Socket position determines hip resurfacing 10-year survivorship

Hip resurfacing arthroplasty as an alternative to total hip arthroplasty in patients aged under 40 years

Aims

The aims of the study were to report for a cohort aged younger than 40 years: 1) indications for HRA; 2) patient-reported outcomes in terms of the modified Harris Hip Score (HHS); 3) dislocation rate; and 4) revision rate.

Methods

This retrospective analysis identified 267 hips from 224 patients who underwent an hip resurfacing arthroplasty (HRA) from a single fellowship-trained surgeon using the direct lateral approach between 2007 and 2019. Inclusion criteria was minimum two-year follow-up, and age younger than 40 years. Patients were followed using a prospectively maintained institutional database.

Results

A total of 217 hips (81%) were included for follow-up analysis at a mean of 3.8 years. Of the 23 females who underwent HRA, none were revised, and the median head size was 46 mm (compared to 50 mm for males). The most common indication for HRA was femoroacetabular impingement syndrome (n = 133), and avascular necrosis ( (n = 53). Mean postoperative HHS was 100 at two and five years. No dislocations occurred. A total of four hips (1.8%) required reoperation for resection of heterotopic ossification, removal of components for infection, and subsidence with loosening. The overall revision rate was 0.9%.

Conclusion

For younger patients with higher functional expectations and increased lifetime risk for revision, HRA is an excellent bone preserving intervention carrying low complication rates, revision rates, and excellent patient outcomes without lifetime restrictions allowing these patients to return to activity and sport. Thus, in younger male patients with end-stage hip disease and higher demands, referral to a high-volume HRA surgeon should be considered.

Hip Resurfacing: A Single Surgeon U.S. Series With Minimum Ten-Year Follow-up

BACKGROUND

Metal-on-metal hip resurfacing is an alternative to total hip arthroplasty (THA). The aim of this study was to determine implant survivorship, analyze patient-reported outcomes measures and to determine patient satisfaction for patients who underwent metal-on-metal hip resurfacing at a large US academic institution by a single surgeon with a minimum of 10-year follow-up.

METHODS

Patients who underwent hip resurfacing from September 2006 through November 2009 were included. Patient demographics and variables were collected from a prospectively maintained institutional database and patients completed an additional questionnaire with patient-reported outcomes measures.

RESULTS

A total of 350 patients (389 hips) out of 371 (433 hips) with a minimum 10-year follow-up were successfully contacted (94.3% follow-up). Mean age was 53 years, 258 were male (73%). 377 out of 389 hips (96.9%) did not require additional surgery. Gender was significantly related to implant survivorship (males 99.0%, females 90.9%; P < .001). 330 patients (369 hips, 94.8%) were satisfied with their surgery. Males had higher proportion of satisfaction scores (P = .02) and higher modified Harris Hip Score (odds ratio = 2.63 (1.39, 4.98), P = .003). Median modified Harris Hip Score score for non-revised hips was 84.0 [80.0; 86.0] versus those requiring revision, 81.5 [74.0; 83.0], (P = .009).

CONCLUSION

At a minimum 10-year follow-up, hip resurfacing, using an implant with a good track record, demonstrates 99.0% survivorship in male patients with an average age of 52 years. We believe that the continued use of metal-on-metal hip resurfacing arthroplasty in this population is justified by both positive patient reported outcomes and survivorship.

Balance Remains Impaired after Hip Arthroplasty: A Systematic Review and Best Evidence Synthesis

Background: Hip arthroplasty (HA) is the most common intervention for joint replacement, but there is no consensus in the literature on the real influence of this procedure on balance, or on what factors in the pre-operative, surgical, and post-operative stages may affect it. Purpose: To synthesize the evidence on how Hip Arthroplasty (HA) affects balance, identifying pre-operative, surgical, and postoperative risk factors that may impair balance in HA patients, with the aim to improve patients’ management strategies. Methods: A literature search was performed on PubMed, PeDRO, and Cochrane Collaboration on 25 May 2021. Inclusion criteria: clinical report of any level of evidence; written in English; with no time limitation; about balance changes in hip osteoarthritis (OA) patients undergoing HA and related factors. Results: 27 papers (391 patients) were included. Overall, the evidence suggested that balance is impaired immediately after surgery and, 4–12 months after surgery, it becomes better than preoperatively, although without reaching the level of healthy subjects. A strong level of evidence was found for hip resurfacing resulting in better balance restoration than total HA (THA), and for strength and ROM exercises after surgery positively influencing balance. Conclusion: Both the surgical technique and the post-operative protocols are key factors influencing balance; thus, they should be carefully evaluated when managing hip OA in patients undergoing HA. Moreover, balance at 4–12 months after surgery is better than preoperatively, although without reaching the level of the healthy population. Attention should be paid in the early post-operative phase, when balance may be impaired in patients undergoing HA.

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.

Is a cementless fixation of the femoral component suitable for metal-on-metal hip resurfacing arthroplasty?

BACKGROUND

Hip resurfacing arthroplasty (HRA) typically uses a hybrid design (cemented femoral component and cementless acetabular shell) but has recently been performed with fully cementless components. There is a paucity of information on the clinical performance of these cementless designs.

