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. 2022 May 13;10(5):23259671221095174.
doi: 10.1177/23259671221095174. eCollection 2022 May.

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

Thomas D Alter  1 , Derrick M Knapik  2 , Floor Lambers  1 , Martina Guidetti  1 , Jorge Chahla  1 , Philip Malloy  1 , Shane J Nho  1
Affiliations

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

Thomas D Alter et al. Orthop J Sports Med. .

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.

Keywords: computed tomography; femoroacetabular impingement syndrome; hip arthroscopy; sex differences.

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Conflict of interest statement

One or more of the authors has declared the following potential conflict of interest or source of funding: D.M.K. has received research support from Arthrex and education payments from Medwest and Smith & Nephew. F.L. is an employee of Stryker. J.C. has received education payments from Arthrex and Smith & Nephew; consulting fees from Arthrex, DePuy, Linvatec, and Smith & Nephew; speaking fees from Linvatec; and hospitality payments from Stryker. S.J.N. has received education payments from Elite Orthopedics and consulting fees and royalties from Stryker. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto.

Figures

Figure 1.
Figure 1.
(A) Alpha angle measurement at 12, 1, 2, and 3 o’clock based on the 3-dimensional model. (B) Line A: line from center of sphere to femoral neck midpoint. Line B: line from center of best-fit sphere to location at which the femoral head loses sphericity. Line C: line from center of sphere to the location at which the femoral head-neck junction exceeds the best-fit sphere by 1 mm, accounting for resolution error. The angle between lines A and C is the 3-dimensonal–based measure of the alpha angle for this study.
Figure 2.
Figure 2.
Mean alpha angle measurement on computed tomography based on 3-dimensional–reconstructed hip models according to femoral clockface.
Figure 3.
Figure 3.
Mean midpoint and extent of cam deformity and labral tear in male and female patients.
See this image and copyright information in PMC

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