Lightweight structure optimization method for scoliosis orthosis based on finite element analysis

Abstract

The invention relates to a lightweight structure optimization method for a scoliosis orthosis based on finite element analysis. The lightweight structure optimization method comprises the following steps: scanning to obtain CT data and body surface point cloud data of a patient; extracting a three-dimensional model of the skeleton according to the CT data, and constructing a preliminary scoliosis orthosis model in combination with the body surface point cloud data; performing surface mesh generation on the three-dimensional model of the skeleton, and assembling the three-dimensional model of the skeleton with an orthosis model to obtain a trunk-orthosis model; carrying out volume mesh generation on the trunk-orthosis model, exporting a finite element model, and carrying out finite element static analysis through finite element analysis software; inputting the orthosis model into topological optimization software, mapping a finite element statics analysis result to the inner surface of the model, and carrying out topological optimization; the optimized area is arranged to be of a hollow structure, and after the whole structure is optimized, the light orthosis is obtained. Compared with the prior art, the invention has the advantages that the lightweight design is realized, the structural cost is reduced, the structural strength is ensured, and the like.

Description

Technical Field

[0001] The invention relates to the field of orthosis structures, and in particular to a method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis. Background Art

[0002] Scoliosis is an abnormal curvature of the spine in the coronal plane, accompanied by axial rotation of the spine. The Scoliosis Research Society recommends that scoliosis be diagnosed when the Cobb angle of the spine is greater than or equal to 10° and axial rotation can be identified. Mild to moderate patients require orthotics as standard treatment to reduce the possibility of scoliosis progressing to surgery.

[0003] Patients with compliance greater than 90% had treatment outcomes five times better than those with compliance less than 90%. Poor compliance with orthoses is associated with poor quality of life, which may be due to poor appearance, improper pressure distribution, poor heat dissipation, restricted movement, or emotional discomfort. Therefore, a lot of attention has been placed on how to optimize the design, structure, and wearing habits of orthoses. Additive manufacturing technology, as a top-down, layer-by-layer process, can produce products of any complex shape. Combined with computer-aided design, it can make scoliosis orthoses fit the human body, be comfortable and beautiful, lightweight and breathable. It has been proven through clinical trials that it can effectively improve patient compliance, thereby improving the correction effect.

[0004] However, since the breathability of this new orthosis is achieved through some randomly distributed hollow patterns, the area of ​​the hollow area affects the mechanical properties of the orthosis. If the hollow area is too small, it will lead to insufficient breathability and lightweight; if the hollow area is too large, it will increase the risk of fracture failure and the difficulty of additive manufacturing, both of which will directly or indirectly increase the manufacturing cost, reduce the comfort of the orthosis, and thus affect the patient's compliance. Therefore, a suitable hollow design can fully utilize the advantages of the additive manufacturing process while ensuring that the orthosis does not fail, improve the comfort of the patient, and reduce the economic burden on the patient's family. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to provide a lightweight structure optimization method for scoliosis orthosis based on finite element analysis. A suitable hollow design is set up to fully utilize the advantages of additive manufacturing technology while ensuring that the orthosis does not fail, thereby improving the comfort of patients wearing it and reducing the economic burden on patients' families.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis, characterized in that it comprises the following steps:

[0008] Scan and obtain the patient's CT data and body surface point cloud data;

[0009] Extracting a three-dimensional model of the skeleton according to the CT data, and constructing a preliminary orthosis model for scoliosis in combination with the body surface point cloud data; performing surface meshing on the three-dimensional model of the skeleton, and then assembling it with the orthosis model to obtain a trunk-orthosis model; performing volume meshing on the trunk-orthosis model, and exporting it as a finite element model;

[0010] Import the finite element model into the finite element analysis software to perform finite element static analysis;

[0011] The orthosis model is input into the topology optimization software, and the finite element static analysis results are mapped to the inner surface of the orthosis model, so as to perform topology optimization;

[0012] The optimized area in the orthosis model is set as a hollow structure, and the overall structure is optimized to obtain a lightweight orthosis.

