Abstract
Introduction Prior work has found that impingement in patients with femoroacetabular impingement syndrome (FAIS) may occur at hip flexion angles >90 degrees, however, this is still debated. Kissing lesions are lesions of cartilage wear on the femoral head/neck junction that may provide insights into what degree of flexion impingement occurs. Our purpose was to determine the angle of hip flexion at which kissing lesions in patients with FAIS engage the labrum under direct arthroscopic visualization to provide insights on the impingement angle. Methods Primary hip arthroscopy patients with intraoperatively identified kissing lesions were included. Patients were flexed at the hip with the lower extremity in neutral rotation until the labrum engaged the femoral neck kissing lesion. Lateral photographs were taken at this position and degree of hip flexion was calculated using an online goniometer. Comparisons between kissing lesion flexion angle and patient demographics were assessed via two-tailed t-tests and one-way ANOVA. Regression analysis was performed to evaluate the relationship between kissing lesion flexion angle and various radiographic measurements, while controlling for age, sex, and body mass index (BMI). Results A total of 108 patients were analyzed in this study. Mean age was 31.0 ± 10.8 years, mean BMI was 26.4 ± 5.8 kg/m2, and 73 (68%) were females. Mean angle of hip flexion required to achieve kissing lesion contact was 63.3 ± 11.5 degrees with a range from 39.8 to 94.9 degrees across all patients. Males engaged at higher flexion angles (66.5 ± 10.9 degrees) compared to females (61.8 ± 11.6, p=0.045). Regression analysis demonstrated inverse relationship between kissing lesion flexion angle and alpha angle on frog leg lateral (β=-0.291, 95% CI [-0.428 to -0.254], p=<0.001) and anteroposterior (AP) radiographs (β=-0.395, 95% CI [-0.571 to -0.219], p=<0.001). Conclusions These findings demonstrate hip impingement in those with FAI may routinely occur at hip flexion angles below 90 degrees and that kissing lesions inversely correlate with alpha angles on radiographs.