The influence of the acetabular labrum on hip joint cartilage consolidation: a poroelastic finite element model

The goal of this study was to investigate the influence of the acetabular l abrum on the consolidation, and hence the solid matrix strains and stresses , of the cartilage layers of the hip joint. A plane-strain finite element m odel was developed, which represented a coronal slice through the acetabula r and femoral cartilage layers and the: acetabular labrum. Elements with po roelastic properties were used to account for the biphasic solid/fluid natu re of the cartilage and labrum. The response of the joint over an extended period of loading (10,000 s) was examined to simulate the nominal compressi ve load that the joint is subjected to throughout the day. The model demons trated that the labrum adds an important resistance in the flow path of the fluid being expressed from the cartilage layers of the joint. Cartilage la yer consolidation was up to 40% quicker in the absence of the labrum. Follo wing removal of the labrum from the model, the solid-on-solid contact stres ses between the femoral and acetabular cartilage layers were greatly increa sed (up to 92% higher), which would increase the friction between the joint surfaces. In the absence of the labrum, the centre of contact shifted towa rds the acetabular rim. Subsurface strains and stresses were much higher wi thout the labrum, which could contribute to fatigue damage of the cartilage layers. Finally, the labrum provided some structural resistance to lateral motion of the femoral head within the acetabulum, enhancing joint stabilit y and preserving joint congruity. (C) 2000 Elsevier Science Ltd. All rights reserved.