A magnesium alloy implant device, its preparation method and application

Abstract

The present invention discloses a magnesium alloy implant device, its preparation method and application. The magnesium alloy implant device is composed of a magnesium alloy hollow nail and a magnesium alloy guide pin that is arranged through the inner cavity of the magnesium alloy hollow nail. The magnesium alloy hollow nail includes a hollow nail body and a layer of inorganic ceramic coating coated on the inner and outer surfaces of the hollow nail body. The self-corrosion potential of the magnesium alloy hollow nail is higher than that of the magnesium alloy guide pin. The material of the magnesium alloy hollow nail body includes the following components in percentage by mass: 1.0-6.0% Ca, 0.8-1.2% Zn, less than 0.1% total impurities, and the rest is Mg. The magnesium alloy guide pin is made of the same material as the magnesium alloy hollow nail body. The preparation method includes three steps: preparing a magnesium alloy rod, separately processing to form the magnesium alloy hollow nail body and the magnesium alloy guide pin, and adding an inorganic ceramic coating to the surface of the magnesium alloy hollow nail body. The above-mentioned implant device has a long service life and is safe to use. It can be widely used in fracture fixation or cruciate ligament reconstruction surgery.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a magnesium alloy implant device, a preparation method and application thereof. Background Art

[0002] Existing medical implants of magnesium alloy bone screws primarily rely on improving the material itself to enhance its corrosion resistance. While this approach improves the corrosion resistance of magnesium alloy bone screws to a certain extent, it does not consider the synergistic effects between the multiple components of the entire implant system, leaving the risk of mechanical failure after implantation. Furthermore, magnesium and magnesium alloys degrade rapidly in body fluids, generating high levels of hydrogen in the short term, which can easily lead to the formation of air pockets. This shortens the mechanical lifespan of the nail after implantation and can also contribute to surgical failure. Furthermore, while current magnesium alloy surface treatment methods can slow the initial degradation rate and reduce the formation of hydrogen air pockets, their primary degradation mechanism is pitting corrosion, resulting in a short mechanical lifespan within the body and a high probability of repair.

[0003] For example, patent publication number CN 108543118B discloses a magnesium alloy fixation screw with controllable degradation in vivo. The magnesium alloy screw body prepared therein is a conventional solid screw structure with limited clinical application. An oxide film layer with a thickness of 50 to 200 μm is formed on the magnesium alloy screw body, and a degradable polymer coating with a thickness of 1 to 50 μm is coated on the oxide film layer. These two coatings are not only thick but also easy to fall off during use, causing local corrosion, and cannot significantly improve the service life.

[0004] The patent with authorization announcement number CN109295365B discloses a degradable magnesium alloy forming blank. This patent solution only solves the problem of poor forming mechanical properties of magnesium alloy materials, but cannot solve the problem of fast, uneven and uncontrolled degradation rate of magnesium alloys, and the service life is difficult to be significantly extended.

[0005] Therefore, the existing magnesium alloy bone screw implantation instruments need to be further improved. Summary of the Invention

[0006] In response to the above problems, the present invention provides a magnesium alloy implant device, a preparation method and an application thereof. The magnesium alloy implant device is matched with a magnesium alloy hollow nail and a magnesium alloy guide pin. The magnesium alloy implant device has a long service life, provides better mechanical support, and is safer to use.

[0007] To solve the above problems, this application provides the following technical solutions:

[0008] In the first aspect, the present application provides a magnesium alloy implant device, which consists of a magnesium alloy hollow nail and a magnesium alloy guide needle penetrating the inner cavity of the magnesium alloy hollow nail. The magnesium alloy hollow nail includes a hollow nail body and a layer of inorganic ceramic coating covering the inner and outer surfaces of the hollow nail body. The self-corrosion potential of the magnesium alloy hollow nail is higher than the self-corrosion potential of the magnesium alloy guide needle.

[0009] The magnesium alloy hollow nail body material includes the following components in mass percentage: 1.0-6.0% Ca, 0.8-1.2% Zn, total impurities less than 0.1%, and the remainder Mg; the magnesium alloy guide pin is made of the same material as the magnesium alloy hollow nail body.

[0010] Preferably, the magnesium alloy hollow nail body material comprises the following components in the following mass percentages: 2% / 4% Ca, 1% Zn, the total amount of impurities is less than 0.1%, and the rest is Mg.

[0011] Preferably, the inorganic ceramic coating is a micro-arc oxidation coating, which comprises the following components in mass percentage: Mg 20-40%, O 20-40%, P 8-20%, Ca 3-6%, and F 15-25%.

[0012] Optionally, in the magnesium alloy implant device, one end of the hollow nail body is provided with a head, the outer end surface of the head is provided with a fixing groove, a through hole for the magnesium alloy guide pin is provided along the central axis of the hollow nail body, and the outer wall of the hollow nail body is provided with threaded portions distributed along the length. The structure and distribution of the threaded portions are not limited to those in the specific embodiments and the accompanying drawings.

