# Spinal Biomechanical Modelling in the Process of Lumbar Intervertebral Disc Herniation in Middle-Aged and Elderly

Authors: Xinyu Zhang; Zhe Zhao; Chunlei Niu; Zengbiao Ma; Jianlei Hou; Guanjun Wang; Miao Tang
Journal: Journal of Healthcare Engineering
 (2021)

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## Abstract

Lumbar disc herniation is one of the common clinical diseases of the lower lumbar spine in orthopedics. The purpose is to remove the herniated disc nucleus pulposus tissue, remove the compressed part of the disease, and relieve symptoms, such as nerve pain. In the past, biomechanics research mostly relied on in vitro measurements, but the complicated internal environment of the human body prevented us from further measurement and research. However, with the development of computer technology, the use of computer CT scanning, software three-dimensional reconstruction, and displacement study three-dimensional spine biomechanics method makes the research of biomechanics into in vitro simulation stage and has gradually become the focus of current research. The postoperative biomechanics was simulated and the comparison model was established at the same time. At the same time, we combined the clinical follow-up data and studied the clinical data for the treatment of postoperative recurrence of lumbar disc herniation. We compared and analyzed the initial operation method and the experimental results and obtained the prevention of recurrence. The results showed that when one inferior articular process was removed, the lumbar spine appeared unstable to rotate to the opposite side; when one inferior articular process was completely removed, the movement of the lumbar spine in all directions was unstable. Better research on the biomechanical properties of the spine will help the diagnosis and treatment of clinical lumbar disc herniation. Therefore, when performing posterior lumbar spine surgery, not only should the exposure of the surgical field and thorough decompression be considered, but also the biomechanical properties of the lumbar spine should be comprehensively evaluated.


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## Body

## 1. Introduction

Lumbar disc herniation is one of the common clinical lower lumbar diseases in orthopedics. Severe pain and inconvenience not only affect the quality of life of the patient, but also bring a huge burden to the family and society. The most fundamental reason for this symptom is the disease of the intervertebral disc. After degeneration, the nucleus pulposus is degenerated and frees the rear dural sac, nerve roots, and other tissues [1]. With the development of computer technology, the use of computer CT scanning, three-dimensional reconstruction, spine biomechanics segmentation and assignment analysis, mechanical loading, stress analysis, and displacement study of three-dimensional spine biomechanics methods makes the research of biomechanics enter the stage of in vitro simulation and gradually become current research hotspots [2]. Spinal biomechanics method, also known as spine biomechanical analysis, is a commonly used and efficient numerical calculation method for the design, analysis, and experiment of continuous physical systems in engineering technology. It is suitable for solving problems with complex physical and geometric conditions [3]. The lumbar spine is a heterogeneous structure with irregular shape and complex mechanical characteristics. The traditional method of using specimens will be subject to many restrictions, and the internal stress changes of the intervertebral disc cannot be measured. The platform can give the intervertebral disc superelasticity, bony structure elastoplasticity, and ligament viscoelastic material properties [4]. Mitchell et al. [5] applied the spinal biomechanics analysis method to spinal biomechanics for the first time, but their model had no posterior structure and only involved complete intervertebral joints. Desmoulin et al. [6] made up for this shortcoming in the later stage, adding the posterior structure to the biomechanical model of the lumbar spine and carrying out the biomechanical analysis of the spine. As one of the research methods of biomechanics, spinal biomechanical analysis has been widely used in the biomechanical analysis of various tissues of the spine and has become a research hotspot in lumbar spine biomechanics [7].Biomechanical studies have shown that in the process of applying cyclic loads, not giving the necessary time for the recovery of the intervertebral disc can lead to cumulative damage. Lumbar disc disease causes low back pain and other uncomfortable symptoms, which have seriously affected the quality of life of humans [8]. Spinal biomechanics analysis method is currently the most popular tool for studying spinal biomechanics. The more important point is that it can change the input parameters and analyze the results [9]. At present, a variety of biomechanical models of the lumbar spine have been gradually established, which can fully and accurately reflect the internal stress of the lumbar spine, so that the modeling method based on medical images has been widely used [10, 11]. Wu et al. [12] changed the elastic modulus and Poisson’s ratio to establish L3-L4 degenerative intervertebral discs and applied an axial load of 0.3 MPa, which was compared with the normal intervertebral discs in the data review. Widyasari et al. [13] established the L4-L5 normal spine biomechanical model and the intervertebral disc herniation model, applied loads under five working conditions including flexion, extension, and torsion, and found that the contact force of the facet joints of the herniated disc model was greater than normal model. Suśtersic et al. [14] proved that the load of the facet joints increases and the bearing capacity of the herniated intervertebral disc decreases, which leads to a decrease in the stability of the lumbar spine. Jezek et al. [15] considered the osmotic pressure change characteristics of the intervertebral disc as one of the key considerations when establishing a three-dimensional spine biomechanical model, and the tissue expansion pressure determines part of the osmotic pressure. The stress of the liquid substance in the intervertebral disc increases, but the stress of the solid substance decreases accordingly. The previous research believed that the water was completely pressed out and would not bear the pressure, and the pressure was fully borne by the solid [16–19]. These studies can visually observe the stress and strain characteristics of intervertebral disc degeneration and deepen the understanding of the mechanism of low back pain and lower extremity pain caused by the protrusion of the nucleus pulposus after the rupture of the annulus fibrosus and the pain of the lower limbs and provide necessary supplements to clinical research [20–22]. Wang et al. [23] studied the load transfer mode and stress distribution with the help of a two-dimensional spine biomechanical model. This simplified intervertebral disc degeneration model shows a slight degeneration of the intervertebral disc. Although it fails to explain the changes that occurred early in the process of intervertebral disc degeneration, the study shows the initial stage of the degeneration process [24–27].In order to better solve the existing problems, this article intends to use Magnetic Resonance Imaging (MRI) and CT images for 3D reconstruction and then use the finite element method to analyze the stress and displacement of the spine model. This article simulates various surgical methods for the treatment of lumbar disc herniation, removing the bone and ligament structure at the back of the spine and studying the changes in the stability of the spine under different conditions. After re-sampling, layer-by-layer division, filling, filtering, and smoothing of the images, all layers of images are combined to build a three-dimensional model of the spine. In the project, the young normal spine, the young diseased spine, and the elderly normal spine were modeled separately. Different models have differences in material properties and physical forms. After modeling, the spine biomechanical analysis is performed on the model. After modeling, the same load should be applied to different models to simulate various movements of the spine, and the results obtained should be analyzed. This article discusses which surgical method will simulate spinal instability and provides a certain theoretical basis for the selection of surgical methods. The main analysis process involves the comparison of the stress and displacement of the young normal spine model and the young diseased spine model under the same load and the comparison of the old normal spine model and the young normal spine model under the same load.


