A porous radial head prosthesis design method and system

Abstract

The present invention provides a method for designing a porous radial capitellum prosthesis, comprising obtaining a three-dimensional model of the radial capitellum prosthesis; establishing a mainstream cell structure based on the three-dimensional model of the radial capitellum prosthesis to obtain a finite element model of the porous radial capitellum prosthesis; establishing a virtual mechanical test bench in ABAQUS for calculation and comparison to obtain a new cell with the best current mechanical performance; and further modifying the finite element model of the porous radial capitellum prosthesis based on the obtained new cell; establishing a relationship between pore size, porosity, and cell size; and setting node tolerances on the modified finite element model of the porous radial capitellum prosthesis based on the relationship between pore size, porosity, and cell size to generate a porous radial capitellum prosthesis with coincident inner and outer nodes, and then outputting the resultant porous radial capitellum prosthesis after physical processing. Implementation of the present invention can ensure structural strength while increasing pore size and decreasing porosity, effectively reduce the material equivalent elastic modulus, and improve shock absorption performance.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a design method and system for a porous radial head prosthesis. Background Art

[0002] Radial head fractures are a common type of elbow fracture, accounting for approximately 17%-19% of elbow fractures and 3% of total body fractures. Radial head replacement is the preferred treatment option for complex Mason type III and IV comminuted radial head fractures, particularly those associated with medial collateral ligament injury.

[0003] The microporous structure of porous titanium alloy not only provides sufficient space for the proliferation and migration of osteoblasts, but also enhances the angiogenesis of mesenchymal stem cells, affects the expression of osteogenic genes and osteoblast differentiation, and is an important factor in promoting bone integration. Comprehensive domestic and foreign studies have shown that titanium alloy prostheses with a porosity of 65% and a pore size of 600μm are more conducive to bone integration.

[0004] At present, most common radial head prostheses on the market are solid structures. After replacement surgery, they will produce obvious stress shielding, stress concentration in the humeral cartilage, and difficulty in bone ingrowth, which can easily lead to osteoporosis, elbow arthritis and implant loosening in the long term.

[0005] To address these issues, some device companies have designed perforated structures on the outer surface, but have not systematically studied the pore size and internal structure. Therefore, it is necessary to improve the pore size and internal structure of existing perforated radial head prostheses. Summary of the Invention

[0006] The technical problem to be solved by the embodiments of the present invention is to provide a method and system for designing a porous radial head prosthesis, which can ensure structural strength while increasing the pore diameter and reducing the porosity, effectively reduce the material equivalent elastic modulus, improve shock absorption performance, and promote bone ingrowth.

[0007] In order to solve the above technical problems, an embodiment of the present invention provides a method for designing a porous radial head prosthesis, the method comprising the following steps:

[0008] Obtain a three-dimensional model of the radial head prosthesis;

[0009] Based on the three-dimensional model of the radial capitellum prosthesis, a mainstream cell structure is established to obtain a finite element model of the porous radial capitellum prosthesis. A virtual mechanical test bench is established in ABAQUS for calculation and comparison to obtain a new cell with the best current mechanical properties. The finite element model of the porous radial capitellum prosthesis is further modified based on the obtained new cell.

[0010] The relationship between pore size, porosity and cell size is established, and based on the relationship between pore size, porosity and cell size, the node tolerance is set on the modified finite element model of the porous radial capitellum prosthesis to generate a porous radial capitellum prosthesis with overlapping inner and outer nodes, and then output it after solidification processing.

[0011] Wherein, in the three-dimensional model of the radial capitellum prosthesis, the radial capitellum prosthesis includes a radial capitellum and a radial medullary needle, both of which are solid structures; the radial medullary needle includes a radial medullary needle head, a radial medullary needle neck and a connecting handle.

[0012] Among them, in the finite element model of the porous radial head prosthesis, the internal structure of the radial bone marrow needle and the connecting handle is a linear lattice structure of a cell array, and the external triangular unit is a common node structure; wherein, the cell adopts a tetrahedral cell.

[0013] The relationship between the pore size, porosity and cell size is achieved through the following formula:

[0014] h=a×tan 60°

[0015]

[0016] V cell =3×a 2 ×cos30°×h

[0017]

[0018]

[0019] Where a is the side length of the cell; h is the height of the cell; d hole is the aperture; V cell is the cell volume; l total is the length of the new cell lattice structure; V radial is the volume of the prosthesis, measured according to the three-dimensional model; v is the porosity.

