The material properties of the bovine acetabular labrum

The compressive and tensile material properties of the bovine acetabular la brum were measured. Confined compression testing was used to determine the aggregate compressive Modulus and the permeability of the labrum. The compr essive 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 l abrum (4.98 +/- 3.43 x 10 (16) m(4)/N s) was lower than that of the meniscu s and cartilage,,vith a significantly higher resistance to interstitial flu id flow across the acetabular rim than along the rim. Specimens from the po sterior and superior regions or the labrum were tested to failure in uniaxi al tension. The maximum stress at failure (11.9 +/- 6.1 MPa). maximum strai n at failure (26.5 +/- 7.6%) and tangent modulus (74.7 +/- 44.3 MPa) were s imilar to those reported for the bovine meniscus, and to other tissues comp osed of highly oriented collagen fiber bundles. In tension, the labrum is m uch stiffer (10-15x) than the adjoining articular cartilage, and the poster ior region of the labrum is significantly stiffer (45%) than the superior r egion. The labrum's low permeability may contribute to sealing of the hip j oint. The high circumferential tensile stiffness of the labrum, together wi th its ring structure, reinforce the acetabular rim and may contribute to j oint stability. (C) 2001 Orthopaedic Research Society. Published by Elsevie r Science Ltd. All rights reserved.