## 2. Construction of a Biomechanical Model of the Spine in the Process of Lumbar Disc Herniation in Middle-Aged and Elderly People

### 2.1. The Distribution of Lumbar Disc Herniation

The lumbar intervertebral disc is located between the two lumbar vertebral bodies. It is a very flexible viscoelastic tissue between the vertebral bodies. It forms lumbar motion segments with the surrounding ligaments, muscles, and fascia to maintain the mobility and stability of the lumbar spine. The lumbar intervertebral disc can transfer the load, balance the body, and stabilize the spine. Figure1 shows a schematic diagram of the structure distribution of lumbar disc herniation.Figure 1
Schematic diagram of the structure distribution of lumbar intervertebral disc herniation.However, the main function of the spine also depends on the integrity of the intervertebral disc. The understanding of the stress and strain distribution of the lumbar spine will help the clinical diagnosis and treatment of the lumbar intervertebral disc. Compared with other parts of the spine, the intervertebral disc bears more pressure, which leads to the extremely common lumbar disc herniation.(1)fx=x1,x2,...,xn|n∈R.When the material to be studied is certain, the basic variables of mechanics should include the following: displacement, stress, and strain. The equations established during the research should be universal equations. Therefore, the small voxel is usually used as the research content. The basic variables used in the description of spine biomechanics analysis should include displacement, stress, and strain.(2)ux,y=u¯x,yvx,y=v¯x,y,x,y∈S¯u¯.We study the relationship between various variables when the tiny voxels are subjected to external forces, including the displacement, stress, and strain of the tiny voxels, and construct equations. The equation includes three major categories, namely, balance equation, geometric equation, and physical equation. Among them, the main focus of the balance equation is the force condition, the geometric equation is the embodiment of the deformation of the object:(3)∂u∂x+∂v∂y+∂w∂z=0,σx,y=1E×εx,x−tεy,y.In order to describe the complex geometric characteristics of the object, the material characteristics of the object, and the given force and constraint conditions, variables, equations for description, and the boundary of the object are used. The commonly used three types of equations in spine biomechanics analysis refer to equations that describe the balance between forces, geometric deformation equations, and physical equations that describe material properties. The boundary conditions are divided into two categories, namely, the displacement boundary and the external force boundary.(4)εx,x=∂u∂xεy,y=∂v∂y.εz,z=∂w∂zThe intervertebral disc is composed of cartilaginous endplates (CEP), annulus fibrosus (AF), and nucleus pulposus (NP). Once the intervertebral disc is under abnormal pressure, the permeability of the endplate and cancellous bone will change, which will affect the nutrient supply of the annulus fibrosus, which in turn leads to the degeneration of the intervertebral disc. If the pressure of the lumbar spine is high and concentrated in this area, the annulus fibrosus will rupture due to poor nutrient supply, and then the nucleus pulposus will be separated along the ruptured area, and finally the intervertebral disc will be squeezed out.


### 2.2. Spinal Biomechanical Model

There are three methods for spine biomechanics modeling: geometric modeling, three-dimensional coordinate instrument modeling, and image modeling. Geometric modeling is quick and simple. It is constructed by geometric form and size, which is suitable for objects with relatively regular shapes; 3D coordinate instrument modeling is constructed based on the spatial coordinates of the specimen. Image modeling obtains image data through CT, MRI, etc., which is suitable for the construction of irregular models, and this method is widely used.(5)∂h∂x,∂y,∂z=∂h∂x∂x0...∂h∂x∂y0∂h∂x∂x...0............∂h∂x∂y0...∂h∂x∂x.The initial finite element analysis was used to analyze aircraft structural problems, and later engineers defined it and extended it to large structures. A structure can theoretically be decomposed into many small and discretized regions. These small regions are called finite elements. If an object moves relative to its interior when subjected to an external force, such an object is called a deformed body, which is closely related to the material properties of the deformed body itself.Figure2 shows the spine biomechanical model architecture. The composition of each element is called a unit, and the unit is composed of the nodes that make up the unit. We can use the computer to define the material properties of the element, deal with the nodes of the element, and at the same time constrain and load the nodes, define the boundary conditions, calculate the element equations mathematically, and establish the equations of the object to be solved so that for complex materials, we approximately solve the internal and external structural mechanics problems of objects such as structures.(6)σx,x,σy,y,σz,z⟶εx,y,εy,z,εz,x,p′x−pxpx=∂u/∂xdxdx=∂u∂x.Figure 2
The architecture of the spine biomechanical model.If the deformable body is divided according to the angle of the geometric complexity of the object, it can be divided into two categories: one is the deformable body of simple shape, and the other is the deformable body of arbitrary shape. Arbitrary deformable body is the main research content, mainly studying its variables and equations. The earliest biomechanical model of the spine was a two-dimensional linear model. Later, with the development of computer software and hardware, nonlinear models were developed, and various analysis software versions gradually improved, which further extended the two-dimensional linear model to the three-dimensional nonlinear model.At the same time, the spine biomechanics method itself is no longer a relatively independent study of the mechanical properties of the spine, but cleverly combined with other disciplines and other methods to make the research results more accurate and reliable. Table1 shows the unit properties of the spine biomechanics model. Spine mobility and displacement can be measured in vitro using experimental methods, but internal stress changes can only be measured by mathematical methods such as spine biomechanics, such as stress changes inside the vertebral body, cancellous bone deformation inside the vertebral body, and microfractures. At the same time, spine biomechanics analysis can also evaluate the effectiveness of internal fixation and effectively modify the internal fixation to reduce stress concentration and fatigue.Table 1
Unit attributes of the spine biomechanical model.
Organizational materialDensity (10−6 kg/mm3)Young’s modulus (MPa)Poisson’s ratioPosterior longitudinal ligament1.129.410.41Anterior longitudinal ligament1.2010.910.39Annulus1.325.710.49Cancellous bone1.812920.27Compact bone1.23143200.41However, other details must be described in addition to this, such as symmetrical sliding boundaries and other special situations that often require special descriptions, which cannot be expressed by using units alone. Other methods, such as coupling equations or constraint equations, can be used to establish special connections to make up for the details of the degree of freedom connection that the element cannot express. When performing spine biomechanical analysis on actual problems, sometimes it is necessary to show, although the value of the degree of freedom is unknown, the value of multiple degrees of freedom is equal. Coupling can be used to realize this relationship. There are not only main degrees of freedom but also other degrees of freedom in the concentration of coupled degrees of freedom, and the analysis matrix has only main degrees of freedom. The value of the main degree of freedom can be calculated, and the obtained value can be assigned to other degrees of freedom.


