PEEK椎弓根螺钉内固定系统对椎间盘内压力变化影响的生物力学研究

Biomechanical study on the effect of PEEK rods system on the intradiscal pressure of adjacent segments

[目的]通过体外生物力学实验分析PEEK棒椎弓根螺钉内固定系统对相邻节段椎间盘内压力(Intradiscal pressure,IDP)的影响。[方法]取10具适当长度新鲜的羊脊柱标本(L_3~L_6),对每具标本依次行不同方式内固定处理,依据处理方式分为以下5个实验组:未处理组(Intact组)、钛棒单节段融合组(TS组)、PEEK棒单节段融合组(PS组)、PEEK棒双节段杂交组(PD组)和钛棒双节段融合组(TD组)。每个标本通过MTS多自由度脊柱运动模拟测试系统完成前屈、后伸、左/右侧弯、左/右扭转6个方向的完整动作。轴向压力为50 N,扭矩大小为:3 N.m。运用针孔式压力传感器测试每个方向运动状态下的椎间盘压力值。[结果]TS组及PS组的上位邻近节段IDP值高于Intact组(P<0.05);PS组上位相邻节段椎间盘压力值明显低于TS组(P<005);PD组过渡阶段椎间盘压力值明显低于TS组上位相邻节段椎间盘压力值(P<0.05);PD组上位相邻节段椎间盘压力值明显低于TD组(P<0.05)。[结论]与坚强固定相比,应用PEEK棒椎弓根螺钉内固定系统可显著降低相邻节段椎间盘内压力,这可能是降低相邻节段退变发生的理论基础。

[Objective] To analyze the effects of PEEK （polyethererketone） rods pedicle screw system on the intradiscal pressure of adjacent segments by biomechanical tests. [Methods] Ten lumbar spine （L3~L6） specimens of fresh sheep cadavers aged 12 to 24 months were used. Each specimen was treated with different fixation methods in turn. According to the treatment applied, the specimen was divided into the following 5 test groups, including no instrumentation （the intact group）, titanium rod for single segment fixation （the TS group） ; PEEK rod for single segment fixation （ the PS group） ; PEEK rod for double segments hybridization group （the PD group） and titanium rod for double segments fixation group （the TD group）. Using MTS （Multi-degree of spine movement simulation test system）, each specimen was subjected to 6 movements with the axial pressure of 50N and torque of 3 N.m, such as flexion, extension, left and right bending, left and right torsion. The intradiscal pressure （IDP） was measured with a needle sensor for each movement. [Results] The intradiscal pressure of the upper adjacent segment in the PS group and the TS group were statistically higher than that of the intact group （P〈0.05）. In addition, the intradiscal pressure in the upper adjacent segment in PS group was remarkably lower than that of the TS group （P〈0.05）. Furthermore, the pressure of the transition segment in the PD group was also considerably lower than that of the upper adjacent segment in the TS group （P〈 0.05） . Under the given load and torque, L3/4 intervertebral pressure in titanium rod fixation with L4/5 fusion was normally increased in flexion, extension, lateral bending and axial rotation compared with the intact condition, but the results were reversed after the hybrid surgery with PEEK rods. [Conclusions] Compared with rigid fixation system, the PEEK rods pedicle screw system will significantly reduce the intradiscal pressure of the adjacent intervertebral segment, which might be the theoretical foundation for reducing the incidence of adjacent segment degeneration.