A method for manufacturing a fusion device with a variable elastic structure based on topology optimization technology

Abstract

The present invention relates to a method for manufacturing a fusion device with a variable elastic structure based on topological optimization technology, and the manufacturing method comprises the following steps: 1) constructing a prediction model of a neural network of bone elastic modulus; 2) designing a pore structure for bone growth based on the prediction model and using bionics, and selecting a pore size suitable for bone growth; 3) using 3D design software to identify and extract fusion device structural features; 4) step 3) optimizing SLM process parameters; 5) obtaining intervertebral disc data through CT, using medical titanium alloy as a basic raw material and a mixture of a degradable polymer material and osteogenic active powder as an auxiliary raw material, and using 3D printing to load SLM process parameters to complete a fusion device body structure with a hollow three-dimensional connected structure; 6) covering the surface of the fusion device body with a dynamic liquid crystal elastic material so that it can be completely fitted with a vertebral end plate; 7) grinding and polishing the parts obtained in step 6) to obtain the required parts.

Description

Technical Field

[0001] The present invention relates to the technical field of intervertebral fusion devices, and in particular to a method for manufacturing a fusion device with a variable elastic structure based on topological optimization technology. Background Art

[0002] In 1988, Bagby proposed the use of a hollow, porous, stainless steel interbody fusion cage for the treatment of equine cervical spondylotic myelopathy. This fusion technique was soon adapted for human use and was approved by the U.S. Food and Drug Administration in 1996 for the treatment of certain spinal disorders. Since then, interbody fusion cages have evolved into a very successful fusion method that is characterized by less postoperative pain, shorter hospital stays, fewer complications, and higher fusion rates than bone graft fusion alone.

[0003] Over the past two decades, the design and materials of interbody fusion cages have changed significantly. In the mid-1990s, threaded titanium cylindrical screw cages, often with autologous bone grafts, achieved higher fusion rates than bone grafts and non-threaded interbody fusions. However, it was soon discovered that threaded screw cages had a high rate of subsidence. Since the beginning of the 21st century, non-threaded titanium or peek interbody fusion cage designs have become more common. However, the problem of cage subsidence and non-fusion remains a major problem.

[0004] Metal additive manufacturing is a new type of forming technology, involving high technologies in multiple disciplines such as optics, mechanics, electricity, materials, detection and control. It is a new processing and manufacturing technology that cannot be completed by traditional manufacturing methods, and it is a high technology that is supported and promoted by the state. At present, many research institutes at home and abroad, such as Tsinghua University, Huazhong University of Science and Technology, MicroFab Commercial Company in the United States, and University of Toronto in Canada, mainly focus on the forming mechanism, drive mode selection and thermal state analysis of the metal additive manufacturing process, etc., for the research of metal additive manufacturing technology. However, there are few clinical studies on the use of additive manufacturing parts after the intervertebral fusion cage with variable elastic structure is designed using topology optimization technology. Summary of the invention

[0005] The purpose of the present invention is to provide a method for manufacturing a fusion device with a variable elastic structure based on topology optimization technology to solve the problems raised in the above background technology.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The method for manufacturing a fusion device with a variable elastic structure based on topological optimization technology is based on topological optimization, using medical titanium alloy as the basic raw material, a mixture of degradable polymer materials and osteogenic active powder as the auxiliary raw material, using 3D printing to form the fusion device body, and covering the surface of the fusion device body with a liquid crystal elastic film to control the application elastic modulus of the intervertebral fusion device to be the same as the measured elastic modulus of the human spine;

[0008] The manufacturing method comprises the following steps:

[0009] 1) Build a database of osteoporotic and non-osteoporotic people; use Python machine learning to build a neural network prediction model for bone elastic modulus;

[0010] 2) Design the pore structure for bone growth based on the prediction model and using bionics, and select the pore size suitable for bone growth;

[0011] 3) Using 3D design software to identify and extract the structural features of the fusion device, using the seed diffusion method to determine the connection relationship between all the suspended triangular facets to be supported, and using the normal distribution method to obtain the main structure of the fusion device to be printed;

[0012] 4) After step 3), the mechanical properties and solidification heat transfer mechanism of the obtained intervertebral fusion cage structure characteristics are analyzed to optimize the SLM process parameters;

[0013] 5) The intervertebral disc data was obtained through CT, and the fusion device body structure with a hollow three-dimensional connected structure was completed by using medical titanium alloy as the basic raw material and a mixture of degradable polymer materials and osteogenic active powder as the auxiliary raw material, and 3D printing and loading SLM process parameters;

[0014] 6) The surface of the fusion device is covered with dynamic liquid crystal elastic material so that it can fit completely with the vertebral endplate;

[0015] 7) Grinding and polishing the parts obtained in step 6) to obtain the desired parts.

