| [Background]Because of the lumbosacral vertebrae’s special position and physiological function in the structure of human body, the lower lumbar degenerative diseases are very common in clinic. The fusion is one of the most common operation methods to treat intervertebral disc degeneration and lumbar instability. Now, the surgery for L5-S1interbody fusion is very common in clinic. The mainly methods of L5-S1fusion are posterior lumbar interbody fusion (PLIF), anterior lumbar interbody fusion (ALIF) and the axial lumbosacral interbody fusion (AxiaLIF) at present. The PLIF operation, using pedicle screw to fix, has a good effect on vertebral fusion and has become the golden standard for the traditional fusion operation. But it has a great influence on the physiological function of the spine, and carries a risk of nerve toot or dural sac damage, and may also cause a sacroiliac joint degeneration. The ALIF operation, which should remove part of the anterior longitudinal ligament and the anterior portion of the annulus, can lead to the loss of the structure’s tension, spinal instability, failure of fusion, and has a high risk to damage the important vessels or nerves. The rate to turn laparotomy is from4%to24%, and the rate of retrograde ejaculation after operation is from6%to45%.In the study of L5-S1fusion surgery, the scholars were looking for safer, more effective and minimally invasive surgical procedures, L5-S1axial lumbosacral interbody fusion (AxiaLIF) thus came into being. The AxiaLIF was first proposed by Cragg in2004. The AxiaLIF operation using an axial screw to make the L5and S1vertebrae body fusion through the presacral space, which preservation of muscles, ligaments and annulus, in theory, may have a better stability and more obvious advantages on biomechanics than traditional posterior and anterior lumbar interbody fusions.Erkan et al tested the biomechanical properties of L5-S1AxiaLIF, and proved that it conformed to the biomechanical requirements, and more stability combined with posterior screws fixation or facet screws fixation. Aryan and other foreign researchers had completed hundreds of chinical surgery, unanimously affirmed its clinical effect. They also pointed out that if the axial screw’s placement is wrong, the axis of the screw is not conformed to the biomechanical requirements, it may result in failed fusion or pseudarthrosis.In domestic studies, Rong Linin et al completed12cases of L5-S1AxiaLIF, and affirmed its advantages of less trauma, fewer complications and faster recovery. After the follow-up of six months, one case was completed fusion, ten cases were partial fusion and one case had not been integrated. The not ideal fusion of L5-S1AxiaLIF in this report may be relevant with the deviation of fixed axis. As Chinese lumbosacral vertebral structure has some different from American and European, Lv Honglin et al pointed out that the operation had its own characteristics in china:different incision and screw’s entrance. He confirmed that the axial lumbosacral interbody fusion is suitable for Chinese by image data’s analysis, but there is no evidence to testify that whether the anatomical parameters of this operation is in the safety range of presacral channels. Li Xiangming et al considered that the "coronal safe zone" is the distance between the two anterior sacral holes, and the "sagittal safe zone" is the length of the pelvic splanchnic nerve. This study will use the three-dimensional reconstruction technique to measure the relevant data of new surgery which suitable for Chinese theoretically, and to verify its feasibility. Meanwhile, according to the theory of three columns, we modify the approach of the new surgery and measure the relevant data to verify its feasibility.Finite element methods are increasingly used in clinical trials. Compared with the specimens’ study, the FEMs have unique advantages in substitutability, repeatability and controllability, etc., and also could reflect the changes of internal stress. In this study, we will establish the three-dimensional finite element model of lower lumbar and pelvis, which is made up of L4and L5, sacrum, coccyx and both sides of innominatum. Then establish the AxiaLIF finite element models with two different roads of axial screw. Simulating, measuring and comparing the biomechanical data of the two models on the four conditions of flexion, extension lateral bending and rotation. Our purpose is to provide biomechanical basis for the promotion and development of the new surgical procedure.Relevant anatomical measurements of the L5-S1axial lumbosacral interbody fusion based on3D reconstruction technology[Objective]To examine the relevant anatomy data of the presacral approach for axial lumbosacral interbody fusion and to explore the suitable surgical pathway for Chinese adult, provide a basis for the promotion of this operation.[Methods] The data of spiral CT scan images were imported into the Mimics10.01software in Dicom format, and the sacral vertebrae3D geometric mesh model was obtained after3D treatment. Finally, the Geomagic studio12.0was used to simply optimize the3D model after imported in the STL format, measure the relevant data and statistically analyze.[Results]In the AxiaLIF surgery which use the coccygeal tip to be the incision and put the axial screw on the axle of lumbosacral vertebral bodies, the distance between the coccygeal tip and the entrance of the nail was found to be (101.7±9.5)mm and (100.2±9.0)mm in Chinese males and females respectively(P>0.05). In the AxiaLIF surgery which use the coccygeal incisures to be the incision and put the axial screw on the middle column of lumbosacral vertebral, the distance between the coccygeal incisures and the entrance of the nail was found to be (82.4±9.5)mm and (83.1±10.6)mm in Chinese males and females respectively(P>0.05). In the AxiaLIF with two different surgical pathway, the vertical distance between needle and S3-4, are (24.4±5.3)mm and (14.5±2.8)mm respectively in men (P<0.05), and are (27.0±5.6)mm and (17.0±3.8)mm respectively in women (P<0.05). There are significant statistical different between the data of male and female groups.