[0013] Furthermore, the method further comprises:

[0014] The model data of the obtained lightweight orthosis is input into the finite element analysis software for finite element static analysis to verify the mechanical properties; if it meets the preset mechanical performance requirements, the final lightweight orthosis is obtained; otherwise, the topology optimization software is used again for topology optimization.

[0015] Furthermore, the CT data is acquired by scanning with a computer tomography device, and the body surface point cloud data is acquired by scanning with an optical scanner, and the scanning range includes a portion from 5 cm above the upper edge of the first thoracic vertebra to 20 cm below the greater trochanter of the femur.

[0016] Furthermore, the extraction process of the three-dimensional model of the skeleton is specifically as follows:

[0017] Through grayscale measurement, threshold segmentation, region growing, multi-layer extraction and Boolean operation, individual vertebrae, ribs, costal cartilages, intervertebral discs, hip bones and femurs are extracted from CT data according to the human anatomical structure and force transmission relationship, thus obtaining a three-dimensional model of the skeleton.

[0018] Furthermore, the construction process of the orthosis model is specifically as follows:

[0019] Based on the acquired body surface point cloud data and according to the three-point force principle, pressure zones are designed at the scoliosis, the contralateral hip and the armpit, and a pressure release zone is designed slightly to the lateral side, thereby designing the orthosis model.

[0020] Furthermore, the process of constructing the trunk-orthosis model includes:

[0021] By wrapping, repairing, adaptive meshing and Boolean operations, the overlapping contours of various parts in the three-dimensional model of the bone are deleted, and the surface of the three-dimensional model is repaired and optimized, and the various parts of the three-dimensional model and the orthosis model are assembled into a whole;

[0022] The model assembled as a whole is meshed, and the surfaces with contact and ligament attachment are marked, and finally exported as a finite element model.

[0023] Further, the finite element analysis software is set with boundary conditions and material properties of the orthosis, and uses only stretched springs or rod elements instead of ligaments to perform finite element static analysis;

[0024] The boundary conditions include: fixing the femurs on both sides, applying a pair of preload forces of equal magnitude and opposite directions parallel to the coronal axis on both sides of the orthosis opening to simulate the force of the strap on the orthosis.

[0025] Furthermore, the method adopts a sub-model method to perform topological optimization on the orthosis model in a topological optimization software;

[0026] The sub-model method comprises: converting the trunk-orthosis model into a separate orthosis model, and copying the loads received by the orthosis in the trunk-orthosis model into the separate orthosis model.

[0027] Furthermore, the hollow structure is any shape that is topologically connected, and the process of setting the hollow structure in the orthosis model includes: converting the three-dimensional coordinates of each point on the surface domain of the topologically optimized orthosis model into corresponding two-dimensional coordinates to obtain a 2D plane; arranging, moving, rotating and scaling the hollow structure in the optimized area of ​​the 2D plane in the form of a 2D image, and then mapping the points of the 2D plane to the 3D surface to achieve the setting of the hollow structure in the orthosis model;

[0028] The optimization software for the hollow structure includes MIMICS, C4D, MESHMIXER or ZBRUSH.

[0029] Furthermore, the design software of the orthosis model includes MIMICS, RODIN 4D or FREEFORM;

[0030] The export format of the finite element model is .cbd, .inp or .mphbin;

[0031] The finite element analysis software is ANSYS, ABAQUS, COMSOL or PROE;

[0032] The topology optimization software is TOSCA, OPTISTRUCT, ATOM module of ABAQUS or Topology Optimization module of ANSYS.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) The present invention assembles a three-dimensional model of the bone and an orthosis model, and then exports the result to a finite element model, performs finite element statics analysis using finite element analysis software, and then implements topology optimization in topology optimization software based on the orthosis model and the finite element statics analysis results, and sets the optimized area as a hollow structure. On the one hand, this scheme realizes the lightweight design of the additively manufactured scoliosis orthosis based on the finite element method; on the other hand, the topology optimization performed through the finite element statics analysis results ensures that the lightweight orthosis can ensure that the patient will not break or fail during wearing, and the overall structural cost is reduced, the lightweight design is implemented, and the structure is stable and reliable.

[0035] (2) The present invention achieves the lightness of the orthosis to the greatest extent, while meeting the mechanical properties of the orthosis and the requirements of additive manufacturing, and can greatly improve the comfort and wearing compliance of the brace, thereby maximizing the orthotic effect.

