Original Research

Tourniquets are often used in total knee arthroplasty (TKA) to improve visualization of structures, shorten operative time, reduce intraoperative bleeding, and improve cementing technique. Despite these advantages, controversy remains regarding the safety of tourniquet use. Tourniquets have been associated with nerve palsies, vascular injury, and muscle damage.^1-5 Some have hypothesized they may cause venous stasis or direct endothelial damage that may develop into deep vein thrombosis (DVT). Abdel-Salam and Eyres⁶ found an increased incidence of postoperative wound complications and DVTs associated with tourniquet use.

Moreover, investigators have analyzed the role of tourniquets in populations at high risk for wound complications. DeLaurentis and colleagues⁷ performed a prospective and retrospective analysis of 1182 TKA patients, 24 (2%) of whom had preexisting peripheral vascular disease (PVD), defined as a history of arterial insufficiency, absent dorsalis pedis and/or absent posterior tibial pulsations, and arterial calcifications. A tourniquet was used in each case. Arterial complications occurred in 6 of the 24 patients with PVD. As expected, the authors found that a history of intermittent claudication, pain at rest, and arterial ulcers resulted in a high risk for vascular complications. Further studies have supported this finding and expanded the list of predisposing factors to include previous vascular surgery and absent and asymmetric pedal pulsations.^7-11 Of particular concern to total joint arthroplasty surgeons was the finding by DeLaurentis and colleagues⁷ that patients with radiographic evidence of calcification of the distal superficial femoral artery and/or popliteal artery were at risk for arterial complications. This finding is also supported by other studies.^8,11 In TKA, damage to arterial structures proximal to the surgical field could manifest as impaired postoperative wound healing or an ischemic limb. Wound healing depends on adequate blood flow to the healing tissue, and any damage to arterial or venous structures can theoretically compromise this process.

Added to vascular/wound complications as concerning complications in orthopedic surgery is venous thromboembolism (VTE). The role of tourniquets in the formation of VTEs is controversial. A tourniquet has the potential to increase the risk for DVT because of the stasis of venous blood in the lower limb or possible damage to calcified blood vessels. Callam and colleagues¹² studied the connection between artery disease and chronic leg ulcers and found that half the patients diagnosed with peripheral artery disease also had stigmata of chronic venous insufficiency. Therefore, the entities can occur in tandem, and surgeons should keep this in mind.

Here we report on a study we conducted to determine whether tourniquet use in TKA in patients with preexisting radiographic evidence of vascular disease increases the risk for wound complications or VTE.

Patients and Methods

We retrospectively reviewed 461 consecutive primary TKAs (373 patients) performed between January 2007 and June 2012 by 2 attending orthopedic surgeons specializing in adult reconstruction. Medical records and operative reports of 583 patients were examined after receiving institutional review board approval. Of these patients, 373 (64%) had a minimum of 12-month follow-up data available. Twelve months was deemed long enough to discover wound complications or DVTs secondary to the index procedure. Most of these outcomes manifest within the first 3 months after surgery and certainly by 12 months. Follow-up longer than 12 months may become a confounder, as wound complications outside the acute to subacute postoperative window could be related to patients’ underlying PVD and not directly to tourniquet use during surgery. Patient demographics and comorbidities were recorded. Comorbidities were obtained from preoperative medical evaluations and surgeons’ preoperative evaluations. All patients had preoperative palpable dorsalis pedis and posterior tibialis arterial pulses. No patient required preoperative vascular studies based on preoperative examination or comorbidities. No patient had prior vascular bypass surgery or stenting.

TKA was performed in a nonlaminar flow, positive-pressure, high-efficiency particulate air-filtered room with sterile toga/surgical helmet systems. For all patients, a pneumatic thigh tourniquet was applied, and the patient was prepared and draped. After limb exsanguination using a rubber bandage, the limb was elevated and the tourniquet inflated to a pressure of 250 to 300 mm Hg. The tourniquet was released either just before closure or immediately after closure in all cases; it was always let down before placement of final bandages.

Prophylactic chemical anticoagulation consisting of warfarin, aspirin, or enoxaparin was used in all patients and continued for 4 to 6 weeks after surgery. All patients received mechanical DVT prophylaxis with sequential compression devices, and all were mobilized out of bed beginning either the day of surgery or the next day. All patients received perioperative intravenous antibiotics, with the preoperative dose given before tourniquet inflation and the last postoperative dose stopped within 24 hours of surgery.

All patients who had primary TKA underwent preoperative medical evaluation and optimization. The patient’s hospital course was monitored closely, and complications noted by the orthopedic team were documented. Follow-up documentation was retrospectively reviewed for evidence of wound complications or VTE. Wound complications were defined as cellulitis, delayed wound healing, wound dehiscence, and/or periprosthetic joint infection. In the case of VTE, physical examination findings were not sufficient for inclusion. Venous duplex ultrasonography demonstrating the clot was reviewed before inclusion.

Preoperative radiographs were examined for arterial calcification (Figure). We refer to calcification seen above the knee joint as proximal calcification and to calcification observed below the joint as distal calcification. Patients exhibited calcification proximally only, distally only, or both proximally and distally. The 373 patients were placed into 2 groups based on whether they had preoperative arterial calcification on plain radiography of the knee. One group (285 patients with no radiographic evidence of preoperative knee arterial calcification) underwent 365 TKAs, and the other group (88 patients with radiographic evidence of preoperative knee arterial calcification) underwent 96 TKAs.

A sample size calculation was performed to determine how many patients were needed in each group with 80% power and an α of 0.05. With an estimated difference in VTE/wound complication rate between the calcification and no-calcification groups of 12%, we needed to review 316 TKAs total. This 12% difference was based on study findings of a 25% complication rate in PVD patients who underwent tourniquet-assisted TKA, and the rate of VTE/wound complication after TKA in patients overall, which can be up to 12%.^7,13,14 We exceeded minimal enrollment and had 461 TKAs. Descriptive statistics were reported, with means and ranges provided where appropriate. Independent t test was used to evaluate the differences in continuous data (age) between the groups. Univariate analysis (using Pearson χ² and Fisher exact tests) and multivariate logistic regression analysis were used to evaluate the effects of categorical variables (sex, comorbidity, calcification [presence, absence], and location of calcification [proximal only, distal only, both]) on wound complication and VTE rates. All tests were 2-tailed and performed with a type I error rate of 0.05. Data analysis was performed with SPSS Version 19.0 (SPSS).

Results

Patient characteristics are summarized in Table 1. Of the 373 patients, 285 lacked calcification, and 88 had calcification. Mean age was 67.73 years (range, 24-92 years) for all patients, 65.99 years (range, 24-89 years) for the no-calcification group, and 74.32 years (range, 54-92 years) for the calcification group; the calcification group demonstrated a trend toward older age, but the difference was not significantly different (P = .07). Of the 373 patients, 156 (41.82%) were male: 110 in the no-calcification group (38.60%) and 46 in the calcification group (52.27%); sex was significantly (P = .002) different between groups, with more males in the calcification group.

Data on total preoperative comorbidities are summarized in Table 2. Hypertension, hyperlipidemia, diabetes, and coronary artery disease (CAD) were the most common comorbidities, and they were all significantly (P ≤ .05) increased in the calcification group.

No patients had reported arterial complications, such as arterial bleeding, aneurysm, intimal tears, or loss of distal pulses. Wound complication after TKA was detected in 3.04% of all cases (Table 3). Rate of DVT after TKA was 2.60% of all cases, and rate of pulmonary embolism after TKA was 2.17% of all cases. Of the 96 TKAs with preoperative radiographic evidence of calcification, 47 (48.96%) had proximal calcification only, 11 (11.46%) had distal calcification only, and 38 (39.58%) had both proximal and distal calcification (Table 4). There was no significant difference between the rate of wound complication or VTE based on location of vascular calcification.

Univariate analysis demonstrated that presence of arterial knee calcification did not increase the risk for postoperative wound complication (odds ratio [OR], 1.04; 95% confidence interval [CI], 0.28-3.80; P > .05) (Table 5). Location of arterial knee calcification also did not increase the risk for postoperative wound complication. In addition, univariate analysis demonstrated that presence of arterial knee calcification did not increase the risk for postoperative VTE (OR, 1.20; 95% CI, 0.43-3.36; P > .05 (Table 6).

Of the 14 wound complications, the most common infections were cellulitis (5/14 cases; 35.71%) and infected hardware that required component revision (5/14 cases; 35.71%). Mean time from TKA to infection was 137.93 days (range, 5-783 days). The most common organism grown in culture from the wound was Staphylococcus (5/14 cases; 35.71%).

Additional univariate statistical analysis revealed that presence of diabetes, hypertension, prior VTE, CAD, and male sex was linked to higher incidence of wound complication (P < .05) (Table 5). When multivariate analysis was performed, hypertension, prior VTE, and male sex remained significant (P < .05) (Table 5).

Discussion

TKA is a safe and effective procedure used to treat osteoarthritis of the knee and improve patients’ quality of life.¹⁵ About 700,000 TKAs are performed annually in the United States.¹⁶ Because of improvements in preventive medicine and medical technology, life expectancy is increasing, and TKAs are now being performed in higher numbers and in an older patient population. Over the next few decades, these developments will lead to more postoperative complications. It is projected that, by 2030, the need for TKAs in the United States will increase by 673% to 3.48 million.¹⁷ Postoperative complications are rare but unfortunately often lead to poor outcomes or even mortality.¹⁸ To help minimize the number of postoperative complications, we must understand the safety of tourniquet use in TKA. Other investigators have concluded that tourniquet use is unsafe in patients with preoperative vascular calcifications on plain radiographs.^7,8,11 The present study, designed to elucidate whether preoperative evidence of knee arterial calcification may predispose TKA patients to postoperative wound complication or VTE, had some important findings.

In our study, wound complication and VTE occurred in a considerable number of patients after TKA. Despite exceeding the number of patients calculated by the power analysis, our population may have been inadequate to fully detect statistical significance. Thus, our conclusion of failing to reject the null hypothesis may have been because of sample size, a type II error. We found that, after primary TKA, 3.04% of patients developed wound complications and 4.77% VTE. According to the literature, the incidence of infection after primary TKA is between 0.5% and 12%, and that of VTE reported within 3 months after TKA is 1.3% to 10%.^13,14 Although we had 100% VTE prophylaxis, meeting the standard of care, VTE after TKA remains a postoperative complication.¹⁹ This study also found that a considerable percentage of primary TKA patients (23.59%) had preoperative calcification of the knee arteries. To our knowledge, this study was the first to quantify the incidence of knee arterial calcification in patients who underwent TKA.

Preoperative calcification of the knee arteries in patients who underwent TKA did not increase the risk for wound complication, VTE, or arterial damage. These calcifications, however, do pose an increased systemic vascular risk.²⁰ Calcification of the vascular wall predicts increased cardiovascular risk, independent of classical cardiovascular risk factors.^3,18,21-24 Clinically, patients who have both diabetes and calcifications are at significant excess risk for total mortality, stroke mortality, and cardiovascular mortality, compared with patients with diabetes but without such calcifications. They also had a significantly higher incidence of coronary heart disease events, stroke events, and lower extremity amputations.^25,26

All our patients underwent tourniquet-assisted TKA. Although previous studies have indicated that tourniquet use may increase arterial complications and wound complications or even limb loss in patients with calcified arteries, we did not find this link.^7,27 Our population had no reported arterial complications related to tourniquet use. Other, smaller studies have had similar findings. Vandenbussche and colleagues²⁸ prospectively studied 80 TKA cases randomized to tourniquet use or no tourniquet use and found no postoperative nerve palsies, wound infections, wound healing problems, or hematomas. Our study is also in accord with studies that have reported tourniquet use did not increase risk for DVT.²⁹ Therefore, unlike earlier data, our data demonstrated that tourniquet use in patients with knee arterial calcification was safe.^7,27,30,31

Patients with calcification were more likely to have the medical comorbidities of hypertension, diabetes, hyperlipidemia, and CAD. All these comorbidities are linked to the development of arterial calcification, or atherosclerotic occlusive disease.^32,33 As life expectancy and the need for TKA increase, it is likely that a larger percentage of TKA patients will have preoperative radiographic evidence of knee arterial calcification. Although current dogma is that tourniquet-assisted TKA is contraindicated for patients with preoperative radiographic evidence of femoral-popliteal calcification, our study results showed that this calcification should not affect preoperative TKA planning for these patients.

We divided our patients into 3 categories: those with proximal calcification (above the joint line), those with distal calcification (below the joint line), and those with both proximal and distal calcification. Location of arterial calcification did not have an effect on their rates of postoperative wound complication or VTE. We hypothesized that patients with proximal calcification would be at increased risk for direct arterial injury and subsequent wound complication because the tourniquet is placed proximally. Previous research has indicated that arterial occlusion and subsequent wound complication can occur because of low blood flow stemming from tourniquet use.⁷ Further, intraoperative manipulation (flexing) of a knee with calcified vessels causes arterial complications after TKA because these vessels are less elastic than nonatheromatous vessels.³¹ However, we found no such effect. At the same time, having arterial calcification might also be an indication of venous disease in this location,¹² which may be especially important for proximal calcifications. Proximal DVT more likely is a precursor to pulmonary embolic events than distal DVT is.^31,34 However, we found no difference in VTE rates among the 3 arterial location groups, which is supported by studies that have found that tourniquet use does not increase DVT incidence.^29,35-40

Risk for wound complications was higher in male patients and in patients with diabetes, prior VTE, hypertension, or CAD. This finding is important because, with the increasing age of patients who undergo TKA, those with serious medical comorbidities will continue to need and have this surgery.¹⁷ Diabetes may increase the rate of wound complication because patients with diabetes have poor microcirculation, poor collagen synthesis, and reduced wound strength.⁴¹ Malinzak and colleagues⁴² demonstrated that, compared with patients without diabetes, those with diabetes had a significantly higher risk for infection after TKA. Prior VTE, specifically DVT, may increase the rate of wound complication because after DVT the deep veins may be damaged and exhibit valvular dysfunction. Labropoulos and colleagues⁴³ showed that DVT history was strongly associated with ulcer nonhealing. Perhaps hypertension has been overlooked as a risk factor for wound complication in TKA. No previous studies have assessed the link between hypertension and wound complications after TKA. However, a study of wound healing after total hip arthroplasty found that, compared with normotensive patients, hypertensive patients had delayed wound healing, putting them at higher risk for infection.⁴⁴ In addition, we found that patients with CAD were at increased risk for wound complications—an unexpected finding, as CAD traditionally is not a risk factor for infection or poor wound healing. Recently, however, CAD was identified as an independent risk factor for surgical site infections in posterior lumbar–instrumented arthrodesis.⁴⁵ The etiology of this association is unknown. Also, male patients were at increased risk for wound complication. Male sex has been implicated as an independent risk factor for development of surgical site infections and has been established as an important predisposing factor for periprosthetic joint infections.⁴⁶

It is possible that patients who present with diabetes, VTE, hypertension, or CAD before TKA should have a consultation with a vascular surgeon or should have TKA performed without a tourniquet, but this conclusion cannot be considered definitive without a large prospective randomized trial or possibly registry data. Our data indicate that patients with these comorbidities have higher rates of wound complications irrespective of preoperative radiographic calcifications. On the basis of our study results, however, we certainly recommend that patients with these risk factors have preoperative medical optimization. Orthopedic surgeons should take a thorough history and perform a meticulous physical examination on these patients to look for evidence of PVD. We recommend that, if vascular claudication is elicited in the history, or if there is evidence of peripheral arterial disease—such as hair loss, skin discoloration, dystrophic nail changes, or absent or unequal peripheral pulses—the ankle-brachial index test should be performed. If the index value is less than 0.9, then a preoperative vascular surgery consultation should be obtained.

This study had some weaknesses. First, it was retrospective, so it is possible that some wound or VTE complications were not reported and thus not found in the paper charts or electronic medical records. Some patients may have had VTE diagnostic scans at other hospitals, and their results may not have been recorded across databases. Moreover, some patients may have seen wound specialists for wound infections or wound healing problems, and these may not have been reported to the orthopedic surgeons. Second, though our patient population was not small, it may not have been of adequate size to fully detect statistical significance. We met our enrollment numbers based on our sample size calculations from an a priori power analysis; however, we still draw conclusions with the possibility of committing a type II error in mind by failing to reject the null hypothesis when in reality a statistically significant difference does exist. Third, none of our consecutive patients carried the preoperative diagnosis of PVD, and none had preoperative vascular surgery. Therefore, though calcifications were noted on radiographs, clinically our patients were asymptomatic with respect to vascular health. Last, the 2 groups were not randomized. All patients underwent tourniquet-assisted TKA.           

Conclusion

To our knowledge, this is the largest study to examine the effect of preoperative knee arterial calcification on wound complication and VTE after tourniquet-assisted TKA. Contrary to previously published recommendations, we conclude that TKA can be safely performed with a tourniquet in the presence of preoperative radiographic evidence of such calcification. However, we recommend that patients with diabetes, hypertension, CAD, or prior VTE undergo an appropriate physical examination to elicit any signs or symptoms of vascular disease. If before surgery there is any question of vascular competence, a vascular surgeon should be consulted.

Tourniquets are often used in total knee arthroplasty (TKA) to improve visualization of structures, shorten operative time, reduce intraoperative bleeding, and improve cementing technique. Despite these advantages, controversy remains regarding the safety of tourniquet use. Tourniquets have been associated with nerve palsies, vascular injury, and muscle damage.^1-5 Some have hypothesized they may cause venous stasis or direct endothelial damage that may develop into deep vein thrombosis (DVT). Abdel-Salam and Eyres⁶ found an increased incidence of postoperative wound complications and DVTs associated with tourniquet use.

Moreover, investigators have analyzed the role of tourniquets in populations at high risk for wound complications. DeLaurentis and colleagues⁷ performed a prospective and retrospective analysis of 1182 TKA patients, 24 (2%) of whom had preexisting peripheral vascular disease (PVD), defined as a history of arterial insufficiency, absent dorsalis pedis and/or absent posterior tibial pulsations, and arterial calcifications. A tourniquet was used in each case. Arterial complications occurred in 6 of the 24 patients with PVD. As expected, the authors found that a history of intermittent claudication, pain at rest, and arterial ulcers resulted in a high risk for vascular complications. Further studies have supported this finding and expanded the list of predisposing factors to include previous vascular surgery and absent and asymmetric pedal pulsations.^7-11 Of particular concern to total joint arthroplasty surgeons was the finding by DeLaurentis and colleagues⁷ that patients with radiographic evidence of calcification of the distal superficial femoral artery and/or popliteal artery were at risk for arterial complications. This finding is also supported by other studies.^8,11 In TKA, damage to arterial structures proximal to the surgical field could manifest as impaired postoperative wound healing or an ischemic limb. Wound healing depends on adequate blood flow to the healing tissue, and any damage to arterial or venous structures can theoretically compromise this process.

Added to vascular/wound complications as concerning complications in orthopedic surgery is venous thromboembolism (VTE). The role of tourniquets in the formation of VTEs is controversial. A tourniquet has the potential to increase the risk for DVT because of the stasis of venous blood in the lower limb or possible damage to calcified blood vessels. Callam and colleagues¹² studied the connection between artery disease and chronic leg ulcers and found that half the patients diagnosed with peripheral artery disease also had stigmata of chronic venous insufficiency. Therefore, the entities can occur in tandem, and surgeons should keep this in mind.

Here we report on a study we conducted to determine whether tourniquet use in TKA in patients with preexisting radiographic evidence of vascular disease increases the risk for wound complications or VTE.

Patients and Methods

We retrospectively reviewed 461 consecutive primary TKAs (373 patients) performed between January 2007 and June 2012 by 2 attending orthopedic surgeons specializing in adult reconstruction. Medical records and operative reports of 583 patients were examined after receiving institutional review board approval. Of these patients, 373 (64%) had a minimum of 12-month follow-up data available. Twelve months was deemed long enough to discover wound complications or DVTs secondary to the index procedure. Most of these outcomes manifest within the first 3 months after surgery and certainly by 12 months. Follow-up longer than 12 months may become a confounder, as wound complications outside the acute to subacute postoperative window could be related to patients’ underlying PVD and not directly to tourniquet use during surgery. Patient demographics and comorbidities were recorded. Comorbidities were obtained from preoperative medical evaluations and surgeons’ preoperative evaluations. All patients had preoperative palpable dorsalis pedis and posterior tibialis arterial pulses. No patient required preoperative vascular studies based on preoperative examination or comorbidities. No patient had prior vascular bypass surgery or stenting.

