Thank you for giving me the opportunity to present this material and thank you for showing interest in this presentation. My name is Mark Farndon. I'm a specialist orthopaedic lower limb surgeon from the UK and along with colleagues from Leeds University, we've been developing a method to assess the tribological effects of osteochondral defects within the ankle joint. So we know that osteoarthritis can be a progressive problem characterised by degeneration of cartilage on the joint surface and some early interventions show poor longer term success rates. There are a variety of different treatments available but little is known about the stability of repairs and how they affect the frictional properties within the joint. As such, our aim was to develop a tribological simulation of the natural tibiotalar joint to try and assess the frictional changes due to the introduction of a chondral defect and subsequent repair. So using matched cadaveric tibiotalar specimens, we were able to develop a methodology to assess the diameter of the talus and identify the centre of rotation. The tibia was then aligned in a custom jig based upon the centre of the rotation and the height adjusted so that the optimal level for COR within the simulator was fixed after cementation. Subsequently, the tibial set was used to align the talus based on the natural alignment of the joint and this was also cemented into custom fixtures. You can see the pendulum friction simulator in the slides here demonstrating the fact that after generation of a chondral defect and subsequent repair using either chondragyde and disylfibrin glue or indeed an osteochondral allograft core, the specimen was then cycled at 3600 intervals at 1 hertz using a 640 newton loading capacity to mimic natural gait with a 20 degree flexion and extension arc in a buffered plasma situation. Ex vivo testing, there were no significant visible changes on the talar articular cartilage though we were able to observe reciprocal damage on the tibia. This was particularly noticeable in the context of the osteochondral allograft and although every method was used to ensure that this was absolutely flush, there is the possibility that the core being proud could have contributed to these problems. Reduction of friction factors could be due to the presence of the defect which allowed for increased deformation of the cartilage on the talar dome and the mean frictional characteristics are shown in the bottom left. If we graph these findings out, then the osteochondral allograft behaved most similarly to the healthy tissue and the chondragyde bilayer behaved similarly to the tissue with defect. For the main limitations, subsequent findings and impacts of the study, the testing method was sensitive enough to be able to assess changes in friction factor as a result of changes in the introduction of a simulated defect. A reduction was seen after the introduction of a chondral lesion and this value was maintained with repair using a chondragyde bilayer membrane. The methodology provides a platform to assess the stability of different types of chondral repairs within the tibia-talar joint moving forward. The only main limitation particularly is that the model only contains a tibia and talus. There was no fibula in this situation and no ligamentous tissue. Thank you for listening and showing interest.

Mark Farndon

orthopaedic lower limb surgeon

tribological effects

osteochondral defects

ankle joint