The influence of head size and sex on the outcome of Birmingham hip resurfacing

What is the long-term survivorship, complication profile, and patient reported outcomes after Birmingham hip resurfacing?

Introduction

When indicated, Birmingham Hip Resurfacing (BHR) presents a viable alternative to total hip arthroplasty (THA), but there remain questions about the long-term outcomes of BHR. Therefore, we asked: 1) what are the long-term patient-reported outcomes and 2) survivorship rates following BHR; 3) what are the causes for revision surgery after BHR? and 4) how have these outcomes compared to THA at long-term follow-up.

Methods

A query of PubMed, MEDLINE, Scopus, and Cochrane in September 2023 was performed. Articles were included if they reported BHR survivorship rates at ≥10 years. Survivorship was defined as an all-cause revision of any BHR component. This review encompasses 26 articles, totaling 13,103 hips. Mean follow-up ranged from 6.0 to 20.9 years, but each study had at least a subgroup analysis for ≥10-year follow-up.

Results

Five studies compared preoperative and postoperative PROs for BHR, with four reporting improvement in at least one PRO after 10-year follow-up. Overall, survivorship rates ranged from 83% to 100% across diverse long-term timeframes, with 25 of 26 studies reporting 10-year survivorship rates greater than 87%. The primary reasons for revisions were implant loosening (22%), adverse reactions to metal debris (21.2%), and fractures of any kind (17.2%). In the six studies that compared BHR to THA, long-term survivorship was similar while BHR exhibited slightly superior activity levels.

Conclusion

The findings from this study suggested favorable long-term survivorship and postoperative outcomes of BHR. In studies comparing long-term BHR and THA, survivorship was comparable, with BHR potentially providing enhanced postoperative activity levels.

Common Factors in Shoulder and Hip Arthroplasty Implant Failures: A Historical Review

In this era of subspecialty care in orthopedics, iterations of implant design can occur in a silo which then precludes gaining knowledge from failures of implant design that may have occurred in different subspecialties. This literature review describes the history of failures in hip and shoulder arthroplasties with the purpose of identifying similar factors that led to previous implant failures. A review of the literature was performed by two reviewers assessing articles that described failed hip and shoulder arthroplasty systems over time. We identified and analyzed 53 implant failures-23 in hip arthroplasty and 30 in shoulder arthroplasty. These failures were categorized as material, mechanical, and technical. In hip arthroplasty, 48% were material, 39% mechanical, and 13% technical failures. In shoulder arthroplasty, the distribution was 10% material, 70% mechanical, and 20% technical failures. The distribution of these failures highlights similar and sometimes repeated failure mechanisms between subspecialties. This accentuates the importance of a collaborative approach to improve future arthroplasty designs.

Clinical outcomes and return to dance after total hip arthroplasty or hip resurfacing in professional dancers

Aims

Professional dancers represent a unique patient population in the setting of hip arthroplasty, given the high degree of hip strength and mobility required by their profession. We sought to determine the clinical outcomes and ability to return to professional dance after total hip arthroplasty (THA) or hip resurfacing arthroplasty (HRA).

Methods

Active professional dancers who underwent primary THA or HRA at a single institution with minimum one-year follow-up were included in the study. Primary outcomes included the rate of return to professional dance, three patient-reported outcome measures (PROMs) (modified Harris Hip Score (mHHS), Hip disability and Osteoarthritis Outcome Score for Joint Replacement (HOOS-JR), and Lower Extremity Activity Scale (LEAS)), and postoperative complications.

Results

A total of 49 hips in 39 patients (mean age 56 years (SD 13); 80% female (n = 39)) were included. Mean follow-up was 4.9 years (SD 5.1). Of these 49 hips, 37 THAs and 12 HRAs were performed. In all, 96% of hips returned to professional dance activities postoperatively. With regard to PROMs, there were statistically significant improvements in mHHS, HOOS-JR, and LEAS from baseline to ≥ one year postoperatively. There were complications in 7/49 hips postoperatively (14%), five of which required revision surgery (10%). There were no revisions for instability after the index procedure. Two complications (5.4%) occurred in hips that underwent THA compared with five (42%) after HRA (p = 0.007), though the difference by procedure was not significantly different when including only contemporary implant designs (p = 0.334).

Conclusion

Active professional dancers experienced significant improvements in functional outcome scores after THA or HRA, with a 96% rate of return to professional dance. However, the revision rate at short- to mid-term follow-up highlights the challenges of performing hip arthroplasty in this demanding patient population. Further investigation is required to determine the results of THA versus HRA using contemporary implant designs in these patients.

Clinical, functional and radiographic long-term follow-up (7-12 years) of Birmingham Hip Resurfacing, including metal ions evaluation: a single surgeon series

Hip resurfacing arthroplasty (HRA) has been advocated as an attractive therapy for a younger, more demanding patient population with debilitating hip osteoarthritis. Controversies surrounding metal-on-metal (MoM) hip resurfacing have, however, led to a significant decline in the popularity of the HRA. Despite this, substantial evidence supports the use of specific implants in a selected group of patients. This is a continued retrospective analysis of a single surgeon series of the Birmingham Hip Resurfacing (BHR). Initial medium-term analysis was done in 2011 and published by Van der Bracht et al.13. This analysis includes a long-term follow-up of 7 to 12 years, including functional scoring (HHS, HOOS and UCLA activity score), metal ion evaluation and survival analysis. Failure was defined as revision for any cause. A total of 267 resurfacing procedures with the BHR were included in 247 patients. We had a mean follow-up of 8.3 years. Overall survival at ten years was 94.8%(97.2% for males and 90.1% for females). There was a statistically significant increase in mean HHS score at follow-up (56.03 - IQR 47-65 to 96.07 - IQR 96-100). Elevated metal ions were correlated with a statistically significant increase in the probability of complications. This cohort study further proved that hip resurfacing arthroplasty with the Birmingham Hip Resurfacing implant provides a good alternative to conventional total hip arthroplasty in young patients. There was a significant increase in functional scores at follow-up. There is further evidence of less favorable outcomes in female patients.

Careful patient selection together with optimal implant positioning may reduce but does not eliminate the risk of elevated serum cobalt and chrome levels following metal-on-metal hip resurfacing

BACKGROUND

Elevated serum chrome (sCr) and cobalt (sCo) concentrations are associated with local tissue adverse reactions to metal debris following metal-on-metal hip resurfacing (MoM-HR). Serum metal ions <2 µg/l are probably of little clinical relevance and a pragmatic "safe" threshold <5 µg/l has been suggested.The primary aim of this study was to evaluate if a careful selection of patients combined with optimal implant positioning could eliminate cases with "unsafe" serum metal ion levels. A secondary aim was to study the association between different risk factors and having Co and/or Cr levels >5 µg/l.

PATIENTS AND METHODS

This is a retrospective, single-institution cohort study of 410 consecutive patients operated on with a Birmingham Hip Resurfacing (BHR) implant between 2001 and 2014. 288 of these had a unilateral MoM-HR, pelvic and true lateral radiographs, and a related sCo and sCr sample, and were included in the final analysis. They were allocated to either a presumed "optimal group" consisting of only men aged <60 years old, with femoral head component >48 mm diameter, and with a cup positioned within Lewinnek's safe zones, or a "suboptimal group" consisting of the remaining patients. Fisher's exact test and multiple logistic regression analyses were performed.

RESULTS

In the optimal group 48% (47/97) had serum metal ions >2 µg/l and 8% (8/97) >5 µg/l compared to 61% (116/191) and 18% (34/191) in the suboptimal group, p = 0.059 and p = 0.034 respectively. Acetabular cups with an anteversion <5 degrees had the highest odds ratio, 6.5 (95% CI, 3.0-14.3), of having sCo and sCr concentrations exceeding 5 µg/l.

CONCLUSIONS

A well oriented BHR acetabular component in a presumably "optimal" patient reduces the risk of having elevated serum metal ions but does not eliminate it. Insufficient cup anteversion seems to be the strongest associated factor of elevated serum metals.

Midterm results of the Birmingham hip resurfacing: a single-surgeon series

INTRODUCTION

Birmingham hip resurfacing (BHR) is readily used as alternative to total hip replacement in younger patients. The current study aims to compare outcomes in terms of adverse local tissue reactions (ALTR), elevated metal ion levels and survival rates between low-risk (femoral component size ≥ 48 mm) and high-risk (femoral component size < 48 mm) BHR patients at a minimum 5-year follow-up (FU).

MATERIALS AND METHODS

We report the minimum 5-year, single surgeon outcome results of 183 BHRs, performed between 2007 and 2012. 154 patients, 18 women (20 hips) and 136 men (163 hips) were included in the study. Patients were grouped in 149 low-risk cases (femoral component size ≥ 48 mm) and in 34 high-risk cases (18 female/12 male) patients with a femoral head size < 48 mm).

RESULTS

At a minimum of 5-years FU time, 91% of the patients were available for FU. The overall survival rate was 91.8%. There were five revisions (survival rate 96.6%) in the low-risk group and ten revisions (survival rate 70.6%) in the high-risk group. In the low-risk group, six patients (6.5%) showed elevated metal ion levels (> 7 μg/l), compared to five patients (20.8%) in the high risk-group (p = 0.03).

CONCLUSION

Including the surgeon's initial learning curve, the BHR shows very good mid-term survival rates in the low-risk group but should, as previously demonstrated, not be considered for patients with less than 48 mm femoral head size.

LEVEL OF EVIDENCE

Level III: retrospective cohort study.

