Functional response to total hip arthroplasty in patients with hip dysplasia

Background: While recent studies have shown patients with developmental dysplasia of the hip (DDH) undergoing total hip arthroplasty (THA) to achieve comparable post-operative outcomes to patients with primary osteoarthritis (OA), it is unclear whether DDH patients display better or worse preoperative function than the general THA population. We aimed to compare the preoperative function and functional response to THA of DDH patients with OA patients. Methods: Through a retrospective review of prospectively collected regional joint registry data, we compared the preoperative, 1-year post-operative and post-operative change in disease-specific (Oxford hip score (OHS), Western Ontario and MacMaster Universities Osteoarthritis Index (WOMAC)) and general health (short form 12 physical health (SF-12 PH), mental health (SF-12 MH) scores) functional scores of 33 DDH patients and 968 OA patients undergoing primary THA. Results: The DDH group displayed substantially worse preoperative function than the OA group (mean OHS 11.2 versus 16.3 (P = 0.001), WOMAC 72.7 versus 60.6 (P < 0.001), SF-12 PH 27.8 versus 28.9 (P = 0.433), SF-12 MH 35.5 versus 44.7 (P < 0.001)). Functional response to THA at 1 year was significantly better in the DDH group than the OA group (mean score improvements: OHS 31.1 versus 24.6 (P < 0.001), WOMAC 61.4 versus 47.2 (P < 0.001), SF-12 PH 22.3 versus 16.5 (P = 0.003), SF-12 MH 18.4 versus 8.4 (P < 0.001)). Conclusion: Despite experiencing significantly worse preoperative function, DDH patients undergoing THA demonstrated superior early functional response to OA patients, with substantially greater improvements observed in all disease-specific and general health outcome measures.