title: Chemical denervation with botulinum neurotoxin a improves the surgical manipulation of the muscle-tendon unit: an experimental study in an animal model.
abstract: OBJECTIVE
  The chemical denervation that results from botulinum neurotoxin A (BoNT-A) causes a temporary, reversible paresis that can result in easier surgical manipulation of the muscle-tendon unit in the context of tendon rupture and repair. The purpose of the study was to determine whether BoNT-A injections can be used to temporarily and reversibly modulate active and passive skeletal muscle properties.
  
  
  METHODS
  Male CD1 mice weighing 40-50 g were divided into a 1-week postinjection group (n = 13: n = 5 saline and n = 8 BoNT-A) and a 2-week postinjection group (n = 17: n = 7 saline and n = 10 BoNT-A). The animals had in vivo muscle force testing and in vivo biomechanical evaluation.
  
  
  RESULTS
  There was a substantial decline in the maximal single twitch amplitude (p < .05) and tetanic amplitude (p < .05) at one week and at 2 weeks after BoNT-A injection, when compared to saline-injected controls. BoNT-A injection significantly reduced the peak passive properties of the muscle-tendon unit as a function of displacement at one week (p < .05). Specifically, the stiffness of the BoNT-A injected muscle-tendon unit was 0.417 N/mm compared to the control saline injected group, which was 0.634 N/mm, a 35% reduction in stiffness (p < .05).
  
  
  CONCLUSIONS
  Presurgical treatment with BoNT-A might improve the surgical manipulation of the muscle-tendon unit, thus improving surgical outcomes. The results implicate neural tone as a substantial contributor to the passive repair tension of the muscle-tendon unit. The modulation of neural tone through temporary, reversible paresis is a novel approach that might improve intraoperative and postoperative passive muscle properties, allowing for progressive rehabilitation while protecting the surgical repair site.
authors.affiliation: Department of Orthopaedic Surgery, Wake Forest University School of Medicine, Winston-Salem, NC 27157-1070, USA. smannava@wfubmc.edu
authors.forename: Sandeep
authors.initials: S
authors.lastname: Mannava
authors.forename: Michael F
authors.initials: MF
authors.lastname: Callahan
authors.forename: Simon M
authors.initials: SM
authors.lastname: Trach
authors.forename: Walter F
authors.initials: WF
authors.lastname: Wiggins
authors.forename: Beth P
authors.initials: BP
authors.lastname: Smith
authors.forename: L Andrew
authors.initials: LA
authors.lastname: Koman
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Smith
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Tuohy
mesh_terms: D000818:Animals; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage*; D004195:Disease Models, Animal; D007273:Injections, Intramuscular; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009121:Muscle Denervation / Q000379:methods*; D053580:Muscle Strength / Q000187:drug effects; D018482:Muscle, Skeletal / Q000601:surgery; D019637:Orthopedic Procedures / Q000379:methods; D011300:Preoperative Care / Q000379:methods; D011336:Probability; D011897:Random Allocation; D012016:Reference Values; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D013710:Tendons / Q000601:surgery
chemical_list: D019274:Botulinum Toxins, Type A