Orthopedics

Patients experiencing sacroiliac joint (SIJ) dysfunction might show symptoms that overlap with those seen in lumbar spine pathology. This article reviews diagnostic tools that assist practitioners to discern the true pain generator in patients with low back pain (LBP) and therapeutic approaches when the cause is SIJ dysfunction.

Prevalence

Most of the US population will experience LBP at some point in their lives. A 2002 National Health Interview survey found that more than one-quarter (26.4%) of 31 044 respondents had complained of LBP in the previous 3 months.¹ About 74 million individuals in the US experienced LBP in the past 3 months.¹ A full 10% of the US population is expected to suffer from chronic LBP, and it is estimated that 2.3% of all visits to physicians are related to LBP.¹

The etiology of LBP often is unclear even after thorough clinical and radiographic evaluation because of the myriad possible mechanisms. Degenerative disc disease, facet arthropathy, ligamentous hypertrophy, muscle spasm, hip arthropathy, and SIJ dysfunction are potential pain generators and exact clinical and radiographic correlation is not always possible. Compounding this difficulty is the lack of specificity with current diagnostic techniques. For example, many patients will have disc desiccation or herniation without any LBP or radicular symptoms on radiographic studies, such as X-rays, computed tomography (CT), and magnetic resonance imaging (MRI). As such, providers of patients with diffuse radiographic abnormalities often have to identify a specific pain generator, which might not have any role in the patient’s pain.

Other tests, such as electromyographic studies, positron emission tomography (PET) scans, discography, and epidural steroid injections, can help pinpoint a specific pain generator. These tests might help determine whether the patient has a surgically treatable condition and could help predict whether a patient’s symptoms will respond to surgery.

However, the standard spine surgery workup often fails to identify an obvious pain generator in many individuals. The significant number of patients that fall into this category has prompted spine surgeons to consider other potential etiologies for LBP, and SIJ dysfunction has become a rapidly developing field of research.

Sacroiliac Joint Dysfunction

The SIJ is a bilateral, C-shaped synovial joint surrounded by a fibrous capsule and affixes the sacrum to the ilia. Several sacral ligaments and pelvic muscles support the SIJ. The L5 nerve ventral ramus and lumbosacral trunk pass anteriorly and the S1 nerve ventral ramus passes inferiorly to the joint capsule. The SIJ is innervated by the dorsal rami of L4-S3 nerve roots, transmitting nociception and temperature. Mechanisms of injury to the SIJ could arise from intra- and extra-articular etiologies, including capsular disruption, ligamentous tension, muscular inflammation, shearing, fractures, arthritis, and infection.² Patients could develop SIJ pain spontaneously or after a traumatic event or repetitive shear.³ Risk factors for developing SIJ dysfunction include a history of lumbar fusion, scoliosis, leg length discrepancies, sustained athletic activity, pregnancy, seronegative HLA-B27 spondyloarthropathies, or gait abnormalities. Inflammation of the SIJ and surrounding structures secondary to an environmental insult in susceptible individuals is a common theme among these etiologies.²

 

Pain from the SIJ is localized to an area of approximately 3 cm × 10 cm that is inferior to the ipsilateral posterior superior iliac spine.⁴ Referred pain maps from SIJ dysfunction extend in the L5-S1 nerve distributions, commonly seen in the buttocks, groin, posterior thigh, and lower leg with radicular symptoms. However, this pain distribution demonstrates extensive variability among patients and bears strong similarities to discogenic or facet joint sources of LBP.^5-7 Direct communication has been shown between the SIJ and adjacent neural structures, namely the L5 nerve, sacral foramina, and the lumbosacral plexus. These direct pathways could explain an inflammatory mechanism for lower extremity symptoms seen in SIJ dysfunction.⁸

The prevalence of SIJ dysfunction among patients with LBP is estimated to be 15% to 30%, an extraordinary number given the total number of patients presenting with LBP every year.⁹ These patients might represent a significant segment of patients with an unrevealing standard spine evaluation. Despite the large number of patients who experience SIJ dysfunction, there is disagreement about optimal methods for diagnosis and treatment.

Diagnosis

The International Association for the Study of Pain has proposed criteria for evaluating patients who have suspected SIJ dysfunction: Pain must be in the SIJ area, should be reproducible by performing specific provocative maneuvers, and must be relieved by injection of local anesthetic into the SIJ.¹⁰ These criteria provide a sound foundation, but in clinical practice, patients often defy categorization.

The presence of pain in the area inferior to the posterior superior iliac spine and lateral to the gluteal fold with pain referral patterns in the L5-S1 nerve distributions is highly sensitive for identifying patients with SIJ dysfunction. Furthermore, pain arising from the SIJ will not be above the level of the L5 nerve sensory distribution. However, this diagnostic finding alone is not specific and might represent other etiologies known to produce similar pain, such as intervertebral discs and facet joints. Patients with SIJ dysfunction often describe their pain as sciatica-like, recurrent, and triggered with bending or twisting motions. It is worsened with any activity loading the SIJ, such as walking, climbing stairs, standing, or sitting upright. SIJ pain might be accompanied by dyspareunia and changes in bladder function because of the nerves involved.¹¹

The use of provocative maneuvers for testing SIJ dysfunction is controversial because of the high rate of false positives and the inability to distinguish whether the SIJ or an adjacent structure is affected. However, the diagnostic utility of specific stress tests has been studied, and clusters of tests are recommended if a health care provider (HCP) suspects SIJ dysfunction. A diagnostic algorithm should first focus on using the distraction test and the thigh thrust test. Distraction is done by applying vertically oriented pressure to the anterior superior iliac spine while aiming posteriorly, therefore distracting the SIJ. During the thigh thrust test the examiner fixates the patient’s sacrum against the table with the left hand and applies a vertical force through the line of the femur aiming posteriorly, producing a posterior shearing force at the SIJ. Studies show that the thigh thrust test is the most sensitive, and the distraction test is the most specific. If both tests are positive, there is reasonable evidence to suggest SIJ dysfunction as the source of LBP.

If there are not 2 positive results, the addition of the compression test, followed by the sacral thrust test also can point to the diagnosis. The compression test is performed with vertical downward force applied to the iliac crest with the patient lying on each side, compressing the SIJ by transverse pressure across the pelvis. The sacral thrust test is performed with vertical force applied to the midline posterior sacrum at its apex directed anteriorly with the patient lying prone, producing a shearing force at the SIJs. The Gaenslen test uses a torsion force by applying a superior and posterior force to the right knee and posteriorly directed force to the left knee. Omitting the Gaenslen test has not been shown to compromise diagnostic efficacy of the other tests and can be safely excluded.¹²

A HCP can rule out SIJ dysfunction if these provocation tests are negative. However, the diagnostic predictive value of these tests is subject to variability among HCPs, and their reliability is increased when used in clusters.^9,13

Imaging for the SIJ should begin with anterior/posterior, oblique, and lateral view plain X-rays of the pelvis (Figures 1 and 2), which will rule out other pathologies by identifying other sources of LBP, such as spondylolisthesis or hip osteoarthritis. HCPs should obtain lumbar and pelvis CT images to identify inflammatory or degenerative changes within the SIJ. CT images provide the high resolution that is needed to identify pathologies, such as fractures and tumors within the pelvic ring that could cause similar pain. MRI does not reliably depict a dysfunctional ligamentous apparatus within the SIJ; however, it can help identify inflammatory sacroiliitis, such as is seen in the spondyloarthropathies.^11,14 Recent studies show combined single photon emission tomography and CT (SPECT-CT) might be the most promising imaging modality to reveal mechanical failure of load transfer with increased scintigraphic uptake in the posterior and superior SIJ ligamentous attachments. The joint loses its characteristic “dumbbell” shape in affected patients with about 50% higher uptake than unaffected joints. These findings were evident in patients who experienced pelvic trauma or during the peripartum period.^15,16

Fluoroscopy-guided intra-articular injection of a local anesthetic (lidocaine) and/or a corticosteroid (triamcinolone) has the dual functionality of diagnosis and treatment (Figure 3). It often is considered the most reliable method to diagnose SIJ dysfunction and has the benefit of pain relief for up to 1 year. However, intra-articular injections lack diagnostic validity because the solution often extravasates to extracapsular structures. This confounds the source of the pain and makes it difficult to interpret these diagnostic injections. In addition, the injection might not reach the entire SIJ capsule and could result in a false-negative diagnosis.^17,18 Periarticular injections have been shown to result in better pain relief in patients diagnosed with SIJ dysfunction than intra-articular injections. Periarticular injections also are easier to perform and could be a first-step option for these patients.¹⁹

 

Treatment

Nonoperative management of SIJ dysfunction includes exercise programs, physical therapy, manual manipulation therapy, sacroiliac belts, and periodic articular injections. Efficacy of these methods is variable, and analgesics often do not significantly benefit this type of pain. Another nonoperative approach is radiofrequency ablation (RFA) of the lumbar dorsal rami and lateral sacral branches, which can vary based on the number of rami treated as well as the technique used. About two-thirds of patients report pain relief after RFA.2 When successful, pain is relieved for 6 to 12 months, which is a temporary yet effective option for patients experiencing SIJ dysfunction.^14,20

Fusion Surgery

Cadaver studies show that biomechanical stabilization of the SIJ leads to decreased range of motion in flexion/extension, lateral bending, and axial rotation. This results in a decreased need for periarticular muscular and ligamentous support, therefore facilitating load transfer across the SIJ.^21,22 Patients undergoing minimally invasive surgery report better pain relief compared with those receiving open surgery at 12 months postoperatively.²³ The 2 main SIJ fusion approaches used are the lateral transarticular and the dorsal approaches. In the dorsal approach, the SIJ is distracted and allograft dowels or titanium cages with graft are inserted into the joint space posteriorly through the back. When approaching laterally, hollow screw implants filled with graft or triangular titanium implants are placed across the joint, accessing the SIJ through the iliac bones using imaging guidance. This lateral transiliac approach using porous titanium triangular rods currently is the most studied technique.²⁴

A recent prospective, multicenter trial included 423 patients with SIJ dysfunction who were randomized to receive SIJ fusion with triangular titanium implants vs a control group who received nonoperative management. Patients in the SIJ fusion group showed substantially greater improvement in pain (81.4%) compared with that of the nonoperative group (26.1%) 6 months after surgery. Pain relief in the SIJ fusion group was maintained at > 80% at 1 and 2 year follow-up, while the nonoperative group’s pain relief decreased to < 10% at the follow-ups. Measures of quality of life and disability also improved for the SIJ fusion group compared with that of the nonoperative group. Patients who were crossed over from conservative management to SIJ fusion after 6 months demonstrated improvements that were similar to those in the SIJ fusion group by the end of the study. Only 3% of patients required surgical revision. The strongest predictor of pain relief after surgery was a diagnostic SIJ anesthetic block of 30 to 60 minutes, which resulted in > 75% pain reduction.^21,25 Additional predictors of successful SIJ fusion include nonsmokers, nonopioid users, and older patients who have a longer time course of SIJ pain.²⁶

Another study investigating the outcomes of SIJ fusion, RFA, and conservative management with a 6-year follow-up demonstrated similar results.²⁷ This further confirms the durability of the surgical group’s outcome, which sustained significant improvement compared with RFA and conservative management group in pain relief, daily function, and opioid use.

HCPs should consider SIJ fusion for patients who have at least 6 months of unsuccessful nonoperative management, significant SIJ pain (> 5 in a 10-point scale), ≥ 3 positive provocation tests, and at least 50% pain relief (> 75% preferred) with diagnostic intra-articular anesthetic injection.¹⁴ It is reasonable for primary care providers to refer these patients to a neurosurgeon or orthopedic spine surgeon for possible fusion. Patients with earlier lumbar/lumbosacral spinal fusions and persistent LBP should be evaluated for potential SIJ dysfunction. SIJ dysfunction after lumbosacral fusion could be considered a form of distal pseudarthrosis resulting from increased motion at the joint. One study found its incidence correlated with the number of segments fused in the lumbar spine.²⁸ Another study found that about one-third of patients with persistent LBP after lumbosacral fusion could be attributed to SIJ dysfunction.²⁹

 

Case Presentation

A 27-year-old female army veteran presented with bilateral buttock pain, which she described as a dull, aching pain across her sacral region, 8 out of 10 in severity. The pain was in a L5-S1 pattern. The pain was bilateral, with the right side worse than the left, and worsened with lateral bending and load transferring. She reported no numbness, tingling, or weakness.

On physical examination, she had full strength in her lower extremities and intact sensation. She reported tenderness to palpation of the sacrum and SIJ. Her gait was normal. The patient had positive thigh thrust and distraction tests. Lumbar spine X-ray, CT, MRI, and electromyographic studies did not show any pathology. She described little or no relief with analgesics or physical therapy. Previous L4-L5 and L5-S1 facet anesthetic injections and transforaminal epidural steroid injections provided minimal pain relief immediately after the procedures. Bilateral SIJ anesthetic injections under fluoroscopic guidance decreased her pain severity from a 7 to 3 out of 10 for 2 to 3 months before returning to her baseline. Radiofrequency ablation of the right SIJ under fluoroscopy provided moderate relief for about 4 months.

After exhausting nonoperative management for SIJ dysfunction without adequate pain control, the patient was referred to neurosurgery for surgical fusion. The patient was deemed an appropriate surgical candidate and underwent a right-sided SIJ fusion (Figures 4 and 5). At her 6-month and 1-year follow-up appointments, she had lasting pain relief, 2 out of 10.

Conclusion

SIJ dysfunction is widely overlooked because of the difficulty in distinguishing it from other similarly presenting syndromes. However, with a detailed history, appropriate physical maneuvers, imaging, and adequate response to intra-articular anesthetic, providers can reach an accurate diagnosis that will inform subsequent treatments. After failure of nonsurgical methods, patients with SIJ dysfunction should be considered for minimally invasive fusion techniques, which have proven to be a safe, effective, and viable treatment option.

Patients experiencing sacroiliac joint (SIJ) dysfunction might show symptoms that overlap with those seen in lumbar spine pathology. This article reviews diagnostic tools that assist practitioners to discern the true pain generator in patients with low back pain (LBP) and therapeutic approaches when the cause is SIJ dysfunction.

Prevalence

Most of the US population will experience LBP at some point in their lives. A 2002 National Health Interview survey found that more than one-quarter (26.4%) of 31 044 respondents had complained of LBP in the previous 3 months.¹ About 74 million individuals in the US experienced LBP in the past 3 months.¹ A full 10% of the US population is expected to suffer from chronic LBP, and it is estimated that 2.3% of all visits to physicians are related to LBP.¹

The etiology of LBP often is unclear even after thorough clinical and radiographic evaluation because of the myriad possible mechanisms. Degenerative disc disease, facet arthropathy, ligamentous hypertrophy, muscle spasm, hip arthropathy, and SIJ dysfunction are potential pain generators and exact clinical and radiographic correlation is not always possible. Compounding this difficulty is the lack of specificity with current diagnostic techniques. For example, many patients will have disc desiccation or herniation without any LBP or radicular symptoms on radiographic studies, such as X-rays, computed tomography (CT), and magnetic resonance imaging (MRI). As such, providers of patients with diffuse radiographic abnormalities often have to identify a specific pain generator, which might not have any role in the patient’s pain.

Other tests, such as electromyographic studies, positron emission tomography (PET) scans, discography, and epidural steroid injections, can help pinpoint a specific pain generator. These tests might help determine whether the patient has a surgically treatable condition and could help predict whether a patient’s symptoms will respond to surgery.

However, the standard spine surgery workup often fails to identify an obvious pain generator in many individuals. The significant number of patients that fall into this category has prompted spine surgeons to consider other potential etiologies for LBP, and SIJ dysfunction has become a rapidly developing field of research.

