Birmingham Hip Resurfacing at 25 years.

Aims: The Birmingham Hip Resurfacing (BHR) was introduced in 1997 to address the needs of young active patients using a historically proven large-diameter metal-on-metal (MoM) bearing. A single designer surgeon's consecutive series of 130 patients (144 hips) was previously reported at five and ten years, reporting three and ten failures, respectively. The aim of this study was to extend the follow-up of this original cohort at 25 years. Methods: The study extends the reporting on the first consecutive 144 resurfacing procedures in 130 patients for all indications. All operations were undertaken between August 1997 and May 1998. The mean age at operation was 52.1 years (SD 9.93; 17 to 76), and included 37 female patients (28.5%). Failure was defined as revision of either component for any reason. Kaplan-Meier survival analysis was performed. Routine follow-up with serum metal ion levels, radiographs, and Oxford Hip Scores (OHSs) was undertaken. Results: Overall implant survival was 83.50% (95% confidence interval (CI) 0.79 to 0.90) at 25 years, and the number at risk was 79. Survival in male patients at 25 years was 89.5% (95% CI 0.83 to 0.96) compared to 66.9% for female patients (95% CI 0.51 to 0.83). Ten additional failures occurred in the period of ten to 25 years. These involved an adverse reaction to metal debris in four patients, a periprosthetic femoral neck fracture affecting five patients, and aseptic loosening in one patient. The median chromium levels were 49.50 nmol/l (interquartile range (IQR) 34 to 70), and the median cobalt serum levels were 42 nmol/l (IQR 24.50 to 71.25). The median OHS at last follow-up was 35 (IQR 10 to 48). During the 25-year study period, 29 patients died. Patient survival at 25 years was 75.10% (95% CI 0.67 to 0.83). Conclusion: This study demonstrates that MoM hip resurfacing using the BHR provides a durable alternative to total hip arthroplasty (THA), particularly in younger male patients with osteoarthritis wishing to maintain a high level of function. These results compare favourably to the best results for THAs.

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.

The Effectiveness of Blood Metal Ions in Identifying Patients with Unilateral Birmingham Hip Resurfacing and Corail-Pinnacle Metal-on-Metal Hip Implants at Risk of Adverse Reactions to Metal Debris.

BACKGROUND: We investigated whether blood metal ions could effectively identify patients with metal-on-metal hip implants with two common designs (Birmingham Hip Resurfacing [BHR] and Corail-Pinnacle) who were at risk of adverse reactions to metal debris. METHODS: This single-center, prospective study involved 598 patients with unilateral hip implants (309 patients with the BHR implant and 289 patients with the Corail-Pinnacle implant) undergoing whole blood metal ion sampling at a mean time of 6.9 years. Patients were classified into two groups, one that had adverse reactions to metal debris (those who had to undergo revision for adverse reactions to metal debris or those with adverse reactions to metal debris on imaging; n = 46) and one that did not (n = 552). Three metal ion parameters (cobalt, chromium, and cobalt-chromium ratio) were compared between groups. Optimal metal ion thresholds for identifying patients with adverse reactions to metal debris were determined using receiver operating characteristic analysis. RESULTS: All ion parameters were significantly higher (p < 0.0001) in the patients who had adverse reactions to metal debris compared with those who did not. Cobalt maximized the area under the curve for patients with the BHR implant (90.5%) and those with the Corail-Pinnacle implant (79.6%). For patients with the BHR implant, the area under the curve for cobalt was significantly greater than that for the cobalt-chromium ratio (p = 0.0005), but it was not significantly greater than that for chromium (p = 0.8483). For the patients with the Corail-Pinnacle implant, the area under the curve for cobalt was significantly greater than that for chromium (p = 0.0004), but it was similar to that for the cobalt-chromium ratio (p = 0.8139). Optimal blood metal ion thresholds for identifying adverse reactions to metal debris varied between the two different implants. When using cobalt, the optimal threshold for identifying adverse reactions to metal debris was 2.15 µg/L for the BHR group and 3.57 µg/L for the Corail-Pinnacle group. These thresholds had good sensitivities (88.5% for the BHR group and 80.0% for the Corail-Pinnacle group) and specificities (84.5% for the BHR group and 76.2% for the Corail-Pinnacle group), high negative predictive values (98.8% for the BHR group and 98.1% for the Corail-Pinnacle group), and low positive predictive values (34.3% for the BHR group and 20.0% for the Corail-Pinnacle group). The authority thresholds proposed by the United States (3 µg/L and 10 µg/L) and the United Kingdom (7 µg/L) missed more patients with adverse reactions to metal debris at 2.0% to 4.7% (twelve to twenty-eight patients) compared with our implant-specific thresholds at 1.2% (seven patients missed). CONCLUSIONS: Patients who underwent metal-on-metal hip arthroplasty performed with unilateral BHR or Corail-Pinnacle implants and who had blood metal ions below our implant-specific thresholds were at low risk of adverse reactions to metal debris. These thresholds could be used to rationalize follow-up resources in asymptomatic patients. Analysis of cobalt alone is acceptable. Implant-specific thresholds were more effective than currently recommended fixed authority thresholds for identifying patients at risk of adverse reactions to metal debris requiring further investigation. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

