Three-dimensional Acetabular Coverage Following Periacetabular Osteotomy: Comparison With Population-based Threshold Values Using Acetabular Sector Angles

Background Periacetabular osteotomy (PAO) is a complex joint-preserving surgery for acetabular dysplasia. While traditionally focused on achieving superior femoral head coverage, the three-dimensional (3D) nature of acetabular morphology requires comprehensive assessment. Recently established population-based threshold values for acetabular sector angles (ASA) enable quantitative evaluation of dysplasia, but their relationship to post-PAO coverage remains unexplored. Methods This retrospective cross-sectional study included 33 patients (18 females, 15 males; mean age 23.4 years) who underwent unilateral PAO between January 2015 and December 2020. Preoperative and postoperative ASA measurements were obtained from standardized CT scans at four anatomical levels: superior, proximal, intermediate, and equatorial. Values were compared with contralateral normal hips and recently published dysplasia threshold values. Harris Hip Scores were recorded pre- and postoperatively. Results Harris Hip Scores improved significantly from 56 to 89 postoperatively (p < 0.001). Superior ASA increased from 108.5° to 129.0° (p < 0.001, Cohen's d = 1.92). Proximal posterior ASA increased by 21.8° (p < 0.001), and proximal anterior ASA by 11.9° (p = 0.025). Postoperative coverage approached contralateral hip values but remained below population-based thresholds for dysplasia at most levels. Notably, contralateral "normal" hips also fell below established thresholds. Conclusions PAO significantly improves 3D acetabular coverage, particularly in superior, posterolateral and superiolateral regions. However, both operated and contralateral hips demonstrate morphological features below population-based dysplasia thresholds, suggesting that surgical success criteria may differ from population norms. Radar chart visualization facilitates comprehensive assessment of acetabular morphology for surgical planning.