全内镜下腰椎板开窗减压有限元模拟建模及生物力学变化

A finite element model of full endoscope lumbar fenestration and biomechanical characteristics

背景:全内镜下减压有效治疗腰椎管狭窄症为突破性前沿技术,相对于开放手术具有创伤小、操作可控、并发症少的特点,但其有限元力学分析鲜有报道。目的:建立全内镜下腰椎椎板开窗有限元模型并探讨减压范围及髓核摘除对腰椎活动度及椎间盘应力分布的影响。方法:采集1例L4-5节段腰椎管狭窄症患者的CT平扫数据,导入Mimics 20.0软件中,建立退变腰椎L4-5节段腰椎管狭窄有限元模型M。将模型M导入3-matic中进行手术模拟,分别为单侧小关节1/2切除及椎间盘1/4切除模型M1、双侧关节突1/2及椎间盘1/2切除模型M2、单侧关节突切除及椎间盘1/4切除模型M3。在ANSYS软件中对4种模型进行同等纯力偶矩的前屈、后伸、左侧弯、右侧弯、左旋转、右旋转6种工况活动及椎间盘同等载荷的力学对比分析。结果与结论:(1)与脊柱M模型比较,M1模型在6种工况下活动度相近,但M2和M3的活动度较M模型明显增大,特别是在左、右侧屈和前屈、后伸工况下,为M模型整体活动度的130%-200%;(2)在椎间盘应力方面,M1模型在椎间盘后区、中区、右区各工况下等效应力的上升趋势不明显,在椎间盘左区、前区的等效应力有所增加,最大增加63%,但没有出现较大的应力集中情况;而M2和M3模型,各区域椎间盘等效应力均出现较大程度上升趋势;(3)提示全内镜视下微创手术对不同类型腰椎管狭窄症减压手术精准可控,关节突关节切除及髓核摘除1/2以内对相应节段的生物力学稳定性影响较小,证实腰椎板开窗有限元模拟建模成功可靠,可为后续腰椎手术生物力学研究提供重要方法和依据。

BACKGROUND: The effective treatment of lumbar spinal stenosis with total endoscopic decompression is a breakthrough frontier technology. Compared with open surgery, it has the characteristics of fewer traumas, controllable operation, and fewer complications, but it reported less in finite element biomechanics. OBJECTIVE: To establish a finite element model of full endoscope lumbar fenestration and to investigate the effects of decompression range and nucleus pulposus removal on lumbar range of motion and stress distribution of disc. METHODS: CT scan data of a case of L4-5 segmental lumbar spinal stenosis were collected and imported in Mimics 20.0 software. A finite element model M of L4-5 lumbar spinal stenosis in degenerative lumbar spine was established. The model M was imported into 3-matic for surgical simulation, i.e., unilateral disc resection of the small joints 1/2 and 1/4 model M1, bilateral joints 1/2 and 1/2 resection of intervertebral disc model M2, and unilateral disc and articular process of 1/4 model M3. In the ANSYS software, the mechanical comparative analysis was conducted in four kinds of models under six working conditions of the same pure couple moment, including forward bending, backward extension, left bending, right bending, left rotation and right rotation, and the same load of the intervertebral disc. RESULTS AND CONCLUSION:(1) Compared with the spinal M model, the range of motion of M1 model was similar under six working conditions, but the range of motion of M2 and M3 was significantly increased than that of M, especially under the left/right flexion and forward/backward flexion working conditions, which was 130%-200% of the overall activity of M model.(2) In terms of the stress of intervertebral disc, M1 model showed no obvious upward trend of the effect force in the posterior region, central region and right region of intervertebral disc under various working conditions. The equivalent stress in the left region and front region of intervertebral disc increased to a maximum of 63%, but there was no significant stress concentration. In the M2 and M3 models, the equivalent stress of intervertebral discs in all regions showed a significant increased trend.(3) Endoscopic minimally invasive surgery is accurate and controllable for different types of lumbar spinal stenosis decompression surgery. The resection of facet joints and the removal of nucleus pulposus by less than 1/2 have little influence on the biomechanical stability of the corresponding segments. The successful and reliable finite element modeling of lumbar lamina fenestration can provide an important method and basis for the follow-up biomechanical study of lumbar surgery.