A magnesium alloy hollow nail, a magnesium alloy guide pin, their preparation method and applications

Abstract

This invention discloses a magnesium alloy hollow nail, a magnesium alloy guide pin, their preparation method, and applications. The magnesium alloy hollow nail consists of a magnesium alloy hollow nail body and an inorganic ceramic coating covering the surface of the magnesium alloy hollow nail body. A through hole for a magnesium alloy guide pin to pass through is provided along the central axis of the magnesium alloy hollow nail body. The inorganic ceramic coating is also uniformly distributed on all inner surfaces of the through hole. Threaded portions are distributed along the length of the outer wall of the magnesium alloy hollow nail body. The self-corrosion potential of the inorganic ceramic coating is higher than that of the magnesium alloy hollow nail body. The magnesium alloy guide pin is used in conjunction with the aforementioned magnesium alloy hollow nail. It has a rod-like structure, and the outer diameter of the magnesium alloy guide pin matches the inner diameter of the through hole of the magnesium alloy hollow nail. This magnesium alloy hollow nail, in conjunction with the magnesium alloy guide pin, significantly improves the corrosion resistance of the magnesium alloy hollow nail, extends its service life, and exhibits good biocompatibility and a longer degradation cycle.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, and in particular to a magnesium alloy hollow nail, its preparation method and its application. Background Technology

[0002] Currently, various alloy bone screws are widely used in orthopedic clinical surgery. Bone screws are typically used for the fixation of internal fractures or dislocations. They achieve fracture fixation, bone positioning, and promote healing by directly screwing in two different bone fragments or fixing plates. Based on different structural characteristics, bone screws can be classified as ordinary screws, locking screws, headless screws (also known as Hubble screws), and hollow screws. Based on the manufacturing material, bone screws can be classified as titanium screws, stainless steel screws, and bioresorbable screws. Against the backdrop of my country's aging population, the number of fracture patients is rising, increasing the market demand for bone screws and placing higher demands on the performance of alloy orthopedic implants, such as better corrosion resistance, longer service life, and better biodegradability in vivo.

[0003] Compared to traditional orthopedic implants made of stainless steel, cobalt-based alloys, and titanium alloys, magnesium alloy implants offer several advantages: Firstly, magnesium alloy screws can degrade and be absorbed after the damaged bone tissue has repaired, eliminating the need for a second surgery and reducing patient pain and treatment costs. Secondly, the density and elastic modulus of magnesium alloys are closer to those of human bone tissue, reducing stress shielding effects and promoting bone healing. Therefore, magnesium alloy orthopedic implants have experienced rapid development in recent years.

[0004] However, magnesium alloy implants generally suffer from a short service life, a characteristic inherent to the material itself. Magnesium and magnesium alloys degrade rapidly in bodily fluids, producing a high amount of hydrogen gas in the short term, which can easily lead to air pockets. This results in a short mechanical service life after implantation. Currently, the main approach to improving the service life of magnesium alloy implants is based on improvements to the bone screw material itself, thereby enhancing its corrosion resistance. However, because the synergistic effects between multiple components within the entire implant system are not considered, the risk of mechanical failure after magnesium alloy bone screw implantation remains, making it difficult to effectively extend the service life.

[0005] Furthermore, while current magnesium alloy surface treatment methods can slow down the degradation rate in the early stages of implantation and reduce the generation of hydrogen gas, the degradation mechanism is mainly pitting corrosion, resulting in a short mechanical support time for the screw in the body and a high probability of needing repair. For example, patent CN 108543118B discloses a magnesium alloy fixation screw with controllable in vivo degradation. The magnesium alloy screw body is a conventional solid screw structure, which has limited clinical application. The magnesium alloy screw body has an oxide film layer with a thickness of 50-200 μm, and a biodegradable polymer coating with a thickness of 1-50 μm is coated on the oxide film layer. Both coatings are not only relatively thick, but are also prone to peeling off during use, leading to localized corrosion, and cannot achieve a significant improvement in service life. Patent CN109295365B discloses a biodegradable magnesium alloy molding blank. This patent solution only addresses the problem of poor mechanical properties of magnesium alloy materials during molding, but it cannot solve the problems of rapid, uneven, and uncontrolled degradation rate of magnesium alloys, making it difficult to significantly extend the service life.

