Comparison of early bone union between anterior and posterior approach in periacetabular osteotomy: spherical periacetabular osteotomy and rotational acetabular osteotomy

Spherical Periacetabular Osteotomy (SPO) is a novel procedure using an osteotomy line similar to that for Rotational Acetabular Osteotomy (RAO). The major difference between these procedures is that an anterior approach is used for SPO and an anterior and posterior approach for RAO. This study compared early bone union between these procedures. We enrolled 12 patients (12 hips) post-RAO and 15 patients (15 hips) post-SPO who consented to undergo computed tomography (CT) imaging about 5 weeks after surgery. Results showed no significant differences in lateral centre-edge angle or acetabular roof obliquity between these groups, both before and after surgery. Partial bone union was observed in 7 of 12 cases (58.3%) in the RAO group and 14 of 15 cases (93.3%) in the SPO group, with the SPO group showing a significantly higher incidence of bone union (<i>P</i> = .03). X-ray images taken simultaneously with CT scans did not reveal any bone union in either group. Functional outcomes measured by the Japanese Orthopaedic Association score revealed no significant differences between groups at 6 months and 1 year postoperatively. Both procedures preserved the quadrilateral surface, avoided cutting the pubic bone, and achieved good stability of the pelvic ring as well as wide contact area on the cut bone. Through CT imaging, this study highlighted the potential of SPO to achieve superior early bone union, likely due to its preservation of blood flow and minimally invasive approach. This study suggests the potential utility of CT imaging in evaluating early bone union after osteotomy.