Sacroiliac Joint Dysfunction

The SIJ is a bilateral, C-shaped synovial joint surrounded by a fibrous capsule and affixes the sacrum to the ilia. Several sacral ligaments and pelvic muscles support the SIJ. The L5 nerve ventral ramus and lumbosacral trunk pass anteriorly and the S1 nerve ventral ramus passes inferiorly to the joint capsule. The SIJ is innervated by the dorsal rami of L4-S3 nerve roots, transmitting nociception and temperature. Mechanisms of injury to the SIJ could arise from intra- and extra-articular etiologies, including capsular disruption, ligamentous tension, muscular inflammation, shearing, fractures, arthritis, and infection.² Patients could develop SIJ pain spontaneously or after a traumatic event or repetitive shear.³ Risk factors for developing SIJ dysfunction include a history of lumbar fusion, scoliosis, leg length discrepancies, sustained athletic activity, pregnancy, seronegative HLA-B27 spondyloarthropathies, or gait abnormalities. Inflammation of the SIJ and surrounding structures secondary to an environmental insult in susceptible individuals is a common theme among these etiologies.²

 

Pain from the SIJ is localized to an area of approximately 3 cm × 10 cm that is inferior to the ipsilateral posterior superior iliac spine.⁴ Referred pain maps from SIJ dysfunction extend in the L5-S1 nerve distributions, commonly seen in the buttocks, groin, posterior thigh, and lower leg with radicular symptoms. However, this pain distribution demonstrates extensive variability among patients and bears strong similarities to discogenic or facet joint sources of LBP.^5-7 Direct communication has been shown between the SIJ and adjacent neural structures, namely the L5 nerve, sacral foramina, and the lumbosacral plexus. These direct pathways could explain an inflammatory mechanism for lower extremity symptoms seen in SIJ dysfunction.⁸

The prevalence of SIJ dysfunction among patients with LBP is estimated to be 15% to 30%, an extraordinary number given the total number of patients presenting with LBP every year.⁹ These patients might represent a significant segment of patients with an unrevealing standard spine evaluation. Despite the large number of patients who experience SIJ dysfunction, there is disagreement about optimal methods for diagnosis and treatment.

Diagnosis

The International Association for the Study of Pain has proposed criteria for evaluating patients who have suspected SIJ dysfunction: Pain must be in the SIJ area, should be reproducible by performing specific provocative maneuvers, and must be relieved by injection of local anesthetic into the SIJ.¹⁰ These criteria provide a sound foundation, but in clinical practice, patients often defy categorization.

The presence of pain in the area inferior to the posterior superior iliac spine and lateral to the gluteal fold with pain referral patterns in the L5-S1 nerve distributions is highly sensitive for identifying patients with SIJ dysfunction. Furthermore, pain arising from the SIJ will not be above the level of the L5 nerve sensory distribution. However, this diagnostic finding alone is not specific and might represent other etiologies known to produce similar pain, such as intervertebral discs and facet joints. Patients with SIJ dysfunction often describe their pain as sciatica-like, recurrent, and triggered with bending or twisting motions. It is worsened with any activity loading the SIJ, such as walking, climbing stairs, standing, or sitting upright. SIJ pain might be accompanied by dyspareunia and changes in bladder function because of the nerves involved.¹¹

The use of provocative maneuvers for testing SIJ dysfunction is controversial because of the high rate of false positives and the inability to distinguish whether the SIJ or an adjacent structure is affected. However, the diagnostic utility of specific stress tests has been studied, and clusters of tests are recommended if a health care provider (HCP) suspects SIJ dysfunction. A diagnostic algorithm should first focus on using the distraction test and the thigh thrust test. Distraction is done by applying vertically oriented pressure to the anterior superior iliac spine while aiming posteriorly, therefore distracting the SIJ. During the thigh thrust test the examiner fixates the patient’s sacrum against the table with the left hand and applies a vertical force through the line of the femur aiming posteriorly, producing a posterior shearing force at the SIJ. Studies show that the thigh thrust test is the most sensitive, and the distraction test is the most specific. If both tests are positive, there is reasonable evidence to suggest SIJ dysfunction as the source of LBP.

If there are not 2 positive results, the addition of the compression test, followed by the sacral thrust test also can point to the diagnosis. The compression test is performed with vertical downward force applied to the iliac crest with the patient lying on each side, compressing the SIJ by transverse pressure across the pelvis. The sacral thrust test is performed with vertical force applied to the midline posterior sacrum at its apex directed anteriorly with the patient lying prone, producing a shearing force at the SIJs. The Gaenslen test uses a torsion force by applying a superior and posterior force to the right knee and posteriorly directed force to the left knee. Omitting the Gaenslen test has not been shown to compromise diagnostic efficacy of the other tests and can be safely excluded.¹²

A HCP can rule out SIJ dysfunction if these provocation tests are negative. However, the diagnostic predictive value of these tests is subject to variability among HCPs, and their reliability is increased when used in clusters.^9,13

Imaging for the SIJ should begin with anterior/posterior, oblique, and lateral view plain X-rays of the pelvis (Figures 1 and 2), which will rule out other pathologies by identifying other sources of LBP, such as spondylolisthesis or hip osteoarthritis. HCPs should obtain lumbar and pelvis CT images to identify inflammatory or degenerative changes within the SIJ. CT images provide the high resolution that is needed to identify pathologies, such as fractures and tumors within the pelvic ring that could cause similar pain. MRI does not reliably depict a dysfunctional ligamentous apparatus within the SIJ; however, it can help identify inflammatory sacroiliitis, such as is seen in the spondyloarthropathies.^11,14 Recent studies show combined single photon emission tomography and CT (SPECT-CT) might be the most promising imaging modality to reveal mechanical failure of load transfer with increased scintigraphic uptake in the posterior and superior SIJ ligamentous attachments. The joint loses its characteristic “dumbbell” shape in affected patients with about 50% higher uptake than unaffected joints. These findings were evident in patients who experienced pelvic trauma or during the peripartum period.^15,16

Fluoroscopy-guided intra-articular injection of a local anesthetic (lidocaine) and/or a corticosteroid (triamcinolone) has the dual functionality of diagnosis and treatment (Figure 3). It often is considered the most reliable method to diagnose SIJ dysfunction and has the benefit of pain relief for up to 1 year. However, intra-articular injections lack diagnostic validity because the solution often extravasates to extracapsular structures. This confounds the source of the pain and makes it difficult to interpret these diagnostic injections. In addition, the injection might not reach the entire SIJ capsule and could result in a false-negative diagnosis.^17,18 Periarticular injections have been shown to result in better pain relief in patients diagnosed with SIJ dysfunction than intra-articular injections. Periarticular injections also are easier to perform and could be a first-step option for these patients.¹⁹

 

Treatment

Nonoperative management of SIJ dysfunction includes exercise programs, physical therapy, manual manipulation therapy, sacroiliac belts, and periodic articular injections. Efficacy of these methods is variable, and analgesics often do not significantly benefit this type of pain. Another nonoperative approach is radiofrequency ablation (RFA) of the lumbar dorsal rami and lateral sacral branches, which can vary based on the number of rami treated as well as the technique used. About two-thirds of patients report pain relief after RFA.2 When successful, pain is relieved for 6 to 12 months, which is a temporary yet effective option for patients experiencing SIJ dysfunction.^14,20

Fusion Surgery

Cadaver studies show that biomechanical stabilization of the SIJ leads to decreased range of motion in flexion/extension, lateral bending, and axial rotation. This results in a decreased need for periarticular muscular and ligamentous support, therefore facilitating load transfer across the SIJ.^21,22 Patients undergoing minimally invasive surgery report better pain relief compared with those receiving open surgery at 12 months postoperatively.²³ The 2 main SIJ fusion approaches used are the lateral transarticular and the dorsal approaches. In the dorsal approach, the SIJ is distracted and allograft dowels or titanium cages with graft are inserted into the joint space posteriorly through the back. When approaching laterally, hollow screw implants filled with graft or triangular titanium implants are placed across the joint, accessing the SIJ through the iliac bones using imaging guidance. This lateral transiliac approach using porous titanium triangular rods currently is the most studied technique.²⁴

A recent prospective, multicenter trial included 423 patients with SIJ dysfunction who were randomized to receive SIJ fusion with triangular titanium implants vs a control group who received nonoperative management. Patients in the SIJ fusion group showed substantially greater improvement in pain (81.4%) compared with that of the nonoperative group (26.1%) 6 months after surgery. Pain relief in the SIJ fusion group was maintained at > 80% at 1 and 2 year follow-up, while the nonoperative group’s pain relief decreased to < 10% at the follow-ups. Measures of quality of life and disability also improved for the SIJ fusion group compared with that of the nonoperative group. Patients who were crossed over from conservative management to SIJ fusion after 6 months demonstrated improvements that were similar to those in the SIJ fusion group by the end of the study. Only 3% of patients required surgical revision. The strongest predictor of pain relief after surgery was a diagnostic SIJ anesthetic block of 30 to 60 minutes, which resulted in > 75% pain reduction.^21,25 Additional predictors of successful SIJ fusion include nonsmokers, nonopioid users, and older patients who have a longer time course of SIJ pain.²⁶

Another study investigating the outcomes of SIJ fusion, RFA, and conservative management with a 6-year follow-up demonstrated similar results.²⁷ This further confirms the durability of the surgical group’s outcome, which sustained significant improvement compared with RFA and conservative management group in pain relief, daily function, and opioid use.

HCPs should consider SIJ fusion for patients who have at least 6 months of unsuccessful nonoperative management, significant SIJ pain (> 5 in a 10-point scale), ≥ 3 positive provocation tests, and at least 50% pain relief (> 75% preferred) with diagnostic intra-articular anesthetic injection.¹⁴ It is reasonable for primary care providers to refer these patients to a neurosurgeon or orthopedic spine surgeon for possible fusion. Patients with earlier lumbar/lumbosacral spinal fusions and persistent LBP should be evaluated for potential SIJ dysfunction. SIJ dysfunction after lumbosacral fusion could be considered a form of distal pseudarthrosis resulting from increased motion at the joint. One study found its incidence correlated with the number of segments fused in the lumbar spine.²⁸ Another study found that about one-third of patients with persistent LBP after lumbosacral fusion could be attributed to SIJ dysfunction.²⁹

 

Case Presentation

A 27-year-old female army veteran presented with bilateral buttock pain, which she described as a dull, aching pain across her sacral region, 8 out of 10 in severity. The pain was in a L5-S1 pattern. The pain was bilateral, with the right side worse than the left, and worsened with lateral bending and load transferring. She reported no numbness, tingling, or weakness.

On physical examination, she had full strength in her lower extremities and intact sensation. She reported tenderness to palpation of the sacrum and SIJ. Her gait was normal. The patient had positive thigh thrust and distraction tests. Lumbar spine X-ray, CT, MRI, and electromyographic studies did not show any pathology. She described little or no relief with analgesics or physical therapy. Previous L4-L5 and L5-S1 facet anesthetic injections and transforaminal epidural steroid injections provided minimal pain relief immediately after the procedures. Bilateral SIJ anesthetic injections under fluoroscopic guidance decreased her pain severity from a 7 to 3 out of 10 for 2 to 3 months before returning to her baseline. Radiofrequency ablation of the right SIJ under fluoroscopy provided moderate relief for about 4 months.

After exhausting nonoperative management for SIJ dysfunction without adequate pain control, the patient was referred to neurosurgery for surgical fusion. The patient was deemed an appropriate surgical candidate and underwent a right-sided SIJ fusion (Figures 4 and 5). At her 6-month and 1-year follow-up appointments, she had lasting pain relief, 2 out of 10.

Conclusion

SIJ dysfunction is widely overlooked because of the difficulty in distinguishing it from other similarly presenting syndromes. However, with a detailed history, appropriate physical maneuvers, imaging, and adequate response to intra-articular anesthetic, providers can reach an accurate diagnosis that will inform subsequent treatments. After failure of nonsurgical methods, patients with SIJ dysfunction should be considered for minimally invasive fusion techniques, which have proven to be a safe, effective, and viable treatment option.

Patients experiencing sacroiliac joint (SIJ) dysfunction might show symptoms that overlap with those seen in lumbar spine pathology. This article reviews diagnostic tools that assist practitioners to discern the true pain generator in patients with low back pain (LBP) and therapeutic approaches when the cause is SIJ dysfunction.

Prevalence

Most of the US population will experience LBP at some point in their lives. A 2002 National Health Interview survey found that more than one-quarter (26.4%) of 31 044 respondents had complained of LBP in the previous 3 months.¹ About 74 million individuals in the US experienced LBP in the past 3 months.¹ A full 10% of the US population is expected to suffer from chronic LBP, and it is estimated that 2.3% of all visits to physicians are related to LBP.¹

The etiology of LBP often is unclear even after thorough clinical and radiographic evaluation because of the myriad possible mechanisms. Degenerative disc disease, facet arthropathy, ligamentous hypertrophy, muscle spasm, hip arthropathy, and SIJ dysfunction are potential pain generators and exact clinical and radiographic correlation is not always possible. Compounding this difficulty is the lack of specificity with current diagnostic techniques. For example, many patients will have disc desiccation or herniation without any LBP or radicular symptoms on radiographic studies, such as X-rays, computed tomography (CT), and magnetic resonance imaging (MRI). As such, providers of patients with diffuse radiographic abnormalities often have to identify a specific pain generator, which might not have any role in the patient’s pain.

Other tests, such as electromyographic studies, positron emission tomography (PET) scans, discography, and epidural steroid injections, can help pinpoint a specific pain generator. These tests might help determine whether the patient has a surgically treatable condition and could help predict whether a patient’s symptoms will respond to surgery.

However, the standard spine surgery workup often fails to identify an obvious pain generator in many individuals. The significant number of patients that fall into this category has prompted spine surgeons to consider other potential etiologies for LBP, and SIJ dysfunction has become a rapidly developing field of research.

Sacroiliac Joint Dysfunction

The SIJ is a bilateral, C-shaped synovial joint surrounded by a fibrous capsule and affixes the sacrum to the ilia. Several sacral ligaments and pelvic muscles support the SIJ. The L5 nerve ventral ramus and lumbosacral trunk pass anteriorly and the S1 nerve ventral ramus passes inferiorly to the joint capsule. The SIJ is innervated by the dorsal rami of L4-S3 nerve roots, transmitting nociception and temperature. Mechanisms of injury to the SIJ could arise from intra- and extra-articular etiologies, including capsular disruption, ligamentous tension, muscular inflammation, shearing, fractures, arthritis, and infection.² Patients could develop SIJ pain spontaneously or after a traumatic event or repetitive shear.³ Risk factors for developing SIJ dysfunction include a history of lumbar fusion, scoliosis, leg length discrepancies, sustained athletic activity, pregnancy, seronegative HLA-B27 spondyloarthropathies, or gait abnormalities. Inflammation of the SIJ and surrounding structures secondary to an environmental insult in susceptible individuals is a common theme among these etiologies.²

 

Pain from the SIJ is localized to an area of approximately 3 cm × 10 cm that is inferior to the ipsilateral posterior superior iliac spine.⁴ Referred pain maps from SIJ dysfunction extend in the L5-S1 nerve distributions, commonly seen in the buttocks, groin, posterior thigh, and lower leg with radicular symptoms. However, this pain distribution demonstrates extensive variability among patients and bears strong similarities to discogenic or facet joint sources of LBP.^5-7 Direct communication has been shown between the SIJ and adjacent neural structures, namely the L5 nerve, sacral foramina, and the lumbosacral plexus. These direct pathways could explain an inflammatory mechanism for lower extremity symptoms seen in SIJ dysfunction.⁸

The prevalence of SIJ dysfunction among patients with LBP is estimated to be 15% to 30%, an extraordinary number given the total number of patients presenting with LBP every year.⁹ These patients might represent a significant segment of patients with an unrevealing standard spine evaluation. Despite the large number of patients who experience SIJ dysfunction, there is disagreement about optimal methods for diagnosis and treatment.

