Preoperative cam-type deformity does not compromise long-term outcomes after transposition osteotomy of the acetabulum for hip dysplasia: A propensity score-matched study.

Abstract

Cam-type deformity may contribute to femoroacetabular impingement after acetabular reorientation for hip dysplasia; however, its clinical relevance after transposition osteotomy of the acetabulum (TOA) remains unclear. This study aimed to determine whether cam-type deformity affects clinical, radiographic, and patient-reported outcomes after TOA in patients with hip dysplasia. We retrospectively reviewed 607 patients (607 hips) who underwent TOA for symptomatic hip dysplasia between 1998 and 2019. Seventy-nine hips with cam-type deformity, defined as an alpha angle ≥55° on preoperative frog-leg lateral radiographs, were propensity score-matched 1:2 to hips without cam-type deformity using age, sex, body mass index, preoperative modified Harris Hip Score (mHHS), preoperative Tönnis grade, and preoperative lateral center-edge angle. The matched cohort comprised 76 hips with and 152 hips without cam-type deformity. Failure was defined as progression to Tönnis grade 3 osteoarthritis or conversion to total hip arthroplasty. The latest mHHS was comparable between hips with and without cam-type deformity (92 vs. 96; p = 0.427) at a median follow-up of 11 and 10 years, respectively (p = 0.589). Osteoarthritis progression occurred in 8 hips (11%) and 20 hips (13%), respectively (p = 0.671), and failure occurred in 5 hips (6.6%) and 12 hips (7.9%), respectively (p = 0.796). The 10- and 20-year joint survival rates were 98% and 73% in both groups (log-rank p = 0.701). Pain, satisfaction, Forgotten Joint Score-12, and all Hip disability and Osteoarthritis Outcome Score subscales were comparable between the groups. Preoperative cam-type deformity was not associated with inferior long-term outcomes after TOA for hip dysplasia. These findings suggest that an alpha angle ≥55° alone may not be sufficient to justify routine femoral osteochondroplasty during TOA; however, future studies should identify cam morphologies associated with clinically relevant residual impingement after acetabular reorientation.