Aims. The Birmingham Hip Resurfacing (BHR) arthroplasty has been used as a surgical treatment of coxarthrosis since 1997. We present 20-year results of 234 consecutive BHRs performed in our unit. Methods. Between 1999 and 2001, there were 217 patients: 142 males (65.4%), mean age 52 years (18 to 68) who had 234 implants (17 bilateral). They had patient-reported outcome measures collected, imaging (radiograph and ultrasound), and serum metal ion assessment. Survivorship analysis was performed using Kaplan-Meier estimates. Revision for any cause was considered as an endpoint for the analysis. Results. Mean follow-up was 20.9 years (19.3 to 22.4). Registry data revealed that 19 hips (8.1%) had been revised and 26 patients (12%) had died from causes unrelated to the BHR. Among the remaining 189 hips, 61% were available for clinical follow-up at 20 years (n = 115) and 70% of patients had biochemical follow-up (n = 132). The cumulative implant survival rate at 20 years for male patients was 96.5% (95% confidence interval (CI) 93.5 to 99.6), and for female patients 87% (95% CI 79.7 to 94.9). The difference was statistically significant (p = 0.029). The mean Oxford Hip Score, Hip disability and Osteoarthritis Outcome Score, and Forgotten Joint Score were 45 (29 to 48), 89 (43 to 100), and 84 (19 to 100), respectively. The mean scores for each of the five domains of the EuroQol five-dimension three-level questionnaire were 1.2, 1.0, 1.2, 1.3, and 1.1, and mean overall score 82.6 (50 to 100). Ultrasound showed no pseudotumour. Mean cobalt and chromium levels were 32.1 nmol/l (1 to 374) and 45.5 nmol/l (9 to 408), respectively. Conclusion. This study shows that BHRs provide excellent survivorship and functional outcomes in young male patients. At 20 years, soft-tissue imaging and serum metal ion studies suggest that a metal-on-metal resurfacing implant can be well tolerated in a group of young patients. Cite this article: Bone Joint J 2023;105-B(9):946–952

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. Cite this article: Bone Joint J 2024;106-B(6):540–547

Aims. It is not known whether change in patient-reported outcome measures (PROMs) over time can be predicted by factors present at surgery, or early follow-up. The aim of this study was to identify factors associated with changes in PROM status between two-year evaluation and medium-term follow-up. Patients and Methods. Patients undergoing Birmingham Hip Resurfacing completed the Veteran’s Rand 36 (VR-36), modified Harris Hip Score (mHHS), Tegner Activity Score, and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at two years and a minimum of three years. A change in score was assessed against minimal clinically important difference (MCID) and patient-acceptable symptom state (PASS) thresholds. Binary logistic regression was used to assess the relationship between patient factors and deterioration in PASS status between follow-ups. Results. Overall, 18% of patients reported reductions in mHHS total score exceeding MCID, and 21% reported similar reductions for WOMAC function scores. Nonetheless, almost all patients remained above PASS thresholds for WOMAC function (98%) and mHHS (93%). Overall, 66% of patients with mHHS scores < PASS at two years reported scores > PASS at latest follow-up. Conversely, 6% of patients deteriorated from > PASS to < PASS between follow-ups. Multivariable modelling indicated body mass index (BMI) > 27 kg/m. 2. , VR-36 Physical Component Score (PCS) < 51, VR-36 Mental Component Score (MCS) > 55, mHHS < 84 at two years, female sex, and bone graft use predicted these deteriorating patients with 79% accuracy and an area under the curve (AUC) of 0.84. Conclusion. Due to largely acceptable results at a later follow-up, extensive monitoring of multiple PROMs is not recommended for Birmingham Hip Resurfacing patients unless they report borderline or unacceptable hip function at two years, are female, are overweight, or received a bone graft during surgery. Cite this article: Bone Joint J 2019;101-B:1431–1437

Aims. The first aim of this study was to evaluate whether preoperative renal function is associated with postoperative changes in whole blood levels of metal ions in patients who have undergone a Birmingham Hip Resurfacing (BHR) arthroplasty with a metal-on-metal bearing. The second aim was to evaluate whether exposure to increased cobalt (Co) and chromium (Cr) levels for ten years adversely affected renal function. Methods. As part of a multicentre, prospective post-approval study, whole blood samples were sent to a single specialized laboratory to determine Co and Cr levels, and the estimated glomerular filtration rate (eGFR). The study included patients with 117 unrevised unilateral BHRs. There were 36 females (31%). The mean age of the patients at the time of surgery of 51.3 years (SD 6.5), and they all had preoperative one-, four-, five-, and ten-year laboratory data. The mean follow-up was 10.1 years (SD 0.2). Results. Median Co levels at one year postoperatively increased significantly compared with the preoperative values, by a factor of 9.7, from 0.13 to 1.26 ppb (p < 0.001), and the median Cr levels increased significantly by a factor of 2.5, from 0.60 to 1.50 ppb (p < 0.001). Lower preoperative eGFRs were associated with significantly larger increases in Co at one year compared with the preoperative levels (ρ = -0.26; p = 0.005), but there was no relationship between preoperative eGFRs and changes in Cr at one year (ρ = -0.13; p = 0.153). Metal levels remained relatively constant with the passage of time, with a median ten-year value of 1.12 ppb for Co and 1.29 ppb for Cr. There was no significant relationship between the Co and Cr levels at ten-year follow-up and the change in eGFR from the preoperative level to that at ten years (ρ = -0.02; p = 0.827 for Co; ρ = -0.008; p = 0.933 for Cr). Conclusion. Although patients with lower preoperative eGFRs tended to have larger increases in Co levels at one year, increased metal levels for patients who underwent unilateral BHR did not adversely affect renal function during the first ten postoperative years. Cite this article: Bone Joint J 2024;106-B(3 Supple A):44–50

The Articular Surface Replacement (ASR) hip resurfacing arthroplasty has a failure rate of 12.0% at five years, compared with 4.3% for the Birmingham Hip Resurfacing (BHR). We analysed 66 ASR and 64 BHR explanted metal-on-metal hip replacements with the aim of understanding their mechanisms of failure. We measured the linear wear rates of the acetabular and femoral components and analysed the clinical cause of failure, pre-revision blood metal ion levels and orientation of the acetabular component. There was no significant difference in metal ion levels (chromium, p = 0.82; cobalt, p = 0.40) or head wear rate (p = 0.14) between the two groups. The ASR had a significantly increased rate of wear of the acetabular component (p = 0.03) and a significantly increased occurrence of edge loading (p < 0.005), which can be attributed to differences in design between the ASR and BHR. The effects of differences in design on the in vivo wear rates are discussed: these may provide an explanation as to why the ASR is more sensitive to suboptimal positioning than the BHR

The early designs of hip resurfacing implants suffered high rates of early failure, making it impossible to obtain valuable mid-term radiostereophotogrammetric (RSA) results. The metal-on-metal Birmingham Hip Resurfacing arthroplasty has shown promising mid-term results and we present here the first mid-term RSA analysis of a hip resurfacing implant. The analysis was performed in 19 hips at five years post-operatively. The mean acetabular component translation and rotation, and femoral component translation were compared with the previous RSA measurements at two and six months, and one and two years. There was no statistical significance (t-test, p ≤ 0.05) between these consecutive movements, indicating the mid-term stability of the implant

A cadaver study using six pairs of lower limbs was conducted to investigate the accuracy of computer navigation and standard instrumentation for the placement of the Birmingham Hip Resurfacing femoral component. The aim was to place all the femoral components with a stem-shaft angle of 135°. The mean stem-shaft angle obtained in the standard instrumentation group was 127.7° (120° to 132°), compared with 133.3° (131° to 139°) in the computer navigation group (p = 0.03). The scatter obtained with computer-assisted navigation was approximately half that found using the conventional jig. Computer navigation was more accurate and more consistent in its placement of the femoral component than standard instrumentation. We suggest that image-free computer-assisted navigation may have an application in aligning the femoral component during hip resurfacing

The dysplasia cup, which was devised as an adjunct to the Birmingham Hip Resurfacing system, has a hydroxyapatite-coated porous surface and two supplementary neutralisation screws to provide stable primary fixation, permit early weight-bearing, and allow incorporation of morcellised autograft without the need for structural bone grafting. A total of 110 consecutive dysplasia resurfacing arthroplasties in 103 patients (55 men and 48 women) performed between 1997 and 2000 was reviewed with a minimum follow-up of six years. The mean age at operation was 47.2 years (21 to 62) and 104 hips (94%) were Crowe grade II or III. During the mean follow-up of 7.8 years (6 to 9.6), three hips (2.7%) were converted to a total hip replacement at a mean of 3.9 years (2 months to 8.1 years), giving a cumulative survival of 95.2% at nine years (95% confidence interval 89 to 100). The revisions were due to a fracture of the femoral neck, a collapse of the femoral head and a deep infection. There was no aseptic loosening or osteolysis of the acetabular component associated with either of the revisions performed for failure of the femoral component. No patient is awaiting a revision. The median Oxford hip score in 98 patients with surviving hips at the final review was 13 and the 10th and the 90th percentiles were 12 and 23, respectively

Few independent studies have reported the outcome of resurfacing arthroplasty of the hip. The aim of this study was to report the five-year clinical outcome and seven-year survival of an independent series. A total of 610 Birmingham Hip Resurfacing arthroplasties were performed in 532 patients with a mean age of 51.8 years (16.5 to 81.6). They were followed for between two and eight years; 107 patients (120 hips) had been followed up for more than five years. Two patients were lost to follow-up. At a minimum of five years’ follow-up, 79 of 85 hips (93%) had an excellent or good outcome according to the Harris hip score. The mean Oxford hip score was 16.1 points (. sd. 7.7) and the mean University of California Los Angeles activity score was 6.6 points (. sd. 1.9). There were no patients with definite radiological evidence of loosening or of narrowing of the femoral neck exceeding 10% of its width. There were 23 revisions (3.8%), giving an overall survival of 95% (95% confidence interval 85.3 to 99.2) at seven years. Fractured neck of femur in 12 hips was the most common indication for revision, followed by aseptic loosening in four. In three hips (three patients) (0.5%), failure was possibly related to metal debris. Considering that these patients are young and active these results are good, and support the use of resurfacing. Further study is needed to address the early failures, particularly those related to fracture and metal debris

Aims

The aim of this study was to assess the functional gain achieved following hip resurfacing arthroplasty (HRA).