[0006] It is evident that current magnesium alloy bone screw implantation devices, while improving the material properties of the bone screws themselves to address issues such as excessively rapid and uneven degradation and short service life, have limited the ability to achieve significant improvements in technical effectiveness.

[0007] Therefore, existing technologies need further improvement. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a novel magnesium alloy hollow nail. This magnesium alloy hollow nail, in conjunction with a magnesium alloy guide needle penetrating through it, protects the high open-circuit potential of the magnesium alloy hollow nail by sacrificing the magnesium alloy guide needle. This allows the hollow nail, as the main load-bearing unit of the implantable device, to provide longer-lasting mechanical support and effectively extend its service life.

[0009] To address the above problems, this application provides the following technical solution:

[0010] In a first aspect, this application provides a magnesium alloy hollow nail, which consists of a magnesium alloy hollow nail body and an inorganic ceramic coating covering the surface of the magnesium alloy hollow nail body; the magnesium alloy hollow nail body has a through hole along its central axis for a magnesium alloy guide needle to pass through, and the inorganic ceramic coating is also uniformly distributed on all inner surfaces of the through hole; the outer wall of the magnesium alloy hollow nail body has threaded portions distributed along its length; the self-corrosion potential of the inorganic ceramic coating is higher than the self-corrosion potential of the magnesium alloy hollow nail body.

[0011] Although existing hollow nails also have inner holes, the function of these inner holes or cavities is to inject drugs and release them sustainably, as in the patent with publication number CN111282025B.

[0012] In this application, the through-hole within the hollow magnesium alloy nail is for installing a magnesium alloy guide pin. By adding an inorganic ceramic coating to the surface of the hollow magnesium alloy nail, the self-corrosion potential of the hollow magnesium alloy nail is increased to be higher than that of a magnesium alloy guide pin of the same material. This allows the magnesium alloy guide pin to act as a sacrificial anode, forming a relative electrochemical corrosion protection. This protects the hollow magnesium alloy nail with its high open-circuit potential, enabling it to provide longer-lasting mechanical support as the main load-bearing unit and significantly extending the service life of the entire implantable device. Therefore, the corrosion resistance principle of the hollow magnesium alloy nail in this application differs from existing technologies.

[0013] To facilitate the proper insertion of the magnesium alloy hollow nail into the target location, the outer wall of the magnesium alloy hollow nail body is provided with threaded portions along its length. The structure and distribution of the threaded portions are not limited to the specific embodiments and drawings.

[0014] Optionally, in the magnesium alloy hollow nail, the threaded portion includes a first threaded portion I and a second threaded portion II distributed on the outer surface of the magnesium alloy body. The two threaded portions are arranged adjacent to each other or spaced apart. The threads of the two threaded portions can be configured differently.

[0015] Optionally, in order to facilitate the installation of the hollow magnesium alloy nail, a locking groove is provided on the outer end face of the head, the locking groove is connected to the through hole, and the cross-section of the locking groove is non-circular.

[0016] Optionally, in the magnesium alloy hollow nail, the body material of the magnesium alloy hollow nail comprises the following components by mass percentage: 1.0-6.0% Ca, 0.8-1.2% Zn, less than 0.1% total impurities, and the remainder being Mg. The magnesium alloy hollow nail body prepared under these conditions exhibits good corrosion resistance.

[0017] Preferably, the magnesium alloy hollow nail body material comprises the following components in the following mass percentages: 2% / 4% Ca, 1% Zn, total impurities less than 0.1%, and the remainder being Mg.

