Self-adaptive bionic cancellous bone defect prosthesis and design method thereof

Abstract

The invention discloses a self-adaptive bionic cancellous bone defect prosthesis and a design method thereof, and belongs to the technical field of medical prostheses, the prosthesis is composed of biological interface gradient microporous structure parts and a main body bionic truss supporting structure part, the biological interface gradient microporous structure parts are arranged at the two ends of the main body bionic truss supporting structure part, and the main body bionic truss supporting structure part is arranged on the main body bionic truss supporting structure part. The method is mainly used for reconstructing bone defects, bionically designing a truss part of a main body with consistent arrangement direction and form of human body bone trabecula through an established linear relation between CT gray value and bone density-elasticity modulus, adaptively matching mechanical conduction of a bone structure, reducing stress shielding effect, and improving bone defect reconstruction efficiency. Meanwhile, various complex mechanical working condition requirements of the prosthesis are met, the prosthesis failure risk is reduced, and the service life of the prosthesis is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of medical prostheses, and particularly relates to a self-adaptive bionic cancellous bone defect prosthesis and a design method thereof. Background Art

[0002] In China, there are approximately 4 million cases of large segment bone defects every year, mainly caused by high-energy injuries (such as high-altitude falls, traffic accidents, etc.) and pathological bone destruction (such as bone tumors, chronic osteomyelitis, etc.). Its treatment has always been a major challenge in orthopedic clinical practice. Currently, the mainstream treatment method is to use solid-structured titanium alloy prostheses for repair and reconstruction. However, the inherent elastic modulus of titanium alloy (110 GPa) is significantly higher than that of cortical bone (10 - 30 GPa), resulting in a serious stress shielding effect, and the bone absorption rate at the prosthesis-bone interface exceeds 35%. Therefore, reducing the elastic modulus of the prosthesis through porous designs such as micropores or trusses is the current main improvement solution. Currently, prosthesis designs mostly adopt homogenized porous structures or topology optimization methods based on finite element stress / volume response. Although the conventional homogeneous micropore design can significantly reduce elasticity, it faces insufficient mechanical strength, causing local mechanical mismatch. The porous structures designed by the topology optimization method based on finite element stress / volume response can meet the requirements of macroscopic mechanical strength. However, the existing stress / volume response optimization mode relies on the simulation of in vitro loading conditions and fails to reflect the in vivo dynamic mechanical conduction characteristics, resulting in deviations between the micropores or trusses of the prosthesis and the bone principal stress trajectory, hindering bone functional remodeling. Therefore, there is an urgent need to develop a new type of bone defect prosthesis with mechanical conduction matching that can meet the requirements of various complex mechanical conditions.

[0003] The patent document with the application number 202411381537.7 discloses a "design method for variable-density bone porous prostheses based on bone density distribution". The prostheses prepared by this method are microporous prostheses, belonging to small pores. If the elastic modulus is close to that of bone, it will inevitably lead to a decrease in strength; moreover, this method belongs to a cad modeling method. First, a large grid is made, and the micropores obtained by Boolean operations inside the prosthesis are made smaller at some positions, inevitably resulting in Boolean edge distortion. It is difficult for micropores to meet the mechanical strength while ensuring that the elastic modulus is close to that of bone.

[0004] As the cornerstone theory in the field of bone biomechanics, Wolff's law clearly states that there is a dynamic adaptive relationship between the morphological structure of bone tissue and the mechanical load distribution. Through the continuous remodeling process of bone resorption and bone deposition, parameters such as the arrangement direction of trabecular bone and the thickness of cortical bone are highly matched with the direction and magnitude of the principal stress. This law reveals that bone tissue regulates cell activity by sensing local stress stimuli, forms a microscopic structure adapted to the mechanical environment, and the trabecular bone grows directionally along the principal stress direction, forming an efficient mechanical conduction path to achieve the optimal balance between structural lightweight and load-bearing performance. Therefore, the bone tissue structure is the most reliable bionic reference for prosthesis design.

[0005] There is sufficient evidence to confirm that there is a linear relationship between CT gray values and bone density. Therefore, by extracting the host bone density gradient field from CT gray values, the result of the accumulation of historical mechanical stimuli in bone tissue can be reflected, and the dual-drive mechanism of "anatomical structure - mechanical environment" can be jointly reflected. Therefore, by establishing a cross-scale mapping model of gray value - elastic modulus - stress stimulation, the engineering expression of Wolff's law can be realized, making up for the deficiencies in current prosthesis design.

