Tear Completion Versus In Situ Repair for 50% Partial-Thickness Bursal-Side Rotator Cuff Tears: A Biomechanical and Histological Study in an Animal Model

BACKGROUND: Tear completion followed by repair (TCR) and in situ repair (ISR) have been widely used for bursal-side partial-thickness rotator cuff tears (PTRCTs). Both techniques have shown favorable results; however, controversy continues in terms of the best management. PURPOSE: To compare the histological and biomechanical outcomes of these 2 techniques for 50% partial-thickness bursal-side rotator cuff tear repair in a rabbit model. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 27 rabbits were used in this experimental study. Seven rabbits were sacrificed at the beginning of the study to form an intact tendon control group. A chronic 50% partial-thickness bursal-side tear model was created in 20 rabbits, and 5 rabbits were sacrificed for biomechanical testing of chronic partial-thickness tears (control group) without repair. In 15 rabbits, partial-thickness tears were repaired after 8 weeks. Partial-thickness tears in the right shoulders were completed to full thickness and repaired; in contrast, left shoulders were repaired in situ. All rabbits were euthanized 8 weeks after the repair. The tendons were tested biomechanically for ultimate failure, linear stiffness, and displacement. Histological evaluations of tendon-to-bone healing were performed via the modified Watkins score. RESULTS: = .009). CONCLUSION: Both repair techniques are effective for 50% partial-thickness bursal-side rotator cuff tears; however, TCR yields significantly superior biomechanical and histological characteristics compared with ISR. CLINICAL RELEVANCE: Tear completion and repair technique may increase tendon-to-bone healing and thereby reduce re-rupture rate in the partial thickness bursal side rotator cuff tears.