Biomechanical evaluation contribution of the acetabular labrum to hip stability

Knowledge of the effect of hip pathologies on hip biomechanics is important to the understanding of the development of osteoarthritis, and the contribution of the labrum to hip joint stability has had limited study. The purpose of this study was to evaluate the effect of labral injury to stability of the femoral head in the acetabular socket. Ten cadaver hip specimens were tested using a robotic system under four different loading conditions: axial loading (80 N) along the femoral axis and axial loading (80 N) combined with either anterior, posterior or lateral loading (60 N). The hip states were examined were intact, with a 1.5 cm capsulotomy and with a 1 cm resection of the anterosuperior labrum. At 30A degrees of flexion, under axial load, the displacement of the hip with capsulotomy and labral resection (9.6 +/- 2.5 mm) was significantly larger then the hip with capsulotomy alone (5.6 +/- 4.1 mm, p = 0.005) and the intact hip (5.2 +/- 3.8 mm, p = 0.005). Also, at 30A degrees of flexion, the displacement under combined axial and anterior/posterior load was increased with capsulotomy and labral resection. The acetabular labrum provides stability to the hip joint in response to a distraction force and combined distraction and translation forces. One centimetre of labral resection caused significant displacement ("wobbling" effect) of the femoral head within the acetabulum with normal range of motion. Successful labral repair could be crucial for restoration of the hip biomechanics and prevention of coxarthrosis.