[0016] Preferably, in step 5, the manufacturing process includes a laser, metal powder, a substrate and a formed part, the substrate is fixed on the 3D displacement platform, and the laser is located directly above the substrate.

[0017] A layer of metal powder is evenly spread on the base plate of the forming cylinder using a powder spreading roller. The computer controls the laser beam to perform selective laser melting on the current layer. After the molten metal powder cools and solidifies, the processing platform is lowered by one unit height, and the powder feeding platform is raised by one unit height. The powder spreading roller re-spreads the metal powder on the processed layer, and the laser beam begins to scan a new layer, and this process is repeated layer by layer until the entire part is formed.

[0018] Preferably, a topology optimization method is used to realize a variable elastic structure with different pores to adapt to people with different bone densities.

[0019] Preferably, the base material and the material of the required part may be the same or different.

[0020] Preferably, the database contains age, gender, height, weight, BMI, and bone density T-value data of osteoporotic and non-osteoporotic people.

[0021] Preferably, the intervertebral fusion cage is designed based on the bone density of different patients and utilizes bionics to achieve a pore structure and a pore size suitable for bone growth.

[0022] Preferably, the material of the intervertebral fusion cage may be a medical titanium alloy, or may be a peek material, or a material suitable for human body implantation which is a combination of a medical titanium alloy and a peek material.

[0023] The invention uses a mixture of degradable polymer material and osteogenic active powder as auxiliary raw material to achieve good biocompatibility and the ability to induce bone ingrowth.

[0024] The thickness of the liquid crystal elastic film can be controlled according to the measured elastic modulus of the human spine, so as to control the applied elastic modulus formed by the intervertebral fusion device to be the same as the measured elastic modulus of the human spine. Therefore, additive manufacturing of customized fusion devices with different elastic moduli can be achieved, and subsequent processing processes can be omitted.

[0025] This technology can realize additive manufacturing of medical titanium alloys and PEEK. If medical titanium alloys are used, after the forming is completed, the metal powder material that has not been used up in the forming process can be recycled and used in the next forming process, thus reducing the waste of forming materials and improving material utilization.

[0026] The method for designing an intervertebral fusion device with a variable elastic structure using topology optimization technology described in the present invention adjusts the laser power, scanning speed, etc. according to the structure of the required parts during processing of the required parts, and adjusts the scanning speed and scanning path during additive manufacturing according to the aperture of the required parts, thereby effectively improving the forming accuracy of the parts, accelerating the forming rate of the parts, and effectively improving the quality of the products. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 , Figure 2 It is a schematic diagram of the structure of different orientations of the present invention. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the accompanying drawings. Figure 1 to Figure 2 .

[0029] The present invention provides a method for manufacturing a fusion device with a variable elastic structure based on topological optimization technology. The method is based on topological optimization, using medical titanium alloy as a basic raw material, using a mixture of degradable polymer materials and osteogenic active powder as an auxiliary raw material, using 3D printing to form a fusion device body, and coating the surface of the fusion device body with a liquid crystal elastic film to control the application elastic modulus of the intervertebral fusion device to be the same as the actual measured elastic modulus of the human spine;

[0030] After the intervertebral fusion device with variable elastic structure is designed by topology optimization technology, it is manufactured by selective laser melting (SLM) technology. The fusion device solid model is designed by computer three-dimensional modeling software, and then the three-dimensional model is sliced ​​and layered by slicing software to obtain a series of cross-sectional contour data. Appropriate process parameters are input, and the laser scanning path is designed based on the contour data. The computer control system controls the laser beam to melt the metal powder layer by layer according to the designed path, and the metal parts are formed by stacking layer by layer. Before the laser beam scanning starts, a very thin layer of metal powder is evenly spread on the base plate of the forming cylinder by using a powder spreading roller. The computer controls the laser beam to selectively laser melt the current layer. After the molten metal powder is cooled and solidified, the processing platform is lowered by one unit height, and the powder feeding platform is raised by one unit height. The powder spreading roller re-spreads the metal powder on the processed layer, and the laser beam begins to scan a new layer, and the layers are stacked in this way until the entire part is formed. In this way, the forming process can be free from the structural restrictions of the three-dimensional model, and a model of any complex shape can be directly formed.

