Thank you for the opportunity to present at this meeting and thank you for showing interest in this audio poster. My name is Mark Farn, and I'm a specialist lower limb orthopaedic surgeon working in the UK and along with colleagues from the University of Leeds. I've been working on assessing the stability of tailored dome defect repairs and trying to answer the question about whether shape matters. So, in terms of treating osteochondral defects, we've been looking at the use of nanofracture and the application of a chondroguide bilayer membrane to the surface of the defect. This treatment strategy is frequently used for small to mid-sized lesions up to 20 millimetres in diameter, and some clinicians have a preference in terms of the shape of the debrided area that they use to create a stable surface for repair. We therefore set out to try and identify whether a circular or square shape is more stable for mid-sized lesions. So, in terms of the testing methodology, we had access to three matched cadaveric tibial and tailor specimens. We identified the centre of rotation of these and cemented them into a custom rig. The aim being then to run pendulum friction simulation tests to try and mimic normal walking over a one hour period with 3,600 cycles at 1 hertz and loading of 640 newtons to simulate body weight with a 20 degree flexion extension arc. The jig you can see on the right hand side of the slide and each paired set of specimens was tested three times. Firstly, with the defect alone, subsequently with a circular repair using a chondroguide matrix and fibrin glue following nanofracture. And then the circular defect was debrided to a square defect and repaired again using chondroguide and fibrin glue. So, each set was run three times. The friction within the system was tested using piezoelectric sensors and load was applied in a standard manner to all. Cartilage surfaces were subsequently examined before and after testing for macroscopic change. So, in terms of the ex vivo testing results, what we found was that, generally speaking, circular repairs were more stable and less subject to displacement. Square repairs tended to displace during the study period, though all of the conditions demonstrated similar frictional characteristics and were comparable to other cartilage to cartilage contact studies within the literature. So, the main findings and limitations of this study were that a circular repair was more stable than the square defect in this study and would suggest that this is due to an edge effect that allows the repair to be lifted during simulated ankle motion and that this enabled displacement of the graft material. Friction was similar across all of the tested conditions but was lowest in the square defect, which corresponded to displacement of the repair. We used a fairly simplified gait model in this study without rotation and further analysis including rotational movements of the joint may be useful in evaluating stability further, though we were able to demonstrate that shape did affect stability and that circular constructs were optimal. Thank you for listening. This project was completed as part of a supported PhD research project and was supported by joint operations who provided the materials used within the study subject to appropriate consents.

Mark Farn

lower limb orthopaedic surgeon

University of Leeds

tailored dome defect repairs

osteochondral defects