Diagnostic Utility of CT-Based Acetabular Sector Angles in Pincer-Type Femoroacetabular Impingement: Limitations and Clinical Integration

Background: Pincer-type femoroacetabular impingement (FAI) results from acetabular overcoverage. While computed tomography (CT) with multiplanar reformation (MPR) enables precise measurement of acetabular sector angles (ASAs), the diagnostic utility and limitations of these measurements remain unclear. Purpose: To evaluate the diagnostic accuracy of ASA measurements in pincer-type FAI and determine whether these measurements can serve as stand-alone diagnostic criteria or should be integrated with other clinical parameters. Study Design: Cross-sectional study. Methods: The authors evaluated 104 hips in 52 patients with surgically confirmed pincer-type FAI and 31 asymptomatic controls. ASAs were measured at 4 levels using CT with MPR correction for pelvic tilt. Receiver operating characteristic (ROC) analysis determined diagnostic cutoff values. Results: Intermediate anterior ASA (IAASA) showed the most significant difference between FAI and controls (88.7°± 21.4° vs 67.8°± 13.6°; P < .001; d = 1.11). However, ROC analysis revealed only moderate diagnostic accuracy (area under the curve, 0.79). An IAASA cutoff of 97° provided 88% specificity but only 40% sensitivity. Conclusion: IAASA is significantly elevated in pincer-type FAI but has only moderate diagnostic accuracy due to substantial population variation. ASA measurements should be integrated with clinical findings, traditional radiographic parameters, and surgical findings rather than used as stand-alone diagnostic criteria.