Does the tidemark location matter in osteochondral allograft transplantation? A finite element analysis

Abstract

<h2>ABSTRACT</h2><h3>OBECTIVE</h3> The purpose of this study is to evaluate the impact that osteochondral allograft cartilage thickness has on contact pressures, and to simulate whether a mismatch of the subchondral bony interface relative to the host-recipient site results in altered biomechanics. <h3>METHODS</h3> Properties of articular cartilage and bone were incorporated into a finite element model to create a simulated osteochondral lesion (diameter: 10mm, height: 10mm, cartilage thickness: 2mm, subchondral bone thickness: 8mm). Five osteochondral plugs were constructed to fill the defect, with cartilage-to-bone ratios between 1:9 and 1:1. The plugs were inserted and given a static downward force of 5000N. Resultant stresses and displacements were measured. <h3>RESULTS</h3> The 2:8 cartilage-to-bone ratio plug, matched with the recipient site, was deemed optimal based on its resultant stress and displacement. The 1:9 plug displaced less than the 2:8 match and endured greater stress per unit of cartilage volume, whereas the 3:7 plug also displayed similar displacement to the 1:9 plug but had greater cartilage volume and was able to distribute less stress per unit of cartilage volume. The 4:6 plug displaced to a similar extent as the 3:7 plug but displayed a unique pattern of strain. The 5:5 plug was considered non-functional, as the majority of displacement was seen in the cartilage of the recipient site rather than in the plug itself. <h3>CONCLUSION</h3> The relationship between the cartilage-to-bone ratio in osteochondral allografts and that of their surroundings significantly impacts the distribution of stresses and predilection for micro-motion at the repair site.