[0031] Specifically, the manufacturing method comprises the following steps:

[0032] 1) Build a database of osteoporotic and non-osteoporotic people; use Python machine learning to build a neural network prediction model for bone elastic modulus;

[0033] 2) Design the pore structure for bone growth based on the prediction model and using bionics, and select the pore size suitable for bone growth;

[0034] 3) Using 3D design software to identify and extract the structural features of the fusion device, using the seed diffusion method to determine the connection relationship between all the suspended triangular facets to be supported, and using the normal distribution method to obtain the main structure of the fusion device to be printed;

[0035] 4) After step 3), the mechanical properties and solidification heat transfer mechanism of the obtained intervertebral fusion cage structure characteristics are analyzed to optimize the SLM process parameters;

[0036] 5) The intervertebral disc data was obtained through CT, and the fusion device body structure with a hollow three-dimensional connected structure was completed by using medical titanium alloy as the basic raw material and a mixture of degradable polymer materials and osteogenic active powder as the auxiliary raw material, and 3D printing and loading SLM process parameters;

[0037] 6) The surface of the fusion device is covered with dynamic liquid crystal elastic material so that it can fit completely with the vertebral endplate;

[0038] 7) Grinding and polishing the parts obtained in step 6) to obtain the desired parts.

[0039] Preferably, in step 5, the manufacturing process includes a laser 1, metal powder 2, a substrate 3 and a formed part 4, the substrate is fixed on the 3D displacement platform, and the laser is located directly above the substrate.

[0040] A layer of metal powder is evenly spread on the base plate of the forming cylinder using a powder spreading roller. The computer controls the laser beam to perform selective laser melting on the current layer. After the molten metal powder cools and solidifies, the processing platform is lowered by one unit height, and the powder feeding platform is raised by one unit height. The powder spreading roller re-spreads the metal powder on the processed layer, and the laser beam begins to scan a new layer, and this process is repeated layer by layer until the entire part is formed.

[0041] Preferably, a topology optimization method is used to realize a variable elastic structure with different pores to adapt to people with different bone densities.

[0042] Preferably, the base material and the material of the required part may be the same or different.

[0043] Preferably, the database contains age, gender, height, weight, BMI, and bone density T-value data of osteoporotic and non-osteoporotic people.

[0044] Preferably, the intervertebral fusion cage is designed based on the bone density of different patients and utilizes bionics to achieve a pore structure and a pore size suitable for bone growth.

[0045] Preferably, the material of the intervertebral fusion cage may be a medical titanium alloy, or may be a peek material, or a material suitable for human body implantation which is a combination of a medical titanium alloy and a peek material.

[0046] The present invention has the following beneficial effects: (1) Personalization and customization: A digital three-dimensional model is established in a computer and imported into a laser selective melting device for processing and forming, without being restricted by different processes. This technology can realize the additive manufacturing of fusion devices with good biocompatibility, the ability to induce bone ingrowth, and different elastic moduli, and eliminates the need for subsequent processing. (2) A wide variety of formable materials: In theory, as long as the metal can be made into powder, the metal powder can be melted by adjusting the appropriate laser power. This technology can realize the additive manufacturing of medical titanium alloys. (3) High material utilization rate: The material consumption is basically the same as the material required for the final molded part. After the molding is completed, the metal powder material that has not been used up in the molding process can be recycled and used in the next molding, thereby reducing the waste of molding materials and improving the material utilization rate. (4) Rapidity: The terminal parts can be directly molded at one time, or can be directly used with only a small amount of simple processes such as sandblasting, polishing or heat treatment. In the production process, the mold can be opened to directly form the sample, which greatly shortens the product development cycle and saves a lot of time and cost. Therefore, it can be used immediately, reducing the casualty rate of the wounded during transportation. It can be used not only in hospitals with medical qualifications, but also in field hospitals for the treatment of the wounded. (5) Good mechanical properties. The density of the molded part can be close to 100%. The metal powder is melted by the energy of the high-energy laser beam and then rapidly solidified. The microstructure of the molded part is mostly fine grains. Therefore, the internal structure of the molded part is uniform, and the mechanical properties are better than those of castings, reaching the level of forgings.

