CN116585076A

CN116585076A - Porous structure, interbody fusion cage and interbody fusion cage preparation method

Info

Publication number: CN116585076A
Application number: CN202310523118.1A
Authority: CN
Inventors: 李冬冬; 陈东旭; 李元元
Original assignee: Huazhong University of Science and Technology
Current assignee: Huazhong University of Science and Technology
Priority date: 2023-05-10
Filing date: 2023-05-10
Publication date: 2023-08-15
Anticipated expiration: 2043-05-10
Also published as: CN116585076B

Abstract

The invention belongs to the technical field of medical implants, and discloses a porous structure, an intervertebral fusion device and a preparation method of the intervertebral fusion device, wherein the porous structure is formed by arranging and assembling a plurality of three-dimensional unit cells, each three-dimensional unit cell comprises a first two-dimensional unit cell and a second two-dimensional unit cell which are connected in an intersecting way, the first two-dimensional unit cells of the plurality of three-dimensional unit cells are arranged in an array manner on a plane of the first two-dimensional unit cell of any three-dimensional unit cell, and the supporting strength of the first two-dimensional unit cell in the second direction from two sides to the center along the first direction is gradually enhanced, wherein the first direction and the second direction are vertical. The invention is arranged on a plane where the first two-dimensional unit cell is located, the supporting strength of the middle part in the first direction to the second direction is larger than the supporting strength of the two side parts to the second direction, and the supporting strength of the middle part easy to dent can be improved by directionally regulating and controlling the mechanical properties of the porous structure in practical application, thereby being beneficial to improving the mechanical properties of the porous structure and ensuring the service life.

Description

Porous structure, interbody fusion cage and interbody fusion cage preparation method

Technical Field

The invention belongs to the technical field of medical implants, and particularly relates to a porous structure, an interbody fusion cage and a preparation method of the interbody fusion cage.

Background

Due to the rapid population growth and aging trend, the demands for bone implants in today's society are rapidly increasing, clinicallyHigher requirements are placed on the properties of external implants that can be implanted in the human body. Among the materials commonly used in metal implants are stainless steel, cobalt-based alloys and titanium alloys. However, clinical researches find that the alloy materials mainly have the following problems in the service process: the elastic modulus of the alloy material is too high, and is Ti ₆ Al ₄ The V alloy is exemplified by an elastic modulus of about 110GPa, which is far higher than the human bone modulus (0.022-21.8 GPa). The alloy material with too high elastic modulus can be implanted into a human body for a long time to cause the original bone tissue function to be degraded and reabsorbed, so that the phenomenon of stress shielding is caused, and implantation failure is caused. Therefore, there is a need to develop artificial implants with biocompatibility and mechanical properties closer to those of natural bones of the human body.

Structurally, the special structure of the porous structure greatly reduces the elastic modulus of the porous structure compared with that of a compact material, and effectively reduces the stress shielding effect. For this reason, porous structures are increasingly replacing dense materials as ideal candidates for implants. The porous structure can effectively improve the stress transmission between the implant and human bone, so that better biological combination is obtained between the implant and bone tissue, and meanwhile, as the porous structure has larger surface area, cells can be supplemented and permeated into the structure from the surrounding bone tissue, bone regeneration and vascularization are promoted, cell proliferation and adhesion are facilitated, and the porous structure has great potential in biomedical implants.

However, the porous configuration adopted by the biomedical implant has a plurality of problems, mainly that the mechanical properties of the porous implant are reduced while the elastic modulus of the porous implant is reduced, and the porous implant cannot be used for both. For example, porous configuration implants are prone to stress concentrations in the loaded environment, reducing the useful life of the implant. In addition, most of the currently commercially available interbody cage prostheses consist of solid structures at the edges and internally filled porous structures, resulting in the outer solid structures of such interbody cage prostheses being prone to deformation under load due to lack of support, which can cause the porous structures to exhibit varying degrees of stress concentration, resulting in severe deformation, subsidence, and even premature failure of the overall interbody cage prosthesis.

Disclosure of Invention

Aiming at the defects or improvement demands of the prior art, the invention provides a porous structure, an interbody fusion cage and a preparation method of the interbody fusion cage, solves the problems that the mechanical properties are reduced while the elastic modulus is reduced, and the two cannot be combined, and improves the bearing capacity of the porous structure, thereby improving the mechanical properties of the porous structure.

In order to achieve the above object, according to one aspect of the present invention, there is provided a porous structure formed by an array of a plurality of three-dimensional unit cells, each of the three-dimensional unit cells including a first two-dimensional unit cell and a second two-dimensional unit cell connected to each other, the first two-dimensional unit cells of the plurality of three-dimensional unit cells being arranged in an array on a plane on which the first two-dimensional unit cell is located, and the first two-dimensional unit cells of the plurality of three-dimensional unit cells having a plurality of deformations in a first direction on the plane on which the first two-dimensional unit cell is located such that a supporting strength of the first two-dimensional unit cell in a second direction gradually increases from both sides to a center in the first direction, wherein the first direction and the second direction are perpendicular.

According to the porous structure provided by the invention, the first two-dimensional unit cell is in a positive poisson ratio two-dimensional shape, and the included angle between the inclined side of the first two-dimensional unit cell and the first direction is gradually increased from two sides to the center along the first direction on the plane where the first two-dimensional unit cell is located.

According to the porous structure provided by the invention, on the plane of the first two-dimensional unit cell, the nodes of the first two-dimensional unit cells of two adjacent three-dimensional unit cells are connected.

