⁵³

The patellar tendon transfer technique (Figure 9), as described by Gordon and Schoenecker,¹⁷⁷ starts with an extensive lateral retinacular release. The patellar tendon is then released from its distal insertion at the TT so that it can be moved medially without moving it inferiorly. After confirming patellar tracking and alignment by flexing the knee from 0° to 90° with the graft in place, the patellar tendon graft is secured with multiple nonabsorbable horizontal sutures.¹⁷⁷ Of note, in skeletally mature patients, a TT osteotomy is used to accomplish the same goal. This osteotomy has been shown to improve both patellar height and TT-TG distance in skeletally mature patients, but is contraindicated in skeletally immature patients.^92,178

Continue to: Initial studies conducted on patellar tendon...

Initial studies conducted on patellar tendon transfer have positive outcomes.¹⁷⁹ At a mean follow-up of 5.1 years, patients reported a decrease in pain and increased the ROM and activity, and only 1 reported a postoperative redislocation.¹⁷⁹ In more recent studies, both Benoit and colleagues³⁶ and Garin and colleagues⁵⁸ reviewed cases of patellar instability treated with patellar tendon transfer to address concomitant patellar alignment and anatomic abnormalities. They reported good functional, clinical, and radiographic outcomes with 12.5% and 16% recurrence rates, respectively.^36,58 They also noted radiographic improvements in femoral sulcus angle, particularly in younger patients, which indicate this procedure is effective in addressing bony abnormalities that can result from neglected malalignment issues.^36,58,154

QUADRICEPSPLASTY

Quadricepsplasty is a lengthening and remodeling technique not frequently used in the pediatric population. The goal of this procedure in patients with significant amounts of growth remaining is to reposition the patella to ameliorate trochlear remodeling and prevent worsening symptoms and anatomic abnormalities.³⁶ A quadricepsplasty accomplishes this by de-rotating and/or lengthening the extensor mechanism and may or may not involve a concomitant MPFL reconstruction. This procedure is particularly effective in young patients who experience obligatory dislocation.^60,72 Several quadricepsplasty techniques have been described including Thompson, Curtis and Fisher, Judet, Stanisavljevic, and V-Y technique.^180-186 Most techniques initially involve sharp dissection of the vastus medialis and lateralis from the rectus femoral tendon. A tongue is then fashioned out of the rectus femoral tendon. Once the vastus medialis and lateralis are detached from the margins of the patella, the knee is extended, and the distal ends of the vasti are sutured to the tongue of the rectus tendon. Effective extension facilitates flexion to 90°.¹⁸⁴ The authors recommend a modification of this technique in which a Z lengthening of the quadriceps tendon is performed after the vastus lateralis is removed distally from the patella and the quadriceps tendon.

Several series and case reports evaluating quadricepsplasty in adult patients report positive outcomes with most patients achieving good or excellent flexion with minimal complications.^{183,185,187-189} Reports on quadricepsplasty used to treat conditions other than patellofemoral instability in children have reported similar positive outcomes.^190-192 As quadricepsplasty for patellar instability is relatively rare in pediatric patients, there is not much relevant literature. However, Kocon and colleagues¹⁹³ reported results of quadricepsplasty and quadricepsplasty combined with the modified Galeazzi procedure in 8 children (10 knees) with a mean follow-up of 3.25 years. Seventy percent of cases resulted in stabilization and correction of patellar position, and only 2 postoperative redislocations were noted.¹⁹³ Additionally, in a study evaluating 6 patients suffering from patellar instability, 2 of whom were obligate dislocators, quadricepsplasty resulted in patellar stability, satisfaction, and near normal gait patterns.¹⁹⁴

Figure 10 shows the surgical algorithm used for patellar instability characteristics.

CONCLUSION

Patellofemoral joint stability relies on a complex interplay of musculotendinous units, ligaments and the osteocartilaginous morphology of the patellofemoral joint. Patellar instability in pediatric patients is different from adults. Having an in-depth understanding of the remodeling potential, the insertion sites for the MPFL and its relationship to the physis are of utmost importance when planning surgery. Reducing and maintaining the patella within the patellofemoral joint early enough can allow for remodeling of the patella and/or the trochlea to provide for lasting stability. Appropriate surgical principles, such as tensioning, can help both prevent continued pain and minimize future complications.

ABSTRACT

Patellar instability in children and adolescents is a challenging subset to treat. Varied forms of instability, ranging from episodic dislocation to fixed dislocation, have been recognized. It is of utmost importance for the treating physician to recognize these different patterns of instability and their associated risk factors, as more complex patterns of instability would require more extensive surgical procedures. Medial patellofemoral ligament (MPFL) reconstruction, by itself, may not suffice or may not be appropriate for the more complex instability patterns. Appropriate and early treatment of such instability in children would allow for functional progression and possible remodeling of the trochlea. However, early treatment has the associated risk of growth disturbances when surgical procedures are performed around open physis or if adult-type bony procedures are performed in children. Recent knowledge about the relationship between trochlea, MPFL femoral attachment, and distal femoral physis could help to advance safe surgical care for these patients. This article reviews the pathophysiology, risk factors, and the existing classification systems for patellar instability in children and adolescents. It focuses on varied surgical techniques, which are unique to the pediatric population, and summarizes the outcomes of these surgical techniques.

Continue to: EPIDEMIOLOGY

EPIDEMIOLOGY

In a prospective 2-year study of Finnish children, the annual incidence rate of patellar instability was 43/100,000 pediatric population.¹ In patients 9 to 15 years of age, the incidence was approximately 1/1000.¹ In another study, patients at highest risk for a first-time patellar dislocation were females aged 10 to 17 years.² In a study in patients with traumatic hemarthrosis, 36% in the younger age group (10-14 years) and 28% in the older age group (15-18 years) had sustained patellar dislocation. In contrast, 22% in the younger age group and 40% in the older age group had sustained an anterior cruciate ligament tear.³

Approximately one-half of patients who dislocate their patella suffer from long-term complications.^4,5 These complications include recurrent instability, patellofemoral pain, osteochondral lesions, and eventual arthritis.^1,4,5 Young, active individuals are more prone to these issues.⁶ Also, 39% or more of patellar dislocation patients have an associated osteochondral fracture that might influence the management.¹ Thus, patellar instability in young patients is an area of concern.

DEVELOPMENTAL ANATOMY

At 4-week gestation, the patellofemoral joint is an ectodermal sac filled with mesenchyme of the somatic mesoderm.⁷ Mesenchymal condensations then appear at 4 to 5 weeks gestation, followed by chondrification of both the femur and patella.⁷ The joint space is present by 6 weeks, and the patellar and distal femoral condyles are present at 7 weeks gestation.⁷ By 8 weeks gestation, the basic knee anatomy resembles that of an adult with the chondroepiphysis forming the articular surfaces of the femur, tibia, and patella.⁷ By this time, the extensor mechanism is formed, and active joint motion has begun, facilitating the development of the trochlear sulcus.⁷ The secondary ossification center in the distal femoral epiphysis forms around 36 weeks gestation.⁸ Postnatally, both the patella and distal femur grow through endochondral ossification.^9,10

The patella is the largest sesamoid bone in the human body.¹¹ The patella begins as a dense consolidation of cells that differentiate as the quadriceps mechanisms develop.^12,13 The patellar anlage becomes distinguishable within the quadriceps tendon around 7.5-week gestation.¹² The morphology of the patella conforms to the distal femur.¹² The patella molds or re-models as the knee begins to move in response to mechanical stresses.⁷ The patella increases in relative size during the first 6 months of gestation, then enlarges proportionately to the rest of the bones.⁷ Ossification begins around 3 years of age for females and 4 to 5 years of age for males.^8,14 The ossification center may appear irregular as it rapidly expands.¹⁴ Ossification proceeds in a proximal to distal direction, thus giving a spurious estimation of patellar height on radiographs in children. The overall morphology of the cartilaginous patella during development is comparable to the final mature shape.¹⁴ Abnormal contact stresses on the articular surface of the patella during skeletal immaturity can lead to deformation.⁷

Ultrasonographic measurements in normal patients show that trochlear groove (TG) morphology is present early and becomes more radiographically apparent as distal femoral ossification is completed.¹⁵ Anatomic dissections of aborted fetuses have verified the morphology of the TG as it remains constant during growth and the groove morphology is the same for both fetuses and adults.¹⁶ An ultrasound study performed on patients aged 12 to 18 years showed the cartilaginous sulcus angle (CSA) remained constant throughout all age groups (146°).¹⁷ The CSA however, differed in patients who suffered a patellar dislocation (average, 164°; range, 154°-195°) compared with normal knees (average CSA, 145°; range, 131°-158°).^15,17,18 The osseous sulcus angle, on the other hand, appears flat at birth and the TG deepens with age. This increase in depth is more of a reflection of progressive ossification of a well-formed cartilaginous trochlea, rather than a true deepening of the sulcus.¹⁷ Thus, the axial radiographic view of the patella provides misleading information about the sulcus angle in children and should not be used to define trochlear morphology.

Continue to: MEDIAL PATELLOFEMORAL LIGAMENT ANATOMY

The medial patellofemoral ligament (MPFL) functions to limit the lateral translation of the patella.¹⁹ The attachment sites on the femur and patella for the MPFL have been studied in children.^20-23 Cadaveric dissections in specimens aged 2 to 11 years have noted the patellar attachment to be an average of 12 mm in length with the midpoint approximately 5 mm superior to the mid-pole of the patella.²² The patellar footprint of the MPFL insertion was a mean 41% of the entire patellar length.²²

It is important to be aware of the characteristic anatomy of the MPFL, as fixation points should mimic the anatomic insertion as best as possible while also avoiding violation of the nearby physis. The MPFL originates between the adductor tubercle and the medial femoral epicondyle just distal to the distal femoral physis and attaches to the superomedial aspect of the patella.^20-25 In relation to the physis in pediatric patients, the midpoint of MPFL insertion has been measured to be 4 mm to 9 mm distal to the femoral physis.^21,24,25 These measurements represent averages as cadaveric studies have reported that some part of MPFL femoral insertion extends proximal to the distal femoral physis.²¹ A recent report of physeal injury to the posterior distal femoral physis during MPFL reconstruction leading to femoral flexion deformity highlights the importance of physeal-respecting surgery.²⁶

TROCHLEA AND ANTERIOR DISTAL FEMORAL PHYSIS

The relationship between the proximal aspect of the trochlea and the anterior distal femoral physis has been recently studied in 175 knees with dysplastic trochlea.²⁷ Based on magnetic resonance imaging evaluation, the lateral aspect of the trochlea extended proximal to the anterior distal femoral physis in 13% of patients and was at the level of the anterior physis in another 13% of patients (Figure 1).²⁷ Hence, a cautious approach is recommended for any surgery to address trochlear dysplasia or trochlear bump in younger patients to prevent iatrogenic injury to anterior distal femoral physis and resultant genu recurvatum. The distance between the trochlea and the physis increased with increasing age.

LIMB ALIGNMENT

Physiologically, the quadriceps angle (Q angle) changes through the course of growth. As children begin standing and walking, they stand with their feet wider apart and in genu varum.²⁸ Physiologic genu varum can reach 15°.²⁸ This degree lessens during the first 1.5 to 2 years of life, transitioning to physiologic valgus of nearly 12° by 3 years of age.²⁸ Genu valgum, thereafter, gradually decreases to reach the adult value of around 7° to 8° by age 7 years.²⁸ Increased genu valgum is a risk factor for patellar instability. In skeletally immature patients, correction of genu valgum through guided growth may be desirable in patients undergoing patellar stabilization surgery (Figures 2A, 2B).²⁹

PATHOPHYSIOLOGY OF PEDIATRIC PATELLAR DISLOCATION

TROCHLEAR DYSPLASIA

Trochlear dysplasia is an abnormal shape and depth of the TG.³⁰ Up to 96% of patients with patellar dislocation have trochlear dysplasia.^30-33 In a study of patellar instability in children, at least 1 of the 3 signs of trochlear dysplasia (the crossing sign, supratrochlear bump, and double contour sign) was present on lateral radiographs.³⁴ In another study on the growth of trochlear dysplasia in children and adolescents, all grades of trochlear dysplasia were present at all ages (ie, the dysplasia was most likely present at birth and did not necessarily worsen with age and growth).³⁵ The linear dimensions of lateral and medial condylar height as well as trochlear bump increased with age but both the sulcus angle and shape of the trochlea did not change significantly.³⁵ Remodeling of a dysplastic trochlea can happen if the patella is stabilized and appropriately located at a younger age, preferably before 10 years of age.^36,37

Continue to: PATELLAR HEIGHT

The role of patellar height in patellar instability has been well established.³⁸ In patients with patella alta, the patella remains proximal to the TG during the greater arc of knee motion, which predisposes it to patellar instability. Calculation of patellar height in children could be challenging due to incomplete ossification, as well as asymmetric ossification of the patella and the tibial tubercle (TT). Since the patella ossifies from proximal to distal, most radiographic methods that measure the patellar height from the distal aspect of the patella provide a spurious elevation of the measurement.

The Caton-Deschamps (CD) method measures the length of the patellar articular surface and the distance from the inferior edge of the articular surface to the anterosuperior corner of the tibial plateau.³⁹ A ratio >1.3 signifies patella alta. The CD ratio has been verified as a simple and reliable index for measuring patellar height in children.⁴⁰ Two other methods have been described for determining patellar height in children.^41,42 Based on anteroposterior (AP) radiographs of the knee in full extension, Micheli and colleagues⁴¹ calculated the difference between the distance from the superior pole of the patella to the tibial plateau and the length of the patella. A positive difference signified patella alta. The Koshino method involves the ratio between a reference line from the midpoint of the patella to the midpoint of the proximal tibial physis and a second distance from the midpoint of the distal femoral physis to the midpoint of the proximal tibial physis on lateral knee radiographs.⁴² Normal values range from 0.99 to 1.20 with the knee in >30° flexion, in children 3 to 18 years of age.

HYPERLAXITY

In contrast to adults, children have increased levels of collagen III compared with collagen I, which is responsible for tissue elasticity.⁴³ Tissue elasticity leads to increased joint mobility, which is more common in children. Joint hypermobility or hyperlaxity has to be differentiated from symptomatic instability. The traditional Beighton score identifies individuals as having joint hypermobility with a score of 5/9 or higher in school-aged children.^44-46 Smits-Engelsman and colleagues⁴⁴ suggested using stricter criteria with scores of 7/9 or higher being indicative of hyperlaxity in school-aged children. A study of 1845 Swedish school children noted that females have a higher degree of joint laxity.⁴⁵ Maximal laxity was noted in females at 15 years of age.⁴⁵ Hyperlaxity has been demonstrated to be greater on the left side of the body⁴⁴ and can be part of generalized syndromes including Down’s syndrome, Marfan’s syndrome, or Ehlers-Danlos syndrome.

LIMB TORSION

Staheli and colleagues⁴⁷ described the normative values of a lower extremity rotational profile, including femoral anteversion and tibial torsion. Children normally have increased femoral anteversion, which decreases with growth. Miserable malalignment is a term used to denote increased femoral anteversion and increased external tibial torsion.^48,49 These rotational abnormalities can increase the Q angle and the lateral forces on the patella. Femoral anteversion or internal rotation of the femur of 30° significantly increases strain in all areas of the MPFL.⁴⁸ This increased strain may lead to MPFL failure and patellar instability.⁴⁸ Increased internal rotation of the femur also increases contact pressure on the lateral aspect of the patellofemoral joint.⁴⁸ Miserable malalignment frequently manifests following a pubertal growth spurt and may require femoral and tibial osteotomy.⁵⁰

SYNDROMIC ASSOCIATIONS

Several syndromes have patellar instability as a part of their manifestation. The more common syndromes include nail-patella syndrome, Kabuki syndrome, Down’s syndrome, and Rubinstein-Taybi syndrome.^51-54 Other syndromes less commonly associated with patellar instability include Turner syndrome, patella aplasia, or absent patella syndrome. Since many patients with syndromic patellar instability are functionally limited, they may not require an aggressive approach to treatment. When treating these patients, it is important to recognize the unique features of a specific syndrome, which may affect the anesthesia risk profile, management decisions, rehabilitation, and prognosis.

Continue to: MPFL TEAR PATTERN

The MPFL serves as an important constraint to the patella to prevent lateral dislocation, primarily during the first 20° to 30° of knee flexion.^55,56 Injury to the MPFL is noted in over 90% of patients who suffer a patellar dislocation.⁵⁷ The location of MPFL tears in pediatric patients is variably reported at the patellar attachment (10%-61%), femoral attachment (12%-73%), both (12%-35%) or mid-substance (2.5%-15%).^25,57 The most common tear patterns in pediatric patients are tears at the patellar attachment.^25,57 This tear pattern may be accompanied by an avulsion fracture of the medial rim of the patella, though this fracture, being extra-articular, seldom needs treatment.

CLASSIFICATION

While several authors have established extensive classification systems of patellar dislocation based on both clinical and radiographic presentation and reviews of the literature, a single classification system has not been recognized as the gold standard. In this section, in addition to presenting our preferred methods of classification, we will review some of the more recent and extensive classification systems for patellar dislocation and patellar instability.

Dejour and colleagues³¹ initially used both the presence of patellofemoral anatomic abnormalities and pain to define 3 types of patellar instability: major, objective, and potential patellar instability. Major patellar instability indicates that the patient has experienced more than 1 documented dislocation, objective instability involves one dislocation in addition to an associated anatomic abnormality, and potential patellar instability refers to cases in which the patient has radiographic abnormalities and patellar pain.³¹ Garin and colleagues⁵⁸ more simplistically divided patellar dislocation patients into 2 groups: major (permanent or habitual) dislocation of the patella and recurrent dislocation. Sillanpaa⁵⁹ stressed the distinction between first-time dislocation and recurrent dislocation specifically in the context of acute injuries. These classification systems were formulated with adults as the most relevant population; however, classifications targeted specifically to pediatric patients have recently been presented in the literature.

Historically, pediatric patella dislocations were simply categorized as traumatic or congenital.⁶⁰ In 2014, Chotel and colleagues⁶¹ focused on classifying patellar dislocation by extensively reviewing anatomic, biomechanical, pathophysiological, and clinical patterns seen most commonly in children. They included 5 categories: congenital dislocation, permanent dislocation, habitual dislocation during knee flexion, habitual dislocation during knee extension, and recurrent dislocation; however, they did not address traumatic dislocations.⁶¹ Congenital dislocation is a rare condition, typically presenting at birth, which produces a pattern of functional genu valgum.⁶² Permanent dislocation typically presents after the child has started walking, but before the age of 5 years.⁶¹ The 2 variations of habitual dislocation typically present between ages 5 and 8 years.⁶¹ The final category is the most common and typically occurs during pre-adolescence or adolescence as a result of an atraumatic or trivial traumatic event or sports injury.¹ Using more specific terminology, Hiemstra and colleagues⁶³ modeled a classification system based on the traumatic, unilateral, bankart lesion, surgery (TUBS)/atraumatic, multidirectional, bilateral, rehabilitation, inferior shift (AMBRI) for shoulder dislocation classifications. The patellar dislocation system is used to identify 2 distinct subsets of patients in the patellofemoral instability population. One subset is defined by the acronym WARPS (weak, atraumatic, risky anatomy, pain, and subluxation), the other is STAID (strong, traumatic, anatomy normal, instability, and dislocation).⁶⁴ Patients categorized by the WARPS acronym tend to experience atraumatic onsets of patellofemoral instability and demonstrate anatomic issues that increase this instability. These underlying anatomic issues include valgus alignment, ligamentous laxity, rotational abnormalities, shallow and short TG, and patella alta. On the other hand, STAID patients describe a traumatic dislocation event and do not have underlying anatomic abnormalities that predispose them to instability.⁶⁴

Taking into account these previous classifications, Frosch and colleagues⁶⁵ added specific pathologies including “instability,” “maltracking,” and “loss of patellar tracking,” in addition to both clinical and radiographic factors to define 5 types of patellar dislocation and their specific treatment recommendations.⁶⁵ Type 1 involves simple dislocation with neither maltracking nor instability and a low risk of redislocation.⁶⁵ Type 2 is defined as primary dislocation followed by subsequent high risk of dislocation and no maltracking.⁶⁵ Type 3 is divided into 5 subcategories of instability and maltracking issues involving soft tissue contracture, patella alta, pathological tibial tuberosity, and TG distance.⁶⁵ Type 4 is defined as the highly unstable “floating patella,” and type 5 involves patellar maltracking without instability ⁶⁵. In terms of treatment, conservative rehabilitation is recommended for type 1 whereas MPFL reconstruction tends to show positive outcomes for both types 2 and 3.^66-70

Continue to: Parikh and Lykissas recently published...

Parikh and Lykissas recently published a comprehensive classification system of 4 defined types of patellar dislocation in addition to voluntary patellar instability and syndromic patellar instability (Table).⁶⁰ The 4 types are Type 1, first-time patellar dislocation; Type 2, recurrent patellar instability; Type 3, dislocatable; and Type 4, dislocated. Type 2 is further subdivided into Type 2A, which presents with positive apprehension signs, and Type 2B, which involves instabilities related to anatomic abnormalities.⁶⁰ A distinction is also made between Type 3A or passive patellar dislocation and Type 3B habitual patellar dislocation.⁶⁰

The classification system proposed by Green and colleagues is more simplified with 3 main categories (Table) of pediatric patellar dislocation: traumatic (acute or recurrent), obligatory (either in flexion or extension), and fixed laterally.^71,72 The acute traumatic categorization refers to patients who experienced an initial dislocation event due to trauma whereas recurrent traumatic involves repeated patella dislocations following an initial incident. Studies report that between 60% to 70% of these acute traumatic dislocations occur as a result of a sports-related incident.^2,33,73 Obligatory dislocations occur with every episode of either knee flexion or extension, depending on the subtype. Obligatory patella dislocation in flexion typically cannot be manipulated or relocated into the trochlea while the knee is fixed but does reduce into the trochlea in full extension. Fixed lateral dislocations are rare, irreducible dislocations in which the patella stays dislocated laterally in flexion and extension. These dislocations often present with other congenital abnormalities. Each of these categories can be further specified as syndromic if the dislocation is associated with genetic or congenital conditions including skeletal dysplasia, Ehlers-Danlos syndrome, cerebral palsy, Marfan disease, nail-patella syndrome, Down syndrome, Rubenstein-Taybi syndrome, and Kabuki syndrome.^{51-54,61,74-76}

SURGICAL TECHNIQUES IN SKELETALLY IMMATURE PATIENTS

While nonsurgical, conservative treatment involving physical therapy and activity modification is recommended for most patients who experience first-time traumatic patellar dislocations, many patients experience complicating factors that indicate them for surgery. These factors include recurrent dislocation, risk factors for patellofemoral instability, underlying malalignment issues, and congenital deformities. When evaluating these factors, particularly patellofemoral instability, the authors recommend assessing osteochondral lesions, age, skeletal maturity, number of previous dislocations, family history, and anatomic risk factors.^2,5,77-79 Extra care should be taken when considering surgical treatment for skeletally immature patients at elevated risk for recurrent instability as the risk of cartilage damage in these cases is high.^80-82

Recently, there has been a reported increase in surgical treatment for patellar instability in the skeletally immature.⁸³ This finding may be attributed to heightened awareness of factors that indicate patients for surgical treatment and increased familiarity of surgeons with newer techniques.⁸³ Many surgical techniques have been described to address patellar instability involving both soft-tissue procedures and bony corrections.⁸⁴ In this article, we discuss the various surgical techniques for MPFL reconstruction, quadricepsplasty, and distal realignment. These procedures can be paired with any number of additional procedures including, but not limited to, lateral retinacular release or lengthening, chondroplasty, TT osteotomy (in skeletally mature patients), and removal of loose bodies.⁸³

There is a need for more comprehensive studies, particularly randomized controlled trials, to evaluate the outcomes for both surgical and nonsurgical treatments for first-time dislocations. In the current literature, only very recently have surgical treatments shown outcomes that are more positive. In 2009, Nietosvaara and colleagues⁸⁵ conducted a randomized controlled trial of nonoperative and operative treatment of primary acute patellar dislocation in both children and adolescents. After a long-term mean follow-up of 14 years, there was not a significant difference between the groups in recurrent dislocation and instability, subjective outcome, or activity scores.⁸⁵ In a subsequent review of 5 studies including 339 knees, Hing and colleagues⁸⁶ also found similar results in both the operative and nonoperative cohorts at risk of recurrent dislocations, Kujala scores, and reoperations. However, a recent systematic review comparing redislocation rates and clinical outcomes between surgical and conservative management of acute patellar dislocation reported more positive outcomes for the surgical cohort.⁸⁷ This review included 627 knees, 470 of which received conservative management, 157 of which received operative treatment. The conservative cohort was followed for an average of 3.9 years and had a 31% rate of recurrent dislocation while the surgical group was followed for a mean 4.7 years and experienced a 22% redislocation rate.⁸⁷ This study indicates that operative management for acute first-time dislocations may be the preferred treatment option.

Continue to: A potential reason some of these studies...

A potential reason some of these studies did not show any significant difference between the operative and nonoperative cohort could be that the surgical cohorts included a wide range of procedures including lateral releases and MPFL repairs. Recent publications have indicated that these techniques do not produce overall positive outcomes. While each surgical treatment plan is unique depending on the patient; recently, MPFL reconstruction has been shown to have better outcomes than both nonoperative management and simple medial repair and/or lateral
release.^67,88-90

MPFL RECONSTRUCTION

INDICATIONS/OVERVIEW

The MPFL is an important stabilizer for the knee that primarily resists lateral translation of the patella. Damage to the MPFL is very common in acute patellar dislocations with up to 90% of first-time dislocations resulting in injury to the MPFL.^91,92 Historically, simple medial and/or lateral MPFL repairs have not been shown to improve patellofemoral kinematics significantly and often result in recurrence.^90,93 To address this issue, during the past few decades, numerous MPFL reconstruction techniques have been developed to reconstruct a stronger ligament with the same kinematics as the anatomic MPFL.^{2,19,69,81,94-106} The ultimate goal of MPFL reconstruction is to reestablish the anatomic “checkrein” to guide the patella into the trochlea between 0° and 30° of knee flexion.^107,108 An essential secondary surgical goal in skeletally immature patients is to avoid damaging the distal femoral physis.