METHODS

The UCLA clinical scores, SF-12 quality of life scores, complication rates, survivorship and radiographic signs of loosening or gross stress shielding of 39 hips (39 male patients) implanted with cementless HRA were compared with those of 40 hips (37 male patients) implanted with hybrid HRA during the same time frame.

RESULTS

There were no significant differences in postoperative clinical and quality of life scores, complication rates, or radiographic signs of loosening between the 2 groups. The 5-year Kaplan-Meier survivorship was 97.2% for the cementless group and 100% for the hybrid group. This difference was not significant (p = 0.3694). There were no femoral component failures in any of the 2 groups.

CONCLUSIONS

At a mean follow-up of 6 years, there is no tangible difference between the performance of cementless HRA compared to hybrid HRA. The absence of learning curve associated with this device and the potential for better preservation of femoral neck bone mineral density suggest that this technology is well suited for young patients with good bone quality seeking to resume an active lifestyle including high-impact activities.

Five to Ten-Year Results of the Birmingham Hip Resurfacing Implant in the U.S.: A Single Institution's Experience

BACKGROUND

International surgeon series and registry data have demonstrated positive outcomes and long-term survival of the Birmingham Hip Resurfacing (BHR) implant. We report the 5 to 10-year results from a single center in the U.S.

METHODS

Three hundred and fourteen patients (360 hips) underwent surface replacement arthroplasty with use of the BHR implant and consented to study participation. Patient-reported outcomes and complication and revision data were collected at a minimum of 5 years of follow-up for 93% (324 of 350) of the hips in surviving patients. A matched-cohort analysis was used to compare clinical outcomes between use of the BHR and total hip arthroplasty.

RESULTS

Mean modified Harris hip score (mHHS) and University of California, Los Angeles (UCLA) scores significantly improved postoperatively, to 89.9 and 8.0, respectively (p < 0.001). The Kaplan-Meier estimated rate of survival for all-cause revision was 97.2% (95% confidence interval [CI], 94.7% to 98.5%) and 93.8% (95% CI, 88.8% to 96.7%) at 5 and 10 years, respectively. In a subgroup analysis of patients fitting our current BHR inclusion criteria (males <60 years of age with a diagnosis of osteoarthritis and anatomy conducive to a femoral head component of ≥48 mm), survival free of aseptic revision was 99.5% (95% CI, 96.6% to 99.9%) at 5 years and 98.2% (95% CI, 94.4% to 99.4%) at 10 years. Fourteen patients (4.3% of all hips) required revision. Postoperative UCLA scores were significantly greater for BHR compared with total hip arthroplasty (mean score of 8.0 ± 2.0 versus 7.6 ± 1.8; p = 0.040) in a matched-cohort analysis, with patients matched according to preoperative UCLA score, diagnosis, age, sex, and body mass index. Among matched patients who were highly active preoperatively (UCLA score of 9 to 10), BHR provided a smaller median decrease in the postoperative UCLA score (0.0 versus 1.0; p < 0.001), which was clinically important according to the minimal clinically important difference (MCID, 0.92). Furthermore, BHR provided a greater likelihood of remaining highly active compared with total hip arthroplasty (61% compared with 20%; p < 0.001).

CONCLUSIONS

BHR demonstrated excellent survivorship and clinical outcomes at 5 to 10 years in selected patients. As compared with total hip arthroplasty, the use of the BHR may provide highly active patients with clinically important advantages in postoperative activity as well as a greater likelihood of remaining highly active. Continued follow-up is necessary to validate long-term BHR outcomes.

LEVEL OF EVIDENCE

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

Metal on Metal Hip Resurfacing in Patients 45 Years of Age and Younger at Minimum 5-Year Follow-Up

BACKGROUND

Metal on metal hip resurfacing (MoM-HR) is an alternative to total hip arthroplasty in young and active patients. The purpose was to determine the survivorship of MoM-HR procedures performed in patients aged 45 years and younger assessing patient-reported outcome measures (PROMs) at minimum 5-year follow-up.

METHODS

All 217 patients equal to or younger than 45 years of age at the time of surgical intervention presenting to our center with MoM-HR between May 2002 and May 2011 were prospectively followed. Baseline demographic data, preoperative and postoperative radiographic measurements, and validated PROMs were obtained (Hip Disability and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and University of California, Los Angeles Activity Score). Survivorship was calculated using Kaplan-Meier analysis, and risk factors for failure were identified using multivariate regression analysis.

RESULTS

The overall survivorship excluding septic failures was 94.6% and 93.8% at 5 and 10 years, respectively. Aseptic loosening of the acetabular component was the most common mode of failure (11/20 cases). Gender, head size, and acetabular abduction angle had no significant effect on survivorship. Significant improvements in PROMs were seen for Hip Disability and Osteoarthritis Outcome Score, Western Ontario and McMaster Universities Osteoarthritis Index, and University of California, Los Angeles Activity Scale (P < .001).

CONCLUSION

This study indicates that MoM-HR is a suitable option for young individuals, as demonstrated through improved functional scores and low revision rates. The survivorship of HR in the younger than 45 age-group was similar to that of total hip arthroplasty, as well as HR in older patients. Given the proposed benefits of HR, this procedure may be viewed as a viable option in patients aged younger than 45 years.

