The following are some relevant selected scientific references:
1. Risk factors for inflammatory pseudotumour formation following hip resurfacing.
J Bone Joint Surg Br. 2009 Dec;91(12):1566-74.
Glyn-Jones S, Pandit H, Kwon YM, Doll H, Gill HS, Murray DW.
Department of Orthopaedics, Nuffield Orthopaedic Centre, University of Oxford, Oxford, England.
Abstract: 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 whereas 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.
2. Canadian academic experience with metal-on-metal hip resurfacing.
Bull NYU Hosp Jt Dis. 2009;67(2):128-31.
O’Neill M, Beaule PE, Bin Nasser A, Garbuz D, Lavigne M, Duncan C, Kim PR, Schemitsch E.
Abstract: The current depth and breadth of experience in hip resurfacing in Canadian academic centers is not well known. This study endeavors to increase awareness of the prevalence of programs and current experience in a select number of representative teaching centers by examining the learning curve of high-volume surgeons. A questionnaire was sent to all academic centers in Canada to identify the volume of hip resurfacing, surgical approach, and type of prosthesis. In addition, five surgeons, not fellowship-trained in hip resurfacing, were selected for a detailed review of their first 50 cases, including survey of patient demographics, surgical approach, radiographic evaluation, complications, and revision. Eleven of 14 academic centers are currently performing hip resurfacing. All of these centers had performed more than 50 cases, with 10 of 11 of them having more than one surgeon performing the procedure. The posterior approach was found to be the most commonly utilized in surgeries. The overall revision rate was 3.2% at a mean time of 2 years, with femoral neck fracture (1.6%) being the most common cause for failure. The failure rate was comparable to other centers of expertise and lower than previously published multicenter trials. All surgeons reviewed were in specialized arthroplasty practices, which may contribute to the relatively low complication rates reported.
3. Sex as a Patient Selection Criterion for Metal-on-Metal Hip Resurfacing Arthroplasty.
J Arthroplasty. 2010 May 7. [Epub ahead of print]
Amstutz HC, Wisk LE, Le Duff MJ.
Joint Replacement Institute at St. Vincent Medical Center, Los Angeles, California.
Abstract: Short-term to midterm results of hip resurfacing arthroplasty suggest various contraindications, in particular the female sex. This study evaluates survivorship and clinical outcomes of a large patient cohort to determine whether sex itself has a detrimental effect on the results of hip resurfacing. We compared the clinical and survivorship results of men and women from a series of 1107 resurfaced hips in 923 patients (681 males and 242 females). Women saw greater positive changes in walking, function, and the mental component of the Short Form-12. There was no difference in complication rates between men and women. Although the revision rate was higher in the women’s group, the effect of sex disappeared when adjusted for component size and surgical technique. These data suggest that there is no appreciable effect of sex on implant survivorship and that women may be excellent candidates for resurfacing with proper surgical technique. This is a level III, retrospective comparative study.
4. Eleven years of experience with metal-on-metal hybrid hip resurfacing: a review of 1000 conserve plus.
J Arthroplasty. 2008 Sep;23(6 Suppl 1):36-43.
Amstutz HC, Le Duff MJ.
Joint Replacement Institute at St Vincent Medical Center, Los Angeles, California 90057, USA.
Abstract: Hip resurfacing is currently the fastest growing hip procedure worldwide. We reviewed 1000 hips in 838 patients who received a Conserve Plus (Wright Medical Technology, Inc., Arlington, Tenn) resurfacing at a single institution. The mean age of the patients was 50.0 years with 74.7% male. The hips were resurfaced irrespective of femoral defect size or etiology. The mean follow-up was 5.6 years (range, 1.1-11.0 years). All clinical scores improved significantly (P < .05). There was no acetabular component loosening. Ten were converted to total hip arthroplasty for femoral neck fracture, 20 for femoral loosening, 2 for sepsis, and 1 for recurrent subluxations. The 5-year survivorship was 95.2% with no failures in hips implanted since 2002. Short-term failures can be prevented. First-generation surgical technique and a low body mass index were the most important risk factors for the procedure. Improvements in bone preparation significantly increased prosthetic survival in hips with risk factors for failure.
5. Birmingham hip resurfacing: Five to eight year results.
Int Orthop. 2010 Jun 19. [Epub ahead of print]
Reito A, Puolakka T, Pajamäki J.
Abstract: Hip resurfacings have been performed in our hospital since May 2001, and in this retrospective study, we analysed the clinical and radiological outcome of the first 144 prostheses (126 patients). One hundred and seven patients have visited our hospital for regular follow-up examination; 16 are not in regular follow-up and were sent a Harris Hip Score (HHS) questionnaire. Three patients live abroad. Mean follow-up was six years. One patient was lost during follow-up. Four prostheses have been revised. The six year cumulative survival rate was 96.7%. Two female patients required revision for aseptic lymphocyte-dominated vascular associated lesions (ALVAL) and two male patients due for femoral head necrosis. Both reoperated female patients had cup inclination >60 degrees . Mean HHS in the follow-up was 95.3, and mean patient satisfaction 2.53 on a scale 0-3. Neck thinning >10% was seen in seven hips and impingement in 12 hips.
6. The influence of head size and sex on the outcome of Birmingham hip resurfacing.
J Bone Joint Surg Am. 2010 Jan;92(1):105-12.
McBryde CW, Theivendran K, Thomas AM, Treacy RB, Pynsent PB.
