COBALT AND CHROMIUM LEVELS FOLLOWING METAL-ON-METAL HIP RESURFACING WITH THE CORMET 2000 PROSTHESIS

Abstract

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.