摘要目的 探讨延迟分离适宜时间及其促进延长区骨愈合机制。 方法 对68只兔左胫骨干骺端截骨，按开始延长时间不同分为4组，采用微血管铸型、力学强度等方法进行动态观察和比较。 结果 截骨术后第4天，截骨断端髓腔血管开始吻合沟通。延长过程中，延长区血管网丰富，仅早期术后立即延长组血管网略显稀疏。 结论 恰当的延迟分离延长有利于延长区的骨形成和改建；延迟分离时间过长，并不能进一步加速延长区骨愈合和改建，同时存在严重并发症的潜在风险；延迟分离可能的机制是有利于截骨断端血循环的重建，适宜的延迟分离时间应根据截骨断端血循环重建所需时间而定。

abstractsObjective To investigate the mechan ism and the optimal time ofdelayed distraction. Methods By means of X-ray,microvascular cast SEM, and mechanical strength t est, we observed in 68 Japanese white rabbits, delayed distraction of different postoperative days. Results It was found that on the 5th day after osteoctomy the blood circulation between the osteotomy ends had been reestablished.On the 90th postoperative day, the mechanical strength w as best in the group of delayed distraction on the 5th day after osteotomy.No no nunion was found in this group. Conclusions Delayed distraction is of benefit to bone healing in the lengthened zone, and th e optimal delayed is dependent on the day when the blood circulation of osteotom y site.