[0013] During use, the hollow nail can be screwed into the target position by the cooperation between the end of the tool and the fixing groove. The fixing groove can adopt various existing slots, not limited to the plum blossom shape in the embodiment.

[0014] Preferably, the threaded portion includes a first threaded portion I and a second threaded portion II sequentially distributed from the head to the tail of the hollow nail body. The threads of the two threaded portions can be arranged differently.

[0015] In a second aspect, the present application provides a method for preparing the aforementioned magnesium alloy implant device, which comprises the following steps:

[0016] S1. preparing magnesium alloy rods;

[0017] S2. Processing the magnesium alloy rod into magnesium alloy hollow nail bodies and magnesium alloy guide pins of different structures using a lathe;

[0018] S3. Processing a layer of inorganic ceramic coating on the surface of the magnesium alloy hollow nail body to obtain a magnesium alloy hollow nail.

[0019] Based on the above processing technology, it can be seen that the magnesium alloy rod is made of the same material as the magnesium alloy hollow nail body and the magnesium alloy guide pin, and the magnesium alloy rod includes the following components in the following mass percentages: 1.0-6.0% Ca, 0.8-1.2% Zn, the total amount of impurities is less than 0.1%, and the rest is Mg.

[0020] Optionally, the preparation method of the magnesium alloy bar is:

[0021] S11. Under the protection of a mixed protective gas atmosphere, melt pure magnesium at 750-800°C and keep warm for 30-60 minutes; add high-purity zinc and pure calcium in corresponding mass percentages, mechanically stir for 3-5 minutes, and keep warm for 20-30 minutes; cool to 700-730°C and cast into an ingot;

[0022] S12. Performing a low-temperature extrusion molding process at an extrusion ratio of 20 to 80, an extrusion temperature of 250 to 400° C., and an extrusion shaft speed of 0.1 to 1.0 mm / s to obtain a magnesium alloy rod. The mass percentages of the components in the prepared magnesium alloy rod are maintained as follows: 1.0 to 6.0% Ca, 0.8 to 1.2% Zn, less than 0.1% total impurities, and the remainder being Mg.

[0023] Optionally, in step S3, the processing method of the inorganic ceramic coating processed on the surface of the hollow nail body is:

[0024] S31, weighing nanohydroxyapatite, ethylene glycol, and triethanolamine in proportion, adding them to water to prepare 1 L of solution A, and placing the solution in an ultrasonic generator for ultrasonic-assisted aging for 40-60 minutes;

[0025] S32. Weigh sodium hexametaphosphate and potassium fluoride dihydrate and add them to water to prepare 1 L of solution B;

[0026] S33, slowly adding solution A to solution B and stirring evenly to obtain solution C;

[0027] S34, placing the cleaned magnesium alloy hollow nail body in solution C as an anode and stainless steel as a cathode to perform micro-arc oxidation treatment;

[0028] S35. Rinse the magnesium alloy hollow nail obtained in the previous step with water and ethanol in turn and dry it.

[0029] Preferably, in the method for preparing the magnesium alloy implant device, the particle size of the nano-hydroxyapatite is less than 100 nanometers.

[0030] In step S31 , the mass volume ratio of nano-hydroxyapatite, ethylene glycol, and triethanolamine is: 3-5 g: 15-25 ml: 25-35 ml.

[0031] Preferably, in step S32, the mass ratio of sodium hexametaphosphate to potassium fluoride dihydrate is: 4-8 g: 14-18 g.

[0032] Preferably, the conditions for the micro-arc oxidation treatment are: a forward voltage of 340-420V, a positive duty cycle of 5-15%, a power frequency of 800-1200Hz, a negative voltage of 50-80V, a negative duty cycle of 5-10%, a positive-to-negative pulse ratio of 5-10:1, and a treatment time of 10-20min.

[0033] Further preferably, the conditions of the micro-arc oxidation treatment are: the micro-arc oxidation process parameters are set to 400 V, frequency 1000 Hz, duty cycle 10%, and treatment time 10 min.

[0034] Thirdly, the application of the aforementioned magnesium alloy implant device in fracture internal fixation and cruciate ligament reconstruction surgery.

[0035] Optionally, the specific application method is: during the operation, after drilling a hole at the fracture site (or surgical site), first screw a stainless steel guide pin into the drilling site for positioning, then install the magnesium alloy hollow nail of the present invention along the stainless steel guide pin, then unscrew the stainless steel guide pin and replace it with a magnesium alloy guide pin, that is, install the magnesium alloy guide pin into the magnesium alloy hollow nail, and complete the fixation of the fracture site by the magnesium alloy implant device. The above-mentioned use of a stainless steel guide pin with higher mechanical strength for positioning first can avoid damage to the magnesium alloy guide pin. In other application methods, it is also possible to directly implant a magnesium alloy guide pin first and then implant a magnesium alloy hollow nail. The application method of cruciate ligament reconstruction surgery is similar and will not be repeated here.