A comparison of two different navigated hip replacement techniques on leg length discrepancy

We hypothesised that a femoral array placed into bone or an external (pinless) reference marker made no difference to leg length discrepancy in patients undergoing navigated total hip arthroplasty. Consecutive patients undergoing navigated total hip arthroplasty. 162 patients. No statistical difference between preoperative leg length discrepancy (p = 0.524). Mean intraoperative change was 3.7 mm and 4.6 mm (p = 0.262). The mean change in leg length measure post operatively was 4.2 mm and 4.1 mm (p = 0.656). No significant difference in leg length discrepancy between a pinless reference markers and a femoral array placed into the bone.

Microstructure and Surface Damage in Retrieved Metal-on-Metal Hip Arthroplasties

BACKGROUND

Besides promising results of metal-on-metal (MOM) hip arthroplasty (HA), frequent failures have been reported even in the short term. Many host, surgical, design, metallurgical, and processing factors have been evoked in the base of these events. We have tried to characterize and to evaluate metallurgical and processing features present in this type of implants.

METHODS

The acetabular and femoral components of 20 MOM HAs collected from a multicenter retrieval program were examined. All the specimens were inspected with naked eye, with confocal microscopy and vertical scanning interferometry, scanning electron microscopy, back-scattered electron imaging, and energy-dispersive X-ray spectroscopy, in 25 zones of each articular component.

RESULTS

Gas pores, shrinkage voids and holes of detached carbides, carbides on surface, embedded particles, scratches and marks of wear, surface discoloration, surface deposits, and tribochemical reaction layers were widely dispersed through a substantial percentage of the total bearing surface in all the implanted components. Surface cup and head voids, and cup scratches showed significant correlation with the clearance of pair. A higher surface damage of the cup and head was observed mainly in the low clearance prostheses. There was no other significant correlation or difference in the incidence and importance of any of these defects between resurfacing hip arthroplasties and total hip arthroplasties, or according to the pair diameter.

CONCLUSION

Some metallurgical features and surface damage were significantly present in the retrieved implants of MoM HAs. It would be desirable to improve the structure and metallurgical characteristics of these implants to avoid those effects and optimize their performance.

Correlation between serum metal ion levels and adverse local tissue reactions after Conserve® Plus hip resurfacing arthroplasty

BACKGROUND

Adverse local tissue reactions (ALTR) have been associated with the use of metal-on-metal (MoM) bearings and the monitoring of cobalt (Co) and chromium (Cr) ion levels in blood or serum may be the best way to evaluate in vivo the wear of these bearings. However, the relationship between Co and Cr ion concentrations and the formation of ALTR remains unclear.

METHODS

We investigated the relationship between ALTR and serum Co and Cr ion levels and identified the clinical factors influencing the formation of ALTR in patients treated with MoM hip resurfacing arthroplasties. 228 patients with unilateral Conserve® Plus MoM hip resurfacing had serum metal ion studies performed more than 1 year after surgery. Metal artifact reduction sequence magnetic resonance imaging (MARS MRI) was performed on subjects at risk for ALTR as determined by a screening protocol.

RESULTS

12 patients had ALTR. Logistic regression showed a strong association of ALTR with elevated ion levels and with low (<10 mm) contact patch to rim distance.

CONCLUSIONS

MoM bearings require enough functional coverage of the socket by design and then precise implantation to maximise functional coverage of the femoral ball, enhance lubrication, and avoid edge-loading wear.

Risk factors for wear-related failures after hip resurfacing in patients with a low contact patch to rim distance

Aims

A contact patch to rim (CPR) distance of < 10 mm has been associated with edge-loading and excessive wear. However, not all arthroplasties with a low CPR distance show problems with wear. Therefore, CPR distance may not be the only variable affecting the post-operative metal ion concentrations.

Patients and Methods

We used multiple logistic regression to determine what variables differed between the patients who had high and low cobalt (CoS) and chromium (CrS) serum ion concentrations within a cohort of patients with low (< 10 mm) CPR distances. A total of 56 patients treated with unilateral hip resurfacing arthroplasty (HRA) had CoS and CrS ion studies performed more than one year after surgery. The mean age of the patients at the time of surgery was 51.7 years (29 to 70), with 38 women (68%) and 18 men (32%).

Results

It was seen that 47 patients had low ion levels (< 7µg/L) and nine had high ion levels (≥ 7µg/L). We found increased risks of high wear with decreasing CPR distance.

Conclusion

The use of CPR distance measurements to predict hips at risk for elevated wear is needed for all patients with HRA. We recommend that patients with low CPR distances have at least one serum ion study performed while patients with CPR distance > 10 mm do not need routine ion studies. We believe that patients with low CPR distance and low ions do not need repeat ion studies unless the patient becomes symptomatic or has substantial radiographic changes. Cite this article: Bone Joint J 2017;99-B:865–71.