Hip resurfacing and posterior approach total hip arthroplasty have equivalent blood loss when tranexamic acid is used: a propensity score matched cohort analysis

INTRODUCTION

Hip resurfacing (HR) requires a larger approach and soft tissue dissection and might therefore be associated with increased blood loss compared to total hip arthroplasty (THA). However, the effect of the adoption of tranexamic acid (TXA) in this setting is unknown. Therefore, the current study compares the blood loss and transfusion requirements between HR and posterior THA in patients receiving TXA.

MATERIALS AND METHODS

This retrospective cohort study included patients undergoing primary, unilateral THA or HR using a posterior approach between February 2016 and 2020 in which TXA was administered. THA and HR patients were propensity score matched using nearest neighbor greedy matching accounting for demographic, health and surgical variables. Postoperative hemoglobin (Hgb) levels and Hgb drop from preoperative to post-operative day (POD) 1 were compared using t-tests and associated risk factors were assessed using linear mixed modelling.

RESULTS

After matching, each cohort consisted of 1395 patients. Cohorts were similar regarding age, sex, BMI, and Charlson Comorbidity Index. No significant differences were found for Hgb levels on POD 1 (12.3 g/dl; p = 0.90) or Hgb drop (2.3 g/dl; p = 0.87). Duration of surgery was significantly longer for HR patients (82 vs 77 min; p < 0.01). Transfusion rate was 0.1% in both cohorts (p = 1.00). Hospital stay was significantly shorter for HR patients (1 vs 2 days; p < 0.01).

CONCLUSION

HR using a standard TXA regimen is not associated with greater perioperative blood loss than posterior THA and does not result in increased transfusion requirements. Both surgical procedures can be considered equally safe in terms of perioperative blood management when TXA is used.

Metal-on-metal hip resurfacing arthroplasty provides excellent long-term survivorship and function in patients with a good-sized femoral head : results of a single, non-designer surgeon's cohort

Aims

To establish the survivorship, function, and metal ion levels in an unselected series of metal-on-metal hip resurfacing arthroplasties (HRAs) performed by a non-designer surgeon.

Methods

We reviewed 105 consecutive HRAs in 83 patients, performed by a single surgeon, at a mean follow-up of 14.9 years (9.3 to 19.1). The cohort included 45 male and 38 female patients, with a mean age of 49.5 years (SD 12.5)

Results

At the time of review 13 patients with 15 hips had died from causes unrelated to the hip operation, and 14 hips had undergone revision surgery, giving an overall survival rate of rate of 86.7% (95% confidence interval (CI) 84.2 to 89.1). The survival rate in men was 97.7% (95% CI 96.3 to 98.9) and in women was 73.4% (95% CI 70.6 to 75.1). The median head size of the failed group was 42 mm (interquartile range (IQR) 42 to 44), and in the surviving group was 50 mm (IQR 46 to 50). In all, 13 of the 14 revised hips had a femoral component measuring ≤ 46 mm. The mean blood levels of cobalt and chromium ions were 26.6 nmol/l (SD 24.5) and 30.6 nmol/l (SD 15.3), respectively. No metal ion levels exceeded the safe limit. The mean Oxford Hip Score was 41.5 (SD 8.9) and Harris Hip Score was 89.9 (14.8). In the surviving group, four patients had radiolucent lines around the stem of the femoral component, and one had lysis around the acetabular component; eight hips demonstrated heterotopic ossification.

Conclusion

Our results confirm the existing understanding that HRA provides good long-term survival and function in patients with adequate-sized femoral heads. This is evidenced by a 97.7% survival rate among men (larger heads) in our series at a mean follow-up of 14.9 years. Failure is closely related to head sizes ≤ 46 cm.

Cite this article: Bone Jt Open 2022;3(1):68–76.

A Comparative Cohort Study With a 20-Year Age Gap: Hip Resurfacing in Patients Aged ≤35 Years and Patients Aged ≥55 Years

Background

This single-center retrospective cohort study aimed to evaluate and compare implant survival and patient-reported outcome measures in 2 distinct age groups separated by 20 years who underwent hip resurfacing arthroplasty (HRA).

Methods

Between 2005 and 2014, 2042 HRAs were performed by a single-surgeon, and 75 and 377 hips from patients aged ≤35 years and ≥55 years, respectively, were included in this study. Implant survival was determined for all available hips. Clinical features and patient-reported outcome measures were collected.

Results

Seven hips were revised, 4 for aseptic loosening of one or both components, one for infection, one for accelerated wear and metallosis, and one for femoral neck fracture. There was no difference in all-cause 10-year revision, with 97.1% (95% confidence interval 80.9 to 99.6) and 99.6% (95% confidence interval: 97 to 99.9) survivorship in younger and older patients, respectively (P = .246). Preoperatively, younger patients were less active than older patients on the Lower Extremity Activity Scale (LEAS) or University of California, Los Angeles, activity scale, but at follow-up, younger patients outpaced older ones.

Conclusion

Original to our study was the isolation and comparison of 2 distinct age groups. With excellent results in disparate age groups, HRA can be applied to a broad patient demographic and is suitable for those patients who want to achieve a high activity level as defined by Lower Extremity Activity Scale or University of California, Los Angeles, scores.

Sex-specific risk factors determine the survivorship of female and male patients after metal-on-metal hip resurfacing

BACKGROUND

The need for revision surgery after hip resurfacing arthroplasty (HRA) is more prevalent for women than for men. However, there is a paucity of information to explain this observation. We aimed (1) to determine sex-specific risk factors leading to revision surgery; and (2) to correlate these risk factors to the dominant modes of failure of HRA.

METHODS

1101 patients (1375 consecutive hips) including 292 women (355 hips) and 809 men (1020 hips) with a mean age of 51.3 years were included regardless of bone quality. The contact patch to rim distance was computed.

RESULTS

A contact patch to rim (CPR) distance of ⩽7 mm, an aetiology of developmental dysplasia, a postoperative abduction-adduction arc of ⩾95°, and a metaphyseal stem left uncemented were risk factors associated with revision surgery for female patients, while a CPR distance of ⩽10 mm, a component size of ⩽46 mm, an age at surgery of ⩽55 years, and an early femoral preparation technique were risk factors for male patients. Hips with no risk factors from the female group had a survivorship of 98.7% at 15 years, matching or exceeding the results of all male subgroups. However the risk factors in the female group increased the risk of revision much more than in the male group.

CONCLUSIONS

In the absence of risk factors, the survivorship of HRA in female patients is equal to that of males. Many female patients can safely benefit from HRA by excluding severe dysplasia and optimising surgical technique.

Preliminary report of clinical experience with metal-on-highly-crosslinked-polyethylene hip resurfacing

Objectives

Modern metal-on-metal (MoM) hip resurfacing arthroplasty (HRA), while achieving good results with well-orientated, well-designed components in ideal patients, is contraindicated in women, men with head size under 50 mm, or metal hypersensitivity. These patients currently have no access to the benefits of HRA. Highly crosslinked polyethylene (XLPE) has demonstrated clinical success in total hip arthroplasty (THA) and, when used in HRA, potentially reduces metal ion-related sequelae. We report the early performance of HRA using a direct-to-bone cementless mono-bloc XLPE component coupled with a cobalt-chrome femoral head, in the patient group for whom HRA is currently contraindicated.

Methods

This is a cross-sectional, observational assessment of 88 consecutive metal-on-XLPE HRAs performed in 84 patients between 2015 and 2018 in three centres (three surgeons, including the designer surgeon). Mean follow-up is 1.6 years (0.7 to 3.9). Mean age at operation was 56 years (sd 11; 21 to 82), and 73% of implantations were in female patients. All patients were individually counselled, and a detailed informed consent was obtained prior to operation. Primary resurfacing was carried out in 85 hips, and three cases involved revision of previous MoM HRA. Clinical, radiological, and Oxford Hip Score (OHS) assessments were studied, along with implant survival.

Results

There was no loss to follow-up and no actual or impending revision or reoperation. Median OHS increased from 24 (interquartile range (IQR) 20 to 28) preoperatively to 48 (IQR 46 to 48) at the latest follow-up (48 being the best possible score). Radiographs showed one patient had a head-neck junction lucency. No other radiolucency, osteolysis, component migration, or femoral neck thinning was noted.

Conclusion

The results in this small consecutive cohort suggest that metal-on-monobloc-XLPE HRA is successful in the short term and merits further investigation as a conservative alternative to the current accepted standard of stemmed THA. However, we would stress that survival data with longer-term follow-up are needed prior to widespread adoption.

Cite this article: R. B. C. Treacy, J. P. Holland, J. Daniel, H. Ziaee, D. J. W. McMinn. Preliminary report of clinical experience with metal-on-highly-crosslinked-polyethylene hip resurfacing. Bone Joint Res 2019;8:443–450. DOI: 10.1302/2046-3758.810.BJR-2019-0060.R1

Computer-assisted Navigation in Hip Resurfacing Arthroplasty: A Case Study utilizing the ReCap Femoral Resurfacing System

Introduction:

The ReCap Femoral Resurfacing System has been associated with increased cases of revision surgery when compared to other hip resurfacing systems. However, computer-assisted navigation may have the potential to reduce the risk of post-operative complications by providing more accurate intraoperative measurements for acetabular component positioning.

Case Report:

The present case describes an active 46-year-old male presenting with severe osteoarthritis of the right hip who elected to undergo a ReCap resurfacing arthroplasty with navigation. Results demonstrated accurate acetabular component position and leg length measurements to within <1° and 1mm of standard radiographic measurements.