[0036] During the tissue healing process at the fracture site, the magnesium alloy implant device provides long-term mechanical support therefor. After the fracture site is healed, the magnesium alloy implant device has good biocompatibility and will be slowly degraded without any toxic side effects to the body. It is safe and convenient to use.

[0037] The present invention has the following beneficial effects:

[0038] 1. Using magnesium alloy of the same material to prepare magnesium alloy hollow nails and magnesium alloy guide needles can greatly reduce production costs; and the present application makes the self-corrosion potential of the magnesium alloy hollow nail higher than the self-corrosion potential of the magnesium alloy guide needle after the magnesium alloy hollow nail is surface treated and the inorganic ceramic coating is added, so that the implant device undergoes a galvanic corrosion effect after surgical implantation into the lesion site: that is, the magnesium alloy guide needle plays the role of a sacrificial anode due to its low self-corrosion potential, forming relative electrochemical corrosion protection, and the magnesium alloy guide needle starts to corrode directionally from both ends, which can solve the current problems of fast degradation rate, uneven degradation and short service cycle of magnesium alloy; through the above method, the magnesium alloy hollow nail with high open circuit potential is protected, and as the main bearing unit, it can provide longer-term mechanical support, greatly extending the service life of the entire implant device.

[0039] Therefore, the inorganic ceramic coating covering the surface of the aforementioned magnesium alloy hollow nail serves two functions. On the one hand, the coating enables the magnesium alloy guide pin to function as a sacrificial anode, thereby protecting the hollow nail body. On the other hand, the coating has good corrosion resistance in the in vivo environment. After the sacrificial anode degrades and corrodes during the later stages of device implantation, the coating can independently establish a corrosion barrier for the magnesium alloy hollow nail, delaying the degradation of the magnesium alloy hollow nail and the attenuation of its mechanical integrity. It can be seen that the aforementioned implantable device establishes a dual protection effect for the magnesium alloy implantable device through the dual technical means of sacrificial anode and coating. The two are mutually compatible and mutually reinforcing, and can significantly extend the service life of the device.

[0040] 2. The processing materials of the magnesium alloy hollow nail and the magnesium alloy guide pin only contain Mg, Ca, and Zn, and the total impurity content is less than 0.1%, which also has good biosafety. The inorganic ceramic coating has good biocompatibility. Therefore, the magnesium alloy implant device is safe to use.

[0041] 3. The magnesium alloy hollow nail and the magnesium alloy guide pin body are both prepared from magnesium alloy rods only through mechanical processing, and the peripheral coating of the magnesium alloy hollow nail can be completed only through a one-step micro-arc oxidation treatment. Therefore, the preparation and processing method of the magnesium alloy implant device provided in this application is simple and easy to operate, does not involve toxic and harmful substances, and is environmentally friendly and green.

[0042] In summary, the magnesium alloy implant device of the present application greatly extends its service life by using hollow nails and guide pins processed from magnesium alloys with excellent performance to cooperate with each other. After the surface of the hollow nail is micro-arc oxidized, it is implanted in the body in combination with the guide pin to obtain excellent mechanical support, biocompatibility and a longer degradation cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a physical picture of magnesium alloy rod;

[0044] Figure 2This is a physical diagram of an embodiment of a magnesium alloy hollow nail;

[0045] Figure 3 This is a schematic diagram of the structure of a magnesium alloy implant device;

[0046] Figure 4 This is the surface state of the alloy after corrosion;

[0047] Figure 5 The experimental results of the effect of voltage on coating;

[0048] Figure 6 To provide experimental results for evaluating the degradation rate of surface coatings on different materials;

[0049] Figure 7 The microstructure of the magnesium alloy hollow extruded bar of Example 4;

[0050] Figure 8 This is the surface EDS qualitative result of Mg2Ca1Zn;

[0051] Figure 9 is the area ratio of the second phase in Mg2Ca1Zn alloy;

[0052] Figure 10 The open circuit potential and corrosion current density of the alloy of Example 4 are measured;

[0053] Figure 11 Schematic diagram of hydrogen evolution device;

[0054] Figure 12 This is the H2 release curve of magnesium alloy degradation in vitro;

[0055] Figure 13 The SEM electron microscope images of the through holes of the magnesium alloy hollow nails with and without coating;

[0056] Figure 14 This is a SEM electron microscope image of the outer surface of the ceramic coating of the magnesium alloy hollow nail. DETAILED DESCRIPTION

[0057] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present invention. In the present invention, unless otherwise specified, the equipment and raw materials used can be purchased from the market or are commonly used in this field. The methods in the following embodiments, unless otherwise specified, are conventional methods in this field.

