Developing a novel methodology to investigate the biomechanics and wear in natural patello-femoral joints

Patello-femoral problems affect nearly a quarter of the population and remain a common cause of knee replacement revision surgery. Minimally invasive treatments such as osteochondral substitutions are early interventions that can be used to prevent or delay the need for these replacements. Lack of pre-clinical testing is a major challenge in getting these promising treatments to clinical trials. The purpose of this research was to develop a platform that can get these products one step closer to clinical trials and hence getting them out in the market as a viable product for treating osteochondral lesions. The aim of this project was to develop and validate a design specification for the pre-clinical testing of natural patello-femoral joint (PFJ). A characterization study was carried out to investigate the suitable animal model required to simulate a human joint that requires osteochondral substitutions. The size of the porcine PFJ was closer to the human PFJ and the material properties of its cartilage were also similar to the human cartilage. Therefore, the porcine PFJ was chosen as the animal model to develop the methodologies for this project. A methodology was developed to investigate wear of the natural porcine PFJ by adapting a single station knee simulator to apply the porcine PFJ gait cycle to the joints. The position of the patella with respect to the femur determined through a contact point study was used to set up the samples in the simulator. A positive (cobalt chrome on natural cartilage) and negative (cartilage on cartilage) control was used to investigate the wear. This study showed the potential of using an Alicona Infinite focus G5 optical profiler to assess the change in cartilage topography in natural joints. The contact area and pressure in the PFJ was measured using Tekscan pressure sensors. This study showed the change in contact mechanics across a gait cycle and the effect of sample geometry on the contact mechanics of a joint. In-vitro simulation can reduce the need for animal testing and progress the preclinical trials for new tissue substitutions. Developing the methodology in a human knee is not practical. However, by establishing an animal model can bring this a step closer. The methods developed in this thesis can contribute towards creating a pre-clinical testing system that can be used to assess early interventions to the PFJ.