title: Characterization of the healing process in non-stabilized and stabilized femur fractures in mice.
abstract: BACKGROUND
  Although a variety of suitable fracture models for mice exist, in many studies bone healing was still analyzed without fracture stabilization. Because there is little information whether the healing of non-stabilized fractures differs from that of stabilized fractures, we herein studied the healing process of non-stabilized compared to stabilized femur fractures.
  
  
  METHODS
  Twenty-one CD-1 mice were stabilized after midshaft fracture of the femur with an intramedullary screw allowing micromovements and endochondral healing. In another 22 mice the femur fractures were left unstabilized. Bone healing was studied by radiological, biomechanical, histomorphometric and protein expression analyses.
  
  
  RESULTS
  Non-stabilized femur fractures revealed a significantly lower biomechanical stiffness compared to stabilized fractures. During the early phase of fracture healing non-stabilized fractures demonstrated a significantly lower amount of osseous tissue and a higher amount of cartilage tissue. During the late phase of fracture healing both non-stabilized and stabilized fractures showed almost 100 % osseous callus tissue. However, in stabilized fractures remodeling was almost completed with lamellar bone while non-stabilized fractures still showed large callus with great amounts of woven bone, indicating a delay in bone remodeling. Of interest, western blot analyses of callus tissue demonstrated in non-stabilized fractures a significantly reduced expression of vascular endothelial growth factor and a slightly lowered expression of bone morphogenetic protein-2 and collagen-10.
  
  
  CONCLUSIONS
  Non-stabilized femur fractures in mice show a marked delay in bone healing compared to stabilized fractures. Therefore, non-stabilized fracture models may not be used to analyze the mechanisms of normal bone healing.
authors.affiliation: Department of Trauma, Hand and Reconstructive Surgery, Saarland University, 66421, Homburg/Saar, Germany. tina.histing@uks.eu.
authors.forename: T
authors.initials: T
authors.lastname: Histing
authors.affiliation: Department of Trauma, Hand and Reconstructive Surgery, Saarland University, 66421, Homburg/Saar, Germany.
authors.forename: K
authors.initials: K
authors.lastname: Heerschop
authors.affiliation: Department of Trauma, Hand and Reconstructive Surgery, Saarland University, 66421, Homburg/Saar, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Klein
authors.affiliation: Institute for Clinical and Experimental Surgery, Saarland University, 66421, Homburg/Saar, Germany.
authors.forename: C
authors.initials: C
authors.lastname: Scheuer
authors.affiliation: Department of Trauma, Hand and Reconstructive Surgery, Saarland University, 66421, Homburg/Saar, Germany.
authors.forename: D
authors.initials: D
authors.lastname: Stenger
authors.affiliation: Department of Trauma, Hand and Reconstructive Surgery, Saarland University, 66421, Homburg/Saar, Germany.
authors.forename: J H
authors.initials: JH
authors.lastname: Holstein
authors.affiliation: Department of Trauma, Hand and Reconstructive Surgery, Saarland University, 66421, Homburg/Saar, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Pohlemann
authors.affiliation: Institute for Clinical and Experimental Surgery, Saarland University, 66421, Homburg/Saar, Germany.
authors.forename: M D
authors.initials: MD
authors.lastname: Menger
mesh_terms: D000818:Animals; D055396:Bone Morphogenetic Protein 2 / Q000378:metabolism; D016723:Bone Remodeling / Q000502:physiology; D001863:Bone Screws; D002146:Bony Callus / Q000378:metabolism; D003094:Collagen / Q000378:metabolism; D005260:Female; D005264:Femoral Fractures / Q000601:surgery*; D005269:Femur / Q000378:metabolism; D005593:Fracture Fixation, Internal; D017102:Fracture Healing / Q000502:physiology*; D051379:Mice; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D055396:Bone Morphogenetic Protein 2; D042461:Vascular Endothelial Growth Factor A; D003094:Collagen
keywords: Bone remodeling; Fracture; Mice; Non-stabilization; Stabilization