Biceps Tendon Changes Along Its Length, and With Altered Loading, in the Presence of Rotator Cuff Tears in a Rat Model

Biceps tendon pathology is commonly seen in the presence of rotator cuff tears and is often identified as a source of shoulder pain. However, the contribution of the biceps tendon to shoulder function is controversial and therefore the etiology of this pathology and its optimal treatment are unknown. Degeneration, inflammation and altered loading have all been hypothesized as possible mechanisms for biceps tendon pathologies. A previous study began to investigate the contribution of altered loading to these pathologies and showed that 4 weeks of increased loading resulted in decreased mechanical properties along the entire length of the tendon while decreased loading resulted in increased stiffness at the insertion site but decreased properties elsewhere [1]. Building on this study, the objective of the present study was to determine the effects of a longer period of altered loading along the length of the biceps tendon in order to determine where biceps tendon pathology originates following rotator cuff tears in a rat model. We hypothesized that: 1) increased loading would result in decreased mechanical and histological properties and decreased loading would result in increased mechanical properties and organization and 2) modulus and organization would increase along the length of the biceps tendon.