An optimal distal radius plate method based on optimal fracture gap strain

Abstract

The application discloses a distal radius bone plate optimization method based on optimal fracture gap strain, and specifically comprises the following steps: constructing a finite element model of a distal radius fracture internal fixation system and performing analysis; taking the minimum weighted bone end displacement as a target function and taking volume as a constraint to construct a topology optimization model based on the weighted sum and variable density method, and updating iteration until a convergence criterion is met to obtain an optimal topology configuration; and evaluating whether the optimal topology configuration meets the optimal fracture gap strain; the application uses weighted optimization, which is more suitable for the stress condition of a wrist joint in actual life; the bone plate obtained through the weighted optimization meets the optimal fracture gap strain under the condition of meeting the rigidity when used, the best healing is pursued, and the life quality of patients is improved.

Description

Technical Field

[0001] This invention relates to optimization methods, specifically to a method for optimizing the distal radius bone plate based on optimal fracture gap strain. Background Technology

[0002] Distal radius fractures are a common type of upper limb fracture in clinical treatment, accounting for about one-sixth of all fractures. Non-surgical treatment can be effective for some distal radius fractures; however, malunion occurs in some patients. Therefore, bone plates have become the preferred choice to promote better wrist joint healing and reduce complications. Bone plate design includes personalized and standardized designs. Compared to personalized plates, standardized plates with universal features are more widely used, but their effectiveness varies from person to person. Therefore, this study analyzes the biomechanics of bone plate fixation for distal radius fractures, optimizing the plate while ensuring basic function to better meet the needs of different individuals and achieve optimal healing. Many current optimization methods are standard topology optimizations under a single load, but in reality, the human radius is subjected to multiple loads simultaneously, not a single one. Furthermore, many optimization methods use bone plate stiffness as the optimization target, aiming to ensure optimal bone end displacement for healing. Therefore, the existing optimization method is improved by weighting the load and using the displacement of the bone fracture ends as the optimization target, which results in a more direct optimization effect. Summary of the Invention

[0003] The problem to be solved by the present invention is to provide a method for optimizing the distal radius bone plate based on the optimal fracture gap strain.

[0004] To achieve the above objectives, the present invention provides the following technical solution:

[0005] A method for optimizing the distal radius bone plate based on optimal fracture gap strain, characterized by comprising the following steps:

[0006] S1: Collect CT data of the patient's radius, use data processing software to obtain a three-dimensional model of the radius, determine the fracture type, and use Solidworks software to cut the radius model to obtain a distal radius fracture model.

[0007] S2: Establish an internal fixation system (bone plate, screw) model, assemble it with the distal radius fracture model to obtain a finite element model of the distal radius fracture internal fixation system, and perform finite element analysis;

[0008] S21: Use Solidworks software to build bone plate and screw models. Since the main research object is bone plate, the screw model is simplified to a cylindrical structure. The assembled geometric model is imported into ABAQUS analysis software to obtain the finite element model of the internal fixation system for distal radius fracture.

[0009] S22: Define material properties and contact in ABAQUS, where the radius body is set to cortical bone, the distal radius is set to cancellous bone, and the bone plate and screw are both made of titanium alloy.

[0010] S23: Define boundary conditions: Boundary conditions are divided into constraint boundary conditions and load boundary conditions;

[0011] Boundary constraints: Fixed constraints are applied to the proximal radius, and loads are applied to the distal radius;

[0012] Load boundary conditions: Establish a load application point on the distal radius wrist joint contact surface and couple it with the radius to apply three types of loads: compression, torsion, and bending.

[0013] S3: Based on the finite element analysis results, with the minimum weighted bone fracture displacement as the objective function and volume as the constraint, a topology optimization model based on the weighted and variable density method is constructed. The optimization region is selected, and the bone plate is subjected to topology optimization to obtain preliminary optimization results.

[0014] S4: Determine whether the displacement of the bone fragment under the optimized bone plate fixation meets the optimal fracture gap strain. If yes, the optimization is completed and redesign is performed. If not, the optimization parameter values ​​are changed and step S3 is continued.

[0015] Furthermore, in step S3, the topology optimization model based on the weighted sum variable density method is as follows:

[0016] objective function

[0017] constraint functions

[0018] 0 < ρ i ≤1;

[0019] Here, the objective function is to minimize the maximum bone end displacement within the region, where U represents a function of displacement, i represents an element, and n is the design response. t It is a displacement vector, ρ(i) is the density of the i-th element, and W t V(ρ) is the optimized volume, V0 is the volume of the design domain, and f is the set volume percentage.

[0020] Further, in step S3, the weights of axial, bending, and torsional loads in the weighted optimization are 50%, 30%, and 20% respectively, and the parameters are set in the optimization module of ABAQUS.

[0021] Furthermore, in step S4, the bone fragment displacement is evaluated by selecting the node displacements of the outer contour path at the fracture site.

