Finite element analysis of thumb thrust in lumbar fixed-point rotation manipulation / 中国组织工程研究

ABSTRACT

BACKGROUND:Lumbar fixed-point rotation operation needs collaborative operation of the doctor's hands,and outputs rotation and thumb thrust.Lumbar disc herniation can be treated through disc displacement and adjusting stress distribution.However,the mechanical effects of thumb thrust and the biomechanical effects of loading direction on manipulative effects remain unclear. OBJECTIVE:To compare the biomechanical difference of lumbar fixed-point rotation manipulation for treating lumbar disc herniation under different thrust directions. METHODS:The L3-5 normal three-dimensional finite element model was constructed and validity was verified.According to the intervertebral disc degeneration Pfirrmann grade,intervertebral disc degeneration was simulated by modifying the L4/5 intervertebral space height,the volume of the nucleus pulposus,as well as the material parameters of the annulus fibrosus,nucleus pulposus,and ligament.Finally,the pathological model of L4/5 moderate disc degeneration with left para-central herniation was constructed,and then the pathological models were used as research objects.Simulation technique:spinning to the right;taking the condition on changing the direction of the thumb thrust to establish three modes of operation(M1:thumb push to the left;M2:thumb push to the right;M3:no thrust push).The protrusion displacement and the disc stress,and the stress and strain of the facet joint cartilage were compared in the three operating modes. RESULTS AND CONCLUSION:(1)Maximum displacement value of L4/5 disc herniation:displacement was 2.672 3 mm for M1,1.156 1 mm for M2,1.826 4 mm for M3,M1＞M3＞M2.(2)The maximum Von Mises stress of L4/5 discs was 1.846 7 MPa for M1,0.419 0 MPa for M2,and 1.257 9 MPa for M3,M1＞M3＞M2.(3)L4/5 bilateral small cartilage produced different degrees of contact stress changes:It was 0.485 5 MPa for M1,0.026 7 MPa for M2,and 0.441 4 MPa for M3,M1＞M3＞M2.Right cartilage contact force was 0.000 5 MPa for M1,0.025 9 MPa for M2,and 0.001 3 MPa for M3,M2＞M3＞M1;the left greater than the right,M1 had the highest value;cartilage strain was consistent with contact stress changes.(4)Different operation modes will have some biomechanical influences on the diseased intervertebral disc and accessory structure.The M1 operation mode can maximize the displacement of protrusion,disc stress and left joint cartilage contact,which can better promote disc displacement,balance stress distribution and reduce facet joint disorder,so the operation is better.