title: Healing of rotator cuff tendons using botulinum toxin A and immobilization in a rat model.
abstract: 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.
authors.affiliation: Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, 21201, USA. mgilotra@umoa.umm.edu.
authors.forename: Mohit N
authors.initials: MN
authors.lastname: Gilotra
authors.affiliation: Department of Orthopaedics, University of Maryland School of Medicine, Baltimore, MD, 21201, USA.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Shorofsky
authors.affiliation: Department of Orthopaedics and Sports Medicine, MedStar Union Memorial Hospital, Baltimore, MD, 21218, USA.
authors.forename: Jason A
authors.initials: JA
authors.lastname: Stein
authors.affiliation: Department of Orthopaedics and Sports Medicine, MedStar Union Memorial Hospital, Baltimore, MD, 21218, USA.
authors.forename: Anand M
authors.initials: AM
authors.lastname: Murthi
mesh_terms: D065087:Acetylcholine Release Inhibitors / Q000494:pharmacology*; D000818:Animals; D019274:Botulinum Toxins, Type A / Q000494:pharmacology*; D004195:Disease Models, Animal; D008297:Male; D017207:Rats, Sprague-Dawley; D012149:Restraint, Physical; D017006:Rotator Cuff / Q000187:drug effects* / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D013708:Tendon Injuries / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology / Q000628:therapy*; D013997:Time Factors; D014945:Wound Healing / Q000187:drug effects*
chemical_list: D065087:Acetylcholine Release Inhibitors; D019274:Botulinum Toxins, Type A
keywords: Botulinum toxin A (Botox); Cast immobilization; Rat model; Rotator cuff repair; Tendon healing