According to the porous structure provided by the invention, the first two-dimensional unit cell is diamond unit cell or hexagonal unit cell;

when the first two-dimensional unit cell is diamond unit cell, on the plane where the first two-dimensional unit cell is located, the width of the first two-dimensional unit cell along the first direction gradually decreases from two sides to the center, and the lengths of the first two-dimensional unit cell along the second direction are the same.

According to the porous structure provided by the invention, the first two-dimensional unit cells in each three-dimensional unit cell are vertically connected with the second two-dimensional unit cell, the lengths and the widths of the second two-dimensional unit cells in different three-dimensional unit cells are the same, and the second two-dimensional unit cells of a plurality of three-dimensional unit cells are arranged in an array on a plane where the second two-dimensional unit cells are located.

According to another aspect of the present invention, there is provided an intervertebral cage comprising:

a porous structure, which is any one of the above porous structures;

and a frame, wherein the porous structure is arranged inside the frame.

According to the interbody fusion cage provided by the invention, the frame is provided with an upper surface, a lower surface and a side edge connected between the upper surface and the lower surface, the side edge is in an inward concave shape, and the direction of the upper surface relative to the lower surface is consistent with the second direction.

According to the interbody fusion cage provided by the invention, a plurality of side edges are arranged between the upper surface and the lower surface along the circumferential direction at intervals.

According to the interbody fusion cage provided by the invention, the upper surface and the lower surface are respectively provided with through holes; the upper surface and the lower surface are respectively provided with a tooth structure.

According to another aspect of the present invention, there is provided a method for preparing an intervertebral fusion device, the intervertebral fusion device being any one of the above, the method comprising:

selecting a first two-dimensional unit cell, and obtaining multiple deformations of the first two-dimensional unit cell by changing the shape and/or the size of the first two-dimensional unit cell so that the support strength of the multiple deformations of the first two-dimensional unit cell in a second direction is different;

selecting a second two-dimensional unit cell, and arranging the second two-dimensional unit cell to be connected with the first two-dimensional unit cell in an intersecting manner to form a three-dimensional unit cell;

arranging and assembling the three-dimensional unit cells to obtain a porous structure, so that a plurality of deformations of the first two-dimensional unit cells are arranged along a first direction on a plane of any one of the three-dimensional unit cells, and the supporting strength of the first two-dimensional unit cells in a second direction is gradually enhanced from two sides to the center;

providing a frame, wherein the frame is provided with an upper surface, a lower surface and side edges connected between the upper surface and the lower surface, and the side edges are concave inwards;

disposing the porous structure into the frame such that the orientation of the upper surface relative to the lower surface is consistent with the second orientation, obtaining a model of an interbody fusion cage;

and printing and manufacturing the model by adopting an additive manufacturing technology to obtain the interbody fusion cage.

In general, compared with the prior art, the porous structure, the interbody fusion cage and the preparation method of the interbody fusion cage are provided by the invention through the technical scheme:

1. the porous structure is formed by a three-dimensional unit cell array, the model structure is simple, the model is convenient to construct and produce and manufacture, the three-dimensional unit cell is formed by intersecting and connecting a first two-dimensional unit cell and a second two-dimensional unit cell, the three-dimensional unit cell is convenient to arrange and expand, the supporting strength of the middle part of the first direction to the second direction is greater than the supporting strength of the two side parts to the second direction on the plane where the first two-dimensional unit cell is positioned, the supporting strength of the middle part easy to dent part can be improved through the directional regulation and control of the mechanical property of the porous structure in practical application, so that the generation of stress concentration phenomenon of the porous structure is reduced, the mechanical property of the porous structure is improved, and the service life is ensured;

2. the pore size of the porous structure at the middle part is different from that of the pore sizes at the two side parts, so that the inside of the porous structure is provided with a plurality of pores with different sizes, a gradient porous structure can be formed, and when the porous structure is used for a medical implant, the porous structure is beneficial to the adhesion and proliferation of cells and improves the biocompatibility of the implant;

3. set up to obtain the fusion cage frame based on interior hexagonal characteristic, set up the side of going into in having between frame upper surface and the lower surface for the deformability reinforcing of frame when atress in the second direction can play certain deformation cushioning effect, is favorable to reducing the stress concentration when bearing, improves fusion cage mechanical properties, and the side of going into in the frame can also be better on transmitting the porous structure with the pressure that the side received, accessible porous structure is reacted to in the bearing direction with this partial pressure, thereby further strengthen bearing capacity.

Drawings

FIG. 1 is a schematic single row of porous structures provided by the present invention;

FIG. 2 is a schematic diagram showing the arrangement of a first two-dimensional unit cell in a porous structure according to the present invention;

FIG. 3 is a schematic diagram of a first variation of the diamond-shaped unit cell provided by the invention;

FIG. 4 is a second modified schematic of diamond-shaped cells provided by the present invention;

FIG. 5 is a schematic diagram of a third variation of the diamond-shaped unit cell provided by the invention;

FIG. 6 is a schematic diagram of the arrangement of hexagonal cells provided by the invention;

FIG. 7 is a multi-row schematic view of a porous structure provided by the present invention;

FIG. 8 is a schematic top view of a plurality of rows of porous structures provided by the present invention;

FIG. 9 is a general schematic of an intersomatic cage provided by the present invention;

FIG. 10 is a front schematic view of a frame of an intersomatic cage provided by the present invention;