[0036] (3) The present invention can give full play to the advantage that the difficulty of additive manufacturing process is not affected by the shape of the product, while reducing the production and processing time, saving consumables, helping to reduce the economic burden on patients' families, and greatly improving the timeliness from design to application. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic flow chart of a method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis provided in an embodiment of the present invention;

[0038] Figure 2 A schematic diagram of a torso-orthosis three-dimensional model provided in an embodiment of the present invention;

[0039] Figure 3 A schematic diagram comparing the before and after effects of a lightweight design of an orthosis provided in an embodiment of the present invention;

[0040] Figure 4 It is a schematic diagram of a 2D image of a honeycomb hollow structure provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0041] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0043] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0044] In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, or are the directions or positional relationships in which the inventive product is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the present invention.

[0045] Example 1

[0046] like Figure 1 As shown, this embodiment provides a method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis, comprising the following steps:

[0047] S1: Scan and obtain the patient's CT data and body surface point cloud data, and save the patient's CT data and point cloud data in DICOM and STL formats;

[0048] In this embodiment, CT data is obtained by scanning with a computer tomography device, and body surface point cloud data is obtained by scanning with an optical scanner, and the scanning range at least includes the portion from 5 cm above the upper edge of the first thoracic vertebra to 20 cm below the greater trochanter of the femur.

[0049] S2: Extract the 3D model of the skeleton based on the CT data, and build a preliminary scoliosis orthosis model in combination with the body surface point cloud data; perform surface meshing on the 3D skeleton model, and then assemble it with the orthosis model to obtain the trunk-orthosis model; perform volume meshing on the trunk-orthosis model and export it as a finite element model;

[0050] The extraction process of the three-dimensional model of the skeleton is as follows:

[0051] Through grayscale measurement, threshold segmentation, region growing, multi-layer extraction and Boolean operation, individual vertebrae, ribs, costal cartilages, intervertebral discs, hip bones and femurs are extracted from CT data according to the human anatomical structure and force transmission relationship, thus obtaining a three-dimensional model of the skeleton.

[0052] The construction process of the orthosis model is as follows:

[0053] Based on the acquired body surface point cloud data and according to the three-point force principle, pressure zones are designed at the scoliosis, contralateral hip and armpit, and a pressure release zone is designed slightly behind the lateral side, thereby designing the orthosis model.

[0054] The process of constructing the trunk-orthosis model includes:

[0055] By wrapping, repairing, adaptive meshing and Boolean operations, the overlapping contours of various parts in the three-dimensional model of the bone are deleted, and the surface of the three-dimensional model is repaired and optimized, and the various parts of the three-dimensional model and the orthosis model are assembled into a whole;

[0056] The model assembled as a whole is meshed, and the surfaces with contact and ligament attachment are marked, and finally exported as a finite element model.

[0057] Orthosis design software includes but is not limited to MIMICS, RODIN4D, and FREEFORM. Finite element model export formats include but are not limited to .cbd, .inp, and .mphbin.

[0058] In this embodiment, the CT data is imported into MIMICS, the three-dimensional model of the skeleton is extracted, and the three-dimensional model of the skeleton is imported into 3-MATIC together with the body surface data to construct a traditional scoliosis orthosis. The surface mesh is divided while ensuring that there are no errors on the surface of the model, and then all the models including the skeleton, trunk and orthosis are assembled. The assembled trunk-orthosis model is meshed and exported to a format that can be recognized by the finite element analysis software.

[0059] The three-dimensional model of the skeleton can be transformed from two-dimensional to three-dimensional in the MIMICS software with the help of grayscale measurement, threshold segmentation, region growing, multi-layer extraction, and Boolean operations. According to the human anatomical structure and force transmission relationship, the vertebrae and intervertebral discs, ribs, costal cartilages, sternum, hip bone, and femur of the T1-S1 segment can be extracted.

[0060] The orthosis is designed based on the three-point force principle, with pressure zones designed at the scoliosis, the opposite hip and the armpit, and a pressure relief zone designed slightly behind the opposite side.

