High-strength porous metal implant material and method for producing the same

Abstract

A high-strength porous metal implant material comprises a three-dimensional interconnected porous structure with a porosity of 55-90%, and two or more reinforcing elements distributed at the edge of the porous structure. The reinforcing elements are integrally formed and seamlessly bonded to each other and to the porous material. The reinforcing element structure of the porous metal implant material improves the material's mechanical strength. Its porous structure promotes bone tissue ingrowth into the porous metal's pores, facilitates osteoblast adhesion, differentiation, and growth, enhances the integration of the implant with bone, and achieves long-term biological fixation of the implant to human tissue. The thickness of the reinforcing elements, their positional distribution, or their volume percentage within the overall material can be adjusted according to the stress or mechanical performance requirements of the bone repair or bone defect site, thereby enabling the production of bone filling and implant materials that meet the different mechanical strength requirements of various locations.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of porous materials, in particular to a high-strength porous metal implant material and a preparation method thereof. BACKGROUND

[0002] Bone defects caused by trauma, tumors, infections and other reasons are common clinical diseases in orthopedics. At present, the main methods to solve this problem are autologous bone transplantation, allogeneic bone transplantation or implanting various artificial bone material substitutes. Autologous bone transplantation mainly has the defects of limited bone quantity, additional damage, infection, bleeding, etc. Allogeneic bone has problems such as high price and immune rejection. A variety of bone material substitutes are increasingly used in research and clinical applications, such as hydroxyapatite, bioceramics, organic polymer medical materials, medical metal materials, etc. In recent years, different material porous metal materials represented by porous stainless steel, porous cobalt alloy, porous magnesium, porous nickel, porous tantalum, porous titanium and its alloy have gradually become a research hotspot due to their good biocompatibility, better compressive strength and elastic modulus close to bone.

[0003] The mechanical strength and porosity of porous metal have always been a pair of contradictory points. On the one hand, by increasing the porosity of the porous material, new bone grows into the pore structure of the porous metal, which is beneficial to the adhesion, differentiation and growth of osteoblasts, enhances the combination of the implant and the bone, and realizes the fixation of the implant and the human tissue. On the other hand, while increasing the porosity of the porous material, the mechanical strength of the porous material is reduced, so that it cannot bear certain stress and load after being implanted into the human body. To solve this problem, the prior art adopts laser welding or resistance welding to combine the dense metal with the porous metal. The dense metal meets the fatigue resistance requirement under dynamic load, and the porous metal meets the requirement of firmly combining the prosthesis surface with the patient's bone, for example, patent CN106236328A discloses combining a porous titanium sleeve with a dense metal handle body by using pulse laser welding technology, and patent CN111012551A discloses realizing the close combination of the porous surface structure and the base structure by resistance welding. By adopting the above connection mode, there is an obvious welding interface between the porous structure and the dense structure, and there is a risk of falling off between the porous structure and the dense structure as the service time of the implant increases. Therefore, the present application provides a porous material with a reinforcing body structure. The reinforcing body is integrally formed in the material preparation process, which avoids the problem of welding interface and the inability of the two materials to be integrally formed by the traditional method of first forming the porous material and the dense material respectively and then combining the porous structure and the dense structure by welding. SUMMARY

[0004] The purpose of the present application is to provide a high-strength porous metal implant material which has high porosity and high mechanical strength.

[0005] Another object of the present application is to provide a preparation method of high-strength porous metal implant material, which is prepared by using an organic foam impregnation method, and specifically, through the steps of sponge pretreatment, slurry preparation, green body production by slurry hanging, reinforcement production, low-temperature drying, and sintering.

[0006] Another object of the present application is to provide the application of the above-mentioned high-strength porous metal implant material in the biomedical field, especially for the repair and reconstruction of bone defects, and for trauma, spinal, and joint implant products, specifically including bone filling products, intervertebral fusion cages, hip joint products, and the like.

[0007] The object of the present application is achieved by the following technical solutions:

[0008] A high-strength porous metal implant material is composed of a three-dimensional interconnected porous structure with a porosity of 55-90% and two or more reinforcements distributed on the edge of the porous structure, and the reinforcements are integrally formed and combined without nodes between the reinforcements and the porous material.

