Timing matters: NSAIDs interfere with the late proliferation stage of a repaired rotator cuff tendon healing in rats

Introduction: Rotator cuff (RC) tear is a common problem that causes pain and can limit shoulder function. Non-steroidal anti-inflammatory drugs (NSAIDs) are often prescribed for musculoskeletal pain, including the pain subsequent to RC repair. NSAIDs have been reported to affect bone metabolism and fracture healing' but there is little evidence about their effect on tendon healing. We investigated the effect of meloxicam (non-steroidal anti-inflammatory drug) on the healing of RC tendons when given immediately after surgical repair. Materials and methods: Thirty-nine rats underwent acute RC tear and repair. Group A (n = 13) received daily intraperitoneal (IP) injections of meloxicam for the first 10 postoperative days. Group B (n = 13) received IP injections of meloxicam starting from postoperative day 11. Group C (n = 13, controls) received daily IP injections of saline for 3 weeks. The animals were killed 3 weeks after surgery and the RC was evaluated by gross inspection, biomechanical testing and histological examination. Results: Group B displayed a significantly lower mean maximal load at 3 weeks than group C (P = 0.02) and group A (P = 0.05). Stiffness was significantly lower in B group as compared to A group (P = 0.05). Qualitative examination of histology specimens did not disclose any apparent differences with respect to cellularity, vascularity, healing, and collagen orientation. Conclusions: We conclude that meloxicam decreases the biomechanical strength of repaired rat RCs when administered between 11 and 20 days after the repair.