Conclusion:

These findings are the first to describe the use of navigation with the ReCap system and provide encouraging results for further clinical evaluation.

Establishing thresholds for metal ion levels in patients with bilateral Articular Surface Replacement hip arthroplasty

INTRODUCTION

The primary aim of the current study was to determine whether metal ion levels could identify well- from poorly-functioning implants in patients after undergoing bilateral Articular Surface Replacement (ASR) Hip System. The secondary aim was to establish threshold values for Co and Cr that could be used to predict clinical problems in these patients.

MATERIALS AND METHODS

The study included 125 patients treated with bilateral ASR hip resurfacing (HRA) and 93 patients treated with bilateral ASR XL total hip arthroplasty (THA) at a mean follow-up of 7.1 years post-surgery. Patients were labelled as well- or poorly-functioning based on strict criteria. We calculated the Co and Cr safe upper ion limits (SUL) for ASR HRA and ASR XL THA separately and assessed these cutoffs ability to predict clinical problems.

RESULTS

In patients with bilateral ASR HRA, the well-functioning group had lower ions than the poorly-functioning. In ASR THA patients, there was no difference in blood Co or Cr levels between well- and poorly-functioning implant groups (p = 0.118 and p = 0.379, respectively). Both Co and Cr could effectively discriminate between well-functioning and poorly-functioning ASR HRA implants (p < 0.001 and p < 0.001, respectively), but not for ASR THA implants (p = 0.118 and p = 0.564, respectively). SULs of 4.0 ppb for Co and 4.0 ppb for Cr could differentiate between well- and poorly-functioning implants with high specificity.

CONCLUSIONS

Metal ion levels are a more reliable tool in MoM HRA than THA when discriminating well- from poorly-functioning implants in bilateral patients. For patients treated with bilateral ASR HRA, ion levels above 4.0 ppb are highly specific for the detection of clinical problems.

Hip resurfacing with a highly cross-linked polyethylene acetabular liner and a titanium nitride-coated femoral component

AIMS

This study evaluated a specific hip resurfacing system to determine the: (1) function and complications, (2) implant survivorship, (3) acetabular bone conservation and joint biomechanics and (4) osteolysis and polyethylene wear.

METHODS

I performed 234 resurfacing procedures (192 patients) using a two-piece titanium acetabular component with a 4 mm highly cross-linked polyethylene liner and a cementless titanium nitride-coated titanium femoral component. Function was assessed with Harris Hip, WOMAC, SF-12, and UCLA scores. Radiography and CT scans were used to evaluate bone retention, component position, joint biomechanics, and osteolysis. Retrieved polyethylene liners were analyzed for wear.

RESULTS

Median follow-up was 8 years and patients averaged 48 years of age at surgery. The mean Harris Hip Score was 96 and all scores improved significantly. Kaplan-Meier survivorship was 97%. The mean medial acetabular thickness was 9 mm postoperatively versus 14 mm preoperatively ( p = 0.019). Femoral bone conservation (head:neck ratio) was 1.36 postoperatively versus 1.42 preoperatively ( p = 0.02). There was no polyethylene wear through or osteolysis. Eight polyethylene retrievals had a mean wear of 0.05 mm/yr.

CONCLUSIONS

Resurfacing with a highly cross-linked polyethylene acetabular component and a titanium nitride-coated titanium cementless femoral component is a reliable and bone-conserving procedure at mid-term.

Outcomes after revision of metal on metal hip resurfacing to total arthroplasty using the direct anterior approach

BACKGROUND

Function after revision total hip arthroplasty (THA) in failed metal-on-metal (MoM) hip resurfacing arthroplasty (HRA) is variable, but post-operative complication rates are reportedly high. We hypothesized HRA conversion to THA using the direct anterior approach (DAA) would be associated with optimal outcome.

METHODS

Seventeen MoM-HRAs in 15 patients (seven males, eight females) were revised through the DAA. The mean age was 45 years (28-59 yrs). The most common indications for revision were aseptic loosening of the acetabular component or of the femoral component and femoral neck fracture. In 16 hips, a conversion to a ceramic-on-ceramic (CoC) (13 hips) or to a metal-on polyethylene (MOP) (2), or to a large-head MoM (1) THA was done. An isolated femoral revision was done in one hip.

RESULTS

After 6.7 ± 3 years, no hip had required a re-revision. The Postel-Merle d'Aubigne (PMA) functional score improved from 9 (4-14) to 16 (12-18) (p < 0.001). An intra-operative fracture of the greater trochanter (one hip) and dysesthesia of the lateral femoral cutaneous nerve (four hips) were reported. Mean serum chromium concentration decreased from 33.2 μg/L (11.8-62 μg/L) pre-operatively to 5.8 μg/L (0.4-35.5 μg/L) post-operatively (p < 0.001), and mean serum cobalt concentration decreased from 35.8 μg/L (6.3-85.5 μg/L) to 4.7 μg/L (0.26-25.7 μg/L) (p = 0.003).

CONCLUSION

Revision of failed MoM-HRA using the DAA resulted in an acceptable clinical outcome, no specific complication and no further surgery. A consistent decline in serum ion levels may be expected following HRA conversion to THA.

Interventions for Improving Hip Resurfacing Outcomes in Women: A High-Volume, Retrospective Study

BACKGROUND

Women seeking surgical intervention for their hip disorders will often find total hip arthroplasty (THA) presented as their only option. THA, when compared with hip resurfacing arthroplasty, removes substantially more bone-stock, limits range-of-motion, exhibits increased dislocation risk, and presents greater overall 10-year mortality rate. Despite these risks, most surgeons continue to select against women for hip resurfacing because registries notoriously report inferior survivorship when compared with men and THA.

METHODS

We investigated the reasons for why resurfacing arthroplasty devices survive poorly in women to develop interventions which might improve hip resurfacing outcomes in women. Using these findings, we developed a series of surgical interventions to treat the underlying issues. Herein, we compare 2 study groups: women who received hip resurfacings before (group 1) and after (group 2) these interventions.

RESULTS

Eight-year implant survivorship substantially improved from 89.6% for group 1 to 97.7% for group 2. Adverse wear-related failure, femoral component loosening, and acetabular component loosening were all significantly reduced in group 2, which we attribute to the implementation of our relative acetabular inclination limit guidelines, use of uncemented femoral fixation, and selection of the Tri-Spike acetabular component for supplemental fixation, respectively. Kaplan-Meier implant survivorship curves, grouped into 2-year time intervals, show that the disparity in failure rates between men and women is diminishing.

CONCLUSION

When experienced surgeons use refined and proper surgical technique, women show promise as excellent candidates for hip resurfacing as an alternative treatment for their debilitating hip conditions.

Blood Metal Ion Thresholds to Identify Patients with Metal-on-Metal Hip Implants at Risk of Adverse Reactions to Metal Debris: An External Multicenter Validation Study of Birmingham Hip Resurfacing and Corail-Pinnacle Implants

BACKGROUND

The authors of recent studies have reported newly devised implant-specific blood metal ion thresholds to predict adverse reactions to metal debris (ARMD) in patients who have undergone unilateral or bilateral metal-on-metal (MoM) hip arthroplasty. These thresholds were most effective for identifying patients at low risk of ARMD. We investigated whether these newly devised blood metal ion thresholds could effectively identify patients at risk of ARMD after MoM hip arthroplasty in an external cohort of patients.

METHODS

We performed a validation study involving 803 MoM hip arthroplasties (323 unilateral Birmingham Hip Resurfacing [BHR], 93 bilateral BHR, and 294 unilateral Corail-Pinnacle implants) performed in 710 patients at 3 European centers. All patients underwent whole-blood metal ion sampling, and were divided into 2 groups: those with ARMD (leading to revision or identified on imaging; n = 75) and those without ARMD (n = 635). Previously devised implant-specific blood metal ion thresholds (2.15 μg/L of cobalt for unilateral BHR; 5.5 μg/L for the maximum of either cobalt or chromium for bilateral BHR; and 3.57 μg/L of cobalt for unilateral Corail-Pinnacle implants) were applied to the validation cohort, and receiver operating characteristic curve analysis was used to establish the discriminatory characteristics of each threshold.

RESULTS

The area under the curve, sensitivity, specificity, and positive and negative predictive values for the ability of each implant-specific threshold to distinguish between patients with and without ARMD were, respectively, 89.4% (95% confidence interval [CI] = 82.8% to 96.0%), 78.9%, 86.7%, 44.1%, and 96.9% for unilateral BHR; 89.2% (CI = 81.3% to 97.1%), 70.6%, 86.8%, 54.5%, and 93.0% for bilateral BHR; and 76.9% (CI = 63.9% to 90.0%), 65.0%, 85.4%, 24.5%, and 97.1% for unilateral Corail-Pinnacle implants. Using the implant-specific thresholds, we missed 20 patients with ARMD (2.8% of the patients in this series). We missed more patients with ARMD when we used the fixed thresholds proposed by regulatory authorities: 35 (4.9%) when we used the U.K. threshold of 7 μg/L for both cobalt and chromium (p = 0.0003), 21 (3.0%) when we used the U.S. threshold of 3 μg/L for both cobalt and chromium (p = 1.0), and 46 (6.5%) when we used the U.S. threshold of 10 μg/L for both cobalt and chromium (p < 0.0001).

