Introduction: Metal-on-metal (MOM) hip resurfacing is becoming a more accepted and available option to consider when treating increasingly younger and more active patients. Advantages include preservation of bone stock and a larger femoral head which increases range of motion without risk of dislocation. We report here the effects of gender on revision rates in patients receiving the Cormet 2000 MOM Hip Resurfacing System.

Methods: 1058 hips were implanted in a multicenter, prospective study. All patients received a cementless, press-fit Cobalt Chrome acetabular shell with plasma sprayed titanium and HA coating and cemented Cobalt Chrome femoral head. Patients were evaluated pre-operatively through 2 years using standardized questionnaires, physical examinations, and radiographic evaluations.

Results: There were 754 males (71%) and 304 (29%) females implanted with the device. Thirty-eight (3.6%) revisions were required; 19 females (6.3%) and 19 (2.5%) males. Males had risk factors significant for revision including increased age in 10-year increments and smaller implant size. Trending but not significant (p=0.08) was lower preoperative HHS.

Discussion and Conclusion: There was a difference in revision rates between males and females, likely due to a difference in bone mass and stability. Based on these findings, the optimal patient seemed to be a larger, younger, more active male. This population has previously been identified to be at most risk after THA and utilization of a resurfacing device may be a good alternative. In addition, future studies designed to optimally select females for MOM hip resurfacing may reduce the revision rate in that population.

Introduction: Metal-on-metal (MOM) hip resurfacing releases ions locally and into the systemic circulation, raising concern for potential long term complications of elevated trace metals. This study was designed to monitor serum cobalt (Co) and chromium (Cr) levels in patients after MOM resurfacing hip arthroplasty with the Cormet 2000 prosthesis and to compare detected levels with those previously reported for hip resurfacing prostheses.

Methods: We prospectively followed patients receiving the Cormet 2000 device. Serum samples were collected at 6 months, 1, 2, and 3 years following surgery. Pre-operative controls were obtained from subjects without implants. Serum Co/Cr levels were determined using high-resolution inductively coupled plasma mass spectrometry. ANOVA was used to compare ion levels in each group. Statistical significance was set at p< 0.05.

Results: 40 subjects (25 male) were followed. Average age was 51 years (33.7–66.1). Median preoperative Co/ Cr levels were 0.27 microg/L (0.087–0.601) and 0.19 (0.014–0.576), respectively. Co/Cr levels were significantly increased at all time points when compared to preoperative levels (p< 0.001). Peak Co and Cr levels were observed at 1 year (3.26 and 4.42, respectively). At three years, the median Co and Cr levels had dropped to 2.08 and 3.55, respectively, but this was not statistically significant.

Conclusion: Elevated serum Co/Cr levels were observed at all time points following implantation. Continued elevations at three years were observed; however, the levels appear to be trending down suggestive of a “wear-in” period. Long term elevations of Co/Cr levels are concerning and will require additional studies to assess long term health risks of these levels in this population.