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<0.001), femoral head sizes ≤48 mm (p<0.01), and cup inclinations >55° (p<0.001). Linear regression demonstrated femoral head size was responsible for the highest proportion of variance in blood metal ions (cobalt p<0.001, R2 = 8%; chromium p<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 >55° had blood metal ions >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 (>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.

The future role of metal-on-metal hip resurfacing.

PURPOSE: The purpose of this review was to assess the ten to 15-year outcomes of metal-on-metal hip resurfacing (MoM HR) when performed at designing and independent centres, and make recommendations for the future use of MoM HR. METHODS: Studies reporting ten to 15-year outcomes for modern MoM HR devices from both designing and independent centres were reviewed. Outcomes from these studies were assessed to allow the formulation of recommendations for the future use of MoM HR. RESULTS: Two MoM HR designs, the Birmingham Hip Resurfacing (BHR) and Conserve Plus, have outcomes reported at a minimum of ten years. The BHR was the only device with outcomes reported at a minimum of ten years by both designing (overall survival of up to 95.8 % at 15 years) and independent surgeons (overall survival of 87.1-94.5 % at ten years). Implant survival in these seven BHR studies was influenced by the pre-operative diagnosis (primary osteoarthritis had better outcomes), gender (male patients had better outcomes), and femoral component head size (larger sizes had better outcomes). In contrast to independent centres, designing surgeons reported acceptable outcomes in female patients undergoing BHR. CONCLUSIONS: There remains a role for MoM HR in young active male patients with primary osteoarthritis, provided the surgeon has sufficient experience in the procedure, the implant has an established record, and the patient is aware of the potential risks associated with MoM bearings and HR. Very experienced HR surgeons may also consider this procedure in females provided they meet the refined inclusion criteria described (including femoral head sizes of 46 mm and above).

Influence of implant design on blood metal ion concentrations in metal-on-metal total hip replacement patients.

PURPOSE: Most factors considered to affect blood metal ions following metal-on-metal hip replacement are based on hip resurfacing patients. The study aims were to determine which factors affect blood metal ion concentrations following metal-on-metal total hip replacement (MoM THR). METHODS: All unilateral MoM THR patients at one centre with whole-blood cobalt (Co) and chromium (Cr) concentrations measured up to May 2013 were included. Blood sampling was at a mean of 4.5 years (range 1.1-11.8 years) postoperatively. RESULTS: Of 496 patients (mean age 59.1 years; 52.8% male), blood metal ions >7 µg/l were observed in 9.7% (n = 48). Large femoral head sizes (≥38 mm) had significantly higher (p < 0.0001) blood metal ions than smaller sizes (28/36 mm). Corail-Pinnacle implants produced significantly lower blood metal ions compared to other implant designs (p < 0.01 Co and Cr). Univariate linear regression demonstrated the only significant predictors of both blood Co and Cr concentrations were femoral head size (R(2) = 8.6% Co and R(2) = 3.3% Cr, both p < 0.0001) and implant design (R(2) = 8.8%, p = 0.005 Co and R(2) = 5.1%, p = 0.003 Cr). When the three THR implant design groups (Corail-Pinnacle, Synergy, Other) were analysed separately, femoral head size no longer significantly affected blood metal ions in any of the three implant design groups. CONCLUSIONS: Implant design was the most important factor affecting blood metal ion concentrations. We recommend the regularity of follow-up be tailored to survival rates of various MoM THR designs rather than according to femoral head size.

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 active patient follow-up on worst-case implant survival analysis.