There are many variations in both the grafts used to replace the MPFL and the means by which to secure them. The ones discussed below include free semitendinosus or gracilis autografts or grafts constructed from a pedicled adductor, patellar, or quadriceps tendon.^69,105,109 While not used as frequently, allografts have also been used.¹¹⁰ Methods to secure these grafts in osseous tunnels include suture anchors or tenodesis screws. Incomplete osseous sockets or medial-sided bone tunnels have also been used as a method to decrease patellar fractures as they preserve the lateral patellar cortex.^111-114

DOUBLE-BUNDLE HAMSTRING AUTOGRAFT

The technique most often used by the author is a double-bundle hamstring autograft harvested from either the semitendinosus or the gracilis secured by short patellar and femoral sockets (Figure 3). After harvesting the hamstring graft from a posteromedial incision, an approximately 90-mm graft is prepared with Krackow stitches to secure 15 mm of the tendon in each socket.¹¹⁵ Lateral radiographs are used intraoperatively to ensure the guidewire for the femoral drill hole falls along the posterior cortex of the diaphysis of the femur while AP radiographs confirm placement distal to the physis. It is important to take both AP and lateral radiographs intraoperatively due to the concave curvature of the distal femoral physis. This unique anatomy can make a point that is located distally to the physis on the AP view appear on or proximal to it on the lateral cross reference view.^24,116 For the patellar socket, 2 short sockets are made in the superior half of the patella. Once the sockets have been drilled, the graft is adjusted so that the patella stays seated in the center of the trochlea between 20° and 30° of flexion. This anchoring is accomplished by securing the graft while the knee is kept at 30° of flexion. Proper tension is confirmed by ensuring that the graft does not allow lateral patella movement over one-fourth the width of the patella in extension while crepitation must not appear throughout the ROM.⁹²

QUADRICPETS TENDON TRANSFER

A combination of techniques by Steensen and colleagues,¹⁰⁵ Goyal,¹⁰⁹ Noyes and Albright,¹¹⁷ and Pinkowsky and Hennrikus¹¹⁸ describe an MPFL reconstruction in which the proximal end of a small medial portion of the quadriceps tendon is released and then attached to the medial epicondyle through a subcutaneous tunnel (Figure 4). This technique is particularly useful for cases in which the extra strength provided by the bone-quadriceps tendon is necessary to correct more severe dysplasia. Leaving the distal end of the quadriceps tendon intact at its patellar insertion, a graft of about 8 mm x 70 mm thickness is harvested from the tendon. The free distal end of the tendon is then run anatomically through the synovium and retinaculum to be either sutured to the medial intermuscular septum at the medial femoral epicondyle or fixed in femoral tunnel using interference screw.^105,109,118 The placement of the femoral fixation point is essential to ensure positive surgical outcomes. If the graft is secured too anteriorly, it may be too loose in extension and too tight in flexion, both of which can lead to postoperative pain, loss of normal kinematics, and overload of the medial patellofemoral cartilage.^119-121 Once the ideal placement of the femoral fixation point has been confirmed by intraoperative radiographs, the graft is secured with a small absorbable suture.^122,123 While this technique has good clinical results, the longitudinal scar that results from graft harvesting is cosmetically unappealing, and it is technically challenging to harvest a consistent strip of the quadriceps tendon. To address some of these concerns, Fink and colleagues¹²⁴ described a new harvesting technique that produces more consistent grafts and requires a smaller incision.

Continue to: ADDUCTOR MAGNUS TENDON TRANSFER

This technique is a double-bundle MPFL reconstruction that uses a pedicled graft of the distal adductor magnus tendon and suture anchors or incomplete osseous sockets to recreate the MPFL anatomically (Figure 5). Avikainen and colleagues⁹⁶ and Sillanpää and colleagues¹²⁵ described this procedure as a progression from the original single-strand adductor magnus transfer technique. First, maintaining the distal insertion, a graft of approximately 14 cm to 18 cm is harvested from the adductor tendon and then passed through a subcutaneous tunnel between the distal vastus medialis obliquus and the superficial joint capsule. The graft is then looped at the medial patella so that the distal bundle runs back to the adductor tubercle.¹²⁵ With the knee at 30° of flexion to assure proper tension, the graft is secured at both the patella and near the adductor tubercle with suture anchors.¹²⁵ Hambridge and colleagues¹²⁶ compared a similar adductor magnus transfer with other pedicled techniques including bone-quadriceps tendon autograft and bone-patellar tendon allograft and found positive results for all 3 methods of reconstruction.

HEMI-PATELLA TENDON TRANSFER

In a similar technique to the adductor tendon transfer, the medial section of the patellar tendon is harvested from the TT and run from its proximal insertion at the medial patella to the medial femoral attachment via a subcutaneous tunnel. The free end of the graft is then secured with suture anchors or incomplete osseous sockets with the knee at 30° of flexion.¹²⁷

HAMSTRING GRAFT WITH ADDUCTOR TENDON AS A PULLEY

Several techniques opt to use a more dynamic model of MPFL reconstruction in which the adductor tendon or medial collateral ligament (MCL) is used as a pulley for the hamstring graft (Figure 6).^128,129 The site of the pulley approximates the normal attachment of the MPFL to the femur and so acts as an effective anatomic replica of the MPFL origin. A semitendinosus graft is harvested and is prepared with continuous sutures, and 2 tunnels to secure the graft are drilled into the patella. The graft is then run subcutaneously from the medial side of the patella to the adductor magnus tubercle into which an osteoperiosteal tunnel is drilled at its distal femoral insertion. The graft is looped through the adductor tunnel and secured with sutures. Proper knee kinematics was ensured by placing the knee at 30° of flexion as the ends of the tendon are secured to the patella.^114,130

HAMSTRING GRAFT WITH MCL AS A PULLEY

The MCL can also be used as a pulley rather than the adductor tendon. The semitendinosus graft is harvested and prepared and the patella drilled as it is in the previous technique. The MCL was fashioned into a pulley by making a slit in its posterior one-third. The semitendinosus graft is looped through this slit, and both ends of the graft are held in place with suture anchors on the surface of the patella.¹²⁹

ADDITIONAL PROCEDURAL COMBINATIONS

Depending on the needs of the individual patient, MPFL reconstruction, and other patellar stabilization techniques can also be combined with additional procedures. Arshi and colleagues⁸³ conducted a review of 6190 adolescents surgically treated for patellar instability and reported the most common additional procedures performed at the time of the stabilization. They found 43.7% of the population underwent lateral retinacular release, which while not effective as an isolated technique to treat patellar instability, has often been used in combination with MPFL reconstruction.^131-133 There is currently a lack of consensus regarding the success of adding a lateral release to the reconstruction. Some studies report no difference while others report a decrease in stability after lateral release.^90,134-136 While lateral retinacular release has been shown to decrease the force required to displace the patella, it can be surgically indicated in certain patients undergoing MPFL reconstruction.¹³¹ The authors advocate that if the lateral retinaculum is tight such that centralized patellar tracking is inhibited following the reconstruction, or if the patella cannot be pushed passively from a laterally tilted position to the neutral horizontal position, lateral retinacular lengthening should be performed to improve kinematics.¹³²

Continue to: Arshi and colleagues...

Arshi and colleagues⁸³ also reported a high rate of cartilage procedures, with chondroplasty performed in 31.1% and chondral fragment/loose body removal in 10.2%. These statistics suggest that a significant level of cartilage damage has occurred by the time of surgery.⁸³

COMPLICATIONS

As MPFL reconstruction techniques have only recently been popularized and developed, there are not many comprehensive studies evaluating the outcomes and complications associated with these procedures. However, in the current literature, there is a general consensus that patients usually experience positive short-term clinical outcomes and relatively low complication rates.^68,77 In one of the largest retrospective cohort studies of pediatric patients undergoing MPFL reconstruction, Parikh and colleagues¹¹⁴ reported both the type and rate of complications. They found complications occurred in 16.2% of patients, and the most common complications were recurrent patellar instability, patellar fractures, patellofemoral arthrosis, motion deficits, and stiffness with over half classified as avoidable. Most of these complications were due to technical errors with episodes of recurrent instability only reported in 4.5% of patients.¹¹⁴ In a comprehensive meta-analysis of MPFL reconstruction studies, Shah and colleagues¹³⁷ reported a complication rate of 26% in both pediatric and adult patients. The cohort was not stratified by age, yet complications were similar to those reported by Parikh and colleagues,¹¹⁴ including pain, loss of knee flexion, wound complications, and patellar fracture.¹³⁷

As indicated by the frequency of technical complications reported by Parikh and colleagues,¹¹⁴ extra caution should be taken in the operating room to minimize potential errors. In techniques that require drilling of femoral sockets, proper length for and placement of the graft is essential to reestablish proper kinematics. Studies have reported that placing the femoral socket too proximally can result in loss of ROM during flexion and increased compressive forces across the patella.¹³⁸ A graft that is too short can have similar negative outcomes, and a graft that is too long can result in recurrent instability. Positioning the graft while the knee is in 30° of flexion can help ensure the proper length and tension is achieved. Once the graft is in place, it is important to ensure the ROM and isometry before completing the fixation.⁷² It is also essential to be vigilant about potential violation of the physes and subsequent growth disturbances. To establish the safest angles for drilling the distal femoral epiphysis for graft placement, Nguyen and colleagues¹³⁹ conducted a study using high-resolution 3-dimensional images of cadaveric distal femoral epiphyses. By recording which tunnels disrupted the physis before reaching 20 mm of depth, the authors concluded that it is safest to drill distally and anteriorly at an angle between 15° and 20°.¹³⁹ This technique should minimize damage to the physis, notch, and distal femoral cartilage and decrease potential complications.¹³⁹

OUTCOMES

In general, the literature reports positive outcomes for MPFL reconstruction—in both studies that address a specific technique and all-encompassing studies. Outcomes are typically reported as Kujala and Tegner scores, results from clinical examinations, and rates of subsequence recurrences. Several recent studies have also evaluated the ability of MPFL reconstruction to restore proper kinematics. Edmonds and colleagues¹⁴⁰ evaluated the difference in patellofemoral joint reaction forces and load experienced by 3 groups of adolescents: a cohort treated with MPFL reconstruction, a cohort treated with soft-tissue realignment of the extensor mechanism (the Insall method), and controls. While both surgical techniques were able to restore medial constraints to the patella, the study showed that only the MPFL reconstruction cohort experienced joint reaction forces that were analogous to the control group. In comparison, the cohort that was treated with soft-tissue realignment alone experienced higher patellofemoral joint reaction forces and did not regain normal joint mechanics.¹⁴⁰ These results can be used to advocate for the further use of MPFL reconstruction as an effective anatomic replacement of the native ligament. Radiographic studies have similarly reported MPFL reconstruction as an effective means to restore anatomic normality. Fabricant and colleagues¹⁴¹ conducted a radiographic study in which patella alta was corrected to normal childhood ranges in patients who underwent MPFL reconstruction technique using a hamstring autograft. Lykissas and colleagues¹⁴² corroborated these results with another radiographic study that reported small but significant decreases in the Blackburne-Peel index and CD index following MPFL reconstruction in 25 adolescents. As correction of patella alta allows the patella to rest in a deeper, more secure position in the TG, these results indicate that effective early MPFL reconstruction can correct for patellar anatomic abnormalities that could be future risk factors.^143,144 Several studies have also reported outcomes addressing specific MPFL techniques; these are reported and discussed in this article.

OUTCOMES BY TECHNIQUE

HAMSTRING AUTOGRAFT

Reports on outcomes following MPFL reconstructions using hamstring autografts have been particularly promising. A cohort of 21 skeletally immature patients who underwent MPFL reconstruction was evaluated pre- and postoperatively with an average of a 2.8-year follow-up. The authors of the study reported no redislocation events and significant improvement in the Kujala scores, and patients were able to return to athletic activities safely.¹⁴⁵ Previous studies report similar positive increases in Kujala scores, subjective patient reports, and lack of subsequent redislocation for patients who underwent either semitendinosus or gracilis autograft MPFL reconstructions. One such study further documented an average patellar inclination angle decrease from 34.3° to 18.6° following MPFL reconstruction.¹⁴⁶ However, while the literature typically reports positive Kujala scores and subjective outcomes for the hamstring autograft procedure, a study arthroscopically evaluating patellar tracking immediately following surgery and then at 6 to 26 months follow-up found that patellar tracking correction was not maintained for all patients who underwent this type of MPFL reconstruction.¹⁴⁷

Continue to: QUADRICEPS TENDON TRANSFER OUTCOMES

Studies specifically evaluating the quadriceps tendon transfer technique for MPFL reconstruction in children are sparse, but authors have reported positive clinical outcomes and low complication rates in adults. After following 32 young adults who underwent this MPFL reconstruction technique for 3 years, Goyal¹⁰⁹ reported a significant increase in mean Kujala scores from 49.31 to 91.25 and no complications or redislocation. He argues this type of quadriceps graft has a high success rate because it is anatomically more similar to the MPFL than other grafts and does not require additional patellar fixation.^101,109 Similar positive Kujala scores and minimal complications have been reported in adult patient populations.¹⁴⁸ Abouelsoud and colleagues¹⁴⁹ conducted one of the few studies in skeletally immature patients and reported similarly positive results with no redislocations and significantly improved Kujala scores at a mean follow-up of 29.25 months in their 16-patient cohorts.

ADDUCTOR MAGNUS TENDON TRANSFER

After initially describing this technique in 14 adult patients, Avikainen and colleagues⁹⁶ followed this cohort and reported positive subjective results and only 1 redislocation. In a more recent study in which the adductor tendon transfer technique was compared with the quadriceps tendon transfer described above and the bone-patellar tendon allograft, Steiner and colleagues⁶⁹ reported similarly significant improvement in all cohorts in Lysholm, Kujala, and Tegner scores with no redislocations. Additionally, Malecki and colleagues¹⁵⁰ followed a cohort of 33 children with 39 knees diagnosed with recurrent patellar dislocation, who underwent MPFL reconstruction using the adductor magnus tendon. After evaluating this cohort functionally and radiographically, the authors reported improvements in Lysholm and Kujala scores, patellar tilt and congruence angles, and peak torque of the quadriceps muscle and flexor.¹⁵⁰ However, this cohort did report postoperative redislocations in 36.4% of patients (4 of 11).¹⁵⁰

HEMI-PATELLA TENDON TRANSFER

In 2012, in the first randomized controlled trial, Bitar and colleagues⁶⁷ compared the outcomes of patients who underwent MPFL reconstruction via the hemi-patellar tendon technique with those who were managed nonoperatively with immobilization and physiotherapy after first-time patellar dislocation. At 2-year follow-up, the surgical cohort presented positive results with a significantly higher mean Kujala score (88.9 to 70.8) and no redislocations or subluxations. In contrast, 35% of nonoperative cases presented with recurrences and subluxations over the 2-year period.⁶⁷

MCL OR ADDUCTOR TENDON AS A PULLEY

Studies have reported good postoperative results and low complication rates for these dynamic techniques.^128,129 In terms of kinematics, while hypermobility and patellar height were not fully corrected, improvements in patellar tilt and lateral shift were reported in a cohort of 6 patients with a minimum 4-year follow-up.¹²⁹ To further evaluate whether the more dynamic pulley reconstruction technique resulted in better outcomes, Gomes and colleagues¹²⁸ compared the subjective reports, clinical evaluations, and complication rates of patients who underwent MPFL reconstruction with a rigid adductor magnus fixation vs a semitendinosus tendon dynamic femoral fixation. One case in the rigid cohort experienced a subsequent subluxation, while patients in the semitendinosus group had better subjective reports and a higher rate of return to sport.¹²⁸ More recently, Kumahashi and colleagues¹⁵¹ specifically studied the outcomes of the MCL tendon as a pulley in 5 patients aged 14 to 15 years. They reported similar successful results as no patients experienced recurrence, and all patients exhibited improvement in radiographic measures of patellar tilt and congruence angle, lateral shift ratio, and both Kujala and Lysholm scores.¹⁵¹

While there has yet to be a randomized controlled trial comparing all of these different techniques, there is a general consensus in the literature that patients tend to perform better following MPFL reconstruction vs MPFL repair.

OTHER STABILIZATION PROCEDURES, INCLUDING DISTAL REALIGNMENT

Patients with additional underlying deficits and malalignment issues such as significant trochlear dysplasia, increased TT-TG distance, patella alta, increased Q angle, and/or positive J sign may require stabilization procedures beyond MPFL reconstruction.^152,153 TT osteotomies are often used to correct alignment issues in the adult patient population; however, these procedures are typically contraindicated in skeletally immature patients. Alternative realignment procedures for the pediatric population include both proximal and distal realignment, with proximal realignment performed primarily in children under the age of 12 years.¹⁵³ Many variations on these procedures exist, some of which are no longer regularly performed due to poor reported outcomes. In this article, we discuss several of the techniques, focusing primarily on those that have demonstrated higher success rates.

Continue to: GALEAZZI TECHNIQUE

One of the first and most famous soft-tissue techniques to address patellar instability was the semitendinosus tenodesis, published by Galeazzi¹⁵⁴ in 1922 (Figure 7). This technique stabilizes the patella without altering the TT. In the original technique, a portion of the semitendinosus tendon is harvested with its tibial insertion left intact. The free end of the tendon is then secured with sutures at the periosteal groove of the medial patella.^154,155 Fiume¹⁵⁶ modified this technique by adding a lateral release and medial retinacular reefing. The most recent addition to this procedure was introduced by Baker and colleagues,¹⁵⁷ in which a tunnel is drilled from the medial to the lateral border of the patella. Tension placed on the grafted tendon is used to reposition the patella medially and draw it downward. Preliminary literature on this modified procedure reported fair clinical results with success rates of approximately 75%.^155,158-160 A recent study evaluating both the clinical and radiographic outcomes of this technique also indicated that while clinical results were excellent in 62.5% of patients, this technique alone was unsuccessful in fully addressing patellar instability in patients with underlying anatomic abnormalities such as patellar alta.¹⁶¹ In light of these less than ideal reports, the authors no longer recommend this technique for patellofemoral instability cases.

ROUX-GOLDTHWAIT PROCEDURE

The Roux-Goldthwait procedure, first described by both Roux¹⁶² and Goldthwait¹⁶³ in 1888 and 1895 respectively, was later modified in 1985 to involve a lateral release, plication of the medial retinaculum, medial transfer of the lateral patellar tendon without advancement, and advancement of the vastus medialis (Figure 8).¹⁶⁴ More recently, Marsh and colleagues¹⁵² introduced an addition to aligning the extensor mechanism with the femoral shaft better. In this technique modification, the patellar tendon is split longitudinally, and its lateral half is detached and transferred distally beneath its medial half. The free end is then sutured to the periosteum on the medial side of the tibia.¹⁵² With a mean long-term follow-up of 6.2 years, Marsh and colleagues¹⁵² reported excellent results in 65%, good in 11%, and fair in 3% of the knees operated on with this modified technique. Of the patients in this cohort whose strength was evaluated, 80% had their strength returned to 90% of preoperative levels in the operated leg.¹⁵² While this study and others report improved outcomes, an increasing body of literature has found high rates of recurrence, patella infera, and other complications following the modified Roux-Goldthwait procedure.^36,165-171 Also, a study comparing MPFL reconstruction using adductus magnus transfer with the Roux-Goldthwait procedure reported that patients in the MPFL cohort reported less pain postoperatively.¹⁵⁰ In addition, whereas the Kujala and Lysholm scores, recurrence rates, patellofemoral angles, and apprehension test results did not demonstrate significant differences between these 2 groups, the MPFL group had significantly fewer abnormal congruence angles, better patellar medialization, and higher peak torque of the hamstring.¹⁵⁰

COMBINED MPFL AND MEDIAL PATELLOTIBIAL LIGAMENT RECONSTRUCTION

While the medial patellotibial ligament (MPTL) has not received much attention with regard to patellar stability, recent studies have indicated its role during higher degrees of both flexion and extension.¹⁷² The MPTL acts as a secondary restrictor ligament which helps release stress on the MPFL by decreasing the Q angle and further normalizing patellar kinematics.¹⁷³ Patients who present with hyperlaxity or knee hyperextension combined with extension subluxation and flexion instability could be indicated for this additional stabilizing procedure. Both Nietosvaara and colleagues⁸⁵ and Brown and Ahmad¹⁷⁴ have described a dual MPTL and MPFL reconstruction technique using a semitendinosus hamstring graft. More recently Hinckel and colleagues¹⁷² described a combined MPFL and MPTL reconstruction, using a graft from the quadriceps tendon to reconstruct the MPFL and one from the patellar tendon to reconstruct the MPTL. In this technique, once the respective grafts have been harvested, a femoral insertion for the graft recreating the MPFL is fluoroscopically established so that an anchor can be inserted distal to the femoral physeal growth plate. For the MPTL insertion, attachment to the tibia below the joint line and 2 cm medial to the patellar tendon is established fluoroscopically just above the physeal growth plate on the proximal epiphysis.^19,175 The MPTL graft is sutured first with the knee at 90° of flexion to establish tension similar to that of the patellar tendon.¹⁷⁶ Then, the knee is placed in 30° of flexion to fix the MPFL graft to the medial patella to prevent excessive lateral translation of the patella.

PATELLAR TENDON TRANSFER

Patellar tendon transfer with proximal realignment is a technique used in particularly young patients to address cases of patellofemoral instability involving concomitant bony or anatomic abnormalities. This procedure is effective for young children with substantial amounts of remaining growth as it better mimics native anatomy than other realignment procedures and does not require bony remodeling.^152-154 It is important to familiarize with surgical techniques to address malalignment issues in young patients as neglected alignment issues can lead to worsening of trochlear dysplasia and instability, which are very difficult to treat later on when patients are older.¹⁵³

The patellar tendon transfer technique (Figure 9), as described by Gordon and Schoenecker,¹⁷⁷ starts with an extensive lateral retinacular release. The patellar tendon is then released from its distal insertion at the TT so that it can be moved medially without moving it inferiorly. After confirming patellar tracking and alignment by flexing the knee from 0° to 90° with the graft in place, the patellar tendon graft is secured with multiple nonabsorbable horizontal sutures.¹⁷⁷ Of note, in skeletally mature patients, a TT osteotomy is used to accomplish the same goal. This osteotomy has been shown to improve both patellar height and TT-TG distance in skeletally mature patients, but is contraindicated in skeletally immature patients.^92,178

Continue to: Initial studies conducted on patellar tendon...

Initial studies conducted on patellar tendon transfer have positive outcomes.¹⁷⁹ At a mean follow-up of 5.1 years, patients reported a decrease in pain and increased the ROM and activity, and only 1 reported a postoperative redislocation.¹⁷⁹ In more recent studies, both Benoit and colleagues³⁶ and Garin and colleagues⁵⁸ reviewed cases of patellar instability treated with patellar tendon transfer to address concomitant patellar alignment and anatomic abnormalities. They reported good functional, clinical, and radiographic outcomes with 12.5% and 16% recurrence rates, respectively.^36,58 They also noted radiographic improvements in femoral sulcus angle, particularly in younger patients, which indicate this procedure is effective in addressing bony abnormalities that can result from neglected malalignment issues.^36,58,154

QUADRICEPSPLASTY

Quadricepsplasty is a lengthening and remodeling technique not frequently used in the pediatric population. The goal of this procedure in patients with significant amounts of growth remaining is to reposition the patella to ameliorate trochlear remodeling and prevent worsening symptoms and anatomic abnormalities.³⁶ A quadricepsplasty accomplishes this by de-rotating and/or lengthening the extensor mechanism and may or may not involve a concomitant MPFL reconstruction. This procedure is particularly effective in young patients who experience obligatory dislocation.^60,72 Several quadricepsplasty techniques have been described including Thompson, Curtis and Fisher, Judet, Stanisavljevic, and V-Y technique.^180-186 Most techniques initially involve sharp dissection of the vastus medialis and lateralis from the rectus femoral tendon. A tongue is then fashioned out of the rectus femoral tendon. Once the vastus medialis and lateralis are detached from the margins of the patella, the knee is extended, and the distal ends of the vasti are sutured to the tongue of the rectus tendon. Effective extension facilitates flexion to 90°.¹⁸⁴ The authors recommend a modification of this technique in which a Z lengthening of the quadriceps tendon is performed after the vastus lateralis is removed distally from the patella and the quadriceps tendon.

Several series and case reports evaluating quadricepsplasty in adult patients report positive outcomes with most patients achieving good or excellent flexion with minimal complications.^{183,185,187-189} Reports on quadricepsplasty used to treat conditions other than patellofemoral instability in children have reported similar positive outcomes.^190-192 As quadricepsplasty for patellar instability is relatively rare in pediatric patients, there is not much relevant literature. However, Kocon and colleagues¹⁹³ reported results of quadricepsplasty and quadricepsplasty combined with the modified Galeazzi procedure in 8 children (10 knees) with a mean follow-up of 3.25 years. Seventy percent of cases resulted in stabilization and correction of patellar position, and only 2 postoperative redislocations were noted.¹⁹³ Additionally, in a study evaluating 6 patients suffering from patellar instability, 2 of whom were obligate dislocators, quadricepsplasty resulted in patellar stability, satisfaction, and near normal gait patterns.¹⁹⁴

Figure 10 shows the surgical algorithm used for patellar instability characteristics.

CONCLUSION

Patellofemoral joint stability relies on a complex interplay of musculotendinous units, ligaments and the osteocartilaginous morphology of the patellofemoral joint. Patellar instability in pediatric patients is different from adults. Having an in-depth understanding of the remodeling potential, the insertion sites for the MPFL and its relationship to the physis are of utmost importance when planning surgery. Reducing and maintaining the patella within the patellofemoral joint early enough can allow for remodeling of the patella and/or the trochlea to provide for lasting stability. Appropriate surgical principles, such as tensioning, can help both prevent continued pain and minimize future complications.

ABSTRACT

Patellar instability in children and adolescents is a challenging subset to treat. Varied forms of instability, ranging from episodic dislocation to fixed dislocation, have been recognized. It is of utmost importance for the treating physician to recognize these different patterns of instability and their associated risk factors, as more complex patterns of instability would require more extensive surgical procedures. Medial patellofemoral ligament (MPFL) reconstruction, by itself, may not suffice or may not be appropriate for the more complex instability patterns. Appropriate and early treatment of such instability in children would allow for functional progression and possible remodeling of the trochlea. However, early treatment has the associated risk of growth disturbances when surgical procedures are performed around open physis or if adult-type bony procedures are performed in children. Recent knowledge about the relationship between trochlea, MPFL femoral attachment, and distal femoral physis could help to advance safe surgical care for these patients. This article reviews the pathophysiology, risk factors, and the existing classification systems for patellar instability in children and adolescents. It focuses on varied surgical techniques, which are unique to the pediatric population, and summarizes the outcomes of these surgical techniques.

Continue to: EPIDEMIOLOGY

EPIDEMIOLOGY

In a prospective 2-year study of Finnish children, the annual incidence rate of patellar instability was 43/100,000 pediatric population.¹ In patients 9 to 15 years of age, the incidence was approximately 1/1000.¹ In another study, patients at highest risk for a first-time patellar dislocation were females aged 10 to 17 years.² In a study in patients with traumatic hemarthrosis, 36% in the younger age group (10-14 years) and 28% in the older age group (15-18 years) had sustained patellar dislocation. In contrast, 22% in the younger age group and 40% in the older age group had sustained an anterior cruciate ligament tear.³

Approximately one-half of patients who dislocate their patella suffer from long-term complications.^4,5 These complications include recurrent instability, patellofemoral pain, osteochondral lesions, and eventual arthritis.^1,4,5 Young, active individuals are more prone to these issues.⁶ Also, 39% or more of patellar dislocation patients have an associated osteochondral fracture that might influence the management.¹ Thus, patellar instability in young patients is an area of concern.