We present the clinical results and survivorship of consecutive 100 Birmingham Hip Resurfacings in 90 patients at a minimum follow-up of ten years. All procedures were carried out by an independent surgeon who commenced a prospective study in 1998. Patients were assessed clinically using the Western Ontario and McMaster Universities osteoarthritis index, Short-Form 36, Harris hip score and University of California, Los Angeles activity score. Radiological analysis was performed by an independent observer and blood metal ion levels concentrations were measured at ten years post-operatively in 62 patients. The median acetabular component inclination was 46.2° (34° to 59°) and anteversion 11.0° (0° to 30°). The median chromium concentration in the unilateral group was 1.74 (0.41 to 15.23) and for the bilateral group was 2.98 (1.57 to 18.01). The equivalent values for cobalt were 1.67 (0.54 to 20.4) and 1.88 (1.38 to 19.32).

In total there were eight failures giving an overall survival at ten years of 92% (95% confidence interval (CI) 86.7 to 97.3). BHR in male patients had an improved survivorship of 94.6% (95% CI 89.4 to 100) compared with females at 84.6% (95% CI 70.7 to 98.5), but this did not reach statistical significance (p = 0.119). Four of the nine BHRs with a bearing diameter of 42 mm failed.

The overall results were consistent with data produced from other centres in that the clinical outcome of large male patients was extremely encouraging, whereas the survival of the smaller joints was less satisfactory.

We describe a patient who sustained a peri-prosthetic fracture of the femoral neck two weeks after undergoing a resurfacing procedure for osteoarthritis of the hip. The fracture was minimally displaced and a satisfactory outcome was obtained following conservative treatment.

Modern metal-on-metal hip resurfacing has been widely performed in the United Kingdom for over a decade. However, the literature reports conflicting views of the benefits: excellent medium- to long-term results with some brands in specific subgroups, but high failure rates and local soft-tissue reactions in others. The National Joint Registry for England and Wales (NJR) has collected data on all hip resurfacings performed since 2003. This retrospective cohort study recorded survival time to revision from a resurfacing procedure, exploring risk factors independently associated with failure. All patients with a primary diagnosis of osteoarthritis who underwent resurfacing between 2003 and 2010 were included in the analyses. Cox’s proportional hazard models were used to analyse the extent to which the risk of revision was related to patient, surgeon and implant covariates. A total of 27 971 hip resurfacings were performed during the study period, of which 1003 (3.59%) underwent revision surgery. In the final adjusted model, we found that women were at greater risk of revision than men (hazard ratio (HR) = 1.30, p = 0.007), but the risk of revision was independent of age. Of the implant-specific predictors, five brands had a significantly greater risk of revision than the Birmingham Hip Resurfacing (BHR) (ASR: HR = 2.82, p < 0.001, Conserve: HR = 2.03, p < 0.001, Cormet: HR = 1.43, p = 0.001, Durom: HR = 1.67, p < 0.001, Recap: HR = 1.58, p = 0.007). Smaller femoral head components were also significantly more likely to require revision (≤ 44 mm: HR = 2.14, p < 0.001, 45 to 47 mm: HR = 1.48, p = 0.001) than medium or large heads, as were operations performed by low-volume surgeons (HR = 1.36, p <  0.001). Once these influences had been removed, in 4873 male patients < 60 years old undergoing resurfacing with a BHR, the five-year estimated risk of revision was 1.59%. In summary, after adjustment for a range of covariates we found that there were significant differences in the rate of failure between brands and component sizes. Younger male patients had good five-year implant survival when the BHR was used

Aims. Metal-on-metal hip resurfacing (MoM-HR) has seen decreased usage due to safety and longevity concerns. Joint registries have highlighted the risks in females, smaller hips, and hip dysplasia. This study aimed to identify if reported risk factors are linked to revision in a long-term follow-up of MoM-HR performed by a non-designer surgeon. Methods. A retrospective review of consecutive MoM hip arthroplasties (MoM-HRAs) using Birmingham Hip Resurfacing was conducted. Data on procedure side, indication, implant sizes and orientation, highest blood cobalt and chromium ion concentrations, and all-cause revision were collected from local and UK National Joint Registry records. Results. A total of 243 hips (205 patients (163 male, 80 female; mean age at surgery 55.3 years (range 25.7 to 75.3)) with MoM-HRA performed between April 2003 and October 2020 were included. Mean follow-up was 11.2 years (range 0.3 to 17.8). Osteoarthritis was the most common indication (93.8%), and 13 hips (5.3%; 7M:6F) showed dysplasia (lateral centre-edge angle < 25°). Acetabular cups were implanted at a median of 45.4° abduction (interquartile range 41.9° - 48.3°) and stems neutral or valgus to the native neck-shaft angle. In all, 11 hips (4.5%; one male, ten females) in ten patients underwent revision surgery at a mean of 7.4 years (range 2.8 to 14.2), giving a cumulative survival rate of 94.8% (95% confidence interval (CI) 91.6% to 98.0%) at ten years, and 93.4% (95% CI 89.3% to 97.6%) at 17 years. For aseptic revision, male survivorship was 100% at 17 years, and 89.6% (95% CI 83.1% to 96.7%) at ten and 17 years for females. Increased metal ion levels were implicated in 50% of female revisions, with the remaining being revised for unexplained pain or avascular necrosis. Conclusion. The Birmingham MoM-HR showed 100% survivorship in males, exceeding the National Institute for Health and Care Excellence ‘5% at ten years’ threshold. Female sex and small component sizes are independent risk factors. Dysplasia alone is not a contraindication to resurfacing. Cite this article: Bone Jt Open 2023;4(11):853–858

We sought to establish the incidence of joint failure secondary to adverse reaction to metal debris (ARMD) following metal-on-metal hip resurfacing in a large, three surgeon, multicentre study involving 4226 hips with a follow-up of 10 to 142 months. Three implants were studied: the Articular Surface Replacement; the Birmingham Hip Resurfacing; and the Conserve Plus. Retrieved implants underwent analysis using a co-ordinate measuring machine to determine volumetric wear. There were 58 failures associated with ARMD. The median chromium and cobalt concentrations in the failed group were significantly higher than in the control group (p < 0.001). Survival analysis showed a failure rate in the patients with Articular Surface Replacement of 9.8% at five years, compared with < 1% at five years for the Conserve Plus and 1.5% at ten years for the Birmingham Hip Resurfacing. Two ARMD patients had relatively low wear of the retrieved components. Increased wear from the metal-on-metal bearing surface was associated with an increased rate of failure secondary to ARMD. However, the extent of tissue destruction at revision surgery did not appear to be dose-related to the volumetric wear

Aims. The aim of this study was to report the implant survival and patient-reported outcome measures (PROMs) in a consecutive series of patients aged less than 50 years at the time of arthroplasty using the Birmingham Hip Resurfacing system (BHR), with a minimum follow-up of ten years. Patients and Methods. A total of 226 patients with osteoarthritis of the hip, who underwent BHR and presented to a single surgeon, were included in the study. Survival of the implant was confirmed by cross-checking with the Australian Orthopaedic Association National Joint Replacement Registry. Kaplan–Meier survival curves with 95% confidence intervals (CIs) were constructed. Pre- and postoperative PROMs were compared with t-tests, and postoperative scores were compared using anchor analysis with age and gender matched normative data. Results. At median follow-up of 12 years (interquartile range (IQR) 10 to 13), six BHRs were revised, with a cumulative rate of survival of 96.8% (95% confidence interval (CI) 94.2 to 99.4) at 15 years, and with a significantly lower (p = 0.019) cumulative rate of revision than the national average for the same device at ten years. Most revisions (n = 4) were undertaken early, less than three years postoperatively, and occurred in women. Patient-reported general health (Veteran’s Rand-36), disease state (Western Ontario and McMaster Universities Osteoarthritis Index), function (modified Harris Hip Score) and level of activity (Tegner activity score) maintained significant (p < 0.01 for each) improvements beyond ten years postoperatively and were equal to, or exceeded, age- and gender-matched normative data in more than 80% of the patients. Conclusion. Longer term PROMs after BHR, from a single surgeon, for patients aged less than 50 years remain under-reported. We found that the outcome after a BHR, at a minimum of ten years postoperatively, remained satisfactory, particularly for self-reported hip function

