The material properties of the bovine acetabular labrum

The compressive and tensile material properties of the bovine acetabular labrum were measured. Confined compression testing was used to determine the aggregate compressive modulus and the permeability of the labrum. The compressive modulus of the labrum (0.157 +/- 0.057 MPa) is comparable to that of the morphologically similar meniscus, and approximately one-quarter to one-half that of the adjoining acetabular cartilage. The permeability of the labrum (4.98 +/- 3.43 x 10(-16) m4/N s) was lower than that of the meniscus and cartilage. With a significantly higher resistance to interstitial fluid flow across the acetabular rim than along the rim. Specimens from the posterior and superior regions of the labrum were tested to failure in uniaxial tension. The maximum stress at failure (11.9 +/- 6.1 MPa), maximum strain at failure (26.5 +/- 7.6%) and tangent modulus (74.7 +/- 44.3 MPa) were similar to those reported for the bovine meniscus, and to other tissues composed of highly oriented collagen fiber bundles. In tension, the labrum is much stiffer (10-15 x) than the adjoining articular cartilage, and the posterior region of the labrum is significantly stiffer (45%) than the superior region. The labrum's low permeability may contribute to sealing of the hip joint. The high circumferential tensile stiffness of the labrum, together with its ring structure, reinforce the acetabular rim and may contribute to joint stability.