DIFFERENTIAL MECHANICS AND HEALING OUTCOMES OF SMALL AND LARGE PARTIAL-WIDTH DEFECTS IN THE RAT ROTATOR CUFF ATTACHMENT
Sullivan, Anna Lia
University of Delaware
Partial-width tears of the rotator cuff are a common occurrence in the clinic, contributing to pain and restricted function of the shoulder. There are limited studies that focus on how these tears heal and mechanically function in vivo. This aim of this study was to understand how varying sizes of partial-width crescent-shaped tears heal in vivo. A rat model was used to assess structural and mechanical outcomes of small and large partial-width defects of the infraspinatus tendon attachment, one of four tendon attachments of the rotator cuff. A surgical defect model was used to generate the tear using biopsy punches and animals were allowed to heal for 3- and 8-week timepoints. We evaluated healing using gross dissection, micro-computed tomography (microCT), histology, and biomechanical outcomes of acute (0-week) and chronic (8-week) healed defects. We found that large defects had increased fibrosis, neovascularization, rounded nuclei, tendon disorganization, and collagen fiber disorganization compared to small defects. The duration of healing, but not defect size, significantly influenced cellularity, bone quality, and mechanical properties. In this study, we showed that increasing the size of crescent-shaped tears negatively impacted the structural healing of the attachment but did not find tear size to influence mechanical function by 8-weeks of healing. This was the first study to compare healing of two different sized partial-width full-thickness rotator cuff defects in vivo.
animal science, rat rotator cuff, partial width defects