The use of Birmingham hip resurfacing (BHR) remains controversial due to the increased revision rate in female patients. We compared the outcomes of
Background. Hip resurfacing arthroplasty (HRA) has seen a recent revival with third generation Metal-on-Metal prostheses and is now widely in use. However, safety and effectiveness of hip resurfacing are still questioned. We systematically reviewed peer-reviewed literature on hip resurfacing arthroplasty to address these issues. Objective. To evaluate implant survival and functional outcomes of hybrid Metal-on-Metal hip resurfacing arthroplasty (HRA). Method. Electronic databases and reference lists were searched from 1988 to May 2010. Identified abstracts were checked for inclusion or exclusion by two independent reviewers. Data were extracted and summarized by one reviewer and verified by a second reviewer. Main study endpoint was implant survival, which we compared with the National Institute of Clinical Excellence (NICE) benchmark. We also evaluated radiological and functional outcomes, failure modes and other adverse events. The quality of evidence was judged using the Grading of Recommendations Assessment, Development and Evaluation system (GRADE). Results. We identified 539 articles, of which 29 met the inclusion criteria. The studies included one randomised clinical trial, 27 prospective case series and one retrospective case series. Data were extracted from these 29 articles, totalling 10621 resurfaced hips, providing details on five out of 11 resurfacing devices on the market. Mean follow up ranged from 0.6 to 10.5 years and implant survival ranged from 84% to 100%. Of the 10621 hips, 370 were revised (3.5%), with aseptic loosening as most frequent failure mode. None of the HRA implants used to date met the full 10 year NICE benchmark. Thirteen studies showed satisfactory implant survival percentages compared to the three year NICE entry-benchmark. These 13 studies used the
INTRODUCTION. Whilst there is a great deal of research on hip implants, few studies have looked at implant orientation and the subsequent effect upon the wear performance of a hip resurfacing. This study aimed to measure implantation angles through radiographic analysis and linear wear for retrieved acetabular cups in order to investigate possible causal links between wear and implant orientation. MATERIALS & METHODS. Seventy Birmingham Hip Resurfacing (Smith & Nephew, UK) cups with known time in vivo were analysed. Linear wear of retrieved cups were assessed using a Talyrond 290 roundness machine. Deviations from the characteristic manufactured profile, was identified as a region of wear. Polar measurements across the wear region were taken to determine wear. The linear wear rate (LWR) of a component was defined as the linear wear (μm) divided by the duration of the implant life in vivo (years). Cups which showed the wear crossing over the edge of the cup were classified as edge loaded (EL). For all non-edge loaded (NEL) cups, the wear area was within the bearing surface. Cup orientation angles were conducted for 31 cups. This was determined by superimposing
Introduction. It was the purpose to evaluate the biomechanical changes that occur after optimal and non-optimal component placement of a hip resurfacing (SRA) by using a subject specific musculoskeletal model based on CT-scan data. Materials and Methods. Nineteen hips from 11 cadavers were resurfaced with a
INTRODUCTION. Studies have suggested that there is a reduction in head-neck-ratio (HNR) associated with MoMHRA. A reduction in HNR at operation would decrease range of movement and increase impingement risk. Impingement could lead to 20 edge loading, increasing wear. Serum ion levels of Chromium (Cr) and Cobalt (Co) are surrogate markers of wear. Although acetabular component orientation has been shown to contribute to wear and PT development, the role of a decrease in HNR has only been highlighted in PT development. This study aimed to measure changes in HNR that occur at resurfacing and determine any gender- and component size-specific differences. In addition it aimed to determine whether changes in HNR could be associated with increased wear. METHODS. 84 patients (56M: 28F) with unilateral MoMHRA were included. The mean age at surgery was 57 years. The mean femoral component was 49mm. Components were considered small if <45mm, average if between 45–50mm and large if >50mm. Three designs were implanted;
INTRODUCTION. Hip wear simulator test results could be affected by many non-bearing related factors such as fixation surface conditions, equipment calibration and component set-up. In an effort to improve the accuracy, reliability and repeatability of hip simulator test, a quality management system has been established at the IDC hip tribology laboratory, which has been accredited by UKAS (United Kingdom Accreditation Service) in accordance with the recognised international standard ISO17025. This study demonstrates that under well-controlled laboratory and testing conditions, satisfactory repeatability can be achieved during hip simulator studies. METHODS. Between 2008 to 2010, ten 50 mm Birmingham Hip Resurfacing (BHR) devices were tested by the IDC tribology laboratory using two ProSim hip wear simulators in three different tests (T1, T2 and T3). All tests were performed following the same IDC testing protocols at 1 Hz frequency for 5 million cycles (Mc) or until after a steady state was reached. Paul type stance phase loadings with a maximum load of 3 kN and a swing phase load of 0.3 kN was used. The flexion and extension angles were 30 and 15 degree. The internal/external rotation angel was ±10 degree. Wear was measured gravimetrically using an analytical balance (Mettler, Toledo xp504) with an accuracy of 0.1 mg. RESULTS. Results showed that wear of all the components tested followed the typical biphasic trend of wear for MoM hip joint device with a high “running-in” wear during the initial stage followed by a low “steady state” wear in the later stage. The data points scattered in a narrow range following the same trend line throughout the tests. The maximum difference in accumulated volume loss between any two tests at any given cycle was less in 0.2 mm3. The average running-in wear rates (±SD) were 0.72 ±0.17, 0.86 ±0.01 and 0.71 ±0.19 mm3/Mc respectively for test T1, T2 and T3. The running-in wear rates for test T1 and T3 were identical, whilst that for T2 was slightly higher. In spite of this, the wear rates for the bearings tested in T2 were still in the same range as those tested in T1 and T3 during the running-in stage. The steady state (>1.0Mc) wear rate of three different tests was practically the same, being 0.18 ±0.02, 0.18 ±0.06 and 0.16 ±0.04 mm3/Mc respectively for test T1, T2 and T3. Overall, the mean running-in wear rate was 0.74 ±0.16 mm3/Mc, and the steady state wear rate was 0.17 ±0.04 mm3/Mc for the 10
INTRODUCTION. Femoral neck narrowing (NN) following Metal-on-Metal Hip Resurfacing Arthroplasty (MoMHRA) is a well-recognised clinical phenomenon. The incidence of resurfaced hips with NN > 10% is reported to be up to 27%. Its pathogenesis is thought to be multi-factorial secondary to stress shielding, impingement, osteolysis secondary to wear/ion particles and as a result of reduced vascularity and pressure effect on cancellous bone secondary to the presence of a soft-tissue mass around the resurfaced hip. Recognised risk factors for its development include: female gender and the presence of a pseudotumour. Serum Chromium (Cr) and Cobalt (Co) are recognised surrogate markers of in-vivo wear of MoMHRA. The aims of this study were to establish whether NN is associated with increased wear. METHODS. A cohort of 214 patients with unilateral MoMHRA (139M: 75F) was included in this study. Primary osteoarthritis was the diagnosis leading to surgery for the majority of patients (208). The average age at surgery was 54.1 years old (13–73). Six different implants were used;
