FP7.2 Patient-Specific Osteotomy Plane Configuration Optimises Femoral Head Coverage and Bone Overlap in Bernese Periacetabular Osteotomy for Hip Dysplasia: A Three-Dimensional Simulation Study

Abstract

Abstract ICLB07 - The Digital Surgeon: Practical Tools and Navigation Basics for Your Everyday Practice, Session Room 12 (BMCC Level 3), October 8, 2026, 14:00 - 16:00 Background Hip dysplasia (HD) produces a structurally deficient acetabulum with insufficient femoral head coverage (FHC), generating pathological concentration of joint contact stress that drives early osteoarthritis. The Bernese periacetabular osteotomy (PAO) corrects this by repositioning the acetabular fragment to normalise load distribution across the articular surface. Despite established technique, the influence of individual osteotomy plane location and angulation on coverage indices and bone overlap at osteotomy planes has not been systematically evaluated. Methods Using a 3D PAO Planner, 278 simulated PAOs with standardised targets were performed on each of eight dysplastic hips representing the spectrum of HD severity. One hundred and eight combinations of iliac plane location (0, 5, 10 and 15 mm distal to the anterior-superior iliac spine [ASIS]) and gradient, and pubic plane angle (50°, 70°, 90°) and distances medial to the iliopectineal eminence were evaluated. Primary outcomes were post-operative lateral centre-edge angle (LCEA), Tönnis angle, percentage FHC, and bone overlap at each osteotomy plane. Results All feasible PAOs improved LCEA, Tönnis angle, and FHC. Patient-specific plane combinations improved FHC beyond the standard configuration without impingement in all eight hips. Iliac plane location at 10mm and 15mm distal to the ASIS significantly improved LCEA and Tönnis in six of eight hips (Kruskal-Wallis p<0.05). Pubic plane configuration did not significantly alter coverage metrics but cuts closer to the eminence correlated with pubic bone overlap (Spearman r = −0.82, p<0.001). The standard combination failed the minimum 10% bone overlap feasibility criterion in the two most severely dysplastic hips; patient-specific plane selection restored feasibility. Conclusions Positioning the iliac plane 10–15 mm distal to the ASIS is a primary modifiable determinant of coverage improvement in Bernese PAO for HD. In severe dysplasia, standard plane placement may be inadequate for both correction and structural stability, underscoring the clinical benefit of pre-operative 3D planning.