[Conclusion]There is high risk on the AxiaLIF which use the coccygeal tip to be the incision. The new AxiaLIF surgery, which use the coccygeal incisures to be the incision and put the axial screw on the middle column of lumbosacral vertebrae, is in the safety range of the presacral space, and needs further verified by biomechanical study.Establishment and biomechanical analysis of normal adult male finite element model of lower lumbar and pelvis[Objective]Establish a complete finite element model of the lower lumbar and pelvis, and provide a basis for subsequent lumbosacral finite element analysis of clinical surgery.[Methods]Obtain the lower lumbar and pelvis CT images through CT scan, and use Mimics10.0to reconstruct the3D model, optimize through Geomagic Studio12.0, establish the finite element model through HaperMesh and Ansys11.0, and verify the model’s effectiveness. In this model,500N of axial preload was used to simulate normal circumstance when standing, and using flexion of12Nm, extension of5Nm, left lateral bending of7.5Nm and right rotation of7.5Nm, and biomechanical analyzing the whole model and the part of L5-S1.[Results](1) Under the condition of flexion, the maximum displacement of the model is6.30mm, which occurs on the forepart of L4vertebral body; the maximum von Mises stress is7.74Mpa, which occurs on the cortex of sacrum; the maximum displacement of L5-S1intervertebral disc is3.76mm, which occurs on the forepart of the disc. (2) Under the condition of extension, the maximum displacement of the model is2.35mm, which occurs on the posterior of L4vertebra; the maximum von Mises stress is6.28Mpa, which occurs on the cortex of sacrum; the maximum displacement of L5-S1intervertebral disc is2.13mm, which occurs on the forepart of the disc.(3) Under the condition of right lateral bending, the maximum displacement of the model is4.04mm, which occurs on the right part of L4vertebral body; the maximum von Mises stress is6.26Mpa, which occurs on the cortex of sacrum; the maximum displacement of L5-S1intervertebral disc is2.72mm, which occurs on the right side of the disc.(4) Under the condition of left rotation, the maximum displacement of the model is4.05mm, which occurs on the forepart of L4vertebral body; the maximum von Mises stress is6.10Mpa, which occurs on the cortex of sacrum; the maximum displacement of L5-S1intervertebral disc is2.75mm, which occurs on the forepart of the disc.[Conclusion]The biomechanical data of the finite element model of the lower lumbar and pelvis are similar to previous studies on various conditions, and this model is accurate and efficient, and can provide the foundation of three-dimensional finite element models for further clinical studies.Biomechanical comparison of axial lumbosacral interbody fusion with two different screw axes by finite element analysis[Objective]Using three-dimensional finite element method to evaluate the biomechanical properties of the L5-S1axial presacral lumbar interbody fusion with two different screw axes, and provide biomechanical basis for the choice of clinical surgery.[Methods]Two AxiaLIF finite element model are established respectively, one use the axis of the lumbosacral vertebral bodies (anterior column) to be the screw’s axis (Model A), and the other one use the midline of the back of the lumbosacral vertebral bodies (middle column) to be the screw’s axis (Model B).500N of axial preload was used to simulate normal circumstance when standing, and respectively load flexion of12Nm, extension of5Nm, left lateral bending of7.5Nm and right rotation of7.5Nm, analyzing and comparing the biomechanical properties about the two AxiaLIF finite element models and the intact model.[Results](1) Under the condition of flexion, the maximum von Mises stress of screw is70.26Mpa and52.30Mpa respectively in the model A and B, the data of model A is34.4%larger than that in model B. Under the condition of extension, the maximum von Mises stress of screw is24.09Mpa and17.69Mpa respectively in the model A and B, the data of model A is36.2%larger than that in model B. Under the condition of right lateral bending, the maximum von Mises stress of screw is66.99Mpa and35.99Mpa respectively in the model A and B, the data of model A is86.1%larger than that in model B. Under the condition of left rotation, the maximum von Mises stress of screw is43.55Mpa and40.75Mpa respectively in the model A and B, the data of model A is6.9%larger than that in model B.(2) Under the condition of flexion, the maximum von Mises stress of bone models is8.64Mpa,8.37Mpa and7.74Mpa respectively in the model A, B and the intact model. Under the condition of extension, the maximum von Mises stress of bone models is6.64Mpa,7.40Mpa and6.28Mpa respectively in the model A, B and the intact model. Under the condition of right lateral bending, the maximum von Mises stress of bone models is7.58Mpa,10.18Mpa and6.26Mpa respectively in the model A, B and the intact model. Under the condition of left rotation, the maximum von Mises stress of bone models is9.33Mpa,10.71Mpa and6.10Mpa respectively in the model A, B and the intact model.(3) Under the condition of flexion, the maximum displacement of the whole model is5.24mm,5.47mm and6.30mm respectively in the model A, B and the intact model. Under the condition of extension, the maximum displacement of the whole model is2.15mm,2.13mm and2.35mm respectively in the model A, B and the intact model. Under the condition of right lateral bending, the maximum displacement of the whole model is3.32mm,3.52mm and4.04mm respectively in the model A, B and the intact model. Under the condition of left rotation, the maximum displacement of the whole model is3.36mm,3.56mm and4.05mm respectively in the model A, B and the intact model.(4) Under the condition of flexion, the maximum displacement of the L5-S1intervertebral disc is3.24mm,3.33mm and3.76mm respectively in the model A, B and the intact model. Under the condition of extension, the maximum displacement of the L5-S1intervertebral disc is1.89mm,1.94mm and2.13mm respectively in the model A, B and the intact model. Under the condition of right lateral bending, the maximum displacement of the L5-S1intervertebral disc is2.40mm,2.45mm and2.72mm respectively in the model A, B and the intact model. Under the condition of left rotation, the maximum displacement of the L5-S1intervertebral disc is2.39mm,2.46mm and2.75mm respectively in the model A, B and the intact model.[Conclusion]For the L5-S1AxiaLIF surgery, there are certain biomechanical advantages when the screw is held in the middle column than in the anterior column. |
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