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

We describe the findings at six years in an ongoing prospective clinicoradiological and metal ion study in a cohort of 26 consecutive male patients with unilateral Birmingham Hip Resurfacing arthroplasties with one of two femoral head sizes (50 mm and 54 mm). Their mean age was 52.9 years (29 to 67). We have previously shown an early increase in the 24-hour urinary excretion of metal ions, reaching a peak at six months (cobalt) and one year (chromium) after operation. Subsequently there is a decreasing trend in excretion of both cobalt and chromium. The levels of cobalt and chromium in whole blood also show a significant increase at one year, followed by a decreasing trend until the sixth year

There have been no large comparative studies of the blood levels of metal ions after implantation of commercially available hip resurfacing devices which have taken into account the effects of femoral size and inclination and anteversion of the acetabular component. We present the results in 90 patients with unilateral articular surface replacement (ASR) hip resurfacings (mean time to blood sampling 26 months) and 70 patients with unilateral Birmingham Hip Resurfacing (BHR) implants (mean time 47 months). The whole blood and serum chromium (Cr) and cobalt (Co) concentrations were inversely related to the size of the femoral component in both groups (p < 0.05). Cr and Co were more strongly influenced by the position of the acetabular component in the case of the ASR, with an increase in metal ions observed at inclinations > 45° and anteversion angles of < 10° and > 20°. These levels were only increased in the BHR group when the acetabular component was implanted with an inclination > 55°. A significant relationship was identified between the anteversion of the BHR acetabular component and the levels of Cr and Co (p < 0.05 for Co), with an increase observed at anteversion angles < 10° and > 20°. The median whole blood and serum Cr concentrations of the male ASR patients were significantly lower than those of the BHR men (p < 0.001). This indicates that reduced diametral clearance may equate to a reduction in metal ion concentrations in larger joints with satisfactory orientation of the acetabular component

Hip resurfacing is being performed more frequently in the United Kingdom. The possible benefits include more accurate restoration of leg length, femoral offset and femoral anteversion than occurs after total hip arthroplasty (THA). We compared anteroposterior radiographs from 26 patients who had undergone hybrid THA (uncemented cup/cemented stem), with 28 who had undergone Birmingham Hip Resurfacing arthroplasty (BHR). We measured the femoral offset, femoral length, acetabular offset and acetabular height with reference to the normal contralateral hip. The data were analysed by paired t-tests. There was a significant reduction in femoral offset (p = 0.0004) and increase in length (p = 0.001) in the BHR group. In the THA group, there was a significant reduction in acetabular offset (p = 0.0003), but femoral offset and overall hip length were restored accurately. We conclude that hip resurfacing does not restore hip mechanics as accurately as THA

This study compared the demographic, clinical and patient-reported outcomes after total hip replacement (THR) and Birmingham Hip Resurfacing (BHR) carried out by a single surgeon. Patients completed a questionnaire that included the WOMAC, SF-36 scores and comorbid medical conditions. Data were collected before operation and one year after. The outcome scores were adjusted for age, gender, comorbid conditions and, at one year, for the pre-operative scores. There were 214 patients with a THR and 132 with a BHR. Patients with a BHR were significantly younger (49 vs 67 years, p < 0.0001), more likely to be male (68% vs 42% of THR, p < 0.0001) and had fewer comorbid conditions (1.3 vs 2.0, p < 0.0001). Before operation there was no difference in WOMAC and SF-36 scores, except for function, in which patients awaiting THR were worse than those awaiting a BHR. At one year patients with a BHR reported significantly better WOMAC pain scores (p = 0.04) and in all SF-36 domains (p < 0.05). Patients undergoing BHR report a significantly greater improvement in general health compared with those with a THR

We report the outcome at a minimum of five years of 110 consecutive metal-on-metal Birmingham Hip Resurfacing arthroplasties in 98 patients. The procedures were performed between October 1999 and June 2002 by one surgeon. All patients were followed up clinically and radiologically. The mean follow-up was 71 months (60 to 93). Revision of either component was defined as failure. The mean Harris Hip score at follow-up was 96.4 (53 to 100). The mean Oxford hip score was 41.9 (16 to 57) pre-operatively and 15.4 (12 to 49) post-operatively (p < 0.001). The mean University of California Los Angeles activity score was 3.91 (1 to 10) pre-operatively and 7.5 (4 to 10) post-operatively (p < 0.001). There were four failures giving a survival at five years of 96.3% (95% confidence interval 92.8 to 99.8). When applying a new method to estimate narrowing of the femoral neck we identified a 10% thinning of the femoral neck in 16 hips (14.5%), but the relevance of this finding to the long-term outcome remains unclear. These good medium-term results from an independent centre confirm the original data from Birmingham

Early failure associated with adverse reactions to metal debris is an emerging problem after hip resurfacing but the exact mechanism is unclear. We analysed our entire series of 660 metal-on-metal resurfacings (Articular Surface Replacement (ASR) and Birmingham Hip Resurfacing (BHR)) and large-bearing ASR total hip replacements, to establish associations with metal debris-related failures. Clinical and radiological outcomes, metal ion levels, explant studies and lymphocyte transformation tests were performed. A total of 17 patients (3.4%) were identified (all ASR bearings) with adverse reactions to metal debris, for which revision was required. This group had significantly smaller components, significantly higher acetabular component anteversion, and significantly higher whole concentrations of blood and joint chromium and cobalt ions than asymptomatic patients did (all p < 0.001). Post-revision lymphocyte transformation tests on this group showed no reactivity to chromium or cobalt ions. Explants from these revisions had greater surface wear than retrievals for uncomplicated fractures. The absence of adverse reactions to metal debris in patients with well-positioned implants usually implies high component wear. Surgeons must consider implant design, expected component size and acetabular component positioning in order to reduce early failures when performing large-bearing metal-on-metal hip resurfacing and replacement

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

Aims

Hip resurfacing remains a potentially valuable surgical procedure for appropriately-selected patients with optimised implant choices. However, concern regarding high early failure rates continues to undermine confidence in use. A large contributor to failure is adverse local tissue reactions around metal-on-metal (MoM) bearing surfaces. Such phenomena have been well-explored around MoM total hip arthroplasties, but comparable data in equivalent hip resurfacing procedures is lacking. In order to define genetic predisposition, we performed a case-control study investigating the role of human leucocyte antigen (HLA) genotype in the development of pseudotumours around MoM hip resurfacings.

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.

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).

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.

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.

Aims

The purpose of this study is to examine six types of bearing surfaces implanted at a single institution over three decades to determine whether the reasons for revision vary among the groups and how long it takes to identify differences in survival.

Aims

We wished to investigate the influence of metal debris exposure on the subsequent immune response and resulting soft-tissue injury following metal-on-metal (MoM) hip arthroplasty. Some reports have suggested that debris generated from the head-neck taper junction is more destructive than equivalent doses from metal bearing surfaces.

Aims

Surface replacement arthroplasty (SRA), compared with traditional total hip arthroplasty (THA), is more expensive and carries unique concern related to metal ions production and hypersensitivity. Additionally, SRA is a more demanding procedure with a decreased margin for error compared with THA. To justify its use, SRA must demonstrate comparable component survival and some clinical advantages. We therefore performed a systematic literature review to investigate the differences in complication rates, patient-reported outcomes, stress shielding, and hip biomechanics between SRA and THA.

Objectives

We investigated the reliability of the cobalt-chromium (CoCr) synovial joint fluid ratio (JFR) in identifying the presence of a severe aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL) response and/or suboptimal taper performance (SOTP) following metal-on-metal (MoM) hip arthroplasty. We then examined the possibility that the CoCr JFR may influence the serum partitioning of Co and Cr.

Objectives

The high revision rates of the DePuy Articular Surface Replacement (ASR) and the DePuy ASR XL (the total hip arthroplasty (THA) version) have led to questions over the viability of metal-on-metal (MoM) hip joints. Some designs of MoM hip joint do, however, have reasonable mid-term performance when implanted in appropriate patients. Investigations into the reasons for implant failure are important to offer help with the choice of implants and direction for future implant designs. One way to assess the performance of explanted hip prostheses is to measure the wear (in terms of material loss) on the joint surfaces.

Metal-on-metal hip resurfacing was performed for developmental dysplasia in 96 hips in 85 patients, 78 in women and 18 in men, with a mean age at the time of surgery of 43 years (14 to 65). These cases were matched for age, gender, operating surgeon and date of operation with a group of patients with primary osteoarthritis who had been treated by resurfacing, to provide a control group of 96 hips (93 patients). A clinical and radiological follow-up study was performed. The dysplasia group were followed for a mean of 4.4 years (2.0 to 8.5) and the osteoarthritis group for a mean of 4.5 years (2.2 to 9.4). Of the dysplasia cases, 17 (18%) were classified as Crowe grade III or IV.

There were five (5.2%) revisions in the dysplasia group and none in the osteoarthritic patients. Four of the failures were due to acetabular loosening and the other sustained a fracture of the neck of femur. There was a significant difference in survival between the two groups (p = 0.02). The five-year survival was 96.7% (95% confidence interval 90.0 to 100) for the dysplasia group and 100% (95% confidence interval 100 to 100) for the osteoarthritic group. There was no significant difference in the median Oxford hip score between the two groups at any time during the study.

The medium-term results of metal-on-metal hip resurfacing in all grades of developmental dysplasia are encouraging, although they are significantly worse than in a group of matched patients with osteoarthritis treated in the same manner.