[0061] The trunk-orthosis finite element model can be used in 3-MATIC with the help of operation tools such as wrapping, repairing, adaptive meshing and Boolean operations to delete the overlapping contours of different 3D models in space, repair and optimize the triangular mesh of the model surface, and assemble all 3D models into a whole. The model is divided into 10-node volume meshes, the surfaces with contact and ligament attachment on the anatomical structure are marked, and the processed 3D model is exported in .cdb file format, such as Figure 2 shown.

[0062] S3: Import the finite element model into the finite element analysis software to perform finite element static analysis;

[0063] Preferably, the finite element analysis software is provided with boundary conditions and material properties of the orthosis, and uses only tensioned springs or rod elements instead of ligaments to perform finite element static analysis;

[0064] The boundary conditions include: fixing the femurs on both sides and applying a pair of preloads of equal magnitude and opposite directions parallel to the coronal axis on both sides of the orthosis opening to simulate the force of the strap on the orthosis.

[0065] The above-mentioned finite element analysis software includes but is not limited to ANSYS, ABAQUS, COMSOL, and PROE.

[0066] The above-mentioned ligament equivalent model includes but is not limited to a spring unit and a rod unit.

[0067] S4: inputting the orthosis model into the topology optimization software, mapping the finite element static analysis results obtained in step S3 to the inner surface of the orthosis model, and performing topology optimization on the orthosis by using the variable density method;

[0068] The above-mentioned topology optimization software includes but is not limited to TOSCA, OPTISTRUCT, ATOM module of ABAQUS, and Topology Optimization module of ANSYS.

[0069] Preferably, the orthosis model is topologically optimized in topology optimization software using a sub-model method;

[0070] The submodel method consists in converting the trunk-orthosis model into a separate orthosis model and copying the loads received by the orthosis in the trunk-orthosis model into the separate orthosis model.

[0071] In this embodiment, the topology optimization function of ANSYS workbench is used to perform topology optimization on the orthosis using the sub-model method.

[0072] S5: The optimized area in the orthosis model is set as a hollow structure, and the overall structure is optimized to obtain a lightweight orthosis; Figure 3 It is a schematic diagram showing the before and after effects of a lightweight orthosis.

[0073] The hollowing method is to convert the three-dimensional coordinates of each point on these surface domains into corresponding two-dimensional coordinates through UV unfolding. This unfolding process will transform the 3D surface domain into a 2D plane and this process is reversible. The hollow structure is spread on the above 2D plane in the form of a 2D image through arrangement, movement, rotation and scaling. The grayscale value of the 2D image is used to calculate the offset of the point mapped to the corresponding 3D surface position, thereby realizing the hollowing of the orthosis. Figure 4 It is a 2D image showing a honeycomb hollow structure.

[0074] The hollow structure may be any shape that is topologically connected. The optimization software for the hollow structure includes but is not limited to MIMICS, C4D, MESHMIXER, and ZBRUSH.

[0075] The overall structural optimization process includes removing sharp edges, filling holes, and smoothing curved surfaces of the orthosis after setting up the hollow structure, so as to obtain a lightweight orthosis that meets wearing and manufacturing requirements.

[0076] S6: The model data of the obtained lightweight orthosis is input into the finite element analysis software, and the finite element static analysis is performed to verify the mechanical properties; if it meets the preset mechanical property requirements, the final lightweight orthosis is obtained; if it does not meet the mechanical property requirements, steps S4-S6 are repeated until the lightweight orthosis can ensure that the patient will not break or fail during wearing.

[0077] The preferred specific embodiments of the present invention are described in detail above. It should be understood that a person skilled in the art can make many modifications and changes based on the concept of the present invention without creative work. Therefore, any technical solution that can be obtained by a person skilled in the art through logical analysis, reasoning or limited experiments based on the concept of the present invention on the basis of the prior art should be within the scope of protection determined by the claims.