TKA was performed in a nonlaminar flow, positive-pressure, high-efficiency particulate air-filtered room with sterile toga/surgical helmet systems. For all patients, a pneumatic thigh tourniquet was applied, and the patient was prepared and draped. After limb exsanguination using a rubber bandage, the limb was elevated and the tourniquet inflated to a pressure of 250 to 300 mm Hg. The tourniquet was released either just before closure or immediately after closure in all cases; it was always let down before placement of final bandages.

Prophylactic chemical anticoagulation consisting of warfarin, aspirin, or enoxaparin was used in all patients and continued for 4 to 6 weeks after surgery. All patients received mechanical DVT prophylaxis with sequential compression devices, and all were mobilized out of bed beginning either the day of surgery or the next day. All patients received perioperative intravenous antibiotics, with the preoperative dose given before tourniquet inflation and the last postoperative dose stopped within 24 hours of surgery.

All patients who had primary TKA underwent preoperative medical evaluation and optimization. The patient’s hospital course was monitored closely, and complications noted by the orthopedic team were documented. Follow-up documentation was retrospectively reviewed for evidence of wound complications or VTE. Wound complications were defined as cellulitis, delayed wound healing, wound dehiscence, and/or periprosthetic joint infection. In the case of VTE, physical examination findings were not sufficient for inclusion. Venous duplex ultrasonography demonstrating the clot was reviewed before inclusion.

Preoperative radiographs were examined for arterial calcification (Figure). We refer to calcification seen above the knee joint as proximal calcification and to calcification observed below the joint as distal calcification. Patients exhibited calcification proximally only, distally only, or both proximally and distally. The 373 patients were placed into 2 groups based on whether they had preoperative arterial calcification on plain radiography of the knee. One group (285 patients with no radiographic evidence of preoperative knee arterial calcification) underwent 365 TKAs, and the other group (88 patients with radiographic evidence of preoperative knee arterial calcification) underwent 96 TKAs.

A sample size calculation was performed to determine how many patients were needed in each group with 80% power and an α of 0.05. With an estimated difference in VTE/wound complication rate between the calcification and no-calcification groups of 12%, we needed to review 316 TKAs total. This 12% difference was based on study findings of a 25% complication rate in PVD patients who underwent tourniquet-assisted TKA, and the rate of VTE/wound complication after TKA in patients overall, which can be up to 12%.^7,13,14 We exceeded minimal enrollment and had 461 TKAs. Descriptive statistics were reported, with means and ranges provided where appropriate. Independent t test was used to evaluate the differences in continuous data (age) between the groups. Univariate analysis (using Pearson χ² and Fisher exact tests) and multivariate logistic regression analysis were used to evaluate the effects of categorical variables (sex, comorbidity, calcification [presence, absence], and location of calcification [proximal only, distal only, both]) on wound complication and VTE rates. All tests were 2-tailed and performed with a type I error rate of 0.05. Data analysis was performed with SPSS Version 19.0 (SPSS).

Results

Patient characteristics are summarized in Table 1. Of the 373 patients, 285 lacked calcification, and 88 had calcification. Mean age was 67.73 years (range, 24-92 years) for all patients, 65.99 years (range, 24-89 years) for the no-calcification group, and 74.32 years (range, 54-92 years) for the calcification group; the calcification group demonstrated a trend toward older age, but the difference was not significantly different (P = .07). Of the 373 patients, 156 (41.82%) were male: 110 in the no-calcification group (38.60%) and 46 in the calcification group (52.27%); sex was significantly (P = .002) different between groups, with more males in the calcification group.

Data on total preoperative comorbidities are summarized in Table 2. Hypertension, hyperlipidemia, diabetes, and coronary artery disease (CAD) were the most common comorbidities, and they were all significantly (P ≤ .05) increased in the calcification group.

No patients had reported arterial complications, such as arterial bleeding, aneurysm, intimal tears, or loss of distal pulses. Wound complication after TKA was detected in 3.04% of all cases (Table 3). Rate of DVT after TKA was 2.60% of all cases, and rate of pulmonary embolism after TKA was 2.17% of all cases. Of the 96 TKAs with preoperative radiographic evidence of calcification, 47 (48.96%) had proximal calcification only, 11 (11.46%) had distal calcification only, and 38 (39.58%) had both proximal and distal calcification (Table 4). There was no significant difference between the rate of wound complication or VTE based on location of vascular calcification.

Univariate analysis demonstrated that presence of arterial knee calcification did not increase the risk for postoperative wound complication (odds ratio [OR], 1.04; 95% confidence interval [CI], 0.28-3.80; P > .05) (Table 5). Location of arterial knee calcification also did not increase the risk for postoperative wound complication. In addition, univariate analysis demonstrated that presence of arterial knee calcification did not increase the risk for postoperative VTE (OR, 1.20; 95% CI, 0.43-3.36; P > .05 (Table 6).

Of the 14 wound complications, the most common infections were cellulitis (5/14 cases; 35.71%) and infected hardware that required component revision (5/14 cases; 35.71%). Mean time from TKA to infection was 137.93 days (range, 5-783 days). The most common organism grown in culture from the wound was Staphylococcus (5/14 cases; 35.71%).

Additional univariate statistical analysis revealed that presence of diabetes, hypertension, prior VTE, CAD, and male sex was linked to higher incidence of wound complication (P < .05) (Table 5). When multivariate analysis was performed, hypertension, prior VTE, and male sex remained significant (P < .05) (Table 5).

Discussion

TKA is a safe and effective procedure used to treat osteoarthritis of the knee and improve patients’ quality of life.¹⁵ About 700,000 TKAs are performed annually in the United States.¹⁶ Because of improvements in preventive medicine and medical technology, life expectancy is increasing, and TKAs are now being performed in higher numbers and in an older patient population. Over the next few decades, these developments will lead to more postoperative complications. It is projected that, by 2030, the need for TKAs in the United States will increase by 673% to 3.48 million.¹⁷ Postoperative complications are rare but unfortunately often lead to poor outcomes or even mortality.¹⁸ To help minimize the number of postoperative complications, we must understand the safety of tourniquet use in TKA. Other investigators have concluded that tourniquet use is unsafe in patients with preoperative vascular calcifications on plain radiographs.^7,8,11 The present study, designed to elucidate whether preoperative evidence of knee arterial calcification may predispose TKA patients to postoperative wound complication or VTE, had some important findings.

In our study, wound complication and VTE occurred in a considerable number of patients after TKA. Despite exceeding the number of patients calculated by the power analysis, our population may have been inadequate to fully detect statistical significance. Thus, our conclusion of failing to reject the null hypothesis may have been because of sample size, a type II error. We found that, after primary TKA, 3.04% of patients developed wound complications and 4.77% VTE. According to the literature, the incidence of infection after primary TKA is between 0.5% and 12%, and that of VTE reported within 3 months after TKA is 1.3% to 10%.^13,14 Although we had 100% VTE prophylaxis, meeting the standard of care, VTE after TKA remains a postoperative complication.¹⁹ This study also found that a considerable percentage of primary TKA patients (23.59%) had preoperative calcification of the knee arteries. To our knowledge, this study was the first to quantify the incidence of knee arterial calcification in patients who underwent TKA.

Preoperative calcification of the knee arteries in patients who underwent TKA did not increase the risk for wound complication, VTE, or arterial damage. These calcifications, however, do pose an increased systemic vascular risk.²⁰ Calcification of the vascular wall predicts increased cardiovascular risk, independent of classical cardiovascular risk factors.^3,18,21-24 Clinically, patients who have both diabetes and calcifications are at significant excess risk for total mortality, stroke mortality, and cardiovascular mortality, compared with patients with diabetes but without such calcifications. They also had a significantly higher incidence of coronary heart disease events, stroke events, and lower extremity amputations.^25,26

All our patients underwent tourniquet-assisted TKA. Although previous studies have indicated that tourniquet use may increase arterial complications and wound complications or even limb loss in patients with calcified arteries, we did not find this link.^7,27 Our population had no reported arterial complications related to tourniquet use. Other, smaller studies have had similar findings. Vandenbussche and colleagues²⁸ prospectively studied 80 TKA cases randomized to tourniquet use or no tourniquet use and found no postoperative nerve palsies, wound infections, wound healing problems, or hematomas. Our study is also in accord with studies that have reported tourniquet use did not increase risk for DVT.²⁹ Therefore, unlike earlier data, our data demonstrated that tourniquet use in patients with knee arterial calcification was safe.^7,27,30,31

Patients with calcification were more likely to have the medical comorbidities of hypertension, diabetes, hyperlipidemia, and CAD. All these comorbidities are linked to the development of arterial calcification, or atherosclerotic occlusive disease.^32,33 As life expectancy and the need for TKA increase, it is likely that a larger percentage of TKA patients will have preoperative radiographic evidence of knee arterial calcification. Although current dogma is that tourniquet-assisted TKA is contraindicated for patients with preoperative radiographic evidence of femoral-popliteal calcification, our study results showed that this calcification should not affect preoperative TKA planning for these patients.

We divided our patients into 3 categories: those with proximal calcification (above the joint line), those with distal calcification (below the joint line), and those with both proximal and distal calcification. Location of arterial calcification did not have an effect on their rates of postoperative wound complication or VTE. We hypothesized that patients with proximal calcification would be at increased risk for direct arterial injury and subsequent wound complication because the tourniquet is placed proximally. Previous research has indicated that arterial occlusion and subsequent wound complication can occur because of low blood flow stemming from tourniquet use.⁷ Further, intraoperative manipulation (flexing) of a knee with calcified vessels causes arterial complications after TKA because these vessels are less elastic than nonatheromatous vessels.³¹ However, we found no such effect. At the same time, having arterial calcification might also be an indication of venous disease in this location,¹² which may be especially important for proximal calcifications. Proximal DVT more likely is a precursor to pulmonary embolic events than distal DVT is.^31,34 However, we found no difference in VTE rates among the 3 arterial location groups, which is supported by studies that have found that tourniquet use does not increase DVT incidence.^29,35-40

Risk for wound complications was higher in male patients and in patients with diabetes, prior VTE, hypertension, or CAD. This finding is important because, with the increasing age of patients who undergo TKA, those with serious medical comorbidities will continue to need and have this surgery.¹⁷ Diabetes may increase the rate of wound complication because patients with diabetes have poor microcirculation, poor collagen synthesis, and reduced wound strength.⁴¹ Malinzak and colleagues⁴² demonstrated that, compared with patients without diabetes, those with diabetes had a significantly higher risk for infection after TKA. Prior VTE, specifically DVT, may increase the rate of wound complication because after DVT the deep veins may be damaged and exhibit valvular dysfunction. Labropoulos and colleagues⁴³ showed that DVT history was strongly associated with ulcer nonhealing. Perhaps hypertension has been overlooked as a risk factor for wound complication in TKA. No previous studies have assessed the link between hypertension and wound complications after TKA. However, a study of wound healing after total hip arthroplasty found that, compared with normotensive patients, hypertensive patients had delayed wound healing, putting them at higher risk for infection.⁴⁴ In addition, we found that patients with CAD were at increased risk for wound complications—an unexpected finding, as CAD traditionally is not a risk factor for infection or poor wound healing. Recently, however, CAD was identified as an independent risk factor for surgical site infections in posterior lumbar–instrumented arthrodesis.⁴⁵ The etiology of this association is unknown. Also, male patients were at increased risk for wound complication. Male sex has been implicated as an independent risk factor for development of surgical site infections and has been established as an important predisposing factor for periprosthetic joint infections.⁴⁶

It is possible that patients who present with diabetes, VTE, hypertension, or CAD before TKA should have a consultation with a vascular surgeon or should have TKA performed without a tourniquet, but this conclusion cannot be considered definitive without a large prospective randomized trial or possibly registry data. Our data indicate that patients with these comorbidities have higher rates of wound complications irrespective of preoperative radiographic calcifications. On the basis of our study results, however, we certainly recommend that patients with these risk factors have preoperative medical optimization. Orthopedic surgeons should take a thorough history and perform a meticulous physical examination on these patients to look for evidence of PVD. We recommend that, if vascular claudication is elicited in the history, or if there is evidence of peripheral arterial disease—such as hair loss, skin discoloration, dystrophic nail changes, or absent or unequal peripheral pulses—the ankle-brachial index test should be performed. If the index value is less than 0.9, then a preoperative vascular surgery consultation should be obtained.

This study had some weaknesses. First, it was retrospective, so it is possible that some wound or VTE complications were not reported and thus not found in the paper charts or electronic medical records. Some patients may have had VTE diagnostic scans at other hospitals, and their results may not have been recorded across databases. Moreover, some patients may have seen wound specialists for wound infections or wound healing problems, and these may not have been reported to the orthopedic surgeons. Second, though our patient population was not small, it may not have been of adequate size to fully detect statistical significance. We met our enrollment numbers based on our sample size calculations from an a priori power analysis; however, we still draw conclusions with the possibility of committing a type II error in mind by failing to reject the null hypothesis when in reality a statistically significant difference does exist. Third, none of our consecutive patients carried the preoperative diagnosis of PVD, and none had preoperative vascular surgery. Therefore, though calcifications were noted on radiographs, clinically our patients were asymptomatic with respect to vascular health. Last, the 2 groups were not randomized. All patients underwent tourniquet-assisted TKA.           

Conclusion

To our knowledge, this is the largest study to examine the effect of preoperative knee arterial calcification on wound complication and VTE after tourniquet-assisted TKA. Contrary to previously published recommendations, we conclude that TKA can be safely performed with a tourniquet in the presence of preoperative radiographic evidence of such calcification. However, we recommend that patients with diabetes, hypertension, CAD, or prior VTE undergo an appropriate physical examination to elicit any signs or symptoms of vascular disease. If before surgery there is any question of vascular competence, a vascular surgeon should be consulted.

Tourniquets are often used in total knee arthroplasty (TKA) to improve visualization of structures, shorten operative time, reduce intraoperative bleeding, and improve cementing technique. Despite these advantages, controversy remains regarding the safety of tourniquet use. Tourniquets have been associated with nerve palsies, vascular injury, and muscle damage.^1-5 Some have hypothesized they may cause venous stasis or direct endothelial damage that may develop into deep vein thrombosis (DVT). Abdel-Salam and Eyres⁶ found an increased incidence of postoperative wound complications and DVTs associated with tourniquet use.

Moreover, investigators have analyzed the role of tourniquets in populations at high risk for wound complications. DeLaurentis and colleagues⁷ performed a prospective and retrospective analysis of 1182 TKA patients, 24 (2%) of whom had preexisting peripheral vascular disease (PVD), defined as a history of arterial insufficiency, absent dorsalis pedis and/or absent posterior tibial pulsations, and arterial calcifications. A tourniquet was used in each case. Arterial complications occurred in 6 of the 24 patients with PVD. As expected, the authors found that a history of intermittent claudication, pain at rest, and arterial ulcers resulted in a high risk for vascular complications. Further studies have supported this finding and expanded the list of predisposing factors to include previous vascular surgery and absent and asymmetric pedal pulsations.^7-11 Of particular concern to total joint arthroplasty surgeons was the finding by DeLaurentis and colleagues⁷ that patients with radiographic evidence of calcification of the distal superficial femoral artery and/or popliteal artery were at risk for arterial complications. This finding is also supported by other studies.^8,11 In TKA, damage to arterial structures proximal to the surgical field could manifest as impaired postoperative wound healing or an ischemic limb. Wound healing depends on adequate blood flow to the healing tissue, and any damage to arterial or venous structures can theoretically compromise this process.

Added to vascular/wound complications as concerning complications in orthopedic surgery is venous thromboembolism (VTE). The role of tourniquets in the formation of VTEs is controversial. A tourniquet has the potential to increase the risk for DVT because of the stasis of venous blood in the lower limb or possible damage to calcified blood vessels. Callam and colleagues¹² studied the connection between artery disease and chronic leg ulcers and found that half the patients diagnosed with peripheral artery disease also had stigmata of chronic venous insufficiency. Therefore, the entities can occur in tandem, and surgeons should keep this in mind.

Here we report on a study we conducted to determine whether tourniquet use in TKA in patients with preexisting radiographic evidence of vascular disease increases the risk for wound complications or VTE.

Patients and Methods

We retrospectively reviewed 461 consecutive primary TKAs (373 patients) performed between January 2007 and June 2012 by 2 attending orthopedic surgeons specializing in adult reconstruction. Medical records and operative reports of 583 patients were examined after receiving institutional review board approval. Of these patients, 373 (64%) had a minimum of 12-month follow-up data available. Twelve months was deemed long enough to discover wound complications or DVTs secondary to the index procedure. Most of these outcomes manifest within the first 3 months after surgery and certainly by 12 months. Follow-up longer than 12 months may become a confounder, as wound complications outside the acute to subacute postoperative window could be related to patients’ underlying PVD and not directly to tourniquet use during surgery. Patient demographics and comorbidities were recorded. Comorbidities were obtained from preoperative medical evaluations and surgeons’ preoperative evaluations. All patients had preoperative palpable dorsalis pedis and posterior tibialis arterial pulses. No patient required preoperative vascular studies based on preoperative examination or comorbidities. No patient had prior vascular bypass surgery or stenting.

TKA was performed in a nonlaminar flow, positive-pressure, high-efficiency particulate air-filtered room with sterile toga/surgical helmet systems. For all patients, a pneumatic thigh tourniquet was applied, and the patient was prepared and draped. After limb exsanguination using a rubber bandage, the limb was elevated and the tourniquet inflated to a pressure of 250 to 300 mm Hg. The tourniquet was released either just before closure or immediately after closure in all cases; it was always let down before placement of final bandages.

Prophylactic chemical anticoagulation consisting of warfarin, aspirin, or enoxaparin was used in all patients and continued for 4 to 6 weeks after surgery. All patients received mechanical DVT prophylaxis with sequential compression devices, and all were mobilized out of bed beginning either the day of surgery or the next day. All patients received perioperative intravenous antibiotics, with the preoperative dose given before tourniquet inflation and the last postoperative dose stopped within 24 hours of surgery.

All patients who had primary TKA underwent preoperative medical evaluation and optimization. The patient’s hospital course was monitored closely, and complications noted by the orthopedic team were documented. Follow-up documentation was retrospectively reviewed for evidence of wound complications or VTE. Wound complications were defined as cellulitis, delayed wound healing, wound dehiscence, and/or periprosthetic joint infection. In the case of VTE, physical examination findings were not sufficient for inclusion. Venous duplex ultrasonography demonstrating the clot was reviewed before inclusion.

Preoperative radiographs were examined for arterial calcification (Figure). We refer to calcification seen above the knee joint as proximal calcification and to calcification observed below the joint as distal calcification. Patients exhibited calcification proximally only, distally only, or both proximally and distally. The 373 patients were placed into 2 groups based on whether they had preoperative arterial calcification on plain radiography of the knee. One group (285 patients with no radiographic evidence of preoperative knee arterial calcification) underwent 365 TKAs, and the other group (88 patients with radiographic evidence of preoperative knee arterial calcification) underwent 96 TKAs.

A sample size calculation was performed to determine how many patients were needed in each group with 80% power and an α of 0.05. With an estimated difference in VTE/wound complication rate between the calcification and no-calcification groups of 12%, we needed to review 316 TKAs total. This 12% difference was based on study findings of a 25% complication rate in PVD patients who underwent tourniquet-assisted TKA, and the rate of VTE/wound complication after TKA in patients overall, which can be up to 12%.^7,13,14 We exceeded minimal enrollment and had 461 TKAs. Descriptive statistics were reported, with means and ranges provided where appropriate. Independent t test was used to evaluate the differences in continuous data (age) between the groups. Univariate analysis (using Pearson χ² and Fisher exact tests) and multivariate logistic regression analysis were used to evaluate the effects of categorical variables (sex, comorbidity, calcification [presence, absence], and location of calcification [proximal only, distal only, both]) on wound complication and VTE rates. All tests were 2-tailed and performed with a type I error rate of 0.05. Data analysis was performed with SPSS Version 19.0 (SPSS).

