Cranial defect reconstruction in an experimental model using different mixtures of bioglass and autologous bone

The purpose of this study was to investigate bone healing in a rabbit cranial defect model using different mixtures of bioglass (NovaBone C/M; Porex Surgical, Inc., Newnan, GA) and autologous bone with and without an overlying absorbable plate (Lactosorb; Walter Lorenz Surgical, Jacksonville, FL). Twelve rabbits were divided into three groups, and a 2 cm diameter cranial defect was created in each rabbit. Group I defects were filled with 80% bioglass and 20% autologous bone, group II with 60% bioglass and 40% autologous bone, and group III with 60% bioglass and 40% autologous bone with the addition of an absorbable plate placed directly over the reconstructed defect to help separate it from the overlying soft tissues. Rabbits were euthanized 6 months postoperatively. Histologic examination was then performed. The size of the remaining bone gap, area of reossification within the defect, and percentage of fibrous tissue within the defect were measured. Histologic analyses revealed that group II animals had an increased cross-sectional area of bone formation and decreased bone gap when compared with group I and III animals (P < 0.05). There were no statistical differences between groups I and III with regard to bone formation. This study suggests that when combining bioactive glass and autologous bone for repairing cranial defects, a combination of 60% bioactive glass and 40% bone graft yields superior results to a combination of 80% bioactive glass and 20% bone graft. Placing an absorbable plate over a defect filled with 60% bioactive glass and 40% bone graft inhibits rather than promotes reossification.