Diagnosis

The International Association for the Study of Pain has proposed criteria for evaluating patients who have suspected SIJ dysfunction: Pain must be in the SIJ area, should be reproducible by performing specific provocative maneuvers, and must be relieved by injection of local anesthetic into the SIJ.¹⁰ These criteria provide a sound foundation, but in clinical practice, patients often defy categorization.

The presence of pain in the area inferior to the posterior superior iliac spine and lateral to the gluteal fold with pain referral patterns in the L5-S1 nerve distributions is highly sensitive for identifying patients with SIJ dysfunction. Furthermore, pain arising from the SIJ will not be above the level of the L5 nerve sensory distribution. However, this diagnostic finding alone is not specific and might represent other etiologies known to produce similar pain, such as intervertebral discs and facet joints. Patients with SIJ dysfunction often describe their pain as sciatica-like, recurrent, and triggered with bending or twisting motions. It is worsened with any activity loading the SIJ, such as walking, climbing stairs, standing, or sitting upright. SIJ pain might be accompanied by dyspareunia and changes in bladder function because of the nerves involved.¹¹

The use of provocative maneuvers for testing SIJ dysfunction is controversial because of the high rate of false positives and the inability to distinguish whether the SIJ or an adjacent structure is affected. However, the diagnostic utility of specific stress tests has been studied, and clusters of tests are recommended if a health care provider (HCP) suspects SIJ dysfunction. A diagnostic algorithm should first focus on using the distraction test and the thigh thrust test. Distraction is done by applying vertically oriented pressure to the anterior superior iliac spine while aiming posteriorly, therefore distracting the SIJ. During the thigh thrust test the examiner fixates the patient’s sacrum against the table with the left hand and applies a vertical force through the line of the femur aiming posteriorly, producing a posterior shearing force at the SIJ. Studies show that the thigh thrust test is the most sensitive, and the distraction test is the most specific. If both tests are positive, there is reasonable evidence to suggest SIJ dysfunction as the source of LBP.

If there are not 2 positive results, the addition of the compression test, followed by the sacral thrust test also can point to the diagnosis. The compression test is performed with vertical downward force applied to the iliac crest with the patient lying on each side, compressing the SIJ by transverse pressure across the pelvis. The sacral thrust test is performed with vertical force applied to the midline posterior sacrum at its apex directed anteriorly with the patient lying prone, producing a shearing force at the SIJs. The Gaenslen test uses a torsion force by applying a superior and posterior force to the right knee and posteriorly directed force to the left knee. Omitting the Gaenslen test has not been shown to compromise diagnostic efficacy of the other tests and can be safely excluded.¹²

A HCP can rule out SIJ dysfunction if these provocation tests are negative. However, the diagnostic predictive value of these tests is subject to variability among HCPs, and their reliability is increased when used in clusters.^9,13

Imaging for the SIJ should begin with anterior/posterior, oblique, and lateral view plain X-rays of the pelvis (Figures 1 and 2), which will rule out other pathologies by identifying other sources of LBP, such as spondylolisthesis or hip osteoarthritis. HCPs should obtain lumbar and pelvis CT images to identify inflammatory or degenerative changes within the SIJ. CT images provide the high resolution that is needed to identify pathologies, such as fractures and tumors within the pelvic ring that could cause similar pain. MRI does not reliably depict a dysfunctional ligamentous apparatus within the SIJ; however, it can help identify inflammatory sacroiliitis, such as is seen in the spondyloarthropathies.^11,14 Recent studies show combined single photon emission tomography and CT (SPECT-CT) might be the most promising imaging modality to reveal mechanical failure of load transfer with increased scintigraphic uptake in the posterior and superior SIJ ligamentous attachments. The joint loses its characteristic “dumbbell” shape in affected patients with about 50% higher uptake than unaffected joints. These findings were evident in patients who experienced pelvic trauma or during the peripartum period.^15,16

Fluoroscopy-guided intra-articular injection of a local anesthetic (lidocaine) and/or a corticosteroid (triamcinolone) has the dual functionality of diagnosis and treatment (Figure 3). It often is considered the most reliable method to diagnose SIJ dysfunction and has the benefit of pain relief for up to 1 year. However, intra-articular injections lack diagnostic validity because the solution often extravasates to extracapsular structures. This confounds the source of the pain and makes it difficult to interpret these diagnostic injections. In addition, the injection might not reach the entire SIJ capsule and could result in a false-negative diagnosis.^17,18 Periarticular injections have been shown to result in better pain relief in patients diagnosed with SIJ dysfunction than intra-articular injections. Periarticular injections also are easier to perform and could be a first-step option for these patients.¹⁹

 

Treatment

Nonoperative management of SIJ dysfunction includes exercise programs, physical therapy, manual manipulation therapy, sacroiliac belts, and periodic articular injections. Efficacy of these methods is variable, and analgesics often do not significantly benefit this type of pain. Another nonoperative approach is radiofrequency ablation (RFA) of the lumbar dorsal rami and lateral sacral branches, which can vary based on the number of rami treated as well as the technique used. About two-thirds of patients report pain relief after RFA.2 When successful, pain is relieved for 6 to 12 months, which is a temporary yet effective option for patients experiencing SIJ dysfunction.^14,20

Fusion Surgery

Cadaver studies show that biomechanical stabilization of the SIJ leads to decreased range of motion in flexion/extension, lateral bending, and axial rotation. This results in a decreased need for periarticular muscular and ligamentous support, therefore facilitating load transfer across the SIJ.^21,22 Patients undergoing minimally invasive surgery report better pain relief compared with those receiving open surgery at 12 months postoperatively.²³ The 2 main SIJ fusion approaches used are the lateral transarticular and the dorsal approaches. In the dorsal approach, the SIJ is distracted and allograft dowels or titanium cages with graft are inserted into the joint space posteriorly through the back. When approaching laterally, hollow screw implants filled with graft or triangular titanium implants are placed across the joint, accessing the SIJ through the iliac bones using imaging guidance. This lateral transiliac approach using porous titanium triangular rods currently is the most studied technique.²⁴

A recent prospective, multicenter trial included 423 patients with SIJ dysfunction who were randomized to receive SIJ fusion with triangular titanium implants vs a control group who received nonoperative management. Patients in the SIJ fusion group showed substantially greater improvement in pain (81.4%) compared with that of the nonoperative group (26.1%) 6 months after surgery. Pain relief in the SIJ fusion group was maintained at > 80% at 1 and 2 year follow-up, while the nonoperative group’s pain relief decreased to < 10% at the follow-ups. Measures of quality of life and disability also improved for the SIJ fusion group compared with that of the nonoperative group. Patients who were crossed over from conservative management to SIJ fusion after 6 months demonstrated improvements that were similar to those in the SIJ fusion group by the end of the study. Only 3% of patients required surgical revision. The strongest predictor of pain relief after surgery was a diagnostic SIJ anesthetic block of 30 to 60 minutes, which resulted in > 75% pain reduction.^21,25 Additional predictors of successful SIJ fusion include nonsmokers, nonopioid users, and older patients who have a longer time course of SIJ pain.²⁶

Another study investigating the outcomes of SIJ fusion, RFA, and conservative management with a 6-year follow-up demonstrated similar results.²⁷ This further confirms the durability of the surgical group’s outcome, which sustained significant improvement compared with RFA and conservative management group in pain relief, daily function, and opioid use.

HCPs should consider SIJ fusion for patients who have at least 6 months of unsuccessful nonoperative management, significant SIJ pain (> 5 in a 10-point scale), ≥ 3 positive provocation tests, and at least 50% pain relief (> 75% preferred) with diagnostic intra-articular anesthetic injection.¹⁴ It is reasonable for primary care providers to refer these patients to a neurosurgeon or orthopedic spine surgeon for possible fusion. Patients with earlier lumbar/lumbosacral spinal fusions and persistent LBP should be evaluated for potential SIJ dysfunction. SIJ dysfunction after lumbosacral fusion could be considered a form of distal pseudarthrosis resulting from increased motion at the joint. One study found its incidence correlated with the number of segments fused in the lumbar spine.²⁸ Another study found that about one-third of patients with persistent LBP after lumbosacral fusion could be attributed to SIJ dysfunction.²⁹

 

Case Presentation

A 27-year-old female army veteran presented with bilateral buttock pain, which she described as a dull, aching pain across her sacral region, 8 out of 10 in severity. The pain was in a L5-S1 pattern. The pain was bilateral, with the right side worse than the left, and worsened with lateral bending and load transferring. She reported no numbness, tingling, or weakness.

On physical examination, she had full strength in her lower extremities and intact sensation. She reported tenderness to palpation of the sacrum and SIJ. Her gait was normal. The patient had positive thigh thrust and distraction tests. Lumbar spine X-ray, CT, MRI, and electromyographic studies did not show any pathology. She described little or no relief with analgesics or physical therapy. Previous L4-L5 and L5-S1 facet anesthetic injections and transforaminal epidural steroid injections provided minimal pain relief immediately after the procedures. Bilateral SIJ anesthetic injections under fluoroscopic guidance decreased her pain severity from a 7 to 3 out of 10 for 2 to 3 months before returning to her baseline. Radiofrequency ablation of the right SIJ under fluoroscopy provided moderate relief for about 4 months.

After exhausting nonoperative management for SIJ dysfunction without adequate pain control, the patient was referred to neurosurgery for surgical fusion. The patient was deemed an appropriate surgical candidate and underwent a right-sided SIJ fusion (Figures 4 and 5). At her 6-month and 1-year follow-up appointments, she had lasting pain relief, 2 out of 10.

Conclusion

SIJ dysfunction is widely overlooked because of the difficulty in distinguishing it from other similarly presenting syndromes. However, with a detailed history, appropriate physical maneuvers, imaging, and adequate response to intra-articular anesthetic, providers can reach an accurate diagnosis that will inform subsequent treatments. After failure of nonsurgical methods, patients with SIJ dysfunction should be considered for minimally invasive fusion techniques, which have proven to be a safe, effective, and viable treatment option.

ANSWER

The radiograph demonstrates no evidence of an acute fracture or soft-tissue gas to suggest an abscess. Of note, though, within the tibiotalar joint, the patient has bony destruction and settling of the articular surfaces of both the distal tibia and fibula into the talus and calcaneus.

This finding is typically associated with neuropathic arthropathy (also known as a Charcot joint). This pathologic process is typically seen in a weight-bearing joint that develops progressive degeneration from chronic loss of sensation.

ANSWER

The radiograph demonstrates no evidence of an acute fracture or soft-tissue gas to suggest an abscess. Of note, though, within the tibiotalar joint, the patient has bony destruction and settling of the articular surfaces of both the distal tibia and fibula into the talus and calcaneus.

This finding is typically associated with neuropathic arthropathy (also known as a Charcot joint). This pathologic process is typically seen in a weight-bearing joint that develops progressive degeneration from chronic loss of sensation.

ANSWER

The radiograph demonstrates no evidence of an acute fracture or soft-tissue gas to suggest an abscess. Of note, though, within the tibiotalar joint, the patient has bony destruction and settling of the articular surfaces of both the distal tibia and fibula into the talus and calcaneus.

This finding is typically associated with neuropathic arthropathy (also known as a Charcot joint). This pathologic process is typically seen in a weight-bearing joint that develops progressive degeneration from chronic loss of sensation.

Hip injections are performed as diagnostic and therapeutic interventions across a variety of medical subspecialties, including but not limited to those practicing physical medicine and rehabilitation, pain medicine, sports medicine, orthopedic surgery, and radiology. Traditional image-guided intra-articular hip injection commonly uses an anterior-oblique approach from a starting point on the anterior groin traversing soft tissue anterior to the femoral neck to the target needle placement at the femoral head-neck junction.

In fluoroscopic procedures, a coaxial technique for needles placement is used for safe and precise insertion of needles. An X-ray beam is angled in line with the projected path of the needle from skin entry point to injection target. Coaxial, en face technique (also called EF, parallel, hub view, down the barrel, or barrel view) appears as a single radiopaque dot over the target injection site.¹ This technique minimizes needle redirection for correction of the injection path and minimal disturbance of surrounding tissue on the approach to the intended target.

Noncoaxial technique, as used in the anterior-oblique approach, intentionally directs the needle away from a skin entry point, the needle barrel traversing the X-ray beam toward an injection target. Clinical challenges to injection with the anterior-oblique approach include using a noncoaxial technique. Additional challenges to the anterior-oblique (also referred to as anterior) approach are body habitus and pannus, proximity to neurovascular structures, and patient positioning. By understanding the risks and benefits of varied technical approaches to accomplish a clinical goal and outcome, trainees are better able to select the technique most appropriate for a varied patient population.

Common risks to patients for all intra-articular interventions include bleeding, infection, and pain. Risk of damage to nearby structures is often mentioned as part of a standard informed consent process as it relates to the femoral vein, artery, and nerve that are in close anatomical proximity to the target injection site. When prior studies have examined the risk of complications resulting from intra-articular hip injections, a common conclusion is that despite a relatively low-risk profile for skilled interventionalists, efforts to avoid needle placement in the medial 50% of the femoral head on antero-posterior imaging is recommended.²

The anterior technique is a commonly described approach, and the same can be used for both ultrasound-guided and fluoroscopically guided hip injections.³ Using ultrasound guidance, the anterior technique can be performed with in-plane direct visualization of the needle throughout the procedure. With fluoroscopic guidance, the anterior approach is performed out-of-plane, using the noncoaxial technique. This requires the interventionalist to use tactile and anatomic guidance to the target injection site. The anterior approach for hip injection is one of few interventions where coaxial technique is not used for the procedure, making the instruction for a learner less concrete and potentially more challenging related to the needle path not under direct visualization in plane with the X-ray beam.

Technical guidance and detailed instruction for the lateral approach is infrequently described in fluoroscopic interventional texts. Reference to a lateral approach hip injection was made as early as the 1970s, without detail provided on the technique, with respect to the advantage of visualization of the hip joint for needle placement when hardware is in place.⁴ A more recent article described a lateral approach technique involving the patient in a decubitus (lateral) supine position, which presents limitations in consistent fluoroscopic imaging and can be a challenging static position for the patient to maintain.⁵

The retrospective review of anterior-oblique and lateral approach procedures in this study aims to demonstrate that there is no significant difference in radiation exposure, rate of successful intra-articular injection, or complication rate. If proven as a noninferior technique, the lateral approach may be a valuable interventional skill to those performing hip injections. Potential benefits to the patient and provider include options for the provider to access the joint using either technique. Additionally, the approach can be added to the instructional plan for those practitioners providing technical instruction to trainees within their health care system.

 

Methods

The institutional review board at the VA Ann Arbor Healthcare System reviewed and granted approval for this study. One of 5 interventional pain physician staff members at the VA Ann Arbor Healthcare System performed fluoroscopically guided hip injections. Interventional pain fellows under the direct supervision of board-certified physicians performed the procedures for the study cases. Supervising physicians included both physiatrists and anesthesiologists. Images were reviewed and evaluated without corresponding patient biographic data.

