Twenty-one acetabular osteophytes in osteoarthritic hips were studied by means of X-ray and histological examination using tetracycline labelling method. The osteophyte could be observed most clearly by tomography pre-operatively. Intense tetracycline fluorescence was seen along the osteo-chondral junction of the osteophyte. As for the distribution of tetracycline, fluorescence of the osteophyte was similiar to that of capital drop. Intense tetracycline fluorescence at the osteo-chondral junction of the osteo-phyte was seen in 16 joints, mild in 4 joints, and no fluorescence in one joint. The tetracycline uptake was more prominent in the unstable osteoarthritic hip.