[0006] In summary, a self-adaptive bionic cancellous bone defect prosthesis and its design method can meet the requirements of various complex mechanical conditions of the prosthesis, reduce the risk of prosthesis failure, and extend the service life of the prosthesis. Summary of the Invention

[0007] Aiming at the deficiencies of existing bone defect prostheses and their design technologies, the present invention proposes a self-adaptive bionic cancellous bone defect prosthesis and its design method, which is mainly used for reconstructing bone defects. By establishing the linear relationship between CT gray values and bone density - elastic modulus, the truss part of the main body with the same arrangement direction and shape as human trabecular bone is bionically designed, which can adaptively match the mechanical conduction of bone structure, reduce the stress shielding effect, and at the same time match the requirements of various complex mechanical conditions of the prosthesis, reduce the risk of prosthesis failure, and extend the service life of the prosthesis.

[0008] A self-adaptive bionic cancellous bone defect prosthesis includes a biological interface gradient microporous structure part and a main body bionic truss support structure part, wherein the biological interface gradient microporous structure part is arranged at both ends of the main body bionic truss support structure part.

[0009] The biological interface gradient microporous structure part and the main body bionic truss support structure part are bionic trabecular bone structures or bionic glass sponge structures or Voronoi diagrams or TPMS structures.

[0010] The material of the bone defect prosthesis is selected as Ti6Al4V.

[0011] A design method of a self-adaptive bionic cancellous bone defect prosthesis, the bone defect prosthesis is integrally formed by 3D printing, and includes the following four steps.

[0012] Step 1: Construct a three-dimensional anatomical model of the bone defect area according to the patient's CT data, including the following steps: (1) Collect the CT data of the bone defect patient, and import the CT data into a medical three-dimensional reconstruction software in Dicom format, such as Mimics; (2) Reconstruct the three-dimensional model of the bone in the medical three-dimensional reconstruction software, divide the defect area, and export its STL model; (3) Import the segmented defective STL model into 3D modeling software such as Rhino, Solidwork, Magics, etc., and design the 3D structure of the prosthesis. (4) Divide the 3D structure of the prosthesis into a main body part and a bone interface connection part. The main body part prepares for the subsequent truss structure design, and the bone interface connection part prepares for the subsequent microporous structure design.

[0013] Step 2: Mirror the contralateral side, extract the spatial coordinate points of the model on the healthy side and their corresponding CT gray value distribution matrix, including the following steps: (1) Divide the exported main body part into volume elements and import the volume element structure into Mimics software. (2) Use the mirror tool to mirror the volume element structure to the healthy side and fit and match the contralateral bone structure. (3) Assign parameters to the volume elements according to the CT gray values and export the point cloud data after assignment. (4) Import the volume element information after assignment into post-processing software such as Matlab software, and extract the three-dimensional coordinates of the corresponding spatial coordinate points and the corresponding gray value information.

[0014] Step 3: Based on the gray value - bone density - elastic modulus mapping relationship model, dynamically adjust the geometric parameters of the truss elements through the gradient parameter matching algorithm, including the spatial density distribution, beam diameter gradient change, and porosity distribution. Use the optimization iteration algorithm to generate a mechanically conductive adaptive truss structure that matches the elastic modulus distribution of the host bone, including the following steps: (1) Based on the existing gray value - bone density - bone elastic modulus assignment formula, establish a mapping relationship model, and select a suitable assignment formula according to the different elastic moduli of the bone parts where the bone defects are located. (2) According to the corresponding formulas of the existing truss structure spatial density distribution, beam diameter gradient change, and porosity change and the elastic modulus of the titanium alloy truss structure, establish a gray value - bone density - bone elastic modulus - titanium alloy elastic modulus matching response. (3) Import the spatial coordinate points of the volume elements and their gray value data information into calculation and design software such as ntop, Grasshopper, Matlab, etc., and establish the connection between the spatial coordinate points of the volume elements and their gray value data and the truss design. (4) Use computer language to automatically generate the main truss structure based on the gray value change.

[0015] The change in truss density is affected by the gray value. High-density trusses are selected in areas with high gray values, and low-density trusses are selected in areas with low gray values. Therefore, the relationship of CT gray value - bone density - elastic modulus - truss density is generated.

