Effects of botulinum toxin A injection on healing and tensile strength of ruptured rabbit Achilles tendons.
BACKGROUND
Tendon lacerations are most commonly managed with surgical repair. Postoperative complications such as adhesions and ruptures often occur with immobilization. Early postoperative mobilization is therefore advised to minimize complications and time required to return to daily life. The aim of this study was to evaluate whether botulinum neurotoxin type-A (BoNT-A) can be used to enhance healing and prevent rupture in mobilized animals with Achilles tenotomy.


METHODS
Twenty-seven rabbits were divided into 3 groups, namely, I, II, and III, after surgical 1-sided Achilles tenotomy and end-to-end repair. The control group for biomechanical comparisons consisted of randomly selected contralateral (unoperated) healthy Achilles tendons. Group I received BoNT-A (4 U/kg) injection into the calf muscles. One week later, electromyographical confirmation was performed to establish the effects of injection. Surgery was then performed. Animals in the second group (n = 9, group II) were immobilized with a cast postoperatively. The third group (n = 9, group III) was mobilized immediately with no cast or BoNT-A. Tendons were harvested and gap formation or ruptures as well as strength of the repaired tendon were assessed 6 weeks after surgery.


RESULTS
Achilles tendons healed in all animals injected with BoNT-A, whereas all were ruptured in group III. All Achilles tendons of animals in groups I and II healed. However, group I repaired tendons were biomechanically equivalent to healthy tendons, whereas group II repaired tendons demonstrated significantly decreased tensile strength (P = 0.009).


CONCLUSIONS
The present study suggests that local injection of BoNT-A can be used for treatment of tendon rupture and may replace the use of cast for immobilization. However, further studies are needed to determine whether BoNT-A injection can have a beneficial effect on the healing of tendon repairs in humans.
From the *Division of Hand Surgery, Department of Orthopaedic Surgery, †Department of Plastic, Reconstructive and Aesthetic Surgery, ‡Department of Pharmacology, and §Department of Neurology, Medical School of Akdeniz University Antalya; and ∥Department of Plastic, Reconstructive and Aesthetic Surgery, Adana Numune Research and Training Hospital, Adana, Turkey.
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D000125:Achilles Tendon / Q000293:injuries* / Q000502:physiology / Q000601:surgery; D000818:Animals; D001696:Biomechanical Phenomena; D019274:Botulinum Toxins, Type A / Q000494:pharmacology / Q000627:therapeutic use*; D003131:Combined Modality Therapy; D008297:Male; D009465:Neuromuscular Agents / Q000494:pharmacology / Q000627:therapeutic use*; D011817:Rabbits; D011897:Random Allocation; D012149:Restraint, Physical; D012421:Rupture / Q000628:therapy; D013708:Tendon Injuries / Q000628:therapy*; D013718:Tensile Strength / Q000187:drug effects; D014945:Wound Healing / Q000187:drug effects
D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A