[0020] The step of setting node tolerance on the modified finite element model of the porous radial head prosthesis to generate a porous radial head prosthesis with coincident inner and outer nodes and outputting the solidified model after processing specifically includes:

[0021] Performing triangulation on the modified finite element model of the porous radial head prosthesis, establishing a set 1 of triangle vertices and a set 2 of outermost cell vertices;

[0022] Obtain the coordinate nodes of set 1 and set 2, establish a loop command, solve the distance between set 1 and set 2 based on the vertex coordinates, set the tolerance value, and when it is less than the tolerance, assign the vertex coordinate of set 2 to the coordinate value of the nearest point in set 1. After the loop command ends, a porous radial head prosthesis with overlapping inner and outer nodes is obtained.

[0023] An embodiment of the present invention further provides a porous radial head prosthesis design system, comprising:

[0024] A three-dimensional model acquisition unit, used for acquiring a three-dimensional model of the radial head prosthesis;

[0025] a finite element model correction unit, configured to establish a mainstream cell structure based on the three-dimensional model of the radial capitellum prosthesis to obtain a finite element model of the porous radial capitellum prosthesis, establish a virtual mechanical test bench in ABAQUS for calculation and comparison, and obtain a new cell with the best current mechanical properties; and further correct the finite element model of the porous radial capitellum prosthesis based on the obtained new cell;

[0026] The prosthesis design result output unit is used to establish the relationship between pore size, porosity and cell size, and based on the relationship between pore size, porosity and cell size, set the node tolerance on the modified finite element model of the porous radial head prosthesis to generate a porous radial head prosthesis with overlapping internal and external nodes and output it after solidification processing.

[0027] Wherein, in the three-dimensional model of the radial capitellum prosthesis, the radial capitellum prosthesis includes a radial capitellum and a radial medullary needle, both of which are solid structures; the radial medullary needle includes a radial medullary needle head, a radial medullary needle neck and a connecting handle.

[0028] Among them, in the finite element model of the porous radial head prosthesis, the internal structure of the radial bone marrow needle and the connecting handle is a linear lattice structure of a cell array, and the external triangular unit is a common node structure; wherein, the cell adopts a tetrahedral cell.

[0029] The relationship between the pore size, porosity and cell size is achieved through the following formula:

[0030] h=a×tan 60°

[0031]

[0032] V cell =3×a 2 ×cos30°×h

[0033]

[0034]

[0035] Where a is the side length of the cell; h is the height of the cell; d hole is the aperture; V cell is the cell volume; l total is the length of the new cell lattice structure; V radial is the volume of the prosthesis, measured according to the three-dimensional model; v is the porosity.

[0036] The implementation of the embodiments of the present invention has the following beneficial effects:

[0037] 1. The porous radial head prosthesis of the present invention has a consistent and controllable internal pore size, which meets the porosity and pore size required for human bone cell growth. It can enhance the angiogenesis of mesenchymal stem cells, affect the expression of osteogenic genes and osteoblast differentiation, and promote bone integration.

[0038] 2. The present invention can effectively reduce the material equivalent elastic modulus while ensuring sufficient mechanical strength, improve shock absorption performance, avoid obvious stress shielding, reduce the possibility of implant cracking, osteoporosis after long-term implantation, elbow arthritis, secondary fractures and implant loosening, and effectively improve postoperative recovery effect;

[0039] 3. The new internal cell provided by the present invention can maintain structural strength while increasing the pore diameter and reducing the porosity compared to other cells. The internal cell nodes can automatically connect without adjusting the position, increasing design flexibility.

[0040] 4. The porous radial head prosthesis design method provided by the present invention improves the cell structure based on the finite element platform and uses tolerance merging in the processing of outer layer cells and surface nodes, providing a new idea for existing designs, reducing design costs and shortening design cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, without paying any creative work, other drawings obtained based on these drawings still fall within the scope of the present invention.

[0042] Figure 1 Flowchart of a method for designing a porous radial head prosthesis provided by an embodiment of the present invention

[0043] Figure 2 A schematic diagram of the internal structure of a porous radial head prosthesis in a method for designing a porous radial head prosthesis provided by an embodiment of the present invention;

[0044] Figure 3 A structural diagram of a new tetrahedron cell in a method for designing a porous radial head prosthesis provided by an embodiment of the present invention;

[0045] Figure 4 A structural diagram of an ABAQUS virtual mechanical test bench in a porous radial head prosthesis design method provided by an embodiment of the present invention;

[0046] Figure 5 A schematic diagram of a radial medullary needle linear lattice structure processing process in a porous radial head prosthesis design method provided by an embodiment of the present invention;

[0047] Figure 6 A schematic diagram of the process of materializing a radial medullary needle in a method for designing a porous radial capitellum prosthesis provided by an embodiment of the present invention;

[0048] Figure 7 A schematic diagram of a process for materializing the radial capitellum in a method for designing a porous radial capitellum prosthesis provided by an embodiment of the present invention;

[0049] Figure 8 A schematic structural diagram of a porous radial head prosthesis design system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0050] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention will be described in further detail below with reference to the accompanying drawings.