### 2.3. Model Weight Factor Optimization

This article is to directly read the CT image into Simpleware and then use this software to segment and process the image to generate a three-dimensional model of the spine. The biomechanical model of the spine is an abstract representation of the actual object to be studied, which can abstract the nature of the object to be studied. In ANSYS, the model needs to be meshed, and the model is divided into units. The construction process of the spine biomechanics model can be subdivided into the following steps: first, we name the working files and then define the unit type of the model. Here, the properties of all materials must be clarified, and finally the spine biomechanics model is constructed. The following tasks can be done in the processor: we clarify the type of solution this time, set the spinal biomechanics analysis options, apply the load, select the load step, and complete the calculation solution. The steps of loading and solving can also be subdivided. After the spine is strong internally fixed, the stress shielding effect appears, and the damaged front column structure loses the function of bearing the main load. These are the results of stress concentration. We must clarify the analysis type and analysis options, then apply a load on the object to be analyzed, and finally select the load step option and perform the solution calculation.In the 3D view, we can generate a preview, preview the generated three-dimensional model, and export the three-dimensional model after confirming that the model does not need to be modified. Presmoothing can be done according to the default settings of the options, and then the model can be exported. In ScanIP, only the surface of the spine model is meshed, and the interior of the model body is not partitioned. Therefore, after the model exported from ScanIP is imported into ScanFE, the smoothing and meshing must be optimized first. Figure3 shows a fan chart of the degree of freedom of the spine biomechanical model. By setting model smoothing parameters, a smooth, volume meshed three-dimensional model can be obtained. All the degrees of freedom and nodes in the model should appear, and the situation where any node or degree of freedom does not appear should be avoided. If there are degrees of freedom at a node, this node should be connected to other elements with the necessary degrees of freedom. The command can be used to derive a new set of equations from the existing constraint equations. In order to generate a new constraint equation here, a new node number will appear in the existing set of constraint equations, but the coefficients and labels should remain the same as the original ones. It is also necessary to pay attention to the constraint equation: the theory of small rotation is the theoretical basis of the constraint equation. Therefore, when there is a large rotation, the major changes in the degree of freedom should be restricted to avoid unexpected situations.Figure 3
Fan chart of the proportion of degrees of freedom of the spine biomechanical model.Table2 shows the weighting factor distribution of the spine biomechanics model. After completing the spine biomechanics calculations, we need to view the results of the calculations. At this time, a postprocessor is used to view the calculation results. The postprocessing here is to observe and analyze the calculation results, and the results can be used to judge whether the calculation is correct, so this step is also very important. There are two types of postprocessors, one is to view static results, that is, general-purpose processors. Another type of processor is to view the dynamic results, that is, the time postprocessor. For the stability of the internal fixation system, the better the screw implantation, the better, but if it is too deep or even penetrates the cortical bone, it will greatly increase the incidence of complications. It is considered that 80% is more appropriate depth. The former is abbreviated as POST1, to view the results over a certain period of time or the results under a certain frequency. The latter is abbreviated as POST2, and what you view is the result of specifying a certain point, and this result changes dynamically over time. Therefore, it can be seen that the results viewed by the general post-processor are the results at a fixed point in time, but the results viewed by the time history postprocessor are the results that dynamically change with time.Table 2
Weighting factor distribution of spine biomechanics model.
Model indexTissue siteUnit typeNumber of unitsNumber of nodesElastic modulus (MPa)1Cortical bone3D solid11711427115422Cancellous bone3D solid110213057213Fiber tube3D solid3425375.914Ligament3D solid13232731245Endplate2D planar8710411.71


## 2.1. The Distribution of Lumbar Disc Herniation

The lumbar intervertebral disc is located between the two lumbar vertebral bodies. It is a very flexible viscoelastic tissue between the vertebral bodies. It forms lumbar motion segments with the surrounding ligaments, muscles, and fascia to maintain the mobility and stability of the lumbar spine. The lumbar intervertebral disc can transfer the load, balance the body, and stabilize the spine. Figure1 shows a schematic diagram of the structure distribution of lumbar disc herniation.Figure 1
Schematic diagram of the structure distribution of lumbar intervertebral disc herniation.However, the main function of the spine also depends on the integrity of the intervertebral disc. The understanding of the stress and strain distribution of the lumbar spine will help the clinical diagnosis and treatment of the lumbar intervertebral disc. Compared with other parts of the spine, the intervertebral disc bears more pressure, which leads to the extremely common lumbar disc herniation.(1)fx=x1,x2,...,xn|n∈R.When the material to be studied is certain, the basic variables of mechanics should include the following: displacement, stress, and strain. The equations established during the research should be universal equations. Therefore, the small voxel is usually used as the research content. The basic variables used in the description of spine biomechanics analysis should include displacement, stress, and strain.(2)ux,y=u¯x,yvx,y=v¯x,y,x,y∈S¯u¯.We study the relationship between various variables when the tiny voxels are subjected to external forces, including the displacement, stress, and strain of the tiny voxels, and construct equations. The equation includes three major categories, namely, balance equation, geometric equation, and physical equation. Among them, the main focus of the balance equation is the force condition, the geometric equation is the embodiment of the deformation of the object:(3)∂u∂x+∂v∂y+∂w∂z=0,σx,y=1E×εx,x−tεy,y.In order to describe the complex geometric characteristics of the object, the material characteristics of the object, and the given force and constraint conditions, variables, equations for description, and the boundary of the object are used. The commonly used three types of equations in spine biomechanics analysis refer to equations that describe the balance between forces, geometric deformation equations, and physical equations that describe material properties. The boundary conditions are divided into two categories, namely, the displacement boundary and the external force boundary.(4)εx,x=∂u∂xεy,y=∂v∂y.εz,z=∂w∂zThe intervertebral disc is composed of cartilaginous endplates (CEP), annulus fibrosus (AF), and nucleus pulposus (NP). Once the intervertebral disc is under abnormal pressure, the permeability of the endplate and cancellous bone will change, which will affect the nutrient supply of the annulus fibrosus, which in turn leads to the degeneration of the intervertebral disc. If the pressure of the lumbar spine is high and concentrated in this area, the annulus fibrosus will rupture due to poor nutrient supply, and then the nucleus pulposus will be separated along the ruptured area, and finally the intervertebral disc will be squeezed out.