Results

Patient characteristics are summarized in Table 1. Of the 373 patients, 285 lacked calcification, and 88 had calcification. Mean age was 67.73 years (range, 24-92 years) for all patients, 65.99 years (range, 24-89 years) for the no-calcification group, and 74.32 years (range, 54-92 years) for the calcification group; the calcification group demonstrated a trend toward older age, but the difference was not significantly different (P = .07). Of the 373 patients, 156 (41.82%) were male: 110 in the no-calcification group (38.60%) and 46 in the calcification group (52.27%); sex was significantly (P = .002) different between groups, with more males in the calcification group.

Data on total preoperative comorbidities are summarized in Table 2. Hypertension, hyperlipidemia, diabetes, and coronary artery disease (CAD) were the most common comorbidities, and they were all significantly (P ≤ .05) increased in the calcification group.

No patients had reported arterial complications, such as arterial bleeding, aneurysm, intimal tears, or loss of distal pulses. Wound complication after TKA was detected in 3.04% of all cases (Table 3). Rate of DVT after TKA was 2.60% of all cases, and rate of pulmonary embolism after TKA was 2.17% of all cases. Of the 96 TKAs with preoperative radiographic evidence of calcification, 47 (48.96%) had proximal calcification only, 11 (11.46%) had distal calcification only, and 38 (39.58%) had both proximal and distal calcification (Table 4). There was no significant difference between the rate of wound complication or VTE based on location of vascular calcification.

Univariate analysis demonstrated that presence of arterial knee calcification did not increase the risk for postoperative wound complication (odds ratio [OR], 1.04; 95% confidence interval [CI], 0.28-3.80; P > .05) (Table 5). Location of arterial knee calcification also did not increase the risk for postoperative wound complication. In addition, univariate analysis demonstrated that presence of arterial knee calcification did not increase the risk for postoperative VTE (OR, 1.20; 95% CI, 0.43-3.36; P > .05 (Table 6).

Of the 14 wound complications, the most common infections were cellulitis (5/14 cases; 35.71%) and infected hardware that required component revision (5/14 cases; 35.71%). Mean time from TKA to infection was 137.93 days (range, 5-783 days). The most common organism grown in culture from the wound was Staphylococcus (5/14 cases; 35.71%).

Additional univariate statistical analysis revealed that presence of diabetes, hypertension, prior VTE, CAD, and male sex was linked to higher incidence of wound complication (P < .05) (Table 5). When multivariate analysis was performed, hypertension, prior VTE, and male sex remained significant (P < .05) (Table 5).

Discussion

TKA is a safe and effective procedure used to treat osteoarthritis of the knee and improve patients’ quality of life.¹⁵ About 700,000 TKAs are performed annually in the United States.¹⁶ Because of improvements in preventive medicine and medical technology, life expectancy is increasing, and TKAs are now being performed in higher numbers and in an older patient population. Over the next few decades, these developments will lead to more postoperative complications. It is projected that, by 2030, the need for TKAs in the United States will increase by 673% to 3.48 million.¹⁷ Postoperative complications are rare but unfortunately often lead to poor outcomes or even mortality.¹⁸ To help minimize the number of postoperative complications, we must understand the safety of tourniquet use in TKA. Other investigators have concluded that tourniquet use is unsafe in patients with preoperative vascular calcifications on plain radiographs.^7,8,11 The present study, designed to elucidate whether preoperative evidence of knee arterial calcification may predispose TKA patients to postoperative wound complication or VTE, had some important findings.

In our study, wound complication and VTE occurred in a considerable number of patients after TKA. Despite exceeding the number of patients calculated by the power analysis, our population may have been inadequate to fully detect statistical significance. Thus, our conclusion of failing to reject the null hypothesis may have been because of sample size, a type II error. We found that, after primary TKA, 3.04% of patients developed wound complications and 4.77% VTE. According to the literature, the incidence of infection after primary TKA is between 0.5% and 12%, and that of VTE reported within 3 months after TKA is 1.3% to 10%.^13,14 Although we had 100% VTE prophylaxis, meeting the standard of care, VTE after TKA remains a postoperative complication.¹⁹ This study also found that a considerable percentage of primary TKA patients (23.59%) had preoperative calcification of the knee arteries. To our knowledge, this study was the first to quantify the incidence of knee arterial calcification in patients who underwent TKA.

Preoperative calcification of the knee arteries in patients who underwent TKA did not increase the risk for wound complication, VTE, or arterial damage. These calcifications, however, do pose an increased systemic vascular risk.²⁰ Calcification of the vascular wall predicts increased cardiovascular risk, independent of classical cardiovascular risk factors.^3,18,21-24 Clinically, patients who have both diabetes and calcifications are at significant excess risk for total mortality, stroke mortality, and cardiovascular mortality, compared with patients with diabetes but without such calcifications. They also had a significantly higher incidence of coronary heart disease events, stroke events, and lower extremity amputations.^25,26

All our patients underwent tourniquet-assisted TKA. Although previous studies have indicated that tourniquet use may increase arterial complications and wound complications or even limb loss in patients with calcified arteries, we did not find this link.^7,27 Our population had no reported arterial complications related to tourniquet use. Other, smaller studies have had similar findings. Vandenbussche and colleagues²⁸ prospectively studied 80 TKA cases randomized to tourniquet use or no tourniquet use and found no postoperative nerve palsies, wound infections, wound healing problems, or hematomas. Our study is also in accord with studies that have reported tourniquet use did not increase risk for DVT.²⁹ Therefore, unlike earlier data, our data demonstrated that tourniquet use in patients with knee arterial calcification was safe.^7,27,30,31

Patients with calcification were more likely to have the medical comorbidities of hypertension, diabetes, hyperlipidemia, and CAD. All these comorbidities are linked to the development of arterial calcification, or atherosclerotic occlusive disease.^32,33 As life expectancy and the need for TKA increase, it is likely that a larger percentage of TKA patients will have preoperative radiographic evidence of knee arterial calcification. Although current dogma is that tourniquet-assisted TKA is contraindicated for patients with preoperative radiographic evidence of femoral-popliteal calcification, our study results showed that this calcification should not affect preoperative TKA planning for these patients.

We divided our patients into 3 categories: those with proximal calcification (above the joint line), those with distal calcification (below the joint line), and those with both proximal and distal calcification. Location of arterial calcification did not have an effect on their rates of postoperative wound complication or VTE. We hypothesized that patients with proximal calcification would be at increased risk for direct arterial injury and subsequent wound complication because the tourniquet is placed proximally. Previous research has indicated that arterial occlusion and subsequent wound complication can occur because of low blood flow stemming from tourniquet use.⁷ Further, intraoperative manipulation (flexing) of a knee with calcified vessels causes arterial complications after TKA because these vessels are less elastic than nonatheromatous vessels.³¹ However, we found no such effect. At the same time, having arterial calcification might also be an indication of venous disease in this location,¹² which may be especially important for proximal calcifications. Proximal DVT more likely is a precursor to pulmonary embolic events than distal DVT is.^31,34 However, we found no difference in VTE rates among the 3 arterial location groups, which is supported by studies that have found that tourniquet use does not increase DVT incidence.^29,35-40

Risk for wound complications was higher in male patients and in patients with diabetes, prior VTE, hypertension, or CAD. This finding is important because, with the increasing age of patients who undergo TKA, those with serious medical comorbidities will continue to need and have this surgery.¹⁷ Diabetes may increase the rate of wound complication because patients with diabetes have poor microcirculation, poor collagen synthesis, and reduced wound strength.⁴¹ Malinzak and colleagues⁴² demonstrated that, compared with patients without diabetes, those with diabetes had a significantly higher risk for infection after TKA. Prior VTE, specifically DVT, may increase the rate of wound complication because after DVT the deep veins may be damaged and exhibit valvular dysfunction. Labropoulos and colleagues⁴³ showed that DVT history was strongly associated with ulcer nonhealing. Perhaps hypertension has been overlooked as a risk factor for wound complication in TKA. No previous studies have assessed the link between hypertension and wound complications after TKA. However, a study of wound healing after total hip arthroplasty found that, compared with normotensive patients, hypertensive patients had delayed wound healing, putting them at higher risk for infection.⁴⁴ In addition, we found that patients with CAD were at increased risk for wound complications—an unexpected finding, as CAD traditionally is not a risk factor for infection or poor wound healing. Recently, however, CAD was identified as an independent risk factor for surgical site infections in posterior lumbar–instrumented arthrodesis.⁴⁵ The etiology of this association is unknown. Also, male patients were at increased risk for wound complication. Male sex has been implicated as an independent risk factor for development of surgical site infections and has been established as an important predisposing factor for periprosthetic joint infections.⁴⁶

It is possible that patients who present with diabetes, VTE, hypertension, or CAD before TKA should have a consultation with a vascular surgeon or should have TKA performed without a tourniquet, but this conclusion cannot be considered definitive without a large prospective randomized trial or possibly registry data. Our data indicate that patients with these comorbidities have higher rates of wound complications irrespective of preoperative radiographic calcifications. On the basis of our study results, however, we certainly recommend that patients with these risk factors have preoperative medical optimization. Orthopedic surgeons should take a thorough history and perform a meticulous physical examination on these patients to look for evidence of PVD. We recommend that, if vascular claudication is elicited in the history, or if there is evidence of peripheral arterial disease—such as hair loss, skin discoloration, dystrophic nail changes, or absent or unequal peripheral pulses—the ankle-brachial index test should be performed. If the index value is less than 0.9, then a preoperative vascular surgery consultation should be obtained.

This study had some weaknesses. First, it was retrospective, so it is possible that some wound or VTE complications were not reported and thus not found in the paper charts or electronic medical records. Some patients may have had VTE diagnostic scans at other hospitals, and their results may not have been recorded across databases. Moreover, some patients may have seen wound specialists for wound infections or wound healing problems, and these may not have been reported to the orthopedic surgeons. Second, though our patient population was not small, it may not have been of adequate size to fully detect statistical significance. We met our enrollment numbers based on our sample size calculations from an a priori power analysis; however, we still draw conclusions with the possibility of committing a type II error in mind by failing to reject the null hypothesis when in reality a statistically significant difference does exist. Third, none of our consecutive patients carried the preoperative diagnosis of PVD, and none had preoperative vascular surgery. Therefore, though calcifications were noted on radiographs, clinically our patients were asymptomatic with respect to vascular health. Last, the 2 groups were not randomized. All patients underwent tourniquet-assisted TKA.           

Conclusion

To our knowledge, this is the largest study to examine the effect of preoperative knee arterial calcification on wound complication and VTE after tourniquet-assisted TKA. Contrary to previously published recommendations, we conclude that TKA can be safely performed with a tourniquet in the presence of preoperative radiographic evidence of such calcification. However, we recommend that patients with diabetes, hypertension, CAD, or prior VTE undergo an appropriate physical examination to elicit any signs or symptoms of vascular disease. If before surgery there is any question of vascular competence, a vascular surgeon should be consulted.

Wound complications (eg, delayed wound healing, blisters, prolonged drainage) have been reported in up to 30% of patients who undergo elective total joint arthroplasty (TJA).^1-6 Wound complications increase resource utilization, lengthen hospital stays, and increase costs.^7-9 Prolonged wound healing and persistent wound drainage are also harbingers of both superficial and deep surgical site infections.^5-11

In several studies, wound complications after TJA were the primary reason for hospital readmissions.^12-15 As part of the Patient Protection and Affordable Care Act, hospitals will be penalized by the Centers for Medicaid & Medicare Services for unplanned hospital readmissions within 30 days after TJA. It is imperative, then, to reduce the risk factors and complications associated with surgical site infections to decrease unplanned readmissions.

Historically, little attention has been given to the role of surgical dressings and the effect of dressings on wound healing. Although many subspecialties (eg, cardiothoracic surgery, general surgery) have reported benefits in using occlusive dressings, adoption in TJA has been slow.^16-18 At our institution about 5 years ago, we began using an occlusive silver-impregnated barrier dressing based on preliminary data from studies showing benefits of occlusive dressings in TJA.^19,20

We conducted a study to determine if use of occlusive antimicrobial barrier dressings decreases rates of wound complications in TJA. We had 3 research questions: Compared with standard surgical dressings, are occlusive dressings associated with decreased rates of wound complications after TJA? Is there a difference in number of dressing changes required between the 2 dressing types? Is satisfaction higher for patients with occlusive dressings than for patients with standard dressings?

Patients and Methods

This randomized controlled trial (RCT) was reviewed and approved by the Institutional Review Board at Carolinas Healthcare. Patients were randomized by the research staff using a parallel, 1:1 allocation method. The randomization table was generated using a random number generator.

An a priori sample size estimate was made using a 2-tailed Fisher exact test with a .05 level of significance. Based on a study by Clarke and colleagues,²¹ we estimated the incidence of wound problems at 3% in the occlusive dressing (study) group and 13% in the standard dressing (control) group. We determined that 260 participants (130 per group) would be needed to achieve 80% power. We considered a 15% attrition rate for a total enrollment goal of 300 study participants (150 per group).

Between December 2010 and January 2013, patients presenting for either primary total hip arthroplasty (THA) or primary total knee arthroplasty (TKA) were recruited to participate in the study. Eligibility criteria (Table 1) were reviewed, and patients were enrolled by the senior surgeons, Dr. Springer, Dr. Beaver, Dr. Griffin, and Dr. Mason. All eligible participants who provided informed consent were randomized to receive either an occlusive antimicrobial barrier dressing (Aquacel Ag, ConvaTec) or standard surgical dressing (Primapore, Smith & Nephew). The occlusive dressing (Figure 1) consists of an outer barrier layer of hydrocolloid and a central island of hydrofiber, which absorbs and locks in any wound exudate within the fibers and prevents the creation of an overly moist wound environment that can lead to skin maceration and wound breakdown. In addition, the hydrofibers are embedded with ionic silver, which is released only at the site of wound exudate, or drainage; thus, there is no continuous exposure of the entire wound to silver. The standard dressing (Figure 2) consists of a central island of gauze enclosed in low-allergy acrylic adhesive tape.

All surgical dressings were placed over a closed incision in a sterile environment in the operating room after the procedure. The groups’ wound closures were identical.

A posterior approach was used for all THAs. The deep fascia was closed with a running barbed suture (Quill, Angiotech), the deep subcutaneous tissue with No. 1 Vicryl suture (Ethicon), and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch (Ethicon) was placed in the subcuticular layer and was followed with a skin adhesive (Dermabond, Ethicon). A closed suction drain, removed on postoperative day (POD) 1, was used for all THAs.

A standard medial parapatellar arthrotomy was used for all TKAs. The arthrotomy was closed with a running barbed suture, the deep subcutaneous tissue with No. 1 Vicryl suture, and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch was placed in the subcuticular layer and was followed with a skin adhesive. A closed suction drain was also used. In addition, a compressive wrap was placed over the dressing in the operating room and was removed the next morning. During the hospital stay, the surgical site was evaluated daily with a standard wound evaluation form.

 In the standard dressing group, the bandage was removed for wound evaluation on POD 2, and the dressing was changed every other day during the hospital stay. The dressing was also changed as needed for wound drainage (Figure 3) or other minor wound-healing concerns.

In the occlusive dressing group, the dressing design allowed the dressing to remain in place for about 7 days. It was removed by a home health nurse during a visit closest to but not before the 7-day mark. In addition, it was changed at surgeon discretion if there were concerns about wound drainage or wound healing. For the occlusive barrier, wound drainage was evaluated by strike-through of drainage on the back side of the dressing (Figure 4). If more than 50% of the dressing was saturated, the bandage was changed and the wound evaluated. If there were no immediate concerns about wound complications (eg, infection, blistering), a new occlusive dressing was placed. Because the occlusive dressing was waterproof, patients in the study group were able to shower immediately after surgery. In the control group, patients were allowed to shower if the surgical dressing was kept dry, as the bandage was not waterproof.

Per the study protocol, all patients were discharged home and followed by a single home health agency. Mean hospital stay was 3 days (range, 0-8 days), which did not differ significantly between groups (P = .133). All home health nurses were trained in evaluation of postsurgical wounds and were aware of the study requirements. The nurses visited all patients 3 days a week until the scheduled 4-week postoperative follow-up with the treating physician or physician assistant. At each visit, the nurse evaluated the wound and surrounding skin using a standard wound document. Dressings were changed based on the criteria we have described. Concerns about wound status (eg, drainage, blistering, erythema) prompted removal of the dressing for further evaluation. The physician was notified of concerns about wound healing, which prompted an office visit for evaluation. The dressing remained in place for a minimum of 7 days but in all cases was removed as close to 7 days as possible, depending on the scheduled nursing visits. Once uneventful wound healing was complete, no further dressing was required. A final wound evaluation was conducted by the surgeon at the 4-week postoperative evaluation.

The primary outcome measure was wound complication (dichotomous variable). Wounds were assessed by describing the amount, type, and color of exudate (Figure 5). The appearance of the wound margins and the surrounding skin was also assessed. Because wounds could not be directly visualized in the occlusive dressing group, drainage (indicated by strike-through) was used as a measure of possible wound complications, prompting removal and full evaluation.

 Secondary endpoints included additional wound treatment or surgical procedures for wound complications, number of dressing changes, and patient satisfaction. Patients completed a satisfaction questionnaire at each wound assessment (Figure 6). Using a visual analog scale (VAS), they rated their satisfaction with their ability to perform activities of daily living (personal hygiene, change clothes, sit comfortably, sleep comfortably), drawing a line on the VAS at a point between 0 (totally unsatisfied) and 100 (totally satisfied) for each satisfaction measure. This line was measured and recorded by the study coordinator. The 4 satisfaction measures were averaged for a composite satisfaction measure.

All statistical analyses were conducted using SAS Version 9.2 (SAS Institute). Standard univariate descriptive statistics (means, standard deviations, frequencies, proportions) were calculated and reported. Differences in mean values for continuous data were assessed with independent t test or Wilcoxon rank sum test. Chi-square test and Fisher exact test were used to determine differences between groups for categorical or dichotomous variables. A significance level of .05 was used for all statistical tests.

Results

The 300 patients who consented to participate in the study were randomized to receive either occlusive dressing or standard dressing. After randomization, 38 patients (15 occlusive, 23 standard) were withdrawn from the study (Table 2), leaving a final dataset of 262 patients, 141 in the occlusive group (67 THAs, 74 TKAs) and 121 in the standard group (49 THAs, 72 TKAs). There were no differences in proportion of THAs or TKAs, age, sex, or body mass index between the occlusive and standard groups (Table 3).

There were statistically significantly (P = .015) fewer wound complications in the occlusive dressing group (10%) than in the standard dressing group (22%). Blisters at or around the wound site were reported in significantly (P = .026) fewer patients with occlusive dressing (1/141, 0.7%) than standard dressing (7/121, 6%). Additional wound care was required in 9 patients (7%) in the standard group and 6 patients (4%) in the occlusive group (P = .27). Two patients (1.7%) in the standard group were readmitted for treatment of wound dehiscence; no one in the occlusive group was readmitted to the hospital or had to return to the operating room for treatment of a wound complication. The difference was not statistically significant (P = .13). There were also no significant (P = .81) differences in rate of wound complications between THA and TKA patients.

There were statistically significantly (P < .0001) fewer dressing changes in the occlusive dressing group. Mean number of dressing changes was 0.14 (median, 0; interquartile range, 0-0) in the occlusive group and 2.8 (median, 2; interquartile range, 1-3) in the standard group.

Compared with patients in the standard dressing group, patients in the occlusive dressing group reported significantly higher satisfaction scores. Mean overall patient satisfaction score was 92 in the occlusive group and 81 in the standard group (P < .0001). Patients in the occlusive group were more satisfied with their ability to take care of their personal hygiene, to change clothes, and to sit and sleep comfortably (Table 4).

