EVALUATION OF FIBROCARTILAGE REGENERATION AND BONE RESPONSE AT FULL-THICKNESS CARTILAGE DEFECTS IN ARTICULATION WITH PYROLYTIC CARBON OR COBALT-CHROMIUM ALLOY HEMIARTHROPLASTIES

Hemiarthroplasty is one method used to treat osteoarthritic joints. Of ten, however, an adverse response of the articular cartilage to the me tal implants occurs. The purpose of this study was to evaluate and com pare the response of a surgically created defect to pyrolytic carbon a nd cobalt-based alloy hemiarthroplasties. The cartilage on the lateral side of the tibial plateau of a canine knee joint was abraded to crea te a full-thickness defect. Two small holes were drilled into the expo sed subchondral bone. Next, either a carbon or metal implant was place d in the lateral femoral condyle. The implantation period was 1 year. Histologic examination of the tibial defects revealed a smooth bony su rface for both implant groups. In addition, there was no evidence of a residual adverse inflammatory response nor of a significant increase in subchondral bone formation for either group. Surface cracks resulti ng from the presence of the implant were seen in 14% of the carbon imp lant specimens and in 100% of the metal implants. Fibrocartilage regen eration was seen in 86% of the carbon implants and in 25% of the metal implants. Thus the carbon appears to be better tolerated mechanically compared to wrought cobalt-chromium alloy. Pyrolytic carbon shows pro mise for use in hemiarthroplasty. (C) 1998 John Wiley & Sons, Inc. J B iomed Mater Res, 41, 534-540, 1998.