FIG. 11 is an overall schematic of a frame of an intersomatic cage provided by the present invention;

FIG. 12 is a schematic plan view of an interbody cage according to the present invention;

FIG. 13 is a schematic view of the support force of the interbody fusion cage of the present invention in a second orientation;

FIG. 14 is a schematic view of the support force of the interbody fusion cage of the present invention in a first direction;

the same reference numbers are used throughout the drawings to reference like elements or structures, wherein:

1: a three-dimensional unit cell; 1a: a first three-dimensional unit cell; 1b: a second three-dimensional unit cell; 1c: three-dimensional unit cell number three; 11: a first two-dimensional unit cell; 11a: a first deformation of diamond-shaped cells; 11b: a second deformation of diamond-shaped cells; 11c: a third variation of diamond-shaped cells; 12: a second two-dimensional unit cell; 2: a frame; 21: an upper surface; 22: a lower surface; 23: a side edge; 24: a tooth structure; 25: and a through hole.

Detailed Description

The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention. In addition, the technical features of the embodiments of the present invention described below may be combined with each other as long as they do not collide with each other.

Referring to fig. 1, the present invention provides a porous structure, wherein the porous structure is formed by arranging a plurality of three-dimensional unit cells 1, each three-dimensional unit cell 1 includes a first two-dimensional unit cell 11 and a second two-dimensional unit cell 12 connected with each other, the first two-dimensional unit cells 11 of the plurality of three-dimensional unit cells 1 are arranged in an array on a plane of the first two-dimensional unit cell 11, and the first two-dimensional unit cells 11 of the plurality of three-dimensional unit cells 1 have a plurality of deformations along a first direction on the plane of the first two-dimensional unit cell 11, so that a supporting strength of the first two-dimensional unit cell 11 in a second direction from two sides to a center along the first direction is gradually increased, wherein the first direction and the second direction are perpendicular.

In this embodiment, for each three-dimensional unit cell 1, a three-dimensional structure is formed by arranging the first two-dimensional unit cell 11 and the second two-dimensional unit cell 12 to be connected in an intersecting manner, and a porous structure is formed by expanding an array of the three-dimensional structure. The first two-dimensional unit cell 11 and the second two-dimensional unit cell 12 are respectively two-dimensional shapes, and are connected in an intersecting manner, namely, planes of the two-dimensional unit cells are in an intersecting manner. Further, for any one three-dimensional unit cell 1, the centerlines of the first two-dimensional unit cell 11 and the second two-dimensional unit cell 12 may coincide; i.e. the symmetry lines of the first two-dimensional unit cell 11 and the second two-dimensional unit cell 12 coincide, an array arrangement can be facilitated.

Further, on the plane on which the first two-dimensional unit cells 11 are located, the first two-dimensional unit cells 11 in the plurality of three-dimensional unit cells 1 are arranged in an array, that is, the plurality of first two-dimensional unit cells 11 in the plurality of three-dimensional unit cells 1 are arranged in a plurality of rows and/or columns. For example, referring to the porous structure shown in fig. 1, the first two-dimensional unit cells 11 of the three-dimensional unit cells 1 are arranged in a plurality of rows and columns. Further, referring to fig. 1 and 2, the plurality of first two-dimensional unit cells 11 are not exactly the same in the first direction on the plane in which the first two-dimensional unit cells 11 are located, but have various deformed structures such that there is a variation in the supporting strength of the first two-dimensional unit cells 11 in the first direction to the second direction. In this embodiment, the first two-dimensional unit cell 11 is deformed to generate different supporting strengths along the first direction, so that directional regulation and control of mechanical properties of the porous structure can be realized.

Specifically, on a plane where the first two-dimensional unit cell 11 is located, a first direction and a second direction which are perpendicular to each other are selected, a plurality of rows of first two-dimensional unit cells 11 are arranged along the first direction, at least one first two-dimensional unit cell 11 is arranged in each row, and the structural dimensions of at least one first two-dimensional unit cell 11 in each row are the same; for the first two-dimensional unit cell 11 of the plurality of rows, the first two-dimensional unit cell 11 near the middle part has a support strength in the second direction greater than that of the first two-dimensional unit cell 11 near the side part by deformation. The supporting strength of the first two-dimensional unit cell 11 in the second direction refers to the maximum acting force in the second direction that the first two-dimensional unit cell 11 can bear; the maximum force is the maximum force that the first two-dimensional unit 11 can withstand when the deformation degree does not exceed the preset deformation degree when the force in the second direction is applied to the first two-dimensional unit 11.

Furthermore, through the specific arrangement of the first two-dimensional unit cell 11, the supporting strength of the formed porous structure in the second direction at the middle part is larger than the supporting strength of the edge part, and the actual stress direction can be set to be consistent with the second direction when the porous structure is applied, so that the supporting strength of the middle part of the porous structure is stronger when the porous structure is applied practically, the middle part of the porous structure is prevented from being sunk, the phenomenon of stress concentration of the porous structure is further reduced, the mechanical property of the porous structure is improved, and the service life of the porous structure is prolonged.

