Gradient porous titanium alloy structure and preparation method and application thereof
By designing a gradient porous titanium alloy structure, the problem of porous titanium alloy implants being difficult to match with the large density difference between the inside and outside of the bone was solved, achieving precise matching at the bone injury site and promoting bone tissue growth, making it suitable for complex bone injuries such as the metaphysis.
Patent Information
- Application Number
- CN202510692039.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-27
- Publication Date
- 2026-02-24
AI Technical Summary
Existing porous titanium alloy implants are difficult to effectively match the metaphyseal bone injury site where there is a large difference in density between the inside and outside of the bone. This may lead to delayed or improper treatment, resulting in malunion of fractures and functional impairment, especially affecting bone growth in adolescents.
A gradient porous titanium alloy structure was designed, and a gradient pore distribution was constructed in a single direction based on the Gyroid structure. The porosity change was controlled by an implicit function expression, and implants adapted to different bone structures were prepared by combining 3D printing technology.
It achieves precise matching of bone injury sites, promotes bone tissue growth, shortens treatment time, reduces complications, is suitable for bone structures with large differences in bone density, such as the metaphysis, and provides a fast and convenient treatment plan.
Smart Images
Figure CN121549904A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of medical device manufacturing technology, specifically to a gradient porous titanium alloy structure, its preparation method, and its application. Background Technology
[0002] The metaphysis, a crucial region for bone growth, contains the epiphyseal plate and growth cartilage, making it susceptible to fractures or injuries under external forces. Currently, metaphyseal bone injuries are primarily caused by trauma, disease, or surgical complications, and are characterized by a gradual increase in bone density from the outside in at the site of injury. If metaphyseal bone injuries are not treated promptly or appropriately, they can lead to malunion of the fracture ends, resulting in acute limb problems such as cubitus varus and genu valgum; they can also cause functional impairments such as limited joint movement and muscle atrophy. In adolescents, metaphyseal injuries can also damage the growth plate, thus affecting bone growth.
[0003] Implantable medical devices, as an important treatment for severe or complex metaphyseal injuries, can stabilize the fracture site, promote fracture healing, and minimize the impact on surrounding growing tissues. Common implants for metaphyseal bone injuries include Kirschner wires, plates and screws, flexible intramedullary nails, interlocking intramedullary nails, and bone cement. However, porous titanium alloy implants for metaphyseal bone injuries are relatively rare.
[0004] Medical titanium alloys have become one of the most widely used implant materials in orthopedic repair due to their good biocompatibility, excellent mechanical strength, corrosion resistance, and low cost. Compared with dense porous titanium alloy implants, porous titanium alloy structures obtained through 3D printing have a lower elastic modulus, which is beneficial for osseointegration and bone ingrowth.
[0005] Therefore, a new titanium alloy structure is needed to address the problem of the limited availability of porous titanium alloy implants for bone structure injuries such as those in the metaphysis where there is a large difference in bone density between the inner and outer bone. Summary of the Invention
[0006] The problem this application aims to solve is to provide a gradient porous titanium alloy structure, its preparation method, and its application. This gradient porous titanium alloy structure is designed based on the Gyroid structure of minimal surface structural units. It is controlled by implicit functional expressions to construct a gradient pore distribution in a single direction according to the porosity, which can realize the imitation of different bone structures, better match the bone injury site, and thus improve the tissue growth effect at the bone injury site.
[0007] To solve the above-mentioned technical problems, this application adopts the following technical solution:
[0008] On one hand, this application provides a gradient porous titanium alloy structure, which is designed based on a minimal surface Gyroid structure. The porosity of the Gyroid structure exhibits a gradient distribution only in one direction. The Gyroid structure is controlled using an implicit functional expression, which is:
[0009]
[0010] In the formula: L is the size of the unit cell, x, y, z are the three directions of the spatial coordinate system, and C is the offset;
[0011] The gradient porous titanium alloy structure constructs a gradient pore distribution in the z-direction based on the change in porosity in the z-direction.
[0012] On the other hand, this application provides a method for preparing the above-mentioned gradient porous titanium alloy structure, comprising the following steps:
[0013] Substituting the C value into the implicit function expression, and simultaneously determining the height and diameter of the generated model, the gradient porous titanium alloy structure is 3D modeled using MATLAB software, and an STL file is exported. The STL file is opened using MagicPlot software, and the obtained modeled structure is measured and analyzed. After the measurement and analysis are completed, the STL file is imported into a 3D printer, and 3D printing is performed using titanium alloy printing materials to obtain a titanium alloy matrix. The titanium alloy matrix is then washed and dried to obtain the gradient porous titanium alloy structure.