[0022] The technical advantages of this invention's method for optimizing the distal radius bone plate based on optimal fracture gap strain are as follows:

[0023] Compared to existing optimization methods, this invention employs a weighted topology optimization method, improving upon the standard method to consider all possible physiological load conditions within a single simulation time. Axial, bending, and torsional loads are weighted at 50%, 30%, and 20% respectively, making the calculations closer to the actual stress conditions experienced by the human body. This results in more accurate optimization results, with the goal of minimizing weighted bone end displacement. This allows patients to achieve optimal healing under bone plate fixation, improving their quality of life. Since the effectiveness of serialized bone plates varies from person to person, the optimization method of this invention optimizes serialized bone plates to obtain individualized bone plates, enabling each patient to pursue optimal healing. Attached Figure Description

[0024] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0025] Figure 1 This is a flowchart illustrating the method for optimizing the distal radius bone plate based on optimal fracture gap strain according to the present invention:

[0026] Figure 2 This is the boundary condition setting diagram:

[0027] Figure 3 This is a diagram showing optimized parameter settings;

[0028] Figure 4 These are comparison images of the bone plate morphology before and after optimization;

[0029] Figure 5 This is a schematic diagram of the path of the distal outer contour nodes of the fracture.

[0030] Figure 6 It is a comparison diagram of bone fragment displacement before and after optimization. Detailed Implementation

[0031] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0032] Example 1: An optimization method for distal radius bone plate based on optimal fracture gap strain, the overall process is as follows: Figure 1As shown, it includes the following steps:

[0033] S1: Collect CT data of the patient's radius, use data processing software to obtain a three-dimensional model of the radius, determine the fracture type, and use Solidworks software to cut the radius model to obtain a distal radius fracture model.

[0034] S2: Establish an internal fixation system (bone plate, screw) model, assemble it with the distal radius fracture model to obtain a finite element model of the distal radius fracture internal fixation system, and perform finite element analysis. Specifically, it includes the following sub-steps.

[0035] S21: Establishing a finite element model of the internal fixation system for distal radius fractures

[0036] Solidworks software was used to create bone plate and screw models. Since the main research object was the bone plate, the screw model was simplified to a cylindrical structure. The assembled geometric model was imported into ABAQUS analysis software to obtain the finite element model of the internal fixation system for distal radius fracture.

[0037] S22: Define material properties and contact

[0038] In ABAQUS, material properties and contact are defined, where the radius body is set as cortical bone, the distal radius is set as cancellous bone, the bone plate and screw are both titanium alloy, the screw and bone are set as bonded, and the screw and bone plate are set as bonded. The material properties in the finite element model are shown in the table below.

[0039]

[0040] S23: Define boundary conditions

[0041] Boundary conditions are divided into constraint boundary conditions and load boundary conditions. Boundary condition settings are as follows: Figure 2 As shown; the constraint boundary conditions are: a fixed constraint is set at the proximal end of the radius, and a load is applied at the distal end; the load boundary conditions are: a load application point is established at the wrist joint contact surface at the distal end of the radius and coupled with the radius; three analysis steps are set, and a compressive load of 100N, a torsional load of 1Nm, and a bending load of 50N are applied.

[0042] S24: Mesh Generation

[0043] Based on the characteristics of different parts of the internal fixation system for distal radius fractures, the internal fixation system was meshed using a hybrid mesh generation method with Hypermesh 2019 software. The bone plate and screws were meshed using hexahedral meshes, while the radius was meshed using tetrahedral meshes.

[0044] S3: Based on the finite element analysis results of S2, a topology optimization model based on the weighted and variable density method is constructed with the minimum weighted bone end displacement as the objective function and volume as the constraint. The optimization region is selected, and the bone plate is topologically optimized using the Optimization module in the ABAQUS finite element analysis software.

[0045] In this embodiment, the topology optimization method employs a weighted and variable density method, using volume as a constraint and minimizing the weighted bone fracture end displacement as the objective function. During optimization, the weighted displacement of the load-applying nodes is controlled to achieve the goal of controlling the bone fracture end displacement. In this embodiment, the volume reduction is set to 45%, and the optimization parameters are set as follows: Figure 3 Specifically, it includes the following sub-steps:

[0046] S31: Select optimization area

[0047] Based on the maximum stress point of the bone plate in the finite element analysis results, the neck region of the bone plate corresponding to the fracture area is selected as the optimization region.

[0048] S32: Define the objective function and constraint functions

[0049] objective function

[0050] constraint functions

[0051] 0 < ρ i ≤1;

[0052] Here, the objective function is to minimize the maximum bone end displacement within the region, where U represents a function of displacement, i represents an element, and n is the design response. t It is a displacement vector, ρ(i) is the density of the i-th element, and W t V(ρ) is the optimized volume, V0 is the volume of the design domain, and f is the set volume percentage.

[0053] The software operation involves designing responses based on the applied nodal axial displacement under compressive load, applied nodal torsional displacement under torsional load, and applied nodal displacement under bending load, as well as optimizing the region volume. The objective function is to minimize the weighted nodal displacements applied under the three loads, with the weights for compressive, bending, and torsional loads being 50%, 30%, and 20%, respectively.