[0047] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. The above is only a preferred implementation of the present invention. It should be pointed out that due to the limitations of textual expression and the objective existence of infinite specific structures, ordinary technicians in this technical field can make several improvements, modifications or changes without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner; these improvements, modifications, changes or combinations, or the direct application of the inventive concept and technical solution to other occasions without improvement, should be regarded as the protection scope of the present invention.

Claims

1. A method for manufacturing a fusion device with a variable elastic structure based on topology optimization technology, characterized in that: It is based on topological optimization and uses medical titanium alloy as the basic raw material, a mixture of degradable polymer materials and osteogenic active powder as the auxiliary raw material, and adopts 3D printing to form the fusion device body. A liquid crystal elastic film is coated on the surface of the fusion device body to control the application elastic modulus of the intervertebral fusion device to be the same as the measured elastic modulus of the human spine. The manufacturing method comprises the following steps: 1) Build a database of osteoporotic and non-osteoporotic people; use Python machine learning to build a neural network prediction model for bone elastic modulus; 2) Design the pore structure for bone growth based on the prediction model and using bionics, and select the pore size suitable for bone growth; 3) Using 3D design software to identify and extract the structural features of the fusion device, using the seed diffusion method to determine the connection relationship between all the suspended triangular facets to be supported, and using the normal distribution method to obtain the main structure of the fusion device to be printed; 4) After step 3), the mechanical properties and solidification heat transfer mechanism of the obtained intervertebral fusion cage structure characteristics are analyzed to optimize the SLM process parameters; 5) The intervertebral disc data was obtained through CT, and the fusion device body structure with a hollow three-dimensional connected structure was completed by using medical titanium alloy as the basic raw material and a mixture of degradable polymer materials and osteogenic active powder as the auxiliary raw material, and 3D printing and loading SLM process parameters; 6) The surface of the fusion device is covered with dynamic liquid crystal elastic material so that it can fit completely with the vertebral endplate; 7) Grinding and polishing the parts obtained in step 6) to obtain the desired parts.

2. The method for manufacturing a fusion device with a variable elastic structure based on topology optimization technology according to claim 1, characterized in that: In step 5, the manufacturing process includes a laser, metal powder, a substrate and a formed part. The substrate is fixed on the 3D displacement platform, and the laser is located directly above the substrate. A layer of metal powder is evenly spread on the base plate of the forming cylinder using a powder spreading roller. The computer controls the laser beam to perform selective laser melting on the current layer. After the molten metal powder cools and solidifies, the processing platform is lowered by one unit height, and the powder feeding platform is raised by one unit height. The powder spreading roller re-spreads the metal powder on the processed layer, and the laser beam begins to scan a new layer, and this process is repeated layer by layer until the entire part is formed.

3. The method for manufacturing a fusion device with a variable elastic structure based on topology optimization technology according to claim 1, characterized in that: The topology optimization method is used to realize variable elastic structures with different pores to adapt to people with different bone densities.

4. The method for manufacturing a fusion device with a variable elastic structure based on topology optimization technology according to claim 1, characterized in that: The base material and the material of the desired part can be the same or different.

5. The method for designing an intervertebral fusion cage with a variable elastic structure using topology optimization technology according to claim 3, characterized in that: The database contains age, gender, height, weight, BMI, and bone density T-value data of osteoporotic and non-osteoporotic people.

6. The method for designing an intervertebral fusion cage with a variable elastic structure using topology optimization technology according to claim 1, characterized in that: The intervertebral fusion cage is designed based on the bone density of different patients and utilizes bionics to achieve a pore structure and a pore size suitable for bone growth.

7. The method for designing an intervertebral fusion cage with a variable elastic structure using topology optimization technology according to claim 1, characterized in that: The material of the intervertebral fusion cage may be a medical titanium alloy, or may be a peek material, or a material suitable for human body implantation which is a combination of a medical titanium alloy and a peek material.

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