[0051] like Figure 1 FIG. 1 is a design method for a porous radial head prosthesis according to an embodiment of the present invention, and the method includes the following steps:

[0052] Step S1, obtaining a three-dimensional model of the radial head prosthesis;

[0053] The specific process involved collecting 130 normal adult radial CT images in DICOM format with a CT scan slice thickness of 0.5mm-1.0mm. Inclusion criteria included healthy adult volunteers undergoing physical examinations, with good development, height, weight, and body mass index (BMI) close to the national standard, and no upper limb deformities. Exclusion criteria included a history of trauma (fractures of any part of the upper limb, malunion, joint dislocation, etc.); congenital deformities such as congenital fusion of the radius and ulna, chondrodysplasia, rickets, and gigantism.

[0054] Secondly, based on the above CT images, a three-dimensional model of the radial capitellum prosthesis was constructed; wherein, in the three-dimensional model of the radial capitellum prosthesis, the radial capitellum prosthesis includes a radial capitellum and a radial medullary needle, both of which are solid structures; the radial medullary needle includes a radial medullary needle head, a radial medullary needle neck and a connecting handle.

[0055] Step S2: Based on the three-dimensional model of the radial capitellum prosthesis, a mainstream cell structure is established to obtain a finite element model of the porous radial capitellum prosthesis, and a virtual mechanical test bench is established in ABAQUS for calculation and comparison to obtain a new cell with the best current mechanical properties. The finite element model of the porous radial capitellum prosthesis is further modified based on the obtained new cell;

[0056] The specific process is as follows: first, the finite element model building software is used to build the mainstream cell structure of the three-dimensional model of the radial head prosthesis to obtain the finite element model of the porous radial head prosthesis. Figure 2 As shown in the figure, the outer surface of the radial head in the porous radial head prosthesis is a closed surface with a relatively thin thickness, which needs to be verified by finite element calculation. The interior is a lattice structure of cells with equal diameters. The radial medullary needle is a solid except for the radial medullary needle neck and the transition area of ​​the neck handle. The outer surface of the radial medullary needle head and the connecting handle are triangular holes. The interior is arrayed according to the porosity and pore size required for the growth of human bone cells, forming a lattice structure of cells with equal diameters. That is, in the finite element model of the porous radial head prosthesis, the internal structure of the radial medullary needle head and the connecting handle is a linear lattice structure of the cell array, and the external triangular unit is a common node structure. Among them, the cell adopts a tetrahedral cell, as shown in FIG. Figure 3 shown.

[0057] It should be noted that based on the finite element model design, it is possible to directly know the advantages and disadvantages of the cell mechanical properties without 3D printing the newly developed cell structure, and at the same time control the thickness of the radial head shell.

[0058] Step S3: Establish the relationship between pore size, porosity and cell size, and based on the relationship between pore size, porosity and cell size, set the node tolerance on the modified finite element model of the porous radial head prosthesis to generate a porous radial head prosthesis with overlapping inner and outer nodes, and output it after solidification processing.

[0059] The specific process is to determine the cell size and cell radius based on the experimental bone growth pore size and bone porosity, and array the cells internally to obtain an internal linear lattice structure.

[0060] Taking the porous modeling of radial marrow needle as an example, we first construct the relationship between pore size, porosity and cell size through 60° modified tetrahedron and use the following formula to achieve it;

[0061] h=a×tan 60°

[0062]

[0063] V cell =3×a 2 ×cos30°×h

[0064]

[0065]

[0066] Where a is the side length of the cell; h is the height of the cell; d hole is the aperture; V cell is the cell volume; l total is the length of the new cell lattice structure; V radial is the volume of the prosthesis, measured according to the three-dimensional model; v is the porosity.

[0067] Then, the surface mesh triangulation is performed on the modified finite element model of the radial intramedullary needle, and a set 1 of triangle vertices and a set 2 of outermost cell vertices are established;

[0068] Secondly, the coordinate nodes of set 1 and set 2 are obtained, and a loop command is established to solve the distance between set 1 and set 2 based on the vertex coordinates. A tolerance value is set, and when the distance is less than the tolerance, the vertex coordinate of set 2 is assigned to the coordinate value of the nearest point in set 1. After the loop command ends, a radial needle with the inner and outer nodes overlapping is obtained.