[0058] Example 1

[0059] 1. If Figure 3 As shown, this embodiment provides a magnesium alloy implant device, which consists of a magnesium alloy hollow nail 1 and a magnesium alloy guide needle 2 that penetrates the inner cavity of the magnesium alloy hollow nail. The magnesium alloy hollow nail includes a hollow nail body 11 and a layer of inorganic ceramic coating 12 coated on the inner and outer surfaces of the hollow nail body. The self-corrosion potential of the magnesium alloy hollow nail is higher than the self-corrosion potential of the magnesium alloy guide needle.

[0060] The magnesium alloy hollow nail body material includes the following components in mass percentage: 1.0-6.0% Ca, 0.8-1.2% Zn, the total impurity content is less than 0.1%, and the remainder is Mg; the magnesium alloy guide pin is made of the same material as the magnesium alloy hollow nail body.

[0061] The inorganic ceramic coating is a micro-arc oxidation coating, which comprises the following components in mass percentage: Mg 20-40%, O 20-40%, P 8-20%, Ca 3-6%, and F 15-25%.

[0062] 2. This application also provides a method for preparing the above-mentioned magnesium alloy implant device, which comprises the following steps:

[0063] S1. Preparation of magnesium alloy bars:

[0064] S11. Under the protection of a mixed protective gas (99% CO2 + 1% SF6) atmosphere, melt pure magnesium at 760°C and keep warm for 30 to 60 minutes; add high-purity zinc and pure calcium, stir mechanically for 3 to 5 minutes, and keep warm for 20 to 30 minutes; cool to 720°C and cast into ingots.

[0065] S12, under the conditions of an extrusion ratio of 20 to 80, an extrusion temperature of 250 to 400°C, and an extrusion shaft speed of 0.1 to 1.0 mm / s, the above-mentioned ingot is processed by a low-temperature extrusion molding process to obtain a magnesium alloy rod (such as Figure 1 ).

[0066] S2, through longitudinal cutting CNC lathe processing, obtain magnesium alloy hollow nails and magnesium alloy guide pins (such as Figure 2 the upper part of the ).

[0067] S3. Processing of magnesium alloy hollow nails:

[0068] A magnesium alloy hollow nail is obtained by processing a layer of inorganic ceramic coating on the surface of the hollow nail body. The processing method of the inorganic ceramic coating is as follows:

[0069] S31. Weigh nano-hydroxyapatite, ethylene glycol, and triethanolamine according to a certain ratio and add them to water to prepare 1 L of solution A, which is then placed in an ultrasonic generator for ultrasonic-assisted aging for 40-60 minutes.

[0070] The particle size of the nano-hydroxyapatite is less than 100 nanometers. In 1L of solution A, the amount of nano-hydroxyapatite used is 3-5g, the amount of ethylene glycol used is 15-25ml, and the amount of triethanolamine used is 25-35ml.

[0071] S32. Weigh sodium hexametaphosphate and potassium fluoride dihydrate and add them to water to prepare 1 L of solution B.

[0072] The mass of sodium hexametaphosphate is 4-8 g, and the mass of potassium fluoride dihydrate is 14-18 g.

[0073] S33. Slowly add solution A to solution B and stir evenly to obtain solution C.

[0074] S34. Place the cleaned magnesium alloy hollow nail body in solution C as the anode and stainless steel as the cathode for micro-arc oxidation treatment.

[0075] The micro-arc oxidation treatment conditions are: a forward voltage of 340-420V, a positive duty cycle of 5-15%, a power frequency of 800-1200Hz, a negative voltage of 0-30V, a negative duty cycle of 20-80%, a positive-to-negative pulse ratio of 5-10:1, and a treatment time of 10-20min.

[0076] S35, the magnesium alloy hollow nail obtained in the previous step is rinsed with water and ethanol in turn and dried, and finally a magnesium alloy hollow nail with a surface bioceramic coating is obtained (such as Figure 2 Down).

[0077] The following three groups of magnesium alloy hollow nails (with coating) were prepared according to the above method and the conditions in Table 1 below. The specific formula and processing conditions are shown in Table 1 below.

[0078] Table 1 Preparation conditions of three groups of magnesium alloy hollow nails

[0079]

[0080]

[0081] 2. Testing of experimental effects

[0082] The magnesium alloy hollow nails of the experimental groups 1 to 3 of this embodiment were subjected to in vitro simulated degradation experiments and measurements of open circuit potential and corrosion current density; the testing methods were the same as those in Example 2.

