The creation and repair of osteochondral defects and the effect on the opposing surfaces

The repair of articular cartilage defects is a topic that has received significant focus from both basic science and clinical perspectives. The current gold standard treatment for significantly damaged or degenerated articular cartilage in the knee is a total joint replacement, although there are several drawbacks including reduced range of motion and increased instability. Whilst the total knee replacement will continue to be a valuable treatment, there is a need to find alternatives and part of the solution is having an appropriate animal model to effectively evaluate said alternative treatments.The first part of this dissertation describes the characterization of an ovine osteochondral defect model which ultimately could be used to validate the efficacy of a variety of osteochondral implants. The effect of this femoral defect on the tibial surface, including the meniscus, was also studied and a metallic resurfacing device (HemiCAP) evaluated for its efficacy in protecting the knee from further degenerative changes. Additionally, pressure footprint and contact stresses were measured with flexible pressure sensors at flexion angles and loads determined from the sheep gaitcycle. This study found that the HemiCAP device increased peak pressure when compared to all other conditions tested, especially at a point corresponding to heel strike. Since loading is known to modulate bone remodelling, micro computed tomography was used to measure changes in the subchondral and cancellous bone on the tibia opposing the surgical site. Biologically, there were no significant differences detected in the knees treated with the HemiCAP device when compared with those that had untreated osteochondral defects, which suggests that the HemiCAP device is not effective in protecting against tibial degeneration, but at least it does no more harm than not treating the defect in the first place