DEVELOPMENTAL ANATOMY

At 4-week gestation, the patellofemoral joint is an ectodermal sac filled with mesenchyme of the somatic mesoderm.⁷ Mesenchymal condensations then appear at 4 to 5 weeks gestation, followed by chondrification of both the femur and patella.⁷ The joint space is present by 6 weeks, and the patellar and distal femoral condyles are present at 7 weeks gestation.⁷ By 8 weeks gestation, the basic knee anatomy resembles that of an adult with the chondroepiphysis forming the articular surfaces of the femur, tibia, and patella.⁷ By this time, the extensor mechanism is formed, and active joint motion has begun, facilitating the development of the trochlear sulcus.⁷ The secondary ossification center in the distal femoral epiphysis forms around 36 weeks gestation.⁸ Postnatally, both the patella and distal femur grow through endochondral ossification.^9,10

The patella is the largest sesamoid bone in the human body.¹¹ The patella begins as a dense consolidation of cells that differentiate as the quadriceps mechanisms develop.^12,13 The patellar anlage becomes distinguishable within the quadriceps tendon around 7.5-week gestation.¹² The morphology of the patella conforms to the distal femur.¹² The patella molds or re-models as the knee begins to move in response to mechanical stresses.⁷ The patella increases in relative size during the first 6 months of gestation, then enlarges proportionately to the rest of the bones.⁷ Ossification begins around 3 years of age for females and 4 to 5 years of age for males.^8,14 The ossification center may appear irregular as it rapidly expands.¹⁴ Ossification proceeds in a proximal to distal direction, thus giving a spurious estimation of patellar height on radiographs in children. The overall morphology of the cartilaginous patella during development is comparable to the final mature shape.¹⁴ Abnormal contact stresses on the articular surface of the patella during skeletal immaturity can lead to deformation.⁷

Ultrasonographic measurements in normal patients show that trochlear groove (TG) morphology is present early and becomes more radiographically apparent as distal femoral ossification is completed.¹⁵ Anatomic dissections of aborted fetuses have verified the morphology of the TG as it remains constant during growth and the groove morphology is the same for both fetuses and adults.¹⁶ An ultrasound study performed on patients aged 12 to 18 years showed the cartilaginous sulcus angle (CSA) remained constant throughout all age groups (146°).¹⁷ The CSA however, differed in patients who suffered a patellar dislocation (average, 164°; range, 154°-195°) compared with normal knees (average CSA, 145°; range, 131°-158°).^15,17,18 The osseous sulcus angle, on the other hand, appears flat at birth and the TG deepens with age. This increase in depth is more of a reflection of progressive ossification of a well-formed cartilaginous trochlea, rather than a true deepening of the sulcus.¹⁷ Thus, the axial radiographic view of the patella provides misleading information about the sulcus angle in children and should not be used to define trochlear morphology.

Continue to: MEDIAL PATELLOFEMORAL LIGAMENT ANATOMY

The medial patellofemoral ligament (MPFL) functions to limit the lateral translation of the patella.¹⁹ The attachment sites on the femur and patella for the MPFL have been studied in children.^20-23 Cadaveric dissections in specimens aged 2 to 11 years have noted the patellar attachment to be an average of 12 mm in length with the midpoint approximately 5 mm superior to the mid-pole of the patella.²² The patellar footprint of the MPFL insertion was a mean 41% of the entire patellar length.²²

It is important to be aware of the characteristic anatomy of the MPFL, as fixation points should mimic the anatomic insertion as best as possible while also avoiding violation of the nearby physis. The MPFL originates between the adductor tubercle and the medial femoral epicondyle just distal to the distal femoral physis and attaches to the superomedial aspect of the patella.^20-25 In relation to the physis in pediatric patients, the midpoint of MPFL insertion has been measured to be 4 mm to 9 mm distal to the femoral physis.^21,24,25 These measurements represent averages as cadaveric studies have reported that some part of MPFL femoral insertion extends proximal to the distal femoral physis.²¹ A recent report of physeal injury to the posterior distal femoral physis during MPFL reconstruction leading to femoral flexion deformity highlights the importance of physeal-respecting surgery.²⁶

TROCHLEA AND ANTERIOR DISTAL FEMORAL PHYSIS

The relationship between the proximal aspect of the trochlea and the anterior distal femoral physis has been recently studied in 175 knees with dysplastic trochlea.²⁷ Based on magnetic resonance imaging evaluation, the lateral aspect of the trochlea extended proximal to the anterior distal femoral physis in 13% of patients and was at the level of the anterior physis in another 13% of patients (Figure 1).²⁷ Hence, a cautious approach is recommended for any surgery to address trochlear dysplasia or trochlear bump in younger patients to prevent iatrogenic injury to anterior distal femoral physis and resultant genu recurvatum. The distance between the trochlea and the physis increased with increasing age.

LIMB ALIGNMENT

Physiologically, the quadriceps angle (Q angle) changes through the course of growth. As children begin standing and walking, they stand with their feet wider apart and in genu varum.²⁸ Physiologic genu varum can reach 15°.²⁸ This degree lessens during the first 1.5 to 2 years of life, transitioning to physiologic valgus of nearly 12° by 3 years of age.²⁸ Genu valgum, thereafter, gradually decreases to reach the adult value of around 7° to 8° by age 7 years.²⁸ Increased genu valgum is a risk factor for patellar instability. In skeletally immature patients, correction of genu valgum through guided growth may be desirable in patients undergoing patellar stabilization surgery (Figures 2A, 2B).²⁹

PATHOPHYSIOLOGY OF PEDIATRIC PATELLAR DISLOCATION

TROCHLEAR DYSPLASIA

Trochlear dysplasia is an abnormal shape and depth of the TG.³⁰ Up to 96% of patients with patellar dislocation have trochlear dysplasia.^30-33 In a study of patellar instability in children, at least 1 of the 3 signs of trochlear dysplasia (the crossing sign, supratrochlear bump, and double contour sign) was present on lateral radiographs.³⁴ In another study on the growth of trochlear dysplasia in children and adolescents, all grades of trochlear dysplasia were present at all ages (ie, the dysplasia was most likely present at birth and did not necessarily worsen with age and growth).³⁵ The linear dimensions of lateral and medial condylar height as well as trochlear bump increased with age but both the sulcus angle and shape of the trochlea did not change significantly.³⁵ Remodeling of a dysplastic trochlea can happen if the patella is stabilized and appropriately located at a younger age, preferably before 10 years of age.^36,37

Continue to: PATELLAR HEIGHT

The role of patellar height in patellar instability has been well established.³⁸ In patients with patella alta, the patella remains proximal to the TG during the greater arc of knee motion, which predisposes it to patellar instability. Calculation of patellar height in children could be challenging due to incomplete ossification, as well as asymmetric ossification of the patella and the tibial tubercle (TT). Since the patella ossifies from proximal to distal, most radiographic methods that measure the patellar height from the distal aspect of the patella provide a spurious elevation of the measurement.

The Caton-Deschamps (CD) method measures the length of the patellar articular surface and the distance from the inferior edge of the articular surface to the anterosuperior corner of the tibial plateau.³⁹ A ratio >1.3 signifies patella alta. The CD ratio has been verified as a simple and reliable index for measuring patellar height in children.⁴⁰ Two other methods have been described for determining patellar height in children.^41,42 Based on anteroposterior (AP) radiographs of the knee in full extension, Micheli and colleagues⁴¹ calculated the difference between the distance from the superior pole of the patella to the tibial plateau and the length of the patella. A positive difference signified patella alta. The Koshino method involves the ratio between a reference line from the midpoint of the patella to the midpoint of the proximal tibial physis and a second distance from the midpoint of the distal femoral physis to the midpoint of the proximal tibial physis on lateral knee radiographs.⁴² Normal values range from 0.99 to 1.20 with the knee in >30° flexion, in children 3 to 18 years of age.

HYPERLAXITY

In contrast to adults, children have increased levels of collagen III compared with collagen I, which is responsible for tissue elasticity.⁴³ Tissue elasticity leads to increased joint mobility, which is more common in children. Joint hypermobility or hyperlaxity has to be differentiated from symptomatic instability. The traditional Beighton score identifies individuals as having joint hypermobility with a score of 5/9 or higher in school-aged children.^44-46 Smits-Engelsman and colleagues⁴⁴ suggested using stricter criteria with scores of 7/9 or higher being indicative of hyperlaxity in school-aged children. A study of 1845 Swedish school children noted that females have a higher degree of joint laxity.⁴⁵ Maximal laxity was noted in females at 15 years of age.⁴⁵ Hyperlaxity has been demonstrated to be greater on the left side of the body⁴⁴ and can be part of generalized syndromes including Down’s syndrome, Marfan’s syndrome, or Ehlers-Danlos syndrome.

LIMB TORSION

Staheli and colleagues⁴⁷ described the normative values of a lower extremity rotational profile, including femoral anteversion and tibial torsion. Children normally have increased femoral anteversion, which decreases with growth. Miserable malalignment is a term used to denote increased femoral anteversion and increased external tibial torsion.^48,49 These rotational abnormalities can increase the Q angle and the lateral forces on the patella. Femoral anteversion or internal rotation of the femur of 30° significantly increases strain in all areas of the MPFL.⁴⁸ This increased strain may lead to MPFL failure and patellar instability.⁴⁸ Increased internal rotation of the femur also increases contact pressure on the lateral aspect of the patellofemoral joint.⁴⁸ Miserable malalignment frequently manifests following a pubertal growth spurt and may require femoral and tibial osteotomy.⁵⁰

SYNDROMIC ASSOCIATIONS

Several syndromes have patellar instability as a part of their manifestation. The more common syndromes include nail-patella syndrome, Kabuki syndrome, Down’s syndrome, and Rubinstein-Taybi syndrome.^51-54 Other syndromes less commonly associated with patellar instability include Turner syndrome, patella aplasia, or absent patella syndrome. Since many patients with syndromic patellar instability are functionally limited, they may not require an aggressive approach to treatment. When treating these patients, it is important to recognize the unique features of a specific syndrome, which may affect the anesthesia risk profile, management decisions, rehabilitation, and prognosis.

Continue to: MPFL TEAR PATTERN

The MPFL serves as an important constraint to the patella to prevent lateral dislocation, primarily during the first 20° to 30° of knee flexion.^55,56 Injury to the MPFL is noted in over 90% of patients who suffer a patellar dislocation.⁵⁷ The location of MPFL tears in pediatric patients is variably reported at the patellar attachment (10%-61%), femoral attachment (12%-73%), both (12%-35%) or mid-substance (2.5%-15%).^25,57 The most common tear patterns in pediatric patients are tears at the patellar attachment.^25,57 This tear pattern may be accompanied by an avulsion fracture of the medial rim of the patella, though this fracture, being extra-articular, seldom needs treatment.

CLASSIFICATION

While several authors have established extensive classification systems of patellar dislocation based on both clinical and radiographic presentation and reviews of the literature, a single classification system has not been recognized as the gold standard. In this section, in addition to presenting our preferred methods of classification, we will review some of the more recent and extensive classification systems for patellar dislocation and patellar instability.

Dejour and colleagues³¹ initially used both the presence of patellofemoral anatomic abnormalities and pain to define 3 types of patellar instability: major, objective, and potential patellar instability. Major patellar instability indicates that the patient has experienced more than 1 documented dislocation, objective instability involves one dislocation in addition to an associated anatomic abnormality, and potential patellar instability refers to cases in which the patient has radiographic abnormalities and patellar pain.³¹ Garin and colleagues⁵⁸ more simplistically divided patellar dislocation patients into 2 groups: major (permanent or habitual) dislocation of the patella and recurrent dislocation. Sillanpaa⁵⁹ stressed the distinction between first-time dislocation and recurrent dislocation specifically in the context of acute injuries. These classification systems were formulated with adults as the most relevant population; however, classifications targeted specifically to pediatric patients have recently been presented in the literature.

Historically, pediatric patella dislocations were simply categorized as traumatic or congenital.⁶⁰ In 2014, Chotel and colleagues⁶¹ focused on classifying patellar dislocation by extensively reviewing anatomic, biomechanical, pathophysiological, and clinical patterns seen most commonly in children. They included 5 categories: congenital dislocation, permanent dislocation, habitual dislocation during knee flexion, habitual dislocation during knee extension, and recurrent dislocation; however, they did not address traumatic dislocations.⁶¹ Congenital dislocation is a rare condition, typically presenting at birth, which produces a pattern of functional genu valgum.⁶² Permanent dislocation typically presents after the child has started walking, but before the age of 5 years.⁶¹ The 2 variations of habitual dislocation typically present between ages 5 and 8 years.⁶¹ The final category is the most common and typically occurs during pre-adolescence or adolescence as a result of an atraumatic or trivial traumatic event or sports injury.¹ Using more specific terminology, Hiemstra and colleagues⁶³ modeled a classification system based on the traumatic, unilateral, bankart lesion, surgery (TUBS)/atraumatic, multidirectional, bilateral, rehabilitation, inferior shift (AMBRI) for shoulder dislocation classifications. The patellar dislocation system is used to identify 2 distinct subsets of patients in the patellofemoral instability population. One subset is defined by the acronym WARPS (weak, atraumatic, risky anatomy, pain, and subluxation), the other is STAID (strong, traumatic, anatomy normal, instability, and dislocation).⁶⁴ Patients categorized by the WARPS acronym tend to experience atraumatic onsets of patellofemoral instability and demonstrate anatomic issues that increase this instability. These underlying anatomic issues include valgus alignment, ligamentous laxity, rotational abnormalities, shallow and short TG, and patella alta. On the other hand, STAID patients describe a traumatic dislocation event and do not have underlying anatomic abnormalities that predispose them to instability.⁶⁴

Taking into account these previous classifications, Frosch and colleagues⁶⁵ added specific pathologies including “instability,” “maltracking,” and “loss of patellar tracking,” in addition to both clinical and radiographic factors to define 5 types of patellar dislocation and their specific treatment recommendations.⁶⁵ Type 1 involves simple dislocation with neither maltracking nor instability and a low risk of redislocation.⁶⁵ Type 2 is defined as primary dislocation followed by subsequent high risk of dislocation and no maltracking.⁶⁵ Type 3 is divided into 5 subcategories of instability and maltracking issues involving soft tissue contracture, patella alta, pathological tibial tuberosity, and TG distance.⁶⁵ Type 4 is defined as the highly unstable “floating patella,” and type 5 involves patellar maltracking without instability ⁶⁵. In terms of treatment, conservative rehabilitation is recommended for type 1 whereas MPFL reconstruction tends to show positive outcomes for both types 2 and 3.^66-70

Continue to: Parikh and Lykissas recently published...

Parikh and Lykissas recently published a comprehensive classification system of 4 defined types of patellar dislocation in addition to voluntary patellar instability and syndromic patellar instability (Table).⁶⁰ The 4 types are Type 1, first-time patellar dislocation; Type 2, recurrent patellar instability; Type 3, dislocatable; and Type 4, dislocated. Type 2 is further subdivided into Type 2A, which presents with positive apprehension signs, and Type 2B, which involves instabilities related to anatomic abnormalities.⁶⁰ A distinction is also made between Type 3A or passive patellar dislocation and Type 3B habitual patellar dislocation.⁶⁰

The classification system proposed by Green and colleagues is more simplified with 3 main categories (Table) of pediatric patellar dislocation: traumatic (acute or recurrent), obligatory (either in flexion or extension), and fixed laterally.^71,72 The acute traumatic categorization refers to patients who experienced an initial dislocation event due to trauma whereas recurrent traumatic involves repeated patella dislocations following an initial incident. Studies report that between 60% to 70% of these acute traumatic dislocations occur as a result of a sports-related incident.^2,33,73 Obligatory dislocations occur with every episode of either knee flexion or extension, depending on the subtype. Obligatory patella dislocation in flexion typically cannot be manipulated or relocated into the trochlea while the knee is fixed but does reduce into the trochlea in full extension. Fixed lateral dislocations are rare, irreducible dislocations in which the patella stays dislocated laterally in flexion and extension. These dislocations often present with other congenital abnormalities. Each of these categories can be further specified as syndromic if the dislocation is associated with genetic or congenital conditions including skeletal dysplasia, Ehlers-Danlos syndrome, cerebral palsy, Marfan disease, nail-patella syndrome, Down syndrome, Rubenstein-Taybi syndrome, and Kabuki syndrome.^{51-54,61,74-76}

SURGICAL TECHNIQUES IN SKELETALLY IMMATURE PATIENTS

While nonsurgical, conservative treatment involving physical therapy and activity modification is recommended for most patients who experience first-time traumatic patellar dislocations, many patients experience complicating factors that indicate them for surgery. These factors include recurrent dislocation, risk factors for patellofemoral instability, underlying malalignment issues, and congenital deformities. When evaluating these factors, particularly patellofemoral instability, the authors recommend assessing osteochondral lesions, age, skeletal maturity, number of previous dislocations, family history, and anatomic risk factors.^2,5,77-79 Extra care should be taken when considering surgical treatment for skeletally immature patients at elevated risk for recurrent instability as the risk of cartilage damage in these cases is high.^80-82

Recently, there has been a reported increase in surgical treatment for patellar instability in the skeletally immature.⁸³ This finding may be attributed to heightened awareness of factors that indicate patients for surgical treatment and increased familiarity of surgeons with newer techniques.⁸³ Many surgical techniques have been described to address patellar instability involving both soft-tissue procedures and bony corrections.⁸⁴ In this article, we discuss the various surgical techniques for MPFL reconstruction, quadricepsplasty, and distal realignment. These procedures can be paired with any number of additional procedures including, but not limited to, lateral retinacular release or lengthening, chondroplasty, TT osteotomy (in skeletally mature patients), and removal of loose bodies.⁸³

There is a need for more comprehensive studies, particularly randomized controlled trials, to evaluate the outcomes for both surgical and nonsurgical treatments for first-time dislocations. In the current literature, only very recently have surgical treatments shown outcomes that are more positive. In 2009, Nietosvaara and colleagues⁸⁵ conducted a randomized controlled trial of nonoperative and operative treatment of primary acute patellar dislocation in both children and adolescents. After a long-term mean follow-up of 14 years, there was not a significant difference between the groups in recurrent dislocation and instability, subjective outcome, or activity scores.⁸⁵ In a subsequent review of 5 studies including 339 knees, Hing and colleagues⁸⁶ also found similar results in both the operative and nonoperative cohorts at risk of recurrent dislocations, Kujala scores, and reoperations. However, a recent systematic review comparing redislocation rates and clinical outcomes between surgical and conservative management of acute patellar dislocation reported more positive outcomes for the surgical cohort.⁸⁷ This review included 627 knees, 470 of which received conservative management, 157 of which received operative treatment. The conservative cohort was followed for an average of 3.9 years and had a 31% rate of recurrent dislocation while the surgical group was followed for a mean 4.7 years and experienced a 22% redislocation rate.⁸⁷ This study indicates that operative management for acute first-time dislocations may be the preferred treatment option.

Continue to: A potential reason some of these studies...

A potential reason some of these studies did not show any significant difference between the operative and nonoperative cohort could be that the surgical cohorts included a wide range of procedures including lateral releases and MPFL repairs. Recent publications have indicated that these techniques do not produce overall positive outcomes. While each surgical treatment plan is unique depending on the patient; recently, MPFL reconstruction has been shown to have better outcomes than both nonoperative management and simple medial repair and/or lateral
release.^67,88-90

MPFL RECONSTRUCTION

INDICATIONS/OVERVIEW

The MPFL is an important stabilizer for the knee that primarily resists lateral translation of the patella. Damage to the MPFL is very common in acute patellar dislocations with up to 90% of first-time dislocations resulting in injury to the MPFL.^91,92 Historically, simple medial and/or lateral MPFL repairs have not been shown to improve patellofemoral kinematics significantly and often result in recurrence.^90,93 To address this issue, during the past few decades, numerous MPFL reconstruction techniques have been developed to reconstruct a stronger ligament with the same kinematics as the anatomic MPFL.^{2,19,69,81,94-106} The ultimate goal of MPFL reconstruction is to reestablish the anatomic “checkrein” to guide the patella into the trochlea between 0° and 30° of knee flexion.^107,108 An essential secondary surgical goal in skeletally immature patients is to avoid damaging the distal femoral physis.

There are many variations in both the grafts used to replace the MPFL and the means by which to secure them. The ones discussed below include free semitendinosus or gracilis autografts or grafts constructed from a pedicled adductor, patellar, or quadriceps tendon.^69,105,109 While not used as frequently, allografts have also been used.¹¹⁰ Methods to secure these grafts in osseous tunnels include suture anchors or tenodesis screws. Incomplete osseous sockets or medial-sided bone tunnels have also been used as a method to decrease patellar fractures as they preserve the lateral patellar cortex.^111-114

DOUBLE-BUNDLE HAMSTRING AUTOGRAFT

The technique most often used by the author is a double-bundle hamstring autograft harvested from either the semitendinosus or the gracilis secured by short patellar and femoral sockets (Figure 3). After harvesting the hamstring graft from a posteromedial incision, an approximately 90-mm graft is prepared with Krackow stitches to secure 15 mm of the tendon in each socket.¹¹⁵ Lateral radiographs are used intraoperatively to ensure the guidewire for the femoral drill hole falls along the posterior cortex of the diaphysis of the femur while AP radiographs confirm placement distal to the physis. It is important to take both AP and lateral radiographs intraoperatively due to the concave curvature of the distal femoral physis. This unique anatomy can make a point that is located distally to the physis on the AP view appear on or proximal to it on the lateral cross reference view.^24,116 For the patellar socket, 2 short sockets are made in the superior half of the patella. Once the sockets have been drilled, the graft is adjusted so that the patella stays seated in the center of the trochlea between 20° and 30° of flexion. This anchoring is accomplished by securing the graft while the knee is kept at 30° of flexion. Proper tension is confirmed by ensuring that the graft does not allow lateral patella movement over one-fourth the width of the patella in extension while crepitation must not appear throughout the ROM.⁹²

QUADRICPETS TENDON TRANSFER

A combination of techniques by Steensen and colleagues,¹⁰⁵ Goyal,¹⁰⁹ Noyes and Albright,¹¹⁷ and Pinkowsky and Hennrikus¹¹⁸ describe an MPFL reconstruction in which the proximal end of a small medial portion of the quadriceps tendon is released and then attached to the medial epicondyle through a subcutaneous tunnel (Figure 4). This technique is particularly useful for cases in which the extra strength provided by the bone-quadriceps tendon is necessary to correct more severe dysplasia. Leaving the distal end of the quadriceps tendon intact at its patellar insertion, a graft of about 8 mm x 70 mm thickness is harvested from the tendon. The free distal end of the tendon is then run anatomically through the synovium and retinaculum to be either sutured to the medial intermuscular septum at the medial femoral epicondyle or fixed in femoral tunnel using interference screw.^105,109,118 The placement of the femoral fixation point is essential to ensure positive surgical outcomes. If the graft is secured too anteriorly, it may be too loose in extension and too tight in flexion, both of which can lead to postoperative pain, loss of normal kinematics, and overload of the medial patellofemoral cartilage.^119-121 Once the ideal placement of the femoral fixation point has been confirmed by intraoperative radiographs, the graft is secured with a small absorbable suture.^122,123 While this technique has good clinical results, the longitudinal scar that results from graft harvesting is cosmetically unappealing, and it is technically challenging to harvest a consistent strip of the quadriceps tendon. To address some of these concerns, Fink and colleagues¹²⁴ described a new harvesting technique that produces more consistent grafts and requires a smaller incision.

Continue to: ADDUCTOR MAGNUS TENDON TRANSFER

This technique is a double-bundle MPFL reconstruction that uses a pedicled graft of the distal adductor magnus tendon and suture anchors or incomplete osseous sockets to recreate the MPFL anatomically (Figure 5). Avikainen and colleagues⁹⁶ and Sillanpää and colleagues¹²⁵ described this procedure as a progression from the original single-strand adductor magnus transfer technique. First, maintaining the distal insertion, a graft of approximately 14 cm to 18 cm is harvested from the adductor tendon and then passed through a subcutaneous tunnel between the distal vastus medialis obliquus and the superficial joint capsule. The graft is then looped at the medial patella so that the distal bundle runs back to the adductor tubercle.¹²⁵ With the knee at 30° of flexion to assure proper tension, the graft is secured at both the patella and near the adductor tubercle with suture anchors.¹²⁵ Hambridge and colleagues¹²⁶ compared a similar adductor magnus transfer with other pedicled techniques including bone-quadriceps tendon autograft and bone-patellar tendon allograft and found positive results for all 3 methods of reconstruction.

HEMI-PATELLA TENDON TRANSFER

In a similar technique to the adductor tendon transfer, the medial section of the patellar tendon is harvested from the TT and run from its proximal insertion at the medial patella to the medial femoral attachment via a subcutaneous tunnel. The free end of the graft is then secured with suture anchors or incomplete osseous sockets with the knee at 30° of flexion.¹²⁷

HAMSTRING GRAFT WITH ADDUCTOR TENDON AS A PULLEY

Several techniques opt to use a more dynamic model of MPFL reconstruction in which the adductor tendon or medial collateral ligament (MCL) is used as a pulley for the hamstring graft (Figure 6).^128,129 The site of the pulley approximates the normal attachment of the MPFL to the femur and so acts as an effective anatomic replica of the MPFL origin. A semitendinosus graft is harvested and is prepared with continuous sutures, and 2 tunnels to secure the graft are drilled into the patella. The graft is then run subcutaneously from the medial side of the patella to the adductor magnus tubercle into which an osteoperiosteal tunnel is drilled at its distal femoral insertion. The graft is looped through the adductor tunnel and secured with sutures. Proper knee kinematics was ensured by placing the knee at 30° of flexion as the ends of the tendon are secured to the patella.^114,130

HAMSTRING GRAFT WITH MCL AS A PULLEY

The MCL can also be used as a pulley rather than the adductor tendon. The semitendinosus graft is harvested and prepared and the patella drilled as it is in the previous technique. The MCL was fashioned into a pulley by making a slit in its posterior one-third. The semitendinosus graft is looped through this slit, and both ends of the graft are held in place with suture anchors on the surface of the patella.¹²⁹

ADDITIONAL PROCEDURAL COMBINATIONS

Depending on the needs of the individual patient, MPFL reconstruction, and other patellar stabilization techniques can also be combined with additional procedures. Arshi and colleagues⁸³ conducted a review of 6190 adolescents surgically treated for patellar instability and reported the most common additional procedures performed at the time of the stabilization. They found 43.7% of the population underwent lateral retinacular release, which while not effective as an isolated technique to treat patellar instability, has often been used in combination with MPFL reconstruction.^131-133 There is currently a lack of consensus regarding the success of adding a lateral release to the reconstruction. Some studies report no difference while others report a decrease in stability after lateral release.^90,134-136 While lateral retinacular release has been shown to decrease the force required to displace the patella, it can be surgically indicated in certain patients undergoing MPFL reconstruction.¹³¹ The authors advocate that if the lateral retinaculum is tight such that centralized patellar tracking is inhibited following the reconstruction, or if the patella cannot be pushed passively from a laterally tilted position to the neutral horizontal position, lateral retinacular lengthening should be performed to improve kinematics.¹³²

Continue to: Arshi and colleagues...

