Synovial, articular cartilage and bone changes in rapidly destructive arthropathy (osteoarthritis) of the hip

We studied ten femoral heads from eight patients suffering from rapidly destructive arthropathy (RDA) of the hip. At surgery, 1-3.5 ml of synovial fluid, ranging from citrous to hemorrhagic, was aspirated from six joints. This fluid was viscous, pauci-cellular and did not contain calcium pyrophosphate dihydrate (CaPPD) crystals, although significant amounts of alizarin S-positive material was found in three joints. Significant synovial hyperplasia was found in four joints and moderate hyperplasia in two. Synovium was hypertrophic, hypercellular and slightly to moderately fibrotic. It lacked evidence of perivascular inflammatory infiltrates. Synovium often contained amyloid micro-deposits and alizarin S-positive osteocartilagenous debris surrounded by macrophages. Synovial hyperplasia had a good correlation with osteocartilagenous debris and a poor correlation with amyloid infiltration. Femoral heads were usually flattened and exhibited large areas of exposed bone spotted by plugs of fibro-cartilagenous tissue. Subchondral bone contained large ischemic and necrotic areas, bone marrow atrophy and fibrosis, and intense bone remodeling. Subchondral bone necrosis and ischemia were the most significant findings of this study and their role in the development of RDA is discussed.