title: Effect of selective sensory denervation on fracture-healing: an experimental study of rats.
abstract: BACKGROUND
  Interactions between the peripheral nervous system and the healing skeleton are poorly understood. Various clinical observations suggest that the nervous system interacts with and promotes fracture-healing. The purpose of this study was to examine the effect of selective sensory denervation on fracture-healing.
  
  
  METHODS
  Fifty-one Sprague-Dawley rats underwent unilateral placement of an intramedullary rod followed by creation of a standardized femoral fracture. One group of these rats underwent sensory denervation by means of a localized capsaicin injection, and the other did not. Subgroups were allocated for analysis of mRNA expression of collagen I and II and osteocalcin at three, seven, and fourteen days after the fracture. Additionally, histological examination was performed at four weeks; micro-computed tomography, at five weeks; and biomechanical testing, at six weeks.
  
  
  RESULTS
  The sensory-denervated group had significantly less collagen-I upregulation than the sensory-intact group at three days after the fracture (difference in means, forty-four-fold [95% confidence interval = 22.7 to 65.5-fold]; p < 0.001) and significantly less collagen-II upregulation at seven days after the fracture (difference in means, ninefold [95% confidence interval = 4.3 to 13.8-fold]; p < 0.001). In the sensory-denervated group, the fracture callus had a significantly larger cross-sectional area (difference in means, 15.6 mm(2) [95% confidence interval = 0.78 to 30.5 mm(2)]; p = 0.043) and was less dense. Biomechanical testing revealed that sensory denervation significantly decreased the load to failure (difference in means, 28.7 N [95% confidence interval = 1.2 to 56.2 N]; p = 0.022).
  
  
  CONCLUSIONS
  Sensory denervation negatively affects fracture-healing. These results offer insight into the nerve-bone interaction following injury.
authors: Department of Orthopaedic Surgery, Wake Forest University School of Medicine, Winston-Salem, NC 27157, USA. papel@wfubmc.edu
authors: Peter J
authors: PJ
authors: Apel
authors: Daniel
authors: D
authors: Crane
authors: Casey N
authors: CN
authors: Northam
authors: Michael
authors: M
authors: Callahan
authors: Thomas L
authors: TL
authors: Smith
authors: Robert D
authors: RD
authors: Teasdall
mesh_terms: D000818:Animals; D003714:Denervation / Q000379:methods; D004195:Disease Models, Animal; D005264:Femoral Fractures / Q000503:physiopathology*; D017102:Fracture Healing / Q000502:physiology*; D008297:Male; D017933:Peripheral Nervous System / Q000187:drug effects / Q000503:physiopathology*; D051381:Rats; D017207:Rats, Sprague-Dawley