[0018] Preferably, the method for preparing the magnesium alloy hollow nail body is as follows:

[0019] (1) Under the protection of a mixed protective gas atmosphere, melt pure magnesium at 750-800℃ and hold for 30-60 minutes; add high-purity zinc and pure calcium of the corresponding mass percentage, stir mechanically for 3-5 minutes, hold for 20-30 minutes; cool down to 700-730℃ and pour into ingots.

[0020] (2) Under the conditions of extrusion ratio of 20 to 80, extrusion temperature of 250 to 400°C and extrusion shaft speed of 0.1 to 1.0 mm / s, a low-temperature extrusion molding process is carried out to obtain magnesium alloy rods; then the magnesium alloy rods are physically processed by a lathe to obtain a magnesium alloy hollow nail body with the aforementioned structural characteristics.

[0021] Optionally, in the magnesium alloy hollow nail, the inorganic ceramic coating is a micro-arc oxidation coating, which includes the following elements in mass percentage: Mg 20-40%, O 20-40%, P 8-20%, Ca 3-6%, F 15-25%.

[0022] Secondly, this application also provides a magnesium alloy guide pin for use in conjunction with the aforementioned magnesium alloy hollow nail. The magnesium alloy guide pin has a rod-like structure, and its outer diameter is slightly smaller than the inner diameter of the through-hole in the magnesium alloy hollow nail. The length of the magnesium alloy guide pin is greater than that of the magnesium alloy hollow nail, so that both ends of the magnesium alloy guide pin are exposed in the assembled state for easy operation.

[0023] The magnesium alloy guide needle is made of the same material as the magnesium alloy hollow nail body. This greatly simplifies the material selection for this magnesium alloy implantation device (the assembly of the magnesium alloy hollow nail and guide needle), reducing its processing technology and production costs.

[0024] Preferably, the magnesium alloy guide needle is made of the following components in the indicated mass percentages: 1.0-6.0% Ca, 0.8-1.2% Zn, less than 0.1% total impurities, and the remainder being Mg.

[0025] Thirdly, this application also provides a method for preparing the above-mentioned magnesium alloy guide needle, which includes the following steps: first, preparing a magnesium alloy rod, and then machining the magnesium alloy rod into a magnesium alloy guide needle by a lathe; wherein, the magnesium alloy rod includes the following components in the following mass percentages: 1.0-6.0% Ca, 0.8-1.2% Zn, less than 0.1% total impurities, and the remainder being Mg.

[0026] Fourthly, this application also provides a method for preparing the above-mentioned magnesium alloy hollow nail, which includes the following steps:

[0027] S1. Prepare magnesium alloy rods and process them into magnesium alloy hollow nail bodies using a lathe.

[0028] The magnesium alloy rods contain the following components by mass percentage: 1.0-6.0% Ca, 0.8-1.2% Zn, less than 0.1% total impurities, and the remainder being Mg.

[0029] S2. A layer of inorganic ceramic coating is processed on the surface of the magnesium alloy hollow nail body to obtain a magnesium alloy hollow nail.

[0030] Preferably, in the method for preparing the magnesium alloy hollow nail, the method for preparing the magnesium alloy rod is as follows:

[0031] S11. Under the protection of a mixed protective gas atmosphere, melt pure magnesium at 750-800℃ and hold for 30-60 minutes; add high-purity zinc and pure calcium of the corresponding mass percentage, stir mechanically for 3-5 minutes, hold for 20-30 minutes; cool to 700-730℃ and pour into ingots.

[0032] 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 molding process is carried out to obtain magnesium alloy rods.

[0033] Preferably, the processing method for the inorganic ceramic coating includes the following steps:

[0034] S21. Weigh out the corresponding amounts of nano-hydroxyapatite, ethylene glycol, and triethanolamine respectively and add them to water to prepare solution A. Place the solution in an ultrasonic generator for ultrasonic-assisted maturation for 40-60 minutes.

[0035] S22. Weigh out sodium hexametaphosphate and potassium fluoride dihydrate and add them to water to prepare solution B.

[0036] S23. Slowly add an equal volume of solution A to solution B and stir until homogeneous to obtain solution C;

[0037] S24. 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.

