The acetabular labrum seal: a poroelastic finite element model

Objective. The aim of the study is to investigate the labrum's ability to s eal a pressurised layer of synovial fluid within the joint, and to study th e influence of this sealing mechanism on cartilage deformation, interstitia l fluid pressure and collagen solid matrix stresses. Background. Cartilage degeneration has been observed in conjunction with la brum pathology. However, little is known about the function of the labrum. Experimental observations have been reported which are consistent with a se aling function of the labrum. Methods. The model was an axisymmetric geometric approximation of the aceta bular and femoral cartilage layers and the surrounding labrum. A poroelasti c formulation was used to account for the solid and fluid components of the se hydrated tissues. A sensitivity analysis of the labrum material properti es was carried out. Results. With a compressive load of 1200 N applied across the joint model, the labrum could seal a layer of pressurised fluid between the femur and ac etabulum, thus preventing contact of the articulating surfaces. With this s ealing effect, loads were transferred across the joint predominantly by uni form pressurisation of the interstitial fluid of the cartilage layers. In t he absence of this sealing, strains within the solid matrix of the cartilag e layers were higher (e.g. 20% vs. 3%). Conclusions. The labrum can seal against fluid expression from the joint sp ace. This sealing function protects the cartilage layers of the hip. Relevance Current treatments for labrum damage and early arthrosis may compromise the sealing function of the labrum. With continued study of the function and i mportance of the labrum, new surgical repair strategies can be developed to maintain the overall function of the hip joint. (C) 2000 Elsevier Science Ltd. All rights reserved.