Effect of osteochondral graft orientation in a biotribological test system

Autologous osteochondral transplantation (AOT) utilizing autografts is a widely used technique for the treatment of small‐to‐medium cartilage defects occurring in knee and ankle joints. The application of viable cartilage and bone ensures proper integration, early weight bearing, as well as restoration of biomechanical and biotribological properties. However, alignment of the autografts onto the defect site remains a pivotal aspect of reinstating the properties of the joint toward successful autograft integration. This is the first study to perform tests with different orientations of osteochondral grafts in a cartilage‐on‐cartilage test system. The objective was to estimate if there are differences between aligned and 90°‐rotated grafts concerning molecular biological and biomechanical parameters. Tissue viability, assessed by XTT assay indicated lower metabolic activity in tested osteochondral grafts (aligned, p = 0.0148 and 90°‐rotated, p = 0.0760) in favor of a higher anabolic gene expression (aligned, p = 0.0030 and 90°‐rotated, 0.0027). Tissue structure was evaluated by Safranin O histology and microscopic images of the surface. Aligned and 90°‐rotated grafts revealed no apparent differences between proteoglycan content or cracks and fissures on the cartilage surface. Test medium analyzed after tribological tests for their sulfated glycosaminoglycan content revealed no differences (p = 0.3282). During the tests, both the friction coefficient and the relative displacement between the two cartilage surfaces were measured, with no significant difference in both parameters (COF, p = 0.2232 and relative displacement, p = 0.3185). From the methods we deployed, this study can infer that there are no differences between aligned and 90°‐rotated osteochondral grafts after tribological tests in the used ex vivo tissue model. © 2019 The Authors. Journal of Orthopaedic Research® Published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res