Biomechanical and Functional Indicators in Male Semiprofessional Soccer Players With Increased Hip Alpha Angles vs. Amateur Soccer Players

Matthias Lahner; Christoph von Schulze Pellengahr; Philipp Alexander Walter; Carsten Lukas; Andreas Falarzik; Kiriakos Daniilidis; Lars Victor von Engelhardt; Christoph Abraham; Ewald M Hennig; Marco Hagen


BMC Musculoskelet Disord. 2014;15(88) 

In This Article


Femoroacetabular impingement (FAI) is a morphological hip disorder which shows a novel approximation to mechanical etiology of hip osteoarthritis.[1,2] A large share of idiopathic hip arthritis can be attributed to FAI, which is why early diagnosis is very important.[3,4] In the pathogenesis of FAI, there are two anatomical deformities either at the acetabulum or the proximal end of the femur or in both structures. A femoral type (cam impingement) is anatomically differentiated from the acetabular type of FAI (pincer impingement).[5] The cam impingement is caused from a prominence at the anterolateral femoral head-neck junction.[6] The alpha angle of Nötzli is described to quantify the asphericity of the femoral head in axial oblique sequences of magnetic resonance images (MRI). Causes for the cam impingement are aspheric deformity of the femoral head, slipped capital femoral epiphysis, late closure of the femoral epiphysis and Legg-Calve-Perthes disease.[7–9] The pincer impingement is caused by an immoderate acetabular cover of the head of femur and is linked with acetabular retroversion, protrusio acetabuli or coxa profunda.[10,11] Symptomatic FAI can be treated by arthroscopic procedures or open surgery.[12]

FAI is assumed to be predominant in young male athletes with sport activities with high impact for the hip joints like soccer.[13] Agricola et al. demonstrated that FAI was more prevalent in 89 elite soccer players than in 92 nonathletic controls.[14] Cam-type deformity develops during adolescence and is probably to be affected by high-impact sports practice.[14] The soccer game is primarily characterized by running-related actions.[15] Therefore, the shock attenuation capacity of soccer players with FAI during running is of special biomechanical interest.

Clinically, FAI must be differentiated from insertional tendinopathy of the adductor muscles. The tendinopathy of the adductor can be associated with arthropathy of the symphysis and insertional pubic area.[16] The major clinical symptoms of the tendinopathy of the adductor muscles are groin or lower abdomen pain.[16]

Only few biomechanical studies exist on the gait analyses in patients with FAI.[17–20] In these studies, symptomatic patients were compared to healthy control probands. However, to our best knowledge, this is the first study which analyzed a strongly selective risk group like male semiprofessional soccer players who are disproportionately affected by FAI, but usually do not show clinical symptoms, yet.

Therefore, the aim of our biomechanical study was to compare the foot rollover process during running between male semiprofessional soccer players with increased alpha angles and age-matched amateur soccer players. It was postulated that an increased alpha angle would lead to different rearfoot motion, tibial acceleration and plantar pressure parameters.