Abstract:
The myotendinous junction (MTJ) is a critical site for force transmission between muscle fibers and tendons, and it is frequently identified as a common location for muscle strain injuries. Despite its clinical importance, the micro-scale mechanical environment and local strain distributions within the MTJ are not fully understood, largely due to the experimental challenges of measuring these phenomena in vivo. This study addresses this knowledge gap by presenting a novel finite element micromechanical model of the MTJ, developed to systematically examine how its intricate structure and mechanical properties influence the local micro-scale strains experienced by individual muscle fibers.
The biomechanical model was rigorously constructed to represent the complex interplay between muscle fibers and the surrounding connective tissues, particularly the endomysium. It accounts for both the passive and active mechanical properties of these components, reflecting their unique stress-strain behaviors. A crucial aspect of the model's development involved its validation through direct comparisons with histological longitudinal sections of muscles fixed in both slack and stretched positions. The model's predictions of A-band deformations within the muscle fibers near the MTJ showed strong agreement with those measured from the histological images, thereby confirming its biofidelity and predictive accuracy.
The results from this micromechanical biomechanics model reveal significant insights into the localized strain distributions within the MTJ. The model accurately predicts the deformations of sarcomeres and muscle fibers at the interface with the tendon, identifying areas of high strain concentration that are likely susceptible to injury. This detailed understanding of the mechanical environment at the MTJ provides a powerful tool for investigating muscle injury mechanisms, developing more effective prevention strategies, and improving rehabilitation protocols. This work underscores the essential role of computational biomechanics in elucidating complex tissue-level mechanics that are otherwise inaccessible through experimental means.
