新型β钛合金半针低弹性模量外固定系统对实验犬胫骨骨折愈合的影响

Effect of external fixation system of low elastic modulus with halfpins made of 15 titanium alloy on bone healing in canine models of tibial fracture

目的探讨新型13钛合金半针低弹性模量外固定系统对实验犬胫骨骨折愈合的影响。方法选取健康杂种犬20只，雌雄不限，建立实验犬胫骨骨折模型并随机分成2组（n=10），分别采用新型13钛合金Ti-24Nb．4Zr．7．9Sn（低弹性模量组，弹性模量为42GPa）和仅＋B钛合金Ti．6A1．4V（高弹性模量组，弹性模量为110GPa）制备外固定半针，并连接其他相同部件，构建低弹性模量及高弹性模量单边外固定系统固定胫骨骨折。运用Micro—CT影像分析技术及骨强度生物力学试验分析两组实验犬胫骨骨折愈合的情况。结果术后2个月两组实验犬胫骨骨折均获愈合。与高弹性模量组相比，低弹性模量组骨密度更大、骨小梁间隙更小、骨小梁厚度更大、骨小梁数目更多，两组比较差异均有统计学意义（P〈0．05），因此，低弹性模量组愈合骨数量及质量均优于高弹性模量组。骨强度生物力学试验证实低弹性模量组愈合骨能够承载的力学负荷较高弹性模量组更大，差异有统计学意义（P〈0．05）。结论与高弹性模量外固定系统比较，新型B钛合金半针低弹性模量外固定系统固定胫骨骨折更有利于骨折的愈合和坚强固定，可更早拆除外固定系统。

Objective To explore the effect of the external fixation system of low elastic modulus low elastic modulus with halfpins made of 13 titanium alloy on bone healing in canine models of tibial fracture. Methods Twenty healthy mongrels were used to establish canine models of tibial fracture for this experi- ment. Next they were randomized into 2 even groups （10 each）. The fractures in the 2 groups were subjected respectively to external fixation of low versus high elastic modulus. The external fixation system of low elastic modulus contained halfpins made of [3 titanium alloy Ti-24Nb-4Zr-7.9Sn （G = 42 GPa） while that of high e- lastic modulus contained halfpins made of ct ＋ 13 titanium alloy Ti-6A1-4V （G = 110 GPa） . The other com- ponents of the 2 external systems were the same. The bone healing was observed and compared between the 2 groups using Micro-CT and biomechanical analyses at 2 months after operation. Results After 2-month treatment, the fractures healed in both groups. Compared with the high elastic modulus group, the low elastic modulus group had significantly greater bone mineral density, significantly smaller trabecular spacing （Tb. Sp）, significantly greater trabeeular thickness （Tb. Th）, and significantly greater trabecular number （Tb. N） （all P 〈 0. 05）. The newly healed bone in the low elastic modulus group was superior to that in the high elastic modulus group in both quantity and quality, and the former had significantly greater biomechanical strength than the latter （ P 〈 0. 05）. Conclusion External fixation system of low elastic modulus low elastic modulus with halfpins made of 13 titanium alloy can reduce the effect of stress-shielding to achieve more rigid fixation which may lead to better bone healing, and consequently earlier removal of external fixation system as well.