Effects of Previous Osteotomy on Outcome of Hip Resurfacing Arthroplasty

The effect of previous conservative surgeries on the outcome of metal-on-metal hip resurfacing arthroplasty (HRA) has not been studied. This study compared postoperative clinical scores and survivorship results of hips with and without previous osteotomies in a population of patients who underwent HRA. A total of 1101 patients (1375 hips) with a mean age of 51.3 years at the time of surgery underwent HRA at a single center. Sixty-nine patients had undergone prior surgery on the operated hip including 14 osteotomies (1 pelvic, 6 femoral, and 7 combined pelvic and femoral osteotomies). Mean follow-up was comparable for patients with prior osteotomy and patients in the control group (101 months vs 96 months, P=.6916); however, patients with prior osteotomies were much younger at the time of surgery (34 years vs 51 years, P=.0001). Kaplan-Meier survival estimates were calculated, and the Cox proportional hazard ratio was used to adjust for the covariates that differed between the 2 groups and affected the survivorship of hip resurfacing. Patients who underwent prior osteotomy showed lower pain and activity scores. In addition, patients who underwent prior osteotomy had a greater chance of revision than the rest of the cohort (hazard ratio, 3.87; 95% confidence interval, 1.54-9.68; P=.004). For patients in whom the natural anatomy or the bone quality of the hip has been severely altered by a prior osteotomy, HRA may be contraindicated if good component fixation cannot be achieved and hip biomechanics restored. [Orthopedics. 2017; 40(4):e609-e616.].

Contact patch to rim distance: the quintessential tool for metal-on-metal bearing in vivo performance analysis - a review

With metal-on-metal (MoM) bearings, fluid film lubrication is disrupted when the contact patch area between the femoral head and the cup is close to the edge of the acetabular component, making the calculation of the contact patch to rim (CPR) distance a key variable in the study of the performance of MoM bearings. A few research centers have used models of varying complexity to calculate the CPR distance and determine its relationship with assessments of component wear. In this review, we aimed to summarise the current knowledge related to the application of CPR distance calculations in the study of in vivo performance of MoM bearings. Our systematic search of the US National Library of Medicine yielded 9 relevant publications in which 3 different models were used for the computation of the CPR distance. The 3 models show different levels of complexity and their use is mainly dependent upon the size of the subject sample and the nature of the data collected as a dependent variable. The studies reviewed consistently showed a strong inverse correlation between CPR distance and wear or metal ion levels suggesting that any study aiming to determine the risk factors for MoM hip devices needs to include an assessment of CPR distance. Cup anteversion can be measured reliably with various tools and should not be an obstacle to the use of this essential variable that is CPR distance.

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.

Aseptic loosening of cobalt chromium monoblock sockets after hip resurfacing

INTRODUCTION

Acetabular component loosening is a leading cause for revision after metal-on-metal hip resurfacing arthroplasty (MMHRA). We aimed to identify potential risk factors and determine radiographic signs associated with this mode of failure.

METHODS

From a series of 1375 hips treated with MMHRA, 21 (20 patients) underwent revision surgery secondary to aseptic loosening of the acetabular component and 6 patients had a radiographically loose acetabular component. A control group of 27 hips (26 patients) was selected among the patients that did not have a revision, and was matched for age, gender, component size and diagnosis.

RESULTS

Mean time to revision in the loosening group was 103.0 months and the mean time of follow-up in the control group was 161.4 months. We found greater activity levels, range of motion scores, and cup abduction angles in the loosening group. The centre-edge (CE) angle of Wiberg was 10° lower in the loosening group compared with the control group. In addition, 11 of the hips from the study group presented a sclerotic halo superior to the cup on the last radiograph vs. none in the control group. There was no difference in the prevalence of postoperative reaming gaps or radiographic signs of neck-cup impingement between the 2 groups.

DISCUSSION

Risk factors for acetabular loosening included hip dysplasia with low CE angle, and a large cup abduction angle. The patient's level of activity influences the appearance of symptoms and the time to revision. We recommend selecting patients with a sufficient CE angle and properly orienting the cup.

Hip resurfacing: history, current status, and future

Hip resurfacing arthroplasty (HRA) presents several advantages over conventional total hip arthroplasty (THA), including conservation and preservation of bone, reduced risk of dislocation, easy replication of hip biomechanics and easy revision if needed. It is a particularly appealing procedure for young patients. HRA has been performed for over 40 years following the same technological advances as THA. The bearing material used by most designs is metal-on-metal (MoM), which has the best compromise between strength and wear properties. However, MoM HRA has a specific set of possible complications. Aseptic femoral failures were initially the most prevalent cause for revision but progress in patient selection and surgical technique seem to have resolved this problem. Wear-related failures (high metal ion levels and adverse local tissue reactions) are now the main concern, and are essentially associated with poor acetabular component design and orientation, to which MoM is more sensitive than other bearing materials. The concept of functional coverage is key to understanding how MoM bearings are affected by edge wear. Only a 3-D assessment of cup position (e.g., the contact patch to rim distance) provides the necessary information to determine the role of cup positioning in relationship with abnormal bearing wear.The concept of hip resurfacing is more valid today than ever as the age of the patients in need of hip arthroplasty keeps getting lower. The recent publication of several excellent long-term survivorship results suggests that selection of a well-designed resurfacing system and accuracy in the placement of the cup can achieve long-term durability.

