Hip resurfacing has grown rapidly since its introduction in the United States, as an alternative to total hip replacement in the younger, active patient. Some studies have suggested a steep learning curve and a higher complication rate when compared to THR. Existing studies have originated from the pioneering surgeons, using a specific type of resurfacing implant. The purpose of this study was to look at the experience of a single, non-inventor surgeon with the adoption of hip resurfacing, using 3 different implants. M&M. All consecutive hip resurfacings performed by the senior surgeon between 2004 and 2008 were included, providing a minimum 2 year followup period. 3 different implant types were used; 2 of these were used as part of the clinical trials, and 1 was used after US FDA approval. A total of 560 hip resurfacings were eligible for the study based upon a minimum of 2 year followup. Results. Nine revisions were performed in this cohort (1.6%). 2 were femoral conversions to endoprostheses for femoral neck fracture; 3 additional femoral conversions were done for osteonecrosis of the femoral head. 1 acetabular revision only was performed for malposition. 2 revisions to THR of both the acetabular and femoral components were done for acetabular loosening and excessive metal production (edge loading). There was 1 revision for metal hypersensitivity. Overall, the K-M survival curve is 98.1% at 4 years. There was no difference with regard to survival from additional surgery with regard to the different implant types. Radiographic signs of failure were also documented. In this cohort, 3 femoral and 1 acetabular components were identified to be radiographically loose, giving a K-M survival from clinical and radiographic failure to be 96.8% at 4 years. Discussion. Hip resurfacing can be adopted successfully with a low rate of reoperation, by the use of careful patient selection. A single surgeon's experience with 3 different types of implants demonstrated no difference in clinical results between the devices

Background. Pseudotumours have been associated with metal-on-metal (MoM) hip replacements. We define it as a solid mass which may have cystic components that is neither neoplastic nor infectious in aetiology. The cause of a pseudotumour is not fully understood but could be due to excessive wear, metal hypersensitivity or due to an as-yet unknown cause. Aim. We present the retrieval analysis of early failure MoM hips revised for pain, loosening or a symptomatic mass. Tissues and implants were examined for the possible causes of failure and pseudotumour formation. Corrosion as a potential new cause for pseudotumour formation will be presented. Methods. A group of 16 MoM hip replacements were collected for retrieval analysis. Six of which had a pseudotumour. An Artificial Hip Profiler (Redlux Ltd) was used to measure wear. Edge loading was determined using the 3D wear data. Tissues were histologically evaluated using a 10-point ALVAL scoring system, which strongly suggests hypersensitivity (1). Cases were assigned to one of three categories: high wear (rates >5m/yr), hypersensitivity or corrosion. Results. Of the 6 pseudotumours, 3 had edge loading, 2 had high ALVAL scores and one had corrosion at the head taper junction. The high wear group, (3 cases) all demonstrated edge loading. Histology revealed more metal wear particles and macrophages, with a low ALVAL score in these cases. Two cases were found to have hypersensitivity with a high ALVAL score, more lymphocytes with less visible wear debris and macrophages. The wear rates were also lower, <4m/yr. One total hip replacement had corrosion at the junction between the head and adaptor taper for the stem. The bearings had low wear and the tissue had extensive necrosis as well as products of corrosion enclosed in fibrin (2). There was no suggestion of hypersensitivity (low ALVAL score). Conclusion. Pseudotumours can be caused by high wear, but if this is ruled out, a hypersensitivity or corrosion product reaction should be considered

In a randomized study of 60 patients allergic reactions are evaluated in three joint prosthesis groups, a resurfacing arthroplasty (ReCap), a non-cemented, large metal-on-metal head (Bimetric Magnum) and a non-cemented, alumina ceramic-on-ceramic bearing in a titanium shell (Bimetric C2a). The inclusion criteria were osteoarthritis, ASA I–II, MRI-scan without caput necrosis, DXA-scan without osteoporosis. The exclusion criteria were short neck (<2cm.), large cysts (>1cm.), medical treatment affecting the bone metabolism, severe deformity of the femoral head, impaired kidney function and inability to co-operate. Blood samples were drawn prior to and 6 weeks, 6 months, 1 year, and 3 years after surgery; two tubes from which plasma was prepared, and two tubes for serum. From the last included 20 patients in each group was also taken blood one and three years after surgery for an in vitro lymphocyte assay for scoring of possible hypersensitivity to prosthesis metals. The isolated lymphocytes were subjected to measurement of proliferation and expression of CD69 by flow cytometry and measurement of the Migration Inhibitory Factor (MIF) by ELISA. Plasma concentrations of the cytokines IL-1, IL-4, IL-6, IL-8, IL-12p70, IL-15, interferon-and osteoprotegerin were determined by multiplex-immunoassay. Serum concentrations of chromium and cobalt were determined by graphite furnace atomic absorption spectrometry. The serum concentrations of chromium and cobalt were lowest in patients with the C2a implant and highest with Magnum, some of these differences were significant at 6 weeks, 6 months, and 1 year after surgery. No patient had a very high serum metal concentration. The values of the variables measured in the in vitro lymphocyte assay mainly changed in the expected direction depending on the concentration of the same metal in the serum sample drawn at the same time, but no significant correlation was seen. One patient had uncertain symptoms of metal hypersensitivity and relatively high serum metal concentrations 3 years after arthroplasty with a Magnum prosthesis and was assessed extraordinarily, and elicited the marginally highest MIF responses in the lymphocyte assay. A strong correlation was found between the plasma concentrations of most cytokines, but the cytokine concentrations were not correlated to contemporary metal concentrations