A retrospective study was conducted to investigate the changes in metal ion levels in a consecutive series of Birmingham Hip Resurfacings (BHRs) at a minimum ten-year follow-up. We reviewed 250 BHRs implanted in 232 patients between 1998 and 2001. Implant survival, clinical outcome (Harris hip score), radiographs and serum chromium (Cr) and cobalt (Co) ion levels were assessed.

Of 232 patients, 18 were dead (five bilateral BHRs), 15 lost to follow-up and ten had been revised. The remaining 202 BHRs in 190 patients (136 men and 54 women; mean age at surgery 50.5 years (17 to 76)) were evaluated at a minimum follow-up of ten years (mean 10.8 years (10 to 13.6)). The overall implant survival at 13.2 years was 92.4% (95% confidence interval 90.8 to 94.0). The mean Harris hip score was 97.7 (median 100; 65 to 100). Median and mean ion levels were low for unilateral resurfacings (Cr: median 1.3 µg/l, mean 1.95 µg/l (< 0.5 to 16.2); Co: median 1.0 µg/l, mean 1.62 µg/l (< 0.5 to 17.3)) and bilateral resurfacings (Cr: median 3.2 µg/l, mean 3.46 µg/l (< 0.5 to 10.0); Co: median 2.3 µg/l, mean 2.66 µg/l (< 0.5 to 9.5)). In 80 unilateral BHRs with sequential ion measurements, Cr and Co levels were found to decrease significantly (p < 0.001) from the initial assessment at a median of six years (4 to 8) to the last assessment at a median of 11 years (9 to 13), with a mean reduction of 1.24 µg/l for Cr and 0.88 µg/l for Co. Three female patients had a > 2.5 µg/l increase of Co ions, associated with head sizes ≤ 50 mm, clinical symptoms and osteolysis. Overall, there was no significant difference in change of ion levels between genders (Cr, p = 0.845; Co, p = 0.310) or component sizes (Cr, p = 0.505; Co, p = 0.370). Higher acetabular component inclination angles correlated with greater change in ion levels (Cr, p = 0.013; Co, p = 0.002). Patients with increased ion levels had lower Harris hip scores (p = 0.038).

In conclusion, in well-functioning BHRs the metal ion levels decreased significantly at ten years. An increase > 2.5 µg/l was associated with poor function.

Cite this article: Bone Joint J 2013;95-B:1332–8.

Objectives

We have encountered patients who developed large joint fluid collections with massive elevations in chromium (Cr) and cobalt (Co) concentrations following metal-on-metal (MoM) hip arthroplasties. In some cases, retrieval analysis determined that these ion concentrations could not be explained simply by the wear rates of the components. We hypothesized that these effects may be associated with aseptic lymphocyte-dominated vasculitis-associated lesion (ALVAL).

Fracture of the neck of the femur after resurfacing arthroplasty usually leads to failure and conversion to a total hip replacement. We describe an intracapsular fracture of the femoral neck sustained after hip resurfacing which was treated by cannulated screws, resulting in union and retention of the resurfacing implant. The result at follow-up three years later was very satisfactory with a Harris hip score of 99.

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.

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.

Blood metal ions have been widely used to investigate metal-on-metal hip replacements, but their ability to discriminate between well-functioning and failed hips is not known. The Medicines and Healthcare products Regulatory Agency (MHRA) has suggested a cut-off level of 7 parts per billion (ppb).

We performed a pair-matched, case-control study to investigate the sensitivity and specificity of blood metal ion levels for diagnosing failure in 176 patients with a unilateral metal-on-metal hip replacement. We recruited 88 cases with a pre-revision, unexplained failed hip and an equal number of matching controls with a well-functioning hip. We investigated the 7 ppb cut-off level for the maximum of cobalt or chromium and determined optimal mathematical cut-off levels from receiver-operating characteristic curves.

The 7 ppb cut-off level for the maximum of cobalt or chromium had a specificity of 89% and sensitivity 52% for detecting a pre-operative unexplained failed metal on metal hip replacement. The optimal cut-off level for the maximum of cobalt or chromium was 4.97 ppb and had sensitivity 63% and specificity 86%.

Blood metal ions had good discriminant ability to separate failed from well-functioning hip replacements. The MHRA cut-off level of 7 ppb provides a specific test but has poor sensitivity.

Hip resurfacing has been proposed as an alternative to traditional total hip arthroplasty in young, active patients. Much has been learned following the introduction of metal-on-metal resurfacing devices in the 1990s. The triad of a well-designed device, implanted accurately, in the correct patient has never been more critical than with these implants.

Following Food and Drug Administration approval in 2006, we studied the safety and effectiveness of one hip resurfacing device (Birmingham Hip Resurfacing) at our hospital in a large, single-surgeon series. We report our early to mid–term results in 1333 cases followed for a mean of 4.3 years (2 to 5.7) using a prospective, observational registry. The mean patient age was 53.1 years (12 to 84); 70% were male and 91% had osteoarthritis. Complications were few, including no dislocations, no femoral component loosening, two femoral neck fractures (0.15%), one socket loosening (0.08%), three deep infections (0.23%), and three cases of metallosis (0.23%). There were no destructive pseudotumours.

Overall survivorship at up to 5.7 years was 99.2%. Aseptic survivorship in males under the age of 50 was 100%. We believe this is the largest United States series of a single surgeon using a single resurfacing system.

Cite this article: Bone Joint J 2016;98-B (1 Suppl A):10–13.

Aims

Surgeons have commonly used modular femoral heads and stems from different manufacturers, although this is not recommended by orthopaedic companies due to the different manufacturing processes.

We compared the rate of corrosion and rate of wear at the trunnion/head taper junction in two groups of retrieved hips; those with mixed manufacturers (MM) and those from the same manufacturer (SM).

We retrospectively analysed concentrations of chromium and cobalt ions in samples of synovial fluid and whole blood taken from a group of 92 patients with failed current-generation metal-on-metal hip replacements. We applied acid oxidative digestion to our trace metal analysis protocol, which found significantly higher levels of metal ion concentrations in blood and synovial fluid than a non-digestive method. Patients were subcategorised by mode of failure as either ‘unexplained pain’ or ‘defined causes’. Using this classification, chromium and cobalt ion levels were present over a wider range in synovial fluid and not as strongly correlated with blood ion levels as previously reported. There was no significant difference between metal ion concentrations and manufacturer of the implant, nor femoral head size below or above 50 mm. There was a moderately positive correlation between metal ion levels and acetabular component inclination angle as measured on three-dimensional CT imaging.

Our results suggest that acid digestion of samples of synovial fluid samples is necessary to determine metal ion concentrations accurately so that meaningful comparisons can be made between studies.

The presence of pseudotumours, which are soft-tissue masses relating to the hip, after metal-on-metal hip resurfacing arthroplasty has been associated with elevated levels of metal ions in serum, suggesting that pseudotumours occur when there is increased wear. We aimed to quantify the wear in vivo of implants revised for pseudotumours (eight) and of a control group of implants (22) revised for other reasons of failure.

We found that the implant group with pseudotumours had a significantly higher rate of median linear wear of the femoral component at 8.1 μm/year (2.75 to 25.4) than the 1.79 μm/year (0.82 to 4.15; p = 0.002) of the non-pseudotumour group. For the acetabular component a significantly higher rate of median linear wear of 7.36 μm/year (1.61 to 24.9) was observed in the pseudotumour group compared with 1.28 μm/year (0.81 to 3.33, p = 0.001) in the other group. Wear of the acetabular component in the pseudotumour group always involved the edge of the implant, indicating that edge-loading had occurred.

Our findings are the first direct evidence that pseudotumour is associated with increased wear at the metal-on-metal articulation. Furthermore, edge-loading with the loss of fluid-film lubrication may be an important mechanism of generation of wear in patients with a pseudotumour.

Pseudotumours are a rare complication of hip resurfacing. They are thought to be a response to metal debris which may be caused by edge loading due to poor orientation of the acetabular component. Our aim was to determine the optimal acetabular orientation to minimise the risk of pseudotumour formation.

We matched 31 hip resurfacings revised for pseudotumour formation with 58 controls who had a satisfactory outcome from this procedure. The radiographic inclination and anteversion angles of the acetabular component were measured on anteroposterior radiographs of the pelvis using Einzel-Bild-Roentgen-Analyse software. The mean inclination angle (47°, 10° to 81°) and anteversion angle (14°, 4° to 34°) of the pseudotumour cases were the same (p = 0.8, p = 0.2) as the controls, 46° (29° to 60°) and 16° (4° to 30°) respectively, but the variation was greater. Assuming an accuracy of implantation of ± 10° about a target position, the optimal radiographic position was found to be approximately 45° of inclination and 20° of anteversion. The incidence of pseudotumours inside the zone was four times lower (p = 0.007) than outside the zone.

In order to minimise the risk of pseudotumour formation we recommend that surgeons implant the acetabular component at an inclination of 45° (± 10) and anteversion of 20° (± 10) on post-operative radiographs. Because of differences between the radiographic and the operative angles, this may be best achieved by aiming for an inclination of 40° and an anteversion of 25°.

Lately, concerns have arisen following the use of large metal-on-metal bearings in hip replacements owing to reports of catastrophic soft-tissue reactions resulting in implant failure and associated complications. This review examines the literature and contemporary presentations on current clinical dilemmas in metal-on-metal hip replacement.