CONCLUSIONS

This external multicenter validation study confirmed that patients with blood metal ion levels below new implant-specific thresholds have a low risk of ARMD after MoM hip arthroplasty. Using these implant-specific thresholds, we missed fewer patients with ARMD compared with when the thresholds currently proposed by regulatory authorities were used. We therefore recommend using implant-specific blood metal ion thresholds when managing patients who have undergone MoM hip arthroplasty.

LEVEL OF EVIDENCE

Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Can blood metal ion levels be used to identify patients with bilateral Birmingham Hip Resurfacings who are at risk of adverse reactions to metal debris?

AIMS

We investigated whether blood metal ion levels could effectively identify patients with bilateral Birmingham Hip Resurfacing (BHR) implants who have adverse reactions to metal debris (ARMD).

PATIENTS AND METHODS

Metal ion levels in whole blood were measured in 185 patients with bilateral BHRs. Patients were divided into those with ARMD who either had undergone a revision for ARMD or had ARMD on imaging (n = 30), and those without ARMD (n = 155). Receiver operating characteristic analysis was used to determine the optimal thresholds of blood metal ion levels for identifying patients with ARMD.

RESULTS

The maximum level of cobalt or chromium ions in the blood was the parameter which produced the highest area under the curve (91.0%). The optimal threshold for distinguishing between patients with and without ARMD was 5.5 µg/l (83.3% sensitivity, 88.4% specificity, 58.1% positive and 96.5% negative predictive values). Similar results were obtained in a subgroup of 111 patients who all underwent cross-sectional imaging. Between 3.2% and 4.3% of patients with ARMD were missed if United Kingdom (7 µg/l) and United States (10 µg/l) authority thresholds were used respectively, compared with 2.7% if our implant specific threshold was used, though these differences did not reach statistical significance (p ≥ 0.248).

CONCLUSION

Patients with bilateral BHRs who have blood metal ion levels below our implant specific threshold were at low-risk of having ARMD. Cite this article: Bone Joint J 2016;98-B:1455-62.

Mid-Term Results and Predictors of Patient-Reported Outcomes of Birmingham Hip Resurfacing

BACKGROUND

Birmingham hip resurfacing (BHR) is the only Food and Drug Administration approved resurfacing option currently available in the United States. While adequate BHR outcomes are established, there is a paucity of US-based literature demonstrating factors critical to improve patient reported outcomes (PROs). This study answers: (1) What is the implant survivorship in a large US cohort? (2) Which preoperative factors result in higher PRO scores over 5 years postoperatively?

METHODS

A retrospective 541 hip single-surgeon cohort with mean of 6.2 years follow-up (range 5-8.1) was collected. Preoperative patient/implant variables, including postoperative radiographic acetabular inclination and femoral component position, clinical outcomes, and follow-up PRO questionnaire information were collected. Validated PROs included the Hip Disability and Osteoarthritis Outcome Score (HOOS), Veterans Rand-12, and University of California Los Angeles (UCLA) activity. PROs were modeled with ordinary least squares then used to create nomograms.

RESULTS

Average patient age was 53 years with 391 (72%) males. Seven hips were revised, resulting in an overall survival of 98.8% at 5 years. Predictive modeling identified preoperative variables (sex, body mass index, smoking, and comorbidity) that had statistically significant associations with HOOS pain (P = .049), HOOS activities of daily living (P = .017), UCLA activity (P < .001), and Veterans Rand-12 physical (P < .001) PROs at latest follow-up. Nomograms predicted follow-up PROs using preoperative patient-specific variables.

CONCLUSION

This study documents excellent survival of the largest reported single-center cohort of BHRs in the United States with a mean 6.2 years follow-up. Multivariate modeling shows male nonsmokers with low body mass index, and no comorbidities will have less hip pain, better function in daily life, higher activity, and better general physical health after BHR arthroplasty.

Revision rates for metal-on-metal hip resurfacing and metal-on-metal total hip arthroplasty - a systematic review

PURPOSE

To compare revision rates of metal-on-metal (MoM) hip resurfacing (HRS) and MoM total hip arthroplasty (THA), as well as the primary causes for revisions.

METHODS

The PubMed database was queried for potentially relevant articles addressing MoMTHA and MoMHRS, a total of 51 articles were included.

RESULTS

The review includes a total number of 5,399 MoMHRS and 3,244 THA prosthesis and the reasons for prosthesis failure were divided into 7 categories and the main causes discussed. The overall MoMTHA revision rate was 4.7% after 6.9 years. MoMHRS revision rate was 5.9% after 5.7 years. The odds ratio was 1.25 (1.03:1.53) 95% CI (p = 0.03) (MoMHRS vs. MoMTHA).The studies of hip prostheses were separated into 2 categories of short- and long-term (more or less than 5 years). Short-term revision rate for MoMTHA was 4.5% after 4.8 years, and for MoMHRS 4.0% after 4.2 years. The odds ratio was 1.09 (0.82:1.43) 95% CI (0 = 0.56) (MoMTHA vs. MoMHRS). Long-term revision rate for MoMTHA was 5.2% after 7.7 years and 8.2% after 7.6 years for MoMHRS. The odds ratio was 1.58 (1.53:1.96) 95% CI (p = 0.0001) (MoMHRS vs. MoMTHA).Revision causes were divided into 7 main categories. The most common cause for revision for both MoMTHA and MoMHRS was loosening 47.6% vs. 37.7%, fracture (MoMTHA 7.69%; MoMHRS 19.62%), metal reactions (MoMTHA 7.69%; MoMHRS 26.92%) infection (MoMTHA 12.08%; MoMHRS 6.54%), instability (MoMTHA 9.13%; MoMHRS 2.69%), manufacturer defect 6.73% for MoMTHA and nonreported for MoMHRS, and miscellaneous (MoMTHA 7.69%; MoMHRS 6.54%) was stated.

INTERPRETATION

The comparison of MoMHRS and MoMTHA revision rates showed no difference in the short term, however in the longer term, the revision rate of MoMHRS was significantly higher than for MoMTHA. The linear increase in revision rate of MoMHRS may indicate a progression in failure.

Predicting high blood metal ion concentrations following hip resurfacing

PURPOSE

To determine whether gender, femoral head size, acetabular inclination, and time since surgery predicted high blood metal ion concentrations following Birmingham Hip Resurfacing (BHR).

METHODS

BHR patients with unilateral bearings at one specialist centre with blood cobalt and chromium concentrations measured up to May 2013 were included. This comprised a mixed (at-risk) group including symptomatic patients and asymptomatic individuals with specific clinical and/or radiological findings. Blood sampling was at a mean of 7.5 years (range 1-15.4 years) postoperatively.

RESULTS

Of 319 patients (mean age 49.3 years; 53% male), blood metal ions greater than 7 µg/l were observed in 9% (n = 28). Blood metal ions were significantly higher in females (p&lt;0.001), femoral head sizes ≤48 mm (p&lt;0.01), and cup inclinations &gt;55° (p&lt;0.001). Linear regression demonstrated femoral head size was responsible for the highest proportion of variance in blood metal ions (cobalt p&lt;0.001, R2 = 8%; chromium p&lt;0.001, R2 = 11%). Analysis of femoral head size and inclination together demonstrated 36% of BHRs with head sizes of 38-44 mm and inclination &gt;55° had blood metal ions &gt;7 µg/l. BHR 10-year survival for this at-risk group was 91% (95% confidence intervals 86.0%-95.0%) with 30 hips revised.

CONCLUSIONS

If blood metal ions are used to screen hip resurfacing patients for adverse reactions to metal debris it is recommended those with small femoral head sizes (38-44 mm) and high acetabular inclinations (&gt;55°) are targeted. These findings require validation in other cohorts as they may not be applicable to all hip resurfacing devices given the differences in radial clearance, coverage arc, and metallurgy.

Hip Resurfacing Using Highly Cross-linked Polyethylene: Prospective Study Results at 8.5 Years

BACKGROUND

Hip resurfacing is an option to consider when treating younger, more active patients. Advantages over total hip arthroplasty include a more normal gait and a lower incidence of thigh pain.

METHODS

In this prospective study, 190 hip resurfacing procedures (164 participants) were performed using a cobalt-chromium femoral component and a cementless acetabular cup with a 3.8-mm highly cross-linked polyethylene acetabular liner.

RESULTS

The mean follow-up was 8.5 (range, 7-10) years. Two participants were lost to follow-up and 2 died. One participant underwent successful revision surgery for acetabular loosening. Four participants underwent successful revision to a total hip arthroplasty because of femoral neck fracture (2), femoral loosening, or infection. The Kaplan-Meier survivorship was 97%. Acetabular bone conservation was assessed using computed tomography by measuring the medial acetabular wall. The mean thickness was 9 mm. Femoral bone was well preserved with a mean head:neck ratio of 1.37. There were 4 (2%) osteolytic defects up to 0.9 cm(3) on computed tomography and no instances of impending polyethylene wear-through. Seven polyethylene retrievals had a measured wear rate of 0.05 mm/y.

CONCLUSION

Hip resurfacing using a highly cross-linked polyethylene acetabular component is a reliable procedure. Both femoral and acetabular bones are reasonably preserved compared with prior resurfacing methods. The low incidence of osteolysis and the low rate of wear found on retrievals suggest that many years of use in highly active patients is possible.

Prevalence of and Risk Factors for Hip Resurfacing Revision: A Cohort Study Into the Second Decade After the Operation

BACKGROUND

Most metal-on-metal hip resurfacing (MoMHR) designs have experienced high short-term failure rates because of pseudotumors. The impact of this complication into the second decade after the procedure is unknown. We investigated (1) the prevalence of, and risk factors for, all-cause and pseudotumor-related revision at up to 15 years following MoMHR and (2) whether risk factors were sex-specific.