[0083] The experimental results are shown in Table 2. As can be seen from the results in Table 2, the open-circuit potential values of the magnesium alloy hollow nails in Experimental Groups 1-3 were relatively close to zero, indicating excellent corrosion resistance. The potential difference between the open-circuit potential of the coated hollow nails and the uncoated magnesium alloy material (equivalent to the magnesium alloy guide pin) facilitated the interaction between the magnesium alloy hollow nails and the magnesium alloy guide pin.

[0084] Table 2 Open circuit potential and current density of three groups of magnesium alloy hollow nails (with coating)

[0085]

[0086]

[0087] Example 2 Optimization experiment of magnesium alloy hollow nail body material

[0088] 1. Experimental methods:

[0089] (1) Preparation of magnesium alloy hollow nail body material (or magnesium alloy guide pin):

[0090] This embodiment sets up experimental groups 4 to 7. The formula of the magnesium alloy hollow nail body material of each experimental group is shown in Table 3. The preparation method and conditions refer to Example 1.

[0091] Table 3 Material formula of magnesium alloy hollow nail body in each experimental group

[0092]

[0093] (2) The magnesium alloy hollow nail body materials of experimental groups 4-7 were tested for mechanical properties (tensile strength, ductility) and electrochemical properties (open circuit potential). The test method was as follows: refer to GB / T 228.1 Tensile tests on metallic materials Part 1: Room temperature test methods YY / T1552-2017 Surgical implants - open circuit potential measurement method for evaluating the long-term corrosion behavior of metallic implant materials and medical devices; the element content of magnesium alloy was analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0094] (3) In order to evaluate the corrosion performance of the above materials themselves, in vitro degradation weight loss experiments were conducted on the magnesium alloy hollow nail body samples of experimental groups 4 and 6. According to the ASTM G1-03 standard, the corrosion rate was calculated according to the following formula:

[0095] Corrosion rate = (K×W) / (A×T×D)

[0096] Where K = 8.76 × 10 4 , W is weight loss (g), A is sample surface area (cm 2 ), T is the immersion time (h), D is the sample density (g / cm3 ).

[0097] 2. Experimental results and analysis

[0098] (1) From the results in Table 4, it can be seen that changing the Ca content of the alloy has no significant effect on the tensile strength of the material, but has a significant effect on the elongation. The elongation of materials suitable for clinical fixation screws is generally not less than 10%. Therefore, Mg-2Ca-1Zn and Mg-4Ca-1Zn can both meet the requirements, and Mg-2Ca-1Zn is more ideal as a fixation screw processing material.

[0099] Analysis of the corrosion resistance of the material itself shows that with the increase of the Ca ratio, the open circuit potential of the alloy gradually decreases, indicating that its corrosion resistance weakens. From an electrochemical point of view, it is also proved that Mg-2Ca-1Zn and Mg-4Ca-1Zn both have good corrosion resistance potential.

[0100] Table 4 Mechanical and electrochemical properties of magnesium alloy materials

[0101] Alloy composition Tensile strength / Mpa Elongation % Open circuit potential / V Experimental Group 4 301.1 15.93 -1.51 Experimental Group 5 326.0 5.33 -1.62 Experimental Group 6 304.4 9.53 -0.44 Experimental Group 7 303.4 5.31 -1.77

[0102] (2) The results in Table 5 show that the proportions of various alloying elements are within the control range. The main impurities in the alloy are Al and Fe. Other impurities are all <0.0001 (not shown in the table). The total impurity content is controlled within the range of <0.1%. Based on the above material physical properties analysis, it can be concluded that the materials of Experimental Group 4 (Mg-2Ca-1Zn) and Experimental Group 6 (Mg-4Ca-1Zn) are ideal magnesium alloy implant materials.

[0103] Table 5 Analysis of element content in magnesium alloy

[0104]

[0105]

[0106] (3) The results of the 130-day weight loss test on the uncoated magnesium alloy hollow nail body (or magnesium alloy guide pin) are shown in Table 6. The corrosion appearance is as follows: Figure 4 shown.

[0107] The results of preliminary material degradation tests show that the corrosion rates of Mg4CaZn and Mg2CaZn are slow, among which the corrosion rate of Mg4CaZn is slower, which corresponds to the open circuit potential of the material.

[0108] Based on all the above experimental results, it can be seen that the magnesium alloy hollow nail bodies of experimental group 4 (Mg2CaZn) and experimental group 6 (Mg4CaZn) have better corrosion resistance, and among them, Mg-2Ca-1Zn has a higher elongation. Therefore, the subsequent examples use the magnesium alloy hollow nail body of Mg-2Ca-1Zn as the object for further experiments.

