Characteristics of sagittal spinopelvic alignment in hip osteoarthritis with developmental dysplasia of the hip.

PURPOSE: This retrospective observational study investigated sagittal spinopelvic alignment and lumbar degeneration in patients with end-stage hip osteoarthritis (OA) secondary to developmental dysplasia of the hip (DDH). METHODS: The study involved 95 DDH patients undergoing total hip arthroplasty (THA) and 95 propensity-matched healthy controls. Pelvic incidence (PI), lumbar lordosis (LL), sacral slope (SS), PI-LL, and sagittal vertical axis (SVA) were assessed using standing whole-spine radiography. Lumbar degeneration was graded via Esposito classification. Pre- and postoperative DDH spinopelvic parameters and baseline controls were compared. RESULTS: Preoperatively, DDH patients showed a significantly greater SS (32.0° vs. 27.8°, P = 0.0014) and anterior SVA (39.0 mm vs. 21.4 mm, P = 0.0005), whereas PI and LL did not differ significantly. Lumbar degeneration was more prevalent in DDH patients (Median Esposito's score was 5 (IQR 3-6) vs. 2 (IQR 1-3), P < 0.0001). Postoperatively, the DDH patients exhibited significant reduction in PI-LL (7.5° vs. 6.2°, P = 0.0079), PI (49.5° vs. 47.5°, P < 0.0001), SS (32.0° vs. 30.0°, P < 0.0001) and SVA (39.0 mm vs. 31.7 mm, P = 0.0273), approaching values observed in healthy individuals. CONCLUSION: End-stage hip OA caused by DDH is characterized by anterior pelvic tilt and forward trunk shift without an increase in LL, potentially associated with concomitant lumbar degeneration. THA partly restores hip center and spinopelvic alignment, supporting the importance of spinal evaluation in surgical planning.