Department of Orthopaedics, University of Utah, 590 Wakara Way, Salt Lake City, UT 84108, USA.
Department of Biomedical Engineering, University of Utah, 36 S. Wasatch Drive, SMBB 3100, Salt Lake City, UT 84112, USA; Scientific Computing and Imaging Institute, University of Utah, 72 South Central Campus Drive, Rm. 3750, Salt Lake City, UT 84112, USA.
Spine J. 2021 Jan;21(1):150-159. doi: 10.1016/j.spinee.2020.07.016. Epub 2020 Aug 5.
Previous studies have analyzed the effect of laminectomy on intervertebral disc (IVD), facet-joint-forces (FJF), and range of motion (ROM), while only two have specifically reported stresses at the pars interarticularis (PI) with posterior element resection. These studies have been performed utilizing a single subject, questioning their applications to a broader population.
We investigate the effect of graded PI resection in a three-dimensional manner on PI stress to provide surgical guidelines for avoidance of iatrogenic instability following lumbar laminectomy. Additionally, quantified FJF and IVD stresses can provide further insight into the development of adjacent segment disease.
Biomechanical finite element (FE) method investigation of the lumbar spine.
FE models of the lumbar spine of three subjects were created using the open-source finite element software, FEBio. Single-level laminectomy, two-level laminectomy, and ventral-to-dorsal PI resection simulations were performed with varying degrees of PI resection from 0% to 75% of the native PI. These models were taken through cardinal ROM under standard loading conditions and PI stresses, FJF, IVD stresses, and ROM were analyzed.
The three types of laminectomy simulated in this study showed a nonlinear increase in PI stress with increased bone resection. Axial rotation generated the most stress at the PI followed by flexion, extension and lateral bending. At 75% bone resection all three types of laminectomy produced PI stresses that were near the ultimate strength of human cortical bone during axial rotation. FJF decreased with increased bone resection for the three laminectomies simulated. This was most notable in axial rotation followed by extension and lateral bending. IVD stresses varied greatly between the nonsurgical models and likewise the effect of laminectomy on IVD stresses varied between subjects. ROM was mostly unaffected by the laminectomies performed in this study.
Regarding the risk of iatrogenic spondylolisthesis, the combined results are sufficient evidence to suggest surgeons should be particularly cautious when PI resection exceeds 50% bone resection for all laminectomies included in this study. Lastly, the effects seen in FJF and IVD stresses indicate the degree to which the remainder of the spine must experience compensatory biomechanical changes as a result of the surgical intervention.
先前的研究分析了椎板切除术对椎间盘（IVD）、小关节面力（FJF）和运动范围（ROM）的影响，只有两项研究专门报告了后路切除后关节突关节的峡部（PI）的应力。这些研究都是针对单个对象进行的，因此其结果可能不适用于更广泛的人群。
我们以三维方式研究 PI 切除分级对 PI 应力的影响，为避免腰椎椎板切除术后医源性不稳定提供手术指导。此外，量化的 FJF 和 IVD 应力可以进一步了解相邻节段疾病的发展。
腰椎的生物力学有限元（FE）方法研究。
使用开源有限元软件 FEBio 创建了三个对象的腰椎 FE 模型。进行了单节段椎板切除术、双节段椎板切除术和腹侧至背侧 PI 切除模拟，PI 切除程度从原生 PI 的 0%到 75%不等。这些模型在标准加载条件下通过主要 ROM 进行了分析，并分析了 PI 应力、FJF、IVD 应力和 ROM。
本研究模拟的三种椎板切除术均显示 PI 应力随骨切除量的增加而呈非线性增加。轴向旋转在 PI 处产生最大的应力，其次是屈伸、伸展和侧屈。在 75%骨切除时，三种类型的椎板切除术在轴向旋转时产生的 PI 应力都接近人类皮质骨的极限强度。随着骨切除量的增加，三种模拟的椎板切除术的 FJF 均减少。轴向旋转后，伸展和侧屈更为明显。IVD 应力在非手术模型之间差异很大，椎板切除术对 IVD 应力的影响也因个体而异。ROM 受本研究中进行的椎板切除术的影响不大。
就医源性脊椎滑脱的风险而言，综合结果足以表明，对于本研究中包含的所有椎板切除术，当 PI 切除超过 50%的骨切除时，外科医生应特别小心。最后，FJF 和 IVD 应力的变化表明，由于手术干预，脊柱的其余部分必须经历多大程度的代偿性生物力学变化。
