Development of a Method to Assess the Tribological Effect of Osteochondral Defects Within the Talocrural Joint

CATEGORY: Basic Sciences/Biologics; Ankle; Ankle Arthritis INTRODUCTION/PURPOSE: Osteochondral lesions of the talus commonly occur because of traumatic injury. These lesions can affect the biomechanical behaviour of the ankle joint resulting in further degradation of the tissue and development of osteoarthritis. However, little is known about the impact of such lesions to the biomechanical behaviour of the natural ankle joint, in particular changes to the tribology of the joint due to their introduction. The aim of this study was to develop a tribological simulation of the natural tibiotalar joint to assess frictional changes due to the introduction of chondral lesion and to further assess the impact of current treatment modalities such as AMIC techniques (Nanofracture with Chondro-Gide membrane) and osteochondral allograft cores (OCA). METHODS: A healthy left cadaveric tibiotalar joint (n =1) was cemented into a custom-made jig; to preserve centre of rotation (COR). The sample was loaded into a ProSim Pendulum Friction simulator and tested using the following loading conditions. Simulations were run at 1-Hertz frequency for 3600 cycles with a constant load of 640 N applied through the tibia through a +- 10° flexion and extension (F/E) angle. Data was normalised using a mean frictional offset value calculated through a 2-minute pre- and post-test to account for additional frictional torque and changes to friction factor was assessed. Cartilage was assessed for changes in tissue appearance and damage. Following this, a 10-mm circular, chondral defect was introduced to talar dome and testing was repeated under the same conditions. The defect was repaired with a 10-mm Chondro-Gide patch and then 10-mm OCA before being subsequently tested using the same methods. RESULTS: No visible changes were seen to the cartilage during testing for the healthy, defected and Chondro-Gide treated conditions. Some damage could be seen on the reciprocal tibial cartilage after testing with the OCA repair. Assessment of normalised friction factors showed that while testing, for each condition, the frictional output remained stable with a reduction in the mean friction factor seen due to the introduction of a defect. This was maintained with Chondro-Gide. A return to normal was seen in the OCA treatment with the overall mean values for the healthy and OCA repair were 0.0301 and 0.0329, respectively. In addition, overall mean frictional factor values in the presence of a defect and Chondro-Gide repair showed reduced frictional values of 0.0119 and 0.0103, respectively. CONCLUSION: This method will allow for potential preclinical evaluation of treatments for OLTs in an appropriately simulated environment to assess tribological changes. The values obtained for the frictional factor all sit within the expected range for friction between two cartilage surfaces that has been reported in the literature 0.003 and 0.08. Thus, providing a reliable platform for comparing different methods of osteochondral defect repair in the tibiotalar joint.