The porous structure provided by the invention is formed by arranging and assembling the three-dimensional unit cells 1, the model structure is simple, the model is convenient to construct and produce and manufacture, the three-dimensional unit cells 1 are formed by intersecting and connecting the first two-dimensional unit cells 11 and the second two-dimensional unit cells 12, the three-dimensional unit cells 1 are convenient to arrange and expand, the supporting strength of the middle part of the first direction to the second direction is greater than the supporting strength of the two side parts to the second direction on the plane where the first two-dimensional unit cells 11 are positioned, and the supporting strength of the middle part easy to dent part can be improved during practical application through directional regulation and control of the mechanical property of the porous structure, so that the generation of stress concentration phenomenon of the porous structure is reduced, the mechanical property of the porous structure is improved, and the service life is ensured.

When the porous structure is applied to the interbody fusion cage, the support strength of the middle part is high, so that the external solid structure can be effectively supported, the probability of deformation of the solid structure is reduced, the occurrence of stress concentration is reduced, and the fusion cage is prevented from serious deformation, sinking and premature failure.

Further, the first two-dimensional unit cell 11 in the first direction is deformed on the plane of the first two-dimensional unit cell 11, namely, the first two-dimensional unit cell 11 positioned at the middle part along the first direction is different from the first two-dimensional unit cell 11 positioned at the two side parts, so that the pore size of the formed porous structure at the middle part is different from the pore size of the two side parts, and further, the porous structure is internally provided with pores with various different sizes, a gradient porous structure can be formed, and when the porous structure is used for a medical implant, the adhesion and proliferation of cells are facilitated, and the biocompatibility of the implant is improved.

Further, the first two-dimensional unit cell 11 may be deformed by a change in shape and/or size to adjust the support strength in the second direction.

Further, the first two-dimensional unit cell 11 is in a two-dimensional shape with positive poisson ratio, and on a plane where the first two-dimensional unit cell 11 is located, an included angle between the oblique side of the first two-dimensional unit cell 11 and the first direction gradually increases from two sides to the center along the first direction. The present embodiment provides an implementation manner of the deformation of the first two-dimensional unit cell 11, where the first two-dimensional unit cell 11 may be configured in a positive poisson ratio shape, and the symmetry axis of the positive poisson ratio shape may be configured along the second direction, so that the positive poisson ratio shape may have a bevel edge with respect to the first direction. Here, the angle between the oblique side of the first two-dimensional unit cell 11 and the first direction gradually increases, which may be an acute angle between the oblique side of the first two-dimensional unit cell 11 and the first direction gradually increases.

For example, referring to fig. 2, the positive poisson ratio may be in a diamond shape, and the included angle θ between the hypotenuse of the diamond and the first direction is shown in the figure, it can be seen that the included angle between the hypotenuse of the diamond located in the middle along the first direction and the first direction is larger than the included angle between the hypotenuse of the diamond located at both sides and the first direction. It is verified that as the included angle between the inclined edge of the diamond and the first direction increases, the supporting strength of the diamond to the second direction increases.

In another embodiment, referring to fig. 6, the positive poisson's ratio shape may be hexagonal, with the hypotenuse of the hexagon at an angle θ to the first direction as shown. It can be seen that the angle between the hypotenuse of the hexagon located in the middle along the first direction and the first direction is larger than the angle between the hypotenuse of the hexagon located on both sides and the first direction. It is verified that the supporting strength of the hexagon to the second direction increases with the increasing angle between the hypotenuse of the hexagon and the first direction. In other embodiments, the positive poisson's ratio two-dimensional shape may be other shapes, which is not limited in particular, and aims to realize the adjustment of the change of the supporting strength of the second direction through the change of the included angle between the oblique side and the first direction.

Further, on the plane on which the first two-dimensional unit cell 11 is located, the nodes of the first two-dimensional unit cells 11 of two adjacent three-dimensional unit cells 1 are connected. Referring to fig. 1 and 2, that is, on the plane in which the first two-dimensional unit cells 11 lie, the first two-dimensional unit cells 11 adjacent in the first direction are connected at the node site, and the first two-dimensional unit cells 11 adjacent in the second direction are also connected at the node site.

The invention relates to a method for connecting the stress of a first two-dimensional unit cell 11 in a first direction with the stress of a second direction, in particular to the method, which is arranged in the first direction, has stronger supporting strength of the first two-dimensional unit cell 11 close to the middle part in the second direction, and is beneficial to better bearing and avoiding deformation and stress concentration in practical application; and when the porous structure is subjected to the pressure in the first direction, the first two-dimensional unit cell 11 also reacts the pressure in the first direction to the second direction, so that the bearing capacity of the porous structure in the second direction is further enhanced.

Further, the first two-dimensional unit cell 11 is a diamond unit cell or a hexagonal unit cell.

Specifically, referring to fig. 2, when the first two-dimensional unit cell 11 is a diamond unit cell, on a plane on which the first two-dimensional unit cell 11 is located, the width of the first two-dimensional unit cell 11 along the first direction gradually decreases from two sides to the center, and the lengths of the first two-dimensional unit cell 11 in the second direction are the same.

That is, in this embodiment, when the first two-dimensional unit cell 11 is set as a diamond unit cell, the deformation of the diamond unit cell is performed by changing the ratio of the major axis to the minor axis of the diamond unit cell, and a plurality of diamond unit cell deformations having different support strengths in the second direction are obtained. The porous structure provided by the embodiment selects two-dimensional diamond unit cells as basic elements of the first two-dimensional unit cell 11 in design, wherein the long axis of the diamond unit cell is a, and the distance between horizontal vertexes is the distance between horizontal vertexes; the short axis is b, which is the distance of the apex in the vertical direction. Two-dimensional diamond-shaped single cells of three shapes are obtained by changing the value of a/b. Two-dimensional diamond-shaped unit cell a/b=1.5 as shown in fig. 3, being the first variant 11a of diamond-shaped unit cell; two-dimensional diamond-shaped unit cell a/b=1 of fig. 4, being the second variant 11b of diamond-shaped unit cell; two-dimensional diamond-shaped unit cell a/b=0.6 of fig. 5, being a third variant 11c of diamond-shaped unit cell; the larger the value of a/b, the weaker the bearing capacity in the vertical direction, namely the second direction, the smaller the value of a/b, and the stronger the bearing capacity in the vertical direction.