For cases using the lateral approach, the patients were positioned supine on the fluoroscopy table. In anterior-posterior and lateral views, trajectory lines are drawn using a long metal marking rod held adjacent to the patient. With pulsed low-dose fluoroscopy, transverse lines are drawn to identify midpoint of the femoral head in lateral view (Figure 1A, x-axis) and the most direct line from skin to lateral femoral head neck junction joint target (Figure 1B, z-axis). Also confirmed in lateral view, the z-axis marked line drawn on the skin is used to confirm that this transverse plane crosses the overlapping femoral heads (Figure 1A, y-axis).

The cross-section of these transverse and coronal plane lines identifies the starting point for the most direct approach from skin to injection target at femoral head-neck junction. Using the coaxial technique in the lateral view, the needle is introduced and advanced using intermittent fluoroscopic images to the lateral joint target. Continuing in this view, the interventionalist can ensure that advancing the needle to the osseous endpoint will place the tip at the midpoint of the femoral head at the target on the lateral surface, avoiding inadvertent advance of the needle anterior or posterior the femoral head. Final needle placement confirmation is then completed in antero-posterior view (Figure 2A). Contrast enhancement is used to confirm intra-articular spread (Figure 2B).

Cases included in the study were performed over an 8-month period in 2017. Case images recorded in IntelliSpace PACS Radiology software (Andover, MA) were included by creating a list of all cases performed and documented using the major joint injection procedure code. The cases reviewed began with the most recent cases. Two research team members (1 radiologist and 1 interventional pain physician) reviewed the series of saved images for each patient and the associated procedure report. The research team members documented and recorded de-identified study data in Microsoft Excel (Redmond, WA).

Imaging reports, using the saved images and the associated procedure report, were classified for technical approach (anterior, lateral, or inconclusive), success of joint injection as evidenced by appropriate contrast enhancement within the joint space (successful, unsuccessful, or incomplete images), documented use of sedation (yes, no), patient positioning (supine, prone), radiation exposure dose, radiation exposure time, and additional comments, such as “notable pannus” or “hardware present” to annotate significant findings on imaging review.

Statistical Analysis

The distribution of 2 outcomes used to compare rates of complication, radiation dose, and exposure time was checked using the Shapiro-Wilk test. Power analysis determined that inclusion of 30 anterior and 30 lateral cases results in adequate power to detect a 1-point mean difference, assuming a standard deviation of 1.5 in each group. Both radiation dose and exposure time were found to be nonnormally distributed (W = 0.65, P < .001; W = 0.86, P < .001; respectively). Median and interquartile range (IQR) of dose and time in seconds for anterior and lateral approaches were computed. Median differences in radiation dose and exposure time between anterior and lateral approaches were assessed with the k-sample test of equality of medians. All analyses were conducted using Stata Version 14.1 (College Station, TX).

 

Results

Between June 2017 and January 2018, 88 cases were reviewed as performed, with 30 anterior and 30 lateral approach cases included in this retrospective comparison study. A total of 28 cases were excluded from the study for using an inconclusive approach, multiple or bilateral procedures, cases without recorded dose and time data, and inadequately saved images to provide meaningful data (Figure 3).

Rate of successful intervention with needle placement confirmed within the articular space on contrast enhancement was not significantly different in the study groups with 96.7% (29 of 30) anterior approach cases reported as successful, 100% (30 of 30) lateral approach cases reported as successful. Overhanging pannus in the viewing area was reported in 5 anterior approach cases and 4 lateral cases. Hardware was noted in 2 lateral approach cases, none in anterior approach cases. Sedation was used for 3 of the anterior approach cases and none of the lateral approach cases.

Patients undergoing the lateral approach received a higher median radiation dose than did those undergoing the anterior approach, but this was not statistically significant (P = .07) (Table). Those undergoing the lateral approach also had a longer median exposure time than did those undergoing the anterior approach, but this also was not statistically significant (P = .3). With no immediate complications reported in any of the studied interventions, there was no difference in complication rates between anterior and lateral approach cases.

Discussion

Pain medicine fellows who have previously completed residency in a variety of disciplines, often either anesthesiology or physical medicine and rehabilitation, perform fluoroscopically guided procedures and benefit from increased experience with coaxial technique as this improves needle depth and location awareness. Once mastered, this skill set can be applied to and useful for multiple interventional pain procedures. Similar technical instruction with an emphasis on coaxial technique for hip injections as performed in the anterior or anterolateral approach can be used in both fluoroscopic and ultrasound-guided procedures, including facet injection, transforaminal epidural steroid injection, and myriad other procedures performed to ameliorate pain. There are advantages to pursuing a similar approach with all image-guided procedures. Evaluated in this comparison study is an alternative technique that has potential for risk reduction benefit with reduced proximity to neurovascular structures, which ultimately leads to a safer procedure profile.

Using a lateral approach, the interventionalist determines a starting point, entering the skin at a greater distance from any overlying pannus and the elevated concentration of gram-negative and gram-positive bacteria contained within the inguinal skin.⁶ A previous study demonstrated improved success of intra-articular needle tip placement without image guidance in patients with body mass index (BMI) < 30.⁷ A prior study of anterior approach using anatomic landmarks as compared to lateral approach demonstrated the anterior approach pierced or contacted the femoral nerve in 27% of anterior cases and came within 5 mm of 60% of anterior cases.² Use of image guidance, whether ultrasound, fluoroscopy, or computed tomography (CT) is preferred related to reduced risk of contact with adjacent neurovascular structures. Anatomic surface landmarks have been described as an alternative injection technique, without the use of fluoroscopy for confirmatory initial, intraprocedure, and final placement.⁸ Palpation of anatomic structures is required for this nonimage-guided technique, and although similar to the described technique in this study, the anatomically guided injection starting point is more lateral than the anterior approach but not in the most lateral position in the transverse plane that is used for this fluoroscopically guided lateral approach study.

Physiologic characteristics of subjects and technical aspects of fluoroscopy both can be factors in radiation dose and exposure times for hip injections. Patient BMI was not included in the data collection, but further study would seek to determine whether BMI is a significant risk for any increased radiation dose and exposure times using lateral approach injections. Use of lateral images for fluoroscopy requires penetration of X-ray beam through more tissue compared with that of anterior-posterior images. Further study of these techniques would benefit from comparing the pulse rate of fluoroscopic images and collimation (or focusing of the radiation beam over a smaller area of tissue) as factors in any observed increase in total radiation dose and exposure times.

Improving the safety profile of this procedure could have a positive impact on the patient population receiving fluoroscopic hip injections, both within the VA Ann Arbor Health System and elsewhere. While the study population was limited to the VA patient population seeking subspecialty nonsurgical joint care at a single tertiary care center, this technique is generalizable and can be used in most patients, as hip pain is a common condition necessitating nonoperative evaluation and treatment.

 

Radiation Exposures

As our analysis demonstrates, mean radiation dose exposure for each group was consistent with low (≤ 3 mSv) to moderate (> 3-20 mSv) annual effective doses in the general population.⁷ Both anterior and lateral median radiation dose of 1 mGy and 3 mGy, respectively, are within the standard exposure for radiographs of the pelvis (1.31 mGy).⁹ It is therefore reasonable to consider a lateral approach for hip injection, given the benefits of direct coaxial approach and avoiding needle entry through higher bacteria-concentrated skin.

The lateral approach did have increased radiation dose and exposure time, although it was not statistically significantly greater than the anterior approach. The difference between radiation dose and time to perform either technique was not clinically significant. One potential explanation for this is that the lateral technique has increased tissue to penetrate, which can be reduced with collimation and other fluoroscopic image adjustments. Additionally, as trainees progress in competency, fewer images should need to be obtained.⁷ We hypothesize that as familiarity and comfort with this technique increase, the number of images necessary for successful injection would decrease, leading to decreased radiation dose and exposure time. We would expect that in the hands of a board-certified interventionalist, radiation dose and exposure time would be significantly decreased as compared to our current dataset, and this is an area of planned further study. With our existing dataset, the majority of procedures were performed with trainees, with inadequate information documented for comparison of dose over time and procedural experience under individual physicians.

Notable strengths of this study are the direct comparison of the anterior approach when compared to the lateral approach with regard to radiation dose and exposure time, which we have not seen described in the literature. A detailed description of the technique may result in increased utilization by other providers. Data were collected from multiple providers, as board-certified pain physicians and board-eligible interventional pain fellows performed the procedures. This variability in providers increases the generalizability of the findings, with a variety of providers, disciplines, years of experiences, and type of training represented.

Limitations

Limitations include the retrospective nature of the study and the relatively small sample size. However, even with this limitation, it is notable that no statistically significant differences were observed in mean radiation dose or fluoroscopy exposure time, making the lateral approach, at minimum, a noninferior technique. Combined with the improved safety profile, this technique is a viable alternative to the traditional anterior-oblique approach. Further study should be performed, such as a prospective, randomized control trial investigating the 2 techniques and following pain scores and functional ability after the procedure.

Conclusion

Given the decreased procedural risk related to proximity of neurovascular structures and coaxial technique for needle advancement, lateral approach for hip injection should be considered by those in any discipline performing fluoroscopically guided procedures. Lateral technique may be particularly useful in technically challenging cases and when skin entry at the anterior groin is suboptimal, as a noninferior alternative to traditional anterior method.

Hip injections are performed as diagnostic and therapeutic interventions across a variety of medical subspecialties, including but not limited to those practicing physical medicine and rehabilitation, pain medicine, sports medicine, orthopedic surgery, and radiology. Traditional image-guided intra-articular hip injection commonly uses an anterior-oblique approach from a starting point on the anterior groin traversing soft tissue anterior to the femoral neck to the target needle placement at the femoral head-neck junction.

In fluoroscopic procedures, a coaxial technique for needles placement is used for safe and precise insertion of needles. An X-ray beam is angled in line with the projected path of the needle from skin entry point to injection target. Coaxial, en face technique (also called EF, parallel, hub view, down the barrel, or barrel view) appears as a single radiopaque dot over the target injection site.¹ This technique minimizes needle redirection for correction of the injection path and minimal disturbance of surrounding tissue on the approach to the intended target.

Noncoaxial technique, as used in the anterior-oblique approach, intentionally directs the needle away from a skin entry point, the needle barrel traversing the X-ray beam toward an injection target. Clinical challenges to injection with the anterior-oblique approach include using a noncoaxial technique. Additional challenges to the anterior-oblique (also referred to as anterior) approach are body habitus and pannus, proximity to neurovascular structures, and patient positioning. By understanding the risks and benefits of varied technical approaches to accomplish a clinical goal and outcome, trainees are better able to select the technique most appropriate for a varied patient population.

Common risks to patients for all intra-articular interventions include bleeding, infection, and pain. Risk of damage to nearby structures is often mentioned as part of a standard informed consent process as it relates to the femoral vein, artery, and nerve that are in close anatomical proximity to the target injection site. When prior studies have examined the risk of complications resulting from intra-articular hip injections, a common conclusion is that despite a relatively low-risk profile for skilled interventionalists, efforts to avoid needle placement in the medial 50% of the femoral head on antero-posterior imaging is recommended.²

The anterior technique is a commonly described approach, and the same can be used for both ultrasound-guided and fluoroscopically guided hip injections.³ Using ultrasound guidance, the anterior technique can be performed with in-plane direct visualization of the needle throughout the procedure. With fluoroscopic guidance, the anterior approach is performed out-of-plane, using the noncoaxial technique. This requires the interventionalist to use tactile and anatomic guidance to the target injection site. The anterior approach for hip injection is one of few interventions where coaxial technique is not used for the procedure, making the instruction for a learner less concrete and potentially more challenging related to the needle path not under direct visualization in plane with the X-ray beam.

Technical guidance and detailed instruction for the lateral approach is infrequently described in fluoroscopic interventional texts. Reference to a lateral approach hip injection was made as early as the 1970s, without detail provided on the technique, with respect to the advantage of visualization of the hip joint for needle placement when hardware is in place.⁴ A more recent article described a lateral approach technique involving the patient in a decubitus (lateral) supine position, which presents limitations in consistent fluoroscopic imaging and can be a challenging static position for the patient to maintain.⁵

The retrospective review of anterior-oblique and lateral approach procedures in this study aims to demonstrate that there is no significant difference in radiation exposure, rate of successful intra-articular injection, or complication rate. If proven as a noninferior technique, the lateral approach may be a valuable interventional skill to those performing hip injections. Potential benefits to the patient and provider include options for the provider to access the joint using either technique. Additionally, the approach can be added to the instructional plan for those practitioners providing technical instruction to trainees within their health care system.

 

Methods

The institutional review board at the VA Ann Arbor Healthcare System reviewed and granted approval for this study. One of 5 interventional pain physician staff members at the VA Ann Arbor Healthcare System performed fluoroscopically guided hip injections. Interventional pain fellows under the direct supervision of board-certified physicians performed the procedures for the study cases. Supervising physicians included both physiatrists and anesthesiologists. Images were reviewed and evaluated without corresponding patient biographic data.

For cases using the lateral approach, the patients were positioned supine on the fluoroscopy table. In anterior-posterior and lateral views, trajectory lines are drawn using a long metal marking rod held adjacent to the patient. With pulsed low-dose fluoroscopy, transverse lines are drawn to identify midpoint of the femoral head in lateral view (Figure 1A, x-axis) and the most direct line from skin to lateral femoral head neck junction joint target (Figure 1B, z-axis). Also confirmed in lateral view, the z-axis marked line drawn on the skin is used to confirm that this transverse plane crosses the overlapping femoral heads (Figure 1A, y-axis).

The cross-section of these transverse and coronal plane lines identifies the starting point for the most direct approach from skin to injection target at femoral head-neck junction. Using the coaxial technique in the lateral view, the needle is introduced and advanced using intermittent fluoroscopic images to the lateral joint target. Continuing in this view, the interventionalist can ensure that advancing the needle to the osseous endpoint will place the tip at the midpoint of the femoral head at the target on the lateral surface, avoiding inadvertent advance of the needle anterior or posterior the femoral head. Final needle placement confirmation is then completed in antero-posterior view (Figure 2A). Contrast enhancement is used to confirm intra-articular spread (Figure 2B).

Cases included in the study were performed over an 8-month period in 2017. Case images recorded in IntelliSpace PACS Radiology software (Andover, MA) were included by creating a list of all cases performed and documented using the major joint injection procedure code. The cases reviewed began with the most recent cases. Two research team members (1 radiologist and 1 interventional pain physician) reviewed the series of saved images for each patient and the associated procedure report. The research team members documented and recorded de-identified study data in Microsoft Excel (Redmond, WA).

Imaging reports, using the saved images and the associated procedure report, were classified for technical approach (anterior, lateral, or inconclusive), success of joint injection as evidenced by appropriate contrast enhancement within the joint space (successful, unsuccessful, or incomplete images), documented use of sedation (yes, no), patient positioning (supine, prone), radiation exposure dose, radiation exposure time, and additional comments, such as “notable pannus” or “hardware present” to annotate significant findings on imaging review.

Statistical Analysis

The distribution of 2 outcomes used to compare rates of complication, radiation dose, and exposure time was checked using the Shapiro-Wilk test. Power analysis determined that inclusion of 30 anterior and 30 lateral cases results in adequate power to detect a 1-point mean difference, assuming a standard deviation of 1.5 in each group. Both radiation dose and exposure time were found to be nonnormally distributed (W = 0.65, P < .001; W = 0.86, P < .001; respectively). Median and interquartile range (IQR) of dose and time in seconds for anterior and lateral approaches were computed. Median differences in radiation dose and exposure time between anterior and lateral approaches were assessed with the k-sample test of equality of medians. All analyses were conducted using Stata Version 14.1 (College Station, TX).

