Spontaneous healing responses of rabbit cranial defects of various sizes

Abstract

[한글]

[영문]This study evaluated the spontaneous healing responses in surgically produced cranial defects in rabbits at different healing periods in order to determine the critical size defect (CSD) of the rabbit cranium.Thirty-two New Zealand white rabbits were used in this study. Defects of three sizes (6, 8, and 11 mm) were created in each of 16 randomly selected rabbits, and 15-mm defects were created individually in another 16 rabbits. The defects were analyzed using radiography, histologic analysis, and histometric analysis after the animal was sacrificed at 2, 4, 8, or 12 weeks postoperatively. Four samples were analyzed for each size of defect and each healing period.The radiographic findings indicated that defect filling gradually increased over time and that smaller defects were covered with a greater amount of radiopaque substance. Bony islands observed at 8 weeks at the center of the defect in both histologic sections and radiographs were speculated to have originated from the periosteum. In addition, the newly formed bone had matured markedly at 8 weeks. In the 15-mm defects, which corresponds to the CSD used in many studies investigating bone regeneration, the defect closure and new bone area ratio were 50.2±18.0% (mean±standard deviation) and 20.1±5.9%, respectively, for the 12-week healing period. The new bone ingrowth and the new bone area did not differ significantly with the defect size for the same healing period, which indicates a constant healing capacity from the defect margin. There was a small statistically significant difference in the defect closure and new bone area ratio between weeks 2 and 4 and between weeks 8 and 12 in each defect group. The results obtained for the spontaneous healing responses of rabbit cranial defects over time and the underlying factors may provide useful guidelines for the development of a rabbit cranial model for in vivo investigations of new bone materials.