[0016] Step 4. Set the interfacial gradient micropores according to the change of the interfacial gray value, and integrate the optimized truss structure with the interfacial gradient micropore structure to output the final prosthesis model, including the following steps: (1) Import the bone interface connection part into prosthesis design software, such as Rhino, Solidwork, Magics, etc., and match it with the main truss part; (2) Extract the spatial coordinate points and their gray values of the prosthesis-bone connection interface. On the basis of Steps 2 and 3, set the gradient micropore structure based on the gray value response to realize the change of the micropore structure parameters with the gray value; (3) In the prosthesis design software, integrate the bone interface connection micropore part and the truss part together by means of Boolean addition operation to complete the design of the prosthesis shape; (4) Set the screw channels and auxiliary bone plates according to the fixation requirements of the prosthesis at different positions. Among them, the pelvic prosthesis needs to add a bionic axial joint fixation on the dorsal side of the sacrum, the long bone shaft prosthesis needs to add bilateral bone plates and reserve the intramedullary needle channel, and the proximal / distal end of the long bone needs to add bone plates and reserve the prosthesis stem channel.

[0017] The self-adaptive bionic cancellous bone defect prosthesis manufactured by 3D printing using the above method is connected to the human body's own pelvis through screws.

[0018] Advantages of the present invention: 1. The present invention is driven by CT gray value design. Through the established cross-scale mapping model of gray value-bone density-elastic modulus, the truss structure of the prosthesis is dynamically matched with the mechanical conduction characteristics of the host bone. On the premise of ensuring strength, the stress shielding effect of traditional titanium alloy prostheses can be significantly reduced.

[0019] 2. The main bionic truss structure of the present invention simulates the mechanical conduction path of trabecular bone. Combined with the interfacial gradient micropore structure, it takes into account both the macroscopic bearing strength and the microscopic bone ingrowth requirements, and solves the problems of insufficient mechanics of homogeneous porous structures or deviation of topological optimization from the in-vivo mechanical environment.

[0020] 3. The present invention mirrors the healthy side bones based on the patient's CT data, extracts the three-dimensional coordinates and gray value distribution, realizes individualized prosthesis design, and accurately matches the anatomical shape and mechanical environment.

[0021] 4. The present invention provides a new type of bionic prosthesis that conforms to the characteristics of the human mechanical conduction distribution and its design method, which can meet the mechanical requirements of bone defect prostheses under complex loading conditions and improve their interfacial bone integration ability. Description of the Drawings

[0022] Figure 1 It is the overall design pattern diagram of the embodiment of the present invention.

[0023] Figure 2 Schematic diagram of the overall structure of an embodiment of the present invention.

[0024] Figure 3 Schematic diagram of the overall installation of an embodiment of the present invention.

[0025] Figure 4 Schematic diagram of the structures of different density trusses of an embodiment of the present invention.

[0026] Figure 5 Schematic diagram of the Thiessen polygon for the selection of the microporous structure of an embodiment of the present invention.

[0027] Figure 6 Schematic diagram of the design flow of an embodiment of the present invention. Detailed implementation manners

[0028] Please refer to Figures 1 to 6 as shown, which is an embodiment of the present invention.

[0029] A self-adaptive bionic cancellous bone defect prosthesis, comprising a biological interface gradient microporous structure part 1 and a main body bionic truss support structure part 2, wherein the biological interface gradient microporous structure part 1 is arranged at both ends of the main body bionic truss support structure part 2.

[0030] The biological interface gradient microporous structure part 1 and the main body bionic truss support structure part 2 are of Thiessen polygon structure. The material of the bone defect prosthesis is selected as Ti6Al4V.

[0031] The self-adaptive bionic cancellous bone defect prosthesis described in this embodiment is designed by 3D printing integrated molding, and includes the following four steps.

[0032] Step 1: Construct a three-dimensional anatomical model of the bone defect area according to the patient's CT data, including the following steps: (1) Collect the CT data of the bone defect patient, and import the CT data into the Mimics medical three-dimensional reconstruction software in Dicom format; (2) Reconstruct the three-dimensional model of the bone in the Mimics medical three-dimensional reconstruction software, divide the defect area, and export its STL model; (3) Import the divided defect STL model into the three-dimensional modeling software Solidwork to design the three-dimensional structure of the prosthesis; (4) Divide the three-dimensional structure of the prosthesis into a main body part and a bone interface connection part, wherein the main body part is prepared for the subsequent truss structure design, and the bone interface connection part is prepared for the subsequent microporous structure design.