METHODS

This single-center prospective cohort study included 1,429 MoMHRs (1216 patients; 40% female) implanted between 1999 and 2009. Patients were contacted in 2010 and 2012 as per national recommendations. Patients with symptoms related to the hip and/or suboptimal Oxford Hip Scores (≤41 of 48 points) underwent cross-sectional imaging and blood metal-ion sampling. Revision diagnoses were established using operative and histopathological findings. Multivariate Cox proportional hazard models were used to assess the association of predictor variables with the time to all-cause and pseudotumor-related revisions.

RESULTS

One hundred and eighty MoMHRs (12.6%) were revised for all causes, and 111 (7.8% of the series and 61.7 % of all revisions) were revised because of pseudotumor. Survival analysis showed the 15-year cumulative revision rate for all causes to be 19.5% (95% confidence interval [CI] = 16.2% to 23.2%) and the 15-year rate of revision due to pseudotumor to be 14.0% (95% CI = 11.0% to 17.7%). Small femoral head size (hazard ratio [HR] per 2 mm = 0.92, 95% CI = 0.88 to 0.97; p = 0.003) and certain implant designs (HR = 1.55 to 3.01; p ≤ 0.029) significantly increased the all-cause revision risk. Female sex (HR = 2.03, 95% CI = 1.19 to 3.44; p = 0.009) and young age (HR per year = 0.98, 95% CI = 0.96 to 1.00; p = 0.020) significantly increased the pseudotumor-related revision risk but not the all-cause revision risk. Risk factors for all-cause and pseudotumor-related revision were sex-specific. In females, small femoral head size (p = 0.014) increased the all-cause revision risk, and young age was the only predictor of pseudotumor-related revision (p = 0.019). In males, implant design was the only predictor of all-cause revision (p ≤ 0.015) and pseudotumor-related revision (p = 0.001).

CONCLUSIONS

The prevalence and rates of revision for all causes and pseudotumor were high at up to 15 years following MoMHR. Predictors of revision differed between all-cause and pseudotumor-related revisions and were sex-specific. These factors must be appropriately weighted when risk-stratifying patients with MoMHRs for surveillance.

LEVEL OF EVIDENCE

Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Medium-term results following large diameter metal-on-metal total hip arthroplasty: increasing failure after 6 years

PURPOSE

The main aim of our study is to report the medium-term survivorship of Birmingham Hip Resurfacing (BHR) cup and a large modular metal head (MMT) on an uncemented Freeman femoral stem. No results have been reported till date with these implants combinations.

METHODS

A total of 205 metal-on-metal total hip replacements (MoM THRs) were performed on 190 patients from October 2002 to November 2004. Prior to the Medicines and Healthcare Products Regulatory Agency (MHRA) guidelines, the patients were followed up at 3, 6 and 12 months postoperatively and annually thereafter. Following the MHRA alert in 2010, the patients were followed-up as per the MHRA guidelines.All statistical analyses were conducted using Stata 13.

RESULTS

At a mean follow-up of 10.5 years, a total of 42 out of 205 hips were revised for reasons related to ALTR. The failure rates increased significantly over time (7% at 6 years and 29% at 10-year follow-up). The analysis showed no statistically significant association to age, gender, side, BMI or component size or position (p&lt;0.05). Blood metal ions showed a poor discriminant ability to separate failed from well-functioning MoM hip replacements.

CONCLUSIONS

Large head MoM BHR on an uncemented stem has extremely high failure rate. The authors do not recommend the use of large head MoM articulation in total hip arthroplasty in the wake of this report and similar findings across the world. Continued surveillance of these implants is required as the failure rates increase with time.

Prevalence of Failure due to Adverse Reaction to Metal Debris in Modern, Medium and Large Diameter Metal-on-Metal Hip Replacements--The Effect of Novel Screening Methods: Systematic Review and Metaregression Analysis

Metal-on-metal (MoM) hip replacements were used for almost a decade before adverse reactions to metal debris (ARMD) were found to be a true clinical problem. Currently, there is a paucity of evidence regarding the usefulness of systematic screening for ARMD. We implemented a systematic review and meta-analysis to establish the prevalence of revision confirmed ARMD stratified by the use of different screening protocols in patients with MoM hip replacements. Five levels of screening were identified: no screening (level 0), targeted blood metal ion measurement and/or cross-sectional imaging (level 1), metal ion measurement without imaging (level 2), metal ion measurement with targeted imaging (level 3) and comprehensive screening (both metal ions and imaging for all; level 4). 122 studies meeting our eligibility criteria were included in analysis. These studies included 144 study arms: 100 study arms with hip resurfacings, 33 study arms with large-diameter MoM total hip replacements (THR), and 11 study arms with medium-diameter MoM THRs. For hip resurfacing, the lowest prevalence of ARMD was seen with level 0 screening (pooled prevalence 0.13%) and the highest with level 4 screening (pooled prevalace 9.49%). Pooled prevalence of ARMD with level 0 screening was 0.29% and with level 4 screening 21.3% in the large-diameter MoM THR group. In metaregression analysis of hip resurfacings, level 4 screening was superior with regard to prevalence of ARMD when compared with other levels. In the large diameter THR group level 4 screening was superior to screening 0,2 and 3. These outcomes were irrespective of follow-up time or study publication year. With hip resurfacings, routine cross-sectional imaging regardless of clinical findings is advisable. It is clear, however, that targeted metal ion measurement and/or imaging is not sufficient in the screening for ARMD in any implant concepts. However, economic aspects should be weighed when choosing the preferred screening level.

Conversion of a failed hip resurfacing arthroplasty to total hip arthroplasty: pearls and pitfalls

Surface replacement arthroplasty (SRA) remains a viable alternative to total hip arthroplasty (THA) in appropriately selected, active adults with degenerative hip disease. However, orthopedic surgeons are facing a number of scenarios where revision of one or both components of an SRA is indicated. Indications for revision vary and impact the potential outcomes of conversion of a SRA to THA. While clinical outcomes are generally favorable, a growing body of data illustrates patients who undergo conversion of a SRA to THA to be at increased risk of requiring a repeat revision surgery and experiencing functional outcomes inferior to that of a primary THA. The results of patients undergoing conversion of a SRA to THA highlight the need for careful patient selection, thorough preoperative counseling, and technical precision when performing a SRA. Furthermore, a systematic approach to the failed SRA is necessary to ensure optimal clinical results.

Frequent femoral neck osteolysis with Birmingham mid-head resection resurfacing arthroplasty in young patients

BACKGROUND

Mid-head resection total hip resurfacing arthroplasty was promoted as an alternative to traditional total hip resurfacing for patients with poor femoral head bone quality or abnormal femoral head morphology, because those patients are at high risk of failure with traditional total hip resurfacing. It is a large-headed metal-on-metal device that uses a short, bone-conserving stem. Good performance of the implant has been reported at short-term followup, but no information on the implant performance in the mid- or long-term is available.

QUESTIONS/PURPOSES

In this study, we report (1) on the mid-term implant survivorship and hip scores in a single nondesigner surgeon series. Because of the occurrence of femoral neck osteolysis and pseudotumor in a subgroup of patients, we also investigated the following: (2) Were there any preoperative parameters that are associated with osteolysis? (3) Could we differentiate the osteolysis group from the others on the basis of implant component sizes, positions, and radiologic parameters? (4) Could we differentiate the osteolysis group from the others on the basis of metal ion levels?

METHODS

Between 2006 and 2011, one surgeon performed a total of 49 Birmingham Mid-head Resection total hip resurfacing arthroplasties in 47 patients. The general indications for this procedure were young patients who were considered suitable for hip resurfacing arthroplasty but had avascular necrosis, large cysts, or severe deformity of the femoral head. Clinical followup including Oxford Hip Score (OHS) and UCLA hip scores were available preoperatively and at a mean of 6 years (range, 3-8 years) on all patients (100%), radiographic followup on 45 of 47 (96%), MRIs on 18 (38%), and metal ion levels on 37 (79%). Mean age at surgery was 50 years. Spearman's correlation was used to test the association between femoral neck osteolysis and preoperative parameters, implant component sizes and positions, and blood metal ion levels.

RESULTS

We found 100% survival. Patients' median OHS was 46 of 48 (range, 35-48) and UCLA 8 of 10 (range, 4-10). However, 16% of the hips (seven of 45) demonstrated osteolysis in the femoral neck. Of the preoperative parameters, the osteolysis was associated with low weight (r = -0.337, p = 0.031) and to a lesser degree with female sex (r = 0.275, p = 0.067). Radiologically, the osteolysis was strongly associated with the presence of a pseudotumor on MRI (r = 0.663, p = 0.004). We could not differentiate the osteolysis group from the rest of the cohort on the basis of the implant sizes or radiographic implant component positions. The cohort's median whole blood cobalt was 1.77 ppb (range, 0.18-10.27 ppb) and chromium 1.88 ppb (range 0.36-10.09 ppb). There was no difference in the metal ion levels between the osteolysis group and the rest of the cohort.

CONCLUSIONS

The high rate of silently developing femoral neck osteolysis associated with this implant is concerning and is expected to cause a high rate of failure at longer followup. We have instituted a program of annual clinical and radiologic followup for this group of patients. We have stopped implanting this device and recommend against its use.

LEVEL OF EVIDENCE

Level IV, therapeutic study.

Are There Long-term Benefits to Cementing the Metaphyseal Stem in Hip Resurfacing?