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.

Current indications for hip resurfacing arthroplasty in 2016

Hip resurfacing arthroplasty (HRA) is an alternative to conventional, stemmed total hip arthroplasty (THA). The best reported results are young, active patients with good bone stock and a diagnosis of osteoarthritis. Since the 1990s, metal-on-metal (MoM) HRA has achieved excellent outcomes when used in the appropriate patient population. Concerns regarding the metal-on-metal bearing surface including adverse local tissue reaction (ALTR) to metal debris have recently lead to a decline in the use of this construct. The current paper aims to provide an updated review on HRA, including a critical review of the most recent literature on HRA.

Revision Rate and Patient-Reported Outcome After Hip Resurfacing Arthroplasty: A Concise Follow-Up of 1064 Cases

We investigated survival and outcomes in 1064 HRA hips operated on between 1998 and 2009. After a mean of 7.8 years, 771 patients (72.4%) completed questionnaires, with a further 160 (15.0%) contacted by phone and 18 (1.7%) had died. There were 54 revisions. Overall implant survival at 10 years was 94.4%. Independent predictors of lower survival were female gender (P=0.015) and cup inclination ≥55° (P<0.001). Woman with cup inclination ≥55° had the highest failure rate with 10-year survival of 69.3%. Vertical cup inclination ≥55° did worse than cups <55° in both men and women. Overall men did better than women, and men with cups <55 degrees did best. Men had significantly better patient-reported outcome scores than woman.

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.

Short-term Results of Birmingham Hip Resurfacing in the United States

Previous data on the survivorship of the Birmingham Hip Resurfacing (BHR) implant have come from design surgeons and large national databases outside of the United States, and there is a lack of reported outcomes of surface replacement arthroplasty from US centers. A retrospective study was undertaken of 1271 hips treated with a BHR system (Smith & Nephew, Memphis, Tennessee) between June 2006 and September 2008 at 6 high-volume total joint centers in the United States. Demographic features, Harris Hip Score (HHS), and radiographic findings were recorded. Patients who did not have a 2-year follow-up visit were contacted by telephone. All patients were asked about complications, reoperations, or failure of the implants. Of the treated hips, 1144 (90%) had a minimum of 2 years of clinical follow-up (mean, 2.9 years; range, 1.8-4.2 years). Mean age was 52.3 years, and 75% of patients were men. Mean HHS improved from 55.8 preoperatively to 97.4 at the most recent follow-up (P<.001). There were 16 (1.4%) revisions to total hip arthroplasty (THA) for fracture (7), early dislocation (3), acetabular component malpositioning with pain (3; 1 with metallosis), infection (1), femoral loosening (1), and pseudotumor (1). There were 9 additional complications (0.8%) that did not require revision, including 3 dislocations treated with closed reduction, 2 fractures, 3 nerve injuries, and 1 pseudotumor. At 2 to 4 years of follow-up, the revision rate and the major complication rate with the BHR system were similar to those in previous reports of primary THA. Excellent clinical results were observed, but further follow-up is necessary to assess mid- and long-term results with the BHR system in US patients.

Do hardened femoral heads reduce blood metal ion concentrations after hip resurfacing?

BACKGROUND

Elevated cobalt and chromium ion concentrations have been associated with the use of metal-on-metal bearings in hip arthroplasty. The use of a differential hardness bearing may reduce metal particle release. The aim of our study was to compare circulating cobalt (Co) and chromium (Cr) ion levels between patients treated with a standard all 'as-cast' heat treated bearing and a differential hardness bearing.

MATERIALS AND METHODS

One hundred and thirty-two patients implanted with unilateral hip resurfacing arthroplasties and having had blood metal ion studies performed between one and six years after surgery were retrospectively selected. There were 73 patients in the standard all 'as cast' heat treated bearing group (group 1) and 59 in the differential hardness bearing group (group 2).

RESULTS

Clinical and quality of life scores were comparable between groups. The median Co in group 1 was 1.01 µg/L and 1.23 µg/L in group 2 (p = 0.0566). The median Cr in group 1 was 1.60 µg/L and 1.34 µg/L in group 2 (p = 0.0505).

CONCLUSION

Compared with conventional heat-treated CoCr bearings, differential hardness metal-on metal bearings do not confirm in vivo the hopes of a substantial reduction in circulating metal ions concentrations suggested by in vitro wear studies.

A new method of registration in navigated hip arthroplasty without the need to register the anterior pelvic plane

A prospective clinical study of 50 patients was conducted to validate a new method of imageless computer navigated hip arthroplasty. The new method enables the surgeon to acquire all registration points with the patient positioned and draped in lateral decubitus position. The final component orientation was measured from post-operative CT scans. The mean error in component position was -1.1° (SD 3.1°) for inclination and 0.9° (SD 4.3°) for anteversion. This compared favourably with the error of -1.8° (SD 1.8°) for inclination and -4.8° (SD 2.7°) for anteversion when using the traditional APP registration. Results show that one can expect the acetabular component to be within a safe zone of ±10° in 99.8% for inclination and 97.7% for anteversion when using the new lateral registration method. Level of Evidence Level II, Prognostic study.

