A method for constructing a acetabular quadrilateral fracture model based on CT and MRI

Abstract

The present invention is applicable to the technical field of medical digital modeling, and in particular relates to a method for constructing an acetabular quadrilateral fracture model based on CT and MRI. The method combines three-dimensional modeling of bone structure and ligament structure with models of different internal fixation devices, and performs finite element analysis by simulating different body positions of the human body to impose constraints and loads, so as to analyze the effects of different internal fixation methods on the human body and obtain an acetabular quadrilateral fracture model, thereby providing technical and data references for actual acetabular quadrilateral internal fixation methods, which is beneficial for medical technicians to improve work efficiency.

Description

Technical Field

[0001] The present invention is applicable to the technical field of medical digital modeling, and in particular relates to a method for constructing an acetabular quadrilateral fracture model based on CT and MRI. Background Art

[0002] Related studies have pointed out that acetabular fractures account for about 0.8% of total body fractures, and the incidence rate in women is higher than that in men. With the continuous development of the transportation and construction industry and the aging of the population, the incidence rate of acetabular quadrilateral fractures has increased year by year. For unstable acetabular quadrilateral fractures, open reduction and internal fixation are mainly used in clinical treatment. Acetabular posterior column channel screws, quadrilateral comb screws, and posterior column channel screws combined with quadrilateral comb screws are currently commonly used internal fixation methods. The acetabulum is anatomically located deep, the inner wall of the quadrilateral is thin, and it is surrounded by many blood vessels and nerves. In addition, acetabular quadrilateral fractures are often comminuted, which makes reduction difficult, and screw placement is easy to penetrate the wall and involve the hip joint cavity. Therefore, the choice of acetabular quadrilateral internal fixation method is one of the hot issues in current research.

[0003] At present, the selection of the four-sided internal fixation method of the acetabulum still relies heavily on the experience and judgment of medical technicians. This method objectively has efficiency problems. In addition, due to the differences in human body structures, the four-sided internal fixation method of the acetabulum will also be different in actual situations, which undoubtedly puts higher demands on medical technicians.

[0004] Therefore, it is necessary to propose a method for the quadrilateral fixation of the acetabulum to solve the above problems. Summary of the invention

[0005] The present invention provides a method for constructing an acetabular quadrilateral fracture model based on CT and MRI, aiming to solve the problem that the existing acetabular quadrilateral internal fixation method has no reference and is difficult to analyze.

[0006] In order to solve the above technical problems, the present invention provides a method for constructing an acetabular quadrilateral fracture model based on CT and MRI, comprising the following steps:

[0007] S1. Acquire CT data and MRI data for constructing a fracture model;

[0008] S2. Based on the CT data, the bony structure is divided and a three-dimensional model of the bony structure is established. Meanwhile, based on the MRI data, a ligament structure including bilateral pubofemoral ligaments, iliofemoral ligaments and ischiofemoral ligaments is divided, and the three-dimensional model of the bony structure is assembled with the ligament structure at the origin to obtain a three-dimensional solid model of the lumbar spine, pelvis and hip joint;

[0009] S3, dividing the sacrum, hip bone and bone fragments based on the CT data, establishing a pelvic model, and designing the acetabulum quadrilateral fracture line on the pelvic model;

[0010] S4, generating different screw models and steel plate models by modeling, assembling and fixing the different screw models and steel plate models as internal fixation devices on the three-dimensional solid model, and obtaining a plurality of three-dimensional solid models to be analyzed;

[0011] S5, dividing the material properties of the nodes of each bone structure and ligament structure in the three-dimensional solid model to be analyzed with different preset material coefficients, wherein the material properties include at least one of elastic modulus, Poisson's ratio and stiffness coefficient;

[0012] S6. Apply loads to different three-dimensional solid models to be analyzed, and obtain preset observation indicators on the acetabular quadrilateral fracture line of different three-dimensional solid models to be analyzed through a finite element analysis method, and select the three-dimensional solid model to be analyzed that meets the preset load conditions based on the preset observation indicators and output it as the acetabular quadrilateral fracture model.