[0038] S25. Rinse the magnesium alloy hollow nails obtained in the previous step with water and ethanol and dry them.

[0039] Optionally, in step S21, in solution A, the mass concentration of nano-hydroxyapatite is 3-5 g / L, the volume concentration of ethylene glycol is 15-25 ml / L, and the volume concentration of triethanolamine is 25-35 ml / L.

[0040] Optionally, in step S22, the mass-volume concentration of sodium hexametaphosphate in solution B is 4-8 g / L, and the mass-volume concentration of potassium fluoride dihydrate is 14-18 g / L.

[0041] Preferably, the conditions for the micro-arc oxidation treatment are: a positive voltage of 340-420V, a positive duty cycle of 5-15%, a power supply 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.

[0042] More preferably, the conditions for the micro-arc oxidation treatment are as follows: the micro-arc oxidation process parameters are set to 400V, frequency 1000Hz, duty cycle 10%, and treatment time 10min.

[0043] Fifthly, this application provides a method for using the aforementioned magnesium alloy hollow nail. The method involves assembling the magnesium alloy hollow nail together with a magnesium alloy guide pin that penetrates its through-hole. The magnesium alloy guide pin has both ends exposed outside the nail body, and the material of the magnesium alloy guide pin is the same as that of the magnesium alloy hollow nail body.

[0044] Optionally, the specific usage method of the above-mentioned magnesium alloy hollow nail and matching magnesium alloy guide pin is as follows:

[0045] During the procedure, a hole is first drilled at the fracture site (or surgical site). A stainless steel guide pin is then screwed into the hole for initial positioning. The magnesium alloy hollow screw of this invention is then installed along the stainless steel guide pin. Next, the stainless steel guide pin is unscrewed and replaced with the magnesium alloy guide pin, which is then installed onto the through-hole magnesium alloy hollow screw, completing the fixation of the fracture site by the magnesium alloy implant. Using a stainless steel guide pin with higher mechanical strength for initial positioning avoids damage to the magnesium alloy guide pin. In other applications, the magnesium alloy guide pin can be implanted first, followed by the magnesium alloy hollow screw. The application method in cruciate ligament reconstruction surgery is similar and will not be elaborated further.

[0046] The present invention has the following beneficial effects:

[0047] 1. This invention provides a magnesium alloy hollow nail made of a specific material. The magnesium alloy hollow nail has a through hole along its axis for installing a magnesium alloy guide needle. An inorganic ceramic coating is wrapped around the surface of the magnesium alloy hollow nail body material, so that the self-corrosion potential of the inorganic ceramic coating is higher than that of the magnesium alloy hollow nail body. This causes the implanted magnesium alloy hollow nail and guide needle to undergo galvanic corrosion after surgical implantation at the lesion site.

[0048] The principle of corrosion protection for the magnesium alloy hollow nail body is as follows: due to its low self-corrosion potential, the magnesium alloy guide needle acts as a sacrificial anode, forming a relative electrochemical corrosion protection. The magnesium alloy guide needle is directionally corroded from both ends, which can solve the current problems of rapid degradation rate, uneven degradation and short service life of magnesium alloy. Through the above method, the magnesium alloy hollow nail with high open circuit potential is protected, and as the main load-bearing unit, it can provide longer mechanical support, greatly extending the service life of the entire implantation device.

[0049] 2. The inorganic ceramic coating covering the inner and outer surfaces of the magnesium alloy hollow nail serves two functions: First, the coating allows the magnesium alloy guide needle to act as a sacrificial anode, thus protecting the hollow nail itself. Second, the coating exhibits good corrosion resistance in the in vivo environment. After the sacrificial anode degrades and corrodes in the later stages of device implantation, the coating can independently establish a corrosion barrier for the magnesium alloy hollow nail, delaying its degradation and the decline in its mechanical integrity. Therefore, the aforementioned magnesium alloy hollow nail achieves dual protection through both sacrificial anode and coating technologies. These two technologies are compatible and mutually reinforcing, resulting in excellent mechanical support, a significantly extended device service life, good biocompatibility, and a longer degradation cycle.

