OBJECTIVETo study the ultrastructure and Ca/P element spectrometry of distraction osteogenesis (DO) for reconstruction of cleft palate (CP), so as to explore the osteogenesis and remodeling of new bone in situ.

METHODS23 rhesus macaques were operated to establish animal models of CP. 2 monkeys didn't received DO as controls. The other 21 monkeys in experimental group underwent DO to correct both bony and soft tissue defects in palate. The distraction was performed at a rate of 0.8 mm/d, twice a day until the cleft was closed. After fixation for 1, 2, 4, 6, 8, 12, 24 weeks, every 3 animals were sacrificed to get the specimens at the distraction gap. The scanning electron microscopic study and Ca, P elements spectrometric analysis were adopted. There were also two unoperated animals as sham group.

RESULTSAfter fixation for 1-2 weeks, the distraction gap was full of collagen fibers oriented along vector of distraction. Few trabeculae was seen at the margin area. After fixation for 4-6 weeks, active osteogenesis was presented with new formed bone trabeculae and abundant cellular component. After fixation for 8-12 weeks, the new formed bone became mature and couldn't distinguish from the normal bone. 24 weeks later, the bone between the distraction gap had a similar structure to the normal bone. Elements spectrometric analysis results indicated that in early stage of osteogenesis, the P and S peaks were relatively high while the Ca peak was much lower. During the late stage, the S peak was obviously decreased, and Ca/P ratio increased to normal level as in the empty control group.

CONCLUSIONSThe CP can be corrected by DO. The new bone between the distraction gap is formed and remodeled through intramembraneous osteogenesis.