title: Bone morphogenetic protein-2 retained in synthetic polymer/β-tricalcium phosphate composite promotes hypertrophy of a vascularized long bone graft in rabbits.
abstract: BACKGROUND
  Vascularized bone grafting is a useful method for repairing critical bone defects. The repaired bone often presents compromised mechanical strength because of insufficient thickness of the graft. To promote the hypertrophic response, bone morphogenetic protein (BMP) with osteoinductive capacity may be effective. This study was designed to evaluate the efficacy of BMP in rabbits.
  
  
  METHODS
  The first metatarsal bones with or without feeding vessels were transferred to critical-sized bone defects in the femurs of rabbits. Recombinant human (rh) BMP-2 (0, 30, or 60 μg) with a carrier material composed of 30 mg of β-tricalcium phosphate powder, 30 mg of a polymer gel (p-dioxanone/polyethylene glycol block copolymer) was placed in contact with the cortical surface and the elevated periosteum of the vascularized bone graft. After surgery, hypertrophic changes were evaluated radiographically. Twelve weeks after surgery, the reconstructed femurs were harvested for investigation by biomechanical and histologic methods.
  
  
  RESULTS
  Rapid hypertrophy was observed on radiographs in the vascularized bone grafts with rhBMP-2-retaining implants. The increase of bone volume and the biomechanical strength were dependent on the dose of rhBMP-2 (p < 0.01). Histologic sections in the vascularized bone grafts with rhBMP-2-retaining implants revealed a large amount of newly formed bone.
  
  
  CONCLUSIONS
  The potential use of BMP may improve clinical outcome by promoting hypertrophy of the vascularized bone graft and shortening the treatment time.
authors.affiliation: Osaka, Tochigi, and Nara, Japan From the Department of Orthopedic Surgery, Osaka City University Graduate School of Medicine; the Department of Orthopedic Surgery, Dokkyo Medical University School of Medicine; the Spine Center, Shiraniwa Hospital; and the Department of Orthopedic Surgery, Osaka City General Hospital.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Okada
authors.forename: Koich
authors.initials: K
authors.lastname: Yano
authors.forename: Takashi
authors.initials: T
authors.lastname: Namikawa
authors.forename: Takuya
authors.initials: T
authors.lastname: Uemura
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Hoshino
authors.forename: Kenichi
authors.initials: K
authors.lastname: Kazuki
authors.forename: Kunio
authors.initials: K
authors.lastname: Takaoka
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D055396:Bone Morphogenetic Protein 2 / Q000008:administration & dosage* / Q000494:pharmacology; D016025:Bone Transplantation / Q000379:methods*; D001842:Bone and Bones / Q000098:blood supply* / Q000166:cytology / Q000000981:diagnostic imaging / Q000187:drug effects*; D002130:Calcium Phosphates / Q000008:administration & dosage / Q000494:pharmacology; D005260:Female; D005269:Femur; D006984:Hypertrophy; D008684:Metatarsus; D009929:Organ Size; D011108:Polymers; D011817:Rabbits; D011859:Radiography; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology
chemical_list: D055396:Bone Morphogenetic Protein 2; D002130:Calcium Phosphates; D011108:Polymers; D011994:Recombinant Proteins; C485817:beta-tricalcium phosphate