title: Controlled induction of a pseudarthrosis: a study using a rodent model.
abstract: OBJECTIVE
  This study aimed to test the hypothesis that under standardized mechanical and biologic conditions, the process of indirect bone repair in a rodent species could be manipulated to form a reproducible, atrophic, fibrous pseudarthrosis.
  
  
  METHODS
  The model used comprised a mid-diaphyseal, transverse osteotomy in the rat femur, stabilized via a precision miniature external fixator, a constant axial fixation stiffness being defined by a specific frame geometry.
  
  
  METHODS
  The repair process for both 0.5-mm and 3.0-mm gap osteotomies was characterized using radiography, dual-energy x-ray absorptiometry, histologic assessment of standardized longitudinal sections, and postmortem mechanical testing.
  
  
  RESULTS
  Healing of the defect was highly reproducible, bone union being attained at around 5 weeks postoperatively with a 0.5-mm gap. Increasing the gap width to 3.0 mm resulted consistently in a pseudarthrosis.
  
  
  CONCLUSIONS
  These two reproducible patterns of repair can now be used to elucidate the underlying molecular mechanisms controlling the extent and progression of connective tissue differentiation in indirect bone repair without the additional variable of a nonstandardized mechanical environment.
authors.affiliation: Department of Anatomy, University of Bristol, Bristol, UK.
authors.forename: Luise J
authors.initials: LJ
authors.lastname: Harrison
authors.forename: James L
authors.initials: JL
authors.lastname: Cunningham
authors.forename: Lennart
authors.initials: L
authors.lastname: Strömberg
authors.forename: Allen E
authors.initials: AE
authors.lastname: Goodship
mesh_terms: D015502:Absorptiometry, Photon; D000818:Animals; D005269:Femur; D017102:Fracture Healing; D008297:Male; D008954:Models, Biological; D010027:Osteotomy; D011542:Pseudarthrosis / Q000000981:diagnostic imaging / Q000473:pathology*; D051381:Rats; D017208:Rats, Wistar