Heat generated by hip resurfacing prostheses: an in vivo pilot study.

In order to determine the magnitude of temperature increases in resurfaced hips, temperature sensors were placed percutaneously in both hip joints of 12 volunteer patients who had 1 or both joints resurfaced. Temperature recordings were made with patients at rest (baseline) and after patients walked for 20 and 60 minutes. The hip resurfacing procedures were performed 12 to 36 months prior to this study using 9 different acetabular bearing surface components. At baseline (resting), a ceramic femoral prosthesis articulating with a poly-ether-ether-ketone (PEEK) acetabular prosthesis generated a temperature increase of 4°C compared to a normal contralateral hip. After 60 minutes of walking, a ceramic femoral prosthesis articulating with a polyurethane acetabular prosthesis generated a temperature increase of 5°C, whereas a ceramic femoral prosthesis articulating with a metal acetabular prosthesis generated a temperature increase of 6°C, a cobalt-chromium alloy femoral prosthesis on a polyethylene acetabular prosthesis generated a temperature increase of 7°C, and a cobalt-chromium alloy metal-on-metal prosthesis generated a temperature increase of 8°C. Resurfaced hips generate more heat than arthritic and normal hips, and arthritic hips generate more heat than normal hips. A resurfaced hip with a ceramic femoral and PEEK or polyurethane acetabulum generated less heat than a resurfaced hip of the same design using a cobalt-chromium femur and either cobalt-chromium, or polyethylene for the acetabulum. Frictional heat generated in a resurfaced hip is not immediately dissipated and may result in increased bearing surface wear. Extended periods of elevated temperature within joints may inhibit periarticular cell growth and perhaps contribute to bone resorption or component loosening over the long term.