[0050] 3. The raw materials of the magnesium alloy hollow nail contain only Mg, Ca, and Zn, with a total impurity content of less than 0.1%, and it also has good biocompatibility. The inorganic ceramic coating has good biocompatibility. Therefore, the magnesium alloy implant device is safe to use.

[0051] 4. The magnesium alloy hollow nail is made by physically processing magnesium alloy rods to obtain the body, and then completing the coating process through a one-step micro-arc oxidation treatment. The raw material composition is simple, the whole preparation process is simple and easy to operate, does not involve toxic or harmful substances, and is environmentally friendly and green. Attached Figure Description

[0052] Figure 1 This is a picture of a magnesium alloy rod.

[0053] Figure 2 A photograph of one embodiment of a magnesium alloy hollow nail;

[0054] Figure 3 A schematic diagram of a magnesium alloy implantable device;

[0055] Figure 4 This is a diagram showing the surface condition of the alloy after corrosion.

[0056] Figure 5 The experimental results show the effect of voltage on the coating.

[0057] Figure 6 The experimental results were used to evaluate the degradation rate of coatings on different material surfaces.

[0058] Figure 7 The microstructure of the air-extruded magnesium alloy bar in Example 4;

[0059] Figure 8 The surface EDS qualitative results of Mg2Ca1Zn;

[0060] Figure 9 The results show the area ratio of the second phase in the Mg2Ca1Zn alloy;

[0061] Figure 10 The results of the alloy open-circuit potential and corrosion current density measurements in Example 4 are as follows;

[0062] Figure 11 This is a schematic diagram of a hydrogen evolution device;

[0063] Figure 12 The H2 release curve of magnesium alloy in vitro degradation;

[0064] Figure 13 SEM images of the through holes in uncoated and coated magnesium alloy hollow nails.

[0065] Figure 14 This is a SEM image of the ceramic coating outer surface of a magnesium alloy hollow nail. Detailed Implementation

[0066] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort 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 the art. Unless otherwise specified, the methods in the following embodiments are conventional methods in the art.

[0067] Example 1: Preparation of magnesium alloy hollow nails and magnesium alloy guide pins

[0068] The magnesium alloy hollow nail of the present invention has the following three main improvements: first, structural improvement; second, material improvement of the magnesium alloy hollow nail body; and third, improvement of the inorganic ceramic coating attached to the magnesium alloy hollow nail body. Each part will be explained below:

[0069] 1. Structural design of magnesium alloy hollow nails

[0070] The embodiment provides a new type of hollow magnesium alloy nail. Figure 2 and Figure 3 A illustrates one embodiment of this magnesium alloy hollow nail, the structure of which is as follows, in order to cooperate with the structure of the magnesium alloy guide pin (whose material is the same as that of the magnesium alloy hollow nail body):

[0071] The magnesium alloy hollow nail consists of a magnesium alloy hollow nail body 11 and an inorganic ceramic coating 12 covering the surface of the magnesium alloy hollow nail body. The magnesium alloy hollow nail body has a through hole 13 along its central axis for a magnesium alloy guide needle to pass through. The inorganic ceramic coating is evenly distributed on the outer surface of the hollow nail body and all the inner surfaces of the through hole.

[0072] The outer wall of the magnesium alloy hollow nail body has threaded portions distributed along its length. In this embodiment, preferably, the threaded portions include a first threaded portion I and a second threaded portion II distributed on the outer surface of the magnesium alloy body, and the two threaded portions are arranged adjacent to each other. The structure and distribution of the threaded portions are not limited to the specific embodiments and drawings.

[0073] To facilitate the installation of the hollow nail, a set groove is provided on the outer end face of the head. The set groove communicates with the through hole, and its cross-section is non-circular, such as a star-shaped or hexagonal shape. During use, the hollow nail can be screwed into the target location by engaging the end of a tool (such as a screwdriver or wrench) with the set groove. The set groove can be any existing slot shape, not limited to the star-shaped slot of this embodiment.

