| Objective: To analyze the influence of different range and location of foramen formation on the biomechanics.of lumbar spine by three-dimensional finite element analysis.Methods: From October to December 2018,10 healthy adults,6 males and 4 females,aged from 24 to 36,with an average age of 28.5 years,were selected.Spinal diseases were excluded.Thin slice CT scan of lumbar spine was performed to obtain CT parameters of lumbar spine.The data were processed by the medical image analysis software mimics19.0,and the bone and soft tissue were distinguished by adjusting the threshold value.Finally,the preliminary three-dimensional finite element model of L4 and L5 vertebrae was obtained.With the help of the reverse engineering software Geomagic studio 2013,the cavity was filled and the model was faired,the cortical cancellous bone was generated,and finally the fitting surfaces of each model were obtained.In the Mapping Software Solidworks 2017,the model was assembled to generate the complete model M0,and then the model M1,M2,m3,M4,M5 were obtained by performing apical,medial 1 /4,2 / 4,3 / 4,and 4 / 4 hierarchical resection of the left superior process of L5 under the application of posterior lumbar spine endoscopy,and the lumbar intervertebral disc model including nucleus pulposus,annulus fibrosus and endplate was constructed.In the finite element analysis software ansys17.0,the important ligaments of spine are simulated by springs,and reasonable unit types and material properties are given.Then,appropriate load parameters are given to simulate the normal lumbar spine to carry out activities such as forward flexion,backward extension,left and right lateral flexion and left and right rotation.The pictures of the maximum ROM of the lumbar spine under various loads of the models with different resection ranges areintercepted,and the screenshots are successively imported into a Dobe Photoshop software to measure the maximum activity.At the same time,the stress distribution map and the maximum value of L4 / 5 disc upper surface were obtained.Then the statistical data were imported into SPSS17.0 software for analysis,and the resected models were compared with the unresected group M0.The analysis of variance was used for the comparison between groups,and SNK test was used for the comparison between the two groups.Results: 1)The three-dimensional finite model of L4-5segment established in this study was effective;2)compared with M0,ROM in the resected tip group(M1)was statistically significant(all P < 0.05),M2 in the resected medial quarter group(M2)was statistically significant(all P < 0.05),m3 in the resected medial quarter group(M3)was statistically significant(all P < 0.05),the difference of right side bending load was statistically significant(all P < 0.05),three quarters of resection group(M4)was statistically significant(all P < 0.05)in forward bending,backward extension,left and right side bending load,and the difference of all resection group(M5)was statistically significant(all P < 0.05)in forward bending,backward extension,left and right side bending and right rotation load;3)L4 / 5intervertebral disc should be compared with M0 of unresected group the differences of M1,M2,m3,M4 and M5 were statistically significant(P < 0.05).Conclusion: 1)In the process of foramen formation,the removal of the tip or the medial quarter of the unilateral single segment of the upper articular process of the lumbar will affect the stability of the lumbar spine,and increase the maximum value of the stress of the intervertebral disc during the activities of the lumbar spine.When the removal of one-half or more,it will significantly damage the stability of the lumbar spine,increase the maximum value of the stress of the intervertebral disc during the activities of the lumbar spine,and significantly damage the biomechanics of the lumbar spine.2)In order to avoid damaging the normal biomechanics of the lumbar spine,the upper articular process should be protected as much as possible during the whole spinal endoscopic foraminal reconstruction. |
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