[0054] S33: Perform iterative optimization

[0055] The maximum number of iterations was set to 50, and the final optimized slab morphology was compared to... Figure 4 As shown.

[0056] S4: Determine whether the displacement of the bone fragment under the optimized bone plate fixation meets the optimal fracture gap strain. If yes, the optimization is completed and redesign is performed. If not, the optimization parameter values ​​are changed and step S3 is continued.

[0057] Appropriate micromovement of the fracture ends promotes callus formation, but excessive movement causes significant strain on the fractured area, hindering callus formation and leading to delayed healing or even nonunion. Therefore, measuring bone end displacement is crucial for a more direct evaluation of fracture healing. This is achieved by assessing the displacement of bone ends at nodal points along the outer contour of the fracture site. (See...) Figure 5 The optimal fracture gap strain suggests that an axial displacement of 0.5-1 mm and a shear displacement of less than 0.8 mm between the fracture ends are optimal for fracture healing. Based on this standard, the changes in bone end displacement after optimization were compared.

[0058] A comparative analysis of the bone plate performance before and after optimization was conducted. The optimization results of this embodiment are shown in the table below: Comparison of bone end displacement. Figure 6 As shown:

[0059]

[0060] The analysis yielded the following results:

[0061] (1) The stiffness of the bone plate was significantly improved after optimization, indicating that the stability of the internal fixation system was increased after optimization.

[0062] (2) After optimization, both the axial displacement and shear displacement of the bone fracture ends were reduced to varying degrees. The axial displacement before and after optimization is as follows: Figure 6 As shown in (a), all conditions satisfy the optimal fracture gap strain, and the optimized shear displacement is reduced, as shown in [the diagram]. Figure 6 As shown in (b), the fracture gap has been reduced from more than 0.8 mm to less than 0.8 mm, which satisfies the optimal fracture gap strain and can achieve the best healing effect.

[0063] The above description of specific illustrative embodiments of the present invention is intended to enable those skilled in the art to understand the invention, but is not intended to limit the invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the invention should be included within the scope of protection of the invention.

Claims

1. A method for optimizing the distal radius bone plate based on optimal fracture gap strain, characterized in that: The specific implementation steps are as follows: S1: Collect CT data of the patient's radius, use data processing software to obtain a three-dimensional model of the radius, determine the fracture type, and use Solidworks software to cut the radius model to obtain a distal radius fracture model. S2: Establish the bone plate and screw model of the internal fixation system, assemble it with the distal radius fracture model, obtain the finite element model of the internal fixation system for distal radius fracture, and perform finite element analysis; S21: Use Solidworks software to build bone plate and screw models. Since the main research object is bone plate, the screw model is simplified to a cylindrical structure. The assembled geometric model is imported into ABAQUS analysis software to obtain the finite element model of the internal fixation system for distal radius fracture. S22: Define material properties and contact in ABAQUS, where the radius body is set to cortical bone, the distal radius is set to cancellous bone, and the bone plate and screw are both made of titanium alloy. S23: Define boundary conditions: Boundary conditions are divided into constraint boundary conditions and load boundary conditions; Boundary constraints: Fixed constraints are applied to the proximal radius, and loads are applied to the distal radius; Load boundary conditions: Establish a load application point on the distal radius wrist joint contact surface and couple it with the radius to apply three types of loads: compression, torsion, and bending. S3: Based on the finite element analysis results, with the minimum weighted bone fracture displacement as the objective function and volume as the constraint, a topology optimization model based on the weighted and variable density method is constructed. The optimization region is selected, and the bone plate is subjected to topology optimization to obtain preliminary optimization results. S4: Determine whether the displacement of the bone fragment under the optimized bone plate fixation meets the optimal fracture gap strain. If yes, the optimization is completed and redesign is performed. If not, the optimization parameter values ​​are changed and step S3 is continued.

2. The method for optimizing the distal radius bone plate based on optimal fracture gap strain according to claim 1, characterized in that: In step S3, the topology optimization model based on the weighted sum variable density method is as follows: objective function constraint functions 0<ρ i ≤1; Here, the objective function is to minimize the maximum bone end displacement within the region, where U represents a function of displacement, i represents an element, and n is the design response. t It is a displacement vector, ρ(i) is the density of the i-th element, and W t V(ρ) is the optimized volume, V0 is the volume of the design domain, and f is the set volume percentage.

3. The method for optimizing the distal radius bone plate based on optimal fracture gap strain according to claim 1, characterized in that: In step S3, the weights of axial, bending, and torsional loads in the weighted optimization are 50%, 30%, and 20%, respectively, and the parameters are set in the optimization module of ABAQUS.

4. The method for optimizing the distal radius bone plate based on optimal fracture gap strain according to claim 1, characterized in that: In step S4, the bone fragment displacement is evaluated by selecting the node displacements of the outer contour path at the fracture site.

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