Arshi and colleagues⁸³ also reported a high rate of cartilage procedures, with chondroplasty performed in 31.1% and chondral fragment/loose body removal in 10.2%. These statistics suggest that a significant level of cartilage damage has occurred by the time of surgery.⁸³

COMPLICATIONS

As MPFL reconstruction techniques have only recently been popularized and developed, there are not many comprehensive studies evaluating the outcomes and complications associated with these procedures. However, in the current literature, there is a general consensus that patients usually experience positive short-term clinical outcomes and relatively low complication rates.^68,77 In one of the largest retrospective cohort studies of pediatric patients undergoing MPFL reconstruction, Parikh and colleagues¹¹⁴ reported both the type and rate of complications. They found complications occurred in 16.2% of patients, and the most common complications were recurrent patellar instability, patellar fractures, patellofemoral arthrosis, motion deficits, and stiffness with over half classified as avoidable. Most of these complications were due to technical errors with episodes of recurrent instability only reported in 4.5% of patients.¹¹⁴ In a comprehensive meta-analysis of MPFL reconstruction studies, Shah and colleagues¹³⁷ reported a complication rate of 26% in both pediatric and adult patients. The cohort was not stratified by age, yet complications were similar to those reported by Parikh and colleagues,¹¹⁴ including pain, loss of knee flexion, wound complications, and patellar fracture.¹³⁷

As indicated by the frequency of technical complications reported by Parikh and colleagues,¹¹⁴ extra caution should be taken in the operating room to minimize potential errors. In techniques that require drilling of femoral sockets, proper length for and placement of the graft is essential to reestablish proper kinematics. Studies have reported that placing the femoral socket too proximally can result in loss of ROM during flexion and increased compressive forces across the patella.¹³⁸ A graft that is too short can have similar negative outcomes, and a graft that is too long can result in recurrent instability. Positioning the graft while the knee is in 30° of flexion can help ensure the proper length and tension is achieved. Once the graft is in place, it is important to ensure the ROM and isometry before completing the fixation.⁷² It is also essential to be vigilant about potential violation of the physes and subsequent growth disturbances. To establish the safest angles for drilling the distal femoral epiphysis for graft placement, Nguyen and colleagues¹³⁹ conducted a study using high-resolution 3-dimensional images of cadaveric distal femoral epiphyses. By recording which tunnels disrupted the physis before reaching 20 mm of depth, the authors concluded that it is safest to drill distally and anteriorly at an angle between 15° and 20°.¹³⁹ This technique should minimize damage to the physis, notch, and distal femoral cartilage and decrease potential complications.¹³⁹

OUTCOMES

In general, the literature reports positive outcomes for MPFL reconstruction—in both studies that address a specific technique and all-encompassing studies. Outcomes are typically reported as Kujala and Tegner scores, results from clinical examinations, and rates of subsequence recurrences. Several recent studies have also evaluated the ability of MPFL reconstruction to restore proper kinematics. Edmonds and colleagues¹⁴⁰ evaluated the difference in patellofemoral joint reaction forces and load experienced by 3 groups of adolescents: a cohort treated with MPFL reconstruction, a cohort treated with soft-tissue realignment of the extensor mechanism (the Insall method), and controls. While both surgical techniques were able to restore medial constraints to the patella, the study showed that only the MPFL reconstruction cohort experienced joint reaction forces that were analogous to the control group. In comparison, the cohort that was treated with soft-tissue realignment alone experienced higher patellofemoral joint reaction forces and did not regain normal joint mechanics.¹⁴⁰ These results can be used to advocate for the further use of MPFL reconstruction as an effective anatomic replacement of the native ligament. Radiographic studies have similarly reported MPFL reconstruction as an effective means to restore anatomic normality. Fabricant and colleagues¹⁴¹ conducted a radiographic study in which patella alta was corrected to normal childhood ranges in patients who underwent MPFL reconstruction technique using a hamstring autograft. Lykissas and colleagues¹⁴² corroborated these results with another radiographic study that reported small but significant decreases in the Blackburne-Peel index and CD index following MPFL reconstruction in 25 adolescents. As correction of patella alta allows the patella to rest in a deeper, more secure position in the TG, these results indicate that effective early MPFL reconstruction can correct for patellar anatomic abnormalities that could be future risk factors.^143,144 Several studies have also reported outcomes addressing specific MPFL techniques; these are reported and discussed in this article.

OUTCOMES BY TECHNIQUE

HAMSTRING AUTOGRAFT

Reports on outcomes following MPFL reconstructions using hamstring autografts have been particularly promising. A cohort of 21 skeletally immature patients who underwent MPFL reconstruction was evaluated pre- and postoperatively with an average of a 2.8-year follow-up. The authors of the study reported no redislocation events and significant improvement in the Kujala scores, and patients were able to return to athletic activities safely.¹⁴⁵ Previous studies report similar positive increases in Kujala scores, subjective patient reports, and lack of subsequent redislocation for patients who underwent either semitendinosus or gracilis autograft MPFL reconstructions. One such study further documented an average patellar inclination angle decrease from 34.3° to 18.6° following MPFL reconstruction.¹⁴⁶ However, while the literature typically reports positive Kujala scores and subjective outcomes for the hamstring autograft procedure, a study arthroscopically evaluating patellar tracking immediately following surgery and then at 6 to 26 months follow-up found that patellar tracking correction was not maintained for all patients who underwent this type of MPFL reconstruction.¹⁴⁷

Continue to: QUADRICEPS TENDON TRANSFER OUTCOMES

Studies specifically evaluating the quadriceps tendon transfer technique for MPFL reconstruction in children are sparse, but authors have reported positive clinical outcomes and low complication rates in adults. After following 32 young adults who underwent this MPFL reconstruction technique for 3 years, Goyal¹⁰⁹ reported a significant increase in mean Kujala scores from 49.31 to 91.25 and no complications or redislocation. He argues this type of quadriceps graft has a high success rate because it is anatomically more similar to the MPFL than other grafts and does not require additional patellar fixation.^101,109 Similar positive Kujala scores and minimal complications have been reported in adult patient populations.¹⁴⁸ Abouelsoud and colleagues¹⁴⁹ conducted one of the few studies in skeletally immature patients and reported similarly positive results with no redislocations and significantly improved Kujala scores at a mean follow-up of 29.25 months in their 16-patient cohorts.

ADDUCTOR MAGNUS TENDON TRANSFER

After initially describing this technique in 14 adult patients, Avikainen and colleagues⁹⁶ followed this cohort and reported positive subjective results and only 1 redislocation. In a more recent study in which the adductor tendon transfer technique was compared with the quadriceps tendon transfer described above and the bone-patellar tendon allograft, Steiner and colleagues⁶⁹ reported similarly significant improvement in all cohorts in Lysholm, Kujala, and Tegner scores with no redislocations. Additionally, Malecki and colleagues¹⁵⁰ followed a cohort of 33 children with 39 knees diagnosed with recurrent patellar dislocation, who underwent MPFL reconstruction using the adductor magnus tendon. After evaluating this cohort functionally and radiographically, the authors reported improvements in Lysholm and Kujala scores, patellar tilt and congruence angles, and peak torque of the quadriceps muscle and flexor.¹⁵⁰ However, this cohort did report postoperative redislocations in 36.4% of patients (4 of 11).¹⁵⁰

HEMI-PATELLA TENDON TRANSFER

In 2012, in the first randomized controlled trial, Bitar and colleagues⁶⁷ compared the outcomes of patients who underwent MPFL reconstruction via the hemi-patellar tendon technique with those who were managed nonoperatively with immobilization and physiotherapy after first-time patellar dislocation. At 2-year follow-up, the surgical cohort presented positive results with a significantly higher mean Kujala score (88.9 to 70.8) and no redislocations or subluxations. In contrast, 35% of nonoperative cases presented with recurrences and subluxations over the 2-year period.⁶⁷

MCL OR ADDUCTOR TENDON AS A PULLEY

Studies have reported good postoperative results and low complication rates for these dynamic techniques.^128,129 In terms of kinematics, while hypermobility and patellar height were not fully corrected, improvements in patellar tilt and lateral shift were reported in a cohort of 6 patients with a minimum 4-year follow-up.¹²⁹ To further evaluate whether the more dynamic pulley reconstruction technique resulted in better outcomes, Gomes and colleagues¹²⁸ compared the subjective reports, clinical evaluations, and complication rates of patients who underwent MPFL reconstruction with a rigid adductor magnus fixation vs a semitendinosus tendon dynamic femoral fixation. One case in the rigid cohort experienced a subsequent subluxation, while patients in the semitendinosus group had better subjective reports and a higher rate of return to sport.¹²⁸ More recently, Kumahashi and colleagues¹⁵¹ specifically studied the outcomes of the MCL tendon as a pulley in 5 patients aged 14 to 15 years. They reported similar successful results as no patients experienced recurrence, and all patients exhibited improvement in radiographic measures of patellar tilt and congruence angle, lateral shift ratio, and both Kujala and Lysholm scores.¹⁵¹

While there has yet to be a randomized controlled trial comparing all of these different techniques, there is a general consensus in the literature that patients tend to perform better following MPFL reconstruction vs MPFL repair.

OTHER STABILIZATION PROCEDURES, INCLUDING DISTAL REALIGNMENT

Patients with additional underlying deficits and malalignment issues such as significant trochlear dysplasia, increased TT-TG distance, patella alta, increased Q angle, and/or positive J sign may require stabilization procedures beyond MPFL reconstruction.^152,153 TT osteotomies are often used to correct alignment issues in the adult patient population; however, these procedures are typically contraindicated in skeletally immature patients. Alternative realignment procedures for the pediatric population include both proximal and distal realignment, with proximal realignment performed primarily in children under the age of 12 years.¹⁵³ Many variations on these procedures exist, some of which are no longer regularly performed due to poor reported outcomes. In this article, we discuss several of the techniques, focusing primarily on those that have demonstrated higher success rates.

Continue to: GALEAZZI TECHNIQUE

One of the first and most famous soft-tissue techniques to address patellar instability was the semitendinosus tenodesis, published by Galeazzi¹⁵⁴ in 1922 (Figure 7). This technique stabilizes the patella without altering the TT. In the original technique, a portion of the semitendinosus tendon is harvested with its tibial insertion left intact. The free end of the tendon is then secured with sutures at the periosteal groove of the medial patella.^154,155 Fiume¹⁵⁶ modified this technique by adding a lateral release and medial retinacular reefing. The most recent addition to this procedure was introduced by Baker and colleagues,¹⁵⁷ in which a tunnel is drilled from the medial to the lateral border of the patella. Tension placed on the grafted tendon is used to reposition the patella medially and draw it downward. Preliminary literature on this modified procedure reported fair clinical results with success rates of approximately 75%.^155,158-160 A recent study evaluating both the clinical and radiographic outcomes of this technique also indicated that while clinical results were excellent in 62.5% of patients, this technique alone was unsuccessful in fully addressing patellar instability in patients with underlying anatomic abnormalities such as patellar alta.¹⁶¹ In light of these less than ideal reports, the authors no longer recommend this technique for patellofemoral instability cases.

ROUX-GOLDTHWAIT PROCEDURE

The Roux-Goldthwait procedure, first described by both Roux¹⁶² and Goldthwait¹⁶³ in 1888 and 1895 respectively, was later modified in 1985 to involve a lateral release, plication of the medial retinaculum, medial transfer of the lateral patellar tendon without advancement, and advancement of the vastus medialis (Figure 8).¹⁶⁴ More recently, Marsh and colleagues¹⁵² introduced an addition to aligning the extensor mechanism with the femoral shaft better. In this technique modification, the patellar tendon is split longitudinally, and its lateral half is detached and transferred distally beneath its medial half. The free end is then sutured to the periosteum on the medial side of the tibia.¹⁵² With a mean long-term follow-up of 6.2 years, Marsh and colleagues¹⁵² reported excellent results in 65%, good in 11%, and fair in 3% of the knees operated on with this modified technique. Of the patients in this cohort whose strength was evaluated, 80% had their strength returned to 90% of preoperative levels in the operated leg.¹⁵² While this study and others report improved outcomes, an increasing body of literature has found high rates of recurrence, patella infera, and other complications following the modified Roux-Goldthwait procedure.^36,165-171 Also, a study comparing MPFL reconstruction using adductus magnus transfer with the Roux-Goldthwait procedure reported that patients in the MPFL cohort reported less pain postoperatively.¹⁵⁰ In addition, whereas the Kujala and Lysholm scores, recurrence rates, patellofemoral angles, and apprehension test results did not demonstrate significant differences between these 2 groups, the MPFL group had significantly fewer abnormal congruence angles, better patellar medialization, and higher peak torque of the hamstring.¹⁵⁰

COMBINED MPFL AND MEDIAL PATELLOTIBIAL LIGAMENT RECONSTRUCTION

While the medial patellotibial ligament (MPTL) has not received much attention with regard to patellar stability, recent studies have indicated its role during higher degrees of both flexion and extension.¹⁷² The MPTL acts as a secondary restrictor ligament which helps release stress on the MPFL by decreasing the Q angle and further normalizing patellar kinematics.¹⁷³ Patients who present with hyperlaxity or knee hyperextension combined with extension subluxation and flexion instability could be indicated for this additional stabilizing procedure. Both Nietosvaara and colleagues⁸⁵ and Brown and Ahmad¹⁷⁴ have described a dual MPTL and MPFL reconstruction technique using a semitendinosus hamstring graft. More recently Hinckel and colleagues¹⁷² described a combined MPFL and MPTL reconstruction, using a graft from the quadriceps tendon to reconstruct the MPFL and one from the patellar tendon to reconstruct the MPTL. In this technique, once the respective grafts have been harvested, a femoral insertion for the graft recreating the MPFL is fluoroscopically established so that an anchor can be inserted distal to the femoral physeal growth plate. For the MPTL insertion, attachment to the tibia below the joint line and 2 cm medial to the patellar tendon is established fluoroscopically just above the physeal growth plate on the proximal epiphysis.^19,175 The MPTL graft is sutured first with the knee at 90° of flexion to establish tension similar to that of the patellar tendon.¹⁷⁶ Then, the knee is placed in 30° of flexion to fix the MPFL graft to the medial patella to prevent excessive lateral translation of the patella.

PATELLAR TENDON TRANSFER

Patellar tendon transfer with proximal realignment is a technique used in particularly young patients to address cases of patellofemoral instability involving concomitant bony or anatomic abnormalities. This procedure is effective for young children with substantial amounts of remaining growth as it better mimics native anatomy than other realignment procedures and does not require bony remodeling.^152-154 It is important to familiarize with surgical techniques to address malalignment issues in young patients as neglected alignment issues can lead to worsening of trochlear dysplasia and instability, which are very difficult to treat later on when patients are older.¹⁵³

The patellar tendon transfer technique (Figure 9), as described by Gordon and Schoenecker,¹⁷⁷ starts with an extensive lateral retinacular release. The patellar tendon is then released from its distal insertion at the TT so that it can be moved medially without moving it inferiorly. After confirming patellar tracking and alignment by flexing the knee from 0° to 90° with the graft in place, the patellar tendon graft is secured with multiple nonabsorbable horizontal sutures.¹⁷⁷ Of note, in skeletally mature patients, a TT osteotomy is used to accomplish the same goal. This osteotomy has been shown to improve both patellar height and TT-TG distance in skeletally mature patients, but is contraindicated in skeletally immature patients.^92,178

Continue to: Initial studies conducted on patellar tendon...

Initial studies conducted on patellar tendon transfer have positive outcomes.¹⁷⁹ At a mean follow-up of 5.1 years, patients reported a decrease in pain and increased the ROM and activity, and only 1 reported a postoperative redislocation.¹⁷⁹ In more recent studies, both Benoit and colleagues³⁶ and Garin and colleagues⁵⁸ reviewed cases of patellar instability treated with patellar tendon transfer to address concomitant patellar alignment and anatomic abnormalities. They reported good functional, clinical, and radiographic outcomes with 12.5% and 16% recurrence rates, respectively.^36,58 They also noted radiographic improvements in femoral sulcus angle, particularly in younger patients, which indicate this procedure is effective in addressing bony abnormalities that can result from neglected malalignment issues.^36,58,154

QUADRICEPSPLASTY

Quadricepsplasty is a lengthening and remodeling technique not frequently used in the pediatric population. The goal of this procedure in patients with significant amounts of growth remaining is to reposition the patella to ameliorate trochlear remodeling and prevent worsening symptoms and anatomic abnormalities.³⁶ A quadricepsplasty accomplishes this by de-rotating and/or lengthening the extensor mechanism and may or may not involve a concomitant MPFL reconstruction. This procedure is particularly effective in young patients who experience obligatory dislocation.^60,72 Several quadricepsplasty techniques have been described including Thompson, Curtis and Fisher, Judet, Stanisavljevic, and V-Y technique.^180-186 Most techniques initially involve sharp dissection of the vastus medialis and lateralis from the rectus femoral tendon. A tongue is then fashioned out of the rectus femoral tendon. Once the vastus medialis and lateralis are detached from the margins of the patella, the knee is extended, and the distal ends of the vasti are sutured to the tongue of the rectus tendon. Effective extension facilitates flexion to 90°.¹⁸⁴ The authors recommend a modification of this technique in which a Z lengthening of the quadriceps tendon is performed after the vastus lateralis is removed distally from the patella and the quadriceps tendon.

Several series and case reports evaluating quadricepsplasty in adult patients report positive outcomes with most patients achieving good or excellent flexion with minimal complications.^{183,185,187-189} Reports on quadricepsplasty used to treat conditions other than patellofemoral instability in children have reported similar positive outcomes.^190-192 As quadricepsplasty for patellar instability is relatively rare in pediatric patients, there is not much relevant literature. However, Kocon and colleagues¹⁹³ reported results of quadricepsplasty and quadricepsplasty combined with the modified Galeazzi procedure in 8 children (10 knees) with a mean follow-up of 3.25 years. Seventy percent of cases resulted in stabilization and correction of patellar position, and only 2 postoperative redislocations were noted.¹⁹³ Additionally, in a study evaluating 6 patients suffering from patellar instability, 2 of whom were obligate dislocators, quadricepsplasty resulted in patellar stability, satisfaction, and near normal gait patterns.¹⁹⁴

Figure 10 shows the surgical algorithm used for patellar instability characteristics.

CONCLUSION

Patellofemoral joint stability relies on a complex interplay of musculotendinous units, ligaments and the osteocartilaginous morphology of the patellofemoral joint. Patellar instability in pediatric patients is different from adults. Having an in-depth understanding of the remodeling potential, the insertion sites for the MPFL and its relationship to the physis are of utmost importance when planning surgery. Reducing and maintaining the patella within the patellofemoral joint early enough can allow for remodeling of the patella and/or the trochlea to provide for lasting stability. Appropriate surgical principles, such as tensioning, can help both prevent continued pain and minimize future complications.

ABSTRACT

The reverse shoulder arthroplasty facilitates surgical treatment of primary and revision shoulder with rotator cuff and bone deficiencies. Wear pattern classifications and a logical treatment approach for glenoid bone loss enable the surgeon to address a difficult series of problems in the reconstructions where the glenoid might not otherwise be able to support the implants. Bone grafting using the native humeral head in primary cases, and in revision cases, iliac crest are the most reliable sources for structural grafts for the worn or deficient glenoid vault.

Continue to: The reverse shoulder arthroplasty...

The reverse shoulder arthroplasty (RSA) technique was approved by the US Food and Drug Administration and introduced to the US market in 2004. It has been a successful addition to the treatment of shoulder pathologies with bone and rotator cuff loss. Its indications have expanded from treatment of very elderly patients with rotator cuff deficiencies to now include younger patients with humeral and glenoid bone loss, arthritis, soft-tissue losses, fractures, instability, and revision arthroplasty. Many of these conditions, when not adequately addressed with anatomic arthroplasty, now have viable treatment options for newer complex and successful reconstructions.

Glenoid bone deficiencies offer unique challenges for successful arthroplasty management. Basing treatment on bone loss classifications permits meaningful evaluation of these surgical options and whether they might be carried out in 1- or 2-stage reconstructions. An underlying premise is that restoration of the glenoid joint line and version assist in final stability, power, and functional results. For this purpose, bone graft options, or augmented implants are beneficial. This review covers the bone grafting options for autografts and allografts for deficient glenoids in reverse shoulder arthroplasty reconstructions.

OPERATIVE TECHNIQUES

For patients without prior arthroplasty, the humeral head is available for bone grafting the glenoid bone deficits. Favard and Hamada have described vertical glenoid classifications for uneven glenoid bone loss applicable to cuff tear arthropathy and inflammatory arthritis patients.^1,2 The more severe E3 superior and medial bone loss is ideally addressed with the humeral head. An early example in 2004 confirmed that this was a good indication for glenoid bone grafting and using the reverse shoulder in these advanced cases (Figures 1A-1E).

In this case, it was noted that with bone grafts the base plate post did not engage the native scapula glenoid vault. Given that the on-growth central post was the strongest part of the fixation, it was fortunate that this healed. The need for a longer post with bone grafts was recognized. Laurent Comtat with the Wright Medical company accommodated the author’s request to develop the first 25- and 30-mm-long posts to allow better fixation and on-growth potential when used with bone grafts.

Gilles Walch’s classification addresses arthritic central and horizontal bone loss.^3,4 Considerations relevant in RSA include the severe A2 central bone loss found in inflammatory arthritis and the B2, B3, and C patterns with posterior bone loss seen in osteoarthritis, rheumatoid arthritis, and congenital dysplasia^5,6 as seen in Figures 2A, 2B. The 3-dimensional (3-D) computed tomography (CT) scan is considered the most accurate method of assessment when compared with axial radiographs.⁷ The glenoid vault model as a measurement of glenoid bone loss has great promise in designing prosthetic replacements and bone graft techniques.⁸

Continue to: Modern methods for determining glenoid version...

Modern methods for determining glenoid version, medialization, and eccentric bone wear include 3-D reconstruction and patient-specific instruments. For many years, version determination has been confirmed at surgery with subscapularis elevation, palpating the glenoid center point along Friedman’s line, and then inserting a Steinmann pin as a guide to restore version and the lateral joint line at the time of bone grafting. An example of this is demonstrated in Figures 3A-3E.⁹

All grafts are harvested with a hole saw from the humeral head. The inner diameter is 29 mm, the same as that of the base plate. Originally, the hole saw and mandrel were obtained from the hardware store, but Pascal Boileau upgraded the hole saw quality when he had industry develop a stainless-steel hole saw and published his results with the BIO-RSA (Wright Medical).¹⁰ In an unpublished study, Harmsen reviewed our 220 consecutive humeral head bone grafts for use of this technique with successful and reproducible results. In a separate evaluation, 29 shaped humeral head bone grafts for B2, B3, and C glenoid bone deficits showed 100% healing.¹¹ This technique has good reproducibility when performed with an autogenous bone graft from a local donor source.

The more challenging cases involve glenoid bone loss from polyethylene osteolysis and, in some revision cases, concomitant sepsis.¹² The humeral head is no longer available, and the distal clavicle or humeral metaphysis are often insufficient to restore the glenoid vault and joint line. Gunther and associates at the UC Berkeley biomaterials laboratory have made many contributions to our understanding of polyethylene wear and the factors leading to its loosening that result in massive glenoid bone loss.¹³

Antuna and colleagues¹⁴ classified these cases as having a central vault cavitary defect, or one combined with a peripheral glenoid wall bone loss of either the anterior or posterior glenoid. Newton and colleagues¹⁵ described the structural tricortical iliac crest bone graft as a 2-stage reconstruction. The second stage could be performed 4 to 6 months later after graft incorporation. With the excellent Association for Osteosynthesis (AO) type fixation using the base plate with compression and locking screws, it was reasonable to perform this in 1 stage, assuming that adequate fixation could be obtained with the iliac bone graft to the glenoid.¹⁶ This worked well with the cavitary glenoid defects and those in which either the anterior or posterior wall was absent.^17-19

EXCEPTIONS TO THE 1-STAGE FIXATION TECHNIQUE

Fixation could still be obtained medially, but more severe cases were encountered with loss of both the anterior and posterior walls. In these more advanced cases, the vault was no longer present after removal of the polyethylene, cement, and rubbery osteolytic tissue that replaced the bone. To account for this, a simplified 3-stage classification was proposed.²⁰ The cavitary vault defect is designated as type 1 bone loss. Type 2A includes the cavitary central defect plus loss of the anterior glenoid wall, and 2B is similar with loss of the posterior wall (Figures 4A-4F). Type 3 involves loss of the glenoid vault and both anterior and posterior walls with erosion down to the medial juncture of the base of the scapular spine, coracoid, and pillar of the scapula.

Continue to: The tricortical iliac crest bone graft...

The tricortical iliac crest bone graft (TICBG) offered a structural graft that worked well for these cases of bone loss. When the graft is performed in 1 stage, the glenoid is exposed, and the defect measured after removing the osteolytic, polyethylene-laden tissue from the glenoid. The iliac graft is harvested and placed with the long post base plate engaging the native scapula medially (Figures 5A-5C).

This technique worked well with the type 1 and 2 defects, but when attempted with the type 3 glenoid defect with global glenoid bone loss, adequate fixation for a single-stage reconstruction could not be predictably obtained with type 3 loss of the vault and both walls. In this situation, the base plate post is wider than the remaining medialized glenoid vault (Figures 6A-6C). The iliac crest provides better bone for this global loss when harvested sideways, fixed with screws, and after secure healing, the second-stage base plate is placed (Figures 7A-7F).

