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Biomechanical Assessment of Calvarial Reconstruction: Biomechanical Assessment of Cranial Defects Repaired with Cryopreserved and Fresh Autologous Graft

Zoe M. MacIsaac, Sameer Shakir, Sanjay Naran, J. Cray, Darren M. Smith, Mark P. Mooney, Gregory M. Cooper, Joseph E. Losee
University of Pittsburgh
2013-02-28

Presenter: Zoe M MacIsaac

Affidavit:
All material in this presentation is the work of Zoe MacIsaac, with help from co-authors.

Director Name: Joseph E Losee

Author Category: Other Specialty Resident
Presentation Category: Basic Science Research
Abstract Category: Craniomaxillofacial

BACKGROUND:
The purpose of this study was to compare biomechanical properties of fresh, autologous reconstruction, versus reconstruction with cryopreserved autologous graft.

METHODS:
Sixteen adult New Zealand White rabbits underwent subtotal calvariectomy (15 x 15 mm2). In Group 1 and 2, bone flaps were immediately replaced. In Group 3, defects were repaired with cryopreserved calvarial graft. Animals underwent CT at 0 and 6 weeks (Group 2, through 6 months), followed histological analysis. Biomechanical analysis with an unconfined compression test was performed: Compression at 0.1mm/min to 80% of initial thickness, 1-hour equilibration, then compression by 1800N.

RESULTS:
Biomechanical results for Groups 1, 2 and 3, respectively: Stress at 80% (MPa) 3.5±2.2, 4.8±1.2, 5.4 ± 1.3; relaxation stress (MPa) 2.1±1.5, 3.0±0.7, 3.2 ± 0.9; final strain at 1800N 0.42±0.0, 0.42±0.1, 0.43±0.1.There were no significant differences between time points for fresh autologous graft, nor were there significant differences between fresh and cryopreserved bone graft at 6 weeks postoperatively. Histologically, lacunae appeared more cellular at both time points for fresh autologous reconstruction, compared to cryopreserved reconstruction. Pentachrome staining revealed more remodeling in cryopreserved reconstruction, compared to reconstruction with fresh autologous graft.

CONCLUSIONS:
Both fresh and cryopreserved calvarial graft provided radiographic coverage; both methods of reconstruction resulted in equivalent biomechanical properties. At six weeks, cryopreserved graft exhibited more remodeling than did fresh autologous graft. Further studies are warranted to determine how biomechanical properties evolve over the long term.

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