Femoral and acetabular anteversion have been recognized as contributing factors to hip pain among patients with femoro-acetabular impingement (FAI). However, to what extend version abnormalities contribute to chondrolabral damage is unclear. Some suggest that combined low version is associated with better cartilage health and less synovitis. However, low femoral version reduces range of motion, leading to impingement with less flexion. This study aimed to assess differences in the location and type of labral tears in hips with different rotational morphology amongst patients treated with hip arthroscopy. This is a prospective consecutive cohort study of 314 hips who underwent hip arthroscopy at a tertiary referral center (age 34±10 years-old, 57% females) for FAI (78%), labral tear (17%) or dysplasia (5%). Patients underwent a computed tomography (CT) scan to measure acetabular and femoral version (using Reikeras technique; normal: 5°–20°). Alpha-angle was calculated and impingement index was calculated as the alpha-angle minus femoral version. Presence, type and location of labral tears was assessed intra-operatively using an acetabular clockface system. There was no difference in central (p=0.4) or cranial (p=0.8) acetabular version between different locations of a labral tear. Femoral version was the highest among patients with a labral tear in zone 3 (12°±10°), compared to those with a labral tear in zone 2 (6±9°; p=0.002), or zone 4 (8±8°; p=0.08). Patients with combined cam and low femoral version were more likely to have a labral tear in zone 2 (51%) than zone 3 (28%) (p=0.009). Mean impingement index was 42±16. Patients with an intact labrum had a lower impingement index than those with a frayed (p=0.009), torn (p=0.048) and ossified labrum (p=0.019). Based on ROC analysis, impingement index >36 was associated with presence of a labral tear (sensitivity 64%, specificity 86%) (AUC 0.86±0.08; p < 0 .001). Femoral version has an influence on the presence and location of labral tears. Low femoral version contributes to anterior impingement in patients with FAI. Combination of low femoral version and presence of CAM morphology may reduce likelilood of labral pathology. Calculating the impingement index may help to consent patients prior to hip arthroscopy.
Verhaegen et al. (Wed,) studied this question.