Claims

1. A method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis, characterized in that: The following steps are involved: Scan and obtain the patient's CT data and body surface point cloud data; Extracting a three-dimensional model of the skeleton according to the CT data, and constructing a preliminary orthosis model of scoliosis in combination with the body surface point cloud data; performing surface meshing on the three-dimensional model of the skeleton, and then assembling it with the orthosis model to obtain a trunk-orthosis model; The trunk-orthosis model was volume meshed and exported as a finite element model; Import the finite element model into the finite element analysis software to perform finite element static analysis; The orthosis model is input into the topology optimization software, and the finite element static analysis results are mapped to the inner surface of the orthosis model, so as to perform topology optimization; The optimized area in the orthosis model is set as a hollow structure, and the overall structure is optimized to obtain a lightweight orthosis.

2. The method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis according to claim 1, characterized in that: The method further comprises: The model data of the obtained lightweight orthosis is input into the finite element analysis software for finite element static analysis to verify the mechanical properties; if it meets the preset mechanical performance requirements, the final lightweight orthosis is obtained; otherwise, the topology optimization software is used again for topology optimization.

3. The method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis according to claim 1, characterized in that: The CT data is acquired by scanning with a computer tomography device, and the body surface point cloud data is acquired by scanning with an optical scanner. The scanning range includes a portion from 5 cm above the upper edge of the first thoracic vertebra to 20 cm below the greater trochanter of the femur.

4. The method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis according to claim 1, characterized in that: The extraction process of the three-dimensional model of the skeleton is specifically as follows: Through grayscale measurement, threshold segmentation, region growing, multi-layer extraction and Boolean operation, individual vertebrae, ribs, costal cartilages, intervertebral discs, hip bones and femurs are extracted from CT data according to the human anatomical structure and force transmission relationship, thus obtaining a three-dimensional model of the skeleton.

5. The method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis according to claim 1, characterized in that: The construction process of the orthosis model is specifically as follows: Based on the acquired body surface point cloud data and according to the three-point force principle, pressure zones are designed at the scoliosis, the contralateral hip and the armpit, and a pressure release zone is designed slightly to the lateral side, thereby designing the orthosis model.

6. The method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis according to claim 1, characterized in that: The process of constructing the trunk-orthosis model includes: By wrapping, repairing, adaptive meshing and Boolean operations, the overlapping contours of various parts in the three-dimensional model of the bone are deleted, and the surface of the three-dimensional model is repaired and optimized, and the various parts of the three-dimensional model and the orthosis model are assembled into a whole; The model assembled as a whole is meshed, and the surfaces with contact and ligament attachment are marked, and finally exported as a finite element model.

7. The method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis according to claim 1, characterized in that: The finite element analysis software is set with boundary conditions and material properties of the orthosis, and uses a spring or rod element that is only stretched to replace the ligament, so as to perform a finite element static analysis; The boundary conditions include: fixing the femurs on both sides, applying a pair of preload forces of equal magnitude and opposite directions parallel to the coronal axis on both sides of the orthosis opening to simulate the force of the strap on the orthosis.

8. The method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis according to claim 1, characterized in that: The method adopts a sub-model method to perform topological optimization on the orthosis model in topological optimization software; The sub-model method comprises: converting the trunk-orthosis model into a separate orthosis model, and copying the loads received by the orthosis in the trunk-orthosis model into the separate orthosis model.

9. The method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis according to claim 1, characterized in that: The hollow structure is any shape that is topologically connected. The process of setting the hollow structure in the orthosis model includes: converting the three-dimensional coordinates of each point on the surface domain of the topologically optimized orthosis model into corresponding two-dimensional coordinates to obtain a 2D plane; arranging, moving, rotating and scaling the hollow structure in the optimized area of ​​the 2D plane in the form of a 2D image, and then mapping the points of the 2D plane to the 3D surface to achieve the setting of the hollow structure in the orthosis model; The optimization software for the hollow structure includes MIMICS, C4D, MESHMIXER or ZBRUSH.

10. The method for optimizing the lightweight structure of a scoliosis orthosis based on finite element analysis according to claim 1, characterized in that: The orthosis model design software includes MIMICS, RODIN 4D or FREEFORM; The export format of the finite element model is .cbd, .inp or .mphbin; The finite element analysis software is ANSYS, ABAQUS, COMSOL or PROE; The topology optimization software is TOSCA, OPTISTRUCT, ATOM module of ABAQUS or TopologyOptimization module of ANSYS.

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