title: Distraction osteogenesis after irradiation in a rabbit model.
abstract: BACKGROUND
  The present study was performed to investigate the effects of preoperative irradiation on distraction osteogenesis, as little is known about how preoperative irradiation delays distraction osteogenesis.
  
  
  METHODS
  A single dose of irradiation was applied to the right rear legs of rabbits. This was followed by tibial lengthening at a rate of 0.5 mm/day, which was continued for 4 weeks. Bone regeneration was examined radiographically and histologically.
  
  
  RESULTS
  In the irradiation group, the radiographs showed little regeneration during the elongation phase. During the maturation phase, the callus appeared slowly, and its formation was spotty. Furthermore, regeneration was not completed until the fourth week of the maturation period. Histological examination at the end of distraction showed a gap in the distraction consisting of loose connective tissue, with part of the fibrous tissue oriented longitudinally. Four weeks after completion of distraction, the major part of the radiolucent region consisted of cartilage. The spotty osteogenesis was identified as enchondral ossification. Immunohistochemical examination of the regeneration area revealed that the blood vessels were extremely localized, and that the level of expression of vascular endothelial growth factor (VEGF) in the osteoblasts was high. Microangiography showed that vascularization at the distracted sites was poor. Distraction osteogenesis was decreased markedly by preoperative irradiation in terms of both rate and process. The results suggested that most of the osteoprogenitor cells were damaged immediately after irradiation. The high level of VEGF in the osteoblasts and the enchondral ossification also suggested a hypoxic state in the distracted region.
  
  
  CONCLUSIONS
  Preoperative irradiation interferes with distraction osteogenesis by inducing a state of poor angiogenesis.
authors.affiliation: Department of Orthopedic Surgery, Graduate School of Medical Science, Kanazawa University, 13-1 Takara-machi, Kanazawa, 920-8641, Japan.
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Tsuchiya
authors.forename: Kenji
authors.initials: K
authors.lastname: Uehara
authors.forename: Keisuke
authors.initials: K
authors.lastname: Sakurakichi
authors.forename: Koji
authors.initials: K
authors.lastname: Watanabe
authors.forename: Hidenori
authors.initials: H
authors.lastname: Matsubara
authors.forename: Katsuro
authors.initials: K
authors.lastname: Tomita
mesh_terms: D000792:Angiography; D000818:Animals; D002648:Child; D006801:Humans; D008297:Male; D018919:Neovascularization, Physiologic / Q000528:radiation effects*; D019857:Osteogenesis, Distraction; D011817:Rabbits; D013977:Tibia / Q000033:anatomy & histology / Q000528:radiation effects; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism
chemical_list: D042461:Vascular Endothelial Growth Factor A