[0069] Finally, the radial marrow needle with the inner and outer nodes overlapped is solidified and output. For example, the radial marrow needle head and the connecting handle are solidified according to the calculated cell radius. The process of solidifying the radial marrow needle is as follows: Figure 6 As shown, the connecting handle can be filled with nutrients such as growth factors, type I collagen and chitosan due to its porous structure to promote bone growth.

[0070] Similarly, the radial head is modeled and solidified using the same method, such as Figure 7 As shown, in order to ensure uniform contact force, its outer surface is a closed body.

[0071] like Figure 8 FIG. 1 is a porous radial head prosthesis design system provided in an embodiment of the present invention, comprising:

[0072] A three-dimensional model acquisition unit 110 is used to acquire a three-dimensional model of the radial head prosthesis;

[0073] a finite element model correction unit 120 for establishing a mainstream cell structure based on the three-dimensional model of the radial capitellum prosthesis to obtain a finite element model of the porous radial capitellum prosthesis, and establishing a virtual mechanical test bench in ABAQUS for calculation and comparison to obtain a new cell with the best current mechanical properties, and further correcting the finite element model of the porous radial capitellum prosthesis based on the obtained new cell;

[0074] The prosthesis design result output unit 130 is used to establish the relationship between pore size, porosity and cell size, and based on the relationship between pore size, porosity and cell size, set the node tolerance on the modified finite element model of the porous radial head prosthesis to generate a porous radial head prosthesis with overlapping internal and external nodes and output it after solidification processing.

[0075] Wherein, in the three-dimensional model of the radial capitellum prosthesis, the radial capitellum prosthesis includes a radial capitellum and a radial medullary needle, both of which are solid structures; the radial medullary needle includes a radial medullary needle head, a radial medullary needle neck and a connecting handle.

[0076] Among them, in the finite element model of the porous radial head prosthesis, the internal structure of the radial bone marrow needle and the connecting handle is a linear lattice structure of a cell array, and the external triangular unit is a common node structure; wherein, the cell adopts a tetrahedral cell.

[0077] The relationship between the pore size, porosity and cell size is achieved through the following formula:

[0078] h=a×tan 60°

[0079]

[0080] V cell =3×a 2 ×cos30°×h

[0081]

[0082]

[0083] Where a is the side length of the cell; h is the height of the cell; d hole is the aperture; V cell is the cell volume; l total is the length of the new cell lattice structure; V radial is the volume of the prosthesis, measured according to the three-dimensional model; v is the porosity.

[0084] The implementation of the embodiments of the present invention has the following beneficial effects:

[0085] 1. The porous radial head prosthesis of the present invention has a consistent and controllable internal pore size, which meets the porosity and pore size required for human bone cell growth. It can enhance the angiogenesis of mesenchymal stem cells, affect the expression of osteogenic genes and osteoblast differentiation, and promote bone integration.

[0086] 2. The present invention can effectively reduce the material equivalent elastic modulus while ensuring sufficient mechanical strength, improve shock absorption performance, avoid obvious stress shielding, reduce the possibility of implant cracking, osteoporosis after long-term implantation, elbow arthritis, secondary fractures and implant loosening, and effectively improve postoperative recovery effect;

[0087] 3. The new internal cell provided by the present invention can maintain structural strength while increasing the pore diameter and reducing the porosity compared to other cells. The internal cell nodes can automatically connect without adjusting the position, increasing design flexibility.

[0088] 4. The porous radial head prosthesis design method provided by the present invention improves the cell structure based on the finite element platform and uses tolerance merging in the processing of outer layer cells and surface nodes, providing a new idea for existing designs, reducing design costs and shortening design cycles.

[0089] It is worth noting that in the above system embodiment, the various units included are only divided according to functional logic, but are not limited to the above division, as long as the corresponding functions can be achieved; in addition, the specific names of the functional units are only for the convenience of distinguishing each other, and are not used to limit the scope of protection of the present invention.

[0090] Those skilled in the art will understand that all or part of the steps in the above-mentioned embodiment method can be completed by instructing the relevant hardware through a program, and the program can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc.

