Biceps tendon properties worsen initially but improve over time following rotator cuff tears in a rat model

Damage to the biceps tendon is often seen in conjunction with rotator cuff tears. However, controversy exists regarding its role in the shoulder and its optimal treatment. A previous study determined that biceps tendons were detrimentally affected in the presence of rotator cuff tears in the rat model and this damage worsened over time. However, whether this damage progresses at later time points to provide a chronic model is unknown. The objective of this study was to determine the changes in the biceps tendon in the presence of a cuff tear over time. Our hypothesis was that histological, compositional, organizational, and mechanical properties would worsen with time. We detached the supraspinatus and infraspinatus tendons of 48 rats and evaluated these properties at 1, 4, 8, and 16 weeks postdetachment. Properties worsened through 8 weeks, but improved between 8 and 16 weeks. We therefore conclude that biceps tendon changes in this model are not truly chronic. Additionally, it has been shown that infraspinatus properties in this model return to normal by 16 weeks, when biceps properties improve, indicating that earlier repair of one or more of the rotator cuff tendons may lead to resolved pathology of the long head of the biceps tendon.