腰椎新型钛合金动态内固定系统的稳定性研究

Stability evaluation of a new Iumbar dynamic systems made of a new type titanium-alloy

目的检测由新型钛合金制成的非融合腰椎动态内固定系统的稳定性。方法收集6具平均6月龄的新鲜小牛腰椎标本，在连续的5种状态下，即完整状态、失稳状态、使用DIFSⅠ系统（椎弓根螺钉的弹性模量为75GPa，由新型钛合金制成，其连接棒弹性模量为43GPa，直径为3．5mm）动态固定状态、使用DIFSⅡ系统（椎弓根螺钉的弹性模量为75GPa，由新型钛合金制成，其连接棒弹性模量为72GPa，直径为3．5mm）动态固定状态、使用对照组SINO系统（短尾“U”形椎弓根系统，连接棒直径为5．5mm）坚固固定状态，对小牛L2-6施加10N·m的纯力矩，测量标本在三维6个方向前屈、后伸、左右侧屈和左右旋转的活动范围（ROM）和中性区（NZ）。结果在失稳状态下L3，4 6个方向的ROM和NZ与其他各状态比较，差异均有统计学意义（P〈0．05）。DIFSⅠ系统动态固定与完整状态和SINO系统固定比较差异均无统计学意义。DIFSⅡ系统动态固定与完整状态各方向的ROM和NZ比较差异有统计学意义（P〈0．05），DIFSⅡ系统动态固定与SINO系统固定的各方向ROM和NZ比较差异无统计学意义。L2，3和L4，5的各种状态下6个方向的ROM和NZ比较差异无统计学意义。结论DIFSⅠ系统动态固定既可以维持腰椎的活动性，又可以获得坚强固定的稳定性；DIFSⅡ系统动态固定性质更接近坚强固定。

Objective To investigate whether the new dynamic internal fixation system （DIFS Ⅰ, DIFS Ⅱ ） is capable to restore the physiologic motion characteristic of a spinal segment after operation. Methods Six calf specimens （L2-6） （median age 6 months） were collected. The specimens were loaded with pure moments of 10 N·m in flexion/extension, lateral bending, and axial rotation. The specimens were tested under the following conditions： 1） intact; 2） instable with operating on L3,4; 3） dynamic fixing with DIFS Ⅰ ; 4） dynamic fixing with DIFS Ⅱ ;5） fixing with SINO system. The range of motion （ROM） at six dictions （flexion, extension, left lateral bending, right lateral bending, left axial rotation, and right axial rotation） and neutral zone （NZ） at the fixed and adjacent segments were analyzed using analysis of variance and multiple comparisons with Bonferroni correction. Results For the fixed segment, the defect increased the median values of the ROM and NZ in flexion-extension, lateral bending and axial rotation, comparing with other status （P〈 0.05）. After fixation of the implant, the DIFS Ⅰ had no significantly difference with the intact condition, DIFS Ⅱ and SINO system, but the DIFS Ⅱ and SINO system decreased the ROM and NZ in all directions compared with the intact condition （P〈 0.05）. The DIFS Ⅱ had no significantly difference with SINO system at the ROM and NZ. At all atatus, there were no significantly differences at the ROM and NZ in L2,3 and L4,5 segments. Conclusion The new dynamic non-fusion internal systems DIFS Ⅰ almost ideally restored the fixed segmental ROM and NZ in flexion-extension, lateral bending and axial rotation to the intact condition and restabilize the defect; the character of DIFS Ⅱ was simile to the SINO system.