## 2.2. Spinal Biomechanical Model

There are three methods for spine biomechanics modeling: geometric modeling, three-dimensional coordinate instrument modeling, and image modeling. Geometric modeling is quick and simple. It is constructed by geometric form and size, which is suitable for objects with relatively regular shapes; 3D coordinate instrument modeling is constructed based on the spatial coordinates of the specimen. Image modeling obtains image data through CT, MRI, etc., which is suitable for the construction of irregular models, and this method is widely used.(5)∂h∂x,∂y,∂z=∂h∂x∂x0...∂h∂x∂y0∂h∂x∂x...0............∂h∂x∂y0...∂h∂x∂x.The initial finite element analysis was used to analyze aircraft structural problems, and later engineers defined it and extended it to large structures. A structure can theoretically be decomposed into many small and discretized regions. These small regions are called finite elements. If an object moves relative to its interior when subjected to an external force, such an object is called a deformed body, which is closely related to the material properties of the deformed body itself.Figure2 shows the spine biomechanical model architecture. The composition of each element is called a unit, and the unit is composed of the nodes that make up the unit. We can use the computer to define the material properties of the element, deal with the nodes of the element, and at the same time constrain and load the nodes, define the boundary conditions, calculate the element equations mathematically, and establish the equations of the object to be solved so that for complex materials, we approximately solve the internal and external structural mechanics problems of objects such as structures.(6)σx,x,σy,y,σz,z⟶εx,y,εy,z,εz,x,p′x−pxpx=∂u/∂xdxdx=∂u∂x.Figure 2
The architecture of the spine biomechanical model.If the deformable body is divided according to the angle of the geometric complexity of the object, it can be divided into two categories: one is the deformable body of simple shape, and the other is the deformable body of arbitrary shape. Arbitrary deformable body is the main research content, mainly studying its variables and equations. The earliest biomechanical model of the spine was a two-dimensional linear model. Later, with the development of computer software and hardware, nonlinear models were developed, and various analysis software versions gradually improved, which further extended the two-dimensional linear model to the three-dimensional nonlinear model.At the same time, the spine biomechanics method itself is no longer a relatively independent study of the mechanical properties of the spine, but cleverly combined with other disciplines and other methods to make the research results more accurate and reliable. Table1 shows the unit properties of the spine biomechanics model. Spine mobility and displacement can be measured in vitro using experimental methods, but internal stress changes can only be measured by mathematical methods such as spine biomechanics, such as stress changes inside the vertebral body, cancellous bone deformation inside the vertebral body, and microfractures. At the same time, spine biomechanics analysis can also evaluate the effectiveness of internal fixation and effectively modify the internal fixation to reduce stress concentration and fatigue.Table 1
Unit attributes of the spine biomechanical model.
Organizational materialDensity (10−6 kg/mm3)Young’s modulus (MPa)Poisson’s ratioPosterior longitudinal ligament1.129.410.41Anterior longitudinal ligament1.2010.910.39Annulus1.325.710.49Cancellous bone1.812920.27Compact bone1.23143200.41However, other details must be described in addition to this, such as symmetrical sliding boundaries and other special situations that often require special descriptions, which cannot be expressed by using units alone. Other methods, such as coupling equations or constraint equations, can be used to establish special connections to make up for the details of the degree of freedom connection that the element cannot express. When performing spine biomechanical analysis on actual problems, sometimes it is necessary to show, although the value of the degree of freedom is unknown, the value of multiple degrees of freedom is equal. Coupling can be used to realize this relationship. There are not only main degrees of freedom but also other degrees of freedom in the concentration of coupled degrees of freedom, and the analysis matrix has only main degrees of freedom. The value of the main degree of freedom can be calculated, and the obtained value can be assigned to other degrees of freedom.


## 2.3. Model Weight Factor Optimization

This article is to directly read the CT image into Simpleware and then use this software to segment and process the image to generate a three-dimensional model of the spine. The biomechanical model of the spine is an abstract representation of the actual object to be studied, which can abstract the nature of the object to be studied. In ANSYS, the model needs to be meshed, and the model is divided into units. The construction process of the spine biomechanics model can be subdivided into the following steps: first, we name the working files and then define the unit type of the model. Here, the properties of all materials must be clarified, and finally the spine biomechanics model is constructed. The following tasks can be done in the processor: we clarify the type of solution this time, set the spinal biomechanics analysis options, apply the load, select the load step, and complete the calculation solution. The steps of loading and solving can also be subdivided. After the spine is strong internally fixed, the stress shielding effect appears, and the damaged front column structure loses the function of bearing the main load. These are the results of stress concentration. We must clarify the analysis type and analysis options, then apply a load on the object to be analyzed, and finally select the load step option and perform the solution calculation.In the 3D view, we can generate a preview, preview the generated three-dimensional model, and export the three-dimensional model after confirming that the model does not need to be modified. Presmoothing can be done according to the default settings of the options, and then the model can be exported. In ScanIP, only the surface of the spine model is meshed, and the interior of the model body is not partitioned. Therefore, after the model exported from ScanIP is imported into ScanFE, the smoothing and meshing must be optimized first. Figure3 shows a fan chart of the degree of freedom of the spine biomechanical model. By setting model smoothing parameters, a smooth, volume meshed three-dimensional model can be obtained. All the degrees of freedom and nodes in the model should appear, and the situation where any node or degree of freedom does not appear should be avoided. If there are degrees of freedom at a node, this node should be connected to other elements with the necessary degrees of freedom. The command can be used to derive a new set of equations from the existing constraint equations. In order to generate a new constraint equation here, a new node number will appear in the existing set of constraint equations, but the coefficients and labels should remain the same as the original ones. It is also necessary to pay attention to the constraint equation: the theory of small rotation is the theoretical basis of the constraint equation. Therefore, when there is a large rotation, the major changes in the degree of freedom should be restricted to avoid unexpected situations.Figure 3
Fan chart of the proportion of degrees of freedom of the spine biomechanical model.Table2 shows the weighting factor distribution of the spine biomechanics model. After completing the spine biomechanics calculations, we need to view the results of the calculations. At this time, a postprocessor is used to view the calculation results. The postprocessing here is to observe and analyze the calculation results, and the results can be used to judge whether the calculation is correct, so this step is also very important. There are two types of postprocessors, one is to view static results, that is, general-purpose processors. Another type of processor is to view the dynamic results, that is, the time postprocessor. For the stability of the internal fixation system, the better the screw implantation, the better, but if it is too deep or even penetrates the cortical bone, it will greatly increase the incidence of complications. It is considered that 80% is more appropriate depth. The former is abbreviated as POST1, to view the results over a certain period of time or the results under a certain frequency. The latter is abbreviated as POST2, and what you view is the result of specifying a certain point, and this result changes dynamically over time. Therefore, it can be seen that the results viewed by the general post-processor are the results at a fixed point in time, but the results viewed by the time history postprocessor are the results that dynamically change with time.Table 2
Weighting factor distribution of spine biomechanics model.
Model indexTissue siteUnit typeNumber of unitsNumber of nodesElastic modulus (MPa)1Cortical bone3D solid11711427115422Cancellous bone3D solid110213057213Fiber tube3D solid3425375.914Ligament3D solid13232731245Endplate2D planar8710411.71