BACKGROUND

Cementing the metaphyseal stem during hip resurfacing surgery improves the initial fixation of the femoral component. However, there may be long-term detrimental effects such as stress shielding or an increased risk of thermal necrosis associated with this technique.

QUESTIONS/PURPOSES

We compared (1) long-term survivorship free from radiographic femoral failure, (2) validated pain scores, and (3) radiographic evidence of component fixation between hips resurfaced with a cemented metaphyseal stem and hips resurfaced with the metaphyseal stem left uncemented.

METHODS

We retrospectively selected all the patients who had undergone bilateral hip resurfacing with an uncemented metaphyseal stem on one side, a cemented metaphyseal stem on the other side, and had both surgeries performed between July 1998 and February 2005. Forty-three patients matched these inclusion criteria. During that period, the indications for cementing the stem evolved in the practice of the senior author (HCA), passing through four phases; initially, only hips with large femoral defects had a cemented stem, then all stems were cemented, then all stems were left uncemented. Finally, stems were cemented for patients receiving small femoral components (< 48 mm) or having large femoral defects (or both). Of the 43 cemented stems, two, 13, 0, and 28 came from each of those four periods. All 43 patients had complete followup at a minimum of 9 years (mean, 143 ± 21 months for the uncemented stems; and 135 ± 22 months for the cemented stems; p = 0.088). Survivorship analyses were performed with Kaplan-Meier and Cox proportional hazards ratios using radiographic failure of the femoral component as the endpoint. Pain was assessed with University of California Los Angeles (UCLA) pain scores, and radiographic femoral failure was defined as complete radiolucency around the metaphyseal stem or gross migration of the femoral component.

RESULTS

There were four failures of the femoral component in the press-fit stem group while the cemented stem group had no femoral failures (p = 0.0471). With the numbers available, we found no differences between the two groups regarding pain relief or radiographic appearance other than in patients whose components developed loosening.

CONCLUSIONS

Cementing the metaphyseal stem improves long-term implant survival and does not alter long-term pain relief or the radiographic appearance of the proximal femur as had been a concern based on the results of finite element studies. We believe that patients with small component sizes and large femoral head defects have more to gain from the use of this technique which adds surface area for fixation, and there is no clinical downside to cementing the stem in patients with large component sizes.

LEVEL OF EVIDENCE

Level III, therapeutic study.

Do Complication Rates Differ by Gender After Metal-on-metal Hip Resurfacing Arthroplasty? A Systematic Review

BACKGROUND

Although metal-on-metal (MoM) bearing surfaces provide low rates of volumetric wear and increased stability, evidence suggests that certain MoM hip arthroplasties have high rates of complication and failure. Some evidence indicates that women have higher rates of failure compared with men; however, the orthopaedic literature as a whole has poorly reported such complications stratified by gender.

QUESTIONS/PURPOSES

This systematic review aimed to: (1) compare the rate of adverse local tissue reaction (ALTR); (2) dislocation; (3) aseptic loosening; and (4) revision between men and women undergoing primary MoM hip resurfacing arthroplasty (HRA).

METHODS

Systematic MEDLINE and EMBASE searches identified all level I to III articles published in peer-reviewed journals, reporting on the outcomes of interest, for MoM HRA. Articles were limited to those with 2-year followup that reported outcomes by gender. Ten articles met inclusion criteria. Study quality was evaluated using the Modified Coleman Methodology Score; the overall quality was poor. Heterogeneity and bias were analyzed using a Mantel-Haenszel statistical method.

RESULTS

Women demonstrated an increased odds of developing ALTR (odds ratio [OR], 5.70 [2.71-11.98]; p<0.001), dislocation (OR, 3.04 [1.2-7.5], p=0.02), aseptic loosening (OR, 3.18 [2.21-4.58], p<0.001), and revision (OR, 2.50 [2.25-2.78], p<0.001) after primary MoM HRA.

CONCLUSIONS

A systematic review of the currently available literature reveals a higher rate of complications (ALTR, dislocation, aseptic loosening, and revision) after MoM HRA in women compared with men. Although femoral head size has been frequently implicated as a prime factor in the higher rate of complication in women, further research is necessary to specifically probe this relationship. Retrospective studies of data available (eg, registry data) should be undertaken, and moving forward studies should report outcomes by gender (particularly complications).

LEVEL OF EVIDENCE

Level III, therapeutic study.

Patient satisfaction and clinical results at a mean eight years following BHR arthroplasty: results from a district general hospital

We present the clinical and radiological results of a prospective study of a consecutive series of patients treated with the Birmingham Hip Resurfacing (BHR) prosthesis between 1999 and 2006 and followed for six to 12 years. Patients were reviewed preoperatively and six, 12, 26 and 52 weeks postoperatively and annually thereafter. They were assessed clinically and radiographically and the Merle d'Aubigne Postel and Oxford Hip scores were calculated at each visit. A SF-36 form assessed general health. Patient satisfaction was assessed by a Visual Analogue Score. Kaplan Meier survival analysis was performed.One hundred and seven patients (109 hips) were included (45 males, 62 females). Median age was 44 years. Mean follow-up was 97.4 months. Median preoperative Merle d'Aubigne Postel and Oxford hip scores were 10 (3-14) and 42 (26-55) respectively. Median SF36 score was 29 (0-65) and patients rated their level of pain as 7.7 on a scale of 0-10 (10 being the worst score). At final follow-up, median MDP and OHS scores were 17 (16-18) and 25 (12-46). Median SF36 score was 72 (27-97). Seven revisions were performed in six females and one male patient. Survival was 96.2% with revision for any reason as the end point. No revisions were performed in the group with hip dysplasia.The BHR prosthesis provides pain relief, high levels of patient satisfaction and improvement of function and well being in the medium-term. Failures occurred primarily in the female group.

Hip resurfacing arthroplasty in treatment of avascular necrosis of the femoral head

Background

Hip resurfacing is a conservative type of total hip arthroplasty but its use is controversial, especially in patients with osteonecrosis. The aim of this study was analysis of the clinical and radiographic outcomes of hip resurfacing in patients with osteonecrosis.

Material/Methods

Between 2007 and 2008, 30 hip resurfacing arthroplasties were performed due to osteoarthritis secondary to avascular necrosis of femoral head staged as Ficat III and IV.

Patients were qualified to resurfacing arthroplasty when the extent of avascular necrosis using Kerboul’s method was <200° and the angle between avascular necrosis and head-neck junction was >20°. All patients were evaluated clinically and radiologically before and 60 months after the operation.

Results

The mean Harris Hip Score (HHS) score increased from 47.8 to 94.25 (p<0.05). Physical activity level (University of California, Los Angeles activity score – UCLA activity score) improved from 3.7 to 7.55 (p<0.05). No implant migration was observed.

Conclusions

Management of osteonecrosis of the hip with resurfacing arthroplasty seems to be effective in strictly-selected patients.

Return to sporting activity after Birmingham hip resurfacing arthroplasty: Mid term results

BACKGROUND

Hip resurfacing arthroplasty (HRA) is primarily indicated for young, active patients with disabling coxarthrosis who wish to remain active and return to sports after surgery. Relatively few prospective studies have assessed return to sporting activity and impact of gender and age on this.

MATERIALS AND METHODS

Seventy-nine consecutive patients treated with HRA were included. Patients were reviewed clinically and radiologically. Function was assessed using the modified University of California Los Angeles (UCLA) activity score. The Oxford, Harris and WOMAC hip scores were calculated.

RESULTS

Average age at the time of surgery was 54.9 years (range 34.5-73.6 years). Average preoperative and postoperative UCLA scores were 4 and 7.6 respectively. Patients were involved in 2 (0-4) sporting activities preoperatively and 2 (0-5) postoperatively. Preoperative and postoperative Oxford Hip Scores, Harris Hip Score and WOMAC scores were 40, 46 and 51 and 16, 94 and 3 respectively (P < 0.0001). Patients returned to sports at an average of 3 months postoperatively.

CONCLUSION

Patients were able to return to sports by 3 months and perform the same number of activities at preoperative intensity. Activity levels are maintained up to the medium term with few complications.

Clinical results of the conserve plus metal on metal hip resurfacing: an independent series

The purpose of the present study was to report the clinical and radiographic results of an independent series of the Conserve Plus hip resurfacing. Five hundred forty-eight consecutive hip resurfacings were performed using the Conserve Plus prosthesis in 458 patients (350 males) with a mean age of 48.3 years (range 19 to 66). No patients were lost to follow-up. At a mean follow-up of 6.6 years (3.9 to 11.9) thirty (5.4%) hips required conversion to a total hip arthroplasty (THA) (20 males, 10 females, mean age=48.3±7.3 years). Five-year survival with as revision endpoint was 94.5% (95% CI: 93.5% to 95.5%). This study confirms the good clinical results previously reported with the Conserve Plus hip resurfacing device.

Metal ion levels and revision rates in metal-on-metal hip resurfacing arthroplasty: a comparative study

Metal-on-metal (MoM) bearings in hip surgery are related to increased blood levels of metal ions. The nature of the relationship between ion levels and failure is still not fully understood. This study compares three cohorts of patients, 120 patients in each cohort, treated with a hip resurfacing arthroplasty, grouped by brand and diameter of femoral component on average four years postoperatively: Birmingham Hip Resurfacing ≥50 mm, Durom resurfacing ≥50 mm and Durom resurfacing <50 mm. The median blood ion levels of cobalt and chromium were significantly lower in the cohort with the large Durom resurfacing than the other two cohorts (P<0.05). The large BHR and large Durom HRA had revision rates of 3.3%. The small Durom HRA had a revision rate of 8.3%. Elevated blood ion levels can indicate a failing MoM bearing. The large BHR and large Durom HRA have similar revision rates yet the large Durom HRA had significantly lower metal ion levels. When similar ion levels were reported for BHR and small Durom the latter had significantly higher revision rates. This suggests ion levels do not absolutely predict the rate of HRA failure. Since MoM generation of metal ions is not the sole reason of failure, regular clinical and radiographic follow-up should also be in place for patients with these joints.

