Osteoarthritis of the hip. Possible protective and causative roles of trabecular microfractures in the head of the femur.

In contrast to the large volume of data on the cartilage and synovial fluid changes, there has been relatively little investigation of the involvement of bone in the genesis of osteoarthritis (OA). Previous researchers have hypothesized that OA follows stiffening of subchondral bone through trabecular microfractures. Although it is widely recognized that marked changes in the subchondral bone are a consistent feature of advanced OA, the nature of the changes in the bone in OA has not received significant attention. The heads of the femur from 67 patients who had joint replacement for advanced OA and 66 autopsy controls without discernible joint disease were examined microscopically to ascertain the number and distribution of trabecular microfractures in coronal slabs and to quantify the mineralization and thickness of trabecular bone in a principal compressive zone. There was a reduction in the number of trabecular microfractures in OA patients, compared with the controls, with a lack of correlation between numbers of microfractures and age in OA patients. There was no evidence for the hypothesis that increased numbers of microfractures led to the increase of bone to support the view that microfractures play a role in maintaining OA joint structure. Structural changes produced relatively sclerotic and porotic groups of OA and two subgroups of the sclerotic group.