Discussion

Wound complications after TJA are common, occurring in up to 30% of patients,^1-6 and are associated with development of superficial and deep surgical site infections, increased resource utilization, and longer hospital stays.^5-11 Although the role of surgical dressings has received little attention in TJA practice, other subspecialties have found that occlusive barrier dressings can reduce wound complications and promote wound healing.^16,17 Mitotic cell division and leukocyte activity, which are critical in wound healing, increase under occlusive dressings. This cellular activity is disrupted with every dressing change, delaying wound healing (biological activity takes 3-4 hours to resume).²² In addition, occlusive dressings increase hypoxia, which promotes angiogenesis and accelerates wound healing.²³

Despite being a prospective RCT, this study had several limitations. Because of the need to evaluate wounds and obvious differences between the 2 dressings (eg, color, ability to shower), it was not possible to blind the patient or surgeon to the dressing used. When rating satisfaction, patients were not able to directly compare the 2 dressings. The primary endpoint of the study was the complication rate; however, the deep periprosthetic infection rate may be a superior endpoint and would require a much larger study. Although we assumed that wound complications may be harbingers for periprosthetic infections, no patient in either group developed periprosthetic infection. Therefore, we cannot conclude that surgical dressings play a role in reducing infections. In addition, as the standard dressing was changed on POD 2 (per standard protocol) and the occlusive dressing could remain in place for up to 7 days, there was a selection bias in the evaluation of the number of dressing changes. However, given the characteristics of the standard dressing (eg, tape, gauze, nonocclusive), leaving it in place after POD 2 is not optimal. Therefore, we would expect to see a difference in the number of dressing changes. We think this comparison remains valid, as occlusive dressings were changed when there were indications of wound problems (eg, excessive drainage [strike-through], surrounding erythema, blistering). With an average of less than 1 dressing change in the occlusive group, we think this is a surrogate for uneventful wound healing and decreased wound complication, and our data support this. It is also important to test both dressing durability and patient tolerance for wearing a single dressing for 7 days.

Our RCT results showed that, compared with a standard dressing, an occlusive antimicrobial dressing was associated with a significant decrease in overall wound complications and blisters. These findings are similar to those of other studies of occlusive dressings in a number of surgical subspecialties.^16,18 In an RCT of 200 patients who underwent elective and nonelective hip and knee surgery and were randomized to either absorbent perforated dressing with adhesive border (Cutiplast, Smith & Nephew) or Aquacel (ConvaTec) covered with vapor-permeable dressing (Tegaderm, 3M), Ravenscroft and colleagues²⁰ found that Aquacel-plus-Tegaderm was 5.8 times more likely than Cutiplast to produce an uncompromised wound. Similarly, in an RCT of hydrofiber (Aquacel) and central pad (Mepore, Mölnlycke) dressings after primary THA and TKA, Abuzakuk and colleagues¹⁹ found significantly fewer dressing changes (43% vs 77%) and blisters (13% vs 26%) in the hydrofiber group than in the pad group.

Hopper and colleagues²⁴ compared 50 consecutive patients treated with modern dressings (Aquacel) with 50 historical control patients treated with traditional surgical dressings (Mepore). Blisters developed in 20% of the patients in the traditional group and 4% of patients in the modern group (P = .028). The authors concluded that adverse outcomes of wound healing can be minimized with modern dressings.

A recent retrospective study by Cai and colleagues²⁵ evaluated the incidence of acute periprosthetic infection (≤3 months after surgery) with use of occlusive (Aquacel) and standard dressings. Incidence of acute periprosthetic infection was 0.44% in the occlusive group and 1.7% in the standard group (P = .005). Incidence of wound-healing problems was not evaluated.

Our second aim in the present study was to evaluate the number of dressing changes required. There were significantly fewer dressing changes in the occlusive dressing group than in the standard dressing group. Therefore, wear time (amount of time a single dressing remains in place) was substantially longer for the occlusive group. In the study by Hopper and colleagues,²⁴ wear time was significantly shorter for the traditional dressing than for the modern dressing (2 vs 7 days; P < .001), and the traditional dressing required more changes (3 vs 0; P < .001).

These findings are important for several reasons. Standard surgical dressings often require frequent changes. If left in place, they create an excessively moist wound environment that promotes blistering and delays wound healing. However, frequent dressing changes expose the wound and increase the risk for surgical site infection.²⁶ A barrier dressing left in place from time of surgery prevents bacteria from entering and contaminating a healing wound. A study by Clarke and colleagues²¹ demonstrated higher skin colonization rates for patients who had dressings changed on POD 1 than for patients who had their first dressing change on POD 6.

Our third study aim was to evaluate patient satisfaction with surgical dressings. The orthopedic literature has little on this topic.²³ Blisters and other wound complications can negatively affect satisfaction.^2,3 Our data showed significant improvement in satisfaction, particularly regarding sterility and hygiene.

Other surgical subspecialties have found similar improvement in patient satisfaction with occlusive barrier dressings. In an RCT of 88 pediatric patients, Rasmussen and colleagues²⁷ found that patients reported significantly less pain during changes of an occlusive adhesive dressing (Duoderm, ConvaTec) than during changes of a conventional Steristrip (3M) plus Cutiplast. According to the authors, the occlusive wound dressing seemed to minimize the physical and psychological trauma to the infant or child and lessen disruption of the child’s and the parents’ daily routines, because the children could be bathed immediately after surgery.

Our study did not specifically address cost. Cai and colleagues²⁵ estimated that, if the Aquacel dressing were routinely used in every hip and knee arthroplasty, it would add about $27 million in cost. However, this must be balanced by the cost of managing infection after TJA. In the United States, at an estimated $50,000 to $100,000 per case and an annual incidence of 1% to 2%, the low-end cost for the treatment of periprosthetic infection would be $500 million.²⁸ Cai and colleagues²⁵ found a 4-fold reduction in periprosthetic infection when use of occlusive dressings was implemented. In addition, wound complications remain the number one reason for hospital readmission after TJA.^12,13 Cost of hospital readmission, as well as financial penalties to institutions for unplanned readmission for wound complications, must be considered.

Conclusion

Our RCT results demonstrated that use of occlusive antimicrobial barrier dressings (vs standard surgical dressings) significantly reduced wound complications and dressing changes and improved overall patient satisfaction. These findings are similar to those in the literature on TJA and other surgical subspecialties. We conclude that occlusive surgical dressings reduce wound complications after TJA.

Wound complications (eg, delayed wound healing, blisters, prolonged drainage) have been reported in up to 30% of patients who undergo elective total joint arthroplasty (TJA).^1-6 Wound complications increase resource utilization, lengthen hospital stays, and increase costs.^7-9 Prolonged wound healing and persistent wound drainage are also harbingers of both superficial and deep surgical site infections.^5-11

In several studies, wound complications after TJA were the primary reason for hospital readmissions.^12-15 As part of the Patient Protection and Affordable Care Act, hospitals will be penalized by the Centers for Medicaid & Medicare Services for unplanned hospital readmissions within 30 days after TJA. It is imperative, then, to reduce the risk factors and complications associated with surgical site infections to decrease unplanned readmissions.

Historically, little attention has been given to the role of surgical dressings and the effect of dressings on wound healing. Although many subspecialties (eg, cardiothoracic surgery, general surgery) have reported benefits in using occlusive dressings, adoption in TJA has been slow.^16-18 At our institution about 5 years ago, we began using an occlusive silver-impregnated barrier dressing based on preliminary data from studies showing benefits of occlusive dressings in TJA.^19,20

We conducted a study to determine if use of occlusive antimicrobial barrier dressings decreases rates of wound complications in TJA. We had 3 research questions: Compared with standard surgical dressings, are occlusive dressings associated with decreased rates of wound complications after TJA? Is there a difference in number of dressing changes required between the 2 dressing types? Is satisfaction higher for patients with occlusive dressings than for patients with standard dressings?

Patients and Methods

This randomized controlled trial (RCT) was reviewed and approved by the Institutional Review Board at Carolinas Healthcare. Patients were randomized by the research staff using a parallel, 1:1 allocation method. The randomization table was generated using a random number generator.

An a priori sample size estimate was made using a 2-tailed Fisher exact test with a .05 level of significance. Based on a study by Clarke and colleagues,²¹ we estimated the incidence of wound problems at 3% in the occlusive dressing (study) group and 13% in the standard dressing (control) group. We determined that 260 participants (130 per group) would be needed to achieve 80% power. We considered a 15% attrition rate for a total enrollment goal of 300 study participants (150 per group).

Between December 2010 and January 2013, patients presenting for either primary total hip arthroplasty (THA) or primary total knee arthroplasty (TKA) were recruited to participate in the study. Eligibility criteria (Table 1) were reviewed, and patients were enrolled by the senior surgeons, Dr. Springer, Dr. Beaver, Dr. Griffin, and Dr. Mason. All eligible participants who provided informed consent were randomized to receive either an occlusive antimicrobial barrier dressing (Aquacel Ag, ConvaTec) or standard surgical dressing (Primapore, Smith & Nephew). The occlusive dressing (Figure 1) consists of an outer barrier layer of hydrocolloid and a central island of hydrofiber, which absorbs and locks in any wound exudate within the fibers and prevents the creation of an overly moist wound environment that can lead to skin maceration and wound breakdown. In addition, the hydrofibers are embedded with ionic silver, which is released only at the site of wound exudate, or drainage; thus, there is no continuous exposure of the entire wound to silver. The standard dressing (Figure 2) consists of a central island of gauze enclosed in low-allergy acrylic adhesive tape.

All surgical dressings were placed over a closed incision in a sterile environment in the operating room after the procedure. The groups’ wound closures were identical.

A posterior approach was used for all THAs. The deep fascia was closed with a running barbed suture (Quill, Angiotech), the deep subcutaneous tissue with No. 1 Vicryl suture (Ethicon), and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch (Ethicon) was placed in the subcuticular layer and was followed with a skin adhesive (Dermabond, Ethicon). A closed suction drain, removed on postoperative day (POD) 1, was used for all THAs.

A standard medial parapatellar arthrotomy was used for all TKAs. The arthrotomy was closed with a running barbed suture, the deep subcutaneous tissue with No. 1 Vicryl suture, and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch was placed in the subcuticular layer and was followed with a skin adhesive. A closed suction drain was also used. In addition, a compressive wrap was placed over the dressing in the operating room and was removed the next morning. During the hospital stay, the surgical site was evaluated daily with a standard wound evaluation form.

 In the standard dressing group, the bandage was removed for wound evaluation on POD 2, and the dressing was changed every other day during the hospital stay. The dressing was also changed as needed for wound drainage (Figure 3) or other minor wound-healing concerns.

In the occlusive dressing group, the dressing design allowed the dressing to remain in place for about 7 days. It was removed by a home health nurse during a visit closest to but not before the 7-day mark. In addition, it was changed at surgeon discretion if there were concerns about wound drainage or wound healing. For the occlusive barrier, wound drainage was evaluated by strike-through of drainage on the back side of the dressing (Figure 4). If more than 50% of the dressing was saturated, the bandage was changed and the wound evaluated. If there were no immediate concerns about wound complications (eg, infection, blistering), a new occlusive dressing was placed. Because the occlusive dressing was waterproof, patients in the study group were able to shower immediately after surgery. In the control group, patients were allowed to shower if the surgical dressing was kept dry, as the bandage was not waterproof.

Per the study protocol, all patients were discharged home and followed by a single home health agency. Mean hospital stay was 3 days (range, 0-8 days), which did not differ significantly between groups (P = .133). All home health nurses were trained in evaluation of postsurgical wounds and were aware of the study requirements. The nurses visited all patients 3 days a week until the scheduled 4-week postoperative follow-up with the treating physician or physician assistant. At each visit, the nurse evaluated the wound and surrounding skin using a standard wound document. Dressings were changed based on the criteria we have described. Concerns about wound status (eg, drainage, blistering, erythema) prompted removal of the dressing for further evaluation. The physician was notified of concerns about wound healing, which prompted an office visit for evaluation. The dressing remained in place for a minimum of 7 days but in all cases was removed as close to 7 days as possible, depending on the scheduled nursing visits. Once uneventful wound healing was complete, no further dressing was required. A final wound evaluation was conducted by the surgeon at the 4-week postoperative evaluation.

The primary outcome measure was wound complication (dichotomous variable). Wounds were assessed by describing the amount, type, and color of exudate (Figure 5). The appearance of the wound margins and the surrounding skin was also assessed. Because wounds could not be directly visualized in the occlusive dressing group, drainage (indicated by strike-through) was used as a measure of possible wound complications, prompting removal and full evaluation.

 Secondary endpoints included additional wound treatment or surgical procedures for wound complications, number of dressing changes, and patient satisfaction. Patients completed a satisfaction questionnaire at each wound assessment (Figure 6). Using a visual analog scale (VAS), they rated their satisfaction with their ability to perform activities of daily living (personal hygiene, change clothes, sit comfortably, sleep comfortably), drawing a line on the VAS at a point between 0 (totally unsatisfied) and 100 (totally satisfied) for each satisfaction measure. This line was measured and recorded by the study coordinator. The 4 satisfaction measures were averaged for a composite satisfaction measure.

All statistical analyses were conducted using SAS Version 9.2 (SAS Institute). Standard univariate descriptive statistics (means, standard deviations, frequencies, proportions) were calculated and reported. Differences in mean values for continuous data were assessed with independent t test or Wilcoxon rank sum test. Chi-square test and Fisher exact test were used to determine differences between groups for categorical or dichotomous variables. A significance level of .05 was used for all statistical tests.

Results

The 300 patients who consented to participate in the study were randomized to receive either occlusive dressing or standard dressing. After randomization, 38 patients (15 occlusive, 23 standard) were withdrawn from the study (Table 2), leaving a final dataset of 262 patients, 141 in the occlusive group (67 THAs, 74 TKAs) and 121 in the standard group (49 THAs, 72 TKAs). There were no differences in proportion of THAs or TKAs, age, sex, or body mass index between the occlusive and standard groups (Table 3).

There were statistically significantly (P = .015) fewer wound complications in the occlusive dressing group (10%) than in the standard dressing group (22%). Blisters at or around the wound site were reported in significantly (P = .026) fewer patients with occlusive dressing (1/141, 0.7%) than standard dressing (7/121, 6%). Additional wound care was required in 9 patients (7%) in the standard group and 6 patients (4%) in the occlusive group (P = .27). Two patients (1.7%) in the standard group were readmitted for treatment of wound dehiscence; no one in the occlusive group was readmitted to the hospital or had to return to the operating room for treatment of a wound complication. The difference was not statistically significant (P = .13). There were also no significant (P = .81) differences in rate of wound complications between THA and TKA patients.

There were statistically significantly (P < .0001) fewer dressing changes in the occlusive dressing group. Mean number of dressing changes was 0.14 (median, 0; interquartile range, 0-0) in the occlusive group and 2.8 (median, 2; interquartile range, 1-3) in the standard group.

Compared with patients in the standard dressing group, patients in the occlusive dressing group reported significantly higher satisfaction scores. Mean overall patient satisfaction score was 92 in the occlusive group and 81 in the standard group (P < .0001). Patients in the occlusive group were more satisfied with their ability to take care of their personal hygiene, to change clothes, and to sit and sleep comfortably (Table 4).

Discussion

Wound complications after TJA are common, occurring in up to 30% of patients,^1-6 and are associated with development of superficial and deep surgical site infections, increased resource utilization, and longer hospital stays.^5-11 Although the role of surgical dressings has received little attention in TJA practice, other subspecialties have found that occlusive barrier dressings can reduce wound complications and promote wound healing.^16,17 Mitotic cell division and leukocyte activity, which are critical in wound healing, increase under occlusive dressings. This cellular activity is disrupted with every dressing change, delaying wound healing (biological activity takes 3-4 hours to resume).²² In addition, occlusive dressings increase hypoxia, which promotes angiogenesis and accelerates wound healing.²³

Despite being a prospective RCT, this study had several limitations. Because of the need to evaluate wounds and obvious differences between the 2 dressings (eg, color, ability to shower), it was not possible to blind the patient or surgeon to the dressing used. When rating satisfaction, patients were not able to directly compare the 2 dressings. The primary endpoint of the study was the complication rate; however, the deep periprosthetic infection rate may be a superior endpoint and would require a much larger study. Although we assumed that wound complications may be harbingers for periprosthetic infections, no patient in either group developed periprosthetic infection. Therefore, we cannot conclude that surgical dressings play a role in reducing infections. In addition, as the standard dressing was changed on POD 2 (per standard protocol) and the occlusive dressing could remain in place for up to 7 days, there was a selection bias in the evaluation of the number of dressing changes. However, given the characteristics of the standard dressing (eg, tape, gauze, nonocclusive), leaving it in place after POD 2 is not optimal. Therefore, we would expect to see a difference in the number of dressing changes. We think this comparison remains valid, as occlusive dressings were changed when there were indications of wound problems (eg, excessive drainage [strike-through], surrounding erythema, blistering). With an average of less than 1 dressing change in the occlusive group, we think this is a surrogate for uneventful wound healing and decreased wound complication, and our data support this. It is also important to test both dressing durability and patient tolerance for wearing a single dressing for 7 days.

Our RCT results showed that, compared with a standard dressing, an occlusive antimicrobial dressing was associated with a significant decrease in overall wound complications and blisters. These findings are similar to those of other studies of occlusive dressings in a number of surgical subspecialties.^16,18 In an RCT of 200 patients who underwent elective and nonelective hip and knee surgery and were randomized to either absorbent perforated dressing with adhesive border (Cutiplast, Smith & Nephew) or Aquacel (ConvaTec) covered with vapor-permeable dressing (Tegaderm, 3M), Ravenscroft and colleagues²⁰ found that Aquacel-plus-Tegaderm was 5.8 times more likely than Cutiplast to produce an uncompromised wound. Similarly, in an RCT of hydrofiber (Aquacel) and central pad (Mepore, Mölnlycke) dressings after primary THA and TKA, Abuzakuk and colleagues¹⁹ found significantly fewer dressing changes (43% vs 77%) and blisters (13% vs 26%) in the hydrofiber group than in the pad group.

Hopper and colleagues²⁴ compared 50 consecutive patients treated with modern dressings (Aquacel) with 50 historical control patients treated with traditional surgical dressings (Mepore). Blisters developed in 20% of the patients in the traditional group and 4% of patients in the modern group (P = .028). The authors concluded that adverse outcomes of wound healing can be minimized with modern dressings.

A recent retrospective study by Cai and colleagues²⁵ evaluated the incidence of acute periprosthetic infection (≤3 months after surgery) with use of occlusive (Aquacel) and standard dressings. Incidence of acute periprosthetic infection was 0.44% in the occlusive group and 1.7% in the standard group (P = .005). Incidence of wound-healing problems was not evaluated.

Our second aim in the present study was to evaluate the number of dressing changes required. There were significantly fewer dressing changes in the occlusive dressing group than in the standard dressing group. Therefore, wear time (amount of time a single dressing remains in place) was substantially longer for the occlusive group. In the study by Hopper and colleagues,²⁴ wear time was significantly shorter for the traditional dressing than for the modern dressing (2 vs 7 days; P < .001), and the traditional dressing required more changes (3 vs 0; P < .001).

These findings are important for several reasons. Standard surgical dressings often require frequent changes. If left in place, they create an excessively moist wound environment that promotes blistering and delays wound healing. However, frequent dressing changes expose the wound and increase the risk for surgical site infection.²⁶ A barrier dressing left in place from time of surgery prevents bacteria from entering and contaminating a healing wound. A study by Clarke and colleagues²¹ demonstrated higher skin colonization rates for patients who had dressings changed on POD 1 than for patients who had their first dressing change on POD 6.

Our third study aim was to evaluate patient satisfaction with surgical dressings. The orthopedic literature has little on this topic.²³ Blisters and other wound complications can negatively affect satisfaction.^2,3 Our data showed significant improvement in satisfaction, particularly regarding sterility and hygiene.