In order to realize that the porous structure has better support to the middle part of the horizontal cross beam of the interbody fusion cage, three two-dimensional diamond structures in the steps are arranged to form a gradient porous structure. Wherein the first deformations 11a of the diamond-shaped unit cell with the largest a/b are arranged on two sides, the third deformations 11c of the two-dimensional diamond-shaped unit cell with the smallest a/b are arranged at the center, the second deformations 11b of the diamond-shaped unit cell are arranged between the first deformations 11a of the diamond-shaped unit cell and the third deformations 11c of the diamond-shaped unit cell, and the lengths of the unit cells in the vertical direction, namely the second direction, are kept consistent, so that the multi-row arrangement is facilitated, as shown in fig. 2. Referring to fig. 1, a first two-dimensional unit cell 11 in a three-dimensional unit cell 1a located on the side in the first direction is a first variant 11a of a diamond-shaped unit cell; the first two-dimensional unit cell 11 in the two-dimensional unit cell 1b adjacent to the three-dimensional unit cell 1a is the second deformation 11b of the diamond-shaped unit cell; the first two-dimensional unit cell 11 in the three-dimensional unit cell 1c located in the center part is the third variant 11c of the diamond-shaped unit cell.

Referring to fig. 6, when the first two-dimensional unit cell 11 is provided as a hexagonal unit cell, the symmetry axis of the hexagonal unit cell is provided along the second direction, and various deformations can be obtained by changing the angle θ between the hypotenuse in the hexagonal unit cell and the first direction. In the embodiment shown in fig. 6, there are three variants of hexagonal unit cells, in which, on a plane in which the hexagonal unit cell is located, the variant with the largest included angle θ between the oblique side and the first direction is located at the middle portion of the first direction, and the variant with the smallest included angle θ between the oblique side and the first direction is located at the two side portions of the first direction. The lengths of the hexagonal cells in the second direction may be the same.

Further, the deformation of the hexagonal unit cell may take other forms, for example, the deformation may be performed by reducing the width of the hexagonal unit cell in the first direction, and also various deformations having different supporting strengths in the second direction may be obtained, and the deformation form of the first two-dimensional unit cell 11 is not limited with the purpose of being able to obtain various deformations having different supporting strengths in the second direction. In the above embodiment, on the plane in which the first two-dimensional unit cell 11 is located, the three-dimensional unit cells 1 of the odd-numbered rows are arranged in the first direction; in other embodiments, even three-dimensional unit cells 1 may be arranged along the first direction, and the number of specific columns is not limited, so that the support strength of the first two-dimensional unit cell 11 in the second direction is gradually increased from both sides to the center.

Further, the first two-dimensional unit cell 11 in each three-dimensional unit cell 1 is vertically connected with the second two-dimensional unit cell 12, and the lengths and the widths of the second two-dimensional unit cells 12 in different three-dimensional unit cells 1 are the same, and on the plane of the second two-dimensional unit cell 12, the second two-dimensional unit cells 12 of the plurality of three-dimensional unit cells 1 are arranged in an array. The length of the second two-dimensional unit cell 12 is the length dimension in the second direction, and the width of the second two-dimensional unit cell 12 is the width dimension in the third direction perpendicular to the first and second directions.

The lengths and the widths of the second two-dimensional unit cells 12 in different three-dimensional unit cells 1 are the same, so that the array arrangement form of the second two-dimensional unit cells 12 can be realized on the plane where any second two-dimensional unit cell 12 is positioned, and the arrangement and the group array of the three-dimensional unit cells 1 are more orderly. For example, referring to fig. 1, the single-row three-dimensional unit cell 1 is arranged, the single-row three-dimensional unit cell 1 has a plurality of rows and columns of three-dimensional unit cells 1, the first two-dimensional unit cells 11 are in an array connection form, and the shape and the size of the second two-dimensional unit cell 12 in the porous structure formed by the single-row three-dimensional unit cell 1 are not limited, so that the connection between the adjacent three-dimensional unit cells 1 can be realized.

Referring to fig. 7, an arrangement form of multiple rows of three-dimensional unit cells 1 is shown, wherein multiple rows (specifically 3 rows) of three-dimensional unit cells 1 are arranged in the multiple rows of three-dimensional unit cells 1, multiple rows and multiple columns of three-dimensional unit cells 1 are arranged in each row of three-dimensional unit cells 1, wherein the length and width dimensions of second two-dimensional unit cells 12 in different three-dimensional unit cells 1 can be identical, so that the multiple rows of three-dimensional unit cells 1 can be arranged in parallel and orderly, and the array expansion of the three-dimensional unit cells 1 can be facilitated as shown in fig. 8.

Further, the shapes of the second two-dimensional unit cells 12 in the different three-dimensional unit cells 1 may be the same or different, and are not particularly limited.