[0009] Further, the porous structure is a connected open hole surrounded by a cavity wall, the cavity wall is an axially hollow structure, the cavity wall has a hole in the radial direction, the porosity of the porous structure is uniformly distributed, and the hole in the radial direction of the cavity wall is a single-stage hole.

[0010] Further, the high-strength porous metal implant material is in the shape of a cube, a cuboid, a trapezoidal body, a cylindrical body, or an irregular body. Further, the high-strength porous metal implant material is made of titanium, tantalum, or niobium.

[0011] Further, the preparation method of the high-strength porous metal implant material comprises the following steps: using an organic foam impregnation method to prepare the high-strength porous metal implant material.

[0012] Further, the preparation method of the high-strength porous metal implant material comprises the following steps:

[0013] 1) Sponge pretreatment: select an organic sponge with a certain pore size as a template, cut it into the required shape according to the requirements, and immerse it in a NaOH solution for pretreatment;

[0014] 2) Slurry preparation: weigh a certain amount of metal powder, binder, dispersant, crosslinking agent, and deionized water, and mix and stir them uniformly to prepare a slurry;

[0015] 3) Green body production by slurry hanging: immerse the organic template prepared in step 1) in the slurry prepared in step 2), remove the excess slurry, and obtain a porous green body after drying.

[0016] 4) Reinforcement production:

[0017] ① Place the V-shaped tooling on the horizontal base support, so that the tooling is in a horizontal position; ② Take an appropriate amount of slurry prepared in step 2) and lay it flat on the V-shaped tooling, immerse the part to be formed into the tooling slurry, and vibrate on the sieve instrument to level the slurry; ③ Add an appropriate amount of liquid nitrogen to the tooling, take out the slurry after quick freezing, and use a knife to level the surface of the reinforcement and the porous structure, then place it in a refrigerator at a temperature of -15℃ to -25℃ for 5 to 30 minutes; ④ Take out the green body to make the next adjacent reinforcement, immerse the next part to be impregnated into the tooling slurry at room temperature for 10 to 90 seconds, at this time the surface of the end point of the frozen reinforcement has a little slurry melting, and the slurry of the reinforcement being formed is integrated and continuous, and the slurry is leveled and then solidified by liquid nitrogen cooling, so that the joint between adjacent reinforcements is formed without interface.

[0018] 5) Low-temperature drying: low-temperature drying the green body prepared in step 4) at a temperature less than 20℃.

[0019] 6) Sintering: place the green body obtained in step 5) into a furnace for sintering to obtain a high-strength porous metal implant material.

[0020] Further, immerse the end point of the frozen reinforcement into the room temperature slurry for 10 to 90 seconds for rewarming, the short rewarming time causes the surface of the end point of the frozen reinforcement to have a little slurry melting, then immerse the next adjacent part to be impregnated into the tooling slurry, vibrate on the sieve instrument to level the slurry, and then add an appropriate amount of liquid nitrogen to quickly freeze the slurry, so that the joints between adjacent reinforcements prepared in the previous steps are integrated. In this process, only the end point of the frozen reinforcement is immersed in the room temperature slurry, and the rest of the frozen reinforcement does not have obvious melting deformation in the air, avoiding defects. Since the slurry is in a water-based environment, the heat capacity of water and air is different, so the surface slurry of the end point of the frozen reinforcement immersed in the room temperature slurry melts, and the frozen reinforcement not immersed in the slurry does not have obvious melting deformation in the air.

[0021] Further, the preparation method of the high-strength porous metal implant material, the V-shaped tooling is made of a low thermal conductivity material, and the low thermal conductivity material includes any one of polypropylene, polyvinyl chloride, polystyrene, polyurethane, or polyamide plastic material. The reason for choosing a low thermal conductivity plastic material to make the tooling mold is to facilitate the demolding of the reinforcement after quick freezing and solidification. The thermal conductivity of plastic is much lower than that of stainless steel mold (about 1 / 500), and when liquid nitrogen is used to quickly freeze and solidify the slurry, the temperature at the interface between the plastic and the slurry is not too low, the ice adhesion strength at the interface is not high, and the reinforcement is easy to separate from the mold.

