Mechanisms of bimaterial attachment at the interface of tendon to bone

The material mismatch at the attachment of tendon to bone is among the most severe for any tensile connection in nature. Attaching dissimilar materials is a major challenge in engineering, and has proven to be a challenge in surgical practice as well. Here, we examine the material attachment schemes employed at this connection through the lens of solid mechanics. We identify four strategies that the body adopts to achieve effective load transfer between tendon and bone: (1) a shallow attachment angle at the insertion of transitional tissue and bone, (2) shaping of gross tissue morphology of the transitional tissue, (3) interdigitation of bone with the transitional tissue, and (4) functional grading of transitional tissue between tendon and bone. We provide solutions to model problems that highlight the first two mechanisms: discuss the third qualitatively in the context of engineering practice and provide a review of our earlier work on the fourth. We study these strategies both in terms of ways that biomimetic attachment might benefit engineering practice and of ways that engineering experience might serve to improve surgical healing outcomes.