An alternative to the iliac crest as a bone graft donor site is the femoral neck allograft.²¹ It avoids the additional surgery and pain at the donor site, but healing is less assured. Scalise and Iannotti²² have had good clinical results but noted substantial graft resorption when revising a total shoulder to a humeral head arthroplasty. In a recent report by Ozgur and colleagues,²³ 64% of femoral neck allografts were still intact at 1-year follow-up. The technique involved harvesting the graft with a hole saw, shaping and affixing it to the deficient glenoid, and gaining central fixation with a threaded or solid post base plate and peripheral screws. Poor results were obtained with the use of the femoral shaft, as it is brittle. Angled peripheral screws caused the allograft shaft to fracture. Low-grade sepsis remained an unanswered problem in the patient group, which averaged 6 prior procedures, and often led to another revision. Less favorable results were found using the 1-piece threaded post base plate with grafts.²⁴ It is assumed that the allograft has less healing potential, and micro motion plays a role when the long central screw has no on-growth healing potential in the native scapula. This graft choice is the author’s least favorite, but is available in desperate situations. Jones and colleagues²⁵ report promising results with bulk allografts and autografts for large glenoid defects with good clinical results. The results in the graft cohort were inferior to those in a matched group not requiring grafts. Their complications were consistent with the revision setting for shoulders having multiple operations. It is well known that preoperative factors are strong predictors of postoperative outcomes.²⁶

CONCLUSION

The author’s current technique is to use the native humeral head when available, or iliac crest for structural support to the base plate and glenosphere. Secure fixation to the native scapula is necessary if the operation is to be done in 1-stage. Incorporation with calcium orthophosphate bone substitution does not replace the need for structural support as shown in Figures 8A-8D.

For the type 2 vault and 1 wall glenoid bone loss defects, the TICBG is still the most useful option. For the type 3 global bone loss defects, a 2-stage approach is the safer option. Additional options that may replace some of these grafting techniques are the introduction of the metallic augmented ingrowth base plates to correct for superior, anterior, and posterior glenoid bone losses. The early unpublished experiences by Wright and colleagues are very promising. All of the above options should be available in the operating room for a busy arthroplasty surgeon.

ABSTRACT

The reverse shoulder arthroplasty facilitates surgical treatment of primary and revision shoulder with rotator cuff and bone deficiencies. Wear pattern classifications and a logical treatment approach for glenoid bone loss enable the surgeon to address a difficult series of problems in the reconstructions where the glenoid might not otherwise be able to support the implants. Bone grafting using the native humeral head in primary cases, and in revision cases, iliac crest are the most reliable sources for structural grafts for the worn or deficient glenoid vault.

Continue to: The reverse shoulder arthroplasty...

The reverse shoulder arthroplasty (RSA) technique was approved by the US Food and Drug Administration and introduced to the US market in 2004. It has been a successful addition to the treatment of shoulder pathologies with bone and rotator cuff loss. Its indications have expanded from treatment of very elderly patients with rotator cuff deficiencies to now include younger patients with humeral and glenoid bone loss, arthritis, soft-tissue losses, fractures, instability, and revision arthroplasty. Many of these conditions, when not adequately addressed with anatomic arthroplasty, now have viable treatment options for newer complex and successful reconstructions.

Glenoid bone deficiencies offer unique challenges for successful arthroplasty management. Basing treatment on bone loss classifications permits meaningful evaluation of these surgical options and whether they might be carried out in 1- or 2-stage reconstructions. An underlying premise is that restoration of the glenoid joint line and version assist in final stability, power, and functional results. For this purpose, bone graft options, or augmented implants are beneficial. This review covers the bone grafting options for autografts and allografts for deficient glenoids in reverse shoulder arthroplasty reconstructions.

OPERATIVE TECHNIQUES

For patients without prior arthroplasty, the humeral head is available for bone grafting the glenoid bone deficits. Favard and Hamada have described vertical glenoid classifications for uneven glenoid bone loss applicable to cuff tear arthropathy and inflammatory arthritis patients.^1,2 The more severe E3 superior and medial bone loss is ideally addressed with the humeral head. An early example in 2004 confirmed that this was a good indication for glenoid bone grafting and using the reverse shoulder in these advanced cases (Figures 1A-1E).

In this case, it was noted that with bone grafts the base plate post did not engage the native scapula glenoid vault. Given that the on-growth central post was the strongest part of the fixation, it was fortunate that this healed. The need for a longer post with bone grafts was recognized. Laurent Comtat with the Wright Medical company accommodated the author’s request to develop the first 25- and 30-mm-long posts to allow better fixation and on-growth potential when used with bone grafts.

Gilles Walch’s classification addresses arthritic central and horizontal bone loss.^3,4 Considerations relevant in RSA include the severe A2 central bone loss found in inflammatory arthritis and the B2, B3, and C patterns with posterior bone loss seen in osteoarthritis, rheumatoid arthritis, and congenital dysplasia^5,6 as seen in Figures 2A, 2B. The 3-dimensional (3-D) computed tomography (CT) scan is considered the most accurate method of assessment when compared with axial radiographs.⁷ The glenoid vault model as a measurement of glenoid bone loss has great promise in designing prosthetic replacements and bone graft techniques.⁸

Continue to: Modern methods for determining glenoid version...

Modern methods for determining glenoid version, medialization, and eccentric bone wear include 3-D reconstruction and patient-specific instruments. For many years, version determination has been confirmed at surgery with subscapularis elevation, palpating the glenoid center point along Friedman’s line, and then inserting a Steinmann pin as a guide to restore version and the lateral joint line at the time of bone grafting. An example of this is demonstrated in Figures 3A-3E.⁹

All grafts are harvested with a hole saw from the humeral head. The inner diameter is 29 mm, the same as that of the base plate. Originally, the hole saw and mandrel were obtained from the hardware store, but Pascal Boileau upgraded the hole saw quality when he had industry develop a stainless-steel hole saw and published his results with the BIO-RSA (Wright Medical).¹⁰ In an unpublished study, Harmsen reviewed our 220 consecutive humeral head bone grafts for use of this technique with successful and reproducible results. In a separate evaluation, 29 shaped humeral head bone grafts for B2, B3, and C glenoid bone deficits showed 100% healing.¹¹ This technique has good reproducibility when performed with an autogenous bone graft from a local donor source.

The more challenging cases involve glenoid bone loss from polyethylene osteolysis and, in some revision cases, concomitant sepsis.¹² The humeral head is no longer available, and the distal clavicle or humeral metaphysis are often insufficient to restore the glenoid vault and joint line. Gunther and associates at the UC Berkeley biomaterials laboratory have made many contributions to our understanding of polyethylene wear and the factors leading to its loosening that result in massive glenoid bone loss.¹³

Antuna and colleagues¹⁴ classified these cases as having a central vault cavitary defect, or one combined with a peripheral glenoid wall bone loss of either the anterior or posterior glenoid. Newton and colleagues¹⁵ described the structural tricortical iliac crest bone graft as a 2-stage reconstruction. The second stage could be performed 4 to 6 months later after graft incorporation. With the excellent Association for Osteosynthesis (AO) type fixation using the base plate with compression and locking screws, it was reasonable to perform this in 1 stage, assuming that adequate fixation could be obtained with the iliac bone graft to the glenoid.¹⁶ This worked well with the cavitary glenoid defects and those in which either the anterior or posterior wall was absent.^17-19

EXCEPTIONS TO THE 1-STAGE FIXATION TECHNIQUE

Fixation could still be obtained medially, but more severe cases were encountered with loss of both the anterior and posterior walls. In these more advanced cases, the vault was no longer present after removal of the polyethylene, cement, and rubbery osteolytic tissue that replaced the bone. To account for this, a simplified 3-stage classification was proposed.²⁰ The cavitary vault defect is designated as type 1 bone loss. Type 2A includes the cavitary central defect plus loss of the anterior glenoid wall, and 2B is similar with loss of the posterior wall (Figures 4A-4F). Type 3 involves loss of the glenoid vault and both anterior and posterior walls with erosion down to the medial juncture of the base of the scapular spine, coracoid, and pillar of the scapula.

Continue to: The tricortical iliac crest bone graft...

The tricortical iliac crest bone graft (TICBG) offered a structural graft that worked well for these cases of bone loss. When the graft is performed in 1 stage, the glenoid is exposed, and the defect measured after removing the osteolytic, polyethylene-laden tissue from the glenoid. The iliac graft is harvested and placed with the long post base plate engaging the native scapula medially (Figures 5A-5C).

This technique worked well with the type 1 and 2 defects, but when attempted with the type 3 glenoid defect with global glenoid bone loss, adequate fixation for a single-stage reconstruction could not be predictably obtained with type 3 loss of the vault and both walls. In this situation, the base plate post is wider than the remaining medialized glenoid vault (Figures 6A-6C). The iliac crest provides better bone for this global loss when harvested sideways, fixed with screws, and after secure healing, the second-stage base plate is placed (Figures 7A-7F).

An alternative to the iliac crest as a bone graft donor site is the femoral neck allograft.²¹ It avoids the additional surgery and pain at the donor site, but healing is less assured. Scalise and Iannotti²² have had good clinical results but noted substantial graft resorption when revising a total shoulder to a humeral head arthroplasty. In a recent report by Ozgur and colleagues,²³ 64% of femoral neck allografts were still intact at 1-year follow-up. The technique involved harvesting the graft with a hole saw, shaping and affixing it to the deficient glenoid, and gaining central fixation with a threaded or solid post base plate and peripheral screws. Poor results were obtained with the use of the femoral shaft, as it is brittle. Angled peripheral screws caused the allograft shaft to fracture. Low-grade sepsis remained an unanswered problem in the patient group, which averaged 6 prior procedures, and often led to another revision. Less favorable results were found using the 1-piece threaded post base plate with grafts.²⁴ It is assumed that the allograft has less healing potential, and micro motion plays a role when the long central screw has no on-growth healing potential in the native scapula. This graft choice is the author’s least favorite, but is available in desperate situations. Jones and colleagues²⁵ report promising results with bulk allografts and autografts for large glenoid defects with good clinical results. The results in the graft cohort were inferior to those in a matched group not requiring grafts. Their complications were consistent with the revision setting for shoulders having multiple operations. It is well known that preoperative factors are strong predictors of postoperative outcomes.²⁶

CONCLUSION

The author’s current technique is to use the native humeral head when available, or iliac crest for structural support to the base plate and glenosphere. Secure fixation to the native scapula is necessary if the operation is to be done in 1-stage. Incorporation with calcium orthophosphate bone substitution does not replace the need for structural support as shown in Figures 8A-8D.

For the type 2 vault and 1 wall glenoid bone loss defects, the TICBG is still the most useful option. For the type 3 global bone loss defects, a 2-stage approach is the safer option. Additional options that may replace some of these grafting techniques are the introduction of the metallic augmented ingrowth base plates to correct for superior, anterior, and posterior glenoid bone losses. The early unpublished experiences by Wright and colleagues are very promising. All of the above options should be available in the operating room for a busy arthroplasty surgeon.

ABSTRACT

The reverse shoulder arthroplasty facilitates surgical treatment of primary and revision shoulder with rotator cuff and bone deficiencies. Wear pattern classifications and a logical treatment approach for glenoid bone loss enable the surgeon to address a difficult series of problems in the reconstructions where the glenoid might not otherwise be able to support the implants. Bone grafting using the native humeral head in primary cases, and in revision cases, iliac crest are the most reliable sources for structural grafts for the worn or deficient glenoid vault.

Continue to: The reverse shoulder arthroplasty...

The reverse shoulder arthroplasty (RSA) technique was approved by the US Food and Drug Administration and introduced to the US market in 2004. It has been a successful addition to the treatment of shoulder pathologies with bone and rotator cuff loss. Its indications have expanded from treatment of very elderly patients with rotator cuff deficiencies to now include younger patients with humeral and glenoid bone loss, arthritis, soft-tissue losses, fractures, instability, and revision arthroplasty. Many of these conditions, when not adequately addressed with anatomic arthroplasty, now have viable treatment options for newer complex and successful reconstructions.

Glenoid bone deficiencies offer unique challenges for successful arthroplasty management. Basing treatment on bone loss classifications permits meaningful evaluation of these surgical options and whether they might be carried out in 1- or 2-stage reconstructions. An underlying premise is that restoration of the glenoid joint line and version assist in final stability, power, and functional results. For this purpose, bone graft options, or augmented implants are beneficial. This review covers the bone grafting options for autografts and allografts for deficient glenoids in reverse shoulder arthroplasty reconstructions.

OPERATIVE TECHNIQUES

For patients without prior arthroplasty, the humeral head is available for bone grafting the glenoid bone deficits. Favard and Hamada have described vertical glenoid classifications for uneven glenoid bone loss applicable to cuff tear arthropathy and inflammatory arthritis patients.^1,2 The more severe E3 superior and medial bone loss is ideally addressed with the humeral head. An early example in 2004 confirmed that this was a good indication for glenoid bone grafting and using the reverse shoulder in these advanced cases (Figures 1A-1E).

In this case, it was noted that with bone grafts the base plate post did not engage the native scapula glenoid vault. Given that the on-growth central post was the strongest part of the fixation, it was fortunate that this healed. The need for a longer post with bone grafts was recognized. Laurent Comtat with the Wright Medical company accommodated the author’s request to develop the first 25- and 30-mm-long posts to allow better fixation and on-growth potential when used with bone grafts.

Gilles Walch’s classification addresses arthritic central and horizontal bone loss.^3,4 Considerations relevant in RSA include the severe A2 central bone loss found in inflammatory arthritis and the B2, B3, and C patterns with posterior bone loss seen in osteoarthritis, rheumatoid arthritis, and congenital dysplasia^5,6 as seen in Figures 2A, 2B. The 3-dimensional (3-D) computed tomography (CT) scan is considered the most accurate method of assessment when compared with axial radiographs.⁷ The glenoid vault model as a measurement of glenoid bone loss has great promise in designing prosthetic replacements and bone graft techniques.⁸

Continue to: Modern methods for determining glenoid version...

Modern methods for determining glenoid version, medialization, and eccentric bone wear include 3-D reconstruction and patient-specific instruments. For many years, version determination has been confirmed at surgery with subscapularis elevation, palpating the glenoid center point along Friedman’s line, and then inserting a Steinmann pin as a guide to restore version and the lateral joint line at the time of bone grafting. An example of this is demonstrated in Figures 3A-3E.⁹

All grafts are harvested with a hole saw from the humeral head. The inner diameter is 29 mm, the same as that of the base plate. Originally, the hole saw and mandrel were obtained from the hardware store, but Pascal Boileau upgraded the hole saw quality when he had industry develop a stainless-steel hole saw and published his results with the BIO-RSA (Wright Medical).¹⁰ In an unpublished study, Harmsen reviewed our 220 consecutive humeral head bone grafts for use of this technique with successful and reproducible results. In a separate evaluation, 29 shaped humeral head bone grafts for B2, B3, and C glenoid bone deficits showed 100% healing.¹¹ This technique has good reproducibility when performed with an autogenous bone graft from a local donor source.

The more challenging cases involve glenoid bone loss from polyethylene osteolysis and, in some revision cases, concomitant sepsis.¹² The humeral head is no longer available, and the distal clavicle or humeral metaphysis are often insufficient to restore the glenoid vault and joint line. Gunther and associates at the UC Berkeley biomaterials laboratory have made many contributions to our understanding of polyethylene wear and the factors leading to its loosening that result in massive glenoid bone loss.¹³

Antuna and colleagues¹⁴ classified these cases as having a central vault cavitary defect, or one combined with a peripheral glenoid wall bone loss of either the anterior or posterior glenoid. Newton and colleagues¹⁵ described the structural tricortical iliac crest bone graft as a 2-stage reconstruction. The second stage could be performed 4 to 6 months later after graft incorporation. With the excellent Association for Osteosynthesis (AO) type fixation using the base plate with compression and locking screws, it was reasonable to perform this in 1 stage, assuming that adequate fixation could be obtained with the iliac bone graft to the glenoid.¹⁶ This worked well with the cavitary glenoid defects and those in which either the anterior or posterior wall was absent.^17-19

EXCEPTIONS TO THE 1-STAGE FIXATION TECHNIQUE

Fixation could still be obtained medially, but more severe cases were encountered with loss of both the anterior and posterior walls. In these more advanced cases, the vault was no longer present after removal of the polyethylene, cement, and rubbery osteolytic tissue that replaced the bone. To account for this, a simplified 3-stage classification was proposed.²⁰ The cavitary vault defect is designated as type 1 bone loss. Type 2A includes the cavitary central defect plus loss of the anterior glenoid wall, and 2B is similar with loss of the posterior wall (Figures 4A-4F). Type 3 involves loss of the glenoid vault and both anterior and posterior walls with erosion down to the medial juncture of the base of the scapular spine, coracoid, and pillar of the scapula.

Continue to: The tricortical iliac crest bone graft...

The tricortical iliac crest bone graft (TICBG) offered a structural graft that worked well for these cases of bone loss. When the graft is performed in 1 stage, the glenoid is exposed, and the defect measured after removing the osteolytic, polyethylene-laden tissue from the glenoid. The iliac graft is harvested and placed with the long post base plate engaging the native scapula medially (Figures 5A-5C).

This technique worked well with the type 1 and 2 defects, but when attempted with the type 3 glenoid defect with global glenoid bone loss, adequate fixation for a single-stage reconstruction could not be predictably obtained with type 3 loss of the vault and both walls. In this situation, the base plate post is wider than the remaining medialized glenoid vault (Figures 6A-6C). The iliac crest provides better bone for this global loss when harvested sideways, fixed with screws, and after secure healing, the second-stage base plate is placed (Figures 7A-7F).

An alternative to the iliac crest as a bone graft donor site is the femoral neck allograft.²¹ It avoids the additional surgery and pain at the donor site, but healing is less assured. Scalise and Iannotti²² have had good clinical results but noted substantial graft resorption when revising a total shoulder to a humeral head arthroplasty. In a recent report by Ozgur and colleagues,²³ 64% of femoral neck allografts were still intact at 1-year follow-up. The technique involved harvesting the graft with a hole saw, shaping and affixing it to the deficient glenoid, and gaining central fixation with a threaded or solid post base plate and peripheral screws. Poor results were obtained with the use of the femoral shaft, as it is brittle. Angled peripheral screws caused the allograft shaft to fracture. Low-grade sepsis remained an unanswered problem in the patient group, which averaged 6 prior procedures, and often led to another revision. Less favorable results were found using the 1-piece threaded post base plate with grafts.²⁴ It is assumed that the allograft has less healing potential, and micro motion plays a role when the long central screw has no on-growth healing potential in the native scapula. This graft choice is the author’s least favorite, but is available in desperate situations. Jones and colleagues²⁵ report promising results with bulk allografts and autografts for large glenoid defects with good clinical results. The results in the graft cohort were inferior to those in a matched group not requiring grafts. Their complications were consistent with the revision setting for shoulders having multiple operations. It is well known that preoperative factors are strong predictors of postoperative outcomes.²⁶

CONCLUSION

The author’s current technique is to use the native humeral head when available, or iliac crest for structural support to the base plate and glenosphere. Secure fixation to the native scapula is necessary if the operation is to be done in 1-stage. Incorporation with calcium orthophosphate bone substitution does not replace the need for structural support as shown in Figures 8A-8D.

For the type 2 vault and 1 wall glenoid bone loss defects, the TICBG is still the most useful option. For the type 3 global bone loss defects, a 2-stage approach is the safer option. Additional options that may replace some of these grafting techniques are the introduction of the metallic augmented ingrowth base plates to correct for superior, anterior, and posterior glenoid bone losses. The early unpublished experiences by Wright and colleagues are very promising. All of the above options should be available in the operating room for a busy arthroplasty surgeon.

Patients with the most severe cases of rheumatoid arthritis are more likely to suffer flares after knee or hip replacement surgery, a new study finds, and it doesn’t seem to matter whether they stop taking biologics before their operation.

“We found that the majority of patients had active disease at the time of surgery, contrary to prior statements that RA patients have inactive disease at the time they go for hip or knee replacement. In fact, the majority – 65% of the patients – reported a flare of RA within 6 weeks of surgery,” lead author Susan M. Goodman, MD, of Cornell University and the Hospital for Special Surgery, New York, said in an interview. “Surprisingly, although more of the flaring patients were taking potent biologics that had been withheld preoperatively, the major risk factor for flares was their baseline disease activity.”

[email protected]

SOURCE: Goodman S et al. J Rheumatol. 2018 Mar 15. doi: 10.3899/jrheum.170366

Patients with the most severe cases of rheumatoid arthritis are more likely to suffer flares after knee or hip replacement surgery, a new study finds, and it doesn’t seem to matter whether they stop taking biologics before their operation.

“We found that the majority of patients had active disease at the time of surgery, contrary to prior statements that RA patients have inactive disease at the time they go for hip or knee replacement. In fact, the majority – 65% of the patients – reported a flare of RA within 6 weeks of surgery,” lead author Susan M. Goodman, MD, of Cornell University and the Hospital for Special Surgery, New York, said in an interview. “Surprisingly, although more of the flaring patients were taking potent biologics that had been withheld preoperatively, the major risk factor for flares was their baseline disease activity.”

[email protected]

SOURCE: Goodman S et al. J Rheumatol. 2018 Mar 15. doi: 10.3899/jrheum.170366

Patients with the most severe cases of rheumatoid arthritis are more likely to suffer flares after knee or hip replacement surgery, a new study finds, and it doesn’t seem to matter whether they stop taking biologics before their operation.

“We found that the majority of patients had active disease at the time of surgery, contrary to prior statements that RA patients have inactive disease at the time they go for hip or knee replacement. In fact, the majority – 65% of the patients – reported a flare of RA within 6 weeks of surgery,” lead author Susan M. Goodman, MD, of Cornell University and the Hospital for Special Surgery, New York, said in an interview. “Surprisingly, although more of the flaring patients were taking potent biologics that had been withheld preoperatively, the major risk factor for flares was their baseline disease activity.”

[email protected]

SOURCE: Goodman S et al. J Rheumatol. 2018 Mar 15. doi: 10.3899/jrheum.170366

ABSTRACT

The h-index is a commonly utilized metric for academic productivity. Previous studies have proposed that self-citation may limit the utility of the h-index. The purpose of this study is to evaluate the impact of self-citation on the h-index among orthopedic investigators. The study cohort consisted of program directors, chairpersons, and faculty at orthopedic surgery residency programs in the United States. The Scopus database was used to determine the h-index and number of citations ± self-citations. The total number of publications was correlated with the change in the h-index via self-citation. A total of 463 researchers were included (198 National Institutes of Health-funded faculty, 147 chairpersons, 118 program directors). Of these researchers, 83.8% cited previous work at least once (mean, 123.9 ± 277.6). Self-citations accounted for 5.8% of all citations. Including these citations increased the author h-index from 18.5 ± 14.9 to 19.2 ± 15.6 (P < .001). A minority of researchers (36.3%, P < .001) had increased their h-index via self-citation (range, 0-11). The proportional increase in the h-index via self-citation was positively related to the number of publications (P < .001). While the practice of self-citation is prevalent in orthopedics, its impact on the h-index is minimal for most researchers. With more publications, researchers can increase their h-index to a greater degree via self-citation.

Continue to: The competitive nature of academic research...

The competitive nature of academic research requires objective metrics to define career end points, such as promotion and funding procurement. While various criteria are used to assess performance in academia, publications and research funding are particularly regarded.¹ Quantifying research dollars is relatively straightforward, but measuring research productivity is more complex. Not all articles are created equal, and disparities exist regarding effort and the ultimate impact of articles. In 2005, a physicist created the h-index to measure both research impact and productivity.² As a bibliometric, the h-index equals the number of publications h that have been cited at least h times. Given its simplicity, the h-index has gained wide popularity in diverse medical specialties, including orthopedic surgery.³ Other recent studies have applied the h-index to hand surgery and spine surgery.^4,5

Importantly, some authors have raised concerns regarding potential limitations of the h-index. One potentially significant limitation is the ability of authors to artificially inflate their h-index via self-citation. The impact of this practice is of particular interest as the h-index becomes widely adopted as a metric for promotion at many academic institutions.^6-7 Furthermore, scholarly productivity has remained a critical component of successful grant funding procurement, and future grant funding applications may evaluate the h-index.^8-10

The purpose of this study is to determine the prevalence and impact of self-citation on the h-index in a large cohort of orthopedic investigators. Given their high level of investment in academic orthopedic surgery, we focused on program directors, chairpersons, and National Institutes of Health (NIH)-funded research faculty at orthopedic surgery residency programs.

METHODS

INCLUSION CRITERIA

This study qualified as non-human and non-animal research and received exemption per the standing policy of the Institutional Review Board. The Fellowship and Residency Electronic Interactive Database (FREIDA) was accessed to generate a list of orthopedic residency program directors.¹¹ This database was also used to generate a list of allopathic orthopedic surgery residency programs. Official program websites were accessed to generate a list of orthopedic chairpersons. Lastly, the NIH RePORTER was used to generate a list of basic science orthopedic investigators who received funding anytime during 2011 to 2014.¹² This methodology was used due to the lack of reporting of basic science investigators on program websites. A list of NIH-funded orthopedic investigators was cross-referenced via an online search to isolate a cohort of PhD investigators.

Orthopedic faculty were defined as chairpersons, program directors, or NIH-funded investigators. In cases of overlap, preference was given in that order. Orthopedic investigators who had not published an article after 1995 were excluded (6 chairpersons, 1 program director).

BIBLIOMETRIC ANALYSIS

While several resources exist to calculate the h-index, the Scopus database (Elsevier) is one of the easiest programs to use.¹³ Author entries are created via institutional affiliations, thereby alleviating the need for manual reconciliations. Investigators were identified on Scopus via “author last name” and “first name, middle initial.” For each author, publications were screened for relevance to the field of orthopedics. Affiliated institutions were cross-referenced with information obtained from individual program websites. The “view h-graph” feature was used to calculate the number of publications, h-index, and number of citations. Then, the “Exclude self-citations” feature was used to calculate the number of corrected citations and the h-index excluding self-citations. Metrics were calculated over a 2-day period.

Continue to: STATISTICAL ANALYSIS

Bibliometric analyses were presented descriptively with means ± standard deviation. After testing for normality, differences in the h-index between groups were assessed via analysis of variance tests. The proportional increase in the number of citations and the h-index were calculated by dividing the difference between the before and after exclusion of self-citations by the total number of citations before exclusion. The relationship between the number of publications and the proportional change in the h-index was assessed via calculation of the Spearman correlation coefficient. The independent variable was the number of publications, and the proportional increase in the h-index via self-citation was the dependent variable. Statistical tests were performed on STATA 13 (StataCorp) and the results considered significant if P < .05. Figures were created using GraphPad Prism 6.02 Software.

RESULTS

A total of 463 orthopedic investigators were included (147 chairpersons, 118 program directors, and 198 NIH-funded faculty) (Table 1). On average, these researchers produced 72.3 ± 83.0 articles and referenced 2139 ± 3222 articles (mean, 29.6 references per article). The cumulative h-index was 19.2 ± 15.6, and was the highest among NIH-funded researchers (24.3 ± 17.0) (P < .001). In all, 83.8% of orthopedic investigators self-cited their previous work at least once, and the total number of self-citations was highest among NIH-funded investigators (221 ± 355) (P < .001). After these self-citations were excluded, the h-index changed by 0.6 ± 1.1 for all investigators, and this change was greatest among NIH-funded researchers (1.1 ± 1.3) (P < .001).

Table 1. Effect of Self-Citation on NIH-funded Investigators, Chairpersons, and Program Directors in Orthopedics

Abbreviation: NIH, National Institutes of Health.

