Regulation of Osteogenesis and Survival within Bone Grafts to the Calvaria: The Effect of the Dura versus the Pericranium

The present study evaluates the isolated role of dura and pericranium in the survival of fresh (osteoblasts viable) and frozen (osteoblasts nonviable) bone grafts. Bilateral craniectomies were performed in 48 mature rabbits. On one side, bone was replaced immediately; on the contralateral side, it was flash-frozen before replacement. Animals were randomized into four groups by placement of Silastic barriers adjacent to bone grafts, as follows: (1) control (no barriers); (2) dural barrier; (3) pericranial barrier; and (4) double (dural and pericranial) barriers. Fluorescein labels were injected at specified intervals, with animals euthanized after 1 or 10 weeks. After 1 week, fresh grafts without dural barriers demonstrated greater fluorescein labeling on the dural than on the pericranial surface (p < 0.05); in contrast, fresh grafts without pericranial barriers had no statistical difference in fluorescein labeling between pericranial and dural surfaces. After 10 weeks, the new bone area was greater in fresh than in frozen grafts (p < 0.05). Total new bone area and dural-side new bone were greater in grafts without dural barriers (p < 0.001); this was not seen in grafts without pericranial barriers. Pericranial new bone was greatest in fresh grafts without a pericranial barrier (p < 0.001); this was not seen in frozen grafts. The dura and pericranium each contributed to osteogenesis, although dural contact was more effective. Maintenance of dural contact enhanced osteogenesis through the entire graft, whereas pericranial contact enhanced osteogenesis only on the pericranial surface of fresh grafts. These data suggest dura is largely responsible for cranial graft survival.