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Development of a Rabbit Chronic-Like Rotator Cuff Injury Model for Study of Fibrosis and Muscular Fatty Degeneration
Published on: March 31, 2023
Healing of rotator cuff tendons using botulinum toxin A and immobilization in a rat model
Mohit N Gilotra1, Michael J Shorofsky2, Jason A Stein3
1Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, 21201, USA. mgilotra@umoa.umm.edu.
Background:
We evaluated effects of botulinum toxin A (Botox) and cast immobilization on tendon healing in a rat model. Injection of Botox into rat supraspinatus was hypothesized to reduce muscle active force and improved healing.
Methods:
Eighty-four supraspinatus tendons were surgically transected and repaired in 42 Sprague-Dawley rats (transosseous technique). After repair, supraspinatus muscle was injected with saline or Botox (3 or 6 U/kg). Half the shoulders were cast-immobilized for the entire postoperative period; half were allowed free cage activity. Histology was examined at 2, 4, 8, and 12 weeks. A healing zone cross-sectional area was measured, and biomechanical testing of repair strength and tendon viscoelastic properties was conducted at 4 and 12 weeks.
Results:
Botox alone and cast immobilization alone exhibited increased ultimate load compared with controls (saline injection, no immobilization) at 4 weeks. No difference in ultimate load occurred between Botox-only and cast-only groups. At 12 weeks, the Botox (6 U/kg) plus cast immobilization group was significantly weakest (p < 0.05). A trend was shown toward decreased healing zone cross-sectional areas in casted groups.
Conclusions:
Supraspinatus Botox injection after rotator cuff repair might help protect the repair. However, cast immobilization plus Botox administration is harmful to rotator cuff healing in a rat tendon model.
