Betamethasone injection at different stages showing different effect on tendon-to-bone healing in a rat rotator cuff tear model.

Abstract

Corticosteroid injection (CSI) has been used to relieve shoulder pain postoperatively, although its adverse effect on tendon-to-bone healing has been proved. However, whether there is any difference in the adverse effect caused by CSI at different stages on rotator cuff healing is still unknown. This study aimed to evaluate the effect of subacromial betamethasone injection on tendon-to-bone healing at different time points in a rat rotator cuff tear model. A total of 42 rats were divided into 3 groups equally. In the experimental groups, betamethasone was injected into the subacromial space intraoperatively and 7 days after surgical repair respectively. In the control group, the torn tendon was repaired in the same way with saline injection. All animals were killed for biomechanical testing and histologic evaluation 2 or 6 weeks after operation. The postoperative injection group showed significantly inferior maximum load (10.97 ± 2.23 vs. 15.36 ± 4.07 N, P = .009, and 20.95 ± 3.39 vs. 28.98 ± 4.50 N, respectively; P = .005) and stiffness (8.10 ± 2.69 vs. 12.27 ± 3.53 N/mm, P = .010, and 5.07 ± 2.38 N/mm vs. 10.88 ± 2.37 N/mm, P = .001) at 2 and 6 weeks compared with that of the control group. Worse histologic formation of the bone-tendon interface was observed in the experimental groups compared with the control group, especially in the postoperative injection group. This study found that postoperative corticosteroid administration at the recovery stage could harm the rotator cuff healing biomechanically and histologically in a rat rotator cuff tear model. However, the intraoperative CSI did not show any significant adverse effect. These findings support the consideration of intraoperative CSI as a potentially safer therapeutic option in clinical practice.