We report 17 patients (20 hips) in whom metal-on-metal resurfacing had been performed and who presented with various symptoms and a soft-tissue mass which we termed a pseudotumour. Each patient underwent plain radiography and in some, CT, MRI and ultrasonography were also performed. In addition, histological examination of available samples was undertaken.

All the patients were women and their presentation was variable. The most common symptom was discomfort in the region of the hip. Other symptoms included spontaneous dislocation, nerve palsy, a noticeable mass or a rash. The common histological features were extensive necrosis and lymphocytic infiltration. To date, 13 of the 20 hips have required revision to a conventional hip replacement. Two are awaiting revision.

We estimate that approximately 1% of patients who have a metal-on-metal resurfacing develop a pseudotumour within five years. The cause is unknown and is probably multifactorial. There may be a toxic reaction to an excess of particulate metal wear debris or a hypersensitivity reaction to a normal amount of metal debris. We are concerned that with time the incidence of these pseudotumours may increase. Further investigation is required to define their cause.

Wear of metal-on-metal bearings causes elevated levels of cobalt and chromium in blood and body fluids. Metal-on-metal bearings have two distinct wear phases. In the early phase, the wear rate is high. Later, it decreases and the bearing enters a steady-state phase. It is expected that as the wear rates decline, the level of cobalt detected in plasma will also decrease. We studied the baseline and exercise-related cobalt rise in 21 patients (13 men and eight women) with a mean age of 54 years (38 to 80) who had undergone successful hip resurfacing at a mean of 44 months (10 to 96) earlier. Our results showed that circulating baseline cobalt levels were not significantly correlated with the time since implantation (r = 0.08, p = 0.650). By contrast, the exercise-related cobalt rise was directly correlated with the inclination angle of the acetabular component (r = 0.47, p = 0.032) and inversely correlated with the time since implantation (r = −0.5, p = 0.020).

Inclination of the acetabular component should be kept less than 40° to decrease the production of wear debris.

Metal-on-metal hip resurfacing is commonly performed for osteoarthritis in young active patients. We have observed cystic or solid masses, which we have called inflammatory pseudotumours, arising around these devices. They may cause soft-tissue destruction with severe symptoms and a poor outcome after revision surgery. The aim of this study was to determine the incidence of and risk factors for pseudotumours that are serious enough to require revision surgery.

Since 1999, 1419 metal-on-metal hip resurfacings have been implanted by our group in 1224 patients; 1.8% of the patients had a revision for pseudotumour. In this series the Kaplan-Meier cumulative revision rate for pseudotumour increased progressively with time. At eight years, in all patients, it was 4% (95% confidence interval (CI) 2.2 to 5.8). Factors significantly associated with an increase in revision rate were female gender (p < 0.001), age under 40 (p = 0.003), small components (p = 0.003), and dysplasia (p = 0.019), whereas implant type was not (p = 0.156). These factors were inter-related, however, and on fitting a Cox proportional hazard model only gender (p = 0.002) and age (p = 0.024) had a significant independent influence on revision rate; size nearly reached significance (p = 0.08). Subdividing the cohort according to significant factors, we found that the revision rate for pseudotumours in men was 0.5% (95% CI 0 to 1.1) at eight years wheras in women over 40 years old it was 6% (95% CI 2.3 to 10.1) at eight years and in women under 40 years it was 13.1% at six years (95% CI 0 to 27) (p < 0.001).

We recommend that resurfacings are undertaken with caution in women, particularly those under 40 years of age but they remain a good option in young men. Further work is required to understand the aetiology of pseudotumours so that this complication can be avoided.

Hip simulators have been used for ten years to determine the tribological performance of large-head metal-on-metal devices using traditional test conditions. However, the hip simulator protocols were originally developed to test metal-on-polyethylene devices. We have used patient activity data to develop a more physiologically relevant test protocol for metal-on-metal devices. This includes stop/start motion, a more appropriate walking frequency, and alternating kinetic and kinematic profiles.

There has been considerable discussion about the effect of heat treatments on the wear of metal-on-metal cobalt chromium molybdenum (CoCrMo) devices. Clinical studies have shown a higher rate of wear, levels of metal ions and rates of failure for the heat-treated metal compared to the as-cast metal CoCrMo devices. However, hip simulator studies in vitro under traditional testing conditions have thus far not been able to demonstrate a difference between the wear performance of these implants.

Using a physiologically relevant test protocol, we have shown that heat treatment of metal-on-metal CoCrMo devices adversely affects their wear performance and generates significantly higher wear rates and levels of metal ions than in as-cast metal implants.

Aims

The aims of this study were to compare the diagnostic test characteristics of ultrasound alone, metal artefact reduction sequence MRI (MARS-MRI) alone, and ultrasound combined with MARS-MRI for identifying intra-operative pseudotumours in metal-on-metal hip resurfacing (MoMHR) patients undergoing revision surgery.

Abnormal wear of cobalt-containing metal-on-metal joints is associated with inflammatory pseudotumours. Cobalt ions activate human toll-like receptor 4 (TLR4), which normally responds to bacterial lipopolysaccharide (LPS) in sepsis. Activation of TLR4 by LPS increases the expression of chemokines IL-8 and CXCL10, which recruit leukocytes and activated T-cells, respectively. This study was designed to determine whether cobalt induces a similar inflammatory response to LPS by promoting the expression of IL-8 and CXCL10. A human monocytic cell line, derived from acute monocytic leukaemia, was treated with cobalt ions and expression of IL-8 and CXCL10 measured at mRNA and protein levels. Cobalt-treated macrophages showed a 60-fold increase in IL-8 mRNA, and an eightfold increase in production of the mature chemokine (both p < 0.001); expression of the CXCL10 gene and protein was also significantly increased by cobalt (both p < 0.001). Experiments were also performed in the presence of CLI-095, a TLR4-specific antagonist which abrogated the cobalt-mediated increase in IL-8 and CXCL10 expression.

These findings suggest that cobalt ions induce inflammation similar to that observed during sepsis by the simultaneous activation of two TLR4-mediated signalling pathways. These pathways result in increased production of IL-8 and CXCL10, and may be implicated in pseudotumour formation following metal-on-metal replacement.

Cite this article: Bone Joint J 2014; 96-B:1172–7.

The aim of this study was to evaluate the functional and oncological outcome of extracorporeally irradiated autografts used to reconstruct the pelvis after a P1/2 internal hemipelvectomy.

The study included 18 patients with a primary malignant bone tumour of the pelvis. There were 13 males and five females with a mean age of 24.8 years (8 to 62). Of these, seven had an osteogenic sarcoma, six a Ewing’s sarcoma, and five a chondrosarcoma. At a mean follow-up of 51.6 months (4 to 185), nine patients had died with metastatic disease while nine were free from disease. Local recurrence occurred in three patients all of whom eventually died of their disease. Deep infection occurred in three patients and required removal of their graft in two while the third underwent a hindquarter amputation for extensive flap necrosis.

The mean Musculoskeletal Tumor Society functional score of the 16 patients who could be followed-up for at least 12 months was 77% (50 to 90). Those 15 patients who completed the Toronto Extremity Salvage Score questionnaire had a mean score of 71% (53 to 85).

Extracorporeal irradiation and re-implantation of bone is a valid method of reconstruction after an internal hemipelvectomy. It has an acceptable morbidity and a functional outcome that compares favourably with other available reconstructive techniques.

Cite this article: Bone Joint J 2014;96-B:1404–10

This review examines the future of total hip arthroplasty, aiming to avoid past mistakes

Femoroacetabular impingement (FAI) is commonly associated with early hip arthritis. We reviewed our series of 1300 hip resurfacing procedures. More than 90% of our male patients, with an average age of 53 years, had cam impingement lesions. In this condition, there are anterior femoral neck osteophytes, and a retroverted femoral head on a normally anteverted neck. It is postulated that FAI results in collision of the anterior neck of the femur against the rim of the acetabulum, causing damage to the acetabular labrum and articular cartilage, resulting in osteoarthritis. Early treatment of FAI involves arthroscopic or open removal of bone from the anterior femoral neck, as well as repair or removal of labral tears. However, once osteoarthritis has developed, hip replacement or hip resurfacing is indicated. Hip resurfacing can re-orient the head and re-shape the neck. This helps to restore normal biomechanics to the hip, eliminate FAI, and improve range of motion. Since many younger men with hip arthritis have FAI, and are also considered the best candidates for hip resurfacing, it is evident that resurfacing has a role in these patients.

In this paper, we will consider the current role of metal-on-metal bearings by looking at three subtypes of MoM hip arthroplasty separately: Hip resurfacing, large head (> 36 mm) MoM THA and MoM THA with traditional femoral head sizes.

The June 2012 Hip & Pelvis Roundup³⁶⁰ looks at: whether metal-on-metal is really such a disaster; resurfacings with unexplained pain; large heads and high ion levels; hip arthroscopy for FAI; the inaccuracy of clinical tests for impingement; arthroscopic lengthening of iliopsoas; the OA hip; the injured hamstring – football’s most common injury; an algorithm for hip fracture surgery; and sparing piriformis at THR.

