title: Quantitative comparison of volume maintenance between inlay and onlay bone grafts in the craniofacial skeleton.
abstract: BACKGROUND
  Nonvascularized autologous bone grafts are the criterion standard in craniofacial reconstruction for bony defects involving the craniofacial skeleton. The authors have previously demonstrated that graft microarchitecture is the major determinant of volume maintenance for both inlay and onlay bone grafts following transplantation. This study performs a head-to-head quantitative analysis of volume maintenance between inlay and onlay bone grafts in the craniofacial skeleton using a rabbit model to comparatively determine their resorptive kinetics over time.
  
  
  METHODS
  Fifty rabbits were divided randomly into six experimental groups: 3-week inlay, 3-week onlay, 8-week inlay, 8-week onlay, 16-week inlay, and 16-week onlay. Cortical bone from the lateral mandible and both cortical and cancellous bone from the ilium were harvested from each animal and placed either in or on the cranium. All bone grafts underwent micro-computed tomographic analysis at 3, 8, and 16 weeks.
  
  
  RESULTS
  All bone graft types in the inlay position increased their volume over time, with the greatest increase in endochondral cancellous bone. All bone graft types in the onlay position decreased their volume over time, with the greatest decrease in endochondral cancellous bone. Inlay bone grafts demonstrated increased volume compared with onlay bone grafts of identical embryologic origin and microarchitecture at all time points (p < 0.05).
  
  
  CONCLUSIONS
  Inlay bone grafts, irrespective of their embryologic origin, consistently display less resorption over time compared with onlay bone grafts in the craniofacial skeleton. Both inlay and onlay bone grafts are driven by the local mechanical environment to recapitulate the recipient bed.
authors: Ann Arbor, Mich.; Boca Raton, Fla.; and Westlake Village, Calif. From the Section of Plastic and Reconstructive Surgery, Department of Surgery, University of Michigan Health System, private practice, and Westlake Oral and Plastic Surgery.
authors: Kristoffer B
authors: KB
authors: Sugg
authors: Andrew H
authors: AH
authors: Rosenthal
authors: Wayne
authors: W
authors: Ozaki
authors: Steven R
authors: SR
authors: Buchman
mesh_terms: D000818:Animals; D001862:Bone Resorption / Q000517:prevention & control; D016025:Bone Transplantation / Q000379:methods*; D019465:Craniofacial Abnormalities / Q000601:surgery*; D006085:Graft Survival / Q000502:physiology*; D007085:Ilium / Q000637:transplantation*; D008334:Mandible / Q000601:surgery*; D011183:Postoperative Complications / Q000517:prevention & control; D011817:Rabbits; D011897:Random Allocation; D020858:Tissue and Organ Harvesting / Q000379:methods; D014182:Transplantation, Autologous
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