 

Results

Between June 2017 and January 2018, 88 cases were reviewed as performed, with 30 anterior and 30 lateral approach cases included in this retrospective comparison study. A total of 28 cases were excluded from the study for using an inconclusive approach, multiple or bilateral procedures, cases without recorded dose and time data, and inadequately saved images to provide meaningful data (Figure 3).

Rate of successful intervention with needle placement confirmed within the articular space on contrast enhancement was not significantly different in the study groups with 96.7% (29 of 30) anterior approach cases reported as successful, 100% (30 of 30) lateral approach cases reported as successful. Overhanging pannus in the viewing area was reported in 5 anterior approach cases and 4 lateral cases. Hardware was noted in 2 lateral approach cases, none in anterior approach cases. Sedation was used for 3 of the anterior approach cases and none of the lateral approach cases.

Patients undergoing the lateral approach received a higher median radiation dose than did those undergoing the anterior approach, but this was not statistically significant (P = .07) (Table). Those undergoing the lateral approach also had a longer median exposure time than did those undergoing the anterior approach, but this also was not statistically significant (P = .3). With no immediate complications reported in any of the studied interventions, there was no difference in complication rates between anterior and lateral approach cases.

Discussion

Pain medicine fellows who have previously completed residency in a variety of disciplines, often either anesthesiology or physical medicine and rehabilitation, perform fluoroscopically guided procedures and benefit from increased experience with coaxial technique as this improves needle depth and location awareness. Once mastered, this skill set can be applied to and useful for multiple interventional pain procedures. Similar technical instruction with an emphasis on coaxial technique for hip injections as performed in the anterior or anterolateral approach can be used in both fluoroscopic and ultrasound-guided procedures, including facet injection, transforaminal epidural steroid injection, and myriad other procedures performed to ameliorate pain. There are advantages to pursuing a similar approach with all image-guided procedures. Evaluated in this comparison study is an alternative technique that has potential for risk reduction benefit with reduced proximity to neurovascular structures, which ultimately leads to a safer procedure profile.

Using a lateral approach, the interventionalist determines a starting point, entering the skin at a greater distance from any overlying pannus and the elevated concentration of gram-negative and gram-positive bacteria contained within the inguinal skin.⁶ A previous study demonstrated improved success of intra-articular needle tip placement without image guidance in patients with body mass index (BMI) < 30.⁷ A prior study of anterior approach using anatomic landmarks as compared to lateral approach demonstrated the anterior approach pierced or contacted the femoral nerve in 27% of anterior cases and came within 5 mm of 60% of anterior cases.² Use of image guidance, whether ultrasound, fluoroscopy, or computed tomography (CT) is preferred related to reduced risk of contact with adjacent neurovascular structures. Anatomic surface landmarks have been described as an alternative injection technique, without the use of fluoroscopy for confirmatory initial, intraprocedure, and final placement.⁸ Palpation of anatomic structures is required for this nonimage-guided technique, and although similar to the described technique in this study, the anatomically guided injection starting point is more lateral than the anterior approach but not in the most lateral position in the transverse plane that is used for this fluoroscopically guided lateral approach study.

Physiologic characteristics of subjects and technical aspects of fluoroscopy both can be factors in radiation dose and exposure times for hip injections. Patient BMI was not included in the data collection, but further study would seek to determine whether BMI is a significant risk for any increased radiation dose and exposure times using lateral approach injections. Use of lateral images for fluoroscopy requires penetration of X-ray beam through more tissue compared with that of anterior-posterior images. Further study of these techniques would benefit from comparing the pulse rate of fluoroscopic images and collimation (or focusing of the radiation beam over a smaller area of tissue) as factors in any observed increase in total radiation dose and exposure times.

Improving the safety profile of this procedure could have a positive impact on the patient population receiving fluoroscopic hip injections, both within the VA Ann Arbor Health System and elsewhere. While the study population was limited to the VA patient population seeking subspecialty nonsurgical joint care at a single tertiary care center, this technique is generalizable and can be used in most patients, as hip pain is a common condition necessitating nonoperative evaluation and treatment.

 

Radiation Exposures

As our analysis demonstrates, mean radiation dose exposure for each group was consistent with low (≤ 3 mSv) to moderate (> 3-20 mSv) annual effective doses in the general population.⁷ Both anterior and lateral median radiation dose of 1 mGy and 3 mGy, respectively, are within the standard exposure for radiographs of the pelvis (1.31 mGy).⁹ It is therefore reasonable to consider a lateral approach for hip injection, given the benefits of direct coaxial approach and avoiding needle entry through higher bacteria-concentrated skin.

The lateral approach did have increased radiation dose and exposure time, although it was not statistically significantly greater than the anterior approach. The difference between radiation dose and time to perform either technique was not clinically significant. One potential explanation for this is that the lateral technique has increased tissue to penetrate, which can be reduced with collimation and other fluoroscopic image adjustments. Additionally, as trainees progress in competency, fewer images should need to be obtained.⁷ We hypothesize that as familiarity and comfort with this technique increase, the number of images necessary for successful injection would decrease, leading to decreased radiation dose and exposure time. We would expect that in the hands of a board-certified interventionalist, radiation dose and exposure time would be significantly decreased as compared to our current dataset, and this is an area of planned further study. With our existing dataset, the majority of procedures were performed with trainees, with inadequate information documented for comparison of dose over time and procedural experience under individual physicians.

Notable strengths of this study are the direct comparison of the anterior approach when compared to the lateral approach with regard to radiation dose and exposure time, which we have not seen described in the literature. A detailed description of the technique may result in increased utilization by other providers. Data were collected from multiple providers, as board-certified pain physicians and board-eligible interventional pain fellows performed the procedures. This variability in providers increases the generalizability of the findings, with a variety of providers, disciplines, years of experiences, and type of training represented.

Limitations

Limitations include the retrospective nature of the study and the relatively small sample size. However, even with this limitation, it is notable that no statistically significant differences were observed in mean radiation dose or fluoroscopy exposure time, making the lateral approach, at minimum, a noninferior technique. Combined with the improved safety profile, this technique is a viable alternative to the traditional anterior-oblique approach. Further study should be performed, such as a prospective, randomized control trial investigating the 2 techniques and following pain scores and functional ability after the procedure.

Conclusion

Given the decreased procedural risk related to proximity of neurovascular structures and coaxial technique for needle advancement, lateral approach for hip injection should be considered by those in any discipline performing fluoroscopically guided procedures. Lateral technique may be particularly useful in technically challenging cases and when skin entry at the anterior groin is suboptimal, as a noninferior alternative to traditional anterior method.

Hip injections are performed as diagnostic and therapeutic interventions across a variety of medical subspecialties, including but not limited to those practicing physical medicine and rehabilitation, pain medicine, sports medicine, orthopedic surgery, and radiology. Traditional image-guided intra-articular hip injection commonly uses an anterior-oblique approach from a starting point on the anterior groin traversing soft tissue anterior to the femoral neck to the target needle placement at the femoral head-neck junction.

In fluoroscopic procedures, a coaxial technique for needles placement is used for safe and precise insertion of needles. An X-ray beam is angled in line with the projected path of the needle from skin entry point to injection target. Coaxial, en face technique (also called EF, parallel, hub view, down the barrel, or barrel view) appears as a single radiopaque dot over the target injection site.¹ This technique minimizes needle redirection for correction of the injection path and minimal disturbance of surrounding tissue on the approach to the intended target.

Noncoaxial technique, as used in the anterior-oblique approach, intentionally directs the needle away from a skin entry point, the needle barrel traversing the X-ray beam toward an injection target. Clinical challenges to injection with the anterior-oblique approach include using a noncoaxial technique. Additional challenges to the anterior-oblique (also referred to as anterior) approach are body habitus and pannus, proximity to neurovascular structures, and patient positioning. By understanding the risks and benefits of varied technical approaches to accomplish a clinical goal and outcome, trainees are better able to select the technique most appropriate for a varied patient population.

Common risks to patients for all intra-articular interventions include bleeding, infection, and pain. Risk of damage to nearby structures is often mentioned as part of a standard informed consent process as it relates to the femoral vein, artery, and nerve that are in close anatomical proximity to the target injection site. When prior studies have examined the risk of complications resulting from intra-articular hip injections, a common conclusion is that despite a relatively low-risk profile for skilled interventionalists, efforts to avoid needle placement in the medial 50% of the femoral head on antero-posterior imaging is recommended.²

The anterior technique is a commonly described approach, and the same can be used for both ultrasound-guided and fluoroscopically guided hip injections.³ Using ultrasound guidance, the anterior technique can be performed with in-plane direct visualization of the needle throughout the procedure. With fluoroscopic guidance, the anterior approach is performed out-of-plane, using the noncoaxial technique. This requires the interventionalist to use tactile and anatomic guidance to the target injection site. The anterior approach for hip injection is one of few interventions where coaxial technique is not used for the procedure, making the instruction for a learner less concrete and potentially more challenging related to the needle path not under direct visualization in plane with the X-ray beam.

Technical guidance and detailed instruction for the lateral approach is infrequently described in fluoroscopic interventional texts. Reference to a lateral approach hip injection was made as early as the 1970s, without detail provided on the technique, with respect to the advantage of visualization of the hip joint for needle placement when hardware is in place.⁴ A more recent article described a lateral approach technique involving the patient in a decubitus (lateral) supine position, which presents limitations in consistent fluoroscopic imaging and can be a challenging static position for the patient to maintain.⁵

The retrospective review of anterior-oblique and lateral approach procedures in this study aims to demonstrate that there is no significant difference in radiation exposure, rate of successful intra-articular injection, or complication rate. If proven as a noninferior technique, the lateral approach may be a valuable interventional skill to those performing hip injections. Potential benefits to the patient and provider include options for the provider to access the joint using either technique. Additionally, the approach can be added to the instructional plan for those practitioners providing technical instruction to trainees within their health care system.

 

Methods

The institutional review board at the VA Ann Arbor Healthcare System reviewed and granted approval for this study. One of 5 interventional pain physician staff members at the VA Ann Arbor Healthcare System performed fluoroscopically guided hip injections. Interventional pain fellows under the direct supervision of board-certified physicians performed the procedures for the study cases. Supervising physicians included both physiatrists and anesthesiologists. Images were reviewed and evaluated without corresponding patient biographic data.

For cases using the lateral approach, the patients were positioned supine on the fluoroscopy table. In anterior-posterior and lateral views, trajectory lines are drawn using a long metal marking rod held adjacent to the patient. With pulsed low-dose fluoroscopy, transverse lines are drawn to identify midpoint of the femoral head in lateral view (Figure 1A, x-axis) and the most direct line from skin to lateral femoral head neck junction joint target (Figure 1B, z-axis). Also confirmed in lateral view, the z-axis marked line drawn on the skin is used to confirm that this transverse plane crosses the overlapping femoral heads (Figure 1A, y-axis).

The cross-section of these transverse and coronal plane lines identifies the starting point for the most direct approach from skin to injection target at femoral head-neck junction. Using the coaxial technique in the lateral view, the needle is introduced and advanced using intermittent fluoroscopic images to the lateral joint target. Continuing in this view, the interventionalist can ensure that advancing the needle to the osseous endpoint will place the tip at the midpoint of the femoral head at the target on the lateral surface, avoiding inadvertent advance of the needle anterior or posterior the femoral head. Final needle placement confirmation is then completed in antero-posterior view (Figure 2A). Contrast enhancement is used to confirm intra-articular spread (Figure 2B).

Cases included in the study were performed over an 8-month period in 2017. Case images recorded in IntelliSpace PACS Radiology software (Andover, MA) were included by creating a list of all cases performed and documented using the major joint injection procedure code. The cases reviewed began with the most recent cases. Two research team members (1 radiologist and 1 interventional pain physician) reviewed the series of saved images for each patient and the associated procedure report. The research team members documented and recorded de-identified study data in Microsoft Excel (Redmond, WA).

Imaging reports, using the saved images and the associated procedure report, were classified for technical approach (anterior, lateral, or inconclusive), success of joint injection as evidenced by appropriate contrast enhancement within the joint space (successful, unsuccessful, or incomplete images), documented use of sedation (yes, no), patient positioning (supine, prone), radiation exposure dose, radiation exposure time, and additional comments, such as “notable pannus” or “hardware present” to annotate significant findings on imaging review.

Statistical Analysis

The distribution of 2 outcomes used to compare rates of complication, radiation dose, and exposure time was checked using the Shapiro-Wilk test. Power analysis determined that inclusion of 30 anterior and 30 lateral cases results in adequate power to detect a 1-point mean difference, assuming a standard deviation of 1.5 in each group. Both radiation dose and exposure time were found to be nonnormally distributed (W = 0.65, P < .001; W = 0.86, P < .001; respectively). Median and interquartile range (IQR) of dose and time in seconds for anterior and lateral approaches were computed. Median differences in radiation dose and exposure time between anterior and lateral approaches were assessed with the k-sample test of equality of medians. All analyses were conducted using Stata Version 14.1 (College Station, TX).

 

Results

Between June 2017 and January 2018, 88 cases were reviewed as performed, with 30 anterior and 30 lateral approach cases included in this retrospective comparison study. A total of 28 cases were excluded from the study for using an inconclusive approach, multiple or bilateral procedures, cases without recorded dose and time data, and inadequately saved images to provide meaningful data (Figure 3).

Rate of successful intervention with needle placement confirmed within the articular space on contrast enhancement was not significantly different in the study groups with 96.7% (29 of 30) anterior approach cases reported as successful, 100% (30 of 30) lateral approach cases reported as successful. Overhanging pannus in the viewing area was reported in 5 anterior approach cases and 4 lateral cases. Hardware was noted in 2 lateral approach cases, none in anterior approach cases. Sedation was used for 3 of the anterior approach cases and none of the lateral approach cases.

Patients undergoing the lateral approach received a higher median radiation dose than did those undergoing the anterior approach, but this was not statistically significant (P = .07) (Table). Those undergoing the lateral approach also had a longer median exposure time than did those undergoing the anterior approach, but this also was not statistically significant (P = .3). With no immediate complications reported in any of the studied interventions, there was no difference in complication rates between anterior and lateral approach cases.

Discussion

Pain medicine fellows who have previously completed residency in a variety of disciplines, often either anesthesiology or physical medicine and rehabilitation, perform fluoroscopically guided procedures and benefit from increased experience with coaxial technique as this improves needle depth and location awareness. Once mastered, this skill set can be applied to and useful for multiple interventional pain procedures. Similar technical instruction with an emphasis on coaxial technique for hip injections as performed in the anterior or anterolateral approach can be used in both fluoroscopic and ultrasound-guided procedures, including facet injection, transforaminal epidural steroid injection, and myriad other procedures performed to ameliorate pain. There are advantages to pursuing a similar approach with all image-guided procedures. Evaluated in this comparison study is an alternative technique that has potential for risk reduction benefit with reduced proximity to neurovascular structures, which ultimately leads to a safer procedure profile.

Using a lateral approach, the interventionalist determines a starting point, entering the skin at a greater distance from any overlying pannus and the elevated concentration of gram-negative and gram-positive bacteria contained within the inguinal skin.⁶ A previous study demonstrated improved success of intra-articular needle tip placement without image guidance in patients with body mass index (BMI) < 30.⁷ A prior study of anterior approach using anatomic landmarks as compared to lateral approach demonstrated the anterior approach pierced or contacted the femoral nerve in 27% of anterior cases and came within 5 mm of 60% of anterior cases.² Use of image guidance, whether ultrasound, fluoroscopy, or computed tomography (CT) is preferred related to reduced risk of contact with adjacent neurovascular structures. Anatomic surface landmarks have been described as an alternative injection technique, without the use of fluoroscopy for confirmatory initial, intraprocedure, and final placement.⁸ Palpation of anatomic structures is required for this nonimage-guided technique, and although similar to the described technique in this study, the anatomically guided injection starting point is more lateral than the anterior approach but not in the most lateral position in the transverse plane that is used for this fluoroscopically guided lateral approach study.

