The concept of osteoarthrotic remodelling as illustrated by ochronotic arthropathy of the hip. An anatomico-radiological approach.

This report is an anatomico-radiological study of six femoral heads excised from four patients with diffused ochronotic arthropathy. In one case a biopsy specimen taken eleven years earlier was also studied. The deterioration of the ochronotic cartilage involves a fragmentation process reflected by histological characteristics that are different from those observed in common "cartilaginous degeneration". The fragments resulting from this process become embedded in the remodelled bone-marrow tissue of the weight-bearing zone and in the synovial membrane. Except for the presence of pigmented cartilage, the intrinsic osteogenic remodelling and the extrinsic osteophytic remodelling (the latter often appearing in the form of minor equivalents) are similar to that of the common form of osteoarthrotic remodelling. The pigment labelling of the ochronotic cartilage provides a particularly favorable opportunity to study the general problem of osteoarthrotic remodelling; it facilitates the differentiation between newly formed and preexisting tissue and consequently our understanding of the entire process. An anatomico-radiological approach provides an explanation for the similarity frequently observed on X-rays between ochronotic and rheumatoid hip arthropathies.