[0109] Table 6 Weight loss test results of untreated alloy

[0110]

[0111] Example 3 Optimization of Inorganic Ceramic Coating

[0112] The magnesium alloy hollow nail body prepared in experimental group 4 (Mg-2Ca-1Zn) of Example 2 was used as the object for bioceramic coating processing to prepare the magnesium alloy hollow nail, optimize the applied voltage parameters of micro-arc oxidation, and explore the effects of voltage, frequency, and duty cycle on the coating thickness, roughness, and calcium content of the coating.

[0113] 1. Effect of voltage on coating

[0114] (1) Experimental and testing methods

[0115] The bioceramic coating processing method of this embodiment was similar to the steps of Experimental Group 1 of Example 1. The forward voltage of the micro-arc oxidation treatment was set as a variable, and the effect of the change in forward voltage on the coating thickness, calcium content, and surface roughness of the magnesium alloy hollow nail was analyzed.

[0116] (2) Experimental results and analysis

[0117] The test results are as follows Figure 5 As shown in the figure, with the increase of voltage, the thickness and calcium content of the bioceramic coating of the magnesium alloy hollow nail gradually increase, and the surface roughness of the magnesium alloy hollow nail is better at around 380V. Therefore, a forward voltage of 380~420V was used for the subsequent micro-arc oxidation condition optimization experiment.

[0118] 2. Parameter test of micro-arc oxidation treatment

[0119] (1) Experimental methods:

[0120] According to the aforementioned preliminary experiments, the range of process parameters for surface coating research was confirmed. The specific research parameters are shown in Table 7. According to the parameter settings, micro-arc oxidation experiments were carried out on three magnesium alloy materials with different elemental compositions (refer to Example 1 for the specific operation method). These three magnesium alloy materials are Mg2CaZn alloy, EZ30 magnesium alloy, and WE43 magnesium alloy.

[0121] Table 7 Micro-arc oxidation parameter settings

[0122]

[0123] (2) Test method:

[0124] A. Material surface coating parameter degradation rate test method and evaluation method:

[0125] The samples (φ16mm*3mm) prepared for micro-arc oxidation parameter exploration were immersed in 3.5% NaCl solution and taken out after 180 days. The surface degradation products were washed away with clean water, and the coating corrosion was evaluated after drying.

[0126] B. In vitro degradation weight loss test: Referring to the method of Example 2, the Mg2CaZn alloy and Mg4CaZn alloy materials processed with inorganic ceramic coating were tested after 120 days of treatment.

[0127] (3) Experimental results and analysis

[0128] ①Based on Figure 6 The corrosion results of the coatings of various materials were evaluated and it was found that the optimal parameters of the micro-arc oxidation process were set as: voltage 400V, frequency 1000Hz, duty cycle 10%, and processing time 10min; and the coating of the Mg2CaZn alloy of the present application had the best corrosion resistance.

[0129] ② Comprehensive analysis of the 120-day in vitro degradation weight loss test results in Table 8 shows that the magnesium alloy hollow nail body material (Mg2CaZn) of the experimental group 1) in Example 1 has a lower degradation corrosion rate after surface coating treatment and is more corrosion-resistant.

[0130] Table 8 Weight loss test results of magnesium alloy hollow nails after adding coating

[0131]

[0132] Example 4 Analysis of the influence of alloy material structure on performance

[0133] (1) Experimental methods

[0134] A. Scanning electron microscopy was performed on the magnesium alloy hollow nail body of Experimental Group 1 of Example 1 and the magnesium alloy hollow nail before and after adding the ceramic coating, and elemental analysis and second phase analysis in the alloy were performed;

[0135] B. Two groups of magnesium alloy hollow nails, 2CaZn and 4CaZn, were used as the objects for the measurement of open circuit potential and corrosion current density, respectively: using an electrochemical workstation, the electrolyte was 0.9% sodium chloride solution, the reference electrode was a saturated silver chloride electrode, the switch was switched to the open circuit potential position, the operating parameters were set for measurement, and the switch was switched to the polarization curve position, the operating parameters were set, and the measurement was carried out.

[0136] The material composition of 2CaZn is: 2% Ca, 1% Zn, the total impurities are less than 0.1%, and the balance is Mg. The material composition of 4CaZn is: 4% Ca, 1% Zn, the total impurities are less than 0.1%, and the balance is Mg.

[0137] (2) Experimental results

[0138] A. Figure 7 and Figure 9 As shown, the Mg-2Ca-1Zn magnesium alloy hollow nail (or magnesium alloy rod) exhibits a typical dynamically recrystallized structure with fine equiaxed grains. The average grain size measured by the intercept method is 2.8±0.3μm. The grains are uniform and small, demonstrating a uniform material quality. Small grains improve corrosion resistance. The ratio of Ca and Zn elements in the structure is essentially consistent with the designed material composition, and no obvious inclusions or defects are observed.

