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Objectives and questions: 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. The primary aims were (1) to characterize the early clinical recovery after PAO and determine the timing and rate at which patients achieve clinically meaningful improvement thresholds – namely the minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient-acceptable symptom state (PASS) – within the first two years after surgery; and (2) to identify patient- and surgery-specific predictors associated with the likelihood of reaching these thresholds. We hypothesized that most patients would reach clinically meaningful improvement thresholds within the first two postoperative years and that patient- and surgery-specific factors would be associated with the likelihood of achieving these thresholds.

Material and methods: This prospective multicenter cohort study is a secondary analysis of a randomized trial including 218 patients (age 27.1±7.7 years; 83.2% female) undergoing PAO with or without hip-arthroscopy.

Aims: 1) determine 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 International Hip Outcome Tool (iHOT-33) within 24 months, and 2) identify predictors of threshold achievement. Correction was assessed by lateral-center-edge-angle (LCEA) and acetabular index. Logistic regression evaluated patient- and surgery-specific factors.

Results: Radiographic parameters improved significantly (LCEA: 18.7±8.4° to 32.2±5.7°; acetabular index: 12.8±7.6° to 1.6±6.3°; both p < 0.001). iHOT-33 improved from 34.2±16.4 preoperatively to 61.4±24.0 (6 months), 72.8±22.0 (12 months), and 78.0±21.0 (24 months) (p < 0.001). At 6, 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: 0.88–0.89, p < 0.05). Residual undercorrection, reflected by higher postoperative acetabular index, reduced odds of MCID and SCB (OR: ~0.80, p < 0.05). Older age lowered likelihood of PASS (OR:0.94, p = 0.047). Labral repair was negatively associated with PASS at 6 months (OR:0.27, p = 0.031) but not thereafter.

Discussion and conclusions: In conclusion, while most patients reached MCID, SCB, and PASS within 12 months, recovery continued into the second year for many, albeit at a slower pace. Patient-specific factors such as higher BMI, older age, and residual undercorrection of the acetabulum were associated with lower odds of achieving these thresholds, underlining their role in shaping early postoperative outcomes.