## 3. Results and Analysis

### 3.1. Data Processing of Lumbar Intervertebral Disc Detection

In this paper, SPSS 13 statistical software is used, and the data obtained are expressed. The comparison of the sample means between each group uses a one-way analysis of variance. We analyze whether there are significant changes in the status of various simulated operations compared with normal spine specimens. The main tool used for data processing is Simpleware software, which consists of three parts. Here, two modules, ScanIP and ScanFE, are mainly used. After the modeling is completed, the material of the spine model is set according to the physical characteristics of the actual human spine so that the model is as close to the actual human spine as possible. Because ANSYS has a very good openness, it can take advantage of this feature of ANSYS to carry out secondary development, modify and expand the functions of ANSYS, and develop a special spine biomechanical analysis tool for the human spine model. Finally, the model is imported into ANSYS, and different loads and constraints are applied to the spine model according to the analysis steps to simulate the movement of the spine. The calculation results of each model are analyzed in the results and experimental conclusions are drawn.The data used in this article are 60 frames of continuous format data obtained by continuous scanning of the human body. The data are read into ScanIP for viewing and processing. First, we adjust the resolution to achieve the purpose of adjusting the accuracy of the model. This step is called resampling. In this project, the imported CT data are trimmed, and data resampled in ScanIP so that only useful data are retained, and the number of grids is reduced. In ScanIP, the part of interest is segmented by observing the different gray values. There are many factors that affect the internal pressure of the intervertebral disc, such as whether the intervertebral disc is originally degenerated, the range of motion of the segment, muscle tension, ligament tension, abdominal pressure, and so on. The bone tissue is easily observed on the CT image, so it is easier to divide the boundary between them. Then, we use the confidence region connection method to fill in the divided regions to obtain plane models of different parts of the fault. Unlike the spine, the characteristics of the intervertebral disc are closer to soft tissue, so it is not very clear on the CT image. We can use all knowledge of medical anatomy to outline the general outline of the intervertebral disc and then fill it. Next, we must perform filtering processing, boundary region processing, threshold segmentation, and other operations on the plane model, and finally generate a three-dimensional spine model based on the multilayer tomographic plane model.Figure4 shows the histograms of the changes in vertebrae expansion and contraction of different specimen numbers. With the increase in the resection of the posterior structure in different surgical methods of the lumbar spine, the range of motion of the lumbar spine specimens in flexion/extension is increasing. From specimen B to specimen C, compared with specimen A, the average increase in flexion range was 3.3%, 5.0%, 9.5%, 16.9%, and 30.2%, respectively. The average increase in extension range was 6.6%, 8.0%, 13.7%, 22.6%, and 32.3%. According to statistical analysis, compared with specimen A, specimens B, C, and D have no significant difference in flexion/extension changes, specimen D has significant differences in flexion/extension, and specimen C has a significant difference in flexion/extension.Figure 4
Histogram of changes in vertebral extension of different specimen numbers.


### 3.2. Simulation of the Biomechanical Model of the Spine

This article is mainly aimed at CT plain scans of normal patients without disease, using Mimics software and ANSYS software to establish a three-dimensional spine biomechanical model of the normal spine, and simulate, stress, load loading, and other conditions on the three-dimensional finite element model of the normal spine. For digital simulation of surgery, etc., we establish a three-dimensional spine biomechanical model after surgery and other different surgical plans and perform stress analysis, and at the same time analyze and compare the data. Sixty-one patients diagnosed with postoperative recurrence of lumbar disc herniation and surgical treatment were selected, and the initial surgical plan for recurrence and the reason for the re-operation were counted. According to the treatment method of re-operation, 50 patients in the observation group were divided into the observation group, and the control group was fixed with posterior approach. There were 50 patients undergoing fusion surgery. Figure5 shows the line comparison chart of the visual simulation score of the spine biomechanics model. Statistics of the blood loss during the second operation, operation time, postoperative score, Visual Analogue Scale (VAS) score, etc., of the two treatment methods were calculated using SPSS 13 to perform statistical analysis. The observation group and the control group had significant differences in intraoperative blood loss and operation time, but there was no significant difference in postoperative score and VAS score.Figure 5
Comparison chart of spine biomechanics model visual simulation score line.The steps of spine biomechanics analysis mainly include preprocessing, loading and solving, and postprocessing. The work that can be completed in the preprocessing includes building the model, setting the properties of the material, applying different loads and boundary conditions, and defining various contact relationships. The establishment of the biomechanical model of the spine and the setting of the material properties have been completed before. Now only the load and boundary conditions of the model and the contact relationship need to be defined, the stress and strain of the lumbar spine can be simulated and simulated. Loads in ANSYS can be divided into two categories: one is boundary conditions, and the other is excitation. The function of ANSYS is to apply different excitations and different boundary conditions to the model to be analyzed for spine biomechanics, and then we perform the analysis to obtain the response. Figure6 shows the linear fitting of the coupling ratio of the model nodes. The maximum stress between the different models increases with the increase of the punch diameter, but all are below the lower limit of the 95% confidence interval of the endplate failure strength, and the difference between the models is not obvious, and the difference is not much from the normal value, so the endplate fracture risk is low. According to the previous introduction, here for the contact relationship, the coupling operation is used to simulate so that the calculation maintains a linear relationship so that the nodes of the contact parts of different materials are set to be the same. In this paper, manual point selection is used to select points between nodes at the same location so that various materials connecting nodes are automatically coupled together.Figure 6
Linear fitting of model node coupling ratio.We use a high-resolution Philips 64-slice CT machine to scan the lower lumbar spine with 140 kV, 200 mA conditions, and 0.9 mm intervals. The scan length is about 84 cm to obtain 1000 pictures in DICOM format. The CD completes the data collection. We use the image import function to select the CD-ROM drive; the system will automatically recognize the DICOM format pictures and sequences in the disc and generate three window pictures including sagittal, coronal, and transverse positions. We select the L4 to be studied on the scanned CT film. By using the method of setting CT threshold on the skeletal plain scan to distinguish between bone and surrounding soft tissues, we use profile line to select StartThresholding option and select Apply option to start rendering, and get the system. The area of the CT threshold range is selected by default, and the edit button is used to depict the selected area, fill in the glitch space in the default range, erase the area that does not need to be studied, and click calculate 3D to obtain a three-dimensional mask.We perform proper wrapping and smoothing operations on the masked three-dimensional model to obtain a normal three-dimensional model containing the L4 vertebral body and intervertebral disc. Importing it into FEA for processing, we use surface spine biomechanical meshing, automatically reduce the mesh and adjust the number of meshes to obtain a triangular mesh pattern, and use a free division mode to convert the triangular mesh into a tetrahedral mesh to get the volume mesh model. The material assignment is carried out through the material that comes with Mimics, and the empirical formula assignment method is used, the model is assigned to the material, the formula is used to assign the value and compared with the empirical results, the elastic modulus and Poisson’s ratio are modified, and a complete normal human L4 vertebral body and intervertebral disc model is established.


