| Background:Hip resurfacing is a bone conserving procedure. It began as a major evolution of hip arthroplasty in the beginning of the21st century. The popularity of this surgery in the United States and Europe is already undeniable; Australia is most likely to soon follow However, concerns about metal ion release, cancer, osteolysis, and hypersensitivity remain. Osteonecrosis has been reported in femoral head removed after failure of hip resurfacing. Many clinical studies have described many possible causative factors. Many reports have described failure mechanisms of hip resurfacing. There is little information in the literature to guide clinical evaluation and management. There is still no clear proof for avoiding use of this implant. Chinese patients have different distribution of hip diseases compared to other race patients. The predominant diagnosis was osteonecrosis (40%) and developmental dysplasia (35%). The aim of this study was to find out the actual clinical and laboratory results of metal on metal resurfacing hip arthroplasties by comparing with other implants.Objectives:To analyze the association of osteonecrosis and elevated metal ions level in revision cases.A total of127cases were operated at the department of Orthopaedics of Wuhan Union hospital from2005to2011. The serum metal ions level was detected by comparing the MOM bearing in different diameter of resurfacing hip arthroplasties and control groups. The clinical result was assessed by Harris Hip score, UCLA activity score, DeLee and Amstuz radiological score and SF-12form.Serum metal ions analysis was done by ICP-MS on a Perkin-Elmer SCIEX Elan6100DRC plus at the central laboratory of Huazhong University of Science and Technology.Results:The ion levels were compared with MOM large diameter head arthroplasty, conventional THR and normal control groups. Fifteen cases in each group, which were matched by age, weight, side and follow-up period. The mean age at the time of surgery was56years (range:28.2-75.5years). The minimum follow up was3months (mean:17.29±9.46months, range:3-48months). We analyzed histological series of3retrieved specimens with a preoperative diagnosis of Ficat type2ON (n=1) and rhuematoid arthritis (RA)(n=2). The serum metal ions concentration of MOM hip resurfacing was higher than that of the control groups (Co:3.02±1.52μg/L vs.0.729±0.32μg/L, p=0.001),(Cr:2.31±1.12μg/L vs.1.21±0.13μg/L, p=0.013),(Ni:8.76±2.03μg/L vs.4.96±0.79μg/L, p=0.000) and (Ti:1.53±1.5μg/L vs.0.43±0.11μg/L, p=0.041). No features of implants failure in radiological assessment. Established avascular necrosis of the femoral head was found in these3cases who sustained post operative fractures. Periprosthetic tissues showed metallosis, extensive lymphocytic and plasma cell infiltration around the metal debris. Patients with ON had more extensive ON than patients with RA. There are increased in metal ions levels as chromium, cobalt, nickel and titanium level were statistically significantly elevated in metal on metal resurfacing hip arthroplasty.The ions level elevation was influenced by patient activity, diet, diameter, duration.lt was found that the chromium and cobalt were highly raised in bilateral resurfacing hip arthroplasty patient who was complicated with pseudo tumor like lesion around the hip. The ions level was also increased in the3patients of the femoral neck fractures after this surgery.An important cause of failure is the fracture of the femoral neck.The chromium and cobalt level of resurfacing hip arthroplasty and large diameter head total hip arthroplasty (THA) are higher than conventional metal on polyethylene THA. There was a high ions level associated with abduction angle more than45degree and repetitive extreme hip motion in the three revision cases. Discussion:We are currently analyzing the research on the cause of the fracture which is due to ON or increase production of ions for the rational conclusion. The toxicological consequences are unknown up to now. This study data suggest that hip resurfacing is very careful to be considered especially in ON.Conclusion:It is concluded that the cause of failure is not only mechanical factors but also the avascular necrosis of the head after operation. This novel Chinese clinical information would be valuable for the practicing surgeon faced with MOM hip resurfacing patient’s population. Long term datas are still necessary to identify the potential risk and the incidence of metal hypersensitivity reaction. There can be demonstrable long term survivorship of MOM resurfacing hip arthroplasty and to determine the chronic elevation in systemic metal content whether there is the toxicologic significance or not. The findings of this study are novel and quite controversial with that of the previously published literature. |
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