Outcomes of a metal-on-metal total hip replacement system

INTRODUCTION

High short-term failure rates have been reported for a variety of metal-on-metal (MoM) total hip replacements (THRs) owing to adverse reactions to metal debris (ARMD). This has led to the withdrawal of certain poorly performing THRs. This study analysed the outcomes of a MoM THR system.

METHODS

Between 2004 and 2010, 578 uncemented MoM THRs (511 patients, mean age: 60.0 years) were implanted at one specialist centre. The THR system used consisted of the Corail(®) stem, Pinnacle(®) cup, Ultamet(®) liner and Articul/eze(®) femoral head (all DePuy, Leeds, UK). All patients were recalled for clinical review with imaging performed as necessary.

RESULTS

The mean follow-up duration was 5.0 years (range: 1.0-9.1 years). Overall, 39 hips (6.7%) in 38 patients (all 36 mm femoral head size) underwent revision at a mean time of 3.5 years (range: 0.01-8.3 years) from the index THR with 30 revisions (77%) performed in women. The cumulative eight-year survival rate for all THRs was 88.9% (95% confidence interval [CI]: 78.5-93.4%), with no difference (p=0.053) between male (95.2%, 95% CI: 84.2-98.7%) and female patients (85.3%, 95% CI: 70.2-92.1%) at eight years. Seventeen revisions (44%) were performed for ARMD. There was no significant difference in absolute postoperative Oxford hip scores between men and women (p=0.608). The mean acetabular inclination in unrevised THRs was 44.0°. Forty-seven non-revised THRs (8.7%) had blood metal ion concentrations above recommended thresholds (seven had periprosthetic effusions).

CONCLUSIONS

Although this MoM THR system has not failed as dramatically as other similar designs, we recommend against continued use and advise regular clinical surveillance to identify ARMD early.

Metal-on-metal hip resurfacing compared with total hip arthroplasty: two to five year outcomes in men younger than sixty five years

PURPOSE

There are limited studies examining the long-term survivorship for the current generation of metal-on-metal hip resurfacing (MOMHR) implants in the young male population, and fewer studies have been published on prospectively collected outcomes data for total hip resurfacing in the USA. The purpose of this study was to demonstrate the efficacy of MOMHR in comparison with total hip arthroplasty (THA) using validated outcome measures, survivorship and complication rates.

METHODS

The study prospectively followed 136 implants in 123 male patients <65 years, all with a primary diagnosis of osteoarthritis and similar comorbidities as determined by the American Society of Anesthesiologists (ASA) score. A single-surgeon cohort of 89 MOMHRs was compared with a similar cohort of 47 THAs. Outcomes were prospectively assessed with the Short-Form Health Survey of 12 questions (SF-12) and Western Ontario and McMaster Universities (WOMAC) questionnaires pre- and postoperatively at yearly intervals. Minimum follow-up was two years, and average follow-up was 3.9 years.

RESULTS

Diagnosis, body mass index (BMI), American Association of Anesthesiologists (ASA) and pre-operative pain and function scores were not significantly different between groups. There was no difference in SF-12 scores postoperatively. At one and two years postoperatively, the MOMHR group had better WOMAC scores than the THA group, but no difference was seen at three to five years postoperatively. There were no revisions in either group over the study period.

CONCLUSIONS

This study demonstrated good results for hip resurfacing in men <65 years five years postoperatively and similar function to THA patients.

Hip resurfacing arthroplasty at a non-specialist centre

INTRODUCTION

Few studies have reported the outcome of hip resurfacing arthroplasty (HRA) with respect to implant characteristics from non-specialist centres. We report the survival, clinical and radiological outcomes of a single surgeon series of HRA with an average follow-up duration of five years.

METHODS

All consecutive HRAs performed by a single surgeon between 2003 and 2011 at a district general hospital were retrospectively examined clinically and radiologically.

RESULTS

A total of 85 patients underwent 109 HRAs (58 male [53.2%] and 51 female patients [46.8%]) with a mean follow-up period of 62 months (range: 12-102 months). The median age was 57 years (range: 25-75 years). The mean acetabular and femoral head component sizes were 54 mm (range: 48-64 mm) and 48 mm (range: 42-58 mm) respectively with a mean acetabular inclination angle of 42.9° (range: 20-75°). The survival rate was 95% with five revisions due to aseptic loosening (n=3) and fracture (n=2): these were predominantly for female patients (n=4), with significantly smaller mean acetabular (51 mm, p=0.04) and femoral (44 mm, p=0.02) implant sizes. Furthermore, they had a higher mean acetabular inclination angle of 48.1° (p=0.74). The mean Oxford hip score was 43.8 (range: 25-48) and the mean University of California Los Angeles (UCLA) activity score was 6.8 (range: 3-10). Radiological findings included heterotopic ossification in 13 (11.9%), radiolucent lines in 6 (5.5%), femoral neck thinning in 2 (1.8%) and femoral neck notching in 5 patients (4.6%).

CONCLUSIONS

We have shown that HRA at a non-specialist centre has short to medium-term outcomes comparable with those at specialist centres. HRA therefore remains a viable option although vigilance is required in case selection and follow-up according to national guidance.

One-component revision of failed hip resurfacing from adverse reaction to metal wear debris

This study assessed the results of 90 one-component revisions for failed hip resurfacing due to adverse reaction to metal wear debris (76 acetabular, 14 femoral). Patients with a femoral head size 40-45 mm (n=33) received a two-piece titanium meshed shell with a cross-linked polyethylene liner and patients with femoral head size 46-54 mm (n=43) received metal-on-metal components. Patients with femoral head size>45 mm who wished a metal-polyethylene bearing received a dual mobility femoral prosthesis. The mean follow-up was 61 months and the procedure was successful in 97% of the patients. Three failures required re-revision; there was one deep infection. There were no dislocations. One-component revision is a reasonable alternative to revision to total hip arthroplasty.

Survival and functional outcome of the Birmingham Hip Resurfacing system in patients aged 65 and older at up to ten years of follow-up

PURPOSE

Limited evidence exists regarding the outcomes of hip resurfacing in elderly patients. The primary study aims were to determine the survival and functional outcome following Birmingham Hip Resurfacing (BHR) in patients ≥65 years at up to ten years of follow-up. Secondary aims were to explore factors affecting survival and functional outcome.

METHODS

Between 1997 and 2012, data were prospectively collected on 180 BHR (162 patients; mean age 69.2 years; 62 % male) implanted by one designing surgeon. Mean follow-up was six (range one to 14.4) years with no loss to follow-up. Outcomes of interest were implant survival, functional outcome [Oxford Hip Score (OHS)] and radiological evidence of implant failure.

RESULTS

Three hips were revised, giving an overall cumulative survival of 96.4 % [95 % confidence interval (CI) 90.3-100] at ten years. Survival of 111 male BHR was 98.9 % (95 % CI 94.8-100) at ten years (one revision) compared with 91.9 % (95 % CI 77.0-100) in 69 female BHR (two revisions). Survival was affected by age (p = 0.014) and femoral head size (p = 0.024) but not by gender (p = 0.079). Median pre-operative OHS was 50.0 % [interquartile range (IQR) 37.5-68.8], improving to 4.4 % (IQR 0-10.4) postoperatively. Men had significantly better postoperative OHSs compared with women (median male OHS 2.1 % versus 6.3 % female OHS; p = 0.021).

CONCLUSIONS

Good survival and functional outcomes were achieved with the BHR at ten years in men and women ≥65 years. Despite registry findings to the contrary, age alone should not be a contraindication for hip resurfacing in centres with expertise in this procedure.

Impact of implant size on cement filling in hip resurfacing arthroplasty

Larger proportions of cement within femoral resurfacing implants might result in thermal bone necrosis. We postulate that smaller components are filled with proportionally more cement, causing an elevated failure rate. A total of 19 femoral heads were fitted with polymeric replicas of ReCap (Biomet) resurfacing components fixed with low-viscosity cement. Two specimens were used for each even size between 40 and 56 mm and one for size 58 mm. All specimens were imaged with computed tomography, and the cement thickness and bone density were analyzed. The average cement mantle thickness was 2.63 mm and was not correlated with the implant size. However, specimen with low bone density had thicker cement mantles regardless of size. The average filling index was 36.65% and was correlated to both implant size and bone density. Smaller implants and specimens with lower bone density contained proportionally more cement than larger implants. According to a linear regression model, bone density but not implant size influenced cement thickness. However, both implant size and bone density had a significant impact on the filling index. Large proportions of cement within the resurfacing head have the potential to generate thermal bone necrosis and implant failure. When considering hip resurfacing in patients with a small femoral head and/or osteoporotic bone, extra care should be taken to avoid thermal bone necrosis, and alternative cementing techniques or even cementless implants should be considered. This study should help delimiting the indications for hip resurfacing and to choose an optimal cementing technique taking implant size into account.

