Comparative study of the femoroacetabular impingement (FAI) prevalence in male semiprofessional and amateur soccer players

Femoroacetabular impingement (FAI) represents a novel approach to the mechanical etiology of hip osteoarthritis. The cam-type femoroacetabular impingement deformity occurs frequently in young male athletes. The aim of our study was to evaluate the prevalence of FAI in male semiprofessional soccer players using clinical examination and magnetic resonance imaging (MRI), compared to amateur soccer players. In MRI, the alpha angle of Notzli is determined for quantifying FAI. According to power analysis, a total of 22 asymptomatic semiprofessional soccer players with a median of 23.3 years of age (range 18-30 years) and 22 male amateur soccer players with a median of 22.5 years of age (control group, range 18-29 years) underwent an MRI to measure the hip alpha angle of Notzli. The alpha angle of the kicking legs of the semiprofessional group and the amateur group were analyzed. The study group was moreover evaluated by the Hip Outcome Score (HOS) and a clinical hip examination including range of motion (ROM) and impingement tests. In the semiprofessional group, 19 soccer players had a right kicking leg and 1 soccer player had a left kicking leg. 2 soccer players kicked with two feet. In the semi-professional group, the mean value of the alpha angle of the kicking leg (57.3 +/- A 8.2A degrees) was significantly higher than in the amateur group (51.7 +/- A 4.8A degrees, P = 0.008). In the semi-professional group, 15 (62.5 %) of 24 kicking legs had an increased alpha angle > 55A degrees, while 5 (27.3 %) kicking legs of the amateur group had an alpha angle > 55A degrees. Five semi professional soccer players had findings in clinical examination, whereof 4 had an increased alpha angle > 55A degrees. No participant of the amateur group showed pathological results in the clinical examination (P = 0.0484). Overall, semiprofessional soccer players had a higher proportion of an increased alpha angle than the amateur group. Semiprofessional players have a higher prevalence of an increased alpha angle in the kicking leg than the amateur group at the same age. The kicking leg is predisposed for FAI.