The purpose of this study was to compare the amount of acetabular bone removed during hip resurfacing (HR) and cementless total hip replacement (THR), after controlling for the diameter of the patient’s native femoral head. Based on a power analysis, 64 consecutive patients (68 hips) undergoing HR or THR were prospectively enrolled in the study. The following data were recorded intra-operatively: the diameter of the native femoral head, the largest reamer used, the final size of the acetabular component, the size of the prosthetic femoral head and whether a decision was made to increase the size of the acetabular component in order to accommodate a larger prosthetic femoral head. Results were compared using two-sided, independent samples Student’s t-tests. A statistically significant difference was seen in the mean ratio of the size of the acetabular component to the diameter of the native femoral head (HR: 1.05 (sd 0.04) versus THR: 1.09 (sd 0.05); p <  0.001) and largest acetabular reamer used to the diameter of the native femoral head (HR: 1.03 (sd 0.04) versus THR: 1.09 (sd 0.05); p < 0.001). The ratios varied minimally when the groups were subdivided by gender, age and obesity. The decision to increase the size of the acetabular component to accommodate a larger femoral head occurred more often in the THR group (27% versus 9%). Despite the emphasis on avoiding damage to the femoral neck during HR, the ratio of the size of the acetabular component to the diameter of the native femoral head was larger in cementless THR than in HR.

Despite the worldwide usage of the cemented Contemporary acetabular component (Stryker), no published data are available regarding its use in patients aged < 50 years. We undertook a mid- to long-term follow-up study, including all consecutive patients aged < 50 years who underwent a primary total hip replacement using the Contemporary acetabular component with the Exeter cemented stem between January 1999 and January 2006. There were 152 hips in 126 patients, 61 men and 65 women, mean age at surgery 37.6 years (16 to 49 yrs). One patient was lost to follow-up.

Mean clinical follow-up of all implants was 7.6 years (0.9 to 12.0). All clinical questionnaire scores, including Harris hip score, Oxford hip score and several visual analogue scales, were found to have improved. The eight year survivorship of all acetabular components for the endpoints revision for any reason or revision for aseptic loosening was 94.4% (95% confidence interval (CI) 89.2 to 97.2) and 96.4% (95% CI 91.6 to 98.5), respectively. Radiological follow-up was complete for 146 implants. The eight year survival for the endpoint radiological loosening was 93.1% (95% CI 86.2 to 96.6). Three surviving implants were considered radiologically loose but were asymptomatic. The presence of acetabular osteolysis (n = 17, 11.8%) and radiolucent lines (n = 20, 13.9%) in the 144 surviving cups indicates a need for continued observation in the second decade of follow-up in order to observe their influence on long-term survival.

The clinical and radiological data resulting in a ten-year survival rate > 90% in young patients support the use of the Contemporary acetabular component in this specific patient group.

Cite this article: Bone Joint J 2013;95-B:1617–25.

Plasma levels of cobalt and chromium ions and Metal Artefact Reduction Sequence (MARS)-MRI scans were performed on patients with 209 consecutive, unilateral, symptomatic metal-on-metal (MoM) hip arthroplasties. There was wide variation in plasma cobalt and chromium levels, and MARS-MRI scans were positive for adverse reaction to metal debris (ARMD) in 84 hips (40%). There was a significant difference in the median plasma cobalt and chromium levels between those with positive and negative MARS-MRI scans (p < 0.001). Compared with MARS-MRI as the potential reference standard for the diagnosis of ARMD, the sensitivity of metal ion analysis for cobalt or chromium with a cut-off of > 7 µg/l was 57%. The specificity was 65%, positive predictive value was 52% and the negative predictive value was 69% in symptomatic patients. A lowered threshold of > 3.5 µg/l for cobalt and chromium ion levels improved the sensitivity and negative predictive value to 86% and 74% but at the expense of specificity (27%) and positive predictive value (44%).

Metal ion analysis is not recommended as a sole indirect screening test in the surveillance of symptomatic patients with a MoM arthroplasty. The investigating clinicians should have a low threshold for obtaining cross-sectional imaging in these patients, even in the presence of low plasma metal ion levels.

Endoprosthetic replacement of the pelvis is one of the most challenging types of limb-salvage surgery, with a high rate of complications. In an attempt to reduce this and build greater versatility into the reconstruction process, a new type of pelvic endoprosthesis was developed in 2003, based on the old McKee-Farrar prosthesis. This study reviews the outcomes in 27 patients who had an ice-cream cone pelvic prosthesis inserted at two different specialist bone tumour centres in the United Kingdom over the past six years. The indications for treatment included primary bone tumours in 19 patients and metastatic disease in two, and six implants were inserted following failure of a previous pelvic reconstruction. Most of the patients had a P2+P3 resection as classified by Enneking, and most had resection of the ilium above the sciatic notch. The mean age of the patients at operation was 49 years (13 to 81). Complications occurred in ten patients (37.0%), of which dislocation was the most common, affecting four patients (14.8%). A total of three patients (11.1%) developed a deep infection around the prosthesis but all were successfully controlled by early intervention and two patients (7.4%) developed a local recurrence, at the same time as widespread metastases appeared. In one patient the prosthesis was removed for severe pain.

This method of treatment is still associated with high morbidity, but early results are promising. Complications are diminishing with increasing experience.

Objectives

Pseudotumours (abnormal peri-prosthetic soft-tissue reactions) following metal-on-metal hip resurfacing arthroplasty (MoMHRA) have been associated with elevated metal ion levels, suggesting that excessive wear may occur due to edge-loading of these MoM implants. This study aimed to quantify in vivo edge-loading in MoMHRA patients with and without pseudotumours during functional activities.

Recent events have highlighted the importance of implant design for survival and wear-related complications following metal-on-metal hip resurfacing arthroplasty. The mid-term survival of the most widely used implant, the Birmingham Hip Resurfacing (BHR), has been described by its designers. The aim of this study was to report the ten-year survival and patient-reported functional outcome of the BHR from an independent centre.

In this cohort of 554 patients (646 BHRs) with a mean age of 51.9 years (16.5 to 81.5) followed for a mean of eight years (1 to 12), the survival and patient-reported functional outcome depended on gender and the size of the implant. In female hips (n = 267) the ten-year survival was 74% (95% confidence interval (CI) 83 to 91), the ten-year revision rate for pseudotumour was 7%, the mean Oxford hip score (OHS) was 43 (sd 8) and the mean UCLA activity score was 6.4 (sd 2). In male hips (n = 379) the ten-year survival was 95% (95% CI 92.0 to 97.4), the ten-year revision rate for pseudotumour was 1.7%, the mean OHS was 45 (sd 6) and the mean UCLA score was 7.6 (sd 2). In the most demanding subgroup, comprising male patients aged < 50 years treated for primary osteoarthritis, the survival was 99% (95% CI 97 to 100).

This study supports the ongoing use of resurfacing in young active men, who are a subgroup of patients who tend to have problems with conventional THR. In contrast, the results in women have been poor and we do not recommend metal-on-metal resurfacing in women. Continuous follow-up is recommended because of the increasing incidence of pseudotumour with the passage of time.

There is widespread concern regarding the incidence of adverse soft-tissue reactions after metal-on-metal (MoM) hip replacement. Recent National Joint Registry data have shown clear differences in the rates of failure of different designs of hip resurfacing. Our aim was to update the failure rates related to metal debris for the Articular Surface Replacement (ASR). A total of 505 of these were implanted.

Kaplan-Meier analysis showed a failure rate of 25% at six years for the ASR resurfacing and of 48.8% for the ASR total hip replacement (THR). Of 257 patients with a minimum follow-up of two years, 67 (26.1%) had a serum cobalt concentration which was greater than 7 μg/l. Co-ordinate measuring machine analysis of revised components showed that all patients suffering adverse tissue reactions in the resurfacing group had abnormal wear of the bearing surfaces. Six THR patients had relatively low rates of articular wear, but were found to have considerable damage at the trunion-taper interface. Our results suggest that wear at the modular junction is an important factor in the development of adverse tissue reactions after implantation of a large-diameter MoM THR.

We report the findings of an independent review of 230 consecutive Birmingham hip resurfacings (BHRs) in 213 patients (230 hips) at a mean follow-up of 10.4 years (9.6 to 11.7). A total of 11 hips underwent revision; six patients (six hips) died from unrelated causes; and 13 patients (16 hips) were lost to follow-up. The survival rate for the whole cohort was 94.5% (95% confidence interval (CI) 90.1 to 96.9). The survival rate in women was 89.1% (95% CI 79.2 to 94.4) and in men was 97.5% (95% CI 92.4 to 99.2). Women were 1.4 times more likely to suffer failure than men. For each millimetre increase in component size there was a 19% lower chance of a failure. The mean Oxford hip score was 45.0 (median 47.0, 28 to 48); mean University of California, Los Angeles activity score was 7.4 (median 8.0, 3 to 9); mean patient satisfaction score was 1.4 (median 1.0, 0 to 9). A total of eight hips had lysis in the femoral neck and two hips had acetabular lysis. One hip had progressive radiological changes around the peg of the femoral component. There was no evidence of progressive neck narrowing between five and ten years.

Our results confirm that BHR provides good functional outcome and durability for men, at a mean follow-up of ten years. We are now reluctant to undertake hip resurfacing in women with this implant.

Resurfacing arthroplasties of the hip are being undertaken with increasing frequency and the complications associated with this procedure are well documented. We have encountered a further problem with a fracture of the centralising peg of the femoral component in a prosthesis which had been in situ for three years.