Cost-utility of metal-on-metal hip resurfacing compared to conventional total hip replacement in young active patients with osteoarthritis

BACKGROUND

Metal-on-metal hip resurfacing arthroplasty (MoM HRA) has emerged as an alternative to total hip arthroplasty (THA) for younger active patients with osteoarthritis (OA). Birmingham hip resurfacing is the most common MoM HRA in Alberta, and is therefore compared with conventional THA.

OBJECTIVE

The objective of this study was to estimate the expected cost-utility of MoM HRA versus THA, in younger patients with OA, using a decision analytic model with a 15-year time horizon.

METHODS

A probabilistic Markov decision analytic model was constructed to estimate the expected cost per quality-adjusted life-year (QALY) of MoM HRA versus THA from a health care payer perspective. The base case considered patients with OA aged 50 years; men comprised 65.9% of the cohort. Sensitivity analyses evaluated cohort age, utility values, failure probabilities, and treatment costs. Data were derived from the Hip Improvement Project and the Hip and Knee Replacement Pilot databases in Alberta, the 2010 National Joint Replacement Registry of the Australian Orthopaedic Association, and the literature.

RESULTS

In the base case, THA was dominated by MoM HRA (incremental mean costs of -$583 and incremental mean QALYs of 0.079). In subgroup analyses, THA remained dominated when cohort age was 40 years instead of 50 years or when only men were assessed. THA dominated when the cohort age was 60 years or when only women were assessed. Results were sensitive to utilities, surgery costs, and MoM HRA revision and conversion probabilities. At a willingness-to-pay of Can $50,000/QALY, there was a 58% probability that MoM HRA is cost-effective.

CONCLUSIONS

The results show that, on average, MoM HRA was preferred to THA for younger and male patients, but THA is still a reasonable option if the patient or clinician prefers given the small absolute differences between the options and the confidence ellipses around the cost-effectiveness estimates.

The outcome of the Birmingham Hip Resurfacing in patients aged < 50 years up to 14 years post-operatively

We report the long-term survival and functional outcome of the Birmingham Hip Resurfacing (BHR) in patients aged < 50 years at operation, and explore the factors affecting survival. Between 1997 and 2006, a total of 447 BHRs were implanted in 393 patients (mean age 41.5 years (14.9 to 49.9)) by one designing surgeon. The mean follow-up was 10.1 years (5.2 to 14.7), with no loss to follow-up. In all, 16 hips (3.6%) in 15 patients were revised, giving an overall cumulative survival of 96.3% (95% confidence interval (CI) 93.7 to 98.3) at ten years and 94.1% (95% CI 84.9 to 97.3) at 14 years. Using aseptic revision as the endpoint, the survival for men with primary osteoarthritis (n = 195) was 100% (95% CI 100 to 100) at both ten years and 14 years, and in women with primary osteoarthritis (n = 109) it was 96.1% (95% CI 90.1 to 99.9) at ten years and 91.2% (95% CI 68.6 to 98.7) at 14 years. Female gender (p = 0.047) and decreasing femoral head size (p = 0.044) were significantly associated with an increased risk of revision. The median Oxford hip score (OHS, modified as a percentage with 100% indicating worst outcome) at last follow-up was 4.2% (46 of 48; interquartile range (IQR) 0% to 24%) and the median University of California, Los Angeles (UCLA) score was 6.0 (IQR 5 to 8). Men had significantly better OHS (p = 0.02) and UCLA scores (p = 0.01) than women. The BHR provides excellent survival and functional results in men into the second decade, with good results achieved in appropriately selected women.

Cite this article: Bone Joint J 2013;95-B:1172–7.

The Canadian Arthroplasty Society’s experience with hip resurfacing arthroplasty

The purpose of this study was twofold: first, to determine whether the five-year results of hip resurfacing arthroplasty (HRA) in Canada justified the continued use of HRA; and second, to identify whether greater refinement of patient selection was warranted.

This was a retrospective cohort study that involved a review of 2773 HRAs performed between January 2001 and December 2008 at 11 Canadian centres. Cox’s proportional hazards models were used to analyse the predictors of failure of HRA. Kaplan–Meier survival analysis was performed to predict the cumulative survival rate at five years. The factors analysed included age, gender, body mass index, pre-operative hip pathology, surgeon’s experience, surgical approach, implant sizes and implant types. The most common modes of failure were also analysed.

The 2773 HRAs were undertaken in 2450 patients: 2127 in men and 646 in women. The mean age at operation was 50.5 years (sd 8.72; 18 to 82) and mean follow-up was 3.4 years (sd 2.1; 2.0 to 10.1). At the last follow-up a total of 101 HRAs (3.6%) required revision. Using revision for all causes of failure as the endpoint, Kaplan–Meier survival analysis showed a cumulative survival of 96.4% (95% confidence interval (CI) 96.1 to 96.9) at five years. With regard to gender, the five-year overall survival was 97.4% in men (95% CI 97.1 to 97.7) and 93.6% in women (95% CI 92.6 to 94.6). Female gender, smaller femoral components, specific implant types and a diagnosis of childhood hip problems were associated with higher rates of failure. The most common cause of failure was fracture of the femoral neck, followed by loosening of the femoral component.

The failure rates of HRA at five years justify the ongoing use of this technique in men. Female gender is an independent predictor of failure, and a higher failure rate at five years in women leads the authors to recommend this technique only in exceptional circumstances for women.

Cite this article: Bone Joint J 2013;95-B:1044–50.

Patterns of changes in femoral bone mineral density up to five years after hip resurfacing

This is a prospective study of 26 patients (29 hips) on the patterns of change in the Bone Mineral Density (BMD) in various zones of the femoral neck and proximal femur five years after hip resurfacing. We have found that BMD continues to positively change up to five years after hip resurfacing. This was observed primarily in the trochanteric and superior neck regions. In both these regions BMD had decreased by up to 10% at six-weeks and three-months after surgery and then had recovered to preoperative level by one year. A regression analysis to assess the influence of age, gender, BMI, preoperative BMD, component size and orientation revealed that the best predictor of change in BMD at five years in the trochanteric area was acetabular component inclination.

The 2012 Otto Aufranc Award: The interpretation of metal ion levels in unilateral and bilateral hip resurfacing

BACKGROUND

The interpretation of metal ion concentrations and their role in clinical management of patients with metal-on-metal implants is still controversial.

QUESTIONS/PURPOSES

We questioned whether patients undergoing hip resurfacing with no clinical problems could be differentiated from those with clinical (pain, loss of function) and/or radiographic (component malpositioning, migration, bone loss), problems based on metal ion levels, and if there was a threshold metal level that predicted the need for clinical intervention. Furthermore, we asked if patient and implant factors differed between these functional groups.

METHODS

We retrospectively identified 453 unilateral and 139 bilateral patients with ion measurements at minimum followup of 12 months (mean, 4.3 years; range, 1-12.9 years). Patients were designated as well functioning or poorly functioning based on strict criteria. The acceptable upper levels within the well-functioning group were determined from the 75th percentile plus 1.5× interquartile range. The sensitivity and specificity of these levels to predict clinical problems were calculated.

RESULTS

Well-functioning group ions were lower than the poorly functioning group ion levels. The acceptable upper levels were: chromium (Cr) 4.6 μg/L, cobalt (Co) 4.0 μg/L unilateral and Cr 7.4 μg/L, Co 5.0 μg/L bilateral. The specificity of these levels in predicting poor function was high (95%) and sensitivity was low (25%). There were more males in the well-functioning group and more females and smaller femoral components in the poorly functioning group.

CONCLUSIONS

Metal levels higher than these proposed safe upper limits can predict problems with metal-on-metal resurfacings and are important parameters in the management of at-risk patients.

LEVEL OF EVIDENCE

Level II, diagnostic study. See Guidelines for Authors for a complete description of levels of evidence.

Socket position determines hip resurfacing 10-year survivorship

BACKGROUND

Modern metal-on-metal hip resurfacing arthroplasty designs have been used for over a decade. Risk factors for short-term failure include small component size, large femoral head defects, low body mass index, older age, high level of sporting activity, and component design, and it is established there is a surgeon learning curve. Owing to failures with early surgical techniques, we developed a second-generation technique to address those failures. However, it is unclear whether the techniques affected the long-term risk factors.

QUESTIONS/PURPOSES

We (1) determined survivorship for hips implanted with the second-generation cementing technique; (2) identified the risk factors for failure in these patients; and (3) determined the effect of the dominant risk factors on the observed modes of failure.

METHODS

We retrospectively reviewed the first 200 hips (178 patients) implanted using our second-generation surgical technique, which consisted of improvements in cleaning and drying the femoral head before and during cement application. There were 129 men and 49 women. Component orientation and contact patch to rim distance were measured. We recorded the following modes of failure: femoral neck fracture, femoral component loosening, acetabular component loosening, wear, dislocation, and sepsis. The minimum followup was 25 months (mean, 106.5 months; range, 25-138 months).

RESULTS

Twelve hips were revised. Kaplan-Meier survivorship was 98.0% at 5 years and 94.3% at 10 years. The only variable associated with revision was acetabular component position. Contact patch to rim distance was lower in hips that dislocated, were revised for wear, or were revised for acetabular loosening. The dominant modes of failure were related to component wear or acetabular component loosening.

CONCLUSIONS

Acetabular component orientation, a factor within the surgeon's control, determines the long-term success of our current hip resurfacing techniques. Current techniques have changed the modes of failure from aseptic femoral failure to wear or loosening of the acetabular component.

LEVEL OF EVIDENCE

Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.