前路腰椎椎间融合术即刻稳定性的生物力学研究

The instant biomechanical stability of anterior lumbar interbody fusion

目的评价应用聚醚醚酮（poly—ether—ether—ketone，PEEK）椎间融合器行前路腰椎椎间融合的即刻生物力学稳定性。方法采用6具成人尸体腰椎标本，均来源于男性，X线检查排除腰椎疾患和明显退行性改变，双能X线骨密度检查证实所有标本骨密度均处于正常范围。截取L4～S2节段腰椎，用自凝型聚甲基丙烯酸甲酯将标本两端固定在夹具内。沿腰椎轴线加载500N的预负荷后，分别在生物力学试验机上检测以下三种状态的前屈、后伸及侧屈各方向活动的即刻稳定性：完整腰椎标本，L5S1椎间盘切除、PEEK椎间融合器植入，辅以后路椎弓根螺钉系统固定。结果l5S1椎间单纯椎间融合器植入后前屈、后伸、左侧屈方向的活动范围较完整腰椎标本分别减少76．9％、66．6％与81．1％；辅以后路椎弓根螺钉系统固定后，前屈、后伸、左侧屈方向的活动范围较完整腰椎标本分别减少93．9％、90％与86．6％。完整腰椎标本的空白对照组L4，5椎间前屈、后伸与左侧屈活动度分别为4．16°±0.33°、4．02°±0．30°、3．48°±0．34°；L5S1单纯椎间融合器组则分别为5．82°±0.36°、5．38°±0．30°、4．96°±0．29°；L5S1椎间融合器辅助椎弓根螺钉固定组则分别为4．82°±0．26°、5．76°±0.31°、3．98°±0．29°。L5S1椎间单纯椎间融合器植入及附加椎弓根螺钉固定后，L4，5椎间相对活动度显著增加，各组间差异有统计学意义（P=0．000）。结论单纯应用PEEK椎间融合器的前路腰椎椎间融合术即刻稳定性优于完整腰椎标本。辅以后路椎弓根螺钉系统固定后融合节段稳定性得到显著增强。

Objective To evaluate the instant biomechanical stability of anterior lumbar interbody fusion （ALIF） with a poly-ether-ether-ketone （PEEK） cage. Methods Six male human lumbar spines were collected; X-ray examination was performed to exclude pathology and obvious degenerative changes of the spines. Bone mineral densities of these spines were normal, identified by LUNAR DPX-L X-ray Bone Densitometer. L4-S2 segment were prepared and embedded to clamps. Preloads of 500 N was applied to specimens through longitudinal axis of the spine. Then the specimens were tested on the following 3 modes in flexion, extension and lateral bending： 1） intact lumbar spine; 2） stand alone ALIF on L5S1; 3） ALIF augmented with pedicle screw system. Results The range of motion （ROM） of stand alone ALIF decreased 76.9%, 66.6%, 81.1% in flexion, extension and lateral bending respectively. The ROM of ALIF augmented with pedicle screw system further decreased 93.9%, 90%, 86.6% in flexion, extension and lateral bending respectively. The ROM of L4,5 increased significantly after stand alone ALIF alone and ALIF augmented with pedicle screw system in L5S1. Conclusion The instant stabilities of stand alone ALIF with PEEK cage are much better than intact lumbar spine. Pedicle screw system fixation can reinforce stability of ALIF significantly.