title: Does the sheep mandible relapse following lengthening by distraction osteogenesis?
abstract: OBJECTIVE
  Distraction osteogenesis is a technique used to lengthen the shortened mandible. However, the long term stability of the distracted mandibular bone is not known. The aim of this study was to assess if the sheep mandible relapses following lengthening, and to assess the quality of distracted bone up to 1 year post lengthening.
  
  
  METHODS
  Twenty-four sheep had bilateral external mandibular distractors applied, with three sheep as controls. Titanium marker screws were positioned both proximal and distal to the distraction zone in all sheep. Following a 5 day latency period, the interdental gap was distracted 1 mm/day for 20 days, with a subsequent 20 day consolidation period. Ante-mortem serial X-rays were used to assess for relapse by measuring the distance between the screws. The animals were sacrificed at either 3, 6, 9 or 12 months post-distraction. At post mortem, the distance between the screws was re-measured. The distracted bone was assessed mechanically and histologically.
  
  
  RESULTS
  The mean mandibular lengthening obtained was 13.2 mm. There was no relapse of the mandible over 12 months. The distracted bone had attained the strength and stiffness of undistracted bone by 6 months post-distraction (p < 0.05). Histological evaluation revealed significant amounts of lamellar bone by 6 months post-distraction.
  
  
  CONCLUSIONS
  No relapse occurred for 12 months post distraction lengthening. The bone formed following distraction was stable and of good quality. These findings lend support to the use of distraction osteogenesis in clinical practice.
authors.affiliation: Department of Plastic & Reconstructive Surgery, St George Hospital, Kogarah, NSW, Australia.
authors.forename: J
authors.initials: J
authors.lastname: McTavish
authors.forename: D D
authors.initials: DD
authors.lastname: Marucci
authors.forename: S F
authors.initials: SF
authors.lastname: Bonar
authors.forename: W R
authors.initials: WR
authors.lastname: Walsh
authors.forename: M D
authors.initials: MD
authors.lastname: Poole
mesh_terms: D000704:Analysis of Variance; D000818:Animals; D001861:Bone Regeneration; D016723:Bone Remodeling; D001863:Bone Screws; D002508:Cephalometry; D004396:Coloring Agents; D004548:Elasticity; D016267:External Fixators; D005500:Follow-Up Studies; D008334:Mandible / Q000000981:diagnostic imaging / Q000473:pathology / Q000601:surgery*; D019857:Osteogenesis, Distraction; D011859:Radiography; D012756:Sheep; D013223:Statistics as Topic; D013314:Stress, Mechanical; D014025:Titanium
chemical_list: D004396:Coloring Agents; D014025:Titanium