title: Extracortical bone-bridging fixation with use of cortical allograft and recombinant human osteogenic protein-1.
abstract: BACKGROUND
  Prosthetic reconstruction with extracortical bone-bridging fixation is an effective method for the treatment of massive bone loss. We evaluated the effect of the use of recombinant human osteogenic protein-1 (rhOP-1) combined with allogenic cortical bone strips as a substitute for an autogenous bone graft for extracortical bone-bridging.
  
  
  METHODS
  Eight skeletally mature adult male dogs underwent a bilateral resection of a 6-cm segment of the femoral diaphysis and reconstruction with a porous segmental prosthesis. On the experimental side, an allogenic cortical onlay graft in the form of bone strips combined with rhOP-1 mixed with bovine type-I-collagen putty (OP-1 putty) was applied. On the control side, allogenic cortical bone strips augmented with autogenous cancellous bone chips and bone marrow were used. The reconstructions were followed for twelve weeks with biweekly evaluations of load-bearing gait and radiographs. The animals were killed twelve weeks after the surgery, and the reconstructed femora were studied biomechanically, histologically, and with microradiographs.
  
  
  RESULTS
  One animal was excluded from the analysis because a fracture of the proximal part of the femur on the control side was observed radiographically twelve weeks after the surgery. There were no significant differences in load-bearing gait between the experimental and control sides throughout the experimental period. Serial radiographs revealed a 1.9-fold (p<0.04), 2.7-fold (p<0.01), and 2.4-fold (p<0.03) increase in mineralized area on the experimental side at two, four, and six weeks, respectively. The torsional stiffness and strength of the fixation attributed to the extracortical bridging bone alone were 2.3-fold (p<0.03) and 2.2-fold (p=0.058) greater on the experimental side, respectively. The allograft porosity on the experimental side was 3.8-fold (p<0.02) greater than that on the control side. With the number of samples available, there was no significant difference in mineral apposition rate between the experimental and control sides.
  
  
  CONCLUSIONS
  In an animal model of segmental bone-replacement prosthetic fixation with use of the extracortical bone-bridging principle, an allogenic onlay cortical graft combined with rhOP-1 was an effective substitute for autogenous bone graft.
authors.affiliation: Department of Orthopaedic Surgery, Johns Hopkins University School of Medicine, 601 North Caroline Street, 5215 Johns Hopkins Outpatient Center, Baltimore, MD 21287, USA.
authors.forename: Jun
authors.initials: J
authors.lastname: Fukuroku
authors.forename: Nozomu
authors.initials: N
authors.lastname: Inoue
authors.forename: Bahman
authors.initials: B
authors.lastname: Rafiee
authors.forename: Franklin H
authors.initials: FH
authors.lastname: Sim
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Frassica
authors.forename: Edmund Y S
authors.initials: EY
authors.lastname: Chao
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins / Q000494:pharmacology*; D016025:Bone Transplantation; D004285:Dogs; D005269:Femur / Q000000981:diagnostic imaging / Q000601:surgery*; D006801:Humans; D008297:Male; D023421:Models, Animal; D016348:Osseointegration; D019736:Prostheses and Implants; D011474:Prosthesis Design; D011859:Radiography; D016212:Transforming Growth Factor beta / Q000494:pharmacology*; D014184:Transplantation, Homologous; D016474:Weight-Bearing
chemical_list: C525819:BMP7 protein, human; D055419:Bone Morphogenetic Protein 7; D019485:Bone Morphogenetic Proteins; D016212:Transforming Growth Factor beta