Tensile properties of the human acetabular labrum-the first report.

The tensile properties of the human acetabular labrum were investigated using a uniaxial tension testing apparatus. The superior quadrant of the acetabular labrum was harvested from patients who underwent hip surgery. The obtained labra were sliced and shaped into rectangles for measuring uniaxial tension. We hypothesized that several characteristics such as gender, age, degeneration due to primary ailment, and the severity of the acetabular dysplasia would influence the tensile properties of the labrum. Antero-posterior radiographs of the pelvis have been used to evaluate the severity of the acetabular dysplasia and to diagnose the developmental dysplasia of the hip joint (DDH) clinically. Thus, we investigated the correlation between each of two representative radiological measurements-the CE angle and the Sharp angle-and tensile properties to assess the influence of the severity of the acetabular dysplasia. The tensile stress-strain curves for the labrum assumed a sigmoid shape. The mean tensile stress at failure for all specimens was 8.8+/-4.1 MPa. The mean strain at failure for all specimens was 48.5+/-10.4%. The mean tensile modulus was 66.4+/-42.2 MPa. Mean tensile stress at failure for specimens from males was greater than that of specimens from females. A significant difference was found in the maximum stress at failure among the three diagnosis-based groups: the other group withstood the highest stress before failure, whereas the osteoarthritis (OA) group withstood the lowest. No significant correlations with age or radiological characteristics were found for tensile stress, strain at failure, or tensile modulus. Our results suggest that labra obtained from male patients have stronger tensile stress than those from female patients, and that degenerative changes may influence the properties of the acetabular labrum.