title: Accelerated repair of a bone defect with a synthetic biodegradable bone-inducing implant.
abstract: BACKGROUND
  Nothing has ever had osteoinductive capacity and degradability equivalent to that of autogenous bone, although many types of biomaterials have been developed. To address this issue, we constructed a new bone graft substitute with osteogenic potential and degradability by using porous beta-tricalcium phosphate (beta-TCP) granules, bone morphogenetic protein (BMP), and a synthetic block copolymer composed of poly-D: ,L: -lactic acid with randomly inserted p-dioxanone and polyethylene glycol (PLA-DX-PEG). In this experimental study, the bone-inducing capacity and degradation properties of the composite implant during the bone healing process were examined in vivo in a cortical and cancellous bone defect model in rabbits.
  
  
  METHODS
  The advantages of this type of implant have been examined in a cortical bone defect model created in the distal femur of rabbits. The defects (6.5 x 5 mm) were filled with 30 mg of various implants: BMP-H [rhBMP-2, 0.0025% (w/w)], BMP-L [rhBMP-2, 0.000625% (w/w)], control A (beta-TCP alone), and control B (no implant). The distal femurs were harvested at scheduled intervals after surgery and examined for the evaluation of the bony repair of the defects by three-dimensional computed tomography and histology.
  
  
  RESULTS
  The repair of both cortical and cancellous bone occurred predominantly in the BMP-H group, and only minor cortical bone repair and cancellous bone formation were noted in the BMP-L and control A groups. Most of the beta-TCP was resorbed in the BMP-H group at 6 weeks after surgery, whereas a significant amount of beta-TCP remained in the BMP-L and control A groups.
  
  
  CONCLUSIONS
  beta-TCP granules coated with a BMP-retaining synthetic polymer appear to be effective in enhancing the repair of both cancellous and cortical bone defects. The early disappearance of the implanted beta-TCP and restoration of the normal anatomy of bone tissue are two notable features of this approach.
authors.affiliation: Department of Orthopaedic Surgery, Osaka City University School of Medicine, 1-4-3 Asahi-machi, Abeno-ku, Osaka, 545-8585, Japan.
authors.forename: Naofumi
authors.initials: N
authors.lastname: Matsushita
authors.forename: Hidetomi
authors.initials: H
authors.lastname: Terai
authors.forename: Takao
authors.initials: T
authors.lastname: Okada
authors.forename: Kazutoshi
authors.initials: K
authors.lastname: Nozaki
authors.forename: Hikaru
authors.initials: H
authors.lastname: Inoue
authors.forename: Shimpei
authors.initials: S
authors.lastname: Miyamoto
authors.forename: Kunio
authors.initials: K
authors.lastname: Takaoka
mesh_terms: D020341:Absorbable Implants; D000818:Animals; D001672:Biocompatible Materials; D001847:Bone Diseases / Q000000981:diagnostic imaging / Q000601:surgery*; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D002130:Calcium Phosphates / Q000494:pharmacology*; D004195:Disease Models, Animal; D008297:Male; D019919:Prosthesis Implantation / Q000295:instrumentation*; D011817:Rabbits; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D001672:Biocompatible Materials; D019485:Bone Morphogenetic Proteins; D002130:Calcium Phosphates; C485817:beta-tricalcium phosphate