[0013] Furthermore, step S2 also includes: according to the position analysis of the bony structure, the three-dimensional model of the bony structure is shifted inward by 2 mm to obtain a cancellous bone model, and the cancellous bone model is added to the three-dimensional solid model.

[0014] Furthermore, step S2 also includes: performing at least one of smoothing, noise removal, and sandpaper polishing on the three-dimensional solid model to make the surface of the three-dimensional solid model smooth.

[0015] Furthermore, the screw model includes at least one of a quadrilateral comb screw with a diameter of 3.5 mm and a length of 80 mm, a common cortical screw with a diameter of 3.5 mm and a length of 40 mm, and a posterior column hollow lag screw with a diameter of 7.3 mm, a length of 100 mm and a thickness of 1.15 mm.

[0016] Furthermore, step S5 also includes: meshing the nodes of each bone structure and ligament structure in the three-dimensional solid model to be analyzed, and determining the size of the mesh for the nodes corresponding to different bone structures and ligament structures according to the size of the structure.

[0017] Furthermore, the manner of applying loads to different three-dimensional solid models to be analyzed in step S6 is specifically:

[0018] Different body positions of the human body are simulated, and loads are applied to the three-dimensional solid model to be analyzed in the standing position, lying position, side-lying position, sitting position, and the direction of femoral head impact.

[0019] Furthermore, the preset observation index includes at least one of the relative displacement of the acetabular quadrilateral fracture line, the maximum equivalent Von-mises stress and stress distribution cloud map of the internal fixation device, and the maximum equivalent Von-mises stress and stress distribution cloud map of the screw model.

[0020] Furthermore, when observing the relative displacement of the acetabular quadrilateral fracture line, multiple points are selected in the acetabular quadrilateral fracture line according to preset intervals, and the difference between the maximum displacement and the minimum displacement between different points is calculated to obtain the relative displacement.

[0021] The beneficial effect achieved by the present invention is that a method for constructing an acetabular quadrilateral fracture model based on CT and MRI is proposed. The method combines the models of different internal fixation devices through three-dimensional modeling of bone structure and ligament structure, and applies constraints and loads by simulating different body positions of the human body to perform finite element analysis, so as to analyze the effects of different internal fixation methods on the human body and obtain an acetabular quadrilateral fracture model, thereby providing technical and data references for actual acetabular quadrilateral internal fixation methods, which is beneficial for medical technicians to improve work efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic diagram of the steps of the method for constructing an acetabular quadrilateral fracture model based on CT and MRI provided by an embodiment of the present invention;

[0023] Figure 2 is a schematic diagram of modeling a three-dimensional solid model provided by an embodiment of the present invention;

[0024] Figure 3 is a schematic diagram of the overall structure of a three-dimensional solid model provided by an embodiment of the present invention;

[0025] Figure 4 is a schematic diagram of the orientation of the acetabular quadrilateral fracture line provided by an embodiment of the present invention;

[0026] Figure 5 is a schematic diagram of the acetabular quadrilateral fracture line provided by an embodiment of the present invention;

[0027] Figure 6 is a schematic diagram of a three-dimensional solid model to be analyzed of different internal fixation devices provided by an embodiment of the present invention;

[0028] Figure 7 is a schematic diagram of the model connection relationship provided by an embodiment of the present invention;

[0029] Figure 8 is a schematic diagram of model load constraints provided by an embodiment of the present invention;

[0030] Fig. 9is a schematic diagram of observation indicators provided by an embodiment of the present invention;

[0031] Fig.10 is a schematic diagram of the relative displacement result of the fracture line path provided by an embodiment of the present invention;

[0032] Fig.11 It is a schematic diagram of the maximum equivalent Von-mises stress result of the internal fixation device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0034] Please refer to Figure 1 , Figure 1 1 is a schematic diagram of the steps of a method for constructing a acetabular quadrilateral fracture model based on CT and MRI provided by an embodiment of the present invention. The method for constructing a acetabular quadrilateral fracture model based on CT and MRI comprises the following steps:

[0035] S1. Acquire CT data and MRI data for constructing a fracture model.