[0074] More importantly, the self-corrosion potential of the inorganic ceramic coating is higher than that of the magnesium alloy hollow nail body. This protects the magnesium alloy hollow nail with a high open circuit potential by sacrificing the magnesium alloy conductor, allowing the magnesium alloy hollow nail to provide longer-lasting mechanical support as the main load-bearing unit.

[0075] The magnesium alloy hollow nail body material comprises the following components by mass percentage: 1.0-6.0% Ca, 0.8-1.2% Zn, less than 0.1% total impurities, and the remainder being Mg; the magnesium alloy guide needle is made of the same material as the magnesium alloy hollow nail body material.

[0076] The inorganic ceramic coating is a micro-arc oxidation coating, which includes the following components in the following mass percentages: Mg 20-40%, O 20-40%, P 8-20%, Ca 3-6%, F 15-25%.

[0077] 2. Preparation method of magnesium alloy hollow nails

[0078] This embodiment provides a method for preparing the magnesium alloy hollow nail, which includes the following steps:

[0079] S1. Prepare magnesium alloy rods and process them into magnesium alloy hollow nail bodies using a lathe.

[0080] S11. Under the protection of a mixed protective gas atmosphere (99% CO2 + 1% SF6), melt pure magnesium at 760℃ and hold for 30-60 minutes; add high-purity zinc and pure calcium, stir mechanically for 3-5 minutes, and hold for 20-30 minutes; cool to 720℃ and pour into an ingot.

[0081] S12. Under the conditions of an extrusion ratio of 20–80, an extrusion temperature of 250–400℃, and an extrusion shaft speed of 0.1–1.0 mm / s, the aforementioned ingot is processed into magnesium alloy rods (e.g., magnesium alloy rods) through a low-temperature extrusion forming process. Figure 1 ).

[0082] S13. Obtain the magnesium alloy hollow nail body (e.g., by longitudinal cutting CNC lathe machining) Figure 2 (As shown in the image above).

[0083] S2. A layer of inorganic ceramic coating is processed on the surface of the magnesium alloy hollow nail body to obtain a magnesium alloy hollow nail.

[0084] Specifically, the processing method for this inorganic ceramic coating is as follows:

[0085] S21. Weigh out nano-hydroxyapatite, ethylene glycol, and triethanolamine according to the proportions and add them to water to prepare 1L of solution A. Place the solution in an ultrasonic generator for ultrasonic-assisted maturation for 40-60 minutes.

[0086] The nano-hydroxyapatite has a particle size of less than 100 nanometers. In 1L of solution A, the amount of nano-hydroxyapatite is 3-5g, the amount of ethylene glycol is 15-25ml, and the amount of triethanolamine is 25-35ml.

[0087] S22. Weigh out sodium hexametaphosphate and potassium fluoride dihydrate and add them to water to prepare 1L of solution B.

[0088] The sodium hexametaphosphate contains 4-8g of sodium hexametaphosphate and the potassium fluoride dihydrate contains 14-18g of potassium fluoride dihydrate.

[0089] S23. Slowly add solution A to solution B and stir until homogeneous to obtain solution C.

[0090] S24. 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.

[0091] The conditions for the micro-arc oxidation treatment are as follows: positive voltage of 340-420V, positive duty cycle of 5-15%, power frequency of 800-1200Hz, negative voltage of 0-30V, negative duty cycle of 20-80%, positive-to-negative pulse ratio of 5-10:1, and treatment time of 10-20min.

[0092] S25. The magnesium alloy hollow nails obtained in the previous step are rinsed with water and ethanol in sequence and then dried to obtain magnesium alloy hollow nails with a bioceramic coating on the surface (e.g., Figure 2 Down).

[0093] Magnesium alloy hollow nails were prepared according to the above preparation method and the specific conditions required in Table 1 below. The specific formulas and processing conditions are shown in Table 1 below.