Physiologic characteristics of subjects and technical aspects of fluoroscopy both can be factors in radiation dose and exposure times for hip injections. Patient BMI was not included in the data collection, but further study would seek to determine whether BMI is a significant risk for any increased radiation dose and exposure times using lateral approach injections. Use of lateral images for fluoroscopy requires penetration of X-ray beam through more tissue compared with that of anterior-posterior images. Further study of these techniques would benefit from comparing the pulse rate of fluoroscopic images and collimation (or focusing of the radiation beam over a smaller area of tissue) as factors in any observed increase in total radiation dose and exposure times.

Improving the safety profile of this procedure could have a positive impact on the patient population receiving fluoroscopic hip injections, both within the VA Ann Arbor Health System and elsewhere. While the study population was limited to the VA patient population seeking subspecialty nonsurgical joint care at a single tertiary care center, this technique is generalizable and can be used in most patients, as hip pain is a common condition necessitating nonoperative evaluation and treatment.

 

Radiation Exposures

As our analysis demonstrates, mean radiation dose exposure for each group was consistent with low (≤ 3 mSv) to moderate (> 3-20 mSv) annual effective doses in the general population.⁷ Both anterior and lateral median radiation dose of 1 mGy and 3 mGy, respectively, are within the standard exposure for radiographs of the pelvis (1.31 mGy).⁹ It is therefore reasonable to consider a lateral approach for hip injection, given the benefits of direct coaxial approach and avoiding needle entry through higher bacteria-concentrated skin.

The lateral approach did have increased radiation dose and exposure time, although it was not statistically significantly greater than the anterior approach. The difference between radiation dose and time to perform either technique was not clinically significant. One potential explanation for this is that the lateral technique has increased tissue to penetrate, which can be reduced with collimation and other fluoroscopic image adjustments. Additionally, as trainees progress in competency, fewer images should need to be obtained.⁷ We hypothesize that as familiarity and comfort with this technique increase, the number of images necessary for successful injection would decrease, leading to decreased radiation dose and exposure time. We would expect that in the hands of a board-certified interventionalist, radiation dose and exposure time would be significantly decreased as compared to our current dataset, and this is an area of planned further study. With our existing dataset, the majority of procedures were performed with trainees, with inadequate information documented for comparison of dose over time and procedural experience under individual physicians.

Notable strengths of this study are the direct comparison of the anterior approach when compared to the lateral approach with regard to radiation dose and exposure time, which we have not seen described in the literature. A detailed description of the technique may result in increased utilization by other providers. Data were collected from multiple providers, as board-certified pain physicians and board-eligible interventional pain fellows performed the procedures. This variability in providers increases the generalizability of the findings, with a variety of providers, disciplines, years of experiences, and type of training represented.

Limitations

Limitations include the retrospective nature of the study and the relatively small sample size. However, even with this limitation, it is notable that no statistically significant differences were observed in mean radiation dose or fluoroscopy exposure time, making the lateral approach, at minimum, a noninferior technique. Combined with the improved safety profile, this technique is a viable alternative to the traditional anterior-oblique approach. Further study should be performed, such as a prospective, randomized control trial investigating the 2 techniques and following pain scores and functional ability after the procedure.

Conclusion

Given the decreased procedural risk related to proximity of neurovascular structures and coaxial technique for needle advancement, lateral approach for hip injection should be considered by those in any discipline performing fluoroscopically guided procedures. Lateral technique may be particularly useful in technically challenging cases and when skin entry at the anterior groin is suboptimal, as a noninferior alternative to traditional anterior method.

Patients given lower prescription quantities of opioid tablets with and without opioid education used significantly less of the medication compared with those given more tablets and no education, according to data from 264 adults and adolescents who underwent anterior cruciate ligament (ACL) surgery.

KatarzynaBialasiewicz/Thinkstock

Although lower default prescription programs have been shown to reduce the number of tablets prescribed, “the effect of reduced prescription quantities on actual patient opioid consumption remains undetermined,” wrote Kevin X. Farley, BS, of Emory University, Atlanta, and colleagues.

In a study published in JAMA, the researchers examined whether patients took fewer tablets if given fewer, and whether patient education about opioids further reduced the number of tablets taken.

The study population included adults and adolescents who underwent ACL surgery at a single center. The patients were divided into three groups: 109 patients received 50 opioid tablets after surgery, 78 received 30 tablets plus education prior to surgery about appropriate opioid use and alternative pain management, and 77 received 30 tablets but no education on opioid use.

Patients given 50 tablets consumed an average of 25 tablets for an average of 5.8 days. By contrast, patients given 30 tablets but no opioid education consumed an average of 16 tablets for an average of 4.5 days, and those given 30 tablets and preoperative education consumed an average of 12 tablets for an average of 3.5 days.

In addition, patients given 30 tablets reported lower levels of constipation and fatigue compared with patients given 50 tablets. No differences were seen in medication refills among the groups.

The findings were limited by several factors including the use of data from a single center, the lack of randomization, and the potential for recall bias, the researchers noted. However, the results suggest that prescribing fewer tablets may further reduce use, as each group consumed approximately half of the tablets given, the researchers added.

“Further investigation should evaluate whether similar opioid stewardship and education protocols would be successful in other patient populations,” they said.

Corresponding author John Xerogeanes, MD, disclosed personal fees from Arthrex and stock options from Trice. The other researchers had no financial conflicts to disclose.

SOURCE: Farley KX et al. JAMA. 2019 June 25.321(24):2465-7.

Patients given lower prescription quantities of opioid tablets with and without opioid education used significantly less of the medication compared with those given more tablets and no education, according to data from 264 adults and adolescents who underwent anterior cruciate ligament (ACL) surgery.

KatarzynaBialasiewicz/Thinkstock

Although lower default prescription programs have been shown to reduce the number of tablets prescribed, “the effect of reduced prescription quantities on actual patient opioid consumption remains undetermined,” wrote Kevin X. Farley, BS, of Emory University, Atlanta, and colleagues.

In a study published in JAMA, the researchers examined whether patients took fewer tablets if given fewer, and whether patient education about opioids further reduced the number of tablets taken.

The study population included adults and adolescents who underwent ACL surgery at a single center. The patients were divided into three groups: 109 patients received 50 opioid tablets after surgery, 78 received 30 tablets plus education prior to surgery about appropriate opioid use and alternative pain management, and 77 received 30 tablets but no education on opioid use.

Patients given 50 tablets consumed an average of 25 tablets for an average of 5.8 days. By contrast, patients given 30 tablets but no opioid education consumed an average of 16 tablets for an average of 4.5 days, and those given 30 tablets and preoperative education consumed an average of 12 tablets for an average of 3.5 days.

In addition, patients given 30 tablets reported lower levels of constipation and fatigue compared with patients given 50 tablets. No differences were seen in medication refills among the groups.

The findings were limited by several factors including the use of data from a single center, the lack of randomization, and the potential for recall bias, the researchers noted. However, the results suggest that prescribing fewer tablets may further reduce use, as each group consumed approximately half of the tablets given, the researchers added.

“Further investigation should evaluate whether similar opioid stewardship and education protocols would be successful in other patient populations,” they said.

Corresponding author John Xerogeanes, MD, disclosed personal fees from Arthrex and stock options from Trice. The other researchers had no financial conflicts to disclose.

SOURCE: Farley KX et al. JAMA. 2019 June 25.321(24):2465-7.

Patients given lower prescription quantities of opioid tablets with and without opioid education used significantly less of the medication compared with those given more tablets and no education, according to data from 264 adults and adolescents who underwent anterior cruciate ligament (ACL) surgery.

KatarzynaBialasiewicz/Thinkstock

Although lower default prescription programs have been shown to reduce the number of tablets prescribed, “the effect of reduced prescription quantities on actual patient opioid consumption remains undetermined,” wrote Kevin X. Farley, BS, of Emory University, Atlanta, and colleagues.

In a study published in JAMA, the researchers examined whether patients took fewer tablets if given fewer, and whether patient education about opioids further reduced the number of tablets taken.

The study population included adults and adolescents who underwent ACL surgery at a single center. The patients were divided into three groups: 109 patients received 50 opioid tablets after surgery, 78 received 30 tablets plus education prior to surgery about appropriate opioid use and alternative pain management, and 77 received 30 tablets but no education on opioid use.

Patients given 50 tablets consumed an average of 25 tablets for an average of 5.8 days. By contrast, patients given 30 tablets but no opioid education consumed an average of 16 tablets for an average of 4.5 days, and those given 30 tablets and preoperative education consumed an average of 12 tablets for an average of 3.5 days.

In addition, patients given 30 tablets reported lower levels of constipation and fatigue compared with patients given 50 tablets. No differences were seen in medication refills among the groups.

The findings were limited by several factors including the use of data from a single center, the lack of randomization, and the potential for recall bias, the researchers noted. However, the results suggest that prescribing fewer tablets may further reduce use, as each group consumed approximately half of the tablets given, the researchers added.

“Further investigation should evaluate whether similar opioid stewardship and education protocols would be successful in other patient populations,” they said.

Corresponding author John Xerogeanes, MD, disclosed personal fees from Arthrex and stock options from Trice. The other researchers had no financial conflicts to disclose.

SOURCE: Farley KX et al. JAMA. 2019 June 25.321(24):2465-7.

ANSWER

The radiograph shows no evidence of an acute fracture. Incidental findings include excreted contrast within the bladder and radiopaque markers from prostatic seed implants.

Fairly extensive sclerosis is noted within both femoral heads, which is suggestive of osteonecrosis (also known as avascular necrosis). Orthopedic consult was requested for further workup of this specific problem.

ANSWER

The radiograph shows no evidence of an acute fracture. Incidental findings include excreted contrast within the bladder and radiopaque markers from prostatic seed implants.

Fairly extensive sclerosis is noted within both femoral heads, which is suggestive of osteonecrosis (also known as avascular necrosis). Orthopedic consult was requested for further workup of this specific problem.

ANSWER

The radiograph shows no evidence of an acute fracture. Incidental findings include excreted contrast within the bladder and radiopaque markers from prostatic seed implants.

Fairly extensive sclerosis is noted within both femoral heads, which is suggestive of osteonecrosis (also known as avascular necrosis). Orthopedic consult was requested for further workup of this specific problem.

 

TORONTO – A high level of pain catastrophizing prior to scheduled knee arthroplasty is not, as previously thought, a harbinger of poor outcomes, and affected patients don’t benefit from cognitive-behavioral therapy–based training in pain coping skills, Daniel L. Riddle, PhD, reported at the OARSI 2019 World Congress.

Bruce Jancin/MDedge News

“The take-home message for us is knee arthroplasty is incredibly effective and there really is no reason to do pain coping skills training in these high–pain catastrophizing patients because the great majority of them have such good outcomes,” said Dr. Riddle, professor of physical therapy at Virginia Commonwealth University, Richmond.

“The other clear message from our trial is that, when you have pain-catastrophizing patients and you lower their pain, their catastrophizing is also lowered. So pain catastrophizing is clearly a response to pain and not a personality trait per se,” he said at the meeting sponsored by the Osteoarthritis Research Society International.

He presented the results of a 402-patient, randomized, three-arm, single-blind trial conducted at five U.S. medical centers. All participants were scheduled for knee arthroplasty for osteoarthritis, and all had moderate- to high-level pain catastrophizing as reflected in the group’s average Pain Catastrophizing Score of 30. They were assigned to an arthritis education active control group, usual care, or an intervention developed specifically for this study: a cognitive-behavioral therapy–based training program for pain coping skills. Similar pain coping skills training interventions have been shown to be beneficial in patients with medically treated knee OA but hadn’t previously been evaluated in surgically treated patients. The primary study endpoint was change in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain Scale at 2, 6, and 12 months after surgery.

The improvement in WOMAC pain in the three study arms was virtually superimposable, going from an average pain score of about 12 preoperatively to 2 postoperatively.

“This was a clear no-effect trial,” Dr. Riddle observed. “These are patients we thought to be at increased risk for poor outcome, but indeed they’re not.”

Pain Catastrophizing Scores improved from 30 preoperatively to roughly 7 at 1 year. “We’ve never seen pain catastrophizing improvements of this magnitude,” the researcher commented.

The study participants typically had a large number of chronically painful areas, but only minimal change in pain scores occurred except in the surgically treated knee.

Of note, even with the impressively large improvements in knee pain, function, and other secondary endpoints in the study group as a whole, roughly 20% of study participants experienced essentially no improvement in their function-limiting knee pain during the first year after arthroplasty. These nonresponders were spread equally across all three study arms. Further research will be needed to develop interventions to help this challenging patient subgroup.

The pain coping skills training consisted of 8 weekly sessions, each an hour long, which began prior to surgery and continued afterward. The intervention was delivered by physical therapists who had been trained by pain psychologists with expertise in cognitive-behavioral therapy. The intervention was delivered by telephone and in face-to-face sessions. The trainers were tracked over the course of the study to make sure that the structured intervention was delivered as planned.

Dr. Riddle reported having no financial conflicts regarding the National Institutes of Health-funded study, the full details of which have been published (J Bone Joint Surg Am. 2019 Feb 6;101[3]:218-227).

[email protected]

 

TORONTO – A high level of pain catastrophizing prior to scheduled knee arthroplasty is not, as previously thought, a harbinger of poor outcomes, and affected patients don’t benefit from cognitive-behavioral therapy–based training in pain coping skills, Daniel L. Riddle, PhD, reported at the OARSI 2019 World Congress.

Bruce Jancin/MDedge News

“The take-home message for us is knee arthroplasty is incredibly effective and there really is no reason to do pain coping skills training in these high–pain catastrophizing patients because the great majority of them have such good outcomes,” said Dr. Riddle, professor of physical therapy at Virginia Commonwealth University, Richmond.

“The other clear message from our trial is that, when you have pain-catastrophizing patients and you lower their pain, their catastrophizing is also lowered. So pain catastrophizing is clearly a response to pain and not a personality trait per se,” he said at the meeting sponsored by the Osteoarthritis Research Society International.

He presented the results of a 402-patient, randomized, three-arm, single-blind trial conducted at five U.S. medical centers. All participants were scheduled for knee arthroplasty for osteoarthritis, and all had moderate- to high-level pain catastrophizing as reflected in the group’s average Pain Catastrophizing Score of 30. They were assigned to an arthritis education active control group, usual care, or an intervention developed specifically for this study: a cognitive-behavioral therapy–based training program for pain coping skills. Similar pain coping skills training interventions have been shown to be beneficial in patients with medically treated knee OA but hadn’t previously been evaluated in surgically treated patients. The primary study endpoint was change in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain Scale at 2, 6, and 12 months after surgery.

The improvement in WOMAC pain in the three study arms was virtually superimposable, going from an average pain score of about 12 preoperatively to 2 postoperatively.

“This was a clear no-effect trial,” Dr. Riddle observed. “These are patients we thought to be at increased risk for poor outcome, but indeed they’re not.”

Pain Catastrophizing Scores improved from 30 preoperatively to roughly 7 at 1 year. “We’ve never seen pain catastrophizing improvements of this magnitude,” the researcher commented.

The study participants typically had a large number of chronically painful areas, but only minimal change in pain scores occurred except in the surgically treated knee.

Of note, even with the impressively large improvements in knee pain, function, and other secondary endpoints in the study group as a whole, roughly 20% of study participants experienced essentially no improvement in their function-limiting knee pain during the first year after arthroplasty. These nonresponders were spread equally across all three study arms. Further research will be needed to develop interventions to help this challenging patient subgroup.