BACKGROUND: Patients lost to follow-up pose problems when performing implant survival analysis. We are unaware of any report detailing how implant survival is affected by the sequential capture of patients.
 AIMS: To assess the logistics of long-term follow-up of patients undergoing Birmingham Hip Resurfacing (BHR), and to determine what impact this had on implant survival with time.
 METHODS: Between 1997 and 2006 data was prospectively collected on consecutive BHR's implanted by a single surgeon in patients under 50 years of age. Survival analysis was performed at monthly intervals during this study with all patients lost to follow-up at any point in time considered to have failed. 
 RESULTS: There were 447 BHR's implanted in 393 patients. At study commencement cumulative 10-year survival was 42% (95% CI 36% to 48%) calculated on the confirmed knowledge of the outcome at that time of 275 BHR's, with the remaining 172 lost to follow-up and considered to have been revised. As patients were actively followed-up there was gradual improvement in survival and narrowing of confidence intervals with a final 10-year BHR survival of 96.3% (95% CI 93.7% to 98.3%) with no loss to follow-up. 
 CONCLUSIONS: The findings demonstrate improvement in long-term implant survival with the sequential capture of young and active patients undergoing BHR who were initially considered lost to follow-up. The results reiterate the recommendation that every effort should be made to follow all patients up after joint replacement. This will improve the accuracy of survival reporting and assist comparison between different prostheses.

A review of hip resurfacings revised for unexplained pain.

BACKGROUND: Adverse reaction to metal debris (ARMD) has come to prominence as a mode of failure for metal-on-metal hip resurfacings. These patients frequently present with unexplained groin pain. AIMS: 1) To review all metal-on-metal hip resurfacings revised for unexplained pain seeking evidence for ARMD; 2) To determine the clinical outcome following revision arthroplasty. METHODS: The hospital database was searched (1997-2009) to identify all cases of Birmingham Hip Resurfacings (BHRs) revised for unexplained pain. ARMD was diagnosed using specific clinical, radiological, and histopathological criteria. Postoperatively all patients were assessed in clinic and completed an Oxford Hip Score (OHS) questionnaire. RESULTS: Of 3076 BHRs implanted 149 were revised. Of these, 20 BHRs in 17 patients were revised for unexplained pain (mean age at BHR 50.5 yr; 55% female). Unexplained pain requiring revision had a prevalence of 0.65% of all hip resurfacings performed (20/3076). ARMD was the mode of failure in 50% (n = 10). Common features observed in ARMD patients included hip-joint effusions, femoral neck thinning, intraoperative macroscopic granulomas, and lymphocytic infiltrates on histopathological examination. No ARMD patients had macroscopic soft-tissue destruction. A range of mechanical causes were responsible for the remaining failures. At a mean 3.6 year follow-up (range 1.1-8.0) one ARMD patient experienced a dislocation. There were no further complications or need for surgical re-intervention. Median OHS for the cohort was 25.0%. CONCLUSIONS: Hip resurfacings revised for unexplained pain comprise a diverse group of conditions with ARMD being the commonest. ARMD probably contains subgroups yet to be defined, some of which may be related to mechanical rather than immunological factors.

A comparison of subsidence of Exeter standard and long stems.

The survivorship of the polished, double taper Exeter stem is related to subsidence within the cement mantle. Long Exeter stems have altered geometry which may influence subsidence characteristics. Using digitised x-rays and appropriate computer software we measured the subsidence of 35 standard and 40 long stem Exeter implants. Measurements were taken from initial postoperative radiographs and repeated at intervals up to 5 years. Long stem implants were used in cemented revisions without the use of impaction bone grafting. Subsidence rates of the standard length stems in our study were comparable to that in published literature. Long stems did not replicate this subsidence pattern and had subsided less at 6, 12 and 24 months. However, the 205mm long stem, which has a fully tapered design, did follow the subsidence characteristics of the standard stem. Subsidence of long stem Exeter implants does not mirror that of the standard length stem. Loss of the fully tapered geometry of the longer stem implants may account for this finding. We suggest that whenever possible, the 205mm long stem should be used if the biomechanical principles of the standard Exeter stem are to be utilised.