Further, referring to fig. 9, the present invention also provides an intervertebral cage comprising: a porous structure as described in any one of the embodiments above; a frame 2, said porous structure being arranged inside said frame 2. By filling the frame 2 of the interbody fusion cage with the porous structure according to any one of the embodiments, the bearing capacity of the cage at the middle part can be improved, as shown in fig. 12, so that the cage is advantageously prevented from being deformed concavely, the occurrence of stress concentration phenomenon can be reduced, the mechanical properties of the cage are improved, and the bearing capacity and the service life of the cage are advantageously improved.

Further, the frame 2 has an upper surface 21, a lower surface 22, and a side 23 connected between the upper surface 21 and the lower surface 22, the side 23 is concave inward, wherein the direction of the upper surface 21 relative to the lower surface 22 coincides with the second direction.

Referring to fig. 10, 11 and 12, that is, when the porous structure is filled into the frame 2, the upper surface 21 is located at one side of the porous structure in the second direction, the lower surface 22 is located at the other side of the porous structure in the second direction, and the upper surface 21 and the lower surface 22 are main bearing surfaces in practical use. In this embodiment, the frame 2 for the fusion cage is obtained by setting based on the characteristic of the hexagon, and the side 23 of the hexagon is specifically set between the upper surface 21 and the lower surface 22 of the frame 2, and the setting characteristic not only enables the frame 2 to better contact with the porous structure to improve the overall stability, but also enables the deformation capability of the frame 2 to be enhanced when being stressed in the second direction by the side 23 of the hexagon, so that the frame 2 has a certain deformability when the upper surface 21 of the frame 2 is borne, compared with the straight edge setting, the frame has a certain deformation buffering effect, is beneficial to reducing stress concentration when bearing and improving the mechanical property of the fusion cage; further, referring to fig. 14, the side 23 in the frame 2 can further better transfer the pressure applied to the side 23 to the porous structure, and the porous structure can react the partial pressure to the bearing direction, so as to further enhance the bearing capacity.

Further, a plurality of the side edges 23 are provided between the upper surface 21 and the lower surface 22 at intervals in the circumferential direction.

Referring to fig. 11, the cage frame 2 of the present embodiment has four sides 23, each side 23 being formed of an inwardly curved sheet-like structure having a thickness of 0.5-3mm. Further, the side edges 23 may be disposed on opposite sides of the porous structure in the first direction. So that when the side edges 23 are subjected to pressure, this partial pressure acts on the porous structure in the first direction, and the first two-dimensional unit cell 11 in the porous structure can instead enhance the supporting strength in the second direction when being subjected to pressure in the first direction, so that the porous structure can react this partial pressure to the second direction, improving the overall carrying capacity, as shown in fig. 14.

Further, referring to fig. 11, the upper surface 21 and the lower surface 22 are respectively provided with through holes 25; the cell adhesion and proliferation between the cells and the porous structure are facilitated when the fusion device is implanted, and the biocompatibility of the fusion device is improved. Teeth structures 24 are provided on the upper surface 21 and the lower surface 22, respectively, to increase friction with the bone interface to prevent dislocation.

Specifically, referring to fig. 11 and 12, the tooth structure 24 may be a discrete protrusion structure, which may be distributed on the upper surface 21 and the lower surface 22 in a discrete manner, and the cross-sectional dimension of the protrusion structure from the surface of the frame 2 to the end far from the surface may be gradually reduced, so that the protrusion structure may be better connected and fixed with the bone interface. In other embodiments, the tooth structure 24 may take other forms, such as, but not limited to, a inverted tooth structure 24.

Further, referring to fig. 9 and 11, in this embodiment, two side edges 23 are provided on both sides of the frame 2 in the first direction, and the side edges along both sides in the first direction are oppositely disposed in pairs; such that both sides of the frame 2 in the first direction are formed with openings between the side edges 23, respectively; the upper surface 21 and the lower surface 22 of the frame 2 are each provided with a through hole 25; the porous structure may be disposed at a location between the opposite sides 23, i.e., at a location between two pairs of opposite sides 23 inside the frame 2, respectively, such that the through holes 25 penetrate the porous structure up and down and communicate with openings of both sides of the frame 2 in the first direction. At this time, a single three-dimensional unit cell may be provided at a position between each pair of opposite side edges 23, or a plurality of three-dimensional unit cells may be provided, and the present invention is not limited thereto.

In other embodiments, the porous structure may be filled in the frame 2, and the arrangement of the porous structure in the frame 2 may be flexibly selected according to actual needs, which is not limited in particular.

Further, the present invention also provides a method for preparing an intervertebral fusion device, where the intervertebral fusion device is an intervertebral fusion device according to any one of the above embodiments, and the method includes:

selecting a first two-dimensional unit cell 11, and obtaining multiple deformations of the first two-dimensional unit cell 11 by changing the shape and/or the size of the first two-dimensional unit cell 11 so that the support strength of the multiple deformations of the first two-dimensional unit cell 11 in a second direction is different;

selecting a second two-dimensional unit cell 12, and arranging the second two-dimensional unit cell 12 and the first two-dimensional unit cell 11 to be connected in an intersecting way to form a three-dimensional unit cell 1;

arranging and assembling the three-dimensional unit cells 1 to obtain a porous structure, so that on a plane where the first two-dimensional unit cell 11 of any one of the three-dimensional unit cells 1 is positioned, multiple deformations of the first two-dimensional unit cell 11 are arranged along a first direction, and the supporting strength of the first two-dimensional unit cell 11 in a second direction is gradually enhanced from two sides to the center;

providing a frame 2, wherein the frame 2 has an upper surface 21, a lower surface 22 and a side 23 connected between the upper surface 21 and the lower surface 22, and the side 23 is concave inwards;

disposing the porous structure into the frame 2 such that the orientation of the upper surface 21 relative to the lower surface 22 coincides with the second orientation, obtaining a model of an intersomatic cage;

