Recovery trajectory and patient-specific predictors following periacetabular osteotomy

Aims: Periacetabular osteotomy (PAO) is the gold-standard treatment for symptomatic hip dysplasia. While long-term joint preservation and functional improvement are documented, early postoperative recovery trajectories and predictors of meaningful improvement remain unclear. Methods: This prospective multicentre cohort study is a secondary analysis of a randomized trial including 218 patients (mean age 27.1 years (SD 7.7); 83.2% female (181/218)) undergoing PAO with or without hip arthroscopy. We aimed to 1) determine the timing and proportion of patients achieving minimal clinically important difference (MCID, + 26), substantial clinical benefit (SCB, + 42), and patient-acceptable symptom state (PASS, ≥ 65) on the 33-item International Hip Outcome Tool (iHOT-33) within 24 months; and 2) identify predictors of threshold achievement. Correction was assessed by lateral centre-edge angle (LCEA) and acetabular index. Logistic regression evaluated patient- and surgery-specific factors. Results: Radiological parameters improved significantly (mean LCEA 18.7° (SD 8.4°) to 32.2° (SD 5.7°); acetabular index 12.8° (SD 7.6°) to 1.6 (SD 6.3°), both p < 0.001). iHOT-33 improved from 34.2 (SD 16.4) preoperatively to 61.4 (SD 24.0) at six months, 72.8 (SD 22.0) at 12 months, and 78.0 (SD 21.0) at 24 months (p < 0.001). At six, 12, and 24 months, MCID was achieved by 70.2%, 71.5%, and 80.3% of patients; SCB by 52.8%, 64.6%, and 74.6%; and PASS by 56.3%, 73.5%, and 79.6%. Most recovery occurred within the first year, with continued gains thereafter. Multivariable analysis identified higher BMI as negative predictor for MCID, SCB, and PASS at 12 months (OR 0.88 to 0.89; p = 0.015 to 0.019). Residual undercorrection, reflected by higher postoperative acetabular index, reduced odds of MCID at 12 months (OR ~ 0.80 (95% CI 0.67 to 0.95); p = 0.011). Older age lowered the likelihood of PASS (OR 0.94 (95% CI 0.89 to 0.999); p = 0.047). Labral repair was negatively associated with PASS at six months (OR 0.27 (95% CI 0.09 to 0.89); p = 0.031), but not thereafter. Conclusion: Most patients achieve clinically meaningful improvement within the first postoperative year, with further recovery into the second. Elevated BMI, older age, and residual undercorrection reduce the likelihood of reaching thresholds, while concomitant labral repair may temporarily delay early symptom acceptability.