title: Increased exercise after stable closed fracture fixation does not affect fracture healing in mice.
abstract: OBJECTIVE
  The aim of the present study was to evaluate the systemic biological effect of increased exercise on bone repair after stable fracture fixation.
  
  
  METHODS
  Two groups of SKH-1h mice were studied. Animals of the first group (n=36) were housed in cages supplied with a running wheel, while mice of the second group (n=37) were housed in standard cages for control. Using a closed femur fracture model, bone repair was analysed by histomorphometry and biomechanical testing at 2 and 5 weeks. At 2 weeks, we additionally evaluated the expression of the proliferation marker PCNA (proliferating cell nuclear antigen) and the angiogenic and osteogenic growth factor VEGF (vascular endothelial growth factor). To standardise the mechanical conditions in the fracture gap, we used an intramedullary compression screw for stable fracture fixation.
  
  
  RESULTS
  Each mouse of the exercise group run a mean total distance of 23.5 km after 2 weeks and 104.3 km after 5 weeks. Histomorphometric analysis of the size and tissue composition of the callus could not reveal significant differences between mice undergoing exercise and controls. Accordingly, biomechanical testing showed a comparable torsional stiffness, peak rotation angle, and load at failure of the healing bones in the two groups. The expression of PCNA and VEGF did also not differ between mice of the exercise group and controls.
  
  
  CONCLUSIONS
  We conclude that increased exercise does not affect bone repair after stable fracture fixation.
authors.affiliation: Department of Trauma, Hand & Reconstructive Surgery, University of Saarland, D-66421 Homburg/Saar, Germany. joerg.holstein@uks.eu
authors.forename: J H
authors.initials: JH
authors.lastname: Holstein
authors.forename: S C
authors.initials: SC
authors.lastname: Becker
authors.forename: M
authors.initials: M
authors.lastname: Fiedler
authors.forename: C
authors.initials: C
authors.lastname: Scheuer
authors.forename: P
authors.initials: P
authors.lastname: Garcia
authors.forename: T
authors.initials: T
authors.lastname: Histing
authors.forename: M
authors.initials: M
authors.lastname: Klein
authors.forename: M D
authors.initials: MD
authors.lastname: Menger
authors.forename: T
authors.initials: T
authors.lastname: Pohlemann
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D001863:Bone Screws; D002146:Bony Callus / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology; D004195:Disease Models, Animal; D005264:Femoral Fractures / Q000000981:diagnostic imaging / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D005594:Fracture Fixation, Intramedullary; D017102:Fracture Healing / Q000502:physiology*; D051379:Mice; D005082:Physical Exertion / Q000502:physiology*; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D011859:Radiography; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D018809:Proliferating Cell Nuclear Antigen; D042461:Vascular Endothelial Growth Factor A; C467480:vascular endothelial growth factor A, mouse