[0033] Step 2: Mirror the contralateral side, and extract the spatial coordinate points on the healthy side of the model and their corresponding CT gray value distribution matrix, including the following steps: (1)Divide the exported main part into volume elements and import the volume element structure into Mimics software; (2)Use the mirror tool to mirror the volume element structure to the healthy side and fit and match the bone structure on the contralateral side; (3)Assign parameters to the volume elements according to the CT gray values and export the point cloud data after assignment; (4)Import the volume element information after assignment into the post-processing Matlab software to extract the three-dimensional coordinates of the corresponding spatial coordinate points and the corresponding gray value information.

[0034] Step 3: Based on the gray value-bone density-elastic modulus mapping relationship model, dynamically adjust the geometric parameters of the truss elements through the gradient parameter matching algorithm, including the spatial density distribution, beam diameter gradient change, and porosity distribution. Use the optimization iteration algorithm to generate a mechanically conductive adaptive truss structure that matches the elastic modulus distribution of the host bone, including the following steps: (1)Based on the existing gray value-bone density-bone elastic modulus assignment formula, establish a mapping relationship model and select a suitable assignment formula according to the different elastic moduli of the bone defect location; (2)Based on the corresponding formulas of the existing truss structure spatial density distribution, beam diameter gradient change, and porosity change and the elastic modulus of the titanium alloy truss structure, establish a gray value-bone density-bone elastic modulus-titanium alloy elastic modulus matching response; (3)Import the volume element spatial coordinate points and their gray value data information into the Matlab calculation and design software and establish the connection between the volume element spatial coordinate points and their gray value data and the truss design; (4)Use computer language to automatically generate the main truss structure based on the gray value change.

[0035] The change in truss density is affected by the gray value. High-density trusses are selected in areas with high gray values, and low-density trusses are selected in areas with low gray values. Therefore, the relationship of CT gray value - bone density - elastic modulus - truss density is generated.

[0036] Step 4: Set the interface gradient micropores according to the change in interface gray value, integrate the optimized truss structure with the interface gradient micropore structure, and output the final prosthesis model, including the following steps: (1)Import the bone interface connection part into the prosthesis design software Rhino and match it with the main truss part; (2)Extract the spatial coordinate points and their gray values of the prosthesis-bone connection interface. On the basis of steps 2 and 3, set the gradient micropore structure based on the gray value response to realize the change of micropore structure parameters with the gray value; (3) In the prosthesis design software, the bone interface connecting the microporous part and the truss part is integrated together by means of Boolean addition operation to complete the design of the prosthesis shape; (4) According to the fixation requirements of prostheses at different positions, screw channels and auxiliary bone plates are set. Among them, the pelvic prosthesis needs to add a bionic axial joint fixation on the dorsal side of the sacrum, the long bone shaft prosthesis needs to add bilateral bone plates and reserve an intramedullary needle channel, and the proximal / distal end of the long bone needs to add a bone plate and reserve a prosthesis stem channel.

[0037] The self-adaptive bionic cancellous bone defect prosthesis fabricated by 3D printing using the above method is connected to the human own pelvis through screws 3.

[0038] The truss adopted in the present invention is a large pore, which thickens the inner beam of the main part of the bracket. On the outer shape of the prosthesis structure, a truss prosthesis is generated according to the gray value - elastic modulus - pore density and beam diameter algorithm; the truss is a large pore, and by increasing the diameter of the main beam, it can better ensure that the elastic modulus is reduced to be close to that of bone while meeting the mechanical properties.

Claims

1. A self-adaptive bionic cancellous bone defect prosthesis, characterized in that: It includes a biological interface gradient microporous structure part (1) and a main body bionic truss support structure part (2), wherein the biological interface gradient microporous structure part (1) is arranged at both ends of the main body bionic truss support structure part (2).

2. The self-adaptive bionic cancellous bone defect prosthesis according to claim 1, characterized in that: The biological interface gradient microporous structure part (1) and the main body bionic truss support structure part (2) are bionic trabecular bone structures or bionic glass sponge structures or Voronoi diagrams or TPMS structures.

