A cadaveric investigation into the links between macroscopic and microscopic osteoarthritic changes at the hip.

Our objective was to investigate the frequency and distribution of osteoarthritic changes at the hip, including the relationship between osteoarthritic lesions on the femoral head surface and histological changes in articular cartilage, in 12 cadavers. Twelve embalmed cadavers (five males and seven females) were dissected, and the femoral head was removed from both sides (24 femoral heads). Any gross osteoarthritic changes were noted and graded (on a scale of 1-3). A circular disc was then removed from the equator of the femoral head and divided into nine regions. Out of 192 segments, 54 underwent sectioning and staining with haematoxylin and eosin to assess histological changes in cartilage. Osteoarthritis of the hip was present in all cadavers, with all males having bilateral OA and 50% having grade 2 or higher lesions (50% were grade 1), and four of the seven female specimens having bilateral OA and only 7% with grade 2 lesions (with 71% grade 1 and 21% normal). Chondrocyte clustering was most commonly observed in the deep layer of cartilage followed by the intermediate and superficial layers respectively, as the grade of the macroscopic lesion increased. Cartilage injury at the histological level precedes any visible denudation of the femoral head articular cartilage. This study supports the hypothesis that early osteoarthritic changes occur in the deep layer of cartilage near the tide mark and progress superficially concomitant with an overall increase in the osteoarthritic lesion size on the femoral head surface.