[0022] Further, the binder used in the slurry preparation process is polyvinyl alcohol (PVA) or polyvinyl butyral (PVB). The dispersant used in the present application is stearic acid, polyethylene glycol 400 or chitosan. The cross-linking agent used in the present application is glyoxal or glutaraldehyde.

[0023] Further, the preparation method of the high-strength porous metal implant material controls the thickness of the reinforcement by adjusting the amount of slurry in the V-shaped tool and the volume fraction of the green body immersed in the slurry. The thickness of the reinforcement increases with the increase of the amount of slurry in the V-shaped tool and the volume fraction of the green body immersed in the slurry. Further, the reinforcement can be distributed on the edges or the entire side of the porous material.

[0024] Further, the high-temperature sintering is carried out in a vacuum or inert gas environment.

[0025] Further, the preparation method of the high-strength porous metal implant material, the low-temperature drying includes cold air drying at a temperature less than 20℃. The green body with reinforcement is in a frozen state. The low-temperature drying method is selected to avoid the deformation of the reinforcement caused by the increase of the rheological property of the slurry in the reinforcement during conventional high-temperature drying, and to slow down the evaporation speed of water in the reinforcement to make the polyvinyl alcohol adhesive uniform, further increasing the uniformity of the reinforcement.

[0026] Further, the application of the high-strength porous metal implant material is used for trauma, spine and joint implant products to repair and reconstruct bone defects and bone damage.

[0027] The beneficial effects of the present application are:

[0028] (1) The present application combines porous metal materials with reinforcement to fully utilize their respective advantages. The prepared high-strength porous metal implant material has high mechanical properties and high three-dimensional pore connectivity, greatly improving the compressive strength of the material, and has strong long-term implant stability. Compared with porous metal materials without reinforcement, the compressive strength is significantly improved, and it is especially suitable for parts that need to bear more weight.

[0029] (2) The three-dimensional interconnected porous structure with a porosity of 55-90% provided by the application promotes the growth of bone tissue into the pore structure of the porous metal, is beneficial to the adhesion, differentiation and growth of osteoblasts, enhances the combination of the implant and the bone, and realizes the long-term biological fixation of the implant and the human tissue. The material obtained by using metal powder and a polymer scaffold with specific sizes and precisely controlling the preparation process not only has excellent mechanical properties, but also has improved three-dimensional interconnected porosity and fluid transfer capacity due to the existence of the axial hollow holes and the radial holes of the cavity wall. The porous metal material includes at least two continuous channels, i.e., the three-dimensional interconnected channels surrounded by the cavity wall and the axial hollow holes of the cavity wall. When the porous metal material is used as a bone tissue material, the material has strong seepage capacity, is beneficial to the transmission of body fluids and nutrient cells in the material, has strong fluidity, and promotes tissue growth and bone conduction.

[0030] (3) The thickness, position distribution relationship or volume ratio of the reinforcing body in the overall material can be adjusted according to the stress or mechanical property requirement of the human bone repair or bone defect site, so as to realize the preparation of bone filling and bone implant materials that meet the requirements of different parts and different mechanical strengths.

[0031] (4) The application provides a preparation method of a high-strength porous metal implant material, which is simple to operate and suitable for industrial production. The prepared material has the characteristics of integral forming between the reinforcing body and the porous material, between the reinforcing bodies, no joint at the joint, and no interface fusion. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The schematic view of the high-strength porous metal implant material with twelve reinforcing body structures on the edges of the cubic shape. DETAILED DESCRIPTION

[0033] The application is further illustrated by the following examples: According to the following examples, the application can be better understood. However, it is easy for those skilled in the art to understand that the specific material ratio, process conditions and results described in the examples are only used to illustrate the application, and should not and will not limit the application described in detail in the claims.