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

BACKGROUND: Hip resurfacing has gained popularity for the treatment of young and active patients who have arthritis. Recent literature has demonstrated an increased rate of revision among female patients as compared with male patients who have undergone hip resurfacing. The aim of the present study was to identify any differences in survival or functional outcome between male and female patients with osteoarthritis who were managed with metal-on-metal hip resurfacing. METHODS: A prospective collection of data on all patients undergoing Birmingham Hip Resurfacing at a single institution was commenced in July 1997. On the basis of the inclusion and exclusion criteria, 1826 patients (2123 hips, including 799 hips in female patients and 1324 hips in male patients) with a diagnosis of osteoarthritis who had undergone the procedure between July 1997 and December 2008 were identified. The variables of age, sex, preoperative Oxford Hip Score, component size used, surgical approach, lead surgeon, and surgeon experience were analyzed. A multivariate Cox proportional hazard survival model was used to identify which variables were most influential for determining revision. RESULTS: The mean duration of follow-up was 3.46 years (range, 0.03 to 10.9 years). The five-year cumulative survival rate for the 655 hips that were followed for a minimum of five years was 97.5% (95% confidence interval, 96.3% to 98.3%). There were forty-eight revisions. Revision was significantly associated with female sex (hazard rate, 2.03 [95% confidence interval, 1.15 to 3.58]; p = 0.014) and decreasing femoral component size (hazard rate per 4-mm decrease in size, 4.68 [95% confidence interval, 4.36 to 5.05]; p < 0.001). Revision was not associated with age (p = 0.88), surgeon (p = 0.41), surgeon experience (p = 0.30), or surgical approach (p = 0.21). A multivariate analysis including the covariates of sex, age, surgeon, surgeon experience, surgical approach, and femoral component size demonstrated that sex was no longer significantly associated with revision when femoral component size was included in the model (p = 0.37). Femoral component size alone was the best predictor of revision when all covariates were analyzed (hazard rate per 4-mm decrease in size, 4.87 [95% confidence interval, 4.37 to 5.42]; p < 0.001). CONCLUSIONS: The present study demonstrates that although female patients initially may appear to have a greater risk of revision, this increased risk is related to differences in the femoral component size and thus is only indirectly related to sex. Patient selection for hip resurfacing is best made on the basis of femoral head size rather than sex.

The influence of surgical approach on outcome in Birmingham hip resurfacing.

UNLABELLED: Various approaches have been described for metal-on-metal hip resurfacing. We compared the posterolateral and direct lateral approaches for complications, pain, function, and implant survival in the short and medium term for two surgeons in a consecutive series of 790 patients (909 hips; July 1997 to July 2004) followed until July 2007. The direct lateral approach group included 135 resurfacing procedures and the posterolateral group included 774 procedures. There was no difference between the two groups for age or gender. The minimum followup for the anterolateral group was 2 years (mean, 5.1 years; range, 2.0-9.4 years) and for the posterolateral group 2 years (mean, 5.5 years; range, 2.0-9.6 years). There were no differences between the two approaches for complications, additional surgery, implant survival, or Oxford hip scores. The 8-year survival rate was 97.9% (95% confidence interval, 89.9-100) for the direct lateral approach and 97.2% (95% confidence interval, 93.9-99.3) for the posterolateral approach. This study indicates both approaches offer excellent pain reduction and return to function after Birmingham hip resurfacing with no difference in survival or in the incidence of complications. An 8-year survival rate of 97% can be achieved using either the posterolateral approach or the direct lateral approach. LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guidelines for authors for a complete description of levels of evidence.

Metal-on-metal hip resurfacing in osteonecrosis of the femoral head.

BACKGROUND: The treatment of end-stage osteonecrosis of the femoral head remains a challenge to the orthopaedic surgeon. Historically, total hip arthroplasty for this condition has been associated with poor rates of survival and function when compared with total hip arthroplasty for the treatment of osteoarthritis. The purpose of this study was to determine the medium-term clinical and radiographic results of metal-on-metal hip resurfacing arthroplasty in patients with end-stage osteonecrosis of the femoral head. METHODS: From June 1994 to March 2004, a consecutive single-surgeon series of seventy-three hip resurfacing procedures were performed in sixty patients for the treatment of end-stage osteonecrosis of the femoral head. The cohort included forty-two men (ten of whom had a bilateral resurfacing) and eighteen women (three of whom had a bilateral resurfacing). The mean age was forty-three years (range, seventeen to sixty-nine years). A clinical and radiographic review was performed. RESULTS: There were four revision operations and one planned revision of the seventy-three hips during the follow-up period. Two of these revisions were necessitated by aseptic failure of the femoral component. This represents an overall survival rate of 93.2% at a mean of 6.1 years of follow-up (range, two to twelve years). CONCLUSIONS: On the basis of this study, metal-on-metal resurfacing of the hip for osteonecrosis can be considered a safe and effective form of surgery for this group of patients. Longer-term follow-up is required to confirm the expected continued success of this form of arthroplasty in this difficult-to-treat population. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions to Authors on jbjs.org for a complete description of levels of evidence.