Modeling of the rabbit's patello-femoral joint for studies of acute blunt injury to the knee

摘要

Knee injury due to blunt trauma in the automotive setting is currently based solely on a bone fracture criterion. Our studies have shown micro injuries to bone and cartilage for sub-fracture loads (Atkinson and Haut, 1995). Furthermore, Atkinsonand Haut (1995) have shown that by distributing impact loads more uniformly over the knee, the injury risk to these tissues is reduced. This suggests a need for a stress-based knee injury criterion. We have developed contact and non-contact computationalmodels of the patella-femoral joint to predict stress distributions during blunt impact and to correlate these stresses to injury. We have developed a 2-D, non-contact, plane strain, elastic model of the rabbit patella-femoral joint (Newberry et al.,in-press). Using this model, we have determined "safe" maximum shear stresses on the retro-patellar surface and cartilage-bone interface. Another study has shown that the critical value for developing lesions at the surface is a shear stress of 5.5 MPa(Atkinson et al.. 1998). However, we have some inconsistencies with this model. First, the maximum shear stress in the retro-patellar cartilage is at the interface with bone, not at the surface where fissures are observed. Secondly, we have not been ableto incorporate the elastic modulus derived from indentation tests, because the deformations of the cartilage become excessively large under pressures generated during impact.