[0034] Example 1

[0035] 1) Sponge pretreatment: select a polyurethane sponge with a pore size of 50 PPI as a template, cut the sponge into a cubic shape with a size of 30mm*30mm*30mm, and immerse it in a 10% NaOH solution for 12h for pretreatment to eliminate the network interval film in the sponge;

[0036] 2) Configuration of slurry: 50 g of tantalum powder, 5 g of polyvinyl alcohol, 0.5 g of polyethylene glycol 400, 0.5 g of glutaraldehyde and 50 g of deionized water were weighed and mixed to prepare a slurry;

[0037] 3) The pretreated organic sponge was immersed in the slurry prepared above, and the excess slurry was removed by squeezing. The immersion was repeated three times. The sponge was dried in an oven at 50°C to obtain a porous green body.

[0038] 4) Preparation of reinforcement: ① A V-shaped tooling cut from a polypropylene plastic material was placed on a horizontal base support, and the tooling was placed in a horizontal position; ② 2 g of the slurry prepared in step 2) was taken and spread on the V-shaped tooling, and one edge of the cubic green body prepared in step 3) was immersed in the tooling slurry. The slurry was leveled on a sifter; ③ An appropriate amount of liquid nitrogen was added to the tooling, and the slurry was frozen. The reinforcement was removed and leveled with the surface of the porous structure using a knife. The reinforcement was then placed in a refrigerator at -15°C for 30 min; ④ The green body was removed, and the next adjacent edge reinforcement was prepared. The next edge to be immersed was immersed in the tooling slurry at room temperature for 10 s. At this time, a small amount of slurry on the surface of the frozen reinforcement end point was melted, and the slurry formed a continuous body with the reinforcement being formed. The slurry was leveled and then solidified by liquid nitrogen cooling; steps ①-④ were repeated to sequentially prepare the adjacent edge reinforcements, until all twelve edge reinforcements of the square green body were completed, and the interface between the edge reinforcements was formed without interface.

[0039] 5) Low-temperature drying: The green body prepared in step 4) was subjected to cold air drying at a temperature of 18°C for 10 h.

[0040] 6) Sintering: The dried green body obtained in step 5) was placed in a furnace for sintering. The green body was slowly heated from room temperature to 580°C at a heating rate of 2°C / min under vacuum, and then held for 6 h. Then, the green body was slowly heated to 1500°C at a heating rate of 2°C / min, and then held for 6 h. Then, the green body was slowly heated to 1900°C at a heating rate of 6°C / min, and then held for 6 h. Then, the furnace was cooled, and a cubic high-strength porous tantalum implant material was obtained.

[0041] The overall compressive strength of the prepared cubic high-strength porous tantalum implant material with twelve edge reinforcement structures was 85 MPa, and the porosity of the porous structure was 85.6%. The porous structure was a connected open pore surrounded by a cavity wall. The cavity wall was an axial hollow structure, and the cavity wall had a radial hole. The porosity of the porous structure was uniformly distributed, and the radial hole of the cavity wall was a single-stage hole. The size of the open pore surrounded by the cavity wall was 400-700 μm, the size of the hollow hole of the cavity wall was about 60 μm, and the size of the radial hole of the cavity wall was 2-8 μm.

[0042] Comparative Example 1

[0043] The preparation method of the non-reinforced porous tantalum implant material of the comparative example is substantially the same as that of example 1, except that step 4 is omitted, and the porous green body after impregnation of the slurry is not further made into a reinforcement, but is directly dried at low temperature, and the cubic porous tantalum implant material is prepared after vacuum high-temperature sintering.

[0044] The overall compressive strength of the prepared cubic porous tantalum material without reinforcement is 56 MPa, and the porosity of the porous structure is 86.5%. Compared with example 1, the compressive strength of the porous material with reinforcement is significantly improved.

[0045] Example 2

[0046] 1) Sponge pretreatment: select a polyurethane sponge with a pore size of 90 PPI as a template, cut the sponge into a cubic shape of 30 mm*30 mm*30 mm, and immerse it in a 10% NaOH solution for 12 h for pretreatment to eliminate the network interval film in the sponge;

[0047] 2) Configure the slurry: weigh 50 g of niobium powder, 5 g of polyvinyl alcohol, 0.5 g of polyethylene glycol 400, 0.5 g of glyoxal, and 50 g of deionized water, and mix and stir uniformly to prepare the slurry;

[0048] 3) Put the pretreated organic sponge into the prepared slurry and impregnate it, squeeze out the excess slurry, and repeat the impregnation until the weight of the green body no longer increases, then dry it in a 50°C oven to obtain a porous green body.

