The effects of extracorporeal shock waves on carrageenan-induced Achilles tendinitis in rats: a biomechanical and histological analysis.

Objective: The aim of this study was to investigate the influence of low-dose extracorporeal shock waves (ESW) on the healing potential of Achilles tendinitis in the rat.

Methods: The 36 adult Sprague-Dawley rats used in this study were randomly divided into four groups. Group A (n=10) were injected with carrageenan, Group B (n=10) were injected with carrageenan and received ESW, Group C (n=10) received ESW only, and Group D (n=6) was a sham group. Rats were injected with 10 microliters of 3% carrageenan or a saline solution eight times during a one-week period with a subcutaneous needle. One week following the final injection, ESW was applied at a rate of 500 impulses in 5 minutes at 2 bars (comparative to 0.09 mJ/mm²) to rats in Groups B and C. Rats were sacrificed three weeks later. Tensile strength, inflammation, and vascularity and collagen density were measured.

Results: Failure of the tendon ultimate loads was significantly lower in the study groups than in the control group (p<0.05). Collagen fiber density was higher in the control group than in the other groups (p=0.59). No other histological differences were found.

Conclusion: Low-dose ESW has a negative effect on tendon tensile strength in this animal model.