[0014] Furthermore, the titanium alloy printing raw material includes Ti6Al4V metal spherical powder with a particle size range of 15-45 μm.
[0015] Furthermore, the 3D printer includes an SLM printer.
[0016] Furthermore, the parameters of the SLM printer are set as follows: power 50-200W, powder thickness 30-50μm, scanning spacing 0.06-0.08mm, scanning speed 0.5-2m / s, and spot diameter 60-80μm.
[0017] Preferably, the parameters of the SLM printer are set as follows: power 75W, powder thickness 30μm, scanning spacing 0.06mm, scanning speed 0.9m / s, and spot diameter 60μm.
[0018] Furthermore, the washing step includes washing the titanium alloy substrate sequentially with acetone, anhydrous ethanol, and deionized water.
[0019] Furthermore, the drying temperature is 50°C.
[0020] Furthermore, the method for obtaining the C value includes:
[0021] The porosity p of the implant is determined by obtaining the pore size and porosity of the bone structure at the site of interest, as well as the continuous linear change of the porosity; the C value is calculated based on the porosity.
[0022] Furthermore, the relationship between the porosity p and the C value is p = 0.4996 - 0.3362C.
[0023] Furthermore, this application provides the application of the above-described gradient porous titanium alloy structure or the above-described method in the preparation of implants at sites of bone structural damage.
[0024] Furthermore, the bone structure includes the metaphysis.
[0025] This application has the following beneficial effects:
[0026] (1) The gradient porous titanium alloy structure provided in this application can prepare bone implants with different porosities without increasing the complexity of the design, thereby realizing the restoration of the real bone structure, promoting the growth of bone tissue, enhancing the bone integration effect, and reducing obstacles for clinical application.
[0027] (2) The gradient porous titanium alloy structure provided in this application can be customized to design bone injury implants with varying pore sizes and dimensions for each patient's bone injury site by simply adjusting the parameters. It is especially suitable for bone structures with large differences in internal and external bone density, such as the metaphysis. It can not only provide a quick and convenient solution when facing various irregular bone injuries, but also enable early implantation, thereby shortening treatment time, reducing complications, and promoting rehabilitation. Attached Figure Description
[0028] To more clearly illustrate the technical solutions in this disclosure, the accompanying drawings used in some embodiments of this disclosure will be briefly described below.
[0029] Figure 1 Three-dimensional modeling of the gradient porous titanium alloy structure Bi-rod and the regular porous titanium alloy structure Re-rod designed for this application (a. Bi-rod, b. Re-rod);
[0030] Figure 2 Images of Bi-rod and Re-rod (a. front, b. top, c. bottom; where the left side is Bi-rod and the right side is Re-rod);
[0031] Figure 3 Electron micrographs of Bi-rod and Re-rod (a. top view, b. bottom view; where the left side is Bi-rod and the right side is Re-rod);
[0032] Figure 4 The mechanical property test results for Bi-rod and Re-rod (a. compressive strength, b. elastic modulus);
[0033] Figure 5 Three-dimensional reconstruction images of Bi-rod and Re-rod (a. Bi-rod, b. Re-rod);
[0034] Figure 6 Pore size distribution and porosity analysis diagrams for Bi-rod and Re-rod (a. Pore size distribution diagram, b. porosity analysis diagram);
[0035] Figure 7 The implantation process for Bi-rod and Re-rod;
[0036] Figure 8 X-ray images of the implantation sites on the experimental rabbits (a. Bi-rod, b. Re-rod);
[0037] Figure 9 Three-dimensional reconstruction images of the implantation site and surrounding area after Bi-rod or Re-rod implantation in experimental rabbits (a. Week 4, b. Week 8; where the left side is Bi-rod and the right side is Re-rod);
[0038] Figure 10 Bone volume fraction at the implantation site in rabbits at four and eight weeks after Bi-rod or Re-rod implantation;
[0039] Figure 11 Example histological analysis and statistical results of bone ingrowth area ratio at the fourth and eighth weeks after Bi-rod or Re-rod implantation in experimental rabbits (a. Example histological analysis; b. Statistical results of bone ingrowth area ratio). Detailed Implementation
[0040] The technical solutions in some embodiments of this disclosure will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this disclosure, and not all embodiments. Based on the embodiments provided in this disclosure, all other embodiments obtained by those skilled in the art are within the scope of protection of this disclosure.
