The importance of the dura in craniofacial surgery.

The hypothesis of this study is that craniofacial procedures that rely on devascularization of cranial bone are successful largely because of the unique environment that the dura offers. This hypothesis was tested by sequentially labeling animals with tetracycline and studying the healing of cranial bone grafts when replaced immediately and when subjected to room air exposure for 90 minutes and contrasting healing in mature and immature animals. Bilateral parietal bone flaps were harvested from guinea pigs. On one side, the bone was replaced as a control, and on the other side, the dura was resected prior to replacing the bone flap. The animals were divided into four groups of five animals each. The first and second groups were immature animals (3 to 4 weeks of age), and the third and fourth groups were mature animals (4 to 6 months of age). In the first and third groups, the bone flaps were replaced immediately, and in the second and fourth groups, the bone flaps were exposed to room air for 90 minutes, since this has been shown to destroy surface osteocytes and simulates extreme exposure conditions that could occur in clinical situations. Sequential marking with tetracycline was performed to study the mineralization rate and overall matrix formation. Significantly decreased mineralization rates occurred in bone flaps not in contract with dura. In those bone flaps exposed to room air for 90 minutes, healing occurred only on the side where dura was present. The clinical implications of the importance of the dura in craniofacial procedures are discussed.