[0036] The CT data used in the embodiment of the present invention is obtained by scanning a human body in a supine position using a 256-row spiral CT machine, and the number of CT data layers is 2993, and the layer thickness is 0.63 mm; the MRI data is obtained by scanning a human body in a supine position using an MRI machine, and the number of MRI data layers is 50, and the layer thickness is 1.3 mm.

[0037] S2. Divide the bony structure based on the CT data and establish a three-dimensional model of the bony structure. At the same time, divide the ligament structure including the bilateral pubofemoral ligament, iliofemoral ligament, and ischiofemoral ligament based on the MRI data, assemble the three-dimensional model of the bony structure with the ligament structure at the origin, and obtain a three-dimensional solid model of the lumbar spine, pelvis, and hip joint.

[0038] Step S2 also includes: according to the position analysis of the bony structure, shifting the three-dimensional model of the bony structure inward by 2 mm to obtain a cancellous bone model, and adding the cancellous bone model to the three-dimensional solid model.

[0039] Step S2 also includes: performing at least one of smoothing, noise removal, and sandpaper polishing on the three-dimensional solid model to make the surface of the three-dimensional solid model smooth.

[0040] like Figure 2 and Figure 3 As shown, Figure 2is a schematic diagram of the modeling of the three-dimensional solid model constructed in an embodiment of the present invention, Figure 3 It is a schematic diagram of the overall structure of the three-dimensional solid model constructed in an embodiment of the present invention.

[0041] S3. Segment the sacrum, hip bone and bone fragments based on the CT data, establish a pelvic model, and design the acetabulum quadrilateral fracture line on the pelvic model.

[0042] The acetabular quadrilateral fracture line in the embodiment of the present invention is adjusted to the following three-dimensional solid model according to the healthy side hip bone resetting fragments after the pelvic model is established: Figure 4 The specific position shown in the figure is used, and the fracture line map is drawn layer by layer on the model plane using drawing software. Through relevant data and observation and statistics of its distribution law, the following is designed: Figure 5 Acetabular fracture line involving the quadrilateral is shown.

[0043] S4. Generate different screw models and steel plate models through modeling, assemble and fix the different screw models and steel plate models as internal fixation devices on the three-dimensional solid model, and obtain multiple three-dimensional solid models to be analyzed.

[0044] The screw model includes at least one of a quadrilateral comb screw with a diameter of 3.5 mm and a length of 80 mm, a common cortical screw with a diameter of 3.5 mm and a length of 40 mm, and a posterior column hollow lag screw with a diameter of 7.3 mm, a length of 100 mm and a thickness of 1.15 mm.

[0045] The purpose of designing multiple groups of internal fixation device models in the embodiment of the present invention is to obtain the optimal fixation scheme through comparison. Specifically, corresponding to the type of the screw model, four three-dimensional solid models to be analyzed are designed including a blank control group without using an internal fixation device, including a blank control group, a posterior column channel screw internal fixation group, a quadrilateral comb screw internal fixation group, and a posterior column channel screw combined with a quadrilateral comb screw internal fixation group. For the convenience of comparison, they are defined as group a, group b, group c and group d, respectively. The fixation methods are as follows: Figure 6 shown.

[0046] S5. Divide the material properties of the nodes of each bone structure and ligament structure in the three-dimensional solid model to be analyzed into different material properties based on preset material coefficients, wherein the material properties include at least one of elastic modulus, Poisson's ratio and stiffness coefficient.