What are the current clinical issues in wear and tribocorrosion?

Wear and corrosion in joint arthroplasty are important causes of failure. From the standpoint of current clinical importance, there are four main categories of wear and tribocorrosion: polyethylene wear, ceramic-on-ceramic (CoC) bearing wear, metal-on-metal (MoM) bearing wear, and taper tribocorrosion. Recently, problems with wear in the knee have become less prominent as have many issues with hip polyethylene (PE) bearings resulting from the success of crosslinked PE. However, MoM articulations and taper tribocorrosion have been associated with soft tissue inflammatory responses, and as a result, they have become prominent clinical concerns. WHERE ARE WE NOW?: For PE wear in the hip, several advances include improved locking mechanisms and data supporting highly crosslinked polyethylenes (HXLPE). Edge-loading in CoC articulations can contribute to stripe wear and subsequent squeaking. For MoM articulations, the relationship of wear-to-edge loading, sensitivity to component positioning, typical soft tissue response, and use of imaging is increasingly understood. Taper tribocorrosion (from femoral head-neck junctions and other modular elements) and associated soft tissue inflammatory responses appear to be serious clinical issues that are not fully understood. WHERE DO WE NEED TO GO?: In the knee, clinical concerns remain with the efficacy of HXLPE, modular connections, and metal allergies. For PE wear in the hip, concerns remain regarding how to increase crosslinking of PE while minimizing PE fractures. With CoC articulations, questions remain on how to prevent noises, chipping, and impingement and if enhanced designs can contribute to improved results. For MoM articulations, we need to improve imaging tests for soft tissue reactions, determine best practices in terms of monitoring protocols, and better define if, how, and when to act on serum metal levels. For taper tribocorrosion, we need to use modularity wisely and also understand how to improve tapers and materials in the future. For patients at risk for tribocorrosion, we need to define realistic diagnostic and monitoring protocols. We also need to enhance revision methods, and the threshold of acceptable soft tissue damage, to minimize complications associated with soft tissue damage such as hip instability. HOW DO WE GET THERE?: HXLPE and other bearing surfaces will likely continue to be refined. We need to develop tapers with more resistance to tribocorrosion through improved understanding of the manufacturing process and ongoing engineering improvements. Revision procedures for wear and tribocorrosion can be enhanced by determining when partial component retention is appropriate and how best to manage soft tissue damage. For CoC articulations, enhanced designs are required to minimize noises, chipping, and impingement. Importantly, we must continue to promote and analyze joint replacement registries to identify early failures and analyze long-term successes.

Hip resurfacing arthroplasty: mid-term results in 486 cases and current indication in our institution

In the previous decade, metal-on-metal hip resurfacing has been considered an attractive option and theoretically advantageous over conventional total hip arthroplasty, especially in young active patients. Different authors have reported favourable mid-term clinical and functional results with acceptable survival rates. Proper indication and planning, as accurate technical execution have been advocated to be crucial elements for success.Concerns regarding serum metal ion levels and possible clinical implications have led in the last years to a decline in the use of metal-on-metal hip resurfacing and metal-on-metal bearings in general.The aim of this study is to present the results of our first 486 cases of hybrid hip resurfacing arthroplasties with a second generation cementing technique, and to describe our current restricted indication of this type of prosthesis, in the light of recent findings in the literature about the possible complications related to metallosis or improper patient selection. Global survivorship of our series was 97.9% at a mean follow-up of 7.2 years.In the second season of our experience the indication is restrictive. The candidate for a resurfacing hip replacement is a young and active male patient, with good bone quality, that has been made aware of the risks and benefits of this type of prosthesis.

High incidence of pseudotumours after hip resurfacing even in low risk patients; results from an intensified MRI screening protocol

We intensified our screening protocol for the presence of pseudotumours in a consecutive series of patients with a hip resurfacing arthroplasty (HRA), to establish whether we should be alert to the presence of 'silent' pseudotumours. Patients categorised with high risk (11 hips) and low risk (10 hips) for pseudotumour development and a control group (23 hips) were screened with metal artefact reduction sequence (MARS) magnetic resonance imaging (MRI). The Anderson classification to grade any metal-on-metal (MoM) disease present on MARS-MRI images was used. In 15 out of 44 MRI scans pseudotumours were observed (34.1%), of which six were graded with mild (13.6%), eight with moderate (18.2%) and one with severe MoM disease (2.3%). Twelve pseudotumours were present in asymptomatic patients (27.3%). Metal ion levels were normal in 80% of the MARS-MRI screened patients. As a consequence of our intensified screening protocol, one patient was revised for pseudotumour formation and another patient was scheduled for revision. Silent pseudotumours were observed in all three groups. Before our intensified screening protocol was initiated, no pseudotumours were encountered in our cohort of 289 HRAs. We concluded that clinical outcomes and plain radiographs for screening MoM patients underestimates the presence of pseudotumours in MoM patients. The true clinical relevance of these pseudotumours is still unclear.