The pain coping skills training consisted of 8 weekly sessions, each an hour long, which began prior to surgery and continued afterward. The intervention was delivered by physical therapists who had been trained by pain psychologists with expertise in cognitive-behavioral therapy. The intervention was delivered by telephone and in face-to-face sessions. The trainers were tracked over the course of the study to make sure that the structured intervention was delivered as planned.

Dr. Riddle reported having no financial conflicts regarding the National Institutes of Health-funded study, the full details of which have been published (J Bone Joint Surg Am. 2019 Feb 6;101[3]:218-227).

[email protected]

 

TORONTO – A high level of pain catastrophizing prior to scheduled knee arthroplasty is not, as previously thought, a harbinger of poor outcomes, and affected patients don’t benefit from cognitive-behavioral therapy–based training in pain coping skills, Daniel L. Riddle, PhD, reported at the OARSI 2019 World Congress.

Bruce Jancin/MDedge News

“The take-home message for us is knee arthroplasty is incredibly effective and there really is no reason to do pain coping skills training in these high–pain catastrophizing patients because the great majority of them have such good outcomes,” said Dr. Riddle, professor of physical therapy at Virginia Commonwealth University, Richmond.

“The other clear message from our trial is that, when you have pain-catastrophizing patients and you lower their pain, their catastrophizing is also lowered. So pain catastrophizing is clearly a response to pain and not a personality trait per se,” he said at the meeting sponsored by the Osteoarthritis Research Society International.

He presented the results of a 402-patient, randomized, three-arm, single-blind trial conducted at five U.S. medical centers. All participants were scheduled for knee arthroplasty for osteoarthritis, and all had moderate- to high-level pain catastrophizing as reflected in the group’s average Pain Catastrophizing Score of 30. They were assigned to an arthritis education active control group, usual care, or an intervention developed specifically for this study: a cognitive-behavioral therapy–based training program for pain coping skills. Similar pain coping skills training interventions have been shown to be beneficial in patients with medically treated knee OA but hadn’t previously been evaluated in surgically treated patients. The primary study endpoint was change in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain Scale at 2, 6, and 12 months after surgery.

The improvement in WOMAC pain in the three study arms was virtually superimposable, going from an average pain score of about 12 preoperatively to 2 postoperatively.

“This was a clear no-effect trial,” Dr. Riddle observed. “These are patients we thought to be at increased risk for poor outcome, but indeed they’re not.”

Pain Catastrophizing Scores improved from 30 preoperatively to roughly 7 at 1 year. “We’ve never seen pain catastrophizing improvements of this magnitude,” the researcher commented.

The study participants typically had a large number of chronically painful areas, but only minimal change in pain scores occurred except in the surgically treated knee.

Of note, even with the impressively large improvements in knee pain, function, and other secondary endpoints in the study group as a whole, roughly 20% of study participants experienced essentially no improvement in their function-limiting knee pain during the first year after arthroplasty. These nonresponders were spread equally across all three study arms. Further research will be needed to develop interventions to help this challenging patient subgroup.

The pain coping skills training consisted of 8 weekly sessions, each an hour long, which began prior to surgery and continued afterward. The intervention was delivered by physical therapists who had been trained by pain psychologists with expertise in cognitive-behavioral therapy. The intervention was delivered by telephone and in face-to-face sessions. The trainers were tracked over the course of the study to make sure that the structured intervention was delivered as planned.

Dr. Riddle reported having no financial conflicts regarding the National Institutes of Health-funded study, the full details of which have been published (J Bone Joint Surg Am. 2019 Feb 6;101[3]:218-227).

[email protected]

 

The odds of surgical site infection were 5.77 times higher during the 90 days after revision vs. primary total joint replacement, according to the findings of a large cohort study.

©decade3d/Thinkstock

In absolute terms, these rates were 15.6% after revision total knee replacement and 8.6% after revision total hip replacement, vs. 2.1% and 2.1% after the respective primary surgeries, wrote Charles E. Edmiston Jr., PhD, and associates. “This result is consistent with results from several other studies that have reported an increased risk after revision procedures,” they added. Such information is essential for developing care bundles based on presenting risk factors, they wrote in a report published in the American Journal of Infection Control.

Population aging and comorbidities are fueling the need for primary and revision joint replacement surgery. “Such trends highlight the need for solutions to cost-effectively prevent and treat surgical site infections, one of the common complications after total joint replacement procedures,” the researchers wrote. Using IBM MarketScan and Medicare data, they studied 335,134 total knee replacements and 163,547 total hip replacements performed in the United States between 2009 and 2015.

After adjustment for potential confounders, the comorbidities that were most strongly linked to surgical site infections during the 90 days after primary or revision joint replacement were AIDS, paralysis, coagulopathy, metastatic cancer, heart failure, alcohol use disorder, obesity, fluid electrolyte disorders, and chronic pulmonary disorders. The estimated odds ratios for these correlates ranged from 1.33 to 1.58, and all confidence intervals reached statistical significance.

In general, these findings reflect those of smaller studies, the researchers noted. “The challenge for the future will be the development of evidence-based surgical care bundles that focus on the peri-, intra-, and postoperative components of orthopedic patient care, especially in patients undergoing periprosthetic revision.”

Johnson & Johnson Medical Device Companies provided funding. Three coinvestigators reported employment and stockholder ties to the company. In addition, Dr. Edmiston and one coinvestigator reported speaker fees for Ethicon, a Johnson & Johnson company.

SOURCE: Edmiston CE et al. Am J Infect Control. 2019 May 6. doi: 10.1016/j.ajic.2019.03.030.

 

The odds of surgical site infection were 5.77 times higher during the 90 days after revision vs. primary total joint replacement, according to the findings of a large cohort study.

©decade3d/Thinkstock

In absolute terms, these rates were 15.6% after revision total knee replacement and 8.6% after revision total hip replacement, vs. 2.1% and 2.1% after the respective primary surgeries, wrote Charles E. Edmiston Jr., PhD, and associates. “This result is consistent with results from several other studies that have reported an increased risk after revision procedures,” they added. Such information is essential for developing care bundles based on presenting risk factors, they wrote in a report published in the American Journal of Infection Control.

Population aging and comorbidities are fueling the need for primary and revision joint replacement surgery. “Such trends highlight the need for solutions to cost-effectively prevent and treat surgical site infections, one of the common complications after total joint replacement procedures,” the researchers wrote. Using IBM MarketScan and Medicare data, they studied 335,134 total knee replacements and 163,547 total hip replacements performed in the United States between 2009 and 2015.

After adjustment for potential confounders, the comorbidities that were most strongly linked to surgical site infections during the 90 days after primary or revision joint replacement were AIDS, paralysis, coagulopathy, metastatic cancer, heart failure, alcohol use disorder, obesity, fluid electrolyte disorders, and chronic pulmonary disorders. The estimated odds ratios for these correlates ranged from 1.33 to 1.58, and all confidence intervals reached statistical significance.

In general, these findings reflect those of smaller studies, the researchers noted. “The challenge for the future will be the development of evidence-based surgical care bundles that focus on the peri-, intra-, and postoperative components of orthopedic patient care, especially in patients undergoing periprosthetic revision.”

Johnson & Johnson Medical Device Companies provided funding. Three coinvestigators reported employment and stockholder ties to the company. In addition, Dr. Edmiston and one coinvestigator reported speaker fees for Ethicon, a Johnson & Johnson company.

SOURCE: Edmiston CE et al. Am J Infect Control. 2019 May 6. doi: 10.1016/j.ajic.2019.03.030.

 

The odds of surgical site infection were 5.77 times higher during the 90 days after revision vs. primary total joint replacement, according to the findings of a large cohort study.

©decade3d/Thinkstock

In absolute terms, these rates were 15.6% after revision total knee replacement and 8.6% after revision total hip replacement, vs. 2.1% and 2.1% after the respective primary surgeries, wrote Charles E. Edmiston Jr., PhD, and associates. “This result is consistent with results from several other studies that have reported an increased risk after revision procedures,” they added. Such information is essential for developing care bundles based on presenting risk factors, they wrote in a report published in the American Journal of Infection Control.

Population aging and comorbidities are fueling the need for primary and revision joint replacement surgery. “Such trends highlight the need for solutions to cost-effectively prevent and treat surgical site infections, one of the common complications after total joint replacement procedures,” the researchers wrote. Using IBM MarketScan and Medicare data, they studied 335,134 total knee replacements and 163,547 total hip replacements performed in the United States between 2009 and 2015.

After adjustment for potential confounders, the comorbidities that were most strongly linked to surgical site infections during the 90 days after primary or revision joint replacement were AIDS, paralysis, coagulopathy, metastatic cancer, heart failure, alcohol use disorder, obesity, fluid electrolyte disorders, and chronic pulmonary disorders. The estimated odds ratios for these correlates ranged from 1.33 to 1.58, and all confidence intervals reached statistical significance.

In general, these findings reflect those of smaller studies, the researchers noted. “The challenge for the future will be the development of evidence-based surgical care bundles that focus on the peri-, intra-, and postoperative components of orthopedic patient care, especially in patients undergoing periprosthetic revision.”

Johnson & Johnson Medical Device Companies provided funding. Three coinvestigators reported employment and stockholder ties to the company. In addition, Dr. Edmiston and one coinvestigator reported speaker fees for Ethicon, a Johnson & Johnson company.

SOURCE: Edmiston CE et al. Am J Infect Control. 2019 May 6. doi: 10.1016/j.ajic.2019.03.030.

 

TORONTO – As Ontario moved toward bundled payments for services related to orthopedic surgeries for osteoarthritis, procedural volume climbed, average hospital length of stay dropped, and the 30-day postdischarge readmission rate declined modestly. However, emergency department visits shot up by 62%.

Bruce Jancin/MDedge News

And therein lies a key lesson for health policy makers who have embraced bundled payments to reduce rising health care costs, Mayilee Canizares, PhD, observed at the OARSI 2019 World Congress.

In Ontario, with patients discharged sooner and directly to home, there was the negative impact of increased emergency department visits after surgery, Dr. Canizares, of the University Health Network in Toronto, said at OARSI 2019 World Congress, sponsored by the Osteoarthritis Research Society International. “Our findings highlight the importance of coordinating the appropriate support services as well as the need to continue assessing the optimal discharge care plan for osteoarthritis patients undergoing surgery.”

Dr. Canizares’ study of the Ontario-wide experience with orthopedic surgery for osteoarthritis during 2004-2016 received the OARSI 2019 award for the meeting’s top-rated study in clinical epidemiology/health services research.

Using administrative data from Canada’s national health care system, Dr. Canizares and her coinvestigators found that the number of individuals undergoing elective orthopedic surgery for osteoarthritis ballooned from 22,700 in 2004 to 41,900 in 2016, representing an increase from 246 to 381 procedures per 100,000 people. During this time, the mean length of stay declined from about 5 days to just under 3 days, the 30-day readmission rate dropped from 4.2% to 3.4%, and the rate of emergency department visits within 30 days post discharge rose steadily from 8.7% in 2004 to 14.1% in 2016.

Roughly half of the operations were total knee replacements and one-third were hip replacements. The profile of patients undergoing surgery changed little over the course of the 12-year study with the exception that in more recent years patients presented with more comorbidities: Indeed, three or more comorbid conditions were present in 2.9% of the surgical patients in 2004 compared to 4.2% in 2016.

In multivariate logistic regression analyses, patient characteristics didn’t explain the change over time in early readmission or unplanned emergency department visit rates. However, discharge disposition did: By 2014, more patients were being discharged home, and in nearly half of cases that was being done without support.

Dr. Canizares reported having no financial conflicts regarding her study, funded by the Toronto General and Western Hospital Foundation.

[email protected]

SOURCE: Canizares M. OARSI, Abstract 16.

 

TORONTO – As Ontario moved toward bundled payments for services related to orthopedic surgeries for osteoarthritis, procedural volume climbed, average hospital length of stay dropped, and the 30-day postdischarge readmission rate declined modestly. However, emergency department visits shot up by 62%.

Bruce Jancin/MDedge News

And therein lies a key lesson for health policy makers who have embraced bundled payments to reduce rising health care costs, Mayilee Canizares, PhD, observed at the OARSI 2019 World Congress.

In Ontario, with patients discharged sooner and directly to home, there was the negative impact of increased emergency department visits after surgery, Dr. Canizares, of the University Health Network in Toronto, said at OARSI 2019 World Congress, sponsored by the Osteoarthritis Research Society International. “Our findings highlight the importance of coordinating the appropriate support services as well as the need to continue assessing the optimal discharge care plan for osteoarthritis patients undergoing surgery.”

Dr. Canizares’ study of the Ontario-wide experience with orthopedic surgery for osteoarthritis during 2004-2016 received the OARSI 2019 award for the meeting’s top-rated study in clinical epidemiology/health services research.

Using administrative data from Canada’s national health care system, Dr. Canizares and her coinvestigators found that the number of individuals undergoing elective orthopedic surgery for osteoarthritis ballooned from 22,700 in 2004 to 41,900 in 2016, representing an increase from 246 to 381 procedures per 100,000 people. During this time, the mean length of stay declined from about 5 days to just under 3 days, the 30-day readmission rate dropped from 4.2% to 3.4%, and the rate of emergency department visits within 30 days post discharge rose steadily from 8.7% in 2004 to 14.1% in 2016.

Roughly half of the operations were total knee replacements and one-third were hip replacements. The profile of patients undergoing surgery changed little over the course of the 12-year study with the exception that in more recent years patients presented with more comorbidities: Indeed, three or more comorbid conditions were present in 2.9% of the surgical patients in 2004 compared to 4.2% in 2016.

In multivariate logistic regression analyses, patient characteristics didn’t explain the change over time in early readmission or unplanned emergency department visit rates. However, discharge disposition did: By 2014, more patients were being discharged home, and in nearly half of cases that was being done without support.

Dr. Canizares reported having no financial conflicts regarding her study, funded by the Toronto General and Western Hospital Foundation.

[email protected]

SOURCE: Canizares M. OARSI, Abstract 16.

 

TORONTO – As Ontario moved toward bundled payments for services related to orthopedic surgeries for osteoarthritis, procedural volume climbed, average hospital length of stay dropped, and the 30-day postdischarge readmission rate declined modestly. However, emergency department visits shot up by 62%.

Bruce Jancin/MDedge News

And therein lies a key lesson for health policy makers who have embraced bundled payments to reduce rising health care costs, Mayilee Canizares, PhD, observed at the OARSI 2019 World Congress.

In Ontario, with patients discharged sooner and directly to home, there was the negative impact of increased emergency department visits after surgery, Dr. Canizares, of the University Health Network in Toronto, said at OARSI 2019 World Congress, sponsored by the Osteoarthritis Research Society International. “Our findings highlight the importance of coordinating the appropriate support services as well as the need to continue assessing the optimal discharge care plan for osteoarthritis patients undergoing surgery.”

Dr. Canizares’ study of the Ontario-wide experience with orthopedic surgery for osteoarthritis during 2004-2016 received the OARSI 2019 award for the meeting’s top-rated study in clinical epidemiology/health services research.

Using administrative data from Canada’s national health care system, Dr. Canizares and her coinvestigators found that the number of individuals undergoing elective orthopedic surgery for osteoarthritis ballooned from 22,700 in 2004 to 41,900 in 2016, representing an increase from 246 to 381 procedures per 100,000 people. During this time, the mean length of stay declined from about 5 days to just under 3 days, the 30-day readmission rate dropped from 4.2% to 3.4%, and the rate of emergency department visits within 30 days post discharge rose steadily from 8.7% in 2004 to 14.1% in 2016.

