不同的棘突间撑开高度对置入节段椎间盘压力分布及关节突关节应力影响的体外生物力学实验研究

目的测量棘突间不同的撑开程度情况下节段椎间盘负荷分布及关节突关节应力情况,以指导其使用。方法 6具腰椎标本,测量SMIPD置入前后椎间盘及关节突关节的受力,分为7组:①空白组,②～⑦SMIPD支撑组,每组间隔2 mm。结果高度10 mm对置入节段椎间盘及关节突关节的压力分布无显著性影响;12 mm过伸时分担46%的椎间盘后纤维环负荷,降低关节突关节压力;14 mm降低后环及关节突关节负荷,但增大前环负荷;16～20 mm后环及关节突关节负荷显著降低,前环负荷增大。结论支撑高度等于或略大于中立位棘突间高度的IPD可分担椎间盘后环及关节突关节负荷并使椎间盘应力更均匀分布;但支撑高度过大会明显增大前环的负荷,如果用于NIC患者的椎间孔撑开,可能会加快椎间盘的退变。

Effects of a new shape-memory alloy interspinous process device on intervertebral disc and zygapophyseal joints pressures distribution in vitro

Objective To quantify lumbar intervertebral disc pressure distribution and zygapophyseal joints pressure with different distraction degrees of interspinous process by using a new shape-memory interspinous process stabilization device(SMIPD) for optimizing the usage of the implant.Methods Six cadaver lumbar specimens for measuring the disc load and zygapophyseal joints pressure before and after SMIPD were implanted.The implants with different spacer height were divided into seven groups.Group one was blank group while group two to seven were SMIPD groups with height difference of 2 mm between two groups.Results The implant with 10 mm spacer height did not significantly share the disc load or change the zygapophyseal joints pressure.The 12 mm implant could share the posterior annulus load,and meanwhile decrease the zygapophyseal joints pressure only in extension.The 14 mm implant could share the load of posterior annulus and nucleus,decrease the zygapophyseal joints pressure in extension and neutral position but slightly increase the anterior annulus’ load.Though the 16～20 mm implants could decrease the posterior annulus’ load and the zygapophyseal joints pressure significantly,the anterior annulus’ load was increased.Conclusion If the spacer height is equal to or slightly higher than the neutral distance of interspinous process,the implant may lead to an optimized biomechanical change to share the disc load and decrease the zygapophyseal joints pressure.However,if the spacer is too high,it will lead to an over-increasing load of anterior annulus and if it is used to distract the intervertebral foramina of the patients with NIC,it may accelerate disc degeneration.