Most orthopedic investigators did not increase their h-index via self-citation (63.7%, P < .001). Table 2 categorizes investigators by changes in their h-index after excluding self-citations (range, 0-11). The maximal change in the h-index was seen in the most prolific group of investigators, who produced 261.0 ± 149.3 articles. In this group, the h-index increased by 11.1% ± 5.2%. The Figure investigates the relationship between the number of articles and the proportional increase in the h-index. The number of publications was positively correlated with the change in h-index after self-citations were excluded (r = 0.448, P < .001).

Table 2. Stratification of Orthopedic Researcher Investigators by Change in h-index After Self-Citation

DISCUSSION

The practice of self-citation is widely prevalent among experienced orthopedic investigators. However, this practice seems to have minimal impact on the h-index for most investigators. Self-citation had a measurable impact on the h-index only after an investigator had many publications. At a mean of 87.9 ± 68.3 articles, investigators had a ∆h-index of 1. This represented a mean 5.9% increase. Overall, these findings underscore the utility of the h-index in assessing scholarly impact and ameliorate concerns over bibliometric manipulation.

Among a large group of experienced orthopedic investigators, self-citation has minimal effect on the h-index. Importantly, most investigators (63.7%) did not experience a full integer increase in their h-index. At a threshold of ∆ h-index increase of 1, investigators had impressive h-indices (24.0 ± 13.3), which eclipsed those of recent studies of hand surgeons (10.2 ± 9.9) and spine surgeons (13.6 ± 8.7).^4,5 This finding suggests that committees for academic promotion in orthopedic surgery may disregard the impact of self-citation on the h-index. While the thresholds for promotion have not been defined in the orthopedic literature, a study in plastic surgery established an h-index threshold of 14.5 for promotion from associate to full professor.¹⁴ It may be, however, that h-indices are higher among orthopedic surgeons, as a previous study reported an h-index of 20 among full professors.¹⁵ Future research is needed to determine thresholds for promotion within orthopedic surgery, as the h-index varies by specialty according to unique citation patterns.

Continue to: It is worth highlighting...

It is worth highlighting the academic performance of NIH-funded PhD researchers in orthopedics. Even including training grant awardees in this group, this cohort exceeded the academic productivity of their orthopedic chairpersons, as measured by the h-index. Previous studies in urology, neurosurgery, and otolaryngology have demonstrated the impact of NIH-funding on academic productivity.^8-10 Ultimately, orthopedic departments could increase academic productivity by recruiting more PhD investigators with NIH funding.

In contrast to academic radiology,¹⁶ this study demonstrated a correlation between the number of publications and the increase in h-index via self-citation. Several reasons may help explain this disparity. The first reason is a technical one, as at the time of this study, the Scopus database had been updated to include citations before 1996. Considering that the h-index increases over time as older publications are cited, the exclusion of older articles is a significant limitation of previous h-index studies. Applying the same logic, the mean h-index for chairpersons of 19.9 quoted in this study contradicts a recent study, which quoted a mean h-index of 15.3.³ This previous study utilized citations that were limited to articles published after 1996.

Previous work on self-citation in the field of orthopedics has been limited to its influence on journal impact factors. Our results build on this literature in several important ways. Firstly, the calculation of a journal’s impact factor is a highly scrutinized process, and authors have criticized the mechanisms employed by editors to inflate impact factors.¹⁷ One study reported that 20% of authors have been encouraged to cite a journal during the revision process.¹⁸ Self-citation practices have been demonstrated in journals of cardiology,¹⁹ diabetes,²⁰ anesthesia,²¹ and medicine.²² A study using a hypothetical model to assess the maximum potential for h-index increase by self-citation demonstrated an h-index inflation of 5 points over 20 years (5/14, 35.7%) by publishing 3 papers per year with 3 self-citations each.²³ This study highlights a potential limitation of the h-index, but our study observed an h-index inflation of ≥4 in only 11 researchers (2.4%). Thus, results from our study ameliorate self-citation concerns in academic orthopedic surgery.

There are several limitations to this study that offer future areas of research. First, the validity of the h-index academic promotion in orthopedic surgery has not been evaluated. This was a motivation for the present study, and the authors have ongoing efforts to characterize the h-index in a larger cohort of orthopedic investigators. Importantly, an appropriate amount of self-citation was not established. It may be necessary for orthopedic researchers to cite their works as they become experts on a specific topic. Lastly, our analyses are prone to limitations inherent in the h-index, which does not account for author contribution or journal impact factors. Despite these limitations, we show that for most orthopedic researchers, the practice of self-citation does not impact the h-index.

In summary, self-citation is a widely prevalent practice among orthopedic investigators, but this practice has minimal impact on an author’s h-index. Approximately one third of orthopedic faculty in our study had a higher h-index due to self-citation. Greater h-index inflation through self-citation correlated with more publications. For the majority of orthopedic faculty, however, self-citation did not inflate the h-index, suggesting that promotional committees may disregard this concern when using the h-index as an adjunct measure for career advancement.

ABSTRACT

The h-index is a commonly utilized metric for academic productivity. Previous studies have proposed that self-citation may limit the utility of the h-index. The purpose of this study is to evaluate the impact of self-citation on the h-index among orthopedic investigators. The study cohort consisted of program directors, chairpersons, and faculty at orthopedic surgery residency programs in the United States. The Scopus database was used to determine the h-index and number of citations ± self-citations. The total number of publications was correlated with the change in the h-index via self-citation. A total of 463 researchers were included (198 National Institutes of Health-funded faculty, 147 chairpersons, 118 program directors). Of these researchers, 83.8% cited previous work at least once (mean, 123.9 ± 277.6). Self-citations accounted for 5.8% of all citations. Including these citations increased the author h-index from 18.5 ± 14.9 to 19.2 ± 15.6 (P < .001). A minority of researchers (36.3%, P < .001) had increased their h-index via self-citation (range, 0-11). The proportional increase in the h-index via self-citation was positively related to the number of publications (P < .001). While the practice of self-citation is prevalent in orthopedics, its impact on the h-index is minimal for most researchers. With more publications, researchers can increase their h-index to a greater degree via self-citation.

Continue to: The competitive nature of academic research...

The competitive nature of academic research requires objective metrics to define career end points, such as promotion and funding procurement. While various criteria are used to assess performance in academia, publications and research funding are particularly regarded.¹ Quantifying research dollars is relatively straightforward, but measuring research productivity is more complex. Not all articles are created equal, and disparities exist regarding effort and the ultimate impact of articles. In 2005, a physicist created the h-index to measure both research impact and productivity.² As a bibliometric, the h-index equals the number of publications h that have been cited at least h times. Given its simplicity, the h-index has gained wide popularity in diverse medical specialties, including orthopedic surgery.³ Other recent studies have applied the h-index to hand surgery and spine surgery.^4,5

Importantly, some authors have raised concerns regarding potential limitations of the h-index. One potentially significant limitation is the ability of authors to artificially inflate their h-index via self-citation. The impact of this practice is of particular interest as the h-index becomes widely adopted as a metric for promotion at many academic institutions.^6-7 Furthermore, scholarly productivity has remained a critical component of successful grant funding procurement, and future grant funding applications may evaluate the h-index.^8-10

The purpose of this study is to determine the prevalence and impact of self-citation on the h-index in a large cohort of orthopedic investigators. Given their high level of investment in academic orthopedic surgery, we focused on program directors, chairpersons, and National Institutes of Health (NIH)-funded research faculty at orthopedic surgery residency programs.

METHODS

INCLUSION CRITERIA

This study qualified as non-human and non-animal research and received exemption per the standing policy of the Institutional Review Board. The Fellowship and Residency Electronic Interactive Database (FREIDA) was accessed to generate a list of orthopedic residency program directors.¹¹ This database was also used to generate a list of allopathic orthopedic surgery residency programs. Official program websites were accessed to generate a list of orthopedic chairpersons. Lastly, the NIH RePORTER was used to generate a list of basic science orthopedic investigators who received funding anytime during 2011 to 2014.¹² This methodology was used due to the lack of reporting of basic science investigators on program websites. A list of NIH-funded orthopedic investigators was cross-referenced via an online search to isolate a cohort of PhD investigators.

Orthopedic faculty were defined as chairpersons, program directors, or NIH-funded investigators. In cases of overlap, preference was given in that order. Orthopedic investigators who had not published an article after 1995 were excluded (6 chairpersons, 1 program director).

BIBLIOMETRIC ANALYSIS

While several resources exist to calculate the h-index, the Scopus database (Elsevier) is one of the easiest programs to use.¹³ Author entries are created via institutional affiliations, thereby alleviating the need for manual reconciliations. Investigators were identified on Scopus via “author last name” and “first name, middle initial.” For each author, publications were screened for relevance to the field of orthopedics. Affiliated institutions were cross-referenced with information obtained from individual program websites. The “view h-graph” feature was used to calculate the number of publications, h-index, and number of citations. Then, the “Exclude self-citations” feature was used to calculate the number of corrected citations and the h-index excluding self-citations. Metrics were calculated over a 2-day period.

Continue to: STATISTICAL ANALYSIS

Bibliometric analyses were presented descriptively with means ± standard deviation. After testing for normality, differences in the h-index between groups were assessed via analysis of variance tests. The proportional increase in the number of citations and the h-index were calculated by dividing the difference between the before and after exclusion of self-citations by the total number of citations before exclusion. The relationship between the number of publications and the proportional change in the h-index was assessed via calculation of the Spearman correlation coefficient. The independent variable was the number of publications, and the proportional increase in the h-index via self-citation was the dependent variable. Statistical tests were performed on STATA 13 (StataCorp) and the results considered significant if P < .05. Figures were created using GraphPad Prism 6.02 Software.

RESULTS

A total of 463 orthopedic investigators were included (147 chairpersons, 118 program directors, and 198 NIH-funded faculty) (Table 1). On average, these researchers produced 72.3 ± 83.0 articles and referenced 2139 ± 3222 articles (mean, 29.6 references per article). The cumulative h-index was 19.2 ± 15.6, and was the highest among NIH-funded researchers (24.3 ± 17.0) (P < .001). In all, 83.8% of orthopedic investigators self-cited their previous work at least once, and the total number of self-citations was highest among NIH-funded investigators (221 ± 355) (P < .001). After these self-citations were excluded, the h-index changed by 0.6 ± 1.1 for all investigators, and this change was greatest among NIH-funded researchers (1.1 ± 1.3) (P < .001).

Table 1. Effect of Self-Citation on NIH-funded Investigators, Chairpersons, and Program Directors in Orthopedics

Abbreviation: NIH, National Institutes of Health.

Most orthopedic investigators did not increase their h-index via self-citation (63.7%, P < .001). Table 2 categorizes investigators by changes in their h-index after excluding self-citations (range, 0-11). The maximal change in the h-index was seen in the most prolific group of investigators, who produced 261.0 ± 149.3 articles. In this group, the h-index increased by 11.1% ± 5.2%. The Figure investigates the relationship between the number of articles and the proportional increase in the h-index. The number of publications was positively correlated with the change in h-index after self-citations were excluded (r = 0.448, P < .001).

Table 2. Stratification of Orthopedic Researcher Investigators by Change in h-index After Self-Citation

DISCUSSION

The practice of self-citation is widely prevalent among experienced orthopedic investigators. However, this practice seems to have minimal impact on the h-index for most investigators. Self-citation had a measurable impact on the h-index only after an investigator had many publications. At a mean of 87.9 ± 68.3 articles, investigators had a ∆h-index of 1. This represented a mean 5.9% increase. Overall, these findings underscore the utility of the h-index in assessing scholarly impact and ameliorate concerns over bibliometric manipulation.

Among a large group of experienced orthopedic investigators, self-citation has minimal effect on the h-index. Importantly, most investigators (63.7%) did not experience a full integer increase in their h-index. At a threshold of ∆ h-index increase of 1, investigators had impressive h-indices (24.0 ± 13.3), which eclipsed those of recent studies of hand surgeons (10.2 ± 9.9) and spine surgeons (13.6 ± 8.7).^4,5 This finding suggests that committees for academic promotion in orthopedic surgery may disregard the impact of self-citation on the h-index. While the thresholds for promotion have not been defined in the orthopedic literature, a study in plastic surgery established an h-index threshold of 14.5 for promotion from associate to full professor.¹⁴ It may be, however, that h-indices are higher among orthopedic surgeons, as a previous study reported an h-index of 20 among full professors.¹⁵ Future research is needed to determine thresholds for promotion within orthopedic surgery, as the h-index varies by specialty according to unique citation patterns.

Continue to: It is worth highlighting...

It is worth highlighting the academic performance of NIH-funded PhD researchers in orthopedics. Even including training grant awardees in this group, this cohort exceeded the academic productivity of their orthopedic chairpersons, as measured by the h-index. Previous studies in urology, neurosurgery, and otolaryngology have demonstrated the impact of NIH-funding on academic productivity.^8-10 Ultimately, orthopedic departments could increase academic productivity by recruiting more PhD investigators with NIH funding.

In contrast to academic radiology,¹⁶ this study demonstrated a correlation between the number of publications and the increase in h-index via self-citation. Several reasons may help explain this disparity. The first reason is a technical one, as at the time of this study, the Scopus database had been updated to include citations before 1996. Considering that the h-index increases over time as older publications are cited, the exclusion of older articles is a significant limitation of previous h-index studies. Applying the same logic, the mean h-index for chairpersons of 19.9 quoted in this study contradicts a recent study, which quoted a mean h-index of 15.3.³ This previous study utilized citations that were limited to articles published after 1996.

Previous work on self-citation in the field of orthopedics has been limited to its influence on journal impact factors. Our results build on this literature in several important ways. Firstly, the calculation of a journal’s impact factor is a highly scrutinized process, and authors have criticized the mechanisms employed by editors to inflate impact factors.¹⁷ One study reported that 20% of authors have been encouraged to cite a journal during the revision process.¹⁸ Self-citation practices have been demonstrated in journals of cardiology,¹⁹ diabetes,²⁰ anesthesia,²¹ and medicine.²² A study using a hypothetical model to assess the maximum potential for h-index increase by self-citation demonstrated an h-index inflation of 5 points over 20 years (5/14, 35.7%) by publishing 3 papers per year with 3 self-citations each.²³ This study highlights a potential limitation of the h-index, but our study observed an h-index inflation of ≥4 in only 11 researchers (2.4%). Thus, results from our study ameliorate self-citation concerns in academic orthopedic surgery.

There are several limitations to this study that offer future areas of research. First, the validity of the h-index academic promotion in orthopedic surgery has not been evaluated. This was a motivation for the present study, and the authors have ongoing efforts to characterize the h-index in a larger cohort of orthopedic investigators. Importantly, an appropriate amount of self-citation was not established. It may be necessary for orthopedic researchers to cite their works as they become experts on a specific topic. Lastly, our analyses are prone to limitations inherent in the h-index, which does not account for author contribution or journal impact factors. Despite these limitations, we show that for most orthopedic researchers, the practice of self-citation does not impact the h-index.

In summary, self-citation is a widely prevalent practice among orthopedic investigators, but this practice has minimal impact on an author’s h-index. Approximately one third of orthopedic faculty in our study had a higher h-index due to self-citation. Greater h-index inflation through self-citation correlated with more publications. For the majority of orthopedic faculty, however, self-citation did not inflate the h-index, suggesting that promotional committees may disregard this concern when using the h-index as an adjunct measure for career advancement.

ABSTRACT

The h-index is a commonly utilized metric for academic productivity. Previous studies have proposed that self-citation may limit the utility of the h-index. The purpose of this study is to evaluate the impact of self-citation on the h-index among orthopedic investigators. The study cohort consisted of program directors, chairpersons, and faculty at orthopedic surgery residency programs in the United States. The Scopus database was used to determine the h-index and number of citations ± self-citations. The total number of publications was correlated with the change in the h-index via self-citation. A total of 463 researchers were included (198 National Institutes of Health-funded faculty, 147 chairpersons, 118 program directors). Of these researchers, 83.8% cited previous work at least once (mean, 123.9 ± 277.6). Self-citations accounted for 5.8% of all citations. Including these citations increased the author h-index from 18.5 ± 14.9 to 19.2 ± 15.6 (P < .001). A minority of researchers (36.3%, P < .001) had increased their h-index via self-citation (range, 0-11). The proportional increase in the h-index via self-citation was positively related to the number of publications (P < .001). While the practice of self-citation is prevalent in orthopedics, its impact on the h-index is minimal for most researchers. With more publications, researchers can increase their h-index to a greater degree via self-citation.

Continue to: The competitive nature of academic research...

The competitive nature of academic research requires objective metrics to define career end points, such as promotion and funding procurement. While various criteria are used to assess performance in academia, publications and research funding are particularly regarded.¹ Quantifying research dollars is relatively straightforward, but measuring research productivity is more complex. Not all articles are created equal, and disparities exist regarding effort and the ultimate impact of articles. In 2005, a physicist created the h-index to measure both research impact and productivity.² As a bibliometric, the h-index equals the number of publications h that have been cited at least h times. Given its simplicity, the h-index has gained wide popularity in diverse medical specialties, including orthopedic surgery.³ Other recent studies have applied the h-index to hand surgery and spine surgery.^4,5

Importantly, some authors have raised concerns regarding potential limitations of the h-index. One potentially significant limitation is the ability of authors to artificially inflate their h-index via self-citation. The impact of this practice is of particular interest as the h-index becomes widely adopted as a metric for promotion at many academic institutions.^6-7 Furthermore, scholarly productivity has remained a critical component of successful grant funding procurement, and future grant funding applications may evaluate the h-index.^8-10

The purpose of this study is to determine the prevalence and impact of self-citation on the h-index in a large cohort of orthopedic investigators. Given their high level of investment in academic orthopedic surgery, we focused on program directors, chairpersons, and National Institutes of Health (NIH)-funded research faculty at orthopedic surgery residency programs.

METHODS

INCLUSION CRITERIA

This study qualified as non-human and non-animal research and received exemption per the standing policy of the Institutional Review Board. The Fellowship and Residency Electronic Interactive Database (FREIDA) was accessed to generate a list of orthopedic residency program directors.¹¹ This database was also used to generate a list of allopathic orthopedic surgery residency programs. Official program websites were accessed to generate a list of orthopedic chairpersons. Lastly, the NIH RePORTER was used to generate a list of basic science orthopedic investigators who received funding anytime during 2011 to 2014.¹² This methodology was used due to the lack of reporting of basic science investigators on program websites. A list of NIH-funded orthopedic investigators was cross-referenced via an online search to isolate a cohort of PhD investigators.

Orthopedic faculty were defined as chairpersons, program directors, or NIH-funded investigators. In cases of overlap, preference was given in that order. Orthopedic investigators who had not published an article after 1995 were excluded (6 chairpersons, 1 program director).

BIBLIOMETRIC ANALYSIS

While several resources exist to calculate the h-index, the Scopus database (Elsevier) is one of the easiest programs to use.¹³ Author entries are created via institutional affiliations, thereby alleviating the need for manual reconciliations. Investigators were identified on Scopus via “author last name” and “first name, middle initial.” For each author, publications were screened for relevance to the field of orthopedics. Affiliated institutions were cross-referenced with information obtained from individual program websites. The “view h-graph” feature was used to calculate the number of publications, h-index, and number of citations. Then, the “Exclude self-citations” feature was used to calculate the number of corrected citations and the h-index excluding self-citations. Metrics were calculated over a 2-day period.

Continue to: STATISTICAL ANALYSIS

Bibliometric analyses were presented descriptively with means ± standard deviation. After testing for normality, differences in the h-index between groups were assessed via analysis of variance tests. The proportional increase in the number of citations and the h-index were calculated by dividing the difference between the before and after exclusion of self-citations by the total number of citations before exclusion. The relationship between the number of publications and the proportional change in the h-index was assessed via calculation of the Spearman correlation coefficient. The independent variable was the number of publications, and the proportional increase in the h-index via self-citation was the dependent variable. Statistical tests were performed on STATA 13 (StataCorp) and the results considered significant if P < .05. Figures were created using GraphPad Prism 6.02 Software.

RESULTS

A total of 463 orthopedic investigators were included (147 chairpersons, 118 program directors, and 198 NIH-funded faculty) (Table 1). On average, these researchers produced 72.3 ± 83.0 articles and referenced 2139 ± 3222 articles (mean, 29.6 references per article). The cumulative h-index was 19.2 ± 15.6, and was the highest among NIH-funded researchers (24.3 ± 17.0) (P < .001). In all, 83.8% of orthopedic investigators self-cited their previous work at least once, and the total number of self-citations was highest among NIH-funded investigators (221 ± 355) (P < .001). After these self-citations were excluded, the h-index changed by 0.6 ± 1.1 for all investigators, and this change was greatest among NIH-funded researchers (1.1 ± 1.3) (P < .001).

Table 1. Effect of Self-Citation on NIH-funded Investigators, Chairpersons, and Program Directors in Orthopedics

Abbreviation: NIH, National Institutes of Health.

Most orthopedic investigators did not increase their h-index via self-citation (63.7%, P < .001). Table 2 categorizes investigators by changes in their h-index after excluding self-citations (range, 0-11). The maximal change in the h-index was seen in the most prolific group of investigators, who produced 261.0 ± 149.3 articles. In this group, the h-index increased by 11.1% ± 5.2%. The Figure investigates the relationship between the number of articles and the proportional increase in the h-index. The number of publications was positively correlated with the change in h-index after self-citations were excluded (r = 0.448, P < .001).

Table 2. Stratification of Orthopedic Researcher Investigators by Change in h-index After Self-Citation

DISCUSSION

The practice of self-citation is widely prevalent among experienced orthopedic investigators. However, this practice seems to have minimal impact on the h-index for most investigators. Self-citation had a measurable impact on the h-index only after an investigator had many publications. At a mean of 87.9 ± 68.3 articles, investigators had a ∆h-index of 1. This represented a mean 5.9% increase. Overall, these findings underscore the utility of the h-index in assessing scholarly impact and ameliorate concerns over bibliometric manipulation.

Among a large group of experienced orthopedic investigators, self-citation has minimal effect on the h-index. Importantly, most investigators (63.7%) did not experience a full integer increase in their h-index. At a threshold of ∆ h-index increase of 1, investigators had impressive h-indices (24.0 ± 13.3), which eclipsed those of recent studies of hand surgeons (10.2 ± 9.9) and spine surgeons (13.6 ± 8.7).^4,5 This finding suggests that committees for academic promotion in orthopedic surgery may disregard the impact of self-citation on the h-index. While the thresholds for promotion have not been defined in the orthopedic literature, a study in plastic surgery established an h-index threshold of 14.5 for promotion from associate to full professor.¹⁴ It may be, however, that h-indices are higher among orthopedic surgeons, as a previous study reported an h-index of 20 among full professors.¹⁵ Future research is needed to determine thresholds for promotion within orthopedic surgery, as the h-index varies by specialty according to unique citation patterns.

Continue to: It is worth highlighting...

It is worth highlighting the academic performance of NIH-funded PhD researchers in orthopedics. Even including training grant awardees in this group, this cohort exceeded the academic productivity of their orthopedic chairpersons, as measured by the h-index. Previous studies in urology, neurosurgery, and otolaryngology have demonstrated the impact of NIH-funding on academic productivity.^8-10 Ultimately, orthopedic departments could increase academic productivity by recruiting more PhD investigators with NIH funding.

In contrast to academic radiology,¹⁶ this study demonstrated a correlation between the number of publications and the increase in h-index via self-citation. Several reasons may help explain this disparity. The first reason is a technical one, as at the time of this study, the Scopus database had been updated to include citations before 1996. Considering that the h-index increases over time as older publications are cited, the exclusion of older articles is a significant limitation of previous h-index studies. Applying the same logic, the mean h-index for chairpersons of 19.9 quoted in this study contradicts a recent study, which quoted a mean h-index of 15.3.³ This previous study utilized citations that were limited to articles published after 1996.

Previous work on self-citation in the field of orthopedics has been limited to its influence on journal impact factors. Our results build on this literature in several important ways. Firstly, the calculation of a journal’s impact factor is a highly scrutinized process, and authors have criticized the mechanisms employed by editors to inflate impact factors.¹⁷ One study reported that 20% of authors have been encouraged to cite a journal during the revision process.¹⁸ Self-citation practices have been demonstrated in journals of cardiology,¹⁹ diabetes,²⁰ anesthesia,²¹ and medicine.²² A study using a hypothetical model to assess the maximum potential for h-index increase by self-citation demonstrated an h-index inflation of 5 points over 20 years (5/14, 35.7%) by publishing 3 papers per year with 3 self-citations each.²³ This study highlights a potential limitation of the h-index, but our study observed an h-index inflation of ≥4 in only 11 researchers (2.4%). Thus, results from our study ameliorate self-citation concerns in academic orthopedic surgery.

There are several limitations to this study that offer future areas of research. First, the validity of the h-index academic promotion in orthopedic surgery has not been evaluated. This was a motivation for the present study, and the authors have ongoing efforts to characterize the h-index in a larger cohort of orthopedic investigators. Importantly, an appropriate amount of self-citation was not established. It may be necessary for orthopedic researchers to cite their works as they become experts on a specific topic. Lastly, our analyses are prone to limitations inherent in the h-index, which does not account for author contribution or journal impact factors. Despite these limitations, we show that for most orthopedic researchers, the practice of self-citation does not impact the h-index.

In summary, self-citation is a widely prevalent practice among orthopedic investigators, but this practice has minimal impact on an author’s h-index. Approximately one third of orthopedic faculty in our study had a higher h-index due to self-citation. Greater h-index inflation through self-citation correlated with more publications. For the majority of orthopedic faculty, however, self-citation did not inflate the h-index, suggesting that promotional committees may disregard this concern when using the h-index as an adjunct measure for career advancement.

ANSWER

The radiograph demonstrates a fracture within the femoral neck. These types of fractures, which are slightly angulated and located at the base of the neck, are typically referred to as basicervical femur fractures. 

Prompt orthopedic surgery consultation was obtained, and the patient underwent an open reduction and internal fixation of his fracture.

ANSWER

The radiograph demonstrates a fracture within the femoral neck. These types of fractures, which are slightly angulated and located at the base of the neck, are typically referred to as basicervical femur fractures. 

Prompt orthopedic surgery consultation was obtained, and the patient underwent an open reduction and internal fixation of his fracture.

ANSWER

The radiograph demonstrates a fracture within the femoral neck. These types of fractures, which are slightly angulated and located at the base of the neck, are typically referred to as basicervical femur fractures. 

Prompt orthopedic surgery consultation was obtained, and the patient underwent an open reduction and internal fixation of his fracture.

This video was filmed at Metabolic & Endocrine Disease Summit (MEDS). Click here to learn more.

This video was filmed at Metabolic & Endocrine Disease Summit (MEDS). Click here to learn more.

This video was filmed at Metabolic & Endocrine Disease Summit (MEDS). Click here to learn more.

