Morphology of Acetabulum and Femoral Head-Neck Junction in Hip Dysplasia Which Underwent Rotational Acetabular Osteotomy

The purpose of this study was to evaluate the preoperative radiographs with cases of developmental dysplasia of the hip (DDH) leading to rotational acetabular osteotomy (RAO) or curved peri-acetabular osteotomy (CPO), and examine the frequency of femoroacetabular impingement (FAI) related bone morphology in the acetabulum and femoral head-neck junction. Twenty-four hips with hip dyaplasia who underwent CPO or RAO were included in this study. Six hips had grade 0 and eighteen hips had grade 1 OA according to the Tönnis classification. We excluded patients with moderate and severe hip osteoarthritis and major femoral head deformities. Preoperative radiograph was evaluated on sharp angle, center-edge angle, alpha angle, crossover sign and posterior wall sign. Crossover signs were revealed in 7 hips (29.2%); posterior wall signs were revealed in 16 hips (66.7%); and cam-type deformities with an alpha angle of ≥50.5 ̊ were observed in 19 hips (79.2%) in preoperative evaluation. As determined using the Tönnis scale, no progression of osteoarthritis was found in 16 of the 24 hips; there was a one-grade progression in 8 hips. Among the 8 hips, either positive cross-over sign or posterior sign in acetabulum, and an alpha angle of ≥50.5 ̊ in femur were observed in six hips with progression of osteoarthritis. The presence of cam-type deformity and acetabular retroversion in patients who underwent RAO or CPO was relatively high in preoperative radiographs, and caution should be employed during surgery in patients with DDH. There is a possibility of secondary FAI due to excessive forward coverage of the bone fragments after RAO and CPO.