FP1.3 Risk Factors and Risk Prediction for Superior Pubic Ramus Nonunion After Bernese Periacetabular Osteotomy for Adult Developmental Dysplasia of the Hip: A Retrospective Study of 406 Hips

Abstract

Abstract ICLB01 - The Instability Masterclass: Correcting Bone, Biology, and Bad Outcomes, Session Room 6 (BMCC Level 3), October 8, 2026, 10:30 - 12:30 Objective To identify risk factors for nonunion of the superior pubic ramus following periacetabular osteotomy (PAO) and to develop a predictive model for identifying patients at high risk. Methods We retrospectively reviewed 321 patients (406 hips) who underwent PAO between July 2019 and June 2023. Variables collected included age, body mass index (BMI), correction of the lateral center-edge angle (C-LCEA), correction of the anterior center-edge angle (C-ACEA), correction of the Tönnis angle (C–Tönnis angle), distance from the pubic ramus osteotomy site to the ilioischial line (mm), difference in ilium–ischium distance, preoperative International Hip Outcome Tool–12 (iHOT-12) score, and Harris Hip Score (HHS). Variable selection was performed using least absolute shrinkage and selection operator (LASSO) regression. Independent risk factors were identified using multivariable logistic regression, and a nomogram was constructed. Model performance was evaluated by the area under the receiver operating characteristic curve (AUC) and the Hosmer–Lemeshow test. Results At a mean follow-up of 28.8 months, nonunion occurred in 63 hips (15.5%). LASSO regression identified four independent predictors: distance from the pubic ramus osteotomy site to the ilioischial line (OR = 1.50, 95% CI: 1.29–1.76; P < 0.001), preoperative lateral center-edge angle (OR = 1.19, 95% CI: 1.13–1.25; P < 0.001), age (OR = 1.13, 95% CI: 1.07–1.20; P < 0.001), and preoperative iHOT-12 score (OR = 0.95, 95% CI: 0.92–0.99; P = 0.007). The model demonstrated excellent discrimination (AUC = 0.904, 95% CI: 0.86–0.95) and good calibration (Hosmer–Lemeshow test, P = 0.095). Conclusion The incidence of superior pubic ramus nonunion after PAO was 15.5%. A greater distance between the osteotomy site and the ilioischial line, larger correction of the lateral center-edge angle, older age, and lower preoperative iHOT-12 scores were independently associated with nonunion. The nomogram based on these variables showed good predictive performance and may facilitate early identification of high-risk patients. Targeted strategies to promote osteotomy healing should be considered in patients with these risk factors.