[0049] 4) Make the reinforcement: ① Cut the V-shaped tooling of polypropylene plastic material into a shape and place it on a horizontal base support, so that the tooling is in a horizontal position; ② Take 4 g of the slurry prepared in step 2) and lay it flat on the V-shaped tooling, immerse one edge of the cubic green body prepared in step 3) in the slurry, and find the level of the slurry on the sifter; ③ Add an appropriate amount of liquid nitrogen to the tooling, take out the frozen slurry, and use a knife to flatten the surface of the reinforcement and the porous structure, then place it in a freezer at -25°C for 5 min; ④ Take out the green body to make the next adjacent edge reinforcement, immerse the next edge to be impregnated in the room temperature slurry for 90 s, at which time the surface of the end point of the frozen reinforcement has a little slurry melting, and the slurry forms an integrated and continuous body with the reinforcement being formed; after the slurry is leveled, it is cooled and solidified by liquid nitrogen; repeat steps ①-④ to make the adjacent edge reinforcements in turn, until all the edge reinforcements of the cubic green body are completed, and the interface between the edge reinforcements can be formed without interface.

[0050] 5) Low-temperature drying: dry the green body prepared in step 4) at a temperature of 18°C for 10 h.

[0051] 6) Sintering: the dried green body obtained in step 5) is placed in a furnace for sintering, the green body is slowly heated from room temperature to 580°C at a heating rate of 2°C / min under vacuum, and kept for 6 hours, then continues to be slowly heated to 1500°C at a heating rate of 2°C / min, and kept for 6 hours, then continues to be heated to 1900°C at a heating rate of 6°C / min, and kept for 6 hours, then cools down with the furnace, to obtain a cubic high-strength porous niobium implant material.

[0052] The overall compressive strength of the prepared cubic high-strength porous niobium implant material with reinforcement is 95 MPa, and the porosity of the porous structure is 55%. This embodiment reduces the overall porosity of the material by selecting a polyurethane sponge with a smaller porosity as the organic template, and increasing the number of slurry impregnations to increase the thickness of the filaments of the porous material, and improves the overall mechanical strength of the material by increasing the thickness of the reinforcement and increasing the volume fraction of the reinforcement in the overall material. The porous structure is a connected open pore surrounded by a cavity wall, the cavity wall is an axially hollow structure, the cavity wall has a hole in the radial direction, the porosity of the porous structure is uniformly distributed, and the hole in the radial direction of the cavity wall is a single-stage hole. The size of the open pore surrounded by the cavity wall is 200-500 μm, the size of the hollow hole in the cavity wall is about 30 μm, and the size of the hole in the radial direction of the cavity wall is 1-5 μm.

[0053] Example 3

[0054] The preparation method of the high-strength porous titanium implant material of this embodiment is substantially the same as that of Example 1, except that the tantalum powder is changed to titanium powder, the binder in the slurry is PVB, the sponge is cut into a trapezoidal shape, the sponge is pretreated, the slurry is configured, the green body is made by hanging slurry, the reinforcement is made, after low-temperature drying, the green body is slowly heated from room temperature to 580°C at a heating rate of 2°C / min under N2 protection, and kept for 6 hours, then continues to be slowly heated to 1250°C at a heating rate of 2°C / min, and kept for 6 hours, then cools down with the furnace, to obtain a trapezoidal high-strength porous titanium implant material.

[0055] The overall compressive strength of the prepared porous titanium material with reinforcement in a trapezoidal shape is 87 MPa, and the porosity of the porous structure is 83.5%. The porous titanium implant material has a three-dimensionally connected porous structure, the pores are uniformly distributed, there is no node fusion between the edge reinforcement of the porous structure and the porous material, and a good continuity is formed between the two, and there is no interface fusion at the end point of the reinforcement, and the reinforcement is integrally formed.

