Tensile properties of the human acetabular labrum—the first report

Abstract

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.

Tensile Strain in the Anterior Part of the Acetabular Labrum During Provocative Maneuvering of the Normal Hip

“…Previous reports of the material properties of the labrum have been based on explanted specimens dissected free of the acetabular margin and loaded uniaxially. Two such studies demonstrated that the average maximum strain at failure was 26.5% in bovine tissue 2 and 48.5% in humans 11 . Although the highest maximum strain value in the present study was lower than the ultimate strains reported in previous studies, this finding indicates that the maneuvers that were simulated in our testing protocol do not strain the labrum near failure.…”

“…Additionally, for visualization of the area surrounding and between markers, a two-dimensional strain color map was created with use of commercial computer-aided design and finite element software (Unigraphics NX 4.0 and Nastran 4.0; EDS, Plano, Texas). The material properties of the labrum used in the finite element analysis (mean tensile modulus, 66.4 ± 42.2 MPa; maximum tensile strain, 45.5%) were derived from the previous work by Ishiko et al 11 .…”

“…Previous analyses of the labrum include finite element models 2-5 and isolated tissue studies 11 , but the biomechanics of the intact labrum have not yet been described. Ferguson et al used finite element models [2][3][4][5] to describe the material properties of the bovine labrum and the potential influence of the labrum on joint function, whereas Ishiko et al 11 described the mechanical properties of the labrum when isolated from the hip joint. An initial clue toward the pathological process causing labral lesions may lie in the previous demonstration of a predominance of lesions in the anterior portion of the labrum and the ensuing suggestion that this area of the labrum may be subject to increased mechanical demands or may be intrinsically weaker 1 .…”

Clinical relevance of the hip joint: Part I – Review of the anatomy of the hip joint

“…27,28 Regarding differences in the tensile strength of the hip joint between genders, those of the male can take higher tensile stress, when compared with those of females. 29 Thus, males may have more stability of the hip joint. However, the relationship between the strength of the labrum and morbidity of the hip disease is not clear.…”

Testing and modelling of soft connective tissues of joints: A review

“…It is common practice to freeze the test samples at 220 uC and to allow them to thaw at room temperature overnight prior to testing [4][5][6][7][8][9][10][11][12]; this has been shown not to affect the creep behaviour of intervertebral discs [13] or the structural properties of the medial collateral ligament [14]. Cryopreservation to 280 uC has also been used [15][16][17]. Giannini et al [18] harvested five pairs of human posterior tibial tendons and, for each pair, they tensile tested one tendon fresh and the other after fresh-freezing it to 280 uC for 30 days.…”