• Vol. 36 No. 11, 911–919
  • 15 November 2007

Bone Generation in the Reconstruction of a Critical Size Calvarial Defect in an Experimental Model

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ABSTRACT

Objective: This study was designed to investigate the optimal combination of known osteogenic biomaterials with shape conforming struts to achieve calvarial vault reconstruction, using a canine model. Methods: Eighteen adolescent beagles were divided equally into 6 groups. A critical size defect of 6 x 2 cm traversed the sagittal suture. The biomaterials used for calvarial reconstruction were demineralised perforated bone matrix (DBM), recombinant human bone morphogenetic protein-2 (rhBMP2) and autogenous platelet-rich plasma (PRP). The struts used were cobalt chrome (metal) or resorbable plate. The groupings were as follows: 1) DBM + metal, 2) DBM + PRP + metal, 3) DBM + PRP + resorbable plate, 4) DBM + rhBMP2 + metal, 5) DBM + rhBMP2 + PRP + metal, and 6) DBM + rhBMP2 + resorbable plate. Animals were euthanised at 3 months post-surgery. There was no mortality or major complications. Analysis was performed macroscopically, histologically, and with computed tomography (CT). Results: There was complete bony regeneration in the rhBMP2 groups only. Non-rhBMP2 groups had minimal bony ingrowth from the defect edges and on the dural surface, a finding confirmed by CT scan and histology. PRP did not enhance bone regeneration. Shape conformation was good with both metal and resorbable plate. Conclusion: rhBMP2 but not PRP accelerated calvarial regeneration in 3 months. The DBM in the rhBMP2 groups were substituted by new trabecular bone. Shape molding was good with both metal and resorbable plate.


The successful separation of a pair of craniopagus twins resulted in significant cranial vault defects that required reconstruction.1 Previously, calvarial reconstruction in separated craniopagus twins was postponed until adolescence when autologous bone was more plentiful.2 The goals of pediatric calvarial reconstruction are to provide protection for the brain, to enable normal growth of the cranial vault and to reduce deformity of the head shape. Several principles are applicable in pediatric calvarial reconstruction. Autologous bone is the material of choice. Alloplastic materials such as hydroxyapatite are less commonly used because of a lack of osseointegration and a tendency to develop foreign body reactions. Demineralised bone matrix (DBM) is widely used by the authors and has been proven to be safe when obtained from trusted sources.3 DBM is osteoinductive and osteoconductive and becomes mineralised after 1 year. However, it does not provide strength for structural support or maintenance of head shape until neo-osteogenesis is complete. Alternatively, to cover large defects, implantable materials such as titanium mesh and polymer custom made implants may be considered in an adult but not in the growing child, who would outgrow these rigid materials rapidly.

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