Analysis of mechanical behavior of two parameters, collagen fiber direction and increased concentration of mineral in direct insertion tendon to bone

Tendons and ligaments have a regular hierarchical structure and play a vital role in transferring muscle forces along the tendon length to the skeleton. In this way, tendon is considered as an interface of soft (muscle) and hard (bone) tissue. Such interface causes stress concentration at the osteotendinous junction (insertion site of the tendon to bone) and could cause failure and fracture of the attachment. Collagen fibers are the main load bearing components along the tendon length. While approaching to the insertion site, gradual increase of minerals contribute as the principal strength factor. Hence, the transition of load-bearing from tensile elements (collagen fibers) to tension-compression crystals (minerals) leads to more strength of the insertion site and reduction of the stress concentration. The current study evaluates the role of mineralization and fiber distribution on performance of tendon to bone insertion by simulation of a representative volume element (RVE) in the attachment site. Comparison of models without and with insertion site indicate interesting deviations in stress concentration.