It is accepted that resurfacing hip replacement preserves the bone mineral density (BMD) of the femur better than total hip replacement (THR). However, no studies have investigated any possible difference on the acetabular side.

Between April 2007 and March 2009, 39 patients were randomised into two groups to receive either a resurfacing or a THR and were followed for two years. One patient’s resurfacing subsequently failed, leaving 19 patients in each group.

Resurfaced replacements maintained proximal femoral BMD and, compared with THR, had an increased bone mineral density in Gruen zones 2, 3, 6, and particularly zone 7, with a gain of 7.5% (95% confidence interval (CI) 2.6 to 12.5) compared with a loss of 14.6% (95% CI 7.6 to 21.6). Resurfacing replacements maintained the BMD of the medial femoral neck and increased that in the lateral zones between 12.8% (95% CI 4.3 to 21.4) and 25.9% (95% CI 7.1 to 44.6).

On the acetabular side, BMD was similar in every zone at each point in time. The mean BMD of all acetabular regions in the resurfaced group was reduced to 96.2% (95% CI 93.7 to 98.6) and for the total hip replacement group to 97.6% (95% CI 93.7 to 101.5) (p = 0.4863). A mean total loss of 3.7% (95% CI 1.0 to 6.5) and 4.9% (95% CI 0.8 to 9.0) of BMD was found above the acetabular component in W1 and 10.2% (95% CI 0.9 to 19.4) and 9.1% (95% CI 3.8 to 14.4) medial to the implant in W2 for resurfaced replacements and THRs respectively. Resurfacing resulted in a mean loss of BMD of 6.7% (95% CI 0.7 to 12.7) in W3 but the BMD inferior to the acetabular component was maintained in both groups.

These results suggest that the ability of a resurfacing hip replacement to preserve BMD only applies to the femoral side.

Objectives

An ongoing prospective study to investigate failing metal-on-metal hip prostheses was commenced at our centre in 2008. We report on the results of the analysis of the first consecutive 126 failed mated total hip prostheses from a single manufacturer.

We compared the medium-term clinical and radiological results of hybrid total hip replacement (THR) with metal-on-metal Birmingham hip resurfacing (BHR) in two groups of 54 young patients matched for age, gender, body mass index and pre-operative levels of activity.

The clinical outcome was assessed by the University of California, Los Angeles (UCLA) activity score, the Oxford Hip Score (OHS) and the EuroQol scores. Radiologically, all hips were assessed for migration and osteolysis, the hybrid THRs for polyethylene wear and the BHRs for a pedestal sign. The mean follow-up of the patients with a hybrid THR was ten years and for those with a BHR, nine years. Four patients with a hybrid THR and one with a BHR had died. In each group five were lost to follow-up. The revision rate of the hybrid THRs was 16.7% (9 of 54) and of the BHRs 9.3% (5 of 54) (p = 0.195). Radiographs of a further eight hybrid THRs demonstrated wear and osteolysis, and they await revision (p = 0.008). Of the unrevised BHRs 90% had radiological changes, of which approximately 50% had progressed over the previous four years. All hybrid THRs demonstrated linear polyethylene wear with a mean of 1.24 mm (0.06 to 3.03). The BHRs recorded superior OHS (p = 0.013), UCLA (p = 0.008), and EuroQol visual analogue scores (p = 0.009).

After nine years, patients with BHRs remained more active and had a lower rate of revision than those with hybrid THRs. Both groups demonstrated progressive radiological changes at medium-term follow-up.

Endoprosthetic replacement of the proximal femur may be required to treat primary bone tumours or destructive metastases either with impending or established pathological fracture. Modular prostheses are available off the shelf and can be adapted to most reconstructive situations for this purpose. We have assessed the clinical and functional outcome of using the METS (Stanmore Implants Worldwide) modular tumour prosthesis to reconstruct the proximal femur in 100 consecutive patients between 2001 and 2006. We compared the results with the published series for patients managed with modular and custom-made endoprosthetic replacements for the same conditions.

There were 52 males and 48 females with a mean age of 56.3 years (16 to 84) and a mean follow-up of 24.6 months (0 to 60). In 65 patients the procedure was undertaken for metastases, in 25 for a primary bone tumour, and in ten for other malignant conditions. A total of 46 patients presented with a pathological fracture, and 19 presented with failed fixation of a previous pathological fracture. The overall patient survival was 63.6% at one year and 23.1% at five years, and was significantly better for patients with a primary bone tumour than for those with metastatic tumour (82.3% vs 53.3%, respectively at one year (p = 0.003)). There were six early dislocations of which five could be treated by closed reduction. No patient needed revision surgery for dislocation. Revision surgery was required by six (6%) patients, five for pain caused by acetabular wear and one for tumour progression. Amputation was needed in four patients for local recurrence or infection.

The estimated five-year implant survival with revision as the endpoint was 90.7%. The mean Toronto Extremity Salvage score was 61% (51% to 95%). The implant survival and complications resulting from the use of the modular system were comparable to the published series of both custom-made and other modular proximal femoral implants.

We conclude that at intermediate follow-up the modular tumour prosthesis for proximal femur replacement provides versatility, a low incidence of implant-related complications and acceptable function for patients with metastatic tumours, pathological fractures and failed fixation of the proximal femur. It also functions as well as a custom-made endoprosthetic replacement.

Objectives

The aims of this piece of work were to: 1) record the background concentrations of blood chromium (Cr) and cobalt (Co) concentrations in a large group of subjects; 2) to compare blood/serum Cr and Co concentrations with retrieved metal-on-metal (MoM) hip resurfacings; 3) to examine the distribution of Co and Cr in the serum and whole blood of patients with MoM hip arthroplasties; and 4) to further understand the partitioning of metal ions between the serum and whole blood fractions.

The cause of fracture of the femoral neck after hip resurfacing is poorly understood. In order to evaluate the role of avascular necrosis we compared 19 femoral heads retrieved at revision for fracture of the femoral neck and 13 retrieved for other reasons.

We developed a new technique of assessing avascular necrosis in the femoral head by determining the percentage of empty osteocyte lacunae present. Femoral heads retrieved as controls at total hip replacement for osteoarthritis and avascular necrosis had 9% (sd 4; n = 13) and 85% (sd 5; n = 10, p < 0.001) empty lacunae, respectively.

In the fracture group the percentage of empty lacunae was 71% (sd 22); in the other group it was 21% (sd 13). The differences between the groups were highly significant (p < 0.001).

We conclude that fracture after resurfacing of the hip is associated with a significantly greater percentage of empty osteocyte lacunae within the trabecular bone. This indicates established avascular necrosis and suggests that damage to the blood supply at the time of surgery is a potent risk factor for fracture of the femoral neck after hip resurfacing.

We have investigated the accuracy of placement of the femoral component using imageless navigation in 100 consecutive Birmingham Hip Resurfacings. Pre-operative templating determined the native neck-shaft angle and planned stem-shaft angle of the implant. The latter were verified post-operatively using digital anteroposterior unilateral radiographs of the hip.

The mean neck-shaft angle determined before operation was 132.7° (118° to 160°). The mean planned stem-shaft angle was a relative valgus alignment of 9.7° (sd 2.6). The stem-shaft angle after operation differed from that planned by a mean of 2.8° (sd 2.0) and in 86% of cases the final angle measured within ± 5° of that planned. We had no instances of notching of the neck or varus alignment of the implant in our series. A learning curve was observed in the time taken for navigation, but not for accurate placement of the implant.

Navigation in hip resurfacing may afford the surgeon a reliable and accurate method of placement of the femoral component.

This study reports the mid-term results of a large-bearing hybrid metal-on-metal total hip replacement in 199 hips (185 patients) with a mean follow-up of 62 months (32 to 83).

Two patients died of unrelated causes and 13 were lost to follow-up. In all, 17 hips (8.5%) have undergone revision, and a further 14 are awaiting surgery. All revisions were symptomatic. Of the revision cases, 14 hips showed evidence of adverse reactions to metal debris. The patients revised or awaiting revision had significantly higher whole blood cobalt ion levels (p = 0.001), but no significant difference in acetabular component size or position compared with the unrevised patients. Wear analysis (n = 5) showed increased wear at the trunnion-head interface, normal levels of wear at the articulating surfaces and evidence of corrosion on the surface of the stem.

The cumulative survival rate, with revision for any reason, was 92.4% (95% confidence interval 87.4 to 95.4) at five years. Including those awaiting surgery, the revision rate would be 15.1% with a cumulative survival at five years of 89.6% (95% confidence interval 83.9 to 93.4).

This hybrid metal-on-metal total hip replacement series has shown an unacceptably high rate of failure, with evidence of high wear at the trunnion-head interface and passive corrosion of the stem surface. This raises concerns about the use of large heads on conventional 12/14 tapers.

Patients considered suitable for total hip resurfacing arthroplasty often have bilateral disease. The peri-operative complications, transfusion requirements, hospital stay, outcome and costs in patients undergoing one-stage bilateral total hip resurfacing were compared with a group of patients undergoing a two-stage procedure. A total of 92 patients were included in the study, of which 37 (40%) had a one-stage and 55 (60%) had a two-stage resurfacing. There were no significant differences in age, gender, or American Society of Anaesthesiologists grade between the groups (p = 0.31, p = 0.23, p = 0.13, respectively). There were three systemic complications in the one-stage group (8.1%) and one in the two-stage group (1.8% of patients; 0.9% of procedures). There was no significant difference in the complication rate (p = 0.72) or the transfusion requirements (p = 0.32) between the two groups. The one-stage group had a reduced total hospital stay of five days (95% confidence interval 4.0 to 6.9; p < 0.001), reduced length of time to completion of all surgery of five months (95% confidence interval 2.6 to 8.3; p < 0.001), and the reduced cost was 35% less than that of a two-stage procedure. However, the total anaesthetic time was significantly longer for the one-stage group (p < 0.001; 95% confidence interval 31 to 52).

