Histomorphometric case-control study of subarticular osteophytes in patients with osteoarthritis of the hip

OBJECTIVE: The objective of this cross-sectional case-control study was to determine the prevalence and size of marginal and subarticular osteophytes in patients with osteoarthritis (OA), and to compare these to that of a control group. DESIGN: We investigated femoral heads from 25 patients with OA following hip replacement surgery, and 25 femoral heads from a control group obtained post-mortem. The area and boundary length of the femoral head, marginal osteophytes, and subarticular osteophytes were determined with histomorphometry. Marginal osteophytes were defined histologically as bony projections at the peripheral margin of the femoral head, while subarticular osteophytes were defined as areas of bone that expanded from the normal curvature of the femoral head into the articular cartilage. RESULTS: The prevalence of OA patients with marginal- and subarticular osteophytes were 100 and 84%, respectively. Whereas the prevalence of the participants in the control group with marginal- and subarticular osteophytes were 56 and 28%, respectively. The area and boundary length of marginal osteophytes was (median (Interquartile range)) 165.3mm(2) (121.4–254.0) mm(2) and 75.1 mm (50.8–99.3) mm for patients with OA compared to 0 mm(2) (0–0.5) mm(2) and 0 mm (0–0.5) mm for the control group (P < 0.001). For the subarticular osteophytes, the area and boundary length was 1.0 mm(2) (0–4.4) mm(2) and 1.4 mm (0–6.5) mm for patients with OA compared to 0 mm(2) (0–0.5) mm(2) and 0 mm (0–0.5) mm for the control group (P < 0.001). CONCLUSION: As expected, both marginal- and subarticular osteophytes at the femoral head, were more frequent and larger in patients with OA than in the control group. However, in the control group, subarticular osteophytes were more prevalent than expected from the minor osteophytic changes at the femoral head margin, which may suggest that subarticular osteophytes are an early degenerative phenomenon that ultimately might develop into clinical osteoarthritis.