Prevalence of Femoroacetabular Impingement Features in Japanese Young Adults without Symptoms: Hip Joint Morphology Using Radial Reformation from Computed Tomography

Purpose: To determine the prevalence of femoroacetabular impingement (FAI) morphology in asymptomatic Japanese young adults using multi-detector computed tomography (MDCT) scan. Materials and Methods: A total of 170 subjects (85 men; age, 19–39 years) without hip-related problems were included. Radial slices of 2-mm thickness at 30° intervals were reconstructed perpendicular to the central axis of the femoral head and neck for both hips. Alpha (α) angles, acetabular (AC) depths, and lateral centre-edge (LCE) angles were measured; maximum value of measured α angles was defined as max α angle, and minimum value of measured AC depths was defined as min AC depth. Max α angle > 55° was considered positive for cam-type FAI feature and min AC depth < 0 mm or LCE angle > 40° was considered positive for pincer-type FAI feature. Differences among planes, right-left correlations, and sex differences in FAI abnormalities were assessed. Results: The α angles at 1and 2-o’clock positions in men and at 2-o’clock position in women were significantly greater than those at other positions. AC depths at 2-o’clock position were smallest in men and women. Max α angles and min AC depths and LCE angles showed strong right-left correlations. Max α angles and the numbers of hips with cam features were significantly higher in men than in women. The prevalence of pincer features was similar between men and women. Conclusion: The prevalence of cam type deformity is higher in men. Our results in Japanese populations were similar to those reported previously for Caucasians.