[0047] Step S5 also includes: meshing the nodes of each bone structure and ligament structure in the three-dimensional solid model to be analyzed, and determining the size of the mesh for the nodes corresponding to different bone structures and ligament structures according to the size of the structure.

[0048] For the convenience of analysis, the three-dimensional solid models to be analyzed constructed in the embodiments of the present invention are all isotropic linear models. Exemplarily, the properties of each material are shown in Table 1 below, wherein the mesh size of the three-dimensional model is adjusted using tetrahedral units, the mesh size of the cortical bone and cancellous bone of the left hip bone, sacrum, L4 and L5 is set to 1mm, the mesh size of the internal fixation device is adjusted to 1mm, and the mesh size of the remaining bone structures, cartilage, and ligaments is set to 2mm. The number of grid units in group a is 2257270, and the number of nodes is 3960161; the number of grid units in group b is 2285474, and the number of nodes is 4011568; the number of grid units in group c is 2294378, and the number of nodes is 4028962; the number of grid units in group d is 2323101, and the number of nodes is 4081141.

[0049] Table 1 Material properties

[0050]

[0051] S6. Apply loads to different three-dimensional solid models to be analyzed, and obtain preset observation indicators on the acetabular quadrilateral fracture line of different three-dimensional solid models to be analyzed through a finite element analysis method, and select the three-dimensional solid model to be analyzed that meets the preset load conditions based on the preset observation indicators and output it as the acetabular quadrilateral fracture model.

[0052] The manner of applying loads to different three-dimensional solid models to be analyzed in step S6 is specifically:

[0053] Different body positions of the human body are simulated, and loads are applied to the three-dimensional solid model to be analyzed in the standing position, lying position, side-lying position, sitting position, and the direction of femoral head impact.

[0054] Specifically, before applying the load, you need to define the connection method for each component in the model, such as Figure 7 As shown, the faces cut to separate the upper and lower parts of the left hip bone are bound by changing the definition type between the parts.

[0055] like Figure 8 As shown, the specific load applied by the embodiment of the present invention is as follows:

[0056] Standing position: constrain the distal ends of both femurs and apply a 500N load vertically downward on the L4 plane;

[0057] Lying position: constrain the posterior edge of the iliac crest on both sides, and apply a load of 250N to the front of the iliac crest on both sides;

[0058] Lateral position: constrain the distal femoral sections on both sides, and apply a load of 500N horizontally to the right above the iliac wing of the left hip bone;

[0059] Sitting position: restrain both femurs, constrain both ischial tuberosities, and apply a load of 500N on L4 to simulate the direction of gravity;

[0060] Femoral head impingement: restrain the bilateral femurs, constrain the sacrum and left hip bone, and apply a load of 500N to the acetabulum along the femoral neck.

[0061] The preset observation index includes at least one of the relative displacement of the acetabular quadrilateral fracture line, the maximum equivalent Von-mises stress and stress distribution cloud map of the internal fixation device, and the maximum equivalent Von-mises stress and stress distribution cloud map of the screw model.

[0062] When observing the relative displacement of the acetabular quadrilateral fracture line, multiple points are selected in the acetabular quadrilateral fracture line according to preset intervals, and the difference between the maximum displacement and the minimum displacement between different points is calculated to obtain the relative displacement. Specifically, multiple points selected in the acetabular quadrilateral fracture line according to preset intervals are as follows: Fig. 9 As shown in A, the position of the screw model is as follows Fig. 9 As shown in B.

[0063] When analyzing the load results of the model, the relative displacement data of the fracture line path of the embodiment of the present invention was square root transformed, and after a normal distribution test, a one-way analysis of variance was performed between the groups. The measurement data were expressed as (x±s), and P<0.05 indicated that the difference was statistically significant.