### 3.3. Example Application and Analysis

This article adopts the method of three-dimensional spine biomechanics through Mimics l0 and ANSYS 13 software to study the biomechanics of changes in spinal stability after treatment of lumbar disc herniation.Methods. (1) Select normal healthy adult volunteers, no history of lumbar spine disease, male, height 175 cm, weight 70 kg, and perform thin-slice CT scans of 0.9 mm on their lumbar spine to obtain CT data in DICOM format. (2) Importing it into the Mimics l0 software for modeling, divide the surface mesh, build the volume model, assign the material, and get the in vitro model of the normal lower lumbar spine L4-5 including the intervertebral disc. (3) Through Boolean shearing and other functions, by setting the shearing area to simulate L4-5 intervertebral disc removal surgery respectively, we establish A, B, and C including normal model, removal surgery model, small fenestration surgery model, and articular process removal surgery model. (4) Import the four groups of models into ANSYS 13 software for stress load simulation, and obtain the corresponding total displacement vector sum, total mechanical strain, and statistical cloud graph data for application SPSS 20 to analyze the data.Figure7 shows a box diagram of the range of spinal pressure load values. A normal human L4 vertebral disc model will be established. There are 40 finite elements, of which there are 45 nodes. We import it into ANSYS 13 software and simulate normal people by applying 500 N pressure load on the upper end plate surface node of waist, and restricting movement in X, Y, and Z directions on the bottom surface node of waist. Spinal pressure process: a torsional load of 8 N in the X direction is applied to the transverse process and the upper surface of the spinous process of the waist, and other constraints remain unchanged, and the numerical value of the spine in flexion and extension is obtained. Torque is applied to the reference points to simulate the six motion states of cervical spine flexion, extension, left-right rotation, and left-right scoliosis. The range of motion of each segment of the cervical spine is measured and compared with the results of previous in vitro and finite element experiments. It is basically similar to the research conducted in the literature verification, and the relevant values are compared. The results of this experiment are compared with the three groups of values, P > 0.05, indicating that there is no significant difference between the results of this experiment and the other three groups of experiments. The verification confirms that the model is consistent with previous studies. The current stress cloud images in the three directions of X, Y, and Z are consistent with the actual situation, and the appearance conforms to the physiological anatomy, and it is accurate and usable.Figure 7
Box diagram of spine pressure load value change interval.We performed flexion/extension, left/right flexion and left/right axial rotation on the experimental specimens on the mechanical testing machine to measure the maximum range of different motions. The data obtained are represented, and the single-factor analysis of variance is performed under the SPSS 13 statistical software in the microcomputer. In the simulated operation, the movement of the spine specimens in all directions was not significantly different from that of the normal control group (P > 0.05); the simulated hemilaminectomy chain nucleus extraction was performed simply. After the interlaminar and inferior articular processes were removed, the movement of the specimen in all directions was not significantly different from that of the normal control group except for the right rotation (P > 0.05).After all the inferior articular processes were removed, the movement in all directions is significantly different from that of the normal control group (P < 0.05 for right rotation); under the simulated total laminectomy, the movement of the specimen in all directions is very different from that of the normal control group (P < 0.01). Figure 8 shows the statistical distribution of disc sensitivity deviation. The intervertebral disc tissue is most sensitive to pressure. Group A showed that the pressure sensitive area was located on the posterior edge of the intervertebral disc. The pressure sensitivity of the three groups B, C, and D was located on the fibrous annulus of the posterior edge of the intervertebral disc after resection. The sensitivity of the front edge subsided. As the decompression range increases, the pressure sensitivity of the value becomes larger. The simulated resection group B was smaller than the other operation groups in terms of displacement, pressure, and stress sensitivity.Figure 8
Statistical distribution of disc sensitivity deviation.The maximum principal strain data of the upper endplate were extracted from the two groups of models, and the unit with the maximum principal strain was defined as the unit with high fracture risk. Both the intact vertebral body and group B have 3 high-risk units for vertebral body endplate fractures, accounting for 0.15% of the total number of endplate units. We selected the sidewall of the bone tunnel where the stress is concentrated in the vertebral body as the research object and measured the change trend of von Mises stress distribution along the path from the ventral side to the dorsal side of the vertebral bone tunnel sidewall with different perforation diameters. In group A, the high-risk units for fractures of models appear in the endplates. Around the damage margin, consistent with the von Mises stress concentration position, the fracture high-risk units of the model are widely distributed in the residual area of the anterior endplate. The fracture risk prediction was performed on the upper endplate of each model, and the results indicated that there were different numbers of high-risk fracture units in the upper endplate of the A group model, while the upper endplate of the group B model is low. Figure9 shows a comparison chart of the significance level of the spine biomechanical model. The stress data of the anterior and posterior upper endplates of the vertebral body in groups A and B were analyzed by one-way analysis of variance with the normal model data. Both bone tunnels have an effect on the endplate stress distribution (P = 0.01). Among them, the stress value of the upper endplate of the model A has no significant difference compared with the normal model (P > 0.05), and the stress value of the upper endplate of the model B has no significant difference compared with the normal model (P > 0.05). Compared with the normal model, the end plate stress data of the model are significantly different.Figure 9
Comparison of the significance level of the spine biomechanical model.


