Association of Cam Deformity on Anteroposterior Pelvic Radiographs and More Severe Chondral Damage in Femoroacetabular Impingement Syndrome

Abstract

Background: Abnormal proximal femoral morphology in femoroacetabular impingement syndrome (FAIS) identifiable on the anteroposterior (AP) pelvic radiograph has been described as the “pistol grip” deformity. The effect of a superior cam deformity identified on this radiographic view remains unknown. Purposes: To assess the relationship between AP cam deformity (AP alpha angle [AP AA] >55°) and cartilage injury; to assess the relationship between AP cam deformity and labral injury; and to determine if patient factors are correlated with cartilage and labral injury. Study Design: Case-control study; Level of evidence, 3. Methods: Patients undergoing osteochondroplasty and labral repair for FAIS with a single surgeon were identified retrospectively. Intraoperative size, location, and severity of cartilage and labral damage were prospectively collected. Chondrolabral and femoral/acetabular cartilage damage were graded with the Beck labral and cartilage injury criteria. Radiographic data included the AP AA, lateral center-edge angle (LCEA), and maximum femoral alpha angle (MF AA). Patients with hip dysplasia (LCEA <18°; LCEA 18°-25° with acetabular index >10°) were excluded. Outcomes were compared across cartilage and labral severity grades. We report odds ratios (ORs) with 95% confidence intervals and P values from multivariable logistic regressions. Results: Of the 158 included hips (154 patients), 69% were female and the mean (± standard deviation [SD]) age was 30.3 ± 9.7 years. Increase in age, increase in body mass index (BMI), and male sex were associated with increasing severity of cartilage and labral injury. More severe cartilage damage was associated with increasing AP AA ( P < .001) and MF AA ( P < .001). The odds of developing a higher category of cartilage injury severity (grade ≥3) were 119% higher (OR, 2.19 [95% CI, 1.36-3.64]; P = .002) for every SD increase (16.7°) in AP AA, adjusting for age, sex, and BMI. The odds of developing a severe labral injury (grade ≥3) were 118% higher (OR, 2.18 [95% CI 1.17-4.32]; P = .018) for every SD increase (10.5°) in MF AA, adjusting for age, sex, BMI, and AP AA. Conclusion: Increasing age and BMI, and male sex are associated with increasing severity of cartilage and labral injury in FAIS. The odds of developing a cartilage injury are significantly higher with independent increases in AP AA and MF AA.