Risk of impingement and third-body abrasion with 28-mm metal-on-metal bearings

BACKGROUND

Concerns have been raised about the sequelae of metal-on-metal (MoM) bearings in total hip arthroplasty (THA). However, retrieval studies, which offer the best insight into the clinically relevant mechanisms of MoM wear, have followed predictable trends to date such as indicting cobalt-chromium (CoCr) metallurgy, cup design, high conformity between the head and cup, "steep cups," "microseparation," and "edge wear."

QUESTIONS/PURPOSES

We wished to evaluate a set of retrieved 28-mm MoM THA for signs of (1) cup-to-stem impingement; (2) normal wear pattern and concomitant stripe damage on femoral heads that would signify adverse wear mechanics; and (3) well-defined evidence of third-body scratches on bearings that would indicate large abrasive particles had circulated the joint space.

METHODS

Ten 28-mm MOM retrievals were selected on the basis that femoral stems were included. Revision surgeries at 3 to 8 years were for pain, osteolysis, and cup loosening. CoCr stems and the MoM bearings were produced by one vendor and Ti6Al4V stems by a second vendor. All but two cases had been fixed with bone cement. We looked for patterns of normal wear and impingement signs on femoral necks and cup rims. We looked for adverse wear defined as stripe damage that was visually apparent on each bearing. Wear patterns were examined microscopically to determine the nature of abrasions and signs of metal transfer. Graphical models recreated femoral neck and cup designs to precisely correlate impingement sites on femoral necks to cup positions and head stripe patterns.

RESULTS

The evidence revealed that all CoCr cup liners had impinged on either anterior or posterior facets of femoral necks. Liner impingement at the most proximal neck notch occurred with the head well located and impingement at the distal notch occurred with the head rotated 5 mm out of the cup. The hip gained 20° motion by such a subluxation maneuver with this THA design. All heads had stripe wear, the basal and polar stripes coinciding with cup impingement sites. Analysis of stripe damage revealed 40 to 100-μm wide scratches created by large particles ploughing across bearing surfaces. The association of stripe wear with evidence of neck notching implicated impingement as the root cause, the outcome being the aggressive third-body wear.

CONCLUSIONS

We found consistent evidence of impingement, abnormal stripe damage, and evidence of third-body abrasive wear in a small sample of one type of 28-mm MoM design. Impingement models demonstrated that 28-mm heads could lever 20° out of the liners. Although other studies continue to show good success with 28-mm MoM bearings, their use has been discontinued at La Pitie Hospital.

What causes unexplained pain in patients with metal-on metal hip devices? A retrieval, histologic, and imaging analysis

BACKGROUND

Adverse tissue reactions associated with metal-on-metal (MOM) hips are common in resurfacing and total hip arthroplasty (THA) designs. The etiology of these reactions in painful, well-positioned arthroplasties is inconsistently described.

QUESTIONS/PURPOSES

The purposes of this study were to compare the (1) articular wear rates; (2) histologic findings; (3) synovial response on MRI; and (4) graded intraoperative tissue damage between well-positioned, MOM hips revised for unexplained pain and MOM hips revised for other reasons and to (5) determine whether the presence of a taper junction on a MOM articulation affects these four parameters in unexplained pain.

METHODS

We retrospectively studied 88 patients (94 hips) who had undergone revision of either a hip resurfacing or a large-head (> 36 mm) THA. Thirty-five hips revised for unexplained pain were compared with a control group of 59 hips revised for other causes. Articular wear was measured using three-dimensional contactless metrology and histologic analysis was performed using the aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) score. Preoperative MRI was performed on 57 patients to determine synovial volumes and thicknesses. Tissue damage was graded from intraoperative reports.

RESULTS

Articular wear rates in the unexplained pain group were lower than in the control group (median 2.6 μm/year versus 12.8 μm/year, p < 0.001). Sixty-six percent of patients in the unexplained pain group had histologic confirmation of ALVAL compared with 19% in the control group (p < 0.001). The synovial thickness on MRI was higher in the unexplained pain group (p = 0.04) and was highly predictive of ALVAL. Severe intraoperative tissue damage was noted in more cases in the unexplained pain group (p = 0.01). There were no differences in articular wear, histology, MRI, and tissue damage between resurfacings and THAs revised for unexplained pain.

CONCLUSIONS

Unexplained pain in patients with well-positioned MOM hips warrants further investigation with MRI to look for features predictive of ALVAL. Tissue destruction in these cases does not appear to be related to high bearing wear or the presence of a taper.

Does femoral neck to cup impingement affect metal ion levels in hip resurfacing?

BACKGROUND

Impingement of the femoral neck with the acetabular component after metal-on-metal hip resurfacing arthroplasty (HRA) is a possible cause of edge loading and accelerated bearing wear. No attempt has been made to correlate radiographic impingement signs and blood metal ion levels.

QUESTIONS/PURPOSES

We (1) compared serum cobalt (CoS) and chromium (CrS) concentrations between patients with and without radiographic impingement signs treated with unilateral HRA, (2) determined whether divot depth on the femoral neck correlated with CoS and CrS, and (3) assessed the predictive value of radiographic impingement signs for high levels of CoS and CrS.