## 3.1. Data Processing of Lumbar Intervertebral Disc Detection

In this paper, SPSS 13 statistical software is used, and the data obtained are expressed. The comparison of the sample means between each group uses a one-way analysis of variance. We analyze whether there are significant changes in the status of various simulated operations compared with normal spine specimens. The main tool used for data processing is Simpleware software, which consists of three parts. Here, two modules, ScanIP and ScanFE, are mainly used. After the modeling is completed, the material of the spine model is set according to the physical characteristics of the actual human spine so that the model is as close to the actual human spine as possible. Because ANSYS has a very good openness, it can take advantage of this feature of ANSYS to carry out secondary development, modify and expand the functions of ANSYS, and develop a special spine biomechanical analysis tool for the human spine model. Finally, the model is imported into ANSYS, and different loads and constraints are applied to the spine model according to the analysis steps to simulate the movement of the spine. The calculation results of each model are analyzed in the results and experimental conclusions are drawn.The data used in this article are 60 frames of continuous format data obtained by continuous scanning of the human body. The data are read into ScanIP for viewing and processing. First, we adjust the resolution to achieve the purpose of adjusting the accuracy of the model. This step is called resampling. In this project, the imported CT data are trimmed, and data resampled in ScanIP so that only useful data are retained, and the number of grids is reduced. In ScanIP, the part of interest is segmented by observing the different gray values. There are many factors that affect the internal pressure of the intervertebral disc, such as whether the intervertebral disc is originally degenerated, the range of motion of the segment, muscle tension, ligament tension, abdominal pressure, and so on. The bone tissue is easily observed on the CT image, so it is easier to divide the boundary between them. Then, we use the confidence region connection method to fill in the divided regions to obtain plane models of different parts of the fault. Unlike the spine, the characteristics of the intervertebral disc are closer to soft tissue, so it is not very clear on the CT image. We can use all knowledge of medical anatomy to outline the general outline of the intervertebral disc and then fill it. Next, we must perform filtering processing, boundary region processing, threshold segmentation, and other operations on the plane model, and finally generate a three-dimensional spine model based on the multilayer tomographic plane model.Figure4 shows the histograms of the changes in vertebrae expansion and contraction of different specimen numbers. With the increase in the resection of the posterior structure in different surgical methods of the lumbar spine, the range of motion of the lumbar spine specimens in flexion/extension is increasing. From specimen B to specimen C, compared with specimen A, the average increase in flexion range was 3.3%, 5.0%, 9.5%, 16.9%, and 30.2%, respectively. The average increase in extension range was 6.6%, 8.0%, 13.7%, 22.6%, and 32.3%. According to statistical analysis, compared with specimen A, specimens B, C, and D have no significant difference in flexion/extension changes, specimen D has significant differences in flexion/extension, and specimen C has a significant difference in flexion/extension.Figure 4
Histogram of changes in vertebral extension of different specimen numbers.


## 3.2. Simulation of the Biomechanical Model of the Spine

This article is mainly aimed at CT plain scans of normal patients without disease, using Mimics software and ANSYS software to establish a three-dimensional spine biomechanical model of the normal spine, and simulate, stress, load loading, and other conditions on the three-dimensional finite element model of the normal spine. For digital simulation of surgery, etc., we establish a three-dimensional spine biomechanical model after surgery and other different surgical plans and perform stress analysis, and at the same time analyze and compare the data. Sixty-one patients diagnosed with postoperative recurrence of lumbar disc herniation and surgical treatment were selected, and the initial surgical plan for recurrence and the reason for the re-operation were counted. According to the treatment method of re-operation, 50 patients in the observation group were divided into the observation group, and the control group was fixed with posterior approach. There were 50 patients undergoing fusion surgery. Figure5 shows the line comparison chart of the visual simulation score of the spine biomechanics model. Statistics of the blood loss during the second operation, operation time, postoperative score, Visual Analogue Scale (VAS) score, etc., of the two treatment methods were calculated using SPSS 13 to perform statistical analysis. The observation group and the control group had significant differences in intraoperative blood loss and operation time, but there was no significant difference in postoperative score and VAS score.Figure 5
Comparison chart of spine biomechanics model visual simulation score line.The steps of spine biomechanics analysis mainly include preprocessing, loading and solving, and postprocessing. The work that can be completed in the preprocessing includes building the model, setting the properties of the material, applying different loads and boundary conditions, and defining various contact relationships. The establishment of the biomechanical model of the spine and the setting of the material properties have been completed before. Now only the load and boundary conditions of the model and the contact relationship need to be defined, the stress and strain of the lumbar spine can be simulated and simulated. Loads in ANSYS can be divided into two categories: one is boundary conditions, and the other is excitation. The function of ANSYS is to apply different excitations and different boundary conditions to the model to be analyzed for spine biomechanics, and then we perform the analysis to obtain the response. Figure6 shows the linear fitting of the coupling ratio of the model nodes. The maximum stress between the different models increases with the increase of the punch diameter, but all are below the lower limit of the 95% confidence interval of the endplate failure strength, and the difference between the models is not obvious, and the difference is not much from the normal value, so the endplate fracture risk is low. According to the previous introduction, here for the contact relationship, the coupling operation is used to simulate so that the calculation maintains a linear relationship so that the nodes of the contact parts of different materials are set to be the same. In this paper, manual point selection is used to select points between nodes at the same location so that various materials connecting nodes are automatically coupled together.Figure 6
Linear fitting of model node coupling ratio.We use a high-resolution Philips 64-slice CT machine to scan the lower lumbar spine with 140 kV, 200 mA conditions, and 0.9 mm intervals. The scan length is about 84 cm to obtain 1000 pictures in DICOM format. The CD completes the data collection. We use the image import function to select the CD-ROM drive; the system will automatically recognize the DICOM format pictures and sequences in the disc and generate three window pictures including sagittal, coronal, and transverse positions. We select the L4 to be studied on the scanned CT film. By using the method of setting CT threshold on the skeletal plain scan to distinguish between bone and surrounding soft tissues, we use profile line to select StartThresholding option and select Apply option to start rendering, and get the system. The area of the CT threshold range is selected by default, and the edit button is used to depict the selected area, fill in the glitch space in the default range, erase the area that does not need to be studied, and click calculate 3D to obtain a three-dimensional mask.We perform proper wrapping and smoothing operations on the masked three-dimensional model to obtain a normal three-dimensional model containing the L4 vertebral body and intervertebral disc. Importing it into FEA for processing, we use surface spine biomechanical meshing, automatically reduce the mesh and adjust the number of meshes to obtain a triangular mesh pattern, and use a free division mode to convert the triangular mesh into a tetrahedral mesh to get the volume mesh model. The material assignment is carried out through the material that comes with Mimics, and the empirical formula assignment method is used, the model is assigned to the material, the formula is used to assign the value and compared with the empirical results, the elastic modulus and Poisson’s ratio are modified, and a complete normal human L4 vertebral body and intervertebral disc model is established.