[0041] Example 1: Obtaining the C value
[0042] To obtain the C value, follow these steps:
[0043] By using the microstructural information of the bone structure at the site of interest, the porosity p, pore size, and continuous linear variation of porosity of the implant are determined. The value of C is calculated according to the formula p = 0.4996 - 0.3362C.
[0044] Example 2: Preparation of Gradient Porous Titanium Alloy Structure
[0045] Substituting the C value calculated in Example 1 into the implicit function expression (Equation 1) of the minimal surface Gyroid structure, and simultaneously determining the height and diameter of the generated model, the gradient porous titanium alloy structure was three-dimensionally modeled using MATLAB software. After modeling, an STL format file was exported. The STL format file was opened using MagicPlot software to perform measurement and analysis on the modeled structure. After the measurement and analysis were completed, the STL format file was imported into an SLM printer (Suzhou Solo Additive AF). In a 3D printing process (250, China), Ti6Al4V spherical metal powder with a particle size range of 15–45 μm was used as the raw material. The printing was performed with parameters of 50–200 W power, powder layer thickness of 30–50 μm, scanning spacing of 0.06–0.08 mm, scanning speed of 0.5–2 m / s, and spot diameter of 60–80 μm to obtain a titanium alloy matrix. The titanium alloy matrix was then washed sequentially with acetone, anhydrous ethanol, and deionized water, and dried in an oven at 40–100 °C to obtain the gradient porous titanium alloy structure.
[0046] Formula 1:
[0047] In the formula: L is the size of the unit cell, x, y, z are the three directions of the spatial coordinate system, and C is the offset;
[0048] Meanwhile, based on the continuous linear change of porosity p in the z-direction, a gradient pore distribution is constructed for the gradient porous titanium alloy structure in the z-direction.
[0049] The preferred particle size of the Ti6Al4V metal spherical powder is 15 μm.
[0050] The preferred printing power is 75W;
[0051] The powder layer thickness is preferably 30 μm;
[0052] The preferred scanning spacing is 0.06 mm;
[0053] The preferred scanning speed is 0.9 m / s;
[0054] The preferred spot diameter is 60 μm;
[0055] The preferred drying temperature is 50°C.
[0056] Comparative Example 1
[0057] The steps for preparing the regular porous titanium alloy scaffold in Comparative Example 1 are the same as in Example 2; the only difference between Comparative Example 1 and Example 2 is that:
[0058] The porosity of the non-gradient porous titanium alloy structure exhibits a trapezoidal distribution in the z-direction.
[0059] Example 1: Characterization and Verification of Gradient Porous Titanium Alloy Structure
[0060] Existing research has found that the microstructure of bone exhibits a gradual decrease in porosity from cancellous bone to cortical bone. Therefore, designing... Figure 1 The gradient porous titanium alloy structure Bi-rod shown was fabricated according to the preferred scheme described in Example 2. The Bi-rod has a height of 6 mm, a diameter of 5 mm, and a porosity that decreases linearly from 80% at the top surface (z=6) to 5% at the bottom surface (z=0) to mimic the porosity change from cancellous bone to cortical bone in the bone microstructure. Simultaneously, a regular porous titanium alloy structure Re-rod with a height of 6 mm, a diameter of 5 mm, and a uniform porosity of 80% was prepared as a control group, following the method described in Comparative Example 1. The top and bottom surfaces of the Bi-rod and Re-rod were imaged using a scanning electron microscope (SEM, FEI Quanta 250, USA) at an accelerating voltage of 20 kV and a magnification of 70X. The imaging results are shown below. Figure 3 As shown.
[0061] The results showed that the printed Bi-rod and Re-rod exhibited no breakage, burrs, or deformation, and were suitable as materials for subsequent experiments.
[0062] Experiment Example 2: Determination of Mechanical Properties of Gradient Porous Titanium Alloy Structure
[0063] The mechanical properties of Bi-rod and Re-rod in Experiment 1 were tested using a commercial mechanical testing machine (MTS, Instron 5944). The specific testing method was as follows: the material to be tested was placed vertically in the center of the test bench, and the loading speed was set to 0.5 mm / min. The compressive modulus of each support was determined by the slope of the straight line at the beginning of the compressive stress-strain curve. The results are as follows: Figure 4 As shown.
[0064] The results showed that Bi-rod had higher compressive strength and elastic modulus than Re-rod, indicating that the gradient porous structure brought better mechanical properties and that Bi-rod could provide better mechanical support as a bone implant.