Other surgical subspecialties have found similar improvement in patient satisfaction with occlusive barrier dressings. In an RCT of 88 pediatric patients, Rasmussen and colleagues²⁷ found that patients reported significantly less pain during changes of an occlusive adhesive dressing (Duoderm, ConvaTec) than during changes of a conventional Steristrip (3M) plus Cutiplast. According to the authors, the occlusive wound dressing seemed to minimize the physical and psychological trauma to the infant or child and lessen disruption of the child’s and the parents’ daily routines, because the children could be bathed immediately after surgery.

Our study did not specifically address cost. Cai and colleagues²⁵ estimated that, if the Aquacel dressing were routinely used in every hip and knee arthroplasty, it would add about $27 million in cost. However, this must be balanced by the cost of managing infection after TJA. In the United States, at an estimated $50,000 to $100,000 per case and an annual incidence of 1% to 2%, the low-end cost for the treatment of periprosthetic infection would be $500 million.²⁸ Cai and colleagues²⁵ found a 4-fold reduction in periprosthetic infection when use of occlusive dressings was implemented. In addition, wound complications remain the number one reason for hospital readmission after TJA.^12,13 Cost of hospital readmission, as well as financial penalties to institutions for unplanned readmission for wound complications, must be considered.

Conclusion

Our RCT results demonstrated that use of occlusive antimicrobial barrier dressings (vs standard surgical dressings) significantly reduced wound complications and dressing changes and improved overall patient satisfaction. These findings are similar to those in the literature on TJA and other surgical subspecialties. We conclude that occlusive surgical dressings reduce wound complications after TJA.

Wound complications (eg, delayed wound healing, blisters, prolonged drainage) have been reported in up to 30% of patients who undergo elective total joint arthroplasty (TJA).^1-6 Wound complications increase resource utilization, lengthen hospital stays, and increase costs.^7-9 Prolonged wound healing and persistent wound drainage are also harbingers of both superficial and deep surgical site infections.^5-11

In several studies, wound complications after TJA were the primary reason for hospital readmissions.^12-15 As part of the Patient Protection and Affordable Care Act, hospitals will be penalized by the Centers for Medicaid & Medicare Services for unplanned hospital readmissions within 30 days after TJA. It is imperative, then, to reduce the risk factors and complications associated with surgical site infections to decrease unplanned readmissions.

Historically, little attention has been given to the role of surgical dressings and the effect of dressings on wound healing. Although many subspecialties (eg, cardiothoracic surgery, general surgery) have reported benefits in using occlusive dressings, adoption in TJA has been slow.^16-18 At our institution about 5 years ago, we began using an occlusive silver-impregnated barrier dressing based on preliminary data from studies showing benefits of occlusive dressings in TJA.^19,20

We conducted a study to determine if use of occlusive antimicrobial barrier dressings decreases rates of wound complications in TJA. We had 3 research questions: Compared with standard surgical dressings, are occlusive dressings associated with decreased rates of wound complications after TJA? Is there a difference in number of dressing changes required between the 2 dressing types? Is satisfaction higher for patients with occlusive dressings than for patients with standard dressings?

Patients and Methods

This randomized controlled trial (RCT) was reviewed and approved by the Institutional Review Board at Carolinas Healthcare. Patients were randomized by the research staff using a parallel, 1:1 allocation method. The randomization table was generated using a random number generator.

An a priori sample size estimate was made using a 2-tailed Fisher exact test with a .05 level of significance. Based on a study by Clarke and colleagues,²¹ we estimated the incidence of wound problems at 3% in the occlusive dressing (study) group and 13% in the standard dressing (control) group. We determined that 260 participants (130 per group) would be needed to achieve 80% power. We considered a 15% attrition rate for a total enrollment goal of 300 study participants (150 per group).

Between December 2010 and January 2013, patients presenting for either primary total hip arthroplasty (THA) or primary total knee arthroplasty (TKA) were recruited to participate in the study. Eligibility criteria (Table 1) were reviewed, and patients were enrolled by the senior surgeons, Dr. Springer, Dr. Beaver, Dr. Griffin, and Dr. Mason. All eligible participants who provided informed consent were randomized to receive either an occlusive antimicrobial barrier dressing (Aquacel Ag, ConvaTec) or standard surgical dressing (Primapore, Smith & Nephew). The occlusive dressing (Figure 1) consists of an outer barrier layer of hydrocolloid and a central island of hydrofiber, which absorbs and locks in any wound exudate within the fibers and prevents the creation of an overly moist wound environment that can lead to skin maceration and wound breakdown. In addition, the hydrofibers are embedded with ionic silver, which is released only at the site of wound exudate, or drainage; thus, there is no continuous exposure of the entire wound to silver. The standard dressing (Figure 2) consists of a central island of gauze enclosed in low-allergy acrylic adhesive tape.

All surgical dressings were placed over a closed incision in a sterile environment in the operating room after the procedure. The groups’ wound closures were identical.

A posterior approach was used for all THAs. The deep fascia was closed with a running barbed suture (Quill, Angiotech), the deep subcutaneous tissue with No. 1 Vicryl suture (Ethicon), and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch (Ethicon) was placed in the subcuticular layer and was followed with a skin adhesive (Dermabond, Ethicon). A closed suction drain, removed on postoperative day (POD) 1, was used for all THAs.

A standard medial parapatellar arthrotomy was used for all TKAs. The arthrotomy was closed with a running barbed suture, the deep subcutaneous tissue with No. 1 Vicryl suture, and the superficial subcutaneous layer with 2-0 Vicryl suture. A running 3-0 Monocryl stitch was placed in the subcuticular layer and was followed with a skin adhesive. A closed suction drain was also used. In addition, a compressive wrap was placed over the dressing in the operating room and was removed the next morning. During the hospital stay, the surgical site was evaluated daily with a standard wound evaluation form.

 In the standard dressing group, the bandage was removed for wound evaluation on POD 2, and the dressing was changed every other day during the hospital stay. The dressing was also changed as needed for wound drainage (Figure 3) or other minor wound-healing concerns.

In the occlusive dressing group, the dressing design allowed the dressing to remain in place for about 7 days. It was removed by a home health nurse during a visit closest to but not before the 7-day mark. In addition, it was changed at surgeon discretion if there were concerns about wound drainage or wound healing. For the occlusive barrier, wound drainage was evaluated by strike-through of drainage on the back side of the dressing (Figure 4). If more than 50% of the dressing was saturated, the bandage was changed and the wound evaluated. If there were no immediate concerns about wound complications (eg, infection, blistering), a new occlusive dressing was placed. Because the occlusive dressing was waterproof, patients in the study group were able to shower immediately after surgery. In the control group, patients were allowed to shower if the surgical dressing was kept dry, as the bandage was not waterproof.

Per the study protocol, all patients were discharged home and followed by a single home health agency. Mean hospital stay was 3 days (range, 0-8 days), which did not differ significantly between groups (P = .133). All home health nurses were trained in evaluation of postsurgical wounds and were aware of the study requirements. The nurses visited all patients 3 days a week until the scheduled 4-week postoperative follow-up with the treating physician or physician assistant. At each visit, the nurse evaluated the wound and surrounding skin using a standard wound document. Dressings were changed based on the criteria we have described. Concerns about wound status (eg, drainage, blistering, erythema) prompted removal of the dressing for further evaluation. The physician was notified of concerns about wound healing, which prompted an office visit for evaluation. The dressing remained in place for a minimum of 7 days but in all cases was removed as close to 7 days as possible, depending on the scheduled nursing visits. Once uneventful wound healing was complete, no further dressing was required. A final wound evaluation was conducted by the surgeon at the 4-week postoperative evaluation.

The primary outcome measure was wound complication (dichotomous variable). Wounds were assessed by describing the amount, type, and color of exudate (Figure 5). The appearance of the wound margins and the surrounding skin was also assessed. Because wounds could not be directly visualized in the occlusive dressing group, drainage (indicated by strike-through) was used as a measure of possible wound complications, prompting removal and full evaluation.

 Secondary endpoints included additional wound treatment or surgical procedures for wound complications, number of dressing changes, and patient satisfaction. Patients completed a satisfaction questionnaire at each wound assessment (Figure 6). Using a visual analog scale (VAS), they rated their satisfaction with their ability to perform activities of daily living (personal hygiene, change clothes, sit comfortably, sleep comfortably), drawing a line on the VAS at a point between 0 (totally unsatisfied) and 100 (totally satisfied) for each satisfaction measure. This line was measured and recorded by the study coordinator. The 4 satisfaction measures were averaged for a composite satisfaction measure.

All statistical analyses were conducted using SAS Version 9.2 (SAS Institute). Standard univariate descriptive statistics (means, standard deviations, frequencies, proportions) were calculated and reported. Differences in mean values for continuous data were assessed with independent t test or Wilcoxon rank sum test. Chi-square test and Fisher exact test were used to determine differences between groups for categorical or dichotomous variables. A significance level of .05 was used for all statistical tests.

Results

The 300 patients who consented to participate in the study were randomized to receive either occlusive dressing or standard dressing. After randomization, 38 patients (15 occlusive, 23 standard) were withdrawn from the study (Table 2), leaving a final dataset of 262 patients, 141 in the occlusive group (67 THAs, 74 TKAs) and 121 in the standard group (49 THAs, 72 TKAs). There were no differences in proportion of THAs or TKAs, age, sex, or body mass index between the occlusive and standard groups (Table 3).

There were statistically significantly (P = .015) fewer wound complications in the occlusive dressing group (10%) than in the standard dressing group (22%). Blisters at or around the wound site were reported in significantly (P = .026) fewer patients with occlusive dressing (1/141, 0.7%) than standard dressing (7/121, 6%). Additional wound care was required in 9 patients (7%) in the standard group and 6 patients (4%) in the occlusive group (P = .27). Two patients (1.7%) in the standard group were readmitted for treatment of wound dehiscence; no one in the occlusive group was readmitted to the hospital or had to return to the operating room for treatment of a wound complication. The difference was not statistically significant (P = .13). There were also no significant (P = .81) differences in rate of wound complications between THA and TKA patients.

There were statistically significantly (P < .0001) fewer dressing changes in the occlusive dressing group. Mean number of dressing changes was 0.14 (median, 0; interquartile range, 0-0) in the occlusive group and 2.8 (median, 2; interquartile range, 1-3) in the standard group.

Compared with patients in the standard dressing group, patients in the occlusive dressing group reported significantly higher satisfaction scores. Mean overall patient satisfaction score was 92 in the occlusive group and 81 in the standard group (P < .0001). Patients in the occlusive group were more satisfied with their ability to take care of their personal hygiene, to change clothes, and to sit and sleep comfortably (Table 4).

Discussion

Wound complications after TJA are common, occurring in up to 30% of patients,^1-6 and are associated with development of superficial and deep surgical site infections, increased resource utilization, and longer hospital stays.^5-11 Although the role of surgical dressings has received little attention in TJA practice, other subspecialties have found that occlusive barrier dressings can reduce wound complications and promote wound healing.^16,17 Mitotic cell division and leukocyte activity, which are critical in wound healing, increase under occlusive dressings. This cellular activity is disrupted with every dressing change, delaying wound healing (biological activity takes 3-4 hours to resume).²² In addition, occlusive dressings increase hypoxia, which promotes angiogenesis and accelerates wound healing.²³

Despite being a prospective RCT, this study had several limitations. Because of the need to evaluate wounds and obvious differences between the 2 dressings (eg, color, ability to shower), it was not possible to blind the patient or surgeon to the dressing used. When rating satisfaction, patients were not able to directly compare the 2 dressings. The primary endpoint of the study was the complication rate; however, the deep periprosthetic infection rate may be a superior endpoint and would require a much larger study. Although we assumed that wound complications may be harbingers for periprosthetic infections, no patient in either group developed periprosthetic infection. Therefore, we cannot conclude that surgical dressings play a role in reducing infections. In addition, as the standard dressing was changed on POD 2 (per standard protocol) and the occlusive dressing could remain in place for up to 7 days, there was a selection bias in the evaluation of the number of dressing changes. However, given the characteristics of the standard dressing (eg, tape, gauze, nonocclusive), leaving it in place after POD 2 is not optimal. Therefore, we would expect to see a difference in the number of dressing changes. We think this comparison remains valid, as occlusive dressings were changed when there were indications of wound problems (eg, excessive drainage [strike-through], surrounding erythema, blistering). With an average of less than 1 dressing change in the occlusive group, we think this is a surrogate for uneventful wound healing and decreased wound complication, and our data support this. It is also important to test both dressing durability and patient tolerance for wearing a single dressing for 7 days.

Our RCT results showed that, compared with a standard dressing, an occlusive antimicrobial dressing was associated with a significant decrease in overall wound complications and blisters. These findings are similar to those of other studies of occlusive dressings in a number of surgical subspecialties.^16,18 In an RCT of 200 patients who underwent elective and nonelective hip and knee surgery and were randomized to either absorbent perforated dressing with adhesive border (Cutiplast, Smith & Nephew) or Aquacel (ConvaTec) covered with vapor-permeable dressing (Tegaderm, 3M), Ravenscroft and colleagues²⁰ found that Aquacel-plus-Tegaderm was 5.8 times more likely than Cutiplast to produce an uncompromised wound. Similarly, in an RCT of hydrofiber (Aquacel) and central pad (Mepore, Mölnlycke) dressings after primary THA and TKA, Abuzakuk and colleagues¹⁹ found significantly fewer dressing changes (43% vs 77%) and blisters (13% vs 26%) in the hydrofiber group than in the pad group.

Hopper and colleagues²⁴ compared 50 consecutive patients treated with modern dressings (Aquacel) with 50 historical control patients treated with traditional surgical dressings (Mepore). Blisters developed in 20% of the patients in the traditional group and 4% of patients in the modern group (P = .028). The authors concluded that adverse outcomes of wound healing can be minimized with modern dressings.

A recent retrospective study by Cai and colleagues²⁵ evaluated the incidence of acute periprosthetic infection (≤3 months after surgery) with use of occlusive (Aquacel) and standard dressings. Incidence of acute periprosthetic infection was 0.44% in the occlusive group and 1.7% in the standard group (P = .005). Incidence of wound-healing problems was not evaluated.

Our second aim in the present study was to evaluate the number of dressing changes required. There were significantly fewer dressing changes in the occlusive dressing group than in the standard dressing group. Therefore, wear time (amount of time a single dressing remains in place) was substantially longer for the occlusive group. In the study by Hopper and colleagues,²⁴ wear time was significantly shorter for the traditional dressing than for the modern dressing (2 vs 7 days; P < .001), and the traditional dressing required more changes (3 vs 0; P < .001).

These findings are important for several reasons. Standard surgical dressings often require frequent changes. If left in place, they create an excessively moist wound environment that promotes blistering and delays wound healing. However, frequent dressing changes expose the wound and increase the risk for surgical site infection.²⁶ A barrier dressing left in place from time of surgery prevents bacteria from entering and contaminating a healing wound. A study by Clarke and colleagues²¹ demonstrated higher skin colonization rates for patients who had dressings changed on POD 1 than for patients who had their first dressing change on POD 6.

Our third study aim was to evaluate patient satisfaction with surgical dressings. The orthopedic literature has little on this topic.²³ Blisters and other wound complications can negatively affect satisfaction.^2,3 Our data showed significant improvement in satisfaction, particularly regarding sterility and hygiene.

Other surgical subspecialties have found similar improvement in patient satisfaction with occlusive barrier dressings. In an RCT of 88 pediatric patients, Rasmussen and colleagues²⁷ found that patients reported significantly less pain during changes of an occlusive adhesive dressing (Duoderm, ConvaTec) than during changes of a conventional Steristrip (3M) plus Cutiplast. According to the authors, the occlusive wound dressing seemed to minimize the physical and psychological trauma to the infant or child and lessen disruption of the child’s and the parents’ daily routines, because the children could be bathed immediately after surgery.

Our study did not specifically address cost. Cai and colleagues²⁵ estimated that, if the Aquacel dressing were routinely used in every hip and knee arthroplasty, it would add about $27 million in cost. However, this must be balanced by the cost of managing infection after TJA. In the United States, at an estimated $50,000 to $100,000 per case and an annual incidence of 1% to 2%, the low-end cost for the treatment of periprosthetic infection would be $500 million.²⁸ Cai and colleagues²⁵ found a 4-fold reduction in periprosthetic infection when use of occlusive dressings was implemented. In addition, wound complications remain the number one reason for hospital readmission after TJA.^12,13 Cost of hospital readmission, as well as financial penalties to institutions for unplanned readmission for wound complications, must be considered.

Conclusion

Our RCT results demonstrated that use of occlusive antimicrobial barrier dressings (vs standard surgical dressings) significantly reduced wound complications and dressing changes and improved overall patient satisfaction. These findings are similar to those in the literature on TJA and other surgical subspecialties. We conclude that occlusive surgical dressings reduce wound complications after TJA.

Femoral stem modularity in total hip arthroplasty (THA) has a checkered past. Developments such as the modular head–trunnion interface, which allows for placement of femoral heads of different sizes and offsets, and the modular midstem, which allows for version adjustments independent of patient anatomy (S-ROM, Depuy) and for bypassing proximal bone defects in the revision setting (Restoration Modular, Stryker; ZMR-XL, Zimmer), have proved very successful.^1-10 However, even these successful advances have been associated with failures at the modular junction.^11-13 Proximal femoral neck–stem modularity (PFNSM) has had mixed results, with notable failures and recalls associated with the neck–stem junction.^14,15 Failures at this junction have occurred secondary to corrosion and breakage of the modular neck.^16-18 Nevertheless, proximal modular stems remain available for implantation. One such system, the M/L Taper stem with Kinectiv technology (Zimmer), is an all-titanium construct that allows for adjustment of several variables (length, offset, version), providing numerous combinations beyond those of the original M/L Taper offerings. Advantages of these offerings include closer reconstruction of patient anatomy, stability improvements, and easing of the process of revision in polyethylene/femoral head exchanges or in infections in which single-staged irrigation and débridement and polyethylene/head exchange are chosen.

These theoretic advantages must be judged in the context of the possible disadvantages of the modular neck junction. The mechanical environment of the junction places it at risk for failure as well as for metallosis from fretting, crevice corrosion, and recurrent repassivation.¹⁹ Although the titanium necks are at less risk for degradation than their cobalt-chromium counterparts, they are at higher risk for breakage.^13,19 For one of the surgeons in our practice, the M/L Taper stem with Kinectiv technology is the stem of choice for primary THA.

We conducted a study to determine, in the setting of primary THA, how often a neck–stem combination choice resulted in a reconstructive geometry that would not have been possible had the surgeon opted for the traditional M/L Taper stem. Every Kinectiv stem has numerous neck options with a head center position that would not be possible with the nonmodular M/L Taper. However, in a high-volume community practice, how often is a modular neck that results in an otherwise unavailable head center being used for the reconstruction?

Materials and Methods

This study was approved by our local institutional review board. The Kinectiv stem is used by 1 of the 4 high-volume joint replacement surgeons in our practice (not one of the authors). From our community practice joint registry, we identified every stem–neck combination used since the Kinectiv stem became available in 2006.²⁰ Each case was performed using a posterior approach. A trabecular metal acetabular component (Zimmer) secured with 2 screws was used, and an M/L Taper stem with Kinectiv technology was implanted in each case.

Once the neck–stem combination was determined, its position on the head centers map was compared with that of the standard M/L Taper head centers (Figures 1, 2) for each stem size as the relationship of the Kinectiv head center varies with each stem size compared with the head center of the M/L Taper stems. If the head centers were in contact on the map, the geometry was considered identical. If the head centers were not in contact, we noted where the nearest standard M/L Taper head center lay in terms of length and offset. As the head centers are laid out in regular, 4-mm increments, this estimation was relatively easy. Any anteverted or retroverted neck was considered to have no adequate substitution in the standard M/L Taper stem offerings. This initial evaluation was performed by Dr. Carothers.

We then reviewed the head center comparisons independently. For every Kinectiv head center that did not contact an M/L Taper counterpart, the difference between those head centers was reviewed. Each of us noted whether the difference between the head centers was clinically relevant, as many of the head center positions are extremely close. The head centers that were so close as to be deemed clinically irrelevant were recorded.