This study demonstrates that consideration should be given to one-stage surgery for patients with bilateral symptomatic disease suitable for metal-on-metal hip resurfacing. A one-stage procedure appears to have benefits for both the patient and the hospital without additional complications.

This is a longitudinal study of the daily urinary output and the concentrations in whole blood of cobalt and chromium in patients with metal-on-metal resurfacings over a period of four years.

Twelve-hour urine collections and whole blood specimens were collected before and periodically after a Birmingham hip resurfacing in 26 patients. All ion analyses were carried out using a high-resolution inductively-coupled plasma mass spectrometer. Clinical and radiological assessment, hip function scoring and activity level assessment revealed excellent hip function.

There was a significant early increase in urinary metal output, reaching a peak at six months for cobalt and one year for chromium post-operatively. There was thereafter a steady decrease in the median urinary output of cobalt over the following three years, although the differences are not statistically significant. The mean whole blood levels of cobalt and chromium also showed a significant increase between the pre-operative and one-year post-operative periods. The blood levels then decreased to a lower level at four years, compared with the one-year levels. This late reduction was statistically significant for chromium but not for cobalt.

The effects of systemic metal ion exposure in patients with metal-on-metal resurfacing arthroplasties continue to be a matter of concern. The levels in this study provide a baseline against which the in vivo wear performance of newer bearings can be compared.

A total of 20 pairs of fresh-frozen cadaver femurs were assigned to four alignment groups consisting of relative varus (10° and 20°) and relative valgus (10° and 20°), 75 composite femurs of two neck geometries were also used. In both the cadaver and the composite femurs, placing the component in 20° of valgus resulted in a significant increase in load to failure. Placing the component in 10° of valgus had no appreciable effect on increasing the load to failure except in the composite femurs with varus native femoral necks. Specimens in 10° of varus were significantly weaker than the neutrally-aligned specimens.

The results suggest that retention of the intact proximal femoral strength occurs at an implant angulation of ≥ 142°. However, the benefit of extreme valgus alignment may be outweighed in clinical practice by the risk of superior femoral neck notching, which was avoided in this study.

Pseudotumour is a rare but important complication of metal-on-metal hip resurfacing that occurs much more commonly in women than in men. We examined the relationship between head-neck ratio (HNR) and pseudotumour formation in 18 resurfaced hips (18 patients) revised for pseudotumour and 42 asymptomatic control resurfaced hips (42 patients).

Patients in whom pseudotumour formation had occurred had higher pre-operative HNR than the control patients (mean 1.37 (sd 0.10) vs mean 1.30 (sd 0.08) p = 0.001). At operation the patients with pseudotumours had a greater reduction in the size of their femoral heads (p = 0.035) and subsequently had greater neck narrowing (mean 10.1% (sd 7.2) vs mean 3.8% (sd 3.2) p < 0.001). No female patient with a pre-operative HNR ≤ 1.3 developed a pseudotumour.

We suggest that reducing the size of the femoral head, made possible by a high pre-operative HNR, increases the risk of impingement and edge loading, and may contribute to high wear and pseudotumour formation. As the incidence of pseudotumour is low in men, it appears safe to perform resurfacing in men. However, this study suggests that it is also reasonable to resurface in women with a pre-operative HNR ≤ 1.3.

We present the early clinical and radiological results of Articular Surface Replacement (ASR) resurfacings in 214 hips (192 patients) with a mean follow-up of 43 months (30 to 57). The mean age of the patients was 56 years (28 to 74) and 85 hips (40%) were in 78 women.

The mean Harris hip score improved from 52 (11 to 81) to 95 (27 to 100) at two years and the mean University of California, Los Angeles activity score from 3.9 (1 to 10) to 7.4 (2 to 10) in the same period. Narrowing of the neck (to a maximum of 9%) was noted in 124 of 209 hips (60%). There were 12 revisions (5.6%) involving four (1.9%) early fractures of the femoral neck and two (0.9%) episodes of collapse of the femoral head secondary to avascular necrosis. Six patients (2.8%) had failure related to metal wear debris. The overall survival for our series was 93% (95% confidence interval 80 to 98) and 89% (95% confidence interval 82 to 96) for hips with acetabular components smaller than 56 mm in diameter.

The ASR implant has a lower diametrical clearance and a subhemispherical acetabular component when compared with other more frequently implanted metal-on-metal hip resurfacings. These changes may contribute to the higher failure rate than in other series, compared with other designs. Given our poor results with the small components we are no longer implanting the smaller size.

Previous research has shown an increase in chromosomal aberrations in patients with worn implants. The type of aberration depended on the type of metal alloy in the prosthesis. We have investigated the metal-specific difference in the level of DNA damage (DNA stand breaks and alkali labile sites) induced by culturing human fibroblasts in synovial fluid retrieved at revision arthroplasty.

All six samples from revision cobalt-chromium metal-on-metal and four of six samples from cobalt-chromium metal-on-polyethylene prostheses caused DNA damage. By contrast, none of six samples from revision stainless-steel metal-on-polyethylene prostheses caused significant damage. Samples of cobalt-chromium alloy left to corrode in phosphate-buffered saline also caused DNA damage and this depended on a synergistic effect between the cobalt and chromium ions.

Our results further emphasise that epidemiological studies of orthopaedic implants should take account of the type of metal alloy used.

We report a retrospective review of the incidence of venous thromboembolism in 463 consecutive patients who underwent primary total hip arthroplasty (487 procedures). Treatment included both total hip replacement and hip resurfacing, and the patients were managed without anticoagulants. The thromboprophylaxis regimen included an antiplatelet agent, generally aspirin, hypotensive epidural anaesthesia, elastic compression stockings and early mobilisation. In 258 of these procedures (244 patients) performed in 2005 (cohort A) mechanical compression devices were not used, whereas in 229 (219 patients) performed during 2006 (cohort B) bilateral intermittent pneumatic calf compression was used.

All operations were performed through a posterior mini-incision approach. Patients who required anticoagulation for pre-existing medical problems and those undergoing revision arthroplasty were excluded. Doppler ultrasonographic screening for deep-vein thrombosis was performed in all patients between the fourth and sixth post-operative days. All patients were reviewed at a follow-up clinic six to ten weeks after the operation. In addition, reponse to a questionnaire was obtained at the end of 12 weeks post-operatively.

No symptomatic calf or above-knee deep-vein thrombosis or pulmonary embolism occurred. In 25 patients in cohort A (10.2%) and in ten patients in cohort B (4.6%) asymptomatic calf deep-vein thromboses were detected ultrasonographically. This difference was statistically significant (p = 0.03). The regimen followed by cohort B offers the prospect of a low incidence of venous thromboembolism without subjecting patients to the higher risk of bleeding associated with anticoagulant use.

We carried out a cross-sectional study with analysis of the demographic, clinical and laboratory characteristics of patients with metal-on-metal hip resurfacing, ceramic-on-ceramic and metal-on-polyethylene hip replacements. Our aim was to evaluate the relationship between metal-on-metal replacements, the levels of cobalt and chromium ions in whole blood and the absolute numbers of circulating lymphocytes. We recruited 164 patients (101 men and 63 women) with hip replacements, 106 with metal-on-metal hips and 58 with non-metal-on-metal hips, aged < 65 years, with a pre-operative diagnosis of osteoarthritis and no pre-existing immunological disorders.

Laboratory-defined T-cell lymphopenia was present in13 patients (15%) (CD8⁺ lymphopenia) and 11 patients (13%) (CD3⁺ lymphopenia) with unilateral metal-on-metal hips. There were significant differences in the absolute CD8⁺ lymphocyte subset counts for the metal-on-metal groups compared with each control group (p-values ranging between 0.024 and 0.046). Statistical modelling with analysis of covariance using age, gender, type of hip replacement, smoking and circulating metal ion levels, showed that circulating levels of metal ions, especially cobalt, explained the variation in absolute lymphocyte counts for almost all lymphocyte subsets.

Increased concentrations of metal ions after metal-on-metal resurfacing arthroplasty of the hip remain a concern. Although there has been no proven link to long-term health problems or early prosthetic failure, variables associated with high metal ion concentrations should be identified and, if possible, corrected. Our study provides data on metal ion levels from a series of 76 consecutive patients (76 hips) after resurfacing arthroplasty with the Articular Surface Replacement. Chromium and cobalt ion concentrations in the whole blood of patients with smaller (≤ 51 mm) femoral components were significantly higher than in those with the larger (≥ 53 mm) components (p < 0.01). Ion concentrations in the former group were significantly related to the inclination (p = 0.01) and anteversion (p = 0.01) of the acetabular component. The same relationships were not significant in the patients with larger femoral components (p = 0.61 and p = 0.49, respectively). Accurate positioning of the acetabular component intra-operatively is essential in order to reduce the concentration of metal ions in the blood after hip resurfacing arthroplasty with the Articular Surface Replacement implant.