3. An adaptive bionic cancellous bone defect prosthesis according to claim 1, characterized in that On: The material of the bone defect prosthesis is selected as Ti6Al4V.

4. The design method of a self-adaptive bionic cancellous bone defect prosthesis according to claim 1, characterized in that: The bone defect prosthesis is a 3D printing integrated molding design, including the following steps: Step 1: Construct a three-dimensional anatomical model of the bone defect area according to the patient's CT data; Step 2: Mirror the contralateral side, and extract the spatial coordinate points and their corresponding CT gray value distribution matrix on the healthy side of the model; Step 3: Based on the gray value-bone density-elastic modulus mapping relationship model, dynamically adjust the geometric parameters of the truss unit through the gradient parameter matching algorithm, including the spatial density distribution, beam diameter gradient change and porosity distribution, and use the optimization iteration algorithm to generate a mechanical conduction adaptive truss structure that matches the elastic modulus distribution of the host bone; Step 4: Set the interface gradient micropores according to the change of the interface gray value, integrate the optimized truss structure and the interface gradient microporous structure, and output the final prosthesis model.

5. The design method of a self-adaptive bionic cancellous bone defect prosthesis according to claim 4, characterized in that: The said Step 1 includes the following steps: (1) Collect the CT data of the bone defect patient, and import the CT data into the medical three-dimensional reconstruction software in Dicom format, (2) Reconstruct the three-dimensional model of the bone in the medical three-dimensional reconstruction software, divide the defect area, and export its STL model; (3) Import the divided defect STL model into the three-dimensional modeling software, and design the three-dimensional structure of the prosthesis; (4) Divide the three-dimensional structure of the prosthesis into the main body part and the bone interface connection part, wherein the main body part is prepared for the subsequent truss structure design, and the bone interface connection part is prepared for the subsequent microporous structure design.

6. The design method of a self-adapting bionic cancellous bone defect prosthesis according to claim 4, characterized in that: The said Step 2 includes the following steps: (1) Perform volume element division on the exported main body part, and import the volume element structure into the Mimics software; (2) Use the mirror tool to mirror the volume element structure to the healthy side and fit and match the contralateral bone structure; (3) Assign parameters to the volume elements according to the CT gray value, and export the point cloud data after assignment; (4) Import the information of the volume elements after assignment into the post-processing software, and extract the three-dimensional coordinates of the corresponding spatial coordinate points and the corresponding gray value information.

7. The design method of a self-adapting bionic cancellous bone defect prosthesis according to claim 4, characterized in that: The said Step 3 includes the following steps: (1) Based on the existing gray value-bone density-bone elastic modulus assignment formula, establish a mapping relationship model, and select a suitable assignment formula according to the different elastic moduli of the bones where the bone defects are located; (2) According to the corresponding formulas of the existing truss structure spatial density distribution, beam diameter gradient change and porosity change and the elastic modulus of the titanium alloy truss structure, establish a gray value-bone density-bone elastic modulus-titanium alloy elastic modulus matching response; (3) Import the spatial coordinate points of the volume elements and their grayscale value data information into the computational design software, and establish the connection between the spatial coordinate points of the volume elements and their grayscale value data and the truss design; (4) Use computer language to automatically generate the main truss structure based on the change of grayscale value.

8. A design method of a self-adaptive bionic cancellous bone defect prosthesis according to claim 4, characterized in that: The fourth step described above includes the following steps: (1) Import the bone interface connection part into the prosthesis design software and match it with the main truss part; (2) Extract the spatial coordinate points and their grayscale values of the prosthesis-bone connection interface. On the basis of steps two and three, set the gradient microporous structure based on the grayscale value response to realize the change of the microporous structure parameters with the grayscale value; (3) In the prosthesis design software, integrate the microporous part of the bone interface connection and the truss part together by means of Boolean addition operation to complete the design of the prosthesis shape; (4) Set the screw channels and auxiliary bone plates according to the fixation requirements of the prosthesis at different positions. Among them, the pelvic prosthesis needs to add the bionic axial joint fixation on the dorsal side of the sacrum, the long bone shaft prosthesis needs to add bilateral bone plates and reserve the intramedullary needle channel, and the long bone near / far end needs to add bone plates and reserve the prosthesis stem channel.

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