Ilio-femoral ligament strains during the flexion-abduction-external rotation test : a cadaveric study

Background: Flexion-abduction-external-rotation (FABER) test is one of the most used tests during the clinical assessment of the hip joint. The limited range of motions reached could be due to iliofemoral ligament tightness, but no study has assessed capsular ligament strain during this test. The main objective of this study is to report strains within the iliofemoral ligament during the FABER test using a segmental approach. Methods: 9 hips were harvested, and all muscles were removed. Hemispherical markers ( 2.6 mm) were glued on the lateral and medial borders of both the medial and lateral iliofemoral bands, separating each border into proximal, mid, and distal portions. The lower limb was placed in a FABER test position. A laser scanner allowed to digitize the 3D surface of the capsule. A Kruskal-Wallis test was performed to assess the effect of ligaments, borders, and portions. Findings: The lateral band of the iliofemoral ligament showed greater strains (14.6 11.4 %) compared to the medial band (-8.7 ± 14.2 %) (p < 0.001). The greatest strains were observed in the distal portion of the lateral border of the lateral band (51.1 21.5 %). A decrease in strain was observed in the mid-portion of the medial border of the medial iliofemoral ligament (-27.9 8.9 %). Interpretation: The FABER test is used to assess pain at the hip. Our results show that the limited range of motion at the hip during this test might be caused by increased strains in the lateral band. These results demonstrate that a limitation of joint range of motion during the FABER could be due to an excessive tension of the lateral band of the iliofemoral ligament