RESUMO
OBJECTIVE: To quantify the radial and lateral extents of femoral cam lesions in FAI patients relative to the alpha angle and correlate with clinical data. METHODS: Retrospective study of 81 hips with femoral cam morphology that underwent arthroscopic surgery between 2017 and 2019. At each hour over the clockface, the alpha angle (α) (abnormal defined as > 55°), radial extent, and lateral extent of cam lesions were measured on CT. These measurements were correlated with clinical and arthroscopic data. Statistics included independent samples t-test and chi-squared test with Bonferroni correction and multivariate logistic regression. RESULTS: Larger α at 12:00-4:00 in males vs females (56.6-63.4° vs 44.3-58.5°, P < 0.001) and at 2:00-4:00 with elite sports participation vs without (56.7-70.9° vs 49.6-61.1°, P ≤ 0.004). Independent risk factors for radial extent beyond 12:00-3:00 were: male sex (OR 4.82, 95% CI [1.46, 15.85], P = 0.010), BMI > 25 (OR 4.74, 95% CI [1.61, 14.00], P = 0.005), and elite sports participation (OR 3.28, 95% CI [1.09, 9.82], P = 0.034). Lateral extent increased at 1:00-4:00 in males vs females (7.8-18.6 mm vs 1.6-9.1 mm, P < 0.0001). A 16% prevalence of distal cam lesions was found at locations with normal α, resulting in underestimation of radial extent by an average of 1.7 hours. CONCLUSION: There is a positive correlation between the alpha angle, lateral extent, and radial extent of cam lesions. FAI patients who were male, participated in elite level sports, and had a BMI > 25 had larger cam lesions. A larger alpha angle is a risk factor for cartilage damage. Patients may have distal cam lesions at locations with normal alpha angles, though their significance is unknown.