[0065] Experimental Example 3: Pore Size and Porosity Detection of Gradient Porous Titanium Alloy Structure
[0066] The Bi-rod and Re-rod in Experiment 1 were scanned using a Micro-CT scanner (Sky Scan 1275, Bruker, Germany). The scanning parameters were 80 kV voltage, 75 mA current, and a rotation step size of 0.2°. Reconstruction was then performed using CTAN (Sky Scan), and the pore size, porosity, and connectivity of the stents were analyzed, yielding the following results: Figure 5 The three-dimensional reconstruction image shown and Figure 6 The aperture distribution diagram is shown.
[0067] The results show that the connectivity of both Bi-rod and Re-rod is 100% through analysis of the 3D reconstruction images. Further processing of the 3D reconstruction images reveals that the average porosity of Bi-rod is 64.18%, while that of Re-rod is 84.67%. This indicates that the pores of the printed scaffold are interconnected, which is beneficial for the transport of blood and nutrients. Furthermore, the pore size distribution of Bi-rod is relatively dispersed, ranging from 200 to 800 nm, while the pore size distribution of Re-rod is concentrated in the 600-800 nm range. This demonstrates that this application successfully constructed a gradient porous titanium alloy structure.
[0068] Experiment Example 4: Animal Experiments with Gradient Porous Titanium Alloy Structures
[0069] In this experiment, all animal procedures were strictly performed in accordance with international animal protection guidelines, and all experimental protocols were approved by the Animal Ethics Committee of the Western Theater Command General Hospital (Approval No. 2024EC7-ky030). A total of 12 male New Zealand white rabbits were used. Bi-rod and Re-rod from Experiment 1 were inserted near one femoral condyle of each rabbit. Euthanasia was performed at two time points (4 weeks and 8 weeks) for further experimental evaluation. The specific experimental procedure is as follows:
[0070] (1) Implantation of porous titanium alloy structure
[0071] One week prior to the Bi-rod and Re-rod implantation surgery, rabbits were acclimatized in the laboratory and fasted for 24 hours before surgery. During the surgery, isoflurane inhalation anesthesia (Shandong Anter Animal Husbandry Technology Co., Ltd.) was used, followed by shaving and disinfection. A 2cm incision was made near the lateral femoral condyle, separating the skin and fascia layers to expose the femur. A 5mm diameter, 6mm deep hole was drilled perpendicular to the femoral shaft from the lateral cortex. The porous titanium alloy structure was then implanted into the prepared hole (implantation process as follows). Figure 7 (As shown), the skin and fascia layers were then sutured, and 400,000 IU of penicillin was injected intramuscularly 3 days postoperatively to prevent incision infection.
[0072] (2) X-ray examination of the implantation site
[0073] On the second day after surgery, all experimental rabbits underwent X-ray examination (HF400VA, MIKASAX-RAY, Japan) with imaging parameters of 44kV and 6.24mAs. The presence of fractures at the implantation site and whether the stent had dislodged were observed and recorded. Two X-ray images, one with Bi-rod and the other with Re-rod implanted, were randomly selected as examples. The results are as follows: Figure 8 As shown.
[0074] The results show that neither Bi-rod nor Re-rod deformed, detached, or broke after implantation, and no fractures occurred at the implantation site, indicating that both Bi-rod and Re-rod have high stability.
[0075] (3) MicroCT analysis of the implantation site
[0076] Six rabbits were sacrificed at weeks 4 and 8 post-implantation. Femurs were harvested, fixed in 10% formalin solution for 72 hours, and prepared as specimens. MicroCT (vivaCT80, SCANCO Medical AG, Switzerland) was used to scan the implantation site and surrounding area (500 μm) with the following parameters: slice spacing 25 μm, voltage 80 kV, and current 114 μA. Three-dimensional reconstruction was then performed using the SCANO MEDICAL μCT Evaluation Program, and the ratio of bone tissue area to total area of the implanted porous titanium alloy structure and surrounding bone was analyzed. Two randomly selected three-dimensional reconstruction images, one with Bi-rod and the other with Re-rod implanted, were used as examples. The results are as follows: Figure 9 The three-dimensional reconstruction image shown and Figure 10 The bone volume fraction (BV / TV) is shown.