[0091] The above disclosure is only a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for designing a porous radial head prosthesis, characterized in that: The method comprises the following steps: Obtain a three-dimensional model of the radial head prosthesis; Based on the three-dimensional model of the radial capitellum prosthesis, a mainstream cell structure is established to obtain a finite element model of the porous radial capitellum prosthesis. A virtual mechanical test bench is established in ABAQUS for calculation and comparison to obtain a new cell with the best current mechanical properties. The finite element model of the porous radial capitellum prosthesis is further modified based on the obtained new cell. Establishing a relationship between pore size, porosity, and cell size, and setting node tolerances on the modified finite element model of the porous radial capitellum prosthesis based on the relationship between pore size, porosity, and cell size, so as to generate a porous radial capitellum prosthesis with coincident inner and outer nodes, solidify the model, and then output the model; The relationship between pore size, porosity and cell size is achieved through the following formula; where, Where a is the side length of the cell; h is the height of the cell; is the aperture; is the cell volume; is the length of the new cell lattice structure; is the volume of the prosthesis, measured according to the three-dimensional model; is the porosity; The step of setting node tolerance on the modified finite element model of the porous radial capitellum prosthesis to generate the porous radial capitellum prosthesis with coincident inner and outer nodes and outputting the solidified model after the solidification process specifically includes: Perform triangulation on the modified finite element model of the porous radial head prosthesis, define the vertices of the triangular mesh as set 1, and define the vertices of the outermost cell structure as set 2; Obtain the coordinates of each vertex in set 1 and set 2, establish a loop command, solve the distance between the vertices in set 1 and the vertices in set 2 based on the coordinates of the vertices, set the tolerance value, and when the distance is less than the tolerance, assign the coordinates of the vertex in set 2 to the vertex in set 1 that is closest to it. After the loop command ends, a porous radial head prosthesis with the inner and outer nodes overlapping is obtained.

2. The method for designing a porous radial head prosthesis according to claim 1, wherein: In the three-dimensional model of the radial capitellum prosthesis, the radial capitellum prosthesis includes a radial capitellum and a radial medullary needle, both of which are solid structures; the radial medullary needle includes a radial medullary needle head, a radial medullary needle neck and a connecting handle.

3. The method for designing a porous radial head prosthesis according to claim 2, wherein: In the finite element model of the porous radial head prosthesis, the internal structure of the radial medullary needle and the connecting handle is a linear lattice structure of a cell array, the outer surface is a triangular hole and its triangular unit is a common node structure; wherein, the cell adopts a tetrahedral cell.

4. A porous radial head prosthesis design system, characterized in that: include: A three-dimensional model acquisition unit, used for acquiring a three-dimensional model of the radial head prosthesis; a finite element model correction unit, configured to establish a mainstream cell structure based on the three-dimensional model of the radial capitellum prosthesis to obtain a finite element model of the porous radial capitellum prosthesis, establish a virtual mechanical test bench in ABAQUS for calculation and comparison, and obtain a new cell with the best current mechanical properties; and further correct the finite element model of the porous radial capitellum prosthesis based on the obtained new cell; a prosthesis design result output unit, configured to establish a relationship between pore size, porosity, and cell size, and, based on the relationship between pore size, porosity, and cell size, set node tolerances on the modified finite element model of the porous radial capitellum prosthesis to generate a porous radial capitellum prosthesis with coincident inner and outer nodes, and output the result after solidification processing; The relationship between pore size, porosity and cell size is achieved through the following formula; where, Where a is the side length of the cell; h is the height of the cell; is the aperture; is the cell volume; is the length of the new cell lattice structure; is the volume of the prosthesis, measured according to the three-dimensional model; is the porosity; The step of setting node tolerance on the modified finite element model of the porous radial capitellum prosthesis to generate the porous radial capitellum prosthesis with coincident inner and outer nodes and outputting the solidified model after the solidification process specifically includes: Perform triangulation on the modified finite element model of the porous radial head prosthesis, define the vertices of the triangular mesh as set 1, and define the vertices of the outermost cell structure as set 2; Obtain the coordinates of each vertex in set 1 and set 2, establish a loop command, solve the distance between the vertices in set 1 and the vertices in set 2 based on the coordinates of the vertices, set the tolerance value, and when the distance is less than the tolerance, assign the coordinates of the vertex in set 2 to the vertex in set 1 that is closest to it. After the loop command ends, a porous radial head prosthesis with the inner and outer nodes overlapping is obtained.

5. The porous radial head prosthesis design system according to claim 4, wherein: In the three-dimensional model of the radial capitellum prosthesis, the radial capitellum prosthesis includes a radial capitellum and a radial medullary needle, both of which are solid structures; the radial medullary needle includes a radial medullary needle head, a radial medullary needle neck and a connecting handle.

6. The porous radial head prosthesis design system according to claim 5, wherein: In the finite element model of the porous radial head prosthesis, the internal structure of the radial medullary needle and the connecting handle is a linear lattice structure of a cell array, and the external triangular unit is a common node structure; wherein the cell adopts a tetrahedral cell.

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