title: Treatment of large calvarial defects with bone transport osteogenesis: a preclinical sheep model.
abstract: BACKGROUND
  Bone transport osteogenesis (BTO), distraction of a free portion of bone across a defect, offers an autologous solution to large cranial defects that may allow treatment without permanent hardware implantation. This study establishes a sheep model to evaluate the feasibility and distraction kinetics of BTO.
  
  
  METHODS
  Subtotal cranial defects (3.5 × 3.5 cm) were created in 10 young adult sheep and a transport segment (3.5 × 2 cm) traversed the defect at varying distraction rates (0, 0.5, 1.0, and 1.5 mm/day) using semi-buried cranial distractors. After a 6-week consolidation period, sheep were euthanized and the resultant bone was analyzed by CT, histology, and mechanical testing.
  
  
  RESULTS
  Gross examination, histology, and 3D CT revealed that control animals had fibrous nonunion whereas distraction animals had ossified defects with fibrous nonunion at the distal docking site. There was one premature consolidation in the 0.5 mm/day group. The volume of bony regenerate in the 0.5, 1.0, and 1.5 mm/day distraction rate groups was statistically indistinct (P = 0.16). The mean flexural moduli (MPa) of non-decalcified samples from the control cranium, transport segment, and bone regenerate were found to be 4.50 ± 4.9, 6.17 ± 2.1, and 4.14 ± 4.8, respectively (P = 0.24).
  
  
  CONCLUSIONS
  This experiment provides proof of concept for BTO for large calvarial defects in a sheep model. Distraction at a rate of 0.5 mm per day may place individuals at higher risk for premature consolidation, but distraction rates did not have significant effects on regenerate quantity or quality. Future work will include the use of curvilinear distraction devices for 3-dimensional contour.
authors.affiliation: From the Divison of Plastic Surgery, The Perelman School of Medicine at the University of Pennsylvania; Division of Plastic Surgery, The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
authors.forename: Patrick A
authors.initials: PA
authors.lastname: Gerety
authors.forename: Jason D
authors.initials: JD
authors.lastname: Wink
authors.forename: Rami D
authors.initials: RD
authors.lastname: Sherif
authors.forename: Nadya
authors.initials: N
authors.lastname: Clarke
authors.forename: Hyun-Duck
authors.initials: HD
authors.lastname: Nah
authors.forename: Jesse A
authors.initials: JA
authors.lastname: Taylor
mesh_terms: D000818:Animals; D016025:Bone Transplantation / Q000379:methods*; D004195:Disease Models, Animal; D005240:Feasibility Studies; D019857:Osteogenesis, Distraction / Q000379:methods*; D019651:Plastic Surgery Procedures / Q000379:methods*; D012756:Sheep; D012886:Skull / Q000293:injuries / Q000601:surgery*; D014057:Tomography, X-Ray Computed