Femoroacetabular Impingement Syndrome Is Associated with Alterations in Foot Mechanics

Background: Femoroacetabular impingement syndrome (FAI) is reportedly associated with abnormalities in hip mechanics. This may be associated with abnormalities in foot mechanics as a consequence of a closed kinematic chain mechanism during the stance, but it has never been investigated in patients with FAI.

Aim: The purpose of this study was to investigate whether FAI syndrome is associated with alterations in foot mechanics.

Methods: Fifteen symptomatic limbs of 15 male patients with cam-type FAI were compared to 30 limbs of 15 normal control males. All subjects had a physical examination, followed by level walking 3-dimensional (3D) gait analysis from foot to hip level.

Results: At heel strike, subtalar joint angle was 3°±3° inversion in the FAI group, and 0°±4° in the normal control group (p=0.01). During the stance, maximum subtalar joint angle was 3°±3° eversion in the FAI group, and 6°±4° eversion in the normal control group (p=0.04). Foot out-toeing angle at heel strike was 16°±8° in the FAI group, and 12°±6° in the normal control group (p=0.05). At the hip level, FAI patients demonstrated a more adducted position compared to control subjects (p=0.01) and a slightly further anterior tilted pelvis (p=0.01).

Discussion and Conclusion: Subtalar inversion at heel strike in patients with FAI syndrome may be a direct consequence of a decrease in hip abduction at that moment. Reduction in subtalar eversion, which is linked to reduction in femur internal rotation, may represent a protective mechanism that these patients acquired in order to eventually alleviate hip symptoms.