Roughly half of the operations were total knee replacements and one-third were hip replacements. The profile of patients undergoing surgery changed little over the course of the 12-year study with the exception that in more recent years patients presented with more comorbidities: Indeed, three or more comorbid conditions were present in 2.9% of the surgical patients in 2004 compared to 4.2% in 2016.

In multivariate logistic regression analyses, patient characteristics didn’t explain the change over time in early readmission or unplanned emergency department visit rates. However, discharge disposition did: By 2014, more patients were being discharged home, and in nearly half of cases that was being done without support.

Dr. Canizares reported having no financial conflicts regarding her study, funded by the Toronto General and Western Hospital Foundation.

[email protected]

SOURCE: Canizares M. OARSI, Abstract 16.

 

TORONTO – High-intensity statin therapy was associated with markedly reduced rates of knee and hip replacement surgery for osteoarthritis or rheumatoid arthritis in a longitudinal cohort study comparing nearly 180,000 statin users with an equal number of propensity-matched nonusers, Jie Wei, PhD, reported at the OARSI 2019 World Congress.

Bruce Jancin/MDedge News

Less intensive statin therapy was associated with significantly less need for joint replacement surgery in rheumatoid arthritis patients, but not in those with osteoarthritis, she said at the meeting, sponsored by the Osteoarthritis Research Society International.

“In summary, statins may reduce the risk of joint replacement, especially when given at high strength and in people with rheumatoid arthritis,” said Dr. Wei, an epidemiologist at Massachusetts General Hospital, Boston, and Central South University in Changsha, Hunan, China.

She was quick to note that this study can’t be considered the final, definitive word on the topic, since other investigators’ studies of the relationship between statin usage and joint replacement surgery for arthritis have yielded conflicting results. However, given the thoroughly established super-favorable risk/benefit ratio of statins for the prevention of cardiovascular morbidity and mortality, the possibility of a prospective, randomized, controlled trial addressing the joint surgery issue is for ethical reasons a train that’s left the station.

Dr. Wei presented an analysis drawn from the U.K. Clinical Practice Research Datalink for the years 1989 through mid-2017. The initial sample included the medical records of 17.1 million patients, or 26% of the total U.K. population. From that massive pool, she and her coinvestigators zeroed in on 178,467 statin users and an equal number of non–statin-user controls under the care of 718 primary care physicians, with the pairs propensity score-matched on the basis of age, gender, locality, comorbid conditions, nonstatin medications, lifestyle factors, and duration of rheumatoid arthritis or osteoarthritis. The mean age of the matched pairs was 62 years, 52% were women, and the mean prospective follow-up was 6.5 years.

The use of high-intensity statin therapy – for example, atorvastatin at 40-80 mg/day or rosuvastatin (Crestor) at 20-40 mg/day – was independently associated with a 21% reduction in the risk of knee or hip replacement surgery for osteoarthritis and a 90% reduction for rheumatoid arthritis, compared with statin nonusers. Notably, joint replacement surgery for osteoarthritis was roughly 25-fold more common than for rheumatoid arthritis.

Statin therapy overall, including the more widely prescribed low- and intermediate-intensity regimens, was associated with a 23% reduction in joint replacement surgery for rheumatoid arthritis, compared with statin nonusers, but had no significant impact on surgery for the osteoarthritis population.

A couple of distinguished American rheumatologists in the audience rose to voice reluctance about drawing broad conclusions from this study.

“Bias, as you’ve said yourself, is a bit of a concern,” said David T. Felson, MD, professor of medicine and public health and director of clinical epidemiology at Boston University.

He was troubled that the study design was such that anyone who filled as few as two statin prescriptions during the more than 6-year study period was categorized as a statin user. That, he said, muddies the waters. Does the database contain information on duration of statin therapy, and whether joint replacement surgery was more likely to occur when patients were on or off statin therapy? he asked.

It does, Dr. Wei replied, adding that she will take that suggestion for additional analysis back to her international team of coinvestigators.

“It seems to me,” said Jeffrey N. Katz, MD, “that the major risk of potential bias is that people who were provided high-intensity statins were prescribed that because they were at risk for or had cardiac disease.”

That high cardiovascular risk might have curbed orthopedic surgeons’ enthusiasm to operate. Thus, it would be helpful to learn whether patients who underwent joint replacement were less likely to have undergone coronary revascularization or other cardiac interventions than were those without joint replacement, according to Dr. Katz, professor of medicine and orthopedic surgery at Harvard Medical School, Boston.

Dr. Wei agreed that confounding by indication is always a possibility in an observational study such as this. Identification of a plausible mechanism by which statins might reduce the risk of joint replacement surgery in rheumatoid arthritis – something that hasn’t happened yet – would help counter such concerns.

She noted that a separate recent analysis of the U.K. Clinical Practice Research Datalink by other investigators concluded that statin therapy started up to 5 years following total hip or knee replacement was associated with a significantly reduced risk of revision arthroplasty. Moreover, the benefit was treatment duration-dependent: Patients on statin therapy for more than 5 years were 26% less likely to undergo revision arthroplasty than were those on a statin for less than 1 year (J Rheumatol. 2019 Mar 15. doi: 10.3899/jrheum.180574).

On the other hand, Swedish investigators found that statin use wasn’t associated with a reduced risk of consultation or surgery for osteoarthritis in a pooled analysis of four cohort studies totaling more than 132,000 Swedes followed for 7.5 years (Osteoarthritis Cartilage. 2017 Nov;25[11]:1804-13).

Dr. Wei reported having no financial conflicts regarding the study, which was supported by the National Clinical Research Center of Geriatric Disorders in Hunan, China, and several British universities.

 

[email protected]

SOURCE: Sarmanova A et al. Osteoarthritis cartilage. 2019 Apr;27[suppl 1]:S78-S79. Abstract 77.

 

TORONTO – High-intensity statin therapy was associated with markedly reduced rates of knee and hip replacement surgery for osteoarthritis or rheumatoid arthritis in a longitudinal cohort study comparing nearly 180,000 statin users with an equal number of propensity-matched nonusers, Jie Wei, PhD, reported at the OARSI 2019 World Congress.

Bruce Jancin/MDedge News

Less intensive statin therapy was associated with significantly less need for joint replacement surgery in rheumatoid arthritis patients, but not in those with osteoarthritis, she said at the meeting, sponsored by the Osteoarthritis Research Society International.

“In summary, statins may reduce the risk of joint replacement, especially when given at high strength and in people with rheumatoid arthritis,” said Dr. Wei, an epidemiologist at Massachusetts General Hospital, Boston, and Central South University in Changsha, Hunan, China.

She was quick to note that this study can’t be considered the final, definitive word on the topic, since other investigators’ studies of the relationship between statin usage and joint replacement surgery for arthritis have yielded conflicting results. However, given the thoroughly established super-favorable risk/benefit ratio of statins for the prevention of cardiovascular morbidity and mortality, the possibility of a prospective, randomized, controlled trial addressing the joint surgery issue is for ethical reasons a train that’s left the station.

Dr. Wei presented an analysis drawn from the U.K. Clinical Practice Research Datalink for the years 1989 through mid-2017. The initial sample included the medical records of 17.1 million patients, or 26% of the total U.K. population. From that massive pool, she and her coinvestigators zeroed in on 178,467 statin users and an equal number of non–statin-user controls under the care of 718 primary care physicians, with the pairs propensity score-matched on the basis of age, gender, locality, comorbid conditions, nonstatin medications, lifestyle factors, and duration of rheumatoid arthritis or osteoarthritis. The mean age of the matched pairs was 62 years, 52% were women, and the mean prospective follow-up was 6.5 years.

The use of high-intensity statin therapy – for example, atorvastatin at 40-80 mg/day or rosuvastatin (Crestor) at 20-40 mg/day – was independently associated with a 21% reduction in the risk of knee or hip replacement surgery for osteoarthritis and a 90% reduction for rheumatoid arthritis, compared with statin nonusers. Notably, joint replacement surgery for osteoarthritis was roughly 25-fold more common than for rheumatoid arthritis.

Statin therapy overall, including the more widely prescribed low- and intermediate-intensity regimens, was associated with a 23% reduction in joint replacement surgery for rheumatoid arthritis, compared with statin nonusers, but had no significant impact on surgery for the osteoarthritis population.

A couple of distinguished American rheumatologists in the audience rose to voice reluctance about drawing broad conclusions from this study.

“Bias, as you’ve said yourself, is a bit of a concern,” said David T. Felson, MD, professor of medicine and public health and director of clinical epidemiology at Boston University.

He was troubled that the study design was such that anyone who filled as few as two statin prescriptions during the more than 6-year study period was categorized as a statin user. That, he said, muddies the waters. Does the database contain information on duration of statin therapy, and whether joint replacement surgery was more likely to occur when patients were on or off statin therapy? he asked.

It does, Dr. Wei replied, adding that she will take that suggestion for additional analysis back to her international team of coinvestigators.

“It seems to me,” said Jeffrey N. Katz, MD, “that the major risk of potential bias is that people who were provided high-intensity statins were prescribed that because they were at risk for or had cardiac disease.”

That high cardiovascular risk might have curbed orthopedic surgeons’ enthusiasm to operate. Thus, it would be helpful to learn whether patients who underwent joint replacement were less likely to have undergone coronary revascularization or other cardiac interventions than were those without joint replacement, according to Dr. Katz, professor of medicine and orthopedic surgery at Harvard Medical School, Boston.

Dr. Wei agreed that confounding by indication is always a possibility in an observational study such as this. Identification of a plausible mechanism by which statins might reduce the risk of joint replacement surgery in rheumatoid arthritis – something that hasn’t happened yet – would help counter such concerns.

She noted that a separate recent analysis of the U.K. Clinical Practice Research Datalink by other investigators concluded that statin therapy started up to 5 years following total hip or knee replacement was associated with a significantly reduced risk of revision arthroplasty. Moreover, the benefit was treatment duration-dependent: Patients on statin therapy for more than 5 years were 26% less likely to undergo revision arthroplasty than were those on a statin for less than 1 year (J Rheumatol. 2019 Mar 15. doi: 10.3899/jrheum.180574).

On the other hand, Swedish investigators found that statin use wasn’t associated with a reduced risk of consultation or surgery for osteoarthritis in a pooled analysis of four cohort studies totaling more than 132,000 Swedes followed for 7.5 years (Osteoarthritis Cartilage. 2017 Nov;25[11]:1804-13).

Dr. Wei reported having no financial conflicts regarding the study, which was supported by the National Clinical Research Center of Geriatric Disorders in Hunan, China, and several British universities.

 

[email protected]

SOURCE: Sarmanova A et al. Osteoarthritis cartilage. 2019 Apr;27[suppl 1]:S78-S79. Abstract 77.

 

TORONTO – High-intensity statin therapy was associated with markedly reduced rates of knee and hip replacement surgery for osteoarthritis or rheumatoid arthritis in a longitudinal cohort study comparing nearly 180,000 statin users with an equal number of propensity-matched nonusers, Jie Wei, PhD, reported at the OARSI 2019 World Congress.

Bruce Jancin/MDedge News

Less intensive statin therapy was associated with significantly less need for joint replacement surgery in rheumatoid arthritis patients, but not in those with osteoarthritis, she said at the meeting, sponsored by the Osteoarthritis Research Society International.

“In summary, statins may reduce the risk of joint replacement, especially when given at high strength and in people with rheumatoid arthritis,” said Dr. Wei, an epidemiologist at Massachusetts General Hospital, Boston, and Central South University in Changsha, Hunan, China.

She was quick to note that this study can’t be considered the final, definitive word on the topic, since other investigators’ studies of the relationship between statin usage and joint replacement surgery for arthritis have yielded conflicting results. However, given the thoroughly established super-favorable risk/benefit ratio of statins for the prevention of cardiovascular morbidity and mortality, the possibility of a prospective, randomized, controlled trial addressing the joint surgery issue is for ethical reasons a train that’s left the station.

Dr. Wei presented an analysis drawn from the U.K. Clinical Practice Research Datalink for the years 1989 through mid-2017. The initial sample included the medical records of 17.1 million patients, or 26% of the total U.K. population. From that massive pool, she and her coinvestigators zeroed in on 178,467 statin users and an equal number of non–statin-user controls under the care of 718 primary care physicians, with the pairs propensity score-matched on the basis of age, gender, locality, comorbid conditions, nonstatin medications, lifestyle factors, and duration of rheumatoid arthritis or osteoarthritis. The mean age of the matched pairs was 62 years, 52% were women, and the mean prospective follow-up was 6.5 years.

The use of high-intensity statin therapy – for example, atorvastatin at 40-80 mg/day or rosuvastatin (Crestor) at 20-40 mg/day – was independently associated with a 21% reduction in the risk of knee or hip replacement surgery for osteoarthritis and a 90% reduction for rheumatoid arthritis, compared with statin nonusers. Notably, joint replacement surgery for osteoarthritis was roughly 25-fold more common than for rheumatoid arthritis.

Statin therapy overall, including the more widely prescribed low- and intermediate-intensity regimens, was associated with a 23% reduction in joint replacement surgery for rheumatoid arthritis, compared with statin nonusers, but had no significant impact on surgery for the osteoarthritis population.

A couple of distinguished American rheumatologists in the audience rose to voice reluctance about drawing broad conclusions from this study.

“Bias, as you’ve said yourself, is a bit of a concern,” said David T. Felson, MD, professor of medicine and public health and director of clinical epidemiology at Boston University.

He was troubled that the study design was such that anyone who filled as few as two statin prescriptions during the more than 6-year study period was categorized as a statin user. That, he said, muddies the waters. Does the database contain information on duration of statin therapy, and whether joint replacement surgery was more likely to occur when patients were on or off statin therapy? he asked.

It does, Dr. Wei replied, adding that she will take that suggestion for additional analysis back to her international team of coinvestigators.

“It seems to me,” said Jeffrey N. Katz, MD, “that the major risk of potential bias is that people who were provided high-intensity statins were prescribed that because they were at risk for or had cardiac disease.”

That high cardiovascular risk might have curbed orthopedic surgeons’ enthusiasm to operate. Thus, it would be helpful to learn whether patients who underwent joint replacement were less likely to have undergone coronary revascularization or other cardiac interventions than were those without joint replacement, according to Dr. Katz, professor of medicine and orthopedic surgery at Harvard Medical School, Boston.

Dr. Wei agreed that confounding by indication is always a possibility in an observational study such as this. Identification of a plausible mechanism by which statins might reduce the risk of joint replacement surgery in rheumatoid arthritis – something that hasn’t happened yet – would help counter such concerns.

She noted that a separate recent analysis of the U.K. Clinical Practice Research Datalink by other investigators concluded that statin therapy started up to 5 years following total hip or knee replacement was associated with a significantly reduced risk of revision arthroplasty. Moreover, the benefit was treatment duration-dependent: Patients on statin therapy for more than 5 years were 26% less likely to undergo revision arthroplasty than were those on a statin for less than 1 year (J Rheumatol. 2019 Mar 15. doi: 10.3899/jrheum.180574).

On the other hand, Swedish investigators found that statin use wasn’t associated with a reduced risk of consultation or surgery for osteoarthritis in a pooled analysis of four cohort studies totaling more than 132,000 Swedes followed for 7.5 years (Osteoarthritis Cartilage. 2017 Nov;25[11]:1804-13).

Dr. Wei reported having no financial conflicts regarding the study, which was supported by the National Clinical Research Center of Geriatric Disorders in Hunan, China, and several British universities.

 

[email protected]

SOURCE: Sarmanova A et al. Osteoarthritis cartilage. 2019 Apr;27[suppl 1]:S78-S79. Abstract 77.