Sex-Based Differences in Femoroacetabular Impingement Syndrome and the Effect of Cam Deformity Location on the Extent of Labral Tearing: A 3-Dimensional Computed Tomography Study

Abstract

Background: Sex-specific quantification of cam morphology in patients with femoroacetabular impingement syndrome may improve diagnostics, surgical planning, and outcomes. Purpose: To (1) examine differences between men and women with symptomatic cam deformities based on deformity location, magnitude, and extent; (2) assess the association between cam deformity and labral pathology; and (3) evaluate the relationship between cam deformity and patient-reported outcome measures after hip arthroscopy. Study Design: Cohort study; Level of evidence, 3. Methods: Computed tomography (CT) scans were acquired in 98 consecutive patients before hip arthroscopy for femoroacetabular impingement syndrome. Custom software was used to generate 3-dimensional bone models and align them to a standard coordinate system. The alpha angle was measured at the 12-, 1-, 2-, and 3-o’clock positions, with 12 and 3 o’clock corresponding to the superior and anterior aspects of the femur, respectively. These alpha angle measurements were used to define the cam midpoint and extent. The labral tear midpoint and extent were evaluated intraoperatively. Bivariate correlation analysis was used to evaluate the association between the cam and labral tear midpoints and between the extent of the cam morphology and labral tearing. Results: The 3-dimensional models were analyzed in a cohort of 69 female and 29 male patients. Male patients were older (mean ± SD, 38.9 ± 12.6 vs 30.7 ± 12.2 years, P = .006) and had a greater body mass index (27.8 ± 4.4 vs 25.3 ± 5.6 kg/m2, P = .005). Male patients had greater alpha angle measures at 12, 1, and 3 o’clock ( P < .05) and a greater maximum alpha angle (69.0° ± 18.8° vs 62.1° ± 21.0°, P = .031); the location of their maximum cam impingement was also significantly different ( P < .05) when compared with female patients. Cam impingement (2:06 ± 1:09 vs 1:33 ± 1:16 clockfaces, P = .032) and labral tearing (3:02 ± 0:35 vs 2:34 ± 0:53 clockfaces, P = .003) in men extended over a greater region of the femoral clockface when compared with women. Significant correlations were demonstrated between the cam and labral tear midpoint locations ( r = 0.190, P = .032) and the extent of the cam deformity and labral tearing ( r = 0.203, P = .024). There were no sex-based differences in patient-reported outcome measures at baseline or 2-year follow-up. Conclusion: Male patients possessed greater cam deformity magnitude and extent when compared with female patients. Cam pathomorphology was associated with the location and extent of labral tearing.