The method can adopt a Selective Laser Melting (SLM) technology to perform additive manufacturing of the interbody fusion cage, the SLM technology is used as an additive manufacturing preparation method, has great application potential in the field of porous material preparation, breaks through the limitation of the traditional processing method, can accurately regulate and control the shape, the size, the distribution condition and the like of a pore structure, and is one of the most beneficial processes for forming the porous structure.

Specifically, diamond-shaped unit cell is selected as the first two-dimensional unit cell 11 in the embodiment, and the preparation method of the interbody fusion cage comprises the following steps: (1) Selecting a two-dimensional diamond unit cell, and obtaining two-dimensional diamond unit cells with different long and short axis ratios by changing the long axis value and the short axis value; and selecting the second two-dimensional unit cells 12, and arranging each two-dimensional diamond unit cell to be connected with one second two-dimensional unit cell 12 in an intersecting manner to form the three-dimensional unit cell 1.

(2) And (3) arranging and assembling the three-dimensional unit cells 1, namely horizontally arranging the diamond unit cells with different long and short axis ratios in the step (1), namely arranging the diamond unit cells along a first direction, and obtaining a gradient porous structure.

(3) The cage frame 2 is designed, which cage frame 2 is obtained on the basis of an inward hexagon. Cross-teeth are added to the upper and lower surfaces 22 of the cage frame 2 to increase friction with the bone interface to prevent dislocation. The three-dimensional structure of the interbody cage frame 2 can be drawn in the three-dimensional design software SolidWorks, and the solid support in the vertical direction is a curved sheet structure, so that the porous part can be well fixed with the edge. Cross-teeth are added to the upper and lower surfaces 22 of the cage frame 2 to increase friction with the bone interface to prevent dislocation, as shown in FIG. 11.

(4) Filling the gradient porous structure in the step (2) into the interbody fusion cage frame 2 in the step (3) to obtain an interbody fusion cage prosthesis, namely a model.

(5) Manufacturing the interbody fusion cage prosthesis in the step (4) by adopting an additive manufacturing technology to obtain an implantable medical device.

Specifically, the two-dimensional diamond-shaped unit cells are horizontally arranged in such a way that the ratio of the long axis to the short axis of the horizontal symmetry axis is gradually reduced from two sides. The gradient porous structure in the step (1) has the following specific parameter requirements: the range of pore parameter values comprises the cell size of 2-4mm and the porosity of 60% -90%; the pore diameter range is 200-900 mu m; the additive manufacturing process limitations are specifically: the diameter range of the rod is 200-600 mu m; the cell size is the maximum of the major and minor axes of the diamond-shaped unit cell.

Research shows that the gradient structure can have different bearing capacities, but the traditional gradient porous structure changes the porosity to realize mechanical regulation and control, and can not realize directional regulation of mechanics. Through verification, the mechanical regulation and control in the directions of the long axis and the short axis can be realized by changing the ratio of the long axis to the short axis of the porous structures such as diamond-shaped single cells. The combination of gradient holes formed by the variation of the long and short axes and the hexagonal shape of the internally-inserted honeycomb can realize additional mechanical response. The gradient pore size of the continuous transition also facilitates proliferation and differentiation of cells. The intervertebral fusion device prosthesis with specific mechanical response has important application value in improving the mechanical and biological compatibility of the implant.

Drawing a gradient porous structure in the interbody fusion cage in the step (4), wherein the drawing mode is as follows: firstly, designing a proper gradient porous size, then drawing a single two-dimensional diamond structure, obtaining rod-shaped two-dimensional diamond unit cells through scanning, then rotating along a symmetry axis, and adjusting the size of a second two-dimensional unit cell 12 after rotation, thus obtaining the three-dimensional unit cell 1. Sequentially, a gradient porous structure can be obtained. The interbody fusion cage prosthesis synthesized by combining the gradient porous structure and the interbody fusion cage frame 2 is stored as a stl model for further print manufacturing.

The printing in the step (5) is formed as follows: inputting the stl model in the steps into the SLM equipment for printing. Printing and forming a compact region and a porous region of the medical implant by adjusting process parameters, wherein the laser power range of the compact region is 180-240W, the scanning speed range is 800-1200mm/s, the scanning interval range is 60-80 mu m, and the layer thickness range is 30-50 mu m; the laser power of the porous region ranges from 160W to 200W, the scanning speed ranges from 1200 mu m/s to 2000 mu m/s, the scanning interval ranges from 60 mu m to 80 mu m, and the layer thickness ranges from 30 mu m to 45 mu m. The dense region is the frame 2, and the porous region is the porous structure.

The medical alloy used in the additive manufacturing in the step (5) is TA ₂ 、TC ₄ One of them.

