Objective To compare the expression of nitricoxide synthase（NOS） in the osteogenesis tissues of gradual distraction and split osteotomy, and investigate molecular biology mechanism. Methods Thirty-six rabbits were randomly divided into gradual distraction group, high split osteotomy group and control group. A batch of 4 animals in each of the first 2 groups were sacrificed respectively on the 1st day, 1st, 2nd and 4th weeks after operation. The local changes of the tissues between bony segments were observed by inspections, radiography, HE staining, and immunological evaluation of NOS. The areas occupied by positive cells with inducible nitric oxide synthase（iNOS） and endothelial nitric oxide synthase（eNOS） were compared statistically within and among different batches. Results Immunologically, little expression of iNOS and eNOS could be detected in normal bone. In gradual distraction group, the iNOS stains were at peak values at 1st day, eNOS at 1st week postoperatively. In split osteotomy group, the iNOS stain were at peak values at 2nd week, eNOS at 1st week postoperatively. The nNOS was not detected in both of the groups. Conclusion Routine procedure of distraction produced better osteogenesis, whereas split osteotomy with free bony segments would lead to abnormal osteogenesis.