[0064] The results of the implementation of the embodiment of the present invention based on the above material properties and load size are as follows:

[0065] For the relative displacement of the fracture path, please refer to Fig.10 , in the standing position, if Fig.10 As shown in Figure A, group a>group b>group c>group d (F=216.744, P<0.01); the other four groups of working conditions all showed a trend of group a>group c>group b>group d, among which, Fig.10 Middle B is lying position (F=220.641, P<0.01), Fig.10 Middle C is lateral position (F=196.204, P<0.01). Fig.10 Middle D is sitting position (F=205.071, P<0.01), Fig.10 Middle E is femoral head impact (F=213.206, P<0.01).

[0066] For the maximum equivalent Von-mises stress of internal fixation devices, please refer to Fig.11 , Fig.11 Middle A 1-5 The screw stress of the posterior column channel in group B is shown; 1-5The posterior column channel screw stress in group D is shown; C 1-5 The stress of the steel plate and the quadrilateral comb screw in group c is shown; D 1-5 The stress of the steel plate and quadrilateral comb screws in group d is shown; A1-D1 shows the standing position; A2-D2 shows the supine position; A3-D3 shows the lateral position; A4-D4 shows the sitting position; A5-D5 shows the femoral head impact. Fig.11 The results show that:

[0067] Posterior column channel screw stress: In the supine position, group d>group b ( Fig.11 -A2, B2; the other four groups of conditions all showed a trend of group b>group d ( Fig.11 -A 1，3-5 , B 1，3-5 );

[0068] The stress of the steel plate combined with the quadrilateral comb screw device: in the lateral position, the trend of group d>group c was shown ( Fig.11 -C3, D3), the other four groups showed a trend of group C>group D ( Fig.11 -C 1-2，4-5 , D 1-2，4-5 );

[0069] Ordinary cortical screw stress in group C and group D: As shown in Table 2, the standing position, lying position, and lateral position showed a trend of small screw 6> small screw 5> small screw 2> small screw 1; the sitting position and femoral head impact condition showed a trend of small screw 6> small screw 5> small screw 2> small screw 1.

[0070] Table 2 Maximum equivalent Von-mises stress of common cortical screws (MPa)

[0071]

[0072] Based on the above results, it can be seen that the mechanical properties of the posterior column channel screw combined with the quadrilateral comb screw are the best; the relative displacement in the standing position is large; the stress of the cortical bone screw through the plate is greater in the posterior direction than in the anterior direction. The cortical bone screw can be placed close to the fracture line through the plate, and the number of screws can be increased on the sacroiliac joint side according to the actual situation.

[0073] The beneficial effect achieved by the present invention is that a method for constructing an acetabular quadrilateral fracture model based on CT and MRI is proposed. The method combines the models of different internal fixation devices through three-dimensional modeling of bone structure and ligament structure, and applies constraints and loads by simulating different body positions of the human body to perform finite element analysis, so as to analyze the effects of different internal fixation methods on the human body and obtain an acetabular quadrilateral fracture model, thereby providing technical and data references for actual acetabular quadrilateral internal fixation methods, which is beneficial for medical technicians to improve work efficiency.

[0074] Those skilled in the art can understand that all or part of the processes in the above-mentioned embodiments can be implemented by instructing related hardware (which can be a mobile phone, a computer, a server, an air conditioner, or a network device, etc.) through a computer program, and the program can be stored in a computer-readable storage medium, and when the program is executed, it can include the processes of the embodiments of the above-mentioned methods. The storage medium can be a disk, an optical disk, a read-only memory (ROM) or a random access memory (RAM), etc.

