Finite Element Analysis Of The Effect Of Different Internal Fixation Methods On Pedicle Screw And Upper Disc Stress In MIS-TLIF Operation

Objective: Based on the MIS-TLIF operation,the three-dimensional finite element models of the lumbar L4-S1 segment unilateral fusion fixation group and bilateral fusion fixation group were established,and the biomechanical characteristics of the adjacent upper vertebral disc and internal fixation screws in different working conditions were analyzed by using the finite element model.Methods and procedures: Male volunteers with a height of 1.75 m and a weight of 65 Kg were selected to meet the requirements.The patients did not have obvious diseases such as osteoporosis,trauma and infection.The image file of L4-S1 of the volunteer was obtained by CT scanning technology.Finite element analysis software Mimics,Geomagic Studio,Pro/E and Hypermesh1.6were used to establish the finite element model of L4-S1,and ABAQUS software was used for mechanical analysis.Among them,L5-S1 was the operative segment of MIS-TLIF,and L4-L5 was the postoperative upper adjacent segment.The model was used to investigate the influence of the stress changes of single and bilateral pedicle screws and upper interv ertebral disc on the adjacent vertebrae under different motion states.Results: 1.To establish the study model in the simulation test,the stress point of model 500 N,1000N,1500 N and 2000 N pressure load,get the overall displacement of the model data,compared to previous in vitro test data,the load-displacement curve of this experiment results have a tendency of in vitro test results,with the change of data suggests that the integrity of the model data.2.T test was performed on the two groups of data.Compared to X1 P<0.05,under any working conditions,the peak stress of intervertebral disc with unilateral screw placement was lower than that with bilateral screw placement,and the result showed a statistically significant difference.3.T test was performed on the two groups of data.Compared with X1 P>0.05.The peak values of unilateral screw fixation were similar to those of bilateral screw fixation group under different working conditions,and there was no significant statistical difference between the two groups.Conclusions: 1.After unilateral MIS-TLIF surgery at L5-S1,due to the retention of the normal spinal structure on one side,the stress of the adjacent segments of the model of unilateral internal fixation was less than that of the bilateral model under various working conditions.From the influence of the stress of the adjacent segments on ASD,unilateral MIS-TLIF surgery can prevent and delay the occurrence of ASD to a certain extent.2.Both of the two internal fixation methods can maintain the stability of the spine after surgery.Unilateral internal fixation reduces the risk of ASD by reducing the range of motion of the ASD,and unilateral MIS-TLIF is of positive significance in the control of long-term surgical complications for patients with suitable indications.