## 3.3. Example Application and Analysis

This article adopts the method of three-dimensional spine biomechanics through Mimics l0 and ANSYS 13 software to study the biomechanics of changes in spinal stability after treatment of lumbar disc herniation.Methods. (1) Select normal healthy adult volunteers, no history of lumbar spine disease, male, height 175 cm, weight 70 kg, and perform thin-slice CT scans of 0.9 mm on their lumbar spine to obtain CT data in DICOM format. (2) Importing it into the Mimics l0 software for modeling, divide the surface mesh, build the volume model, assign the material, and get the in vitro model of the normal lower lumbar spine L4-5 including the intervertebral disc. (3) Through Boolean shearing and other functions, by setting the shearing area to simulate L4-5 intervertebral disc removal surgery respectively, we establish A, B, and C including normal model, removal surgery model, small fenestration surgery model, and articular process removal surgery model. (4) Import the four groups of models into ANSYS 13 software for stress load simulation, and obtain the corresponding total displacement vector sum, total mechanical strain, and statistical cloud graph data for application SPSS 20 to analyze the data.Figure7 shows a box diagram of the range of spinal pressure load values. A normal human L4 vertebral disc model will be established. There are 40 finite elements, of which there are 45 nodes. We import it into ANSYS 13 software and simulate normal people by applying 500 N pressure load on the upper end plate surface node of waist, and restricting movement in X, Y, and Z directions on the bottom surface node of waist. Spinal pressure process: a torsional load of 8 N in the X direction is applied to the transverse process and the upper surface of the spinous process of the waist, and other constraints remain unchanged, and the numerical value of the spine in flexion and extension is obtained. Torque is applied to the reference points to simulate the six motion states of cervical spine flexion, extension, left-right rotation, and left-right scoliosis. The range of motion of each segment of the cervical spine is measured and compared with the results of previous in vitro and finite element experiments. It is basically similar to the research conducted in the literature verification, and the relevant values are compared. The results of this experiment are compared with the three groups of values, P > 0.05, indicating that there is no significant difference between the results of this experiment and the other three groups of experiments. The verification confirms that the model is consistent with previous studies. The current stress cloud images in the three directions of X, Y, and Z are consistent with the actual situation, and the appearance conforms to the physiological anatomy, and it is accurate and usable.Figure 7
Box diagram of spine pressure load value change interval.We performed flexion/extension, left/right flexion and left/right axial rotation on the experimental specimens on the mechanical testing machine to measure the maximum range of different motions. The data obtained are represented, and the single-factor analysis of variance is performed under the SPSS 13 statistical software in the microcomputer. In the simulated operation, the movement of the spine specimens in all directions was not significantly different from that of the normal control group (P > 0.05); the simulated hemilaminectomy chain nucleus extraction was performed simply. After the interlaminar and inferior articular processes were removed, the movement of the specimen in all directions was not significantly different from that of the normal control group except for the right rotation (P > 0.05).After all the inferior articular processes were removed, the movement in all directions is significantly different from that of the normal control group (P < 0.05 for right rotation); under the simulated total laminectomy, the movement of the specimen in all directions is very different from that of the normal control group (P < 0.01). Figure 8 shows the statistical distribution of disc sensitivity deviation. The intervertebral disc tissue is most sensitive to pressure. Group A showed that the pressure sensitive area was located on the posterior edge of the intervertebral disc. The pressure sensitivity of the three groups B, C, and D was located on the fibrous annulus of the posterior edge of the intervertebral disc after resection. The sensitivity of the front edge subsided. As the decompression range increases, the pressure sensitivity of the value becomes larger. The simulated resection group B was smaller than the other operation groups in terms of displacement, pressure, and stress sensitivity.Figure 8
Statistical distribution of disc sensitivity deviation.The maximum principal strain data of the upper endplate were extracted from the two groups of models, and the unit with the maximum principal strain was defined as the unit with high fracture risk. Both the intact vertebral body and group B have 3 high-risk units for vertebral body endplate fractures, accounting for 0.15% of the total number of endplate units. We selected the sidewall of the bone tunnel where the stress is concentrated in the vertebral body as the research object and measured the change trend of von Mises stress distribution along the path from the ventral side to the dorsal side of the vertebral bone tunnel sidewall with different perforation diameters. In group A, the high-risk units for fractures of models appear in the endplates. Around the damage margin, consistent with the von Mises stress concentration position, the fracture high-risk units of the model are widely distributed in the residual area of the anterior endplate. The fracture risk prediction was performed on the upper endplate of each model, and the results indicated that there were different numbers of high-risk fracture units in the upper endplate of the A group model, while the upper endplate of the group B model is low. Figure9 shows a comparison chart of the significance level of the spine biomechanical model. The stress data of the anterior and posterior upper endplates of the vertebral body in groups A and B were analyzed by one-way analysis of variance with the normal model data. Both bone tunnels have an effect on the endplate stress distribution (P = 0.01). Among them, the stress value of the upper endplate of the model A has no significant difference compared with the normal model (P > 0.05), and the stress value of the upper endplate of the model B has no significant difference compared with the normal model (P > 0.05). Compared with the normal model, the end plate stress data of the model are significantly different.Figure 9
Comparison of the significance level of the spine biomechanical model.


## 4. Conclusion

The spinal biomechanics analysis method can perform stress and strain analysis on complex shapes, and the mechanical performance test is comprehensive and objective. The application of biomechanical analysis of the spine to the lumbar spine is the current research hotspot. Lumbar degeneration is usually caused by a variety of cumulative injuries to the motor segments of the spine. The spine biomechanical model can simulate extremely complex tissues and load systems and can accurately simulate complex lumbar spine geometric models, study the stress and strain analysis of spinal motion segments under complex cyclic loads, and help us understand the biomechanical properties of the intervertebral disc and disc retraction. By comparing stress data and displacement data, this paper can analyze the differences between different spine models, which is of great significance to the research of the spine and the treatment of spine diseases. The computer simulation model can control the experimental conditions and calculate the contact area and stress of the vertebral body and the intervertebral disc. By comparing the stress data and the displacement data, the differences between different spine models can be analyzed, which has important guiding significance for the research of the spine and the treatment of spine diseases. In this way, the operation process can be simulated before the operation, and the purpose of helping the doctor to formulate a reasonable operation plan is achieved. After the operation, the effect of the operation can also be analyzed and appropriate recommendations can be given to the patient. This article reviews the data of patients with recurrence, using retrospective analysis method to make statistics on the patient’s age, initial operation time, operation method, operation segment, recurrence interval, recurrence reason, second operation method, etc. At the same time, the patients after the operation were followed up, JOA score, VAS score, and other conditions were performed, statistical analysis was performed, and relevant conclusions were drawn. Finally, compared with the previously established three-dimensional spine biomechanics model, analysis of the need for improvement and prevention and other prognostic measures are given.



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*Source: 2869488-2021-10-29.xml*