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



The demographic data is presented in Table 1. There was no statistically significant difference concerning the mean age of both groups. There was no statistically significance difference in height, weight and body-mass index. 7 (50%) subjects of the semiprofessional group and 5 (35.7%) subjects of the amateur group clinically showed a varus malalignement of the mechanical axis. In both groups, no one had a history of hip dysplasia or disease in the childhood. In the soccer group, the mean value of the alpha angle was 55.16 ± 6.58° (Figure 1). The mean value of the alpha angle was lower in the amateur group, but there was no significant difference in the amateur group (51.65 ± 4.43°, Table 2, Figure 2). Concerning the inter-rater reliability, the values ranged from 0.87 to 0.99 (Table 3).

Figure 1.

Axial MRI scan of the right hip of a participant of the soccer group. The alpha angle is formed by the connecting lines (yellow lines) between the longitudinal mid-axis of the femoral neck and the axis which marked the point first exceeded the radius of the cartilage-covered femoral head. The alpha angle was 76.8° in this example.

Figure 2.

Axial MRI sequence of a participant of the amateur group. The alpha angle of the right hip was 48.3°.

Biomechanical Measurements

The results (mean values and standard deviations) of the ground reaction forces, peak tibial acceleration, rearfoot motion and plantar pressure parameters are presented in Table 4 and Table 5. In both shoe conditions, we found similar statistically significant differences between the groups. Increases in median power frequency (NW: +7%, p < 0.05, VW: +8%, p < 0.05) and the rate of the vertical ground reaction force (NW: +39%, p < 0.01, VW: +56%, p < 0.05) reveal higher loading of the lower extremities and shock transmission to the upper body in the semiprofessional subjects.

The reduced shock absorption for the semiprofessional subjects is also demonstrated by an increased peak tibial acceleration (NW: +32%, p < 0.05, VW: +56%, p < 0.01) when compared to the amateur soccer players. Maximum rearfoot motion is about 22% lower in the semiprofessional soccer players compared to the amateur group in both shoe conditions. In the second part of the stance phase, peak vertical force is increased (NW/VW: +8%, p < 0.05) while the horizontal impulse is reduced (NW: -10%, p < 0.05; VW: -7%, p = 0.08) in the semiprofessional subjects. Additionally, we found increased peak plantar pressures under the lateral midfoot (NW: + 30%, p < 0.05, VW: +15%, p < 0.05) and the third metatarsal head (NW: + 30%, p < 0.05, VW: +36%) in the semiprofessional group for running at the same speed (3.3 m/s).