动力内固定融合术对失稳脊柱稳定作用的实验研究

目的：探讨动力椎弓根螺钉内固定的优越性。方法：18只山羊随机分为3组，正常对照组（A组，仅作脊柱后路皮肤切开，L2～L4节段椎旁肌剥离）、动力固定融合组（B组，在A组基础上切除L3后部结构后行动力固定融合）和坚强同定融合组（C组，同B组但改为坚强固定融合）。术后24周处死动物，截取L1-L6节段脊柱标本，在脊柱三维运动试验机上测试固定节段运动范围，然后在MTS 858试验机上进行压缩刚度测试。A组标本测试完后切除L3后部结构作为损伤组（D组）重复稳定性和刚度测试，B组和C组取出内固定器后重复刚度测试。结果：与D组相比．B组和C组屈伸、侧弯和轴向旋转活动范围明显减少（P〈0．01），而且在屈伸、侧弯方向上比A组更稳定。与D组相比，B组和C组刚度均显著性提高（P〈0.01）；B组和C组内固定器取出后与取出前刚度之比的均值分别为85．51％、74．49％，有显著性差异（P〈0．05）。结论：动力内固定和坚强内固定融合均能恢复山羊失稳脊柱的稳定性，但动力内同定能增加载荷分享。

Stability analysis of a dynamic pedicle screw fixation device with posterolateral fusion in goat model

Objective: To compare the stability of dynamic pedicle screw fixation device(DD) to its equivalentrigid pedicle screw fixation device (RD) with posterolateral fusion in vivo goat model.Method:18 goats wererandomly divided into three groups:control normal group (group A), dynamic device with posterolateral fusiongroup(group B) and rigid device with posterolateral fusion group(group C).After 24 weeks postoperative obser-vation, the lumbar was harvested.The stability biomechanical test was done by measuring range of motion(ROM) in six motion modes.Maximal load was carried out in every specimen in the spinal three- dimensionmotion biomechanical test machine.Then the specimen was performed on axial compression test in the MTS858testing device.The average compression stiffness of the last three cycles was recorded.After the above test, thespecimen in normal group was injured by resecting L3 posterior structure as injured group (group D) and thesame biomechanical test was performed again.Compression stiffness test was performed again in group B and Cafter carefully removing of the fixation.Result:The stability test indicated that ROM in all testing modes ingroup B and C decreased significantly compared with the injured group (P<0.01).Group B and C showed morestability than normal group in the aspect of flexion-extension and lateral bending.There was no significantdifference between group B and C in all test modes.The average stiffness of axial compression in the injuredgroup decreased significantly compared with normal group.Group B and C showed larger compression stiffnessthan injured group (P<0.01).The compression stiffness values of those with fixation removal to those withfixation demonstrated 85.51%, 74.49% in group B and C respectively (P<0.05).Conclusion:Both the dynamicdevice and rigid device with posterolateral fusion could provide spinal stability.The dynamic device canenhance load sharing.