Virtual Periacetabular Osteotomy and Anatomical Measurements

Abstract

Objective: To report on a CT scan virtual periacetabular osteotomy (PAO) process to evaluate the potential risk of different PAO cutting planes.

Methods: A total of 123 patients (64 men and 59 women) underwent virtual PAO. We defined two retroacetabular cutting (RC) planes: the RC plane and the RC⁺ plane (10 mm posteriorly as compared to the RC plane). Subsequently, we measured the anatomical minimum distance between the acetabulum and the sciatic notch, the minimum distance between the acetabulum and the retroacetabular cutting plane (osteotomy of the posterior column), and the osteotomy length in the cranio-caudal direction.

Results: The mean (standard deviation [SD]) minimum distance between the acetabulum and the sciatic notch was 25.82 ± 3.52 mm (95% confidence intervals [CI], 25.36-26.25 mm). In men, the mean (SD) minimum distance between the acetabulum and sciatic notch (27.18 ± 3.47 mm; 95% CI, 26.56-27.78 mm) was significantly (3 mm) larger than in women (24.34 ± 2.92 mm; 95% CI, 23.82-24.89 mm; P < 0.001). The mean (SD) minimum distance between the acetabulum and the retroacetabular plane was significantly larger for the RC⁺ plane (6.97 ± 0.91 mm) than for the RC plane (P < 0.001). In men, this distance (10.23 ± 3.84 mm) was significantly (2.3 mm) larger than in women (7.94 ± 3.45 mm; P < 0.001). The mean (SD) osteotomy length was significantly larger for the RC⁺ plane (61.78 ± 6.75 mm) than for the RC plane (68.48 ± 6.65) mm; P < 0.001). All three evaluated parameters had significantly shorter lengths in women than in men.

Conclusion: The safety space for PAO in women was narrower than in men. By shifting the RC plane 10 mm into the posterior direction, the RC⁺ plane provides a safer cutting distance and shorter osteotomy line in the PAO than the RC plan, which is important to avoid intraarticular penetration.

Keywords: New cutting planes; Peracetabular osteotomy; Safety space; Virtual anatomical measurement.