As can be seen from fig. 9 and 12, the gradient porous structure has a gradient pore structure, thus facilitating proliferation, adhesion, and bone ingrowth of cells. Analysis is performed from mechanical feedback, and firstly, in the vertical direction, namely in the second direction, the gradient hole structure shows a supporting force in Gaussian distribution, namely a longitudinal acting force, so that the horizontal cross beam of the interbody fusion cage frame 2 is prevented from being severely deformed when being subjected to external loading, as shown in fig. 13. In the horizontal direction, the cage frame 2 contracts when being deformed under force, the lateral edges 23 exert inward transverse force on the gradient porous structure, and the supporting force of the gradient porous structure in the horizontal direction also presents gradient distribution, namely, the supporting force gradually decreases from the edge to the center, as shown in fig. 14, so that the better supporting of the lateral edges 23 is facilitated. Along with the continuous increase of the transverse acting force, the intervertebral fusion device provided by the invention can react the transverse acting force to the longitudinal direction so as to further improve the bearing capacity of external loading, realize directional adjustment of force and avoid implantation failure caused by insufficient supporting force.

The invention provides a design and SLM preparation method of a 3D printing interbody fusion cage, wherein a diamond-shaped porous structure with a continuously-changed long and short axes is filled in an interbody fusion cage frame 2 with an embedded hexagonal characteristic, so that an interbody fusion cage prosthesis is formed, the interbody fusion cage prosthesis is prepared by adopting an SLM technology, and the interbody fusion cage prosthesis with specific mechanical response is beneficial to solving the problems of non-uniform mechanical property and poor mechanical property of the interbody fusion cage.

The design idea of the interbody fusion cage presented by the invention is based on a gradient hole structure with adjustable force response, and the gradient hole structure is filled into the interbody fusion cage frame 2 to form the interbody fusion cage prosthesis. Compared with the traditional method, the mechanical properties of the vertebral fusion device are improved mainly in the following aspects. Firstly, the supporting strength of the intervertebral fusion device from two sides to the hole filled in the center is gradually enhanced, and larger supporting force can be provided in the stress direction, so that the suspended frame 2 of the intervertebral fusion device is prevented from being excessively bent under stress. Secondly, the internally-incorporated hexagonal two-sided bending frame 2 can transmit deformation to the internal porous structure when loaded, which can react forces to the loading direction, further the bearing capacity of the interbody cage prosthesis. The medical implant based on the gradient pore structure with adjustable force response, which is prepared by the invention, has wide application prospect in artificial prosthesis.

In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art: the method fills the diamond gradient porous structure with the length axis continuously changed into the interbody fusion cage frame 2, so that the mechanical adjustment of the porous part can be realized. The frame 2 of the interbody fusion cage with the honeycomb hexagon feature can further transmit load to the upper surface and the lower surface 22 of the interbody fusion cage through the porous part during deformation, so that real-time mechanical adjustment is realized. Implantation failure due to insufficient supporting force and stress shielding is avoided. The diamond gradient porous structure with the continuously-changed long and short axes has continuously-changed pore diameter, is favorable for cell adhesion and proliferation, and improves the biocompatibility of the intervertebral fusion device prosthesis.

It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.

Claims

1. A porous structure, characterized in that the porous structure is formed by a plurality of three-dimensional unit cell arrays, each three-dimensional unit cell comprises a first two-dimensional unit cell and a second two-dimensional unit cell which are connected in an intersecting manner, the first two-dimensional unit cells of the three-dimensional unit cells are arranged in an array manner on a plane of any one of the three-dimensional unit cells, and the first two-dimensional unit cells of the three-dimensional unit cells are deformed in a plurality of ways along a first direction on the plane of the first two-dimensional unit cell, so that the supporting strength of the first two-dimensional unit cells in a second direction is gradually enhanced from two sides to the center along the first direction, wherein the first direction and the second direction are perpendicular.

2. The porous structure of claim 1, wherein the first two-dimensional unit cell is in a positive poisson's ratio two-dimensional shape, and wherein the angle between the hypotenuse of the first two-dimensional unit cell and the first direction increases gradually from both sides to the center along the first direction on the plane in which the first two-dimensional unit cell is located.

3. The porous structure of claim 1, wherein nodes of said first two-dimensional unit cells of adjacent two of said three-dimensional unit cells are connected in a plane in which said first two-dimensional unit cell is located.

4. The porous structure of claim 1, wherein the first two-dimensional unit cell is a diamond-shaped unit cell or a hexagonal unit cell;

5. The porous structure of any one of claims 1-4, wherein said first two-dimensional unit cell of each said three-dimensional unit cell is vertically connected to said second two-dimensional unit cell, and wherein said second two-dimensional unit cells of a plurality of said three-dimensional unit cells are arranged in an array on a plane on which said second two-dimensional unit cell is located, with the same length and width dimensions as said second two-dimensional unit cell of different said three-dimensional unit cells.

6. An intervertebral cage, comprising:

a porous structure as claimed in any one of claims 1 to 5;

and a frame, wherein the porous structure is arranged inside the frame.

7. The interbody fusion device of claim 6, wherein said frame has an upper surface, a lower surface, and sides connected between said upper surface and said lower surface, said sides being concave inwardly, wherein a direction of said upper surface relative to said lower surface coincides with said second direction.

8. The interbody fusion device of claim 7, wherein a plurality of said sides are circumferentially spaced between said upper surface and said lower surface.

9. The interbody fusion device of claim 6, wherein said upper surface and said lower surface are each provided with a through hole; the upper surface and the lower surface are respectively provided with a tooth structure.

10. A method for preparing an intervertebral fusion device, wherein the intervertebral fusion device is an intervertebral fusion device as claimed in any one of claims 6-9, the method comprising: