57Botox Weakens Muscle Repair in Chronic Rotator Cuff Injury
This animal study evaluated the effects of intramuscular botulinum toxin (Botox) on the repair strength of chronic rotator cuff injuries in rabbits. Twelve weeks after supraspinatus tendon transection, one shoulder was injected with Botox and the contralateral side with saline before repair. Six weeks post-repair, the Botox-treated group had significantly lower repair strength (2.64 N) compared to controls (5.51 N, p = 0.03), and a higher rate of partial healing defects (80% vs. 40%). All samples showed Goutallier Grade 3 or 4 fatty infiltration, which was more pronounced with Botox. Contrary to the initial hypothesis, Botox compromised healing and may increase muscle degeneration in chronic injuries.