[0075] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

[0076] The embodiments of the present invention are described above in conjunction with the accompanying drawings. What is disclosed is only the preferred embodiment of the present invention. However, the present invention is not limited to the above-mentioned specific implementation manner. The above-mentioned specific implementation manner is only illustrative rather than restrictive. Under the enlightenment of the present invention, ordinary technicians in this field can also make many forms and equivalent changes without departing from the scope of protection of the purpose of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for constructing an acetabular quadrilateral fracture model based on CT and MRI, characterized in that: The following steps are involved: S1. Acquire CT data and MRI data for constructing a fracture model; S2. Based on the CT data, the bony structure is divided and a three-dimensional model of the bony structure is established. Meanwhile, based on the MRI data, a ligament structure including bilateral pubofemoral ligaments, iliofemoral ligaments and ischiofemoral ligaments is divided, and the three-dimensional model of the bony structure is assembled with the ligament structure at the origin to obtain a three-dimensional solid model of the lumbar spine, pelvis and hip joint; S3, dividing the sacrum, hip bone and bone fragments based on the CT data, establishing a pelvic model, and designing the acetabulum quadrilateral fracture line on the pelvic model; S4, generating different screw models and steel plate models by modeling, assembling and fixing the different screw models and steel plate models as internal fixation devices on the three-dimensional solid model, and obtaining a plurality of three-dimensional solid models to be analyzed; S5, dividing the material properties of the nodes of each bone structure and ligament structure in the three-dimensional solid model to be analyzed with different preset material coefficients, wherein the material properties include at least one of elastic modulus, Poisson's ratio and stiffness coefficient; S6. Apply loads to different three-dimensional solid models to be analyzed, and obtain preset observation indicators on the acetabular quadrilateral fracture line of different three-dimensional solid models to be analyzed through a finite element analysis method, and select the three-dimensional solid model to be analyzed that meets the preset load conditions based on the preset observation indicators and output it as the acetabular quadrilateral fracture model.

2. The method for constructing a CT and MRI-based acetabular quadrilateral fracture model according to claim 1, wherein: Step S2 also includes: according to the position analysis of the bony structure, shifting the three-dimensional model of the bony structure inward by 2 mm to obtain a cancellous bone model, and adding the cancellous bone model to the three-dimensional solid model.

3. The method for constructing an acetabular quadrilateral fracture model based on CT and MRI according to claim 1, characterized in that: Step S2 also includes: performing at least one of smoothing, noise removal, and sandpaper polishing on the three-dimensional solid model to make the surface of the three-dimensional solid model smooth.

4. The method for constructing an acetabular quadrilateral fracture model based on CT and MRI according to claim 1, characterized in that: The screw model includes at least one of a quadrilateral comb screw with a diameter of 3.5 mm and a length of 80 mm, a common cortical screw with a diameter of 3.5 mm and a length of 40 mm, and a posterior column hollow lag screw with a diameter of 7.3 mm, a length of 100 mm and a thickness of 1.15 mm.

5. The method for constructing an acetabular quadrilateral fracture model based on CT and MRI according to claim 1, characterized in that: Step S5 also includes: meshing the nodes of each bone structure and ligament structure in the three-dimensional solid model to be analyzed, and determining the size of the mesh for the nodes corresponding to different bone structures and ligament structures according to the size of the structure.

6. The method for constructing an acetabular quadrilateral fracture model based on CT and MRI according to claim 1, characterized in that: The manner of applying loads to different three-dimensional solid models to be analyzed in step S6 is specifically: Different body positions of the human body are simulated, and loads are applied to the three-dimensional solid model to be analyzed in the standing position, lying position, side-lying position, sitting position, and the direction of femoral head impact.

7. The method for constructing an acetabular quadrilateral fracture model based on CT and MRI according to claim 1, characterized in that: The preset observation index includes at least one of the relative displacement of the acetabular quadrilateral fracture line, the maximum equivalent Von-mises stress and stress distribution cloud map of the internal fixation device, and the maximum equivalent Von-mises stress and stress distribution cloud map of the screw model.

8. The method for constructing an acetabular quadrilateral fracture model based on CT and MRI according to claim 7, characterized in that: When observing the relative displacement of the acetabular quadrilateral fracture line, multiple points are selected in the acetabular quadrilateral fracture line according to preset intervals, and the difference between the maximum displacement and the minimum displacement between different points is calculated to obtain the relative displacement.

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