Abstract: BACKGROUND: Hip resurfacing has gained popularity for the treatment of young and active patients who have arthritis. Recent literature has demonstrated an increased rate of revision among female patients as compared with male patients who have undergone hip resurfacing. The aim of the present study was to identify any differences in survival or functional outcome between male and female patients with osteoarthritis who were managed with metal-on-metal hip resurfacing. METHODS: A prospective collection of data on all patients undergoing Birmingham Hip Resurfacing at a single institution was commenced in July 1997. On the basis of the inclusion and exclusion criteria, 1826 patients (2123 hips, including 799 hips in female patients and 1324 hips in male patients) with a diagnosis of osteoarthritis who had undergone the procedure between July 1997 and December 2008 were identified. The variables of age, sex, preoperative Oxford Hip Score, component size used, surgical approach, lead surgeon, and surgeon experience were analyzed. A multivariate Cox proportional hazard survival model was used to identify which variables were most influential for determining revision. RESULTS: The mean duration of follow-up was 3.46 years (range, 0.03 to 10.9 years). The five-year cumulative survival rate for the 655 hips that were followed for a minimum of five years was 97.5% (95% confidence interval, 96.3% to 98.3%). There were forty-eight revisions. Revision was significantly associated with female sex (hazard rate, 2.03 [95% confidence interval, 1.15 to 3.58]; p = 0.014) and decreasing femoral component size (hazard rate per 4-mm decrease in size, 4.68 [95% confidence interval, 4.36 to 5.05]; p < 0.001). Revision was not associated with age (p = 0.88), surgeon (p = 0.41), surgeon experience (p = 0.30), or surgical approach (p = 0.21). A multivariate analysis including the covariates of sex, age, surgeon, surgeon experience, surgical approach, and femoral component size demonstrated that sex was no longer significantly associated with revision when femoral component size was included in the model (p = 0.37). Femoral component size alone was the best predictor of revision when all covariates were analyzed (hazard rate per 4-mm decrease in size, 4.87 [95% confidence interval, 4.37 to 5.42]; p < 0.001). CONCLUSIONS: The present study demonstrates that although female patients initially may appear to have a greater risk of revision, this increased risk is related to differences in the femoral component size and thus is only indirectly related to sex. Patient selection for hip resurfacing is best made on the basis of femoral head size rather than sex.
7. Birmingham hip arthroplasty: five to eight years of prospective multicenter results.
J Arthroplasty. 2009 Oct;24(7):1044-50.
Khan M, Kuiper JH, Edwards D, Robinson E, Richardson JB.
Abstract: Pioneering centers report excellent results of Birmingham resurfacing arthroplasty. Results from pioneering surgeons are not usually reproduced when implants are used at other centers. We therefore studied patients’ satisfaction, postoperative hip function, and survival of Birmingham hip resurfacing in a group, operated by nonpioneering surgeons. The median first year postoperative Harris hip score was 95, and this score was sustained for a period of 8 years. The cumulative survival at 8 years was 95.7%. Most of the failures were in the first year; commonest cause of the first year failures was fracture of femoral neck. This complication is not seen as a substantial problem in the pioneering surgeons’ studies. We therefore conclude that this complication is not related to the prosthesis and that its occurrence can be reduced.
8. Birmingham hip resurfacing arthroplasty. A minimum follow-up of five years.
J Bone Joint Surg Br. 2005 Feb;87(2):167-70.
Treacy RB, McBryde CW, Pynsent PB.
Royal Orthopaedic Hospital, Birmingham, England.
Abstract: We report the survival at five years of 144 consecutive metal-on-metal resurfacings of the hip implanted between August 1997 and May 1998. Failure was defined as revision of either the acetabular or femoral component for any reason during the study period. The survival at the end of five years was 98% overall and 99% for aseptic revisions only. The mean age of the patients at implantation was 52.1 years. Three femoral components failed during the first two years, two were infected and one fractured. A single stage revision was carried out in each case. No other revisions were performed or are impending. No patients were lost to follow-up. Four died from unrelated causes during the study period. This study confirms that hip resurfacing using a metal-on-metal bearing of known provenance can provide a solution in the medium term for the younger more active adult who requires surgical intervention for hip disease.
9. What is the Midterm Survivorship and Function After Hip Resurfacing?
Clin Orthop Relat Res. 2010 Jun 24. [Epub ahead of print]
Rahman L, Muirhead-Allwood SK, Alkinj M.
The London Hip Unit, 30 Devonshire Street, London, W1G 6PU, UK
Abstract: BACKGROUND: Hip resurfacing arthroplasty is a common procedure that improves functional scores and has a reported survivorship between 95% and 98% at 5 years. However, most studies are reported from the pioneering rather than independent centers or have relatively small patient numbers or less than five years followup. Various factors have been implicated in early failure. QUESTIONS/PURPOSES: Our purposes were to determine: (1) the midterm survival of the BHR; (2) the function in patients treated with hip resurfacing; and (3) whether age, gender, BMI, or size of components related to failure. METHODS: We reviewed the first 302 patients (329 hips) on whom we performed resurfacing arthroplasty. We assessed the survivorship, change in functional hip scores (HHS, OHS, WOMAC, UCLA), and analyzed potential risk factors (age, gender, BMI, component size) for failure. The mean age at the time of surgery was 56.0 years (range, 28.2-75.5 years). The minimum followup was 5 years (mean, 6.6 years; range, 5-9.2 years). RESULTS: Kaplan-Meier analysis showed survival of 96.5% (95% CI, 94.7-98.4) at 9 years taking revision for any cause as the endpoint. All functional hip scores (HHS, OHS, WOMAC, UCLA) improved. Survivorship was higher in men compared with women. The component sizes and body mass index were smaller in the revised group compared with the nonrevised group. CONCLUSIONS: Medium-term survivorship and functional scores of hip resurfacing are comparable to those from the pioneering center. Hip resurfacing remains a good alternative to THA, particularly in the younger male population with relatively large femoral head sizes