Combination of Anterior Acetabular Coverage and Femoral Head Shape Predicts Femoroacetabular Impingement After Periacetabular Osteotomy.

Abstract Background Femoroacetabular impingement (FAI) after periacetabular osteotomy (PAO) may be affected by both anterior acetabular coverage and femoral head shape. This study aimed to radiographically evaluate the relationship of the combination of acetabular coverage and femoral head shape with the occurrence of FAI after curved PAO. Methods In this study, 76 hip joints from patients with symptomatic developmental dysplasia of the hip underwent curved PAO. The relationship between the combined postoperative anterior center-edge (CE) and alpha angles (i.e., the combination angle) and the occurrence of postoperative FAI was evaluated. Clinical factors and the pre- and postoperative three-dimensional CE angles, acetabular versions, femoral versions, radiographic alpha angles of the femoral head, and the combination angle were measured and compared to clinical outcomes. Results The modified Harris Hip Scores (mHHS), University of California, Los Angeles (UCLA) activity scores, and acetabular coverage angles were significantly improved following curved PAO. ROC curve analysis demonstrated the combination angle over 108° may be a predictive factor for the occurrence of FAI after curved PAO. Multivariate analysis demonstrated that an age Conclusion A combination angle >108° may be a predictive factor for the occurrence of FAI after curved PAO and impaired clinical outcomes. To avoid postoperative FAI, we propose that osteochondroplasty of the femoral head should be performed for patients with preoperative combination angles >90°.