[0139] Figure 13 These are the SEM electron microscopy characterization results of the through-holes of the magnesium alloy hollow nails with and without coating. From the comparison of the figures, it can be seen that after the coating process, a uniform ceramic coating is produced on the inner surface of the through-hole of the magnesium alloy hollow nail with a thickness of about 5-10um, and the coating surface has an uneven structure.

[0140] Figure 14 This is an SEM electron microscope image of the outer surface of the ceramic coating of a magnesium alloy hollow nail. From the image, we can see that the micro-arc oxidation layer on the nail surface is uniform and smooth, and can completely cover the surface of the magnesium alloy nail. At the same time, there are evenly distributed blind holes on the surface of the layer with a diameter of about 1-5um.

[0141] B. Figure 10 As shown in the results of Tables 9 and 10, after the magnesium alloy material of the present application is added with the inorganic ceramic coating (i.e., MAO treatment), the open circuit potential is significantly reduced to -0.115 V, and the corrosion current density is reduced to 3.16×10 -6 A / cm 2 The experimental results show that after adding the inorganic ceramic coating to the surface of the magnesium alloy hollow nail body (also the aforementioned magnesium alloy rod), its corrosion tendency is reduced to 1 / 6 of the original, and the corrosion resistance is greatly improved.

[0142] Table 9 Open circuit potential and current density of untreated magnesium alloy hollow nail body

[0143]

[0144] Table 10 Open circuit potential and current density of the magnesium alloy hollow nail body after adding inorganic ceramic coating

[0145]

[0146] Example 5 Performance comparison of different usage modes of the magnesium alloy implant device of the present invention

[0147] 1. Experimental methods

[0148] The following experimental group 8 and comparative examples 1 and 2 were set up respectively, and the devices of experimental group 8, comparative examples 1 and 2 were used as objects for in vitro simulated degradation experiments. The in vitro simulated magnesium alloy degradation experimental device (i.e., the schematic diagram of the hydrogen evolution experimental device) is as follows: Figure 11 As shown in FIG, this method measures the volume of hydrogen generated by the water displacement method to obtain the degradation rate of the magnesium alloy.

[0149] (1) The experimental groups were specifically set up as follows:

[0150] Experimental Group 8: A magnesium alloy implant device (an assembly of a magnesium alloy hollow body and a magnesium alloy guide pin) prepared according to the method of Experimental Group 1 in Example 1;

[0151] Comparative Example 1: The difference from Experimental Group 8 is that only magnesium alloy hollow nails (with coating) are provided without built-in magnesium alloy guide pins;

[0152] Comparative Example 2: The difference from Experimental Group 8 is that only a magnesium alloy hollow nail body is provided, without an inorganic ceramic coating and a built-in magnesium alloy guide pin.

[0153] Comparative Example 3: The existing magnesium alloy WE43 was used.

[0154] (2) Specific experimental steps and conditions: The magnesium alloy instruments of each group were immersed in PBS buffer solution. The specific device was as follows: Figure 11 After installation, record the hydrogen drainage volume and indoor temperature every day, and replace the degradation simulation liquid once a week.

[0155] 2. Experimental results and analysis

[0156] According to the above method, the samples of each test group were degraded in PBS buffer in vitro for 2 months. The cumulative volume curve of hydrogen released by magnesium alloy in each group is shown in Figure 2. Figure 12 As shown in the figure, during the first week of simulated degradation, the hydrogen release rates of the magnesium alloy implants in the three test groups were similar, and then showed differentiation:

[0157] ① Comparative Example 2 without coating and guide needle: Obvious pitting points are formed on the surface of the hollow nail body, and the volume of hydrogen release increases rapidly. After 30 days of degradation, the nail loses its mechanical support and breaks at the corrosion point.

[0158] ② Comparative Example 1 of Coated Hollow Nails: The hydrogen release rate of this group of magnesium alloy hollow nails is relatively stable, and the release curve is linear. It tends to be uniformly corroded within 30 days of degradation. After 30 days, pitting points appear. After 60 days of degradation, the nail loses mechanical support and breaks.

[0159] ③ Comparative Example 3: Magnesium alloy WE4 was crushed and degraded within one week.

[0160] ④ Experimental Group 8 with coating and guide pin: The hydrogen release rate was slow, uniform and stable. After 60 days of continuous degradation, corrosion was found at both ends of the nail, but no pitting was found in the middle section, which showed that the mechanical support function could be maintained. Based on the initial hydrogen release rate, the complete degradation period of the magnesium alloy device in this group was estimated to be 2 years.

[0161] Based on the above experimental results, it can be seen that the magnesium alloy implant device provided in this application is precisely through the mutual cooperation of the magnesium alloy hollow nail with a self-corrosion potential difference and the magnesium alloy guide pin, so that the magnesium alloy hollow nail with a high open circuit potential is protected by sacrificing the magnesium alloy guide pin, and can provide longer-term mechanical support as the main bearing unit.

