Ortho- and heterotopic bone grafts in bifocal transport osteogenesis for craniofacial reconstruction - an experimental study in sheep

Bifocal transport osteogenesis (BTO) is a promising technique for the reconstruction of extended osseous craniofacial defects. Aim of this study was to determine the potential of this technique related to various donor sites of the transport segment. In 10 adult sheep critical size defects of the calvaria were treated by gradual movement of a transport segment consisting either of autogenous regional free calvarial bone grafts (n = 5) or autogenous illiac free bone grafts (n = 5). Latency period was 5 days; the rate of distraction was I mm per day and extended approximately 40 days. The consolidation period was 28 days. After harvesting, specimens were investigated by conventional radiography, CT-scans, histologically and by fluorescence. In both groups transport osteogenesis resulted in a complete closure of the critical size defect. Membranous bone formation and remodeling occurred during the entire period of distraction and consolidation. The volumes and thickness of newly formed bone at the defect site were increased significantly when calvarial bone grafts were used (P < 0.05). Iliac bone grafts became progrediently smaller during distraction, while the volume of calvarial grafts remained relatively constant (P < 0.05). In conclusion, transport segments consisting of calvarial and iliac bone resulted in a reliable closure of craniofacial critical size defects in adult organisms; the application of calvarial bone grafts resulted in an increased extend of bone formation.