[0056] Example 4

[0057] The preparation method of the high-strength porous tantalum implant material of the embodiment with four side surfaces of a cubic shape distributed with the reinforcement structure is substantially the same as that of Embodiment 1, except that in the process of making the reinforcement, one side surface of the prepared cubic green body is immersed in the V-shaped tool slurry as a whole, and after the slurry is rapidly frozen by liquid nitrogen, it is taken out, the cubic body is rotated by 90°, the adjacent side surface is immersed in the V-shaped tool slurry at room temperature, and then liquid nitrogen is used for freezing to make the adjacent reinforcement, and the above steps are repeated until four continuous side surface reinforcement structures are formed.

[0058] Embodiment 5

[0059] The preparation method of the high-strength porous tantalum implant material of the embodiment with four side surfaces of a cubic shape distributed with the reinforcement structure is substantially the same as that of Embodiment 1, except that in the process of making the reinforcement, one side surface of the prepared cubic green body is immersed in the V-shaped tool slurry as a whole, and after the slurry is rapidly frozen by liquid nitrogen, it is taken out, the cubic body is rotated by 90°, the adjacent side surface is immersed in the V-shaped tool slurry at room temperature, and then liquid nitrogen is used for freezing to make the adjacent reinforcement, and the above steps are repeated until four continuous side surface reinforcement structures are formed.

Claims

1. A high-strength porous metal implant material, characterized in that, The high-strength porous metal implant material consists of a three-dimensional interconnected porous structure with a porosity of 55-90%, and two or more reinforcing bodies distributed at the edge of the porous structure. The reinforcing bodies are integrally formed and bonded to the porous material without joints. The porous structure is a series of interconnected openings enclosed by a cavity wall. The cavity wall is an axially hollow structure with radial pores. The porosity of the porous structure is uniformly distributed, and the radial pores of the cavity wall are single-stage pores. The high-strength porous metal implant material is prepared using an organic foam impregnation method, including the following specific steps: 1) Sponge pretreatment: Select an organic sponge with a certain pore size as a template, cut it into the required shape according to the requirements, and soak it in NaOH solution for pretreatment; 2) Prepare the slurry: Weigh a certain amount of metal powder, binder, dispersant, crosslinking agent and deionized water, mix and stir evenly to prepare the slurry; 3) Making green body by slurry application: The organic template prepared in step 1) is immersed in the slurry prepared in step 2) to remove excess slurry, and then dried to obtain a porous green body; 4) Create reinforcements: ① Place the V-shaped fixture on the horizontal base support to ensure it is horizontal; ② Spread an appropriate amount of the slurry prepared in step 2) on the V-shaped fixture, immerse the part of the green body to be reinforced prepared in step 3) into the slurry, vibrate it on a sieve to level the slurry; ③ Add an appropriate amount of liquid nitrogen to the fixture, freeze the slurry quickly, remove it, use a knife to smooth the surface of the reinforcement and porous structure, and then freeze it in a refrigerator at -15℃ to -25℃ for 5 to 30 minutes; ④ Take out the green body to make the next adjacent reinforcement, immerse the next part to be impregnated in the room temperature slurry of the fixture for 10 to 90 seconds. At this time, a small amount of slurry melts on the surface of the frozen reinforcement end, forming an integrated and continuous structure with the slurry of the reinforcement being formed. After the slurry is leveled, it is cooled and solidified by liquid nitrogen, and the reinforcement can achieve interface-free forming at the junction of adjacent reinforcements; 5) Low-temperature drying: The green body prepared in step 4) is dried at a temperature below 20°C; 6) Sintering: The blank obtained in step 5) is placed in a furnace for sintering to obtain a high-strength porous metal implant material.

2. The high-strength porous metal implant material according to claim 1, characterized in that, The high-strength porous metal implant material is in the shape of a cube, cuboid, trapezoid, cylinder, or irregular shape.

3. The high-strength porous metal implant material according to claim 1, characterized in that, The metal is titanium, tantalum, or niobium.

4. The high-strength porous metal implant material according to claim 1, characterized in that, The V-shaped tooling is made of a material with low thermal conductivity, including any one of polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyurethane, or polyamide.

5. The high-strength porous metal implant material according to claim 1, characterized in that, The low-temperature drying in step 5) includes cold air drying.

6. The high-strength porous metal implant material according to claim 1, characterized in that, Step 6) is sintering performed under vacuum conditions or inert gas environment.

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