ABSTRACT

Glenoid bone deficiency in the setting of shoulder replacement surgery is far more common than originally reported. The frequency and severity of the glenoid defects are noted to be more common and severe with the advent of computer-assisted surgery. The results of an anatomic total shoulder arthroplasty (aTSA) with glenoid deficiency have been reported to be inferior to aTSA patients without a glenoid deficiency. Options for treating the glenoid deficiency include eccentric reaming, bone grafting, and the use of augmented glenoid components. The purpose of this article is to present the indications, technique, and results of augmented glenoids for both aTSA and reverse TSA (RTSA).

Augments for both aTSA and RTSA are viable options. They preserve subchondral bone at the same time as optimizing the joint line without the need for bone grafts. Complications, revisions and results are as good as compared to shoulder arthroplasties without glenoid wear.

Continue to: Glenoid bone deficiency...

Glenoid bone deficiency in arthritic or cuff-deficient shoulder has been reported in up to 50% of shoulder defect cases.^1,2 The type and severity of glenoid deformities vary depending on the underlying pathology and time of manifestation. Osteoarthritis with bone loss typically results in posterior or posterior inferior glenoid wear and is commonly classified as Walch types B1 or B2 (biconcave). In cases of severe erosion, B3 classification has been proposed; in this classification, bone loss becomes extremely severe, progressing to resemble a type C glenoid. Unlike primary osteoarthritis, inflammatory arthropathy more commonly causes central loss of glenoid bone (Walch A2). With the rotator cuff insufficiency, superior migration of the humeral head occurs. As these conditions progress, cuff tear arthropathy (CTA) changes result in superior or posterior-superior bone loss.¹ Anterior bone loss (type D) will be rarely encountered due to recurrent anterior instability.³

Classically, with anatomic total shoulder arthroplasty (aTSA), the surgeon considers several options for managing glenoid deficiencies. The most commonly employed technique involves eccentrically reaming the glenoid and correcting the deformity. This procedure is relatively easy but features significant drawbacks, such as sacrificing the subchondral bone, medializing the glenohumeral joint line, and secondarily shrinking the glenoid surface area. Other options include structural bone grafting behind the glenoid component. Most anatomic prosthetic glenoids prove to be unsuitable for fixation of structural bone graft. Therefore, the graft is first internally fixed, followed by placement of the glenoid component. Cement, which is commonly used for glenoid fixation, may potentially inhibit bone-graft healing. Reports using this technique documented high radiographic failure rate of up to 40% at midterm follow-up.⁴ Although leaving the glenoid component retroverted may be considered, surgeons should develop awareness of the possibility of peg penetration of the anterior glenoid neck. Additionally, retroversion in excess of 5°may increase the risk of recurrent posterior subluxation, resulting in early glenoid loosening.^5-7 Results of aTSA under significant glenoid deficiency are inferior to those of aTSA patients without glenoid deficiency.⁸ Such findings have been extremely inferior in patients with significant glenoid wear, prompting numerous surgeons to abandon aTSA in this population in favor of reverse TSA (RTSA) due to improved bony fixation.

In 2010, augmented anatomic glenoids were first introduced as a wedge (Exactech) and as a step shortly thereafter (DePuy Synthes; Figures 1A-1C). More recently, hemi-wedges have been introduced (Wright Medical Group). Augments have gained popularity due to improved range of motion vs reverse shoulder arthroplasty (RSA). However, debates remain regarding the use of posteriorly augmented components in the setting of posterior glenoid bone loss.⁸ Augments serve as another viable option for handling glenoid bone deficiency in aTSA.

Glenoid bone loss in RTSA presents similar options to aTSA. However, screw fixation of the glenoid component offers several distinct advantages. Baseplate fixation can readily be used with bone grafting and with a highly anticipated success rate. With multiple screw options, 100% support of the baseplate is not mandatory. Although bony increase offset RSAs (BIO-RSAs) have shown success, augmentation with allograft or autograft increases operative time and relies on osseous integration for long-term implant success.⁹ Metal augmented baseplates were first introduced in 2011 (Exactech) as a means of managing glenoid bone loss without structural grafting. Although initial results have been encouraging, additional studies are needed to assess the longevity of these implants (Figures 1A-1C).

aTSA AUGMENTS

aTSA augments were introduced as a means of correcting acquired glenoid bone deficiency, restoring native glenoid version, correcting humeral subluxation, and preserving the native subchondral bone. Compared with glenoid bone grafting, augmented glenoid components decrease operative time, allow for a technically easier operation, and require no bone healing for clinical success. Early and midterm results are encouraging, showing similar findings comparable to those of aTSA in non-glenoid deficient shoulders.^10-12

Continue to: INDICATIONS

Indications and limitations for augmented aTSA glenoids remain incompletely defined. The most common indication for an augmented aTSA is osteoarthritis with a B2 glenoid. We recommend augments in the occurrence of any indication of significant eccentric glenoid wear. With the expertise of surgeons, deformities of up to 20° to 25° of deformity can be readily handled with good predictability. More severe deformities can be managed with augmented aTSA components, but early failure rates may be high. The most severe acquired deformities remain best managed with RTSA. Currently, we prefer RTSA when glenoid bone loss exceeds 25°. With the widespread availability of computed tomography (CT) scans with 3-dimensional (3-D) reconstruction, glenoid bone defects are increasingly recognized. When correcting deformity, surgeons should strive to limit residual retroversion to a maximum of 5°.¹³ Preoperative planning software and computer-assisted surgery (ExactechGPS) may allow surgeons to better define the limits of augmented glenoid fixation prior to the date of surgery. We routinely utilize computer-guided glenoid preparation to control glenoid version to within 5° of neutral position.

The differences between B3 and a true type C glenoid must be recognized. Although B3 glenoids may still be a candidate for an augmented anatomic glenoid component, type C glenoids are not. Developmental abnormalities of type C glenoid occur simultaneously with humeral deformities, including medialized posterior rotator cuff musculature. Correction of the joint line to neutral version may not replicate the non-diseased state of a dysplastic type shoulder. Davis and colleagues¹⁴ have proposed treating these patients by leaving both the humerus and glenoid in their native version without correction.

TECHNIQUE

The implant that we have the most experience with is an 8° full-wedge augmented glenoid component. Such an implant is typically utilized for B2 glenoids. We recommend that a high-quality CT scan be performed for preoperative planning. As a general rule, the starting point often lies close to the ridge of B2 glenoid and more anterior than the apparent glenoid center, which is viewed intraoperatively due to asymmetric posterior wear. Full-wedge component is utilized to ream the ridge separating the neo and paleoglenoids to create a flat surface. This condition is best achieved by drilling a pilot hole at the planned glenoid central peg position to prevent the reamer from sliding anteriorly during reaming. Glenoid preparation begins with the smallest reamer until the ridge has been flattened, and the reamer makes full contact with the glenoid. The reamer diameter is then increased based on glenoid size. Slightly downsizing the glenoid implant will require less reaming to achieve full backside support. Once the glenoid is properly reamed, the central and peripheral peg holes are drilled using the appropriate guides. Holes are then dried, and all-polyethylene or composite glenoid component (either partially or completely cemented) is installed using favored cementing techniques. The advantage of composite glenoid component is that the central cage allows for bone ingrowth and may potentially improve long-term implant survival. Press fit of the central cage requires no waiting time for glenoid cement hardening before proceeding to the humerus. When placing an augmented component, adequate glenoid exposure is imperative to allow in-line placement and appropriate seating of the component without impingement on adjacent retractors.

When using the step-augmented glenoid, the paleoglenoid is prepared in a similar fashion to a standard aTSA. Once the paleoglenoid has been reamed to a neutral position, a protector plate is placed onto the paleoglenoid. and a step-cut saw is used to prepare the posterior stepped bone cut. Peripheral pegs are then drilled, and the component is installed in routine fashion. When using hemi-wedge augments, the paleoglenoid is again prepared in a similar fashion as a standard glenoid component over a cannulated guidewire. The neoglenoid is subsequently prepared using a specialized angled reamer with a positive stop to prevent over-reaming. These glenoid implants improve rotational force neutralization given the absence of flat back against the glenoid. All 3 designs preserve bone when compared with eccentric reaming alone,¹⁵ with the half-augmented wedge preserving the most bone.

Table 1. Results of Various Augmented Glenoid Components in Anatomic Total Shoulder

Arthroplasty

RESULTS

In our institution, we first used all-polyethylene posteriorly augmented glenoid components in 2010. Between 2010 and 2015, 45 patients received an 8° all-polyethylene posterior augment, and 7 patients received a 16° augment. In 2015, we transitioned to the composite caged posterior augment. All patients in our database who received an augmented glenoid component experienced improvement in active forward elevation, external rotation, American Shoulder and Elbow Surgeons (ASES), and Constant scores (Table 1). Minimum follow-up was 1 year for patients receiving both an 8° cage (mean, 1.48 years) and an 8° all-polyethylene augment (mean, 3.18 years). Figures 2A-2C show a patient with significant posterior glenoid wear and humeral head subluxation treated with an 8° wedge composite posterior augment glenoid 3 years postoperative.

Continue to: COMPLICATIONS

Two complications developed in the group undergoing composite cage augment. One patient experienced glenoid loosening after a motor vehicle accident. Another patient sustained significant intraoperative tuberosity avulsion during implantation of the humeral component, requiring a change of implant and tuberosity fixation. Although no complications were noted in the 8° all-polyethylene group, 3 patients in the 16° augment group sustained complications. One of these patients suffered a cardiac event that was unrelated to the implant. Two complications in this group were both related to loosening of the glenoid component, requiring subsequent revision.

DISCUSSION

The first report on augmented aTSA was published in 2008, and it involved a 5° augmented, anatomic glenoid.¹² One study was based on a small series of augments; the poor results led the reporting surgeons to subsequently abandon the implant.¹² This early design produced a correction on the articular side of the implant rather than the pathologic bony side. By performing such correction, the component pegs remained anteriorly oriented, placing the component at risk of perforation through the anterior glenoid neck. All current augment designs feature pegs that are oriented down the glenoid vault, with corrections occurring on the bony surface. This condition requires 2 different axes for reaming the glenoid and drilling the pegs. This approach allows the pegs to be directed down the glenoid neck, and is a far superior solution to neutralizing shear forces when compared with the implants used in the 1990s.

Early to midterm results of modern aTSA augments have been extremely encouraging with low revision rates. The main concern of recurrent posterior subluxation has been rarely reported. The concerns over glenoid loosening due to high shear forces, similarly, have not been described to date. However, surgeons should remain cautious, as longer-term follow-up remains unavailable.

The main advantage of aTSA augments is their capacity to preserve bone compared with eccentric reaming and better long-term stability. Each of the augment designs requires varying amounts of bone removal. Through biomechanics and using finite element analysis, the 3 augment types act differently, with no design demonstrating remarkable biomechanical superiority.⁶ Favorito and colleagues¹⁶ performed a retrospective review of 22 patients who underwent aTSA using an all-polyethylene, posteriorly augmented, and stepped glenoid component for posterior bone loss. At an average follow-up of 36 months, all patients experienced improvements in active forward elevation, external rotation, visual analog scale, Short Form-36 Physical Component Summary, and Western Ontario Osteoarthritis of the Shoulder scores. The authors noted that 2 patients (9%) experienced complications: 1 with an anterior dislocation and the other with recurrent posterior instability requiring revision. Sandow and Schutz¹⁷ reported the preliminary results of 10 patients who underwent aTSA using trabecular metal augment with a minimum of 2-year follow-up. All patients received either a 15° or 30° posterior, metal-backed augment for severe glenoid bone loss (Walch grade B2 or C). At a minimum of 2-year follow-up, all patients received correction to within 10° of neutral glenoid version, without any complications nor implant failures.

Regardless of augment design, all current components restore the native glenoid version, improving the length and subsequent tension of rotator cuff musculature. Similarly, re-centering the humeral head decreases the forces on the glenoid and allows for optimal function with decreasing loss of vital subchondral bone.  

Continue to: RTSA AUGMENTS

Similar to anatomic augments, metal augments were introduced for use with RTSA in 2011. Unlike anatomic augments, those for RTSA were manufactured with metal. Given the difference in bony wear patterns in patients requiring RTSA, augments were available in a number of configurations. With CTA, wear is most commonly superior. Leaving a superiorly inclined baseplate must be avoided due to risks of notching, loosening, and early failure. However, correcting this tilt will require significant reaming of the inferior glenoid. A superior augment is ideally suited for this bone-loss pattern. If the glenoid is retroverted significantly, difficulty can also arise during glenoid preparation and baseplate placement. Posterior augments may ease this aspect of the procedure. Posterior augments feature the additional benefits of tensioning any remaining posterior rotator cuff, minimizing posterior inferior impingement, and technically easing the operation.¹⁸ As we improve our awareness of glenoid orientation using computer navigation, a posterior-superior augmented implant is commonly needed to simultaneously optimize the baseplate position and to minimize reaming (Figure 3). The posterior-superior augmented baseplate has become the most commonly used baseplate augment of choice in 90% of our RTSA cases that require an augment.

INDICATIONS

Augmented RTSA baseplates are indicated when adequate backside contact cannot be achieved with eccentric reaming, thus compromising potential fixation. In our practice, we preferably use augments at <50% contact with the backside of the baseplate. Excessive superior inclination is observed in a CTA setting, commonly indicating the use of superior augments. Similarly, severe primary osteoarthritis may contain elements of posterior bone loss, leading to increased retroversion, which is where we use posterior augments. When patients exhibit combined deformities, or when the surgeon wishes to tension the posterior rotator cuff, a posterior-superior augmented glenoid baseplate is used. For extremely severe defects, we have combined bone grafting and augments. In patients with a highly deficient glenoid but good quality of the remaining bone stock, an augment allows for better contact with less reaming although it is not fully supported when compared with a non-augmented baseplate. Bone grafts can function similarly, but the autograft humeral head is not constantly present in revision situations and requires increased operative time to allow for precision carpentry. Additionally, the success of BIO-RSA requires healing of bone graft on the native glenoid to support the baseplate.¹⁹ Jones and colleagues⁹ compared metal augmented RTSA with BIO-RSA and presented equivalent results.

To minimize reaming and to obtain appropriately inferior inclination, we have discovered preoperative templating and intraoperative, computer-guided glenoid preparation to be extremely valuable (ExactechGPS). These tools allow appropriate assessment of augments and for minimal bone removal when preparing the glenoid.

TECHNIQUE

When using an augment, a fine-cut CT scan is highly recommended to aid in surgery planning. We also find 3-D reconstructions to be helpful. Preoperative planning software also allows surgeons to maximize fixation of implant within the glenoid vault. The starting point for reaming is planned based on CT. Some surgeons using augments perform minimal or no reaming at all, electing to remove the remaining cartilage with a Cobb elevator. Different reaming and drilling axes are used when using augments. In cases of severe glenoid deformity and unavailability of computer assistance, a guide wire with inferior inclination can be installed based on CT scan. Penetration of this wire down the glenoid neck can be palpated and compared with the preoperative plan. We generally prefer at least 24 mm of bone containment for the central cage. Once the surgeon is satisfied with the placement of the wire, the appropriate augment guide is placed, followed by a second guide wire. This second wire acts as the reaming axis. The first wire is removed, and the glenoid is reamed with a cannulated reamer. Once reaming is completed, the original wire is replaced in the same hole and trajectory, and the reaming wire is removed. The first wire is then drilled with a cannulated drill for the central cage. The augmented baseplate is then impacted into place, and screw fixation is performed. Again, intraoperative computer guidance allows for precision screw placement with maximal bone attachment.

Table 2. Results of Reverse Total Shoulder Arthroplasty Augmented Baseplates

RESULTS

Based on our experience, glenoid augments for RTSA have performed well at short- and mid-term follow-up. From October 2011 to July 2016, 139 patients undergoing RTSA received a posterior, superior, or posterior-superior augmented glenoid baseplate. All groups demonstrated improvements in functional outcome measures, including Constant, ASES, Shoulder Pain and Disability Index, and Simple Shoulder Test scores compared with baseline values (Table 2). The posterior-superior augment group experienced the most significant improvement in active forward flexion and external rotation, whereas the posterior augment group experienced the most significant improvement in ASES and Constant scores. Figures 4A-4C displays the radiographs of a patient with significant glenoid wear treated with a posterior-superior augment RTSA.

Continue to: COMPLICATIONS

In the superior augment group, 3 patients (13%) sustained 5 complications. One patient sustained 3 separate episodes of instability, eventually requiring revision of prosthesis. In the posterior augment group, 4 patients (8%) sustained complications. Two of the 4 patients presented postoperative humeral fractures related to traumatic events, whereas another patient sustained an intraoperative tuberosity fracture. The last complication in this group involved a postoperative draining wound that was treated with oral antibiotics.

Nine complications developed in the posterior-superior augment group (13%); these complications included aseptic baseplate loosening (5), glenoid fracture (1), humeral fracture (1), acromial stress fracture (1), and cerebrovascular accident (1).

DISCUSSION

As the use of augments in RTSA is relatively new, significantly scarce data exist regarding their outcomes and longevity. A few studies have focused on the short-term outcomes of these augments. Jones and colleagues⁹ performed a retrospective review of 80 patients who underwent RTSA and required either a structural bone graft or an augmented glenoid baseplate.⁹ They observed that although all patients showed improvements in pain, range of motion, and functional scores, the structural bone graft group incurred a 14.6% complication rate compared with none observed in the augment group. Additionally, Jones and colleagues⁹ noted that the augmented baseplate group exhibited a significantly lower rate of scapular notching compared with the bone-graft group (10% vs 18.5%) at similar follow-up intervals. A separate study by Wright and colleagues¹⁸ compared posterior vs superior augmented baseplates in RTSA. The posterior augment group demonstrated lower rates of scapular notching (6.3% vs 14.3%) and showed more significant improvements in Constant, ASES, and active forward elevation measures, compared with the superior augment group.

As more manufacturers develop augments for RTSA, and as ExactechGPS uses become more widespread, the use of RTSA baseplate augments will continually grow. Custom implants using massive metal augments are now also being introduced. Although currently too expensive for most cases, as technology drives the cost down, every patient may receive customized augmented implants in the future.

The advantages of augmented baseplate designs include minimized reaming and notching, improved tension of the remaining rotator cuff, and decreased operating room time. The disadvantages include increased cost and lack of mid- or long-term clinical data. The concerns with baseplate loosening with augments in RTSA are much less than those with augments for aTSA due to the outstanding baseplate fixation that can be achieved in RTSA.

Continue to: CONLCLUSION

Augments offer an excellent tool for surgeons performing both aTSA and RTSA with glenoid bone loss. Use of augments will become more common as more manufacturers develop them. Although clinical results fall short in full midterm, they have been positive for both augmented RTSA and aTSA. Concerns arise when performing augmented aTSA, as an upper limit of correction has not been defined with regard to component failure. Currently, no data support the maximum amount of correction that can be achieved. In our current practice, we face difficulty in correcting more than 25^° of version in young active patients with aTSA augment. Beyond this point, we perform a RTSA with an augment. In older patients or low-demand patients, we only correct minor deformities (<20^°) with an aTSA augment, opting instead for an augmented RTSA due to the lower midterm failure rates observed with this implant.

ABSTRACT

Glenoid bone deficiency in the setting of shoulder replacement surgery is far more common than originally reported. The frequency and severity of the glenoid defects are noted to be more common and severe with the advent of computer-assisted surgery. The results of an anatomic total shoulder arthroplasty (aTSA) with glenoid deficiency have been reported to be inferior to aTSA patients without a glenoid deficiency. Options for treating the glenoid deficiency include eccentric reaming, bone grafting, and the use of augmented glenoid components. The purpose of this article is to present the indications, technique, and results of augmented glenoids for both aTSA and reverse TSA (RTSA).

Augments for both aTSA and RTSA are viable options. They preserve subchondral bone at the same time as optimizing the joint line without the need for bone grafts. Complications, revisions and results are as good as compared to shoulder arthroplasties without glenoid wear.

Continue to: Glenoid bone deficiency...

Glenoid bone deficiency in arthritic or cuff-deficient shoulder has been reported in up to 50% of shoulder defect cases.^1,2 The type and severity of glenoid deformities vary depending on the underlying pathology and time of manifestation. Osteoarthritis with bone loss typically results in posterior or posterior inferior glenoid wear and is commonly classified as Walch types B1 or B2 (biconcave). In cases of severe erosion, B3 classification has been proposed; in this classification, bone loss becomes extremely severe, progressing to resemble a type C glenoid. Unlike primary osteoarthritis, inflammatory arthropathy more commonly causes central loss of glenoid bone (Walch A2). With the rotator cuff insufficiency, superior migration of the humeral head occurs. As these conditions progress, cuff tear arthropathy (CTA) changes result in superior or posterior-superior bone loss.¹ Anterior bone loss (type D) will be rarely encountered due to recurrent anterior instability.³

Classically, with anatomic total shoulder arthroplasty (aTSA), the surgeon considers several options for managing glenoid deficiencies. The most commonly employed technique involves eccentrically reaming the glenoid and correcting the deformity. This procedure is relatively easy but features significant drawbacks, such as sacrificing the subchondral bone, medializing the glenohumeral joint line, and secondarily shrinking the glenoid surface area. Other options include structural bone grafting behind the glenoid component. Most anatomic prosthetic glenoids prove to be unsuitable for fixation of structural bone graft. Therefore, the graft is first internally fixed, followed by placement of the glenoid component. Cement, which is commonly used for glenoid fixation, may potentially inhibit bone-graft healing. Reports using this technique documented high radiographic failure rate of up to 40% at midterm follow-up.⁴ Although leaving the glenoid component retroverted may be considered, surgeons should develop awareness of the possibility of peg penetration of the anterior glenoid neck. Additionally, retroversion in excess of 5°may increase the risk of recurrent posterior subluxation, resulting in early glenoid loosening.^5-7 Results of aTSA under significant glenoid deficiency are inferior to those of aTSA patients without glenoid deficiency.⁸ Such findings have been extremely inferior in patients with significant glenoid wear, prompting numerous surgeons to abandon aTSA in this population in favor of reverse TSA (RTSA) due to improved bony fixation.

In 2010, augmented anatomic glenoids were first introduced as a wedge (Exactech) and as a step shortly thereafter (DePuy Synthes; Figures 1A-1C). More recently, hemi-wedges have been introduced (Wright Medical Group). Augments have gained popularity due to improved range of motion vs reverse shoulder arthroplasty (RSA). However, debates remain regarding the use of posteriorly augmented components in the setting of posterior glenoid bone loss.⁸ Augments serve as another viable option for handling glenoid bone deficiency in aTSA.

Glenoid bone loss in RTSA presents similar options to aTSA. However, screw fixation of the glenoid component offers several distinct advantages. Baseplate fixation can readily be used with bone grafting and with a highly anticipated success rate. With multiple screw options, 100% support of the baseplate is not mandatory. Although bony increase offset RSAs (BIO-RSAs) have shown success, augmentation with allograft or autograft increases operative time and relies on osseous integration for long-term implant success.⁹ Metal augmented baseplates were first introduced in 2011 (Exactech) as a means of managing glenoid bone loss without structural grafting. Although initial results have been encouraging, additional studies are needed to assess the longevity of these implants (Figures 1A-1C).

aTSA AUGMENTS

aTSA augments were introduced as a means of correcting acquired glenoid bone deficiency, restoring native glenoid version, correcting humeral subluxation, and preserving the native subchondral bone. Compared with glenoid bone grafting, augmented glenoid components decrease operative time, allow for a technically easier operation, and require no bone healing for clinical success. Early and midterm results are encouraging, showing similar findings comparable to those of aTSA in non-glenoid deficient shoulders.^10-12

Continue to: INDICATIONS

Indications and limitations for augmented aTSA glenoids remain incompletely defined. The most common indication for an augmented aTSA is osteoarthritis with a B2 glenoid. We recommend augments in the occurrence of any indication of significant eccentric glenoid wear. With the expertise of surgeons, deformities of up to 20° to 25° of deformity can be readily handled with good predictability. More severe deformities can be managed with augmented aTSA components, but early failure rates may be high. The most severe acquired deformities remain best managed with RTSA. Currently, we prefer RTSA when glenoid bone loss exceeds 25°. With the widespread availability of computed tomography (CT) scans with 3-dimensional (3-D) reconstruction, glenoid bone defects are increasingly recognized. When correcting deformity, surgeons should strive to limit residual retroversion to a maximum of 5°.¹³ Preoperative planning software and computer-assisted surgery (ExactechGPS) may allow surgeons to better define the limits of augmented glenoid fixation prior to the date of surgery. We routinely utilize computer-guided glenoid preparation to control glenoid version to within 5° of neutral position.

The differences between B3 and a true type C glenoid must be recognized. Although B3 glenoids may still be a candidate for an augmented anatomic glenoid component, type C glenoids are not. Developmental abnormalities of type C glenoid occur simultaneously with humeral deformities, including medialized posterior rotator cuff musculature. Correction of the joint line to neutral version may not replicate the non-diseased state of a dysplastic type shoulder. Davis and colleagues¹⁴ have proposed treating these patients by leaving both the humerus and glenoid in their native version without correction.

TECHNIQUE

The implant that we have the most experience with is an 8° full-wedge augmented glenoid component. Such an implant is typically utilized for B2 glenoids. We recommend that a high-quality CT scan be performed for preoperative planning. As a general rule, the starting point often lies close to the ridge of B2 glenoid and more anterior than the apparent glenoid center, which is viewed intraoperatively due to asymmetric posterior wear. Full-wedge component is utilized to ream the ridge separating the neo and paleoglenoids to create a flat surface. This condition is best achieved by drilling a pilot hole at the planned glenoid central peg position to prevent the reamer from sliding anteriorly during reaming. Glenoid preparation begins with the smallest reamer until the ridge has been flattened, and the reamer makes full contact with the glenoid. The reamer diameter is then increased based on glenoid size. Slightly downsizing the glenoid implant will require less reaming to achieve full backside support. Once the glenoid is properly reamed, the central and peripheral peg holes are drilled using the appropriate guides. Holes are then dried, and all-polyethylene or composite glenoid component (either partially or completely cemented) is installed using favored cementing techniques. The advantage of composite glenoid component is that the central cage allows for bone ingrowth and may potentially improve long-term implant survival. Press fit of the central cage requires no waiting time for glenoid cement hardening before proceeding to the humerus. When placing an augmented component, adequate glenoid exposure is imperative to allow in-line placement and appropriate seating of the component without impingement on adjacent retractors.

When using the step-augmented glenoid, the paleoglenoid is prepared in a similar fashion to a standard aTSA. Once the paleoglenoid has been reamed to a neutral position, a protector plate is placed onto the paleoglenoid. and a step-cut saw is used to prepare the posterior stepped bone cut. Peripheral pegs are then drilled, and the component is installed in routine fashion. When using hemi-wedge augments, the paleoglenoid is again prepared in a similar fashion as a standard glenoid component over a cannulated guidewire. The neoglenoid is subsequently prepared using a specialized angled reamer with a positive stop to prevent over-reaming. These glenoid implants improve rotational force neutralization given the absence of flat back against the glenoid. All 3 designs preserve bone when compared with eccentric reaming alone,¹⁵ with the half-augmented wedge preserving the most bone.

