Posterior femoroacetabular impact in patients with suspected anterior femoroacetabular impingement evaluated with a 3-Dimensional dynamic study

Abstract Background Recently, posterior femoroacetabular impact (PFAI) is considered as a cause of hip pain. The purpose of this study was to estimate the frequency of PFAI in patients with suspected symptomatic Anterior femoroacetabular impingement (AFAI) through 3D dynamic study Methods We performed a retrospective observational study of patients with suspected of symptomatic AFAI evaluated by computed tomography (CT) from February 2015 to December 2017. PFAI was identified through a 3-dimensional (3D) dynamic study with Clinical Graphics software (Move ForwardTM, Zimmer Biomet, Inc. Miami, USA). Acetabular anteversion, femoral anteversion, neck-shaft angle, lateral central-edge (LCE) angle, alpha angle and range-of-motion were collected. Results The study included 181 hips in 131 patients with a median age of 48 (Interquartile range-IQR: 38-59) years; 61.1% (80) were women. PFAI was found in 18.8% (34/181) of hips [95% confidence interval: 13.8%-25.1%]. Among hips with PFAI, 15 had AFAI. External rotation (PFAI: 40; IQR:40-45, AFAI: 45; IQR: 40-60) and neck-shaft angel were lower in the PFAI group (PFAI: 128.4±4.3, AFAI: 133.7±5.4). Conclusion The impact between the acetabulum and femoral neck on the posterior-superior zone is a frequent finding in patients with symptomatic AFAI through a 3D dynamic study.