[0077] In the 3D reconstruction image, the white area represents the porous titanium alloy structure, and the yellow area represents bone tissue. Figure 9 It can be seen that, in both week 4 and week 8, bone tissue growth on Bi-rod was more uniform, with a certain amount of bone tissue growth throughout the entire porous titanium alloy structure. In contrast, bone tissue growth on Re-rod was uneven, with almost no bone tissue growth observed in some areas. Figure 10 As can be seen, at weeks 4 and 8, the bone volume fraction of Bi-rod was higher than that of Re-rod. This indicates that Bi-rod has a better bone growth effect than Re-rod, and can form more bone tissue around or inside the implanted bone, thus promoting the recovery of bone injury sites. This suggests that Bi-rod is more suitable for bone tissue growth.
[0078] (4) Histological analysis of the implantation site
[0079] The specimens were dehydrated using a series of progressively increasing alcohol washes and embedded in methyl methacrylate. Sections were prepared using a microtome (Leica SP 1600, Leica, Germany), then polished using a micro-abrasive (EXAKT 400CS, Leica, Germany), and finally stained with van Gieson. After staining, the specimens were scanned using a panoramic slide scanner (PANNORAMICSCAN, 3DHISTECH). The scanned images were analyzed using ImagePro Plus software (Silver Spring, MD) to determine the ratio of the actual contact length between the bone and implant surfaces to the possible contact length, denoted as the bone ingrowth area ratio. The results are shown below. Figure 11 As shown.
[0080] The results showed that, compared to Re-rod, Bi-rod had better early bone integration and sustained bone regeneration capabilities, which could reduce the time required for patients to bear weight.
[0081] In summary, this application mimics the porosity changes in bone structure from cancellous bone to cortical bone, providing a method for preparing a gradient porous titanium alloy structure. This method can customize implants using titanium alloy raw materials that have been used in the field for a long time and have high biocompatibility, based on the porosity differences at individual bone injury sites. It not only has good stability but also has a better bone growth promoting effect, which can effectively promote the healing of bone injury sites. It is particularly suitable for bone structures with uneven porosity distribution, such as the metaphysis.
[0082] The above description is merely a preferred embodiment of this disclosure. It should be understood that this disclosure is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in various other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or techniques or knowledge in related fields. Any modifications and variations made by those skilled in the art that do not depart from the spirit and scope of this disclosure should be within the protection scope of the appended claims.
Claims
1. A gradient porous titanium alloy structure, characterized in that, The gradient porous titanium alloy structure is designed based on a minimal surface Gyroid structure. The porosity of this structure exhibits a gradient distribution only in one direction. The Gyroid structure is controlled using an implicit functional expression, which is: In the formula: L is the size of the unit cell, x, y, z are the three directions of the spatial coordinate system, and C is the offset; The gradient porous titanium alloy structure constructs a gradient pore distribution in the z-direction based on the change in porosity in the z-direction.
2. The method for preparing the gradient porous titanium alloy structure as described in claim 1, characterized in that, Includes the following steps: Substitute the C value into the implicit function expression, and simultaneously determine the height and diameter of the generated model. Use MATLAB software to perform three-dimensional modeling of the gradient porous titanium alloy structure and export the STL file. Open the STL file using MagicPlot software and perform measurement and analysis on the obtained modeled structure; After the measurement and analysis are completed, the STL file is imported into the 3D printer, and 3D printing is performed using titanium alloy printing material to obtain a titanium alloy matrix; The titanium alloy matrix is washed and dried to obtain the gradient porous titanium alloy structure.
3. The method according to claim 2, wherein the titanium alloy printing raw material comprises Ti6Al4V metal spherical powder with a particle size range of 15-45 μm.
4. The method according to claim 2, characterized in that, The 3D printers include SLM printers.
5. The method according to claim 4, characterized in that, The parameters of the SLM printer are set as follows: power 50-200W, powder thickness 30-50μm, scanning spacing 0.06-0.08mm, scanning speed 0.5-2m / s, and spot diameter 60-80μm.
6. The method according to claim 2, characterized in that, The washing steps include: sequentially washing the titanium alloy substrate with acetone, anhydrous ethanol, and deionized water; And / or, the drying temperature is 40–100°C.
7. The method according to claim 2, characterized in that, The method for calculating the C value includes: The porosity p of the implant is determined by obtaining the pore size and porosity of the bone structure at the site of interest, as well as the continuous linear change of the porosity. The C value is calculated based on the porosity p.
8. The method of claim 7, characterized in that, The relationship between the porosity and the C value is p = 0.4996 - 0.3362C.
9. The application of the gradient porous titanium alloy structure as described in claim 1 or the method described in any one of claims 2 to 8 in the preparation of implants for bone structure injuries.
10. The application according to claim 9, characterized in that, The bone structure includes the metaphysis.