The effect of strain rate on the mechanism of failure of the osteochondral region of immature and mature cartilage on bone in unconstrained shear, loaded through the cartilage layer only, is examined. Strain rate did not affect the fracture mechanism or the fracture load levels in either tissue but only influenced the extent of cartilage deformation before fracture initiation. The exact mechanism of osteochondral failure was found to be the same as observed during impact loading where it depended on skeletal maturity only. Shear fracture of the immature tissue always occurred subchondrally and progressed in a stepwise manner by the propagation of a relatively large crack. By contrast failure in the skeletally failure in the skeletally mature tissue occurred by the advance of a much smaller crack which propagated within the well-defined tidemark region. (A)
Abstract