Table 1. Results of Various Augmented Glenoid Components in Anatomic Total Shoulder

Arthroplasty

RESULTS

In our institution, we first used all-polyethylene posteriorly augmented glenoid components in 2010. Between 2010 and 2015, 45 patients received an 8° all-polyethylene posterior augment, and 7 patients received a 16° augment. In 2015, we transitioned to the composite caged posterior augment. All patients in our database who received an augmented glenoid component experienced improvement in active forward elevation, external rotation, American Shoulder and Elbow Surgeons (ASES), and Constant scores (Table 1). Minimum follow-up was 1 year for patients receiving both an 8° cage (mean, 1.48 years) and an 8° all-polyethylene augment (mean, 3.18 years). Figures 2A-2C show a patient with significant posterior glenoid wear and humeral head subluxation treated with an 8° wedge composite posterior augment glenoid 3 years postoperative.

Continue to: COMPLICATIONS

Two complications developed in the group undergoing composite cage augment. One patient experienced glenoid loosening after a motor vehicle accident. Another patient sustained significant intraoperative tuberosity avulsion during implantation of the humeral component, requiring a change of implant and tuberosity fixation. Although no complications were noted in the 8° all-polyethylene group, 3 patients in the 16° augment group sustained complications. One of these patients suffered a cardiac event that was unrelated to the implant. Two complications in this group were both related to loosening of the glenoid component, requiring subsequent revision.

DISCUSSION

The first report on augmented aTSA was published in 2008, and it involved a 5° augmented, anatomic glenoid.¹² One study was based on a small series of augments; the poor results led the reporting surgeons to subsequently abandon the implant.¹² This early design produced a correction on the articular side of the implant rather than the pathologic bony side. By performing such correction, the component pegs remained anteriorly oriented, placing the component at risk of perforation through the anterior glenoid neck. All current augment designs feature pegs that are oriented down the glenoid vault, with corrections occurring on the bony surface. This condition requires 2 different axes for reaming the glenoid and drilling the pegs. This approach allows the pegs to be directed down the glenoid neck, and is a far superior solution to neutralizing shear forces when compared with the implants used in the 1990s.

Early to midterm results of modern aTSA augments have been extremely encouraging with low revision rates. The main concern of recurrent posterior subluxation has been rarely reported. The concerns over glenoid loosening due to high shear forces, similarly, have not been described to date. However, surgeons should remain cautious, as longer-term follow-up remains unavailable.

The main advantage of aTSA augments is their capacity to preserve bone compared with eccentric reaming and better long-term stability. Each of the augment designs requires varying amounts of bone removal. Through biomechanics and using finite element analysis, the 3 augment types act differently, with no design demonstrating remarkable biomechanical superiority.⁶ Favorito and colleagues¹⁶ performed a retrospective review of 22 patients who underwent aTSA using an all-polyethylene, posteriorly augmented, and stepped glenoid component for posterior bone loss. At an average follow-up of 36 months, all patients experienced improvements in active forward elevation, external rotation, visual analog scale, Short Form-36 Physical Component Summary, and Western Ontario Osteoarthritis of the Shoulder scores. The authors noted that 2 patients (9%) experienced complications: 1 with an anterior dislocation and the other with recurrent posterior instability requiring revision. Sandow and Schutz¹⁷ reported the preliminary results of 10 patients who underwent aTSA using trabecular metal augment with a minimum of 2-year follow-up. All patients received either a 15° or 30° posterior, metal-backed augment for severe glenoid bone loss (Walch grade B2 or C). At a minimum of 2-year follow-up, all patients received correction to within 10° of neutral glenoid version, without any complications nor implant failures.

Regardless of augment design, all current components restore the native glenoid version, improving the length and subsequent tension of rotator cuff musculature. Similarly, re-centering the humeral head decreases the forces on the glenoid and allows for optimal function with decreasing loss of vital subchondral bone.  

Continue to: RTSA AUGMENTS

Similar to anatomic augments, metal augments were introduced for use with RTSA in 2011. Unlike anatomic augments, those for RTSA were manufactured with metal. Given the difference in bony wear patterns in patients requiring RTSA, augments were available in a number of configurations. With CTA, wear is most commonly superior. Leaving a superiorly inclined baseplate must be avoided due to risks of notching, loosening, and early failure. However, correcting this tilt will require significant reaming of the inferior glenoid. A superior augment is ideally suited for this bone-loss pattern. If the glenoid is retroverted significantly, difficulty can also arise during glenoid preparation and baseplate placement. Posterior augments may ease this aspect of the procedure. Posterior augments feature the additional benefits of tensioning any remaining posterior rotator cuff, minimizing posterior inferior impingement, and technically easing the operation.¹⁸ As we improve our awareness of glenoid orientation using computer navigation, a posterior-superior augmented implant is commonly needed to simultaneously optimize the baseplate position and to minimize reaming (Figure 3). The posterior-superior augmented baseplate has become the most commonly used baseplate augment of choice in 90% of our RTSA cases that require an augment.

INDICATIONS

Augmented RTSA baseplates are indicated when adequate backside contact cannot be achieved with eccentric reaming, thus compromising potential fixation. In our practice, we preferably use augments at <50% contact with the backside of the baseplate. Excessive superior inclination is observed in a CTA setting, commonly indicating the use of superior augments. Similarly, severe primary osteoarthritis may contain elements of posterior bone loss, leading to increased retroversion, which is where we use posterior augments. When patients exhibit combined deformities, or when the surgeon wishes to tension the posterior rotator cuff, a posterior-superior augmented glenoid baseplate is used. For extremely severe defects, we have combined bone grafting and augments. In patients with a highly deficient glenoid but good quality of the remaining bone stock, an augment allows for better contact with less reaming although it is not fully supported when compared with a non-augmented baseplate. Bone grafts can function similarly, but the autograft humeral head is not constantly present in revision situations and requires increased operative time to allow for precision carpentry. Additionally, the success of BIO-RSA requires healing of bone graft on the native glenoid to support the baseplate.¹⁹ Jones and colleagues⁹ compared metal augmented RTSA with BIO-RSA and presented equivalent results.

To minimize reaming and to obtain appropriately inferior inclination, we have discovered preoperative templating and intraoperative, computer-guided glenoid preparation to be extremely valuable (ExactechGPS). These tools allow appropriate assessment of augments and for minimal bone removal when preparing the glenoid.

TECHNIQUE

When using an augment, a fine-cut CT scan is highly recommended to aid in surgery planning. We also find 3-D reconstructions to be helpful. Preoperative planning software also allows surgeons to maximize fixation of implant within the glenoid vault. The starting point for reaming is planned based on CT. Some surgeons using augments perform minimal or no reaming at all, electing to remove the remaining cartilage with a Cobb elevator. Different reaming and drilling axes are used when using augments. In cases of severe glenoid deformity and unavailability of computer assistance, a guide wire with inferior inclination can be installed based on CT scan. Penetration of this wire down the glenoid neck can be palpated and compared with the preoperative plan. We generally prefer at least 24 mm of bone containment for the central cage. Once the surgeon is satisfied with the placement of the wire, the appropriate augment guide is placed, followed by a second guide wire. This second wire acts as the reaming axis. The first wire is removed, and the glenoid is reamed with a cannulated reamer. Once reaming is completed, the original wire is replaced in the same hole and trajectory, and the reaming wire is removed. The first wire is then drilled with a cannulated drill for the central cage. The augmented baseplate is then impacted into place, and screw fixation is performed. Again, intraoperative computer guidance allows for precision screw placement with maximal bone attachment.

Table 2. Results of Reverse Total Shoulder Arthroplasty Augmented Baseplates

RESULTS

Based on our experience, glenoid augments for RTSA have performed well at short- and mid-term follow-up. From October 2011 to July 2016, 139 patients undergoing RTSA received a posterior, superior, or posterior-superior augmented glenoid baseplate. All groups demonstrated improvements in functional outcome measures, including Constant, ASES, Shoulder Pain and Disability Index, and Simple Shoulder Test scores compared with baseline values (Table 2). The posterior-superior augment group experienced the most significant improvement in active forward flexion and external rotation, whereas the posterior augment group experienced the most significant improvement in ASES and Constant scores. Figures 4A-4C displays the radiographs of a patient with significant glenoid wear treated with a posterior-superior augment RTSA.

Continue to: COMPLICATIONS

In the superior augment group, 3 patients (13%) sustained 5 complications. One patient sustained 3 separate episodes of instability, eventually requiring revision of prosthesis. In the posterior augment group, 4 patients (8%) sustained complications. Two of the 4 patients presented postoperative humeral fractures related to traumatic events, whereas another patient sustained an intraoperative tuberosity fracture. The last complication in this group involved a postoperative draining wound that was treated with oral antibiotics.

Nine complications developed in the posterior-superior augment group (13%); these complications included aseptic baseplate loosening (5), glenoid fracture (1), humeral fracture (1), acromial stress fracture (1), and cerebrovascular accident (1).

DISCUSSION

As the use of augments in RTSA is relatively new, significantly scarce data exist regarding their outcomes and longevity. A few studies have focused on the short-term outcomes of these augments. Jones and colleagues⁹ performed a retrospective review of 80 patients who underwent RTSA and required either a structural bone graft or an augmented glenoid baseplate.⁹ They observed that although all patients showed improvements in pain, range of motion, and functional scores, the structural bone graft group incurred a 14.6% complication rate compared with none observed in the augment group. Additionally, Jones and colleagues⁹ noted that the augmented baseplate group exhibited a significantly lower rate of scapular notching compared with the bone-graft group (10% vs 18.5%) at similar follow-up intervals. A separate study by Wright and colleagues¹⁸ compared posterior vs superior augmented baseplates in RTSA. The posterior augment group demonstrated lower rates of scapular notching (6.3% vs 14.3%) and showed more significant improvements in Constant, ASES, and active forward elevation measures, compared with the superior augment group.

As more manufacturers develop augments for RTSA, and as ExactechGPS uses become more widespread, the use of RTSA baseplate augments will continually grow. Custom implants using massive metal augments are now also being introduced. Although currently too expensive for most cases, as technology drives the cost down, every patient may receive customized augmented implants in the future.

The advantages of augmented baseplate designs include minimized reaming and notching, improved tension of the remaining rotator cuff, and decreased operating room time. The disadvantages include increased cost and lack of mid- or long-term clinical data. The concerns with baseplate loosening with augments in RTSA are much less than those with augments for aTSA due to the outstanding baseplate fixation that can be achieved in RTSA.

Continue to: CONLCLUSION

Augments offer an excellent tool for surgeons performing both aTSA and RTSA with glenoid bone loss. Use of augments will become more common as more manufacturers develop them. Although clinical results fall short in full midterm, they have been positive for both augmented RTSA and aTSA. Concerns arise when performing augmented aTSA, as an upper limit of correction has not been defined with regard to component failure. Currently, no data support the maximum amount of correction that can be achieved. In our current practice, we face difficulty in correcting more than 25^° of version in young active patients with aTSA augment. Beyond this point, we perform a RTSA with an augment. In older patients or low-demand patients, we only correct minor deformities (<20^°) with an aTSA augment, opting instead for an augmented RTSA due to the lower midterm failure rates observed with this implant.

ABSTRACT

Glenoid bone deficiency in the setting of shoulder replacement surgery is far more common than originally reported. The frequency and severity of the glenoid defects are noted to be more common and severe with the advent of computer-assisted surgery. The results of an anatomic total shoulder arthroplasty (aTSA) with glenoid deficiency have been reported to be inferior to aTSA patients without a glenoid deficiency. Options for treating the glenoid deficiency include eccentric reaming, bone grafting, and the use of augmented glenoid components. The purpose of this article is to present the indications, technique, and results of augmented glenoids for both aTSA and reverse TSA (RTSA).

Augments for both aTSA and RTSA are viable options. They preserve subchondral bone at the same time as optimizing the joint line without the need for bone grafts. Complications, revisions and results are as good as compared to shoulder arthroplasties without glenoid wear.

Continue to: Glenoid bone deficiency...

Glenoid bone deficiency in arthritic or cuff-deficient shoulder has been reported in up to 50% of shoulder defect cases.^1,2 The type and severity of glenoid deformities vary depending on the underlying pathology and time of manifestation. Osteoarthritis with bone loss typically results in posterior or posterior inferior glenoid wear and is commonly classified as Walch types B1 or B2 (biconcave). In cases of severe erosion, B3 classification has been proposed; in this classification, bone loss becomes extremely severe, progressing to resemble a type C glenoid. Unlike primary osteoarthritis, inflammatory arthropathy more commonly causes central loss of glenoid bone (Walch A2). With the rotator cuff insufficiency, superior migration of the humeral head occurs. As these conditions progress, cuff tear arthropathy (CTA) changes result in superior or posterior-superior bone loss.¹ Anterior bone loss (type D) will be rarely encountered due to recurrent anterior instability.³

Classically, with anatomic total shoulder arthroplasty (aTSA), the surgeon considers several options for managing glenoid deficiencies. The most commonly employed technique involves eccentrically reaming the glenoid and correcting the deformity. This procedure is relatively easy but features significant drawbacks, such as sacrificing the subchondral bone, medializing the glenohumeral joint line, and secondarily shrinking the glenoid surface area. Other options include structural bone grafting behind the glenoid component. Most anatomic prosthetic glenoids prove to be unsuitable for fixation of structural bone graft. Therefore, the graft is first internally fixed, followed by placement of the glenoid component. Cement, which is commonly used for glenoid fixation, may potentially inhibit bone-graft healing. Reports using this technique documented high radiographic failure rate of up to 40% at midterm follow-up.⁴ Although leaving the glenoid component retroverted may be considered, surgeons should develop awareness of the possibility of peg penetration of the anterior glenoid neck. Additionally, retroversion in excess of 5°may increase the risk of recurrent posterior subluxation, resulting in early glenoid loosening.^5-7 Results of aTSA under significant glenoid deficiency are inferior to those of aTSA patients without glenoid deficiency.⁸ Such findings have been extremely inferior in patients with significant glenoid wear, prompting numerous surgeons to abandon aTSA in this population in favor of reverse TSA (RTSA) due to improved bony fixation.

In 2010, augmented anatomic glenoids were first introduced as a wedge (Exactech) and as a step shortly thereafter (DePuy Synthes; Figures 1A-1C). More recently, hemi-wedges have been introduced (Wright Medical Group). Augments have gained popularity due to improved range of motion vs reverse shoulder arthroplasty (RSA). However, debates remain regarding the use of posteriorly augmented components in the setting of posterior glenoid bone loss.⁸ Augments serve as another viable option for handling glenoid bone deficiency in aTSA.

Glenoid bone loss in RTSA presents similar options to aTSA. However, screw fixation of the glenoid component offers several distinct advantages. Baseplate fixation can readily be used with bone grafting and with a highly anticipated success rate. With multiple screw options, 100% support of the baseplate is not mandatory. Although bony increase offset RSAs (BIO-RSAs) have shown success, augmentation with allograft or autograft increases operative time and relies on osseous integration for long-term implant success.⁹ Metal augmented baseplates were first introduced in 2011 (Exactech) as a means of managing glenoid bone loss without structural grafting. Although initial results have been encouraging, additional studies are needed to assess the longevity of these implants (Figures 1A-1C).

aTSA AUGMENTS

aTSA augments were introduced as a means of correcting acquired glenoid bone deficiency, restoring native glenoid version, correcting humeral subluxation, and preserving the native subchondral bone. Compared with glenoid bone grafting, augmented glenoid components decrease operative time, allow for a technically easier operation, and require no bone healing for clinical success. Early and midterm results are encouraging, showing similar findings comparable to those of aTSA in non-glenoid deficient shoulders.^10-12

Continue to: INDICATIONS

Indications and limitations for augmented aTSA glenoids remain incompletely defined. The most common indication for an augmented aTSA is osteoarthritis with a B2 glenoid. We recommend augments in the occurrence of any indication of significant eccentric glenoid wear. With the expertise of surgeons, deformities of up to 20° to 25° of deformity can be readily handled with good predictability. More severe deformities can be managed with augmented aTSA components, but early failure rates may be high. The most severe acquired deformities remain best managed with RTSA. Currently, we prefer RTSA when glenoid bone loss exceeds 25°. With the widespread availability of computed tomography (CT) scans with 3-dimensional (3-D) reconstruction, glenoid bone defects are increasingly recognized. When correcting deformity, surgeons should strive to limit residual retroversion to a maximum of 5°.¹³ Preoperative planning software and computer-assisted surgery (ExactechGPS) may allow surgeons to better define the limits of augmented glenoid fixation prior to the date of surgery. We routinely utilize computer-guided glenoid preparation to control glenoid version to within 5° of neutral position.

The differences between B3 and a true type C glenoid must be recognized. Although B3 glenoids may still be a candidate for an augmented anatomic glenoid component, type C glenoids are not. Developmental abnormalities of type C glenoid occur simultaneously with humeral deformities, including medialized posterior rotator cuff musculature. Correction of the joint line to neutral version may not replicate the non-diseased state of a dysplastic type shoulder. Davis and colleagues¹⁴ have proposed treating these patients by leaving both the humerus and glenoid in their native version without correction.

TECHNIQUE

The implant that we have the most experience with is an 8° full-wedge augmented glenoid component. Such an implant is typically utilized for B2 glenoids. We recommend that a high-quality CT scan be performed for preoperative planning. As a general rule, the starting point often lies close to the ridge of B2 glenoid and more anterior than the apparent glenoid center, which is viewed intraoperatively due to asymmetric posterior wear. Full-wedge component is utilized to ream the ridge separating the neo and paleoglenoids to create a flat surface. This condition is best achieved by drilling a pilot hole at the planned glenoid central peg position to prevent the reamer from sliding anteriorly during reaming. Glenoid preparation begins with the smallest reamer until the ridge has been flattened, and the reamer makes full contact with the glenoid. The reamer diameter is then increased based on glenoid size. Slightly downsizing the glenoid implant will require less reaming to achieve full backside support. Once the glenoid is properly reamed, the central and peripheral peg holes are drilled using the appropriate guides. Holes are then dried, and all-polyethylene or composite glenoid component (either partially or completely cemented) is installed using favored cementing techniques. The advantage of composite glenoid component is that the central cage allows for bone ingrowth and may potentially improve long-term implant survival. Press fit of the central cage requires no waiting time for glenoid cement hardening before proceeding to the humerus. When placing an augmented component, adequate glenoid exposure is imperative to allow in-line placement and appropriate seating of the component without impingement on adjacent retractors.

When using the step-augmented glenoid, the paleoglenoid is prepared in a similar fashion to a standard aTSA. Once the paleoglenoid has been reamed to a neutral position, a protector plate is placed onto the paleoglenoid. and a step-cut saw is used to prepare the posterior stepped bone cut. Peripheral pegs are then drilled, and the component is installed in routine fashion. When using hemi-wedge augments, the paleoglenoid is again prepared in a similar fashion as a standard glenoid component over a cannulated guidewire. The neoglenoid is subsequently prepared using a specialized angled reamer with a positive stop to prevent over-reaming. These glenoid implants improve rotational force neutralization given the absence of flat back against the glenoid. All 3 designs preserve bone when compared with eccentric reaming alone,¹⁵ with the half-augmented wedge preserving the most bone.

Table 1. Results of Various Augmented Glenoid Components in Anatomic Total Shoulder

Arthroplasty

RESULTS

In our institution, we first used all-polyethylene posteriorly augmented glenoid components in 2010. Between 2010 and 2015, 45 patients received an 8° all-polyethylene posterior augment, and 7 patients received a 16° augment. In 2015, we transitioned to the composite caged posterior augment. All patients in our database who received an augmented glenoid component experienced improvement in active forward elevation, external rotation, American Shoulder and Elbow Surgeons (ASES), and Constant scores (Table 1). Minimum follow-up was 1 year for patients receiving both an 8° cage (mean, 1.48 years) and an 8° all-polyethylene augment (mean, 3.18 years). Figures 2A-2C show a patient with significant posterior glenoid wear and humeral head subluxation treated with an 8° wedge composite posterior augment glenoid 3 years postoperative.

Continue to: COMPLICATIONS

Two complications developed in the group undergoing composite cage augment. One patient experienced glenoid loosening after a motor vehicle accident. Another patient sustained significant intraoperative tuberosity avulsion during implantation of the humeral component, requiring a change of implant and tuberosity fixation. Although no complications were noted in the 8° all-polyethylene group, 3 patients in the 16° augment group sustained complications. One of these patients suffered a cardiac event that was unrelated to the implant. Two complications in this group were both related to loosening of the glenoid component, requiring subsequent revision.

DISCUSSION

The first report on augmented aTSA was published in 2008, and it involved a 5° augmented, anatomic glenoid.¹² One study was based on a small series of augments; the poor results led the reporting surgeons to subsequently abandon the implant.¹² This early design produced a correction on the articular side of the implant rather than the pathologic bony side. By performing such correction, the component pegs remained anteriorly oriented, placing the component at risk of perforation through the anterior glenoid neck. All current augment designs feature pegs that are oriented down the glenoid vault, with corrections occurring on the bony surface. This condition requires 2 different axes for reaming the glenoid and drilling the pegs. This approach allows the pegs to be directed down the glenoid neck, and is a far superior solution to neutralizing shear forces when compared with the implants used in the 1990s.

Early to midterm results of modern aTSA augments have been extremely encouraging with low revision rates. The main concern of recurrent posterior subluxation has been rarely reported. The concerns over glenoid loosening due to high shear forces, similarly, have not been described to date. However, surgeons should remain cautious, as longer-term follow-up remains unavailable.

The main advantage of aTSA augments is their capacity to preserve bone compared with eccentric reaming and better long-term stability. Each of the augment designs requires varying amounts of bone removal. Through biomechanics and using finite element analysis, the 3 augment types act differently, with no design demonstrating remarkable biomechanical superiority.⁶ Favorito and colleagues¹⁶ performed a retrospective review of 22 patients who underwent aTSA using an all-polyethylene, posteriorly augmented, and stepped glenoid component for posterior bone loss. At an average follow-up of 36 months, all patients experienced improvements in active forward elevation, external rotation, visual analog scale, Short Form-36 Physical Component Summary, and Western Ontario Osteoarthritis of the Shoulder scores. The authors noted that 2 patients (9%) experienced complications: 1 with an anterior dislocation and the other with recurrent posterior instability requiring revision. Sandow and Schutz¹⁷ reported the preliminary results of 10 patients who underwent aTSA using trabecular metal augment with a minimum of 2-year follow-up. All patients received either a 15° or 30° posterior, metal-backed augment for severe glenoid bone loss (Walch grade B2 or C). At a minimum of 2-year follow-up, all patients received correction to within 10° of neutral glenoid version, without any complications nor implant failures.

Regardless of augment design, all current components restore the native glenoid version, improving the length and subsequent tension of rotator cuff musculature. Similarly, re-centering the humeral head decreases the forces on the glenoid and allows for optimal function with decreasing loss of vital subchondral bone.  

Continue to: RTSA AUGMENTS

Similar to anatomic augments, metal augments were introduced for use with RTSA in 2011. Unlike anatomic augments, those for RTSA were manufactured with metal. Given the difference in bony wear patterns in patients requiring RTSA, augments were available in a number of configurations. With CTA, wear is most commonly superior. Leaving a superiorly inclined baseplate must be avoided due to risks of notching, loosening, and early failure. However, correcting this tilt will require significant reaming of the inferior glenoid. A superior augment is ideally suited for this bone-loss pattern. If the glenoid is retroverted significantly, difficulty can also arise during glenoid preparation and baseplate placement. Posterior augments may ease this aspect of the procedure. Posterior augments feature the additional benefits of tensioning any remaining posterior rotator cuff, minimizing posterior inferior impingement, and technically easing the operation.¹⁸ As we improve our awareness of glenoid orientation using computer navigation, a posterior-superior augmented implant is commonly needed to simultaneously optimize the baseplate position and to minimize reaming (Figure 3). The posterior-superior augmented baseplate has become the most commonly used baseplate augment of choice in 90% of our RTSA cases that require an augment.

INDICATIONS

Augmented RTSA baseplates are indicated when adequate backside contact cannot be achieved with eccentric reaming, thus compromising potential fixation. In our practice, we preferably use augments at <50% contact with the backside of the baseplate. Excessive superior inclination is observed in a CTA setting, commonly indicating the use of superior augments. Similarly, severe primary osteoarthritis may contain elements of posterior bone loss, leading to increased retroversion, which is where we use posterior augments. When patients exhibit combined deformities, or when the surgeon wishes to tension the posterior rotator cuff, a posterior-superior augmented glenoid baseplate is used. For extremely severe defects, we have combined bone grafting and augments. In patients with a highly deficient glenoid but good quality of the remaining bone stock, an augment allows for better contact with less reaming although it is not fully supported when compared with a non-augmented baseplate. Bone grafts can function similarly, but the autograft humeral head is not constantly present in revision situations and requires increased operative time to allow for precision carpentry. Additionally, the success of BIO-RSA requires healing of bone graft on the native glenoid to support the baseplate.¹⁹ Jones and colleagues⁹ compared metal augmented RTSA with BIO-RSA and presented equivalent results.

To minimize reaming and to obtain appropriately inferior inclination, we have discovered preoperative templating and intraoperative, computer-guided glenoid preparation to be extremely valuable (ExactechGPS). These tools allow appropriate assessment of augments and for minimal bone removal when preparing the glenoid.

TECHNIQUE

When using an augment, a fine-cut CT scan is highly recommended to aid in surgery planning. We also find 3-D reconstructions to be helpful. Preoperative planning software also allows surgeons to maximize fixation of implant within the glenoid vault. The starting point for reaming is planned based on CT. Some surgeons using augments perform minimal or no reaming at all, electing to remove the remaining cartilage with a Cobb elevator. Different reaming and drilling axes are used when using augments. In cases of severe glenoid deformity and unavailability of computer assistance, a guide wire with inferior inclination can be installed based on CT scan. Penetration of this wire down the glenoid neck can be palpated and compared with the preoperative plan. We generally prefer at least 24 mm of bone containment for the central cage. Once the surgeon is satisfied with the placement of the wire, the appropriate augment guide is placed, followed by a second guide wire. This second wire acts as the reaming axis. The first wire is removed, and the glenoid is reamed with a cannulated reamer. Once reaming is completed, the original wire is replaced in the same hole and trajectory, and the reaming wire is removed. The first wire is then drilled with a cannulated drill for the central cage. The augmented baseplate is then impacted into place, and screw fixation is performed. Again, intraoperative computer guidance allows for precision screw placement with maximal bone attachment.

Table 2. Results of Reverse Total Shoulder Arthroplasty Augmented Baseplates