INTRODUCTION. One of the recent advances in the hard-on-hard hip arthroplasty is the development of a new material of diffusion hardened oxidised zirconium (DHOxZr). The DHOxZr material consists of a ceramic layer on the top surface which is supported by a thick oxygen diffusion hardened (DH) zone underneath. With the desired properties of metal substrate, ceramic surface and a gradient structure of the oxygen diffusion zone, the DHOxZr-on-DHOxZr bearing combination is expected to produce low wear and minimal metal ions. This can possibly address the concerns associated with metal hypersensitivity associated with metal on metal bearings and fracture risk associated with ceramics. The aim of this study was to evaluate the wear of DHOxZr-on-DHOxZr as a possible hard on hard bearing combination in hips. METHODS. Three pairs of 50 mm DHOxZr prototype hip joint devices, each consisting of a DHOxZr modular head and a DHOxZr liner were wear tested in a ProSim hip joint simulator under standard testing conditions used by the Implant Development Centre (IDC), Smith & Nephew, Leamington Spa for 5 million cycles (Mc). The flexion/extension was 30° and 15°. The internal/external rotation was ± 10°. The force was Paul-type stance phase loading, with a maximum load of 3 kN and a standard ISO swing phase load of 0.3 kN. The test frequency was 1 Hz. Gravimetric analysis was carried out at 0, 0.5, 1, 2, 3, 4 & 5 million cycles. The lubricant was new born calf serum with 2 g/l sodium azide concentration diluted with de-ionised water to achieve average protein concentration of 20 g/l. Lubricant was changed every 0.25Mc during the first million cycles of the test and at every 0.33 Mc from 1 to 5Mc. RESULTS. A biphasic wear pattern was observed for the DHOxZr on DHOxZr devices during the test, with a running in phase from 0–1 Mc and a steady state phase from 1–5 Mc. At a confidence level of 95%, the mean wear rate was 0.21 ±0.06 mm3/Mc during the running-in stage, and the wear rate was reduced to 0.01 ±0.03 mm3/Mc during the steady state for the device tested. The wear volume loss of the DHOxZr on DHOxZr devices was significantly lower than that generated by CoCrMo metal on metal (MoM) devices (p < 0.05) under identical simulator test conditions

INTRODUCTION. The advantages of large diameter metal on metal total hip arthroplasty (MoM THA) and hip resurfacing arthroplasty are decreased wear rate, preservation of bone stock, anatomical restoration and enhanced stability. Large amounts of metal wear particles and metal ions are released which may induce adverse reactions including local soft tissue toxicity, hypersensitivity reactions, bone loss and risk of carcinogenesis. Aseptic loosening can be the result of a peri-prosthetic osteolysis generated as a result of a biological response to particulate wear debris. No reports in the literature exist as to whether circulating levels of Chromium (Cr) and Cobalt (Co) decrease upon removal of a symptomatic large diameter MoM implant or whether levels remain high due to the effect of metal ions debris left behind in the soft tissues after revision surgery. PATIENTS AND METHODS. Between June 2006 and June 2009 we undertook 44 revision surgeries of both large head MoM THAs (femoral head diameter 38mm) and metal-on-metal hip resurfacings for suspected metallosis. Mean time from original implant to revision was 4 years, 8 months (1yr 4mo–7yr 9mo). The mean follow up evaluation was 2 years and 2 months (1yr 2mo–4 years). Blood samples were taken for whole blood Cr and serum Co according to a recognised protocol and compared with reference levels indicated by the Medicines and Healthcare Regulatory Agency recommendation of less than 7ppb for Cr (130nM/L) and Co (119nM/L). RESULTS. 42 patients were found to have histological evidence of either metal allergy, metal toxicity or foreign body reaction. 2 patients had evidence of infection with no features of metal reaction. 3 patients suffered early dislocation requiring closed reduction. 1 patient had infective complications necessitating Girdlestones. 11 patients were lost to follow up, 8 patients were diagnosed pre operatively on Co and Cr levels in urine or synovial fluid aspirate alone. 23 patients had pre revision blood or serum metal ion level results available for direct comparison. Median serum Co level pre revision was 176.6nM/L, falling post revision to 5.1nM/L (p=<0.001∗). The median whole blood Cr level pre revision was 117nM/L and 19nm/L post revision (p=<0.001∗). Mean Oxford Hip Score was 23.7. DISCUSSION. This study demonstrates that at greater than one year post removal of a large diameter MoM hip implant for the indication of symptomatic metallosis or metal hypersensitivity, metal ion levels fall to almost normal levels and that outcome of revision surgery in terms of patient satisfaction is not adversely affected