Results

Between January 2008 and October 2013, 463 primary THAs were performed using the M/L Taper femoral stem with Kinectiv technology. Of the neck options used, 205 (44%) had a head center identical to that of a nonmodular M/L Taper stem. In another 56 cases (12%), all 3 reviewing surgeons agreed that the M/L Taper head center was so close to the Kinectiv head center as to be clinically indistinguishable. Of these 56 cases, 54 had a head center difference of less than 1 mm in length or offset; the other 2 had a 2-mm difference in offset.

Thus, a total of 261 stems (56%) had a standard M/L Taper option that offered an identical head center or one so close as to be clinically indistinguishable. Interestingly, in the group of 202 stems that did not have an identical head center and were not clinically indistinguishable, 132 (65%) of these modular stems were within 4 mm in length and 2 mm of offset of the closest Kinectiv head center. A verted neck was used in 12 cases (11 anteverted, 1 retroverted).

Nine of the 463 cases required revision surgery, 3 for recurrent instability. In 1 of these 3 cases, the acetabulum was revised for malposition, and the neck was converted from standard offset, +0 mm length (head center identical to nonmodular stem), to extended offset, +4 mm length (2 mm shorter with 1 mm less offset than closest nonmodular head center). The second case had complete deficiency of the abductor tendons and was converted to a constrained liner, though at the time of the THA a head center identical to that of the nonmodular stem was used. The third case was revised to convert a standard offset, +0 mm length, straight neck (head center identical to nonmodular stem), to extended offset, +4 mm length, anteverted neck (anteversion making this a unique head center position). Of the other 6 cases, 1 was treated for corrosion at the head–neck junction by changing the head from cobalt-chromium to ceramic (the junction was noted to be pristine), 1 underwent revision of the acetabular component for loosening, 2 femoral stems were revised for periprosthetic femur fracture, and 2 cases underwent 2-stage revision for late infection. There were no failures secondary to metallosis at the neck–stem junction and no modular breakages. The 3 cases of recurrent instability had no dislocation episodes after revision.

Discussion

PFNSM was developed to help more closely reconstruct patient anatomy. PFNSM allows for individualization of offset, length, and version—and thus for optimization of component interaction to avoid impingement and dislocation while promoting range of motion and normal gait.²¹ These benefits must be judged in light of the disadvantages of proximal stem modularity, including corrosion and breakage of the modular neck.^14-18

In the present study, conducted in a high-volume private practice setting, 44% of necks used in a proximally modular construct had a head center identical to that of a nonmodular alternative. In the opinion of the 3 authors (high-volume hip surgeons), an additional 12% of the modular stems had a head center so close to that of the nonmodular stem as to be clinically indistinguishable. In addition, 132 of the modular necks had a femoral head center within 4 mm in length and 2 mm of offset of the nonmodular stem. These findings call into question the theoretical benefits of regular use of this modular femoral stem for primary THA. Certainly there are extreme femoral neck–shaft angle cases in which the standard nonmodular stem may be inadequate and this proximal modularity would be helpful, but our study showed such cases are relatively less frequent. We caution against routine use of this proximal modularity in primary THA and suggest restricting it to cases in which the standard stem offerings are unacceptable. These findings are not surprising given that the standard M/L Taper stem is based on a historically successful model with neck angle and length options designed to meet the goals of restoring length, offset, range of motion, and stability. We would expect that a well-designed stem will meet these goals in the majority of cases.

Of our 463 cases with the modular neck, 9 required revision surgery. Of these 9 revisions, 2 were for recurrent dislocation in which the modular neck was revised to one that enhanced stability, and there were no further dislocations. The ability to change the geometry of the proximal femur resulted in a stability solution that avoided revision of the entire femoral component, as might otherwise be required. One case of acetabular loosening and 1 case that required placement of a constrained liner were potentially benefited by the modular neck in that the surgeries may have been expedited by being able to remove the neck to ease exposure for placement of the acetabular components. The other 5 revisions—2 for periprosthetic femur fracture, 2 two-stage revisions for infection, and 1 femoral head exchange for metallosis at the head–neck junction—saw no benefit from the modularity in the revision setting.

This study had several limitations. First, as it was primarily an evaluation of use of a modular femoral system, there was no attempt to account for the fact that acetabular component orientation can affect stability and, thus, the perceived need for additional offset or changes in version. The habit of all 3 of the reviewing surgeons is to consider the position of the acetabular component and to reposition the component, if necessary, to achieve appropriate stability. Therefore, the need for the modularity may be even less than suggested by this study. In addition, the idea that (in 12 cases) no standard stem option would be acceptable because of the use of a verted neck ignores the possibility that cup repositioning could have obviated the need for additional version. Furthermore, use of a 36-mm head results in an additional 3.5 mm of offset in the polyethylene liner, and this study did not account for the option of increasing head size—and for the potential increase in stability from a larger head and the increased offset gained from the liner.

A second limitation is that a significant number of Kinectiv stems (132) had a head center within 4 mm in length and 2 mm of offset of the nearest M/L Taper stem. We carefully template every primary THA to determine the plan that will optimize component size and position and restore length and offset. More options for achieving these goals are available when templating with the intention of using the Kinectiv modular neck. The neck cut and position of the stem proximally or distally in the proximal femur may not need to be so exact, as the additional options may be able to accommodate minor inaccuracies. Thus, the reported percentage of clinically indistinguishable head centers (12%) may underestimate the actual number of modular stems that could have been replaced with a nonmodular stem.

Third, this study did not evaluate the effect of the modular junction on ease of irrigation and débridement with head/neck and polyethylene exchange in cases of infection, or on ease of head/neck and polyethylene exchange for revision. In addition, the study did not evaluate other cases of instability involving a nonmodular stem that otherwise could have been solved with simple revision of the head/neck combination, avoiding revision of the entire stem and/or the acetabular component. We reported revisions for infection and for instability, but comprehensive assessment and comparison were beyond the scope of this study. Certainly ease of revision of the head and neck is a factor that could favor use of the modularity.

Fourth, this was not a clinical outcome study comparing 2 different femoral stems. We sought only to determine how often a modular neck was chosen that resulted in a head center that would have been unavailable to the non-modular stem suggesting that the patient was receiving a reconstructive benefit in exchange for the modularity. However, 2 recent reports have noted no clinical benefit at 2-year follow-up with use of the modular neck compared with the nonmodular stem.^22,23

Though the M/L Taper with Kinectiv technology has, thus far, performed well, PFNSM should be used with caution in light of recently reported failures at the neck–stem junction.14,16-18 Our study results suggest that most (≥56%) of the modular stems used could have been reconstructed as acceptably with a nonmodular stem, and therefore a reconstructive benefit was not realized in trade for the potential risks of proximal modularity. Only 2 of the 9 revision cases saw a clear advantage in being able to change the modular neck geometry in the revision setting. Given the recently reported failures and the high-profile recall of a modular stem,14 we recommend restricting the modular stem to cases that cannot be adequately reconstructed with the nonmodular option.

Femoral stem modularity in total hip arthroplasty (THA) has a checkered past. Developments such as the modular head–trunnion interface, which allows for placement of femoral heads of different sizes and offsets, and the modular midstem, which allows for version adjustments independent of patient anatomy (S-ROM, Depuy) and for bypassing proximal bone defects in the revision setting (Restoration Modular, Stryker; ZMR-XL, Zimmer), have proved very successful.^1-10 However, even these successful advances have been associated with failures at the modular junction.^11-13 Proximal femoral neck–stem modularity (PFNSM) has had mixed results, with notable failures and recalls associated with the neck–stem junction.^14,15 Failures at this junction have occurred secondary to corrosion and breakage of the modular neck.^16-18 Nevertheless, proximal modular stems remain available for implantation. One such system, the M/L Taper stem with Kinectiv technology (Zimmer), is an all-titanium construct that allows for adjustment of several variables (length, offset, version), providing numerous combinations beyond those of the original M/L Taper offerings. Advantages of these offerings include closer reconstruction of patient anatomy, stability improvements, and easing of the process of revision in polyethylene/femoral head exchanges or in infections in which single-staged irrigation and débridement and polyethylene/head exchange are chosen.

These theoretic advantages must be judged in the context of the possible disadvantages of the modular neck junction. The mechanical environment of the junction places it at risk for failure as well as for metallosis from fretting, crevice corrosion, and recurrent repassivation.¹⁹ Although the titanium necks are at less risk for degradation than their cobalt-chromium counterparts, they are at higher risk for breakage.^13,19 For one of the surgeons in our practice, the M/L Taper stem with Kinectiv technology is the stem of choice for primary THA.

We conducted a study to determine, in the setting of primary THA, how often a neck–stem combination choice resulted in a reconstructive geometry that would not have been possible had the surgeon opted for the traditional M/L Taper stem. Every Kinectiv stem has numerous neck options with a head center position that would not be possible with the nonmodular M/L Taper. However, in a high-volume community practice, how often is a modular neck that results in an otherwise unavailable head center being used for the reconstruction?

Materials and Methods

This study was approved by our local institutional review board. The Kinectiv stem is used by 1 of the 4 high-volume joint replacement surgeons in our practice (not one of the authors). From our community practice joint registry, we identified every stem–neck combination used since the Kinectiv stem became available in 2006.²⁰ Each case was performed using a posterior approach. A trabecular metal acetabular component (Zimmer) secured with 2 screws was used, and an M/L Taper stem with Kinectiv technology was implanted in each case.

Once the neck–stem combination was determined, its position on the head centers map was compared with that of the standard M/L Taper head centers (Figures 1, 2) for each stem size as the relationship of the Kinectiv head center varies with each stem size compared with the head center of the M/L Taper stems. If the head centers were in contact on the map, the geometry was considered identical. If the head centers were not in contact, we noted where the nearest standard M/L Taper head center lay in terms of length and offset. As the head centers are laid out in regular, 4-mm increments, this estimation was relatively easy. Any anteverted or retroverted neck was considered to have no adequate substitution in the standard M/L Taper stem offerings. This initial evaluation was performed by Dr. Carothers.

We then reviewed the head center comparisons independently. For every Kinectiv head center that did not contact an M/L Taper counterpart, the difference between those head centers was reviewed. Each of us noted whether the difference between the head centers was clinically relevant, as many of the head center positions are extremely close. The head centers that were so close as to be deemed clinically irrelevant were recorded.

Results

Between January 2008 and October 2013, 463 primary THAs were performed using the M/L Taper femoral stem with Kinectiv technology. Of the neck options used, 205 (44%) had a head center identical to that of a nonmodular M/L Taper stem. In another 56 cases (12%), all 3 reviewing surgeons agreed that the M/L Taper head center was so close to the Kinectiv head center as to be clinically indistinguishable. Of these 56 cases, 54 had a head center difference of less than 1 mm in length or offset; the other 2 had a 2-mm difference in offset.

Thus, a total of 261 stems (56%) had a standard M/L Taper option that offered an identical head center or one so close as to be clinically indistinguishable. Interestingly, in the group of 202 stems that did not have an identical head center and were not clinically indistinguishable, 132 (65%) of these modular stems were within 4 mm in length and 2 mm of offset of the closest Kinectiv head center. A verted neck was used in 12 cases (11 anteverted, 1 retroverted).

Nine of the 463 cases required revision surgery, 3 for recurrent instability. In 1 of these 3 cases, the acetabulum was revised for malposition, and the neck was converted from standard offset, +0 mm length (head center identical to nonmodular stem), to extended offset, +4 mm length (2 mm shorter with 1 mm less offset than closest nonmodular head center). The second case had complete deficiency of the abductor tendons and was converted to a constrained liner, though at the time of the THA a head center identical to that of the nonmodular stem was used. The third case was revised to convert a standard offset, +0 mm length, straight neck (head center identical to nonmodular stem), to extended offset, +4 mm length, anteverted neck (anteversion making this a unique head center position). Of the other 6 cases, 1 was treated for corrosion at the head–neck junction by changing the head from cobalt-chromium to ceramic (the junction was noted to be pristine), 1 underwent revision of the acetabular component for loosening, 2 femoral stems were revised for periprosthetic femur fracture, and 2 cases underwent 2-stage revision for late infection. There were no failures secondary to metallosis at the neck–stem junction and no modular breakages. The 3 cases of recurrent instability had no dislocation episodes after revision.

Discussion

PFNSM was developed to help more closely reconstruct patient anatomy. PFNSM allows for individualization of offset, length, and version—and thus for optimization of component interaction to avoid impingement and dislocation while promoting range of motion and normal gait.²¹ These benefits must be judged in light of the disadvantages of proximal stem modularity, including corrosion and breakage of the modular neck.^14-18

In the present study, conducted in a high-volume private practice setting, 44% of necks used in a proximally modular construct had a head center identical to that of a nonmodular alternative. In the opinion of the 3 authors (high-volume hip surgeons), an additional 12% of the modular stems had a head center so close to that of the nonmodular stem as to be clinically indistinguishable. In addition, 132 of the modular necks had a femoral head center within 4 mm in length and 2 mm of offset of the nonmodular stem. These findings call into question the theoretical benefits of regular use of this modular femoral stem for primary THA. Certainly there are extreme femoral neck–shaft angle cases in which the standard nonmodular stem may be inadequate and this proximal modularity would be helpful, but our study showed such cases are relatively less frequent. We caution against routine use of this proximal modularity in primary THA and suggest restricting it to cases in which the standard stem offerings are unacceptable. These findings are not surprising given that the standard M/L Taper stem is based on a historically successful model with neck angle and length options designed to meet the goals of restoring length, offset, range of motion, and stability. We would expect that a well-designed stem will meet these goals in the majority of cases.

Of our 463 cases with the modular neck, 9 required revision surgery. Of these 9 revisions, 2 were for recurrent dislocation in which the modular neck was revised to one that enhanced stability, and there were no further dislocations. The ability to change the geometry of the proximal femur resulted in a stability solution that avoided revision of the entire femoral component, as might otherwise be required. One case of acetabular loosening and 1 case that required placement of a constrained liner were potentially benefited by the modular neck in that the surgeries may have been expedited by being able to remove the neck to ease exposure for placement of the acetabular components. The other 5 revisions—2 for periprosthetic femur fracture, 2 two-stage revisions for infection, and 1 femoral head exchange for metallosis at the head–neck junction—saw no benefit from the modularity in the revision setting.

This study had several limitations. First, as it was primarily an evaluation of use of a modular femoral system, there was no attempt to account for the fact that acetabular component orientation can affect stability and, thus, the perceived need for additional offset or changes in version. The habit of all 3 of the reviewing surgeons is to consider the position of the acetabular component and to reposition the component, if necessary, to achieve appropriate stability. Therefore, the need for the modularity may be even less than suggested by this study. In addition, the idea that (in 12 cases) no standard stem option would be acceptable because of the use of a verted neck ignores the possibility that cup repositioning could have obviated the need for additional version. Furthermore, use of a 36-mm head results in an additional 3.5 mm of offset in the polyethylene liner, and this study did not account for the option of increasing head size—and for the potential increase in stability from a larger head and the increased offset gained from the liner.

A second limitation is that a significant number of Kinectiv stems (132) had a head center within 4 mm in length and 2 mm of offset of the nearest M/L Taper stem. We carefully template every primary THA to determine the plan that will optimize component size and position and restore length and offset. More options for achieving these goals are available when templating with the intention of using the Kinectiv modular neck. The neck cut and position of the stem proximally or distally in the proximal femur may not need to be so exact, as the additional options may be able to accommodate minor inaccuracies. Thus, the reported percentage of clinically indistinguishable head centers (12%) may underestimate the actual number of modular stems that could have been replaced with a nonmodular stem.

Third, this study did not evaluate the effect of the modular junction on ease of irrigation and débridement with head/neck and polyethylene exchange in cases of infection, or on ease of head/neck and polyethylene exchange for revision. In addition, the study did not evaluate other cases of instability involving a nonmodular stem that otherwise could have been solved with simple revision of the head/neck combination, avoiding revision of the entire stem and/or the acetabular component. We reported revisions for infection and for instability, but comprehensive assessment and comparison were beyond the scope of this study. Certainly ease of revision of the head and neck is a factor that could favor use of the modularity.

Fourth, this was not a clinical outcome study comparing 2 different femoral stems. We sought only to determine how often a modular neck was chosen that resulted in a head center that would have been unavailable to the non-modular stem suggesting that the patient was receiving a reconstructive benefit in exchange for the modularity. However, 2 recent reports have noted no clinical benefit at 2-year follow-up with use of the modular neck compared with the nonmodular stem.^22,23

Though the M/L Taper with Kinectiv technology has, thus far, performed well, PFNSM should be used with caution in light of recently reported failures at the neck–stem junction.14,16-18 Our study results suggest that most (≥56%) of the modular stems used could have been reconstructed as acceptably with a nonmodular stem, and therefore a reconstructive benefit was not realized in trade for the potential risks of proximal modularity. Only 2 of the 9 revision cases saw a clear advantage in being able to change the modular neck geometry in the revision setting. Given the recently reported failures and the high-profile recall of a modular stem,14 we recommend restricting the modular stem to cases that cannot be adequately reconstructed with the nonmodular option.

Femoral stem modularity in total hip arthroplasty (THA) has a checkered past. Developments such as the modular head–trunnion interface, which allows for placement of femoral heads of different sizes and offsets, and the modular midstem, which allows for version adjustments independent of patient anatomy (S-ROM, Depuy) and for bypassing proximal bone defects in the revision setting (Restoration Modular, Stryker; ZMR-XL, Zimmer), have proved very successful.^1-10 However, even these successful advances have been associated with failures at the modular junction.^11-13 Proximal femoral neck–stem modularity (PFNSM) has had mixed results, with notable failures and recalls associated with the neck–stem junction.^14,15 Failures at this junction have occurred secondary to corrosion and breakage of the modular neck.^16-18 Nevertheless, proximal modular stems remain available for implantation. One such system, the M/L Taper stem with Kinectiv technology (Zimmer), is an all-titanium construct that allows for adjustment of several variables (length, offset, version), providing numerous combinations beyond those of the original M/L Taper offerings. Advantages of these offerings include closer reconstruction of patient anatomy, stability improvements, and easing of the process of revision in polyethylene/femoral head exchanges or in infections in which single-staged irrigation and débridement and polyethylene/head exchange are chosen.

These theoretic advantages must be judged in the context of the possible disadvantages of the modular neck junction. The mechanical environment of the junction places it at risk for failure as well as for metallosis from fretting, crevice corrosion, and recurrent repassivation.¹⁹ Although the titanium necks are at less risk for degradation than their cobalt-chromium counterparts, they are at higher risk for breakage.^13,19 For one of the surgeons in our practice, the M/L Taper stem with Kinectiv technology is the stem of choice for primary THA.

We conducted a study to determine, in the setting of primary THA, how often a neck–stem combination choice resulted in a reconstructive geometry that would not have been possible had the surgeon opted for the traditional M/L Taper stem. Every Kinectiv stem has numerous neck options with a head center position that would not be possible with the nonmodular M/L Taper. However, in a high-volume community practice, how often is a modular neck that results in an otherwise unavailable head center being used for the reconstruction?

Materials and Methods

This study was approved by our local institutional review board. The Kinectiv stem is used by 1 of the 4 high-volume joint replacement surgeons in our practice (not one of the authors). From our community practice joint registry, we identified every stem–neck combination used since the Kinectiv stem became available in 2006.²⁰ Each case was performed using a posterior approach. A trabecular metal acetabular component (Zimmer) secured with 2 screws was used, and an M/L Taper stem with Kinectiv technology was implanted in each case.

Once the neck–stem combination was determined, its position on the head centers map was compared with that of the standard M/L Taper head centers (Figures 1, 2) for each stem size as the relationship of the Kinectiv head center varies with each stem size compared with the head center of the M/L Taper stems. If the head centers were in contact on the map, the geometry was considered identical. If the head centers were not in contact, we noted where the nearest standard M/L Taper head center lay in terms of length and offset. As the head centers are laid out in regular, 4-mm increments, this estimation was relatively easy. Any anteverted or retroverted neck was considered to have no adequate substitution in the standard M/L Taper stem offerings. This initial evaluation was performed by Dr. Carothers.