METHODS

A retrospective radiographic review of 141 patients with CoS and CrS analyses yielded 21 patients with and 120 without radiographic impingement signs (controls). Radiographic measurements included divot depth and orientation of the acetabular component to compute the contact patch to rim distance, a measure of functional head coverage. We defined a patient as having radiographic impingement signs if a remodeling of the femoral neck cortex showed a depression matching the predicted path of an impinging acetabular component. CoS and CrS were analyzed by inductively coupled plasma mass spectrometry and the radiographs were taken within 12 months of the last blood draw.

RESULTS

Median CoS and CrS were greater in the impingement group than in controls in patients with less than 10-mm contact patch to rim distances. Divot depth did not correlate with CoS or CrS. In predicting elevated ion levels (≥ 7 μg/L), the presence of a radiographic impingement sign showed a sensitivity of 50% for CoS and 33% for CrS and a specificity of 87% for both CoS and CrS.

CONCLUSIONS

Radiographic impingement signs influenced CoS and CrS only when the functional head coverage was insufficient due to poor socket positioning. Radiographic impingement signs alone were not a good predictor of elevated metal ion levels.

Metal ion levels in total hip arthroplasty versus hip resurfacing

Recent studies suggest that the tapered interface between stem and femoral head may be a substantial source of cobalt and chromium ion release after metal-on-metal (MOM) total hip arthroplasty (THA). This study compared patient ion levels after MOM hip resurfacing (HR) and MOM THA performed with identical acetabular components. 110 HRs were compared with 22 THAs. All had well-oriented components, unilateral implants, and serum ion studies beyond one year post-operatively. The HR group's median cobalt value was 1.11 μg/L vs. 2.86 μg/L for the THA patients. The HR group's median chromium value was 1.49 μg/L vs. 2.94 μg/L for THA. Significantly higher THA ion levels suggest a source of ions other than the MOM bearing itself.

Contact patch to rim distance predicts metal ion levels in hip resurfacing

BACKGROUND

Component design, size, acetabular orientation, patient gender, and activity level have been suggested as factors leading to elevated metal ion concentrations after-on-metal hip resurfacing arthroplasty (MMHRA). The calculation of the contact patch to rim (CPR) distance integrates component size, design, and acetabular orientation and may be a good predictor of elevated metal ion levels.

QUESTIONS/PURPOSES

We evaluated the effects and the predictive value of the CPR distance on serum cobalt (CoS) and chromium (CrS) ion levels.

METHODS

We retrospectively studied 182 patients with Conserve Plus MMHRAs at a minimum of 12 months after surgery (median, 57 months; range, 12-165 months). CoS and CrS levels were analyzed using inductively-coupled plasma mass spectrometry. Multiple logistic regression was performed to determine which if any of the factors related to serum ion levels.

RESULTS

Patients with CPR distances of 10 mm or less had a 37-fold increased risk of having elevated CoS of 7 μg/L or higher. Similarly, these patients had an 11-fold increased risk of having elevated CrS of 7 μg/L or higher. Sex and University of California Los Angeles activity scores did not influence the postoperative CoS and CrS levels. The negative predictive value for CPR distance less than 10 mm was 99.3% for CoS greater than 7 μg/L and 98.0% for CrS greater than 7 μg/L.

CONCLUSIONS

Our observations suggest the CPR distance would be a useful indicator to determine which patients are at risk for elevated ion levels. Patients with CPR distances greater than 10 mm need not be monitored unless they become symptomatic.

Can patients return to high-impact physical activities after hip resurfacing? A prospective study

PURPOSE

Although the resumption of low-impact sports activities is compatible with total hip arthroplasty (THA), participation in high-impact sports seems problematic, and there is no consensus as to whether it is advisable. The purpose of this article is to evaluate the quality and possibility of resuming high-impact physical activities after hip resurfacing.

MATERIALS

The study was performed in an on-going, single-surgeon, prospective series of 215 resurfacing arthroplasties (RSA). Mean follow-up was 44.1 months (range, 39.1-54.5). Clinical evaluation included the Postel-Merle d'Aubigné (PMA) score, the Oxford hip score, the Harris hip score (HHS), Devane score, and UCLA activity score. A specific questionnaire analysing sports activities was administered to each patient to assess the number and level of physical activities performed (both before the operation and at final follow-up).

RESULTS

In the series of 202 consecutive patients (215 RSA), 50 patients (55 RSA) engaged regularly in at least one high-impact activity before their operation and the onset of pain, 102 patients practised at least one intermediate-impact activity, and the 50 remaining patients undertook only low-impact activities. Harris hip score increased from 44.8 (range, 23-68) before the operation to 97.8 (range, 85-100) at the last follow-up. Mean time to sports resumption after surgery was 14.6 weeks (range, 7-29). The resumption rate was 98 % for sports of any impact level and 82 % for high-impact activities. No osteolysis or implant loosening was observed at follow-up. No revision was performed.

CONCLUSION

In 2012, no consensus recommendations yet exist for the resumption of sports activities after RSA. Existing recommendations concern only conventional THA. We believe that RSA allows younger and more active patients to resume physical and sports activities without restriction. The rate of return to sports after RSA appears to be excellent and unequalled by conventional hip prostheses. High-impact sports seem to be compatible with hip resurfacing, although no long-term studies have analysed the impact of these activities on wear and/or aseptic loosening.