[0162] It is understandable that those skilled in the art can make equivalent substitutions or changes based on the technical solutions and concepts of the present invention, and all these changes or substitutions should fall within the scope of protection of the claims attached to the present invention.

Claims

1. A magnesium alloy implant device, characterized in that: The invention comprises a magnesium alloy hollow nail and a magnesium alloy guide pin disposed through the inner cavity of the magnesium alloy hollow nail. The magnesium alloy hollow nail comprises a magnesium alloy hollow nail body and a layer of inorganic ceramic coating covering the inner and outer surfaces of the magnesium alloy hollow nail body. A through hole for the magnesium alloy guide pin to pass through is disposed through the hollow nail body along the central axis. The inner diameter of the through hole matches that of the magnesium alloy guide pin. Both ends of the magnesium alloy guide pin are exposed outside the through hole. The self-corrosion potential of the magnesium alloy hollow nail is higher than that of the magnesium alloy guide pin. The magnesium alloy hollow nail body material includes the following components in mass percentage: 1.0-6.0% Ca, 0.8-1.2% Zn, the total impurity content is less than 0.1%, and the remainder is Mg; the magnesium alloy guide pin is made of the same material as the magnesium alloy hollow nail body; The inorganic ceramic coating is a micro-arc oxidation coating, which includes the following components in mass percentage: Mg 20-40%, O 20-40%, P 8-20%, Ca 3-6%, and F 15-25%.

2. The magnesium alloy implant device according to claim 1, characterized in that: One end of the hollow nail body is arranged as a head, the outer end surface of the head is provided with a fixing groove, and the outer wall of the hollow nail body is provided with threaded parts along the length direction.

3. A method for preparing a magnesium alloy implant device according to claim 1, characterized in that: The following steps are involved: S1. Preparing a magnesium alloy rod, the magnesium alloy rod comprising the following components in mass percentages: 1.0-6.0% Ca, 0.8-1.2% Zn, a total impurity content of less than 0.1%, and the remainder being Mg; S2. Processing the magnesium alloy rod into magnesium alloy hollow nail bodies and magnesium alloy guide pins of different structures using a lathe; S3, processing a layer of inorganic ceramic coating on the surface of the magnesium alloy hollow nail body to obtain a magnesium alloy hollow nail; In step S3, the processing method of the inorganic ceramic coating on the surface of the hollow nail body is: S31. Weigh corresponding amounts of nano-hydroxyapatite, ethylene glycol, and triethanolamine, respectively, and add them to water to prepare 1 L of solution A, which is then placed in an ultrasonic generator for ultrasound-assisted aging for 40-60 min. S32. Weigh sodium hexametaphosphate and potassium fluoride dihydrate and add them to water to prepare 1 L of solution B; S33, slowly adding solution A to solution B and stirring evenly to obtain solution C; S34, placing the cleaned magnesium alloy hollow nail body in solution C as an anode and stainless steel as a cathode to perform micro-arc oxidation treatment; S35. Rinse the magnesium alloy hollow nail obtained in the previous step with water and ethanol in turn and dry it.

4. The method for preparing a magnesium alloy implant device according to claim 3, characterized in that: In step S1, the preparation method of the magnesium alloy rod is as follows: S11. Under the protection of a mixed protective gas atmosphere, melt pure magnesium at 750-800°C and keep warm for 30-60 minutes; add high-purity zinc and pure calcium in corresponding mass percentages, mechanically stir for 3-5 minutes, and keep warm for 20-30 minutes; cool to 700-730°C and cast into an ingot; S12. Under the conditions of an extrusion ratio of 20 to 80, an extrusion temperature of 250 to 400° C., and an extrusion shaft speed of 0.1 to 1.0 mm / s, a low-temperature extrusion forming process is performed to obtain a magnesium alloy rod.

5. The method for preparing a magnesium alloy implant device according to claim 3, characterized in that: In step S31, the particle size of the nano-hydroxyapatite is less than 100 nanometers; the mass volume ratio of the nano-hydroxyapatite, ethylene glycol, and triethanolamine is: 3-5 g: 15-25 ml: 25-35 ml.

6. The method for preparing a magnesium alloy implant device according to claim 3, characterized in that: In step S32, the mass ratio of sodium hexametaphosphate to potassium fluoride dihydrate is: 4-8 g: 14-18 g.

7. The method for preparing a magnesium alloy implant device according to claim 3, characterized in that: The micro-arc oxidation treatment conditions are: a forward voltage of 340-420V, a positive duty cycle of 5-15%, a power frequency of 800-1200Hz, a negative voltage of 50-80V, a negative duty cycle of 5-10%, a positive-to-negative pulse ratio of 5-10:1, and a treatment time of 10-20min.

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