Epidemiological, clinical, biological and radiological differences between atrophic and hypertrophic patterns of hip osteoarthritis: a case-control study.

OBJECTIVE Lack of osteophytes (atrophic form) has been shown to be a factor in the severity of hip osteoarthritis (OA). The aim of this study was to determine the epidemiological, radiological and biological differences between the hypertrophic and atrophic forms of hip osteoarthritis. METHODS 25 patients with symptomatic hip OA (ACR criteria) and classified as having an atrophic form of OA based on the lack of osteophytes on standard radiograph of the pelvis, were matched for joint space width with 25 subjects with evidence of the hypertrophic form of hip OA. OA radiological severity was assessed using a scoring system and by computer measurement of the joint space width. Angles of hip dysplasia were measured. Serum hyaluronic acid, cartilage oligomeric matrix protein, collagenase, Type I procollagen, C-terminal crosslinking telopeptide of type I collagen and tissue inhibitor of métalloproteases-1 were assayed by immunoassay and C-reactive protein by ultrasensitive immunonephelemetry. Statistical analysis was performed using logistic regression, taking into account age, sex, body mass index, and bilaterality. RESULTS Compared to hypertrophic OA, atrophic OA affected chiefly elderly women and was characterized by a smaller centre-edge angle and diffuse superior femoral head migration. It was less frequently bilateral. No statistically significant difference was found in the biological data between the two groups. CONCLUSION An atrophic bone response in hip OA occurs chiefly in women and is associated with poor coverage of the femoral head. Serum biomarkers able to demonstrate differences between the atrophic and hypertrophic patterns of OA are lacking.