O3331 HISTOLOGICAL FINDINGS IN RETRIEVED FEMORAL HEAD REMNANTS FOLLOWING REVISION OF HIP RESURFACING ARTHROPLASTY FOR EARLY FAILURE

Abstract

Aims: To determine the pathological changes in the femur following resurfacing hip arthroplasty and identify possible causes of early failure. Methods: Bone samples from 8 femoral heads at several levels were examined histologically following removal of cemented femoral head surface replacement following aseptic early failure: 4 neck fractures (no history of fall), 3 persistent severe pain and 1 cup loosening. Intra-operatively no obvious macroscopic causes of failure (including notching the neck) were noted. In all patients, the initial diagnosis had been osteoarthritis. None had known risk factors for osteonecrosis. Results: In the patients who had recent fracture, the bony changes were suggestive of relatively longstanding osteonecrosis with degenerative, necrotic and þbrotic changes in the bone marrow and loss of osteocyte nuclei in the trabeculae. There was appositional new bone formation at the surface of the necrotic bone trabeculae. The changes were consistent with osteonecrosis of more than 2 weeks duration and probably preceded the fracture in all cases. In the patients who underwent revision for non-fracture, some osteonecrosis was seen, but this was a lot less than when a fracture had occurred. Conclusion: Osteonecrosis of the femoral head is seen following resurfacing hip arthroplasty and may be a predisposing factor in patients who subsequently fracture.