Anatomical and Interpositional Bursa Preservation Showed Similar Improved Tendon to Bone Healing Compared With the Bursa Removal in a Rat Rotator Cuff Tear Model

Abstract

To compare the effects of anatomical preservation (AP) and interpositional preservation (IP) of subacromial bursa tissue on tendon-to-bone healing in a rat model of rotator cuff tear. In this study, 48 male Sprague-Dawley rats (average weight 283 g) underwent bilateral supraspinatus tendons severed by sharp incision and repaired immediately. The subacromial bursa tissues were completely removed in 16 rats, who served as the control (CON) group. The other 32 rats were randomly divided into 2 groups AP and IP between tendon and bone. Eight rats of each group were sacrificed for bilateral shoulders at 3 and 9 weeks after the operation, including 5 rats for biomechanical tests and 3 for histologic analysis. No significant differences in terms of biomechanical properties were observed among the groups 3 weeks after surgery. At 9 weeks, the maximum load and stiffness of the AP (32.95 ± 6.33 N, P= .029; 12.49 ± 3.17 N/mm, P < .001; respectively) and IP (33.58 ± 8.47 N, P= .015; 11.63 ± 2.84 N/mm, P= .010, respectively) groups were significantly superior to that of the CON group (26.59 ± 4.47 N; 8.42 ± 2.33 N/mm, respectively). More organized collagen and more mature tendon insertion were observed in AP and IP groups at the interface at 9 weeks, which means better tendon-to-bone healing compared with the CON group. The subacromial bursa plays a positive role in tendon-bone healing. Either anatomical preservation or interpositional preservation between tendon and bone can similarly facilitate the process of healing. Considering the additional surgical time and surgical manipulation, preserving the subacromial bursa at the anatomical position seems to be a better way to promote rotator cuff healing.