Serum metal ion levels after rotating-hinge knee arthroplasty: comparison between a standard device and a megaprosthesis.

PURPOSE

The effects of systemic metal ion exposure in patients with implants made of common prosthetic alloys continue to be a matter of concern. The aim of the study was to determine the measurement values of cobalt (Co), chromium (Cr) and molybdenum (Mo) in serum following rotating-hinge knee arthroplasty.

METHODS

Blood was taken from 25 patients [mean follow-up 35 (range nine to 67) months] treated with megaprostheses (n=17) or standard rotating-hinge devices (n=8) and analysed using electrothermal graphite furnace atomic absorption spectrometry (ET-ASS).

RESULTS

Determining the concentrations of metal ions following rotating-hinge knee arthroplasty revealed increments for Co and Cr but not Mo. Metal ion release was significantly higher in patients with megaprostheses compared to a standard rotating-hinge knee device (Co p=0,024; Cr p=0.025).

CONCLUSION

The authors believe there might be an additional metal ion release from the surface of the prosthesis and not only from the articulating surfaces because, in cases of rotating-hinge knee prosthesis, there is a metal-on-polyethylene articulation and not a direct metal-on-metal junction. Nevertheless, long-term studies are required to determine adverse effects of Co, Cr and Mo following total hip replacement and total knee arthroplasty.