We then reviewed the head center comparisons independently. For every Kinectiv head center that did not contact an M/L Taper counterpart, the difference between those head centers was reviewed. Each of us noted whether the difference between the head centers was clinically relevant, as many of the head center positions are extremely close. The head centers that were so close as to be deemed clinically irrelevant were recorded.

Results

Between January 2008 and October 2013, 463 primary THAs were performed using the M/L Taper femoral stem with Kinectiv technology. Of the neck options used, 205 (44%) had a head center identical to that of a nonmodular M/L Taper stem. In another 56 cases (12%), all 3 reviewing surgeons agreed that the M/L Taper head center was so close to the Kinectiv head center as to be clinically indistinguishable. Of these 56 cases, 54 had a head center difference of less than 1 mm in length or offset; the other 2 had a 2-mm difference in offset.

Thus, a total of 261 stems (56%) had a standard M/L Taper option that offered an identical head center or one so close as to be clinically indistinguishable. Interestingly, in the group of 202 stems that did not have an identical head center and were not clinically indistinguishable, 132 (65%) of these modular stems were within 4 mm in length and 2 mm of offset of the closest Kinectiv head center. A verted neck was used in 12 cases (11 anteverted, 1 retroverted).

Nine of the 463 cases required revision surgery, 3 for recurrent instability. In 1 of these 3 cases, the acetabulum was revised for malposition, and the neck was converted from standard offset, +0 mm length (head center identical to nonmodular stem), to extended offset, +4 mm length (2 mm shorter with 1 mm less offset than closest nonmodular head center). The second case had complete deficiency of the abductor tendons and was converted to a constrained liner, though at the time of the THA a head center identical to that of the nonmodular stem was used. The third case was revised to convert a standard offset, +0 mm length, straight neck (head center identical to nonmodular stem), to extended offset, +4 mm length, anteverted neck (anteversion making this a unique head center position). Of the other 6 cases, 1 was treated for corrosion at the head–neck junction by changing the head from cobalt-chromium to ceramic (the junction was noted to be pristine), 1 underwent revision of the acetabular component for loosening, 2 femoral stems were revised for periprosthetic femur fracture, and 2 cases underwent 2-stage revision for late infection. There were no failures secondary to metallosis at the neck–stem junction and no modular breakages. The 3 cases of recurrent instability had no dislocation episodes after revision.

Discussion

PFNSM was developed to help more closely reconstruct patient anatomy. PFNSM allows for individualization of offset, length, and version—and thus for optimization of component interaction to avoid impingement and dislocation while promoting range of motion and normal gait.²¹ These benefits must be judged in light of the disadvantages of proximal stem modularity, including corrosion and breakage of the modular neck.^14-18

In the present study, conducted in a high-volume private practice setting, 44% of necks used in a proximally modular construct had a head center identical to that of a nonmodular alternative. In the opinion of the 3 authors (high-volume hip surgeons), an additional 12% of the modular stems had a head center so close to that of the nonmodular stem as to be clinically indistinguishable. In addition, 132 of the modular necks had a femoral head center within 4 mm in length and 2 mm of offset of the nonmodular stem. These findings call into question the theoretical benefits of regular use of this modular femoral stem for primary THA. Certainly there are extreme femoral neck–shaft angle cases in which the standard nonmodular stem may be inadequate and this proximal modularity would be helpful, but our study showed such cases are relatively less frequent. We caution against routine use of this proximal modularity in primary THA and suggest restricting it to cases in which the standard stem offerings are unacceptable. These findings are not surprising given that the standard M/L Taper stem is based on a historically successful model with neck angle and length options designed to meet the goals of restoring length, offset, range of motion, and stability. We would expect that a well-designed stem will meet these goals in the majority of cases.

Of our 463 cases with the modular neck, 9 required revision surgery. Of these 9 revisions, 2 were for recurrent dislocation in which the modular neck was revised to one that enhanced stability, and there were no further dislocations. The ability to change the geometry of the proximal femur resulted in a stability solution that avoided revision of the entire femoral component, as might otherwise be required. One case of acetabular loosening and 1 case that required placement of a constrained liner were potentially benefited by the modular neck in that the surgeries may have been expedited by being able to remove the neck to ease exposure for placement of the acetabular components. The other 5 revisions—2 for periprosthetic femur fracture, 2 two-stage revisions for infection, and 1 femoral head exchange for metallosis at the head–neck junction—saw no benefit from the modularity in the revision setting.

This study had several limitations. First, as it was primarily an evaluation of use of a modular femoral system, there was no attempt to account for the fact that acetabular component orientation can affect stability and, thus, the perceived need for additional offset or changes in version. The habit of all 3 of the reviewing surgeons is to consider the position of the acetabular component and to reposition the component, if necessary, to achieve appropriate stability. Therefore, the need for the modularity may be even less than suggested by this study. In addition, the idea that (in 12 cases) no standard stem option would be acceptable because of the use of a verted neck ignores the possibility that cup repositioning could have obviated the need for additional version. Furthermore, use of a 36-mm head results in an additional 3.5 mm of offset in the polyethylene liner, and this study did not account for the option of increasing head size—and for the potential increase in stability from a larger head and the increased offset gained from the liner.

A second limitation is that a significant number of Kinectiv stems (132) had a head center within 4 mm in length and 2 mm of offset of the nearest M/L Taper stem. We carefully template every primary THA to determine the plan that will optimize component size and position and restore length and offset. More options for achieving these goals are available when templating with the intention of using the Kinectiv modular neck. The neck cut and position of the stem proximally or distally in the proximal femur may not need to be so exact, as the additional options may be able to accommodate minor inaccuracies. Thus, the reported percentage of clinically indistinguishable head centers (12%) may underestimate the actual number of modular stems that could have been replaced with a nonmodular stem.

Third, this study did not evaluate the effect of the modular junction on ease of irrigation and débridement with head/neck and polyethylene exchange in cases of infection, or on ease of head/neck and polyethylene exchange for revision. In addition, the study did not evaluate other cases of instability involving a nonmodular stem that otherwise could have been solved with simple revision of the head/neck combination, avoiding revision of the entire stem and/or the acetabular component. We reported revisions for infection and for instability, but comprehensive assessment and comparison were beyond the scope of this study. Certainly ease of revision of the head and neck is a factor that could favor use of the modularity.

Fourth, this was not a clinical outcome study comparing 2 different femoral stems. We sought only to determine how often a modular neck was chosen that resulted in a head center that would have been unavailable to the non-modular stem suggesting that the patient was receiving a reconstructive benefit in exchange for the modularity. However, 2 recent reports have noted no clinical benefit at 2-year follow-up with use of the modular neck compared with the nonmodular stem.^22,23

Though the M/L Taper with Kinectiv technology has, thus far, performed well, PFNSM should be used with caution in light of recently reported failures at the neck–stem junction.14,16-18 Our study results suggest that most (≥56%) of the modular stems used could have been reconstructed as acceptably with a nonmodular stem, and therefore a reconstructive benefit was not realized in trade for the potential risks of proximal modularity. Only 2 of the 9 revision cases saw a clear advantage in being able to change the modular neck geometry in the revision setting. Given the recently reported failures and the high-profile recall of a modular stem,14 we recommend restricting the modular stem to cases that cannot be adequately reconstructed with the nonmodular option.

Total hip arthroplasty (THA) is an excellent option for the treatment of osteoarthritis of the hip. In numerous studies, modern implants have shown survivorship of more than 90% at 10 years.^1,2 Polyethylene wear and subsequent osteolysis are major obstacles to the long-term success of THA.^3-5 Polyethylene wear particles are phagocytized by macrophages, inducing an inflammatory response that can ultimately lead to osteolysis of the bony architecture surrounding the bone–implant interface.^6,7 As modern implants often rely on direct implant-to-bone ingrowth to maintain fixation, wear at this junction can lead to aseptic component loosening and ultimately require revision surgery.^8-10 Osteolysis can be diagnosed with plain radiography or computed tomography (CT).¹¹ CT is more sensitive than plain radiography for the diagnosis of osteolysis and is better able to determine the size and location of osteolytic lesions.^12,13

Although diagnosis of osteolysis is well defined in the literature, what is more challenging is radiographic diagnosis of a loose acetabular component.¹¹ The most commonly described criteria for loosening are presence of a complete radiolucent line of more than 2 mm in width at the bone–implant interface and any progressive tilting or migration of the component.^14,15 CT-based criteria for component loosening remain largely undefined, though Egawa and colleagues¹⁶ showed that acetabular osteolysis involving less than 40% of the total cup surface is not associated with component loosening. Although a patient may show signs of osteolysis on postoperative imaging, this finding does not necessitate immediate revision surgery.¹⁷ Osteolysis may be monitored clinically and followed radiographically to determine when intervention is necessary.¹³

The goals of revision surgery are to eliminate the wear generator and bone-graft lytic lesions where needed to help maintain the bone–implant interface.¹⁷ The timing of such surgery is important, as the surgeon must balance the risk for gross component migration against the morbidity and mortality associated with acetabular component revision.¹⁸ This is in contrast to the settings of infection, periprosthetic fracture, recurrent instability, and component fracture/loosening, in which revision is urgently indicated and the case cannot be managed conservatively.

We conducted a study to determine the incidence of loose acetabular components without radiographic or clinical findings that would necessitate urgent revision THA. Radiographically silent loosening (RSL) was defined as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Although these patients make up a small minority of the revision population, knowing the incidence of RSL can help raise surgeon awareness of this potentially dangerous situation. We further sought to determine whether patients with RSL present with different demographic characteristics or clinical symptoms than patients with stable acetabular components.

Materials and Methods

In this retrospective, case–control, institutional review board–approved study, we evaluated patients who had undergone revision THA and had preoperative plain radiographs and CT images. We identified patients by International Classification of Diseases, Ninth Revision (ICD‑9) codes (00.70, 00.71, 00.72, 00.73, 80.05, 81.53, 84.56, 84.57) and searched for those cases treated between 2000 and 2012.

Inclusion criteria were confirmed revision THA and confirmed plain radiography and CT of the THA performed before revision. When osteolysis was diagnosed by plain radiography, CT was ordered to determine the extent of bony lesions or to evaluate for eccentric head position or component malposition. Last, all patients included in the study had a detailed operative report clearly indicating acetabular component stability at time of revision. Acetabular component stability at time of surgery was determined according to the criteria defined by Berger and colleagues.¹⁹ Cups were evaluated for gross motion during both hip dislocation and during edge loading of the component after thorough scar and capsular débridement.

Patients who did not have CT performed before revision surgery were excluded from the study. These patients had been diagnosed by clinical history and/or plain radiography. Cases revised for periprosthetic infection or periprosthetic fracture were also excluded. Patients with metal-on-metal bearings were excluded, as were any cases revised from hemiarthroplasty to THA, as well as cases revised for recurrent dislocations or component malposition.

All plain radiographs and CT images were evaluated by the orthopedic surgeon who performed the revision and by a radiologist. Images were inspected for signs of gross component migration, tilting, and concentric lucency of the bone–implant interface. Patients with imaging that showed signs of component movement or migration (as seen by the attending surgeon or the radiologist) were excluded. Patients with radiographic evidence of femoral stem loosening were also excluded, as they had an indication to undergo revision arthroplasty. The remaining patients were then stratified into 2 groups: those with stable acetabular components at time of revision and those with loose acetabular components. Stable acetabular shells showed no gross motion of the implant with dislocation, edge loading with an impactor, or pulling with a Kocher clamp after débridement and screw removal.^15,19 The 2 groups were then compared with respect to age, sex, and most common presenting symptoms and diagnoses. Fischer exact test and Student t test were used to statistically compare the groups.

Results

Overall, 393 patients underwent revision arthroplasty for the diagnoses (ICD-9 codes) indicated (Figure). One hundred eighty-nine patients (48.1%) had CT performed before revision. Of these 189 patients, 85 were excluded for diagnoses that were evident on either plain radiography or CT, that necessitated urgent revision, or for procedures beyond the scope of the study (Table 1). CT showed a loose cup in 28 patients; 6 of these cups were also seen on CT. Thirteen patients were diagnosed with a loose femoral stem, 10 with a periprosthetic infection, and 8 with a periprosthetic fracture.

One hundred four patients (54 men, 50 women) met the study inclusion criteria. Mean age was 65.1 years. Of these 104 patients, 87 (83.7%) had a stable acetabular shell at time of revision surgery; the other 17 (16.3%) were diagnosed with RSL of the acetabular shell. Osteolysis was the most common diagnosis (89.4%) in the overall population, and pain was the most common complaint at time of presentation (66.6%). Lack of symptoms was the second most common presentation at time of revision (19.2%) (Table 2). Patients without symptoms underwent revision surgery because of concern about impending compromise of the bone–implant interface and progressive osteolysis.

The 2 groups (stable vs unstable acetabular shells) were not significantly different with respect to age (P = .961) or sex distribution (P = .185). All patients in the RSL group were diagnosed with osteolysis radiographically, and 15 (88%) of 17 patients presented with pain as the primary complaint, compared with only 54 (62%) of 87 patients in the group with stable shells. Patients with RSL were significantly more likely to present with pain as the primary complaint (P = .0487). Nineteen patients in the stable implant group and only 1 patient in the RSL group were asymptomatic, but this was not statistically significant (P = .185) when compared against all other diagnoses.

Discussion

We defined RSL as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Patients with RSL and the surgeons who treat them are in a difficult position. In the setting of osteolysis, patients can be treated with serial radiographic imaging and clinical monitoring to determine if and when revision arthroplasty should be performed.¹⁷ However, given the complexity and risks associated with revision THA, surgeons should be aware that the acetabular shell may necessitate revision even if it does not appear to be frankly unstable on radiographic imaging.¹⁸

Of the 393 patients who underwent revision THA at our institution, 48.1% were evaluated with CT. Eighty-five of the 189 patients who underwent CT were diagnosed with radiographic loosening, or were diagnosed as needing urgent revision THA in the setting of loose components, periprosthetic infection, periprosthetic fracture, or catastrophic implant failure. Of the remaining 104 patients, 17 (16.3%) met the diagnosis of RSL of the acetabular component. The most common complaint was pain, and the most common diagnoses were osteolysis and polyethylene wear. Age and sex were not associated with increased likelihood of RSL.

Our study has several limitations. We defined the radiographic diagnosis of loose acetabular components as components showing frank migration, tilting, or a 2-mm concentric lucency on plain radiography or CT. Although these are common definitions of loose acetabular components, more sensitive radiographic measures have been described.¹⁶ We also excluded patients with recurrent dislocations and metal-on-metal prostheses, as these cases increase the metal artifact on CT and limit the ability to evaluate the bone–implant interface. Metal artifact remains an ongoing challenge to use of CT for post-THA imaging. However, tailored imaging protocols are helping to eliminate metal artifact. Bone scan was not used to evaluate for possible component loosening. Although sensitivity and specificity are about 67% and 76%, respectively,²⁰ Temmerman and colleagues²¹ also found poor intraobserver reliability (0.53) for bone scans in the setting of uncemented acetabular components. Last, our study did not evaluate the bony ingrowth patterns that corresponded to stable or unstable fixation and did not evaluate the volumetric size or anatomical location of the osteolytic lesions on CT. Careful assessment of these variables is clinically relevant when trying to determine if revision arthroplasty is warranted.

Although we used relatively simple radiographic criteria to define loose components, more sensitive and specific techniques have been described for both plain radiography and CT. Moore and colleagues²² described 5 radiographic signs of bony ingrowth; when 3 or more were present, sensitivity was 89.6% and specificity 76.9%. Mehin and colleagues²³ suggested that osteolysis involving more than 50% of the circumference of the shell on a standard pelvic radiograph might require revision arthroplasty. However, more recent studies have found that anteroposterior and lateral radiographs are less able to evaluate the anterior and posterior rims of the bone–implant interface, and it is this ingrowth area that may be the most crucial for stable osseointegration.^12,16

CT has expanded our ability to evaluate the bone–implant interface in 3 dimensions. Egawa and colleagues¹⁶ described using CT to evaluate the surface area involved with osteolysis and found that less than 40% involvement of the surface area generally corresponded to well-fixed components. Furthermore, they found that osteolysis generally creates lesions inferior and superior to the acetabular component and less often involves the anterior and posterior rims, which may be more important for stable fixation. The authors noted that volumetric analysis and CT were not as cost-effective as plain radiography and were more time- and skill-intensive.

Osteolysis itself remains a common indication for revision THA. However, the most appropriate procedure remains controversial. Mallory and colleagues²⁴ recommended explanting all acetabular shells in the setting of revision arthroplasty. They indicated that full assessment of the bony pelvis and any lytic defects was possible only with the wide exposure gained by acetabular component removal. More recent studies have begun to justify isolated component revision in the setting of well-fixed acetabular shells. Studies by Maloney and colleagues,¹⁰ Park and colleagues,¹⁵ and Beaulé and colleagues²⁵ have shown excellent outcomes with retention of well-fixed acetabular shells and removal of the wear generator in the setting of osteolysis. Haidukewych¹⁷ wrote that the goals in addressing osteolysis in revision THA are to eliminate the wear generator, débride osteolytic lesions, and restore bone stock. Surgeons should weigh the benefits of component retention and isolated liner exchange against the morbidity associated with explantation and preparation for implanting a new component. Good outcomes have been achieved with isolated component exchange, but surgeons should be aware that instability remains the most common complication after isolated liner exchange.⁸

The majority of our patients with RSL presented with complaints of pain and the diagnosis of osteolysis. One patient who had the diagnosis but was clinically asymptomatic was found to have a loose acetabular shell at time of revision surgery. Given the increased morbidity associated with acetabular component revision, this patient’s condition represents a dangerous combination of RSL and clinically asymptomatic component loosening. By raising awareness about RSL and its incidence, we should be able to increase our ability to detect RSL. A surgeon who detects RSL before gross migration or movement of the acetabular component may be better able to plan for revision arthroplasty before a catastrophic event that may necessitate a larger, more complex procedure. With the number of patients who require revision THA continuing to rise, surgeons should be aware of the incidence of RSL and the potential of RSL to affect patient care and potential surgical options.

Total hip arthroplasty (THA) is an excellent option for the treatment of osteoarthritis of the hip. In numerous studies, modern implants have shown survivorship of more than 90% at 10 years.^1,2 Polyethylene wear and subsequent osteolysis are major obstacles to the long-term success of THA.^3-5 Polyethylene wear particles are phagocytized by macrophages, inducing an inflammatory response that can ultimately lead to osteolysis of the bony architecture surrounding the bone–implant interface.^6,7 As modern implants often rely on direct implant-to-bone ingrowth to maintain fixation, wear at this junction can lead to aseptic component loosening and ultimately require revision surgery.^8-10 Osteolysis can be diagnosed with plain radiography or computed tomography (CT).¹¹ CT is more sensitive than plain radiography for the diagnosis of osteolysis and is better able to determine the size and location of osteolytic lesions.^12,13

Although diagnosis of osteolysis is well defined in the literature, what is more challenging is radiographic diagnosis of a loose acetabular component.¹¹ The most commonly described criteria for loosening are presence of a complete radiolucent line of more than 2 mm in width at the bone–implant interface and any progressive tilting or migration of the component.^14,15 CT-based criteria for component loosening remain largely undefined, though Egawa and colleagues¹⁶ showed that acetabular osteolysis involving less than 40% of the total cup surface is not associated with component loosening. Although a patient may show signs of osteolysis on postoperative imaging, this finding does not necessitate immediate revision surgery.¹⁷ Osteolysis may be monitored clinically and followed radiographically to determine when intervention is necessary.¹³

The goals of revision surgery are to eliminate the wear generator and bone-graft lytic lesions where needed to help maintain the bone–implant interface.¹⁷ The timing of such surgery is important, as the surgeon must balance the risk for gross component migration against the morbidity and mortality associated with acetabular component revision.¹⁸ This is in contrast to the settings of infection, periprosthetic fracture, recurrent instability, and component fracture/loosening, in which revision is urgently indicated and the case cannot be managed conservatively.

