Assessing the Stability of Talar Defect Repairs: Does Shape Matter?

CATEGORY: Basic Sciences/Biologics; Ankle; Sports INTRODUCTION/PURPOSE: The management of osteochondral lesions of the talus (OLTs) provides a challenging predicament for clinicians; with an increased array of treatment options available. In many cases, the management strategy used is dependent on both the size and location of the lesion. One of the current treatments used for mid-sized (10-20 mm) lesions is Chondro-Gide membrane. To apply this therapy, the defect site is debrided into a shape of the clinicians' preference with a template being used to prepare the Chondro-Gide matrix to the correct size and shape. However, there is some debate within the clinical community as to which shape allows for improved treatment. In this study we aim to assess whether a square or circular scaffold repair provided improved treatment when tested tribologically. METHODS: 16-mm circular chondral defects were introduced to the talar dome of cadaveric donor tissue (n = 3). The tibiotalar joints were cemented with the centre of rotation preserved. The ankle joint was loaded into a ProSim Pendulum Friction simulator and tested using the following loading and motor conditions. Simulations were run at a 1-Hertz for 3600 cycles with a constant tibial load of 640 N and 20° sweep arc through flexion and extension. Data was normalised using a mean frictional offset value calculated using 2 minute pre- and post- test to account for additional frictional torque. Nanofracture was performed on the defect site and a circular Chondro-Gide patch was fixed using a synthetic fibrin glue before testing using the same conditions. The circular defect site was modified to create a 16-mm square defect which was repaired with a square patch in the same manner and tested as described. RESULTS: The overall mean frictional factors over the 1-hour test for the defect, circular and square repairs were 0.039, 0.042 and 0.026, respectively. These values are within the expected range for in vitro testing of two cartilage surfaces previously reported in the literature of 0.003 and 0.08, suggesting that frictional values did not differ between the samples. However, visual changes to the stability of the repair and the reciprocal tibial cartilage could be seen post testing. In all cases the circular repair remained in the defect site. In comparison, for 2 out of 3 of the defects repaired with a square Chondro-Gide patch did not remain stable within the defect site. In both cases further delamination was seen on the reciprocal tibial cartilage tissue. 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.