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Repair of a Critical Porcine Tibial Defect via Allograft Revitalization
Christopher Runyan, M.D., Ph.D., Samantha Ali, BS, Donna Jones, PhD, David Billmire, MD, Jesse Taylor, MD.
Cincinnati Children's Hospital Medical Center
2012-02-01
Presenter: Samantha Ali (M1, University of Cincinnati)
Affidavit:
The research submitted represents a collaboration of the work between all four authors. To be specific, the presenting student, Samantha Ali, devised a protocol for radiographic analysis, assisted with both surgical osteotomies, and analyzed micro CT data to assess tibial healing.
Director Name: David Billmire, M.D.
Author Category: Student
Presentation Category: Clinical
Abstract Category: Craniomaxillofacial
How does this presentation meet the established conference educational objectives?
This presentation will address the issues currently faced during repair of critical bony defects. Utilizing an allograft scaffold for repair of bony defects is an alternative to autograft which often leaves considerable donor mortality and may lack adequate available bone for use. Allograft bone, alone, lacks vascularity. Therefore it does not heal, grow, and remodel in vivo, which contributes to significant failure rates (40-60%) after 10 years. The addition of autologous adipose-derived stem cells, recombinant human Bone Morphogenetic Protein, and native periosteum to the allograft scaffold allow for introduction of vasculature and consequently, better healing outcomes. Allograft revitalization provides patients with bone that is capable of remodeling itself, adding an aesthetic value for craniofacial defects. Revitalized allograft possesses mechanical strength identical to living bone and an ability to heal after subsequent fractures.
How will your presentation be used by practicing physicians in the audience?
This technique provides a strong and equally effective alternative to autograft and allograft surgical repair of critical size defects. It also addresses some of the suboptimal aesthetic and functional issues faced with the use of autograft for repair of the defects due to the lack of a donor site and the bone's ability to remodel itself.
Purpose: We examined the efficacy of 'allograft revitalization', a technique using hemi-mandibular allograft scaffold, autologous adipose derived-stem cells (ASCs), recombinant human Bone Morphogenetic Protein-2 (rhBMP-2) and native periosteum, to repair a critical defect relative to other standards of care.
Methods: Bilateral, 3 cm defects were created in the tibial diaphysis of 9 pigs. Three repair strategies were tested. 'Negative control' (NC) defects were repaired with allograft tibia. 'Positive control' (PC) defects were osteotomized and left in situ, with the posterior, native periosteum intact. 'Experimental' (EXP) defects were repaired with allograft tibia packed with ASCs and rhBMP-2 (0.5mg/ml rhBMP-2 solution, Medtronic), with native periosteum intact. Constructs were secured by plate and screw fixation. Each group contained six tibias. Healing was assessed based on physical exam and serial radiography. Eight-weeks post-grafting, 3 tibias in each group were osteotomized mid-graft to assess healing potential. After an additional seven weeks, explants were harvested for micro-CT and standard histologic analysis.
Results and Conclusion: At seven weeks, no NC defects had healed (0/6) whereas most PC (5/6) and all EXP (6/6) defects were radiographically healed. Seven weeks following repeat graft osteotomies (3 per group), No NC defects produced bony union (0/3), whereas all PC (3/3) and EXP (3/3) defects healed. No clinical and radiographic differences were found between the PC and EXP groups, indicating revitalized allograft performed as well as autograft for healing a critical defect in this model.