We conducted a study to determine the incidence of loose acetabular components without radiographic or clinical findings that would necessitate urgent revision THA. Radiographically silent loosening (RSL) was defined as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Although these patients make up a small minority of the revision population, knowing the incidence of RSL can help raise surgeon awareness of this potentially dangerous situation. We further sought to determine whether patients with RSL present with different demographic characteristics or clinical symptoms than patients with stable acetabular components.

Materials and Methods

In this retrospective, case–control, institutional review board–approved study, we evaluated patients who had undergone revision THA and had preoperative plain radiographs and CT images. We identified patients by International Classification of Diseases, Ninth Revision (ICD‑9) codes (00.70, 00.71, 00.72, 00.73, 80.05, 81.53, 84.56, 84.57) and searched for those cases treated between 2000 and 2012.

Inclusion criteria were confirmed revision THA and confirmed plain radiography and CT of the THA performed before revision. When osteolysis was diagnosed by plain radiography, CT was ordered to determine the extent of bony lesions or to evaluate for eccentric head position or component malposition. Last, all patients included in the study had a detailed operative report clearly indicating acetabular component stability at time of revision. Acetabular component stability at time of surgery was determined according to the criteria defined by Berger and colleagues.¹⁹ Cups were evaluated for gross motion during both hip dislocation and during edge loading of the component after thorough scar and capsular débridement.

Patients who did not have CT performed before revision surgery were excluded from the study. These patients had been diagnosed by clinical history and/or plain radiography. Cases revised for periprosthetic infection or periprosthetic fracture were also excluded. Patients with metal-on-metal bearings were excluded, as were any cases revised from hemiarthroplasty to THA, as well as cases revised for recurrent dislocations or component malposition.

All plain radiographs and CT images were evaluated by the orthopedic surgeon who performed the revision and by a radiologist. Images were inspected for signs of gross component migration, tilting, and concentric lucency of the bone–implant interface. Patients with imaging that showed signs of component movement or migration (as seen by the attending surgeon or the radiologist) were excluded. Patients with radiographic evidence of femoral stem loosening were also excluded, as they had an indication to undergo revision arthroplasty. The remaining patients were then stratified into 2 groups: those with stable acetabular components at time of revision and those with loose acetabular components. Stable acetabular shells showed no gross motion of the implant with dislocation, edge loading with an impactor, or pulling with a Kocher clamp after débridement and screw removal.^15,19 The 2 groups were then compared with respect to age, sex, and most common presenting symptoms and diagnoses. Fischer exact test and Student t test were used to statistically compare the groups.

Results

Overall, 393 patients underwent revision arthroplasty for the diagnoses (ICD-9 codes) indicated (Figure). One hundred eighty-nine patients (48.1%) had CT performed before revision. Of these 189 patients, 85 were excluded for diagnoses that were evident on either plain radiography or CT, that necessitated urgent revision, or for procedures beyond the scope of the study (Table 1). CT showed a loose cup in 28 patients; 6 of these cups were also seen on CT. Thirteen patients were diagnosed with a loose femoral stem, 10 with a periprosthetic infection, and 8 with a periprosthetic fracture.

One hundred four patients (54 men, 50 women) met the study inclusion criteria. Mean age was 65.1 years. Of these 104 patients, 87 (83.7%) had a stable acetabular shell at time of revision surgery; the other 17 (16.3%) were diagnosed with RSL of the acetabular shell. Osteolysis was the most common diagnosis (89.4%) in the overall population, and pain was the most common complaint at time of presentation (66.6%). Lack of symptoms was the second most common presentation at time of revision (19.2%) (Table 2). Patients without symptoms underwent revision surgery because of concern about impending compromise of the bone–implant interface and progressive osteolysis.

The 2 groups (stable vs unstable acetabular shells) were not significantly different with respect to age (P = .961) or sex distribution (P = .185). All patients in the RSL group were diagnosed with osteolysis radiographically, and 15 (88%) of 17 patients presented with pain as the primary complaint, compared with only 54 (62%) of 87 patients in the group with stable shells. Patients with RSL were significantly more likely to present with pain as the primary complaint (P = .0487). Nineteen patients in the stable implant group and only 1 patient in the RSL group were asymptomatic, but this was not statistically significant (P = .185) when compared against all other diagnoses.

Discussion

We defined RSL as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Patients with RSL and the surgeons who treat them are in a difficult position. In the setting of osteolysis, patients can be treated with serial radiographic imaging and clinical monitoring to determine if and when revision arthroplasty should be performed.¹⁷ However, given the complexity and risks associated with revision THA, surgeons should be aware that the acetabular shell may necessitate revision even if it does not appear to be frankly unstable on radiographic imaging.¹⁸

Of the 393 patients who underwent revision THA at our institution, 48.1% were evaluated with CT. Eighty-five of the 189 patients who underwent CT were diagnosed with radiographic loosening, or were diagnosed as needing urgent revision THA in the setting of loose components, periprosthetic infection, periprosthetic fracture, or catastrophic implant failure. Of the remaining 104 patients, 17 (16.3%) met the diagnosis of RSL of the acetabular component. The most common complaint was pain, and the most common diagnoses were osteolysis and polyethylene wear. Age and sex were not associated with increased likelihood of RSL.

Our study has several limitations. We defined the radiographic diagnosis of loose acetabular components as components showing frank migration, tilting, or a 2-mm concentric lucency on plain radiography or CT. Although these are common definitions of loose acetabular components, more sensitive radiographic measures have been described.¹⁶ We also excluded patients with recurrent dislocations and metal-on-metal prostheses, as these cases increase the metal artifact on CT and limit the ability to evaluate the bone–implant interface. Metal artifact remains an ongoing challenge to use of CT for post-THA imaging. However, tailored imaging protocols are helping to eliminate metal artifact. Bone scan was not used to evaluate for possible component loosening. Although sensitivity and specificity are about 67% and 76%, respectively,²⁰ Temmerman and colleagues²¹ also found poor intraobserver reliability (0.53) for bone scans in the setting of uncemented acetabular components. Last, our study did not evaluate the bony ingrowth patterns that corresponded to stable or unstable fixation and did not evaluate the volumetric size or anatomical location of the osteolytic lesions on CT. Careful assessment of these variables is clinically relevant when trying to determine if revision arthroplasty is warranted.

Although we used relatively simple radiographic criteria to define loose components, more sensitive and specific techniques have been described for both plain radiography and CT. Moore and colleagues²² described 5 radiographic signs of bony ingrowth; when 3 or more were present, sensitivity was 89.6% and specificity 76.9%. Mehin and colleagues²³ suggested that osteolysis involving more than 50% of the circumference of the shell on a standard pelvic radiograph might require revision arthroplasty. However, more recent studies have found that anteroposterior and lateral radiographs are less able to evaluate the anterior and posterior rims of the bone–implant interface, and it is this ingrowth area that may be the most crucial for stable osseointegration.^12,16

CT has expanded our ability to evaluate the bone–implant interface in 3 dimensions. Egawa and colleagues¹⁶ described using CT to evaluate the surface area involved with osteolysis and found that less than 40% involvement of the surface area generally corresponded to well-fixed components. Furthermore, they found that osteolysis generally creates lesions inferior and superior to the acetabular component and less often involves the anterior and posterior rims, which may be more important for stable fixation. The authors noted that volumetric analysis and CT were not as cost-effective as plain radiography and were more time- and skill-intensive.

Osteolysis itself remains a common indication for revision THA. However, the most appropriate procedure remains controversial. Mallory and colleagues²⁴ recommended explanting all acetabular shells in the setting of revision arthroplasty. They indicated that full assessment of the bony pelvis and any lytic defects was possible only with the wide exposure gained by acetabular component removal. More recent studies have begun to justify isolated component revision in the setting of well-fixed acetabular shells. Studies by Maloney and colleagues,¹⁰ Park and colleagues,¹⁵ and Beaulé and colleagues²⁵ have shown excellent outcomes with retention of well-fixed acetabular shells and removal of the wear generator in the setting of osteolysis. Haidukewych¹⁷ wrote that the goals in addressing osteolysis in revision THA are to eliminate the wear generator, débride osteolytic lesions, and restore bone stock. Surgeons should weigh the benefits of component retention and isolated liner exchange against the morbidity associated with explantation and preparation for implanting a new component. Good outcomes have been achieved with isolated component exchange, but surgeons should be aware that instability remains the most common complication after isolated liner exchange.⁸

The majority of our patients with RSL presented with complaints of pain and the diagnosis of osteolysis. One patient who had the diagnosis but was clinically asymptomatic was found to have a loose acetabular shell at time of revision surgery. Given the increased morbidity associated with acetabular component revision, this patient’s condition represents a dangerous combination of RSL and clinically asymptomatic component loosening. By raising awareness about RSL and its incidence, we should be able to increase our ability to detect RSL. A surgeon who detects RSL before gross migration or movement of the acetabular component may be better able to plan for revision arthroplasty before a catastrophic event that may necessitate a larger, more complex procedure. With the number of patients who require revision THA continuing to rise, surgeons should be aware of the incidence of RSL and the potential of RSL to affect patient care and potential surgical options.

Total hip arthroplasty (THA) is an excellent option for the treatment of osteoarthritis of the hip. In numerous studies, modern implants have shown survivorship of more than 90% at 10 years.^1,2 Polyethylene wear and subsequent osteolysis are major obstacles to the long-term success of THA.^3-5 Polyethylene wear particles are phagocytized by macrophages, inducing an inflammatory response that can ultimately lead to osteolysis of the bony architecture surrounding the bone–implant interface.^6,7 As modern implants often rely on direct implant-to-bone ingrowth to maintain fixation, wear at this junction can lead to aseptic component loosening and ultimately require revision surgery.^8-10 Osteolysis can be diagnosed with plain radiography or computed tomography (CT).¹¹ CT is more sensitive than plain radiography for the diagnosis of osteolysis and is better able to determine the size and location of osteolytic lesions.^12,13

Although diagnosis of osteolysis is well defined in the literature, what is more challenging is radiographic diagnosis of a loose acetabular component.¹¹ The most commonly described criteria for loosening are presence of a complete radiolucent line of more than 2 mm in width at the bone–implant interface and any progressive tilting or migration of the component.^14,15 CT-based criteria for component loosening remain largely undefined, though Egawa and colleagues¹⁶ showed that acetabular osteolysis involving less than 40% of the total cup surface is not associated with component loosening. Although a patient may show signs of osteolysis on postoperative imaging, this finding does not necessitate immediate revision surgery.¹⁷ Osteolysis may be monitored clinically and followed radiographically to determine when intervention is necessary.¹³

The goals of revision surgery are to eliminate the wear generator and bone-graft lytic lesions where needed to help maintain the bone–implant interface.¹⁷ The timing of such surgery is important, as the surgeon must balance the risk for gross component migration against the morbidity and mortality associated with acetabular component revision.¹⁸ This is in contrast to the settings of infection, periprosthetic fracture, recurrent instability, and component fracture/loosening, in which revision is urgently indicated and the case cannot be managed conservatively.

We conducted a study to determine the incidence of loose acetabular components without radiographic or clinical findings that would necessitate urgent revision THA. Radiographically silent loosening (RSL) was defined as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Although these patients make up a small minority of the revision population, knowing the incidence of RSL can help raise surgeon awareness of this potentially dangerous situation. We further sought to determine whether patients with RSL present with different demographic characteristics or clinical symptoms than patients with stable acetabular components.

Materials and Methods

In this retrospective, case–control, institutional review board–approved study, we evaluated patients who had undergone revision THA and had preoperative plain radiographs and CT images. We identified patients by International Classification of Diseases, Ninth Revision (ICD‑9) codes (00.70, 00.71, 00.72, 00.73, 80.05, 81.53, 84.56, 84.57) and searched for those cases treated between 2000 and 2012.

Inclusion criteria were confirmed revision THA and confirmed plain radiography and CT of the THA performed before revision. When osteolysis was diagnosed by plain radiography, CT was ordered to determine the extent of bony lesions or to evaluate for eccentric head position or component malposition. Last, all patients included in the study had a detailed operative report clearly indicating acetabular component stability at time of revision. Acetabular component stability at time of surgery was determined according to the criteria defined by Berger and colleagues.¹⁹ Cups were evaluated for gross motion during both hip dislocation and during edge loading of the component after thorough scar and capsular débridement.

Patients who did not have CT performed before revision surgery were excluded from the study. These patients had been diagnosed by clinical history and/or plain radiography. Cases revised for periprosthetic infection or periprosthetic fracture were also excluded. Patients with metal-on-metal bearings were excluded, as were any cases revised from hemiarthroplasty to THA, as well as cases revised for recurrent dislocations or component malposition.

All plain radiographs and CT images were evaluated by the orthopedic surgeon who performed the revision and by a radiologist. Images were inspected for signs of gross component migration, tilting, and concentric lucency of the bone–implant interface. Patients with imaging that showed signs of component movement or migration (as seen by the attending surgeon or the radiologist) were excluded. Patients with radiographic evidence of femoral stem loosening were also excluded, as they had an indication to undergo revision arthroplasty. The remaining patients were then stratified into 2 groups: those with stable acetabular components at time of revision and those with loose acetabular components. Stable acetabular shells showed no gross motion of the implant with dislocation, edge loading with an impactor, or pulling with a Kocher clamp after débridement and screw removal.^15,19 The 2 groups were then compared with respect to age, sex, and most common presenting symptoms and diagnoses. Fischer exact test and Student t test were used to statistically compare the groups.

Results

Overall, 393 patients underwent revision arthroplasty for the diagnoses (ICD-9 codes) indicated (Figure). One hundred eighty-nine patients (48.1%) had CT performed before revision. Of these 189 patients, 85 were excluded for diagnoses that were evident on either plain radiography or CT, that necessitated urgent revision, or for procedures beyond the scope of the study (Table 1). CT showed a loose cup in 28 patients; 6 of these cups were also seen on CT. Thirteen patients were diagnosed with a loose femoral stem, 10 with a periprosthetic infection, and 8 with a periprosthetic fracture.

One hundred four patients (54 men, 50 women) met the study inclusion criteria. Mean age was 65.1 years. Of these 104 patients, 87 (83.7%) had a stable acetabular shell at time of revision surgery; the other 17 (16.3%) were diagnosed with RSL of the acetabular shell. Osteolysis was the most common diagnosis (89.4%) in the overall population, and pain was the most common complaint at time of presentation (66.6%). Lack of symptoms was the second most common presentation at time of revision (19.2%) (Table 2). Patients without symptoms underwent revision surgery because of concern about impending compromise of the bone–implant interface and progressive osteolysis.

The 2 groups (stable vs unstable acetabular shells) were not significantly different with respect to age (P = .961) or sex distribution (P = .185). All patients in the RSL group were diagnosed with osteolysis radiographically, and 15 (88%) of 17 patients presented with pain as the primary complaint, compared with only 54 (62%) of 87 patients in the group with stable shells. Patients with RSL were significantly more likely to present with pain as the primary complaint (P = .0487). Nineteen patients in the stable implant group and only 1 patient in the RSL group were asymptomatic, but this was not statistically significant (P = .185) when compared against all other diagnoses.

Discussion

We defined RSL as an acetabular component that was loose at time of revision surgery but that did not show frank signs of loosening on either plain radiography or CT. Patients with RSL and the surgeons who treat them are in a difficult position. In the setting of osteolysis, patients can be treated with serial radiographic imaging and clinical monitoring to determine if and when revision arthroplasty should be performed.¹⁷ However, given the complexity and risks associated with revision THA, surgeons should be aware that the acetabular shell may necessitate revision even if it does not appear to be frankly unstable on radiographic imaging.¹⁸

Of the 393 patients who underwent revision THA at our institution, 48.1% were evaluated with CT. Eighty-five of the 189 patients who underwent CT were diagnosed with radiographic loosening, or were diagnosed as needing urgent revision THA in the setting of loose components, periprosthetic infection, periprosthetic fracture, or catastrophic implant failure. Of the remaining 104 patients, 17 (16.3%) met the diagnosis of RSL of the acetabular component. The most common complaint was pain, and the most common diagnoses were osteolysis and polyethylene wear. Age and sex were not associated with increased likelihood of RSL.

Our study has several limitations. We defined the radiographic diagnosis of loose acetabular components as components showing frank migration, tilting, or a 2-mm concentric lucency on plain radiography or CT. Although these are common definitions of loose acetabular components, more sensitive radiographic measures have been described.¹⁶ We also excluded patients with recurrent dislocations and metal-on-metal prostheses, as these cases increase the metal artifact on CT and limit the ability to evaluate the bone–implant interface. Metal artifact remains an ongoing challenge to use of CT for post-THA imaging. However, tailored imaging protocols are helping to eliminate metal artifact. Bone scan was not used to evaluate for possible component loosening. Although sensitivity and specificity are about 67% and 76%, respectively,²⁰ Temmerman and colleagues²¹ also found poor intraobserver reliability (0.53) for bone scans in the setting of uncemented acetabular components. Last, our study did not evaluate the bony ingrowth patterns that corresponded to stable or unstable fixation and did not evaluate the volumetric size or anatomical location of the osteolytic lesions on CT. Careful assessment of these variables is clinically relevant when trying to determine if revision arthroplasty is warranted.

Although we used relatively simple radiographic criteria to define loose components, more sensitive and specific techniques have been described for both plain radiography and CT. Moore and colleagues²² described 5 radiographic signs of bony ingrowth; when 3 or more were present, sensitivity was 89.6% and specificity 76.9%. Mehin and colleagues²³ suggested that osteolysis involving more than 50% of the circumference of the shell on a standard pelvic radiograph might require revision arthroplasty. However, more recent studies have found that anteroposterior and lateral radiographs are less able to evaluate the anterior and posterior rims of the bone–implant interface, and it is this ingrowth area that may be the most crucial for stable osseointegration.^12,16

CT has expanded our ability to evaluate the bone–implant interface in 3 dimensions. Egawa and colleagues¹⁶ described using CT to evaluate the surface area involved with osteolysis and found that less than 40% involvement of the surface area generally corresponded to well-fixed components. Furthermore, they found that osteolysis generally creates lesions inferior and superior to the acetabular component and less often involves the anterior and posterior rims, which may be more important for stable fixation. The authors noted that volumetric analysis and CT were not as cost-effective as plain radiography and were more time- and skill-intensive.

Osteolysis itself remains a common indication for revision THA. However, the most appropriate procedure remains controversial. Mallory and colleagues²⁴ recommended explanting all acetabular shells in the setting of revision arthroplasty. They indicated that full assessment of the bony pelvis and any lytic defects was possible only with the wide exposure gained by acetabular component removal. More recent studies have begun to justify isolated component revision in the setting of well-fixed acetabular shells. Studies by Maloney and colleagues,¹⁰ Park and colleagues,¹⁵ and Beaulé and colleagues²⁵ have shown excellent outcomes with retention of well-fixed acetabular shells and removal of the wear generator in the setting of osteolysis. Haidukewych¹⁷ wrote that the goals in addressing osteolysis in revision THA are to eliminate the wear generator, débride osteolytic lesions, and restore bone stock. Surgeons should weigh the benefits of component retention and isolated liner exchange against the morbidity associated with explantation and preparation for implanting a new component. Good outcomes have been achieved with isolated component exchange, but surgeons should be aware that instability remains the most common complication after isolated liner exchange.⁸

The majority of our patients with RSL presented with complaints of pain and the diagnosis of osteolysis. One patient who had the diagnosis but was clinically asymptomatic was found to have a loose acetabular shell at time of revision surgery. Given the increased morbidity associated with acetabular component revision, this patient’s condition represents a dangerous combination of RSL and clinically asymptomatic component loosening. By raising awareness about RSL and its incidence, we should be able to increase our ability to detect RSL. A surgeon who detects RSL before gross migration or movement of the acetabular component may be better able to plan for revision arthroplasty before a catastrophic event that may necessitate a larger, more complex procedure. With the number of patients who require revision THA continuing to rise, surgeons should be aware of the incidence of RSL and the potential of RSL to affect patient care and potential surgical options.