[0094] Table 1. Preparation conditions of three groups of magnesium alloy hollow nails

[0095]

[0096] 3. Preparation of magnesium alloy guide needles

[0097] Since the material of the magnesium alloy guide pin is the same as that of the magnesium alloy hollow nail body, its preparation method is the same as that of the magnesium alloy hollow nail body. The difference is that when the magnesium alloy rod is processed by a longitudinal CNC lathe, it is processed into magnesium alloy guide pin 2.

[0098] For the reasons stated above, the material properties of the magnesium alloy guide pin are the same as those of the magnesium alloy hollow nail body, and can be analyzed by referring to the experimental data of the magnesium alloy hollow nail later. Further details will not be provided hereafter.

[0099] 4. Performance testing of magnesium alloy hollow nails in experimental groups 1-3

[0100] (1) Detection method

[0101] The open circuit potential and corrosion current density of the magnesium alloy hollow nails in experimental groups 1 to 3 were determined. The test methods were based on GB / T 228.1 Metallic materials, tensile testing - Part 1: Room temperature test method and YY / T1552-2017 Surgical implants, evaluation of long-term corrosion behavior of metallic implant materials and medical devices, open circuit potential measurement method.

[0102] (2) Test results and analysis

[0103] The experimental results are shown in Table 2 below. The results show that the open-circuit potential values ​​of the magnesium alloy hollow nails in experimental groups 1-3 are close to zero, indicating good corrosion resistance. Increasing the open-circuit potential of the coated hollow nails creates a potential difference between them and the uncoated magnesium alloy material (equivalent to a magnesium alloy guide needle), facilitating the interaction and function of the magnesium alloy hollow nails and magnesium alloy guide needles.

[0104] Table 2. Alloy open-circuit potential and current density of three groups of magnesium alloy hollow nails (with coating)

[0105] Sample number Experimental Group 1 Experimental Group 2 Experimental Group 3 Open circuit potential (V) -0.185 -0.093 -0.086 <![CDATA[Current density (×10 -6 A / cm 2 )]]> 3.351 3.126 3.279

[0106] Example 2: Performance Comparison of Magnesium Alloy Hollow Nails Before and After Inorganic Ceramic Coating Processing

[0107] This embodiment uses two groups of magnesium alloy hollow nails as experimental objects. One group is 2CaZn, and the composition of the bulk material of the magnesium alloy hollow nails in this group is: 2% Ca, 1% Zn, total impurities less than 0.1%, and the remainder Mg. The other group is 4CaZn, and the composition of the bulk material of the magnesium alloy hollow nails in this group is: 4% Ca, 1% Zn, total impurities less than 0.1%, and the remainder Mg. Other processing conditions are the same as those for experimental group 1 in Example 1.

[0108] The changes in open circuit potential and corrosion current density of the magnesium alloy hollow nails in the two groups were detected before and after the addition of inorganic ceramic coating (i.e., MAO treatment) to analyze their corrosion resistance performance.

[0109] 1. Detection method:

[0110] Using an electrochemical workstation, with a 0.9% sodium chloride solution as the electrolyte and a saturated silver chloride electrode as the reference electrode, switch to the open circuit potential setting, set the operating parameters, and perform the measurement. Then switch to the polarization curve setting, set the operating parameters, and perform the measurement.

[0111] 2. Experimental Results and Analysis

[0112] From Tables 3-4 and Figure 10 The results show that, after the addition of an inorganic ceramic coating (i.e., MAO treatment), the open circuit potential of the magnesium alloy hollow nail body in this application is significantly reduced to -0.115V, and the corrosion current density is reduced to 3.16×10⁻⁶. -6 A / cm 2 .

[0113] The test results show that after the inorganic ceramic coating is added to the surface of the magnesium alloy hollow nail body (also the aforementioned magnesium alloy rod), the tendency to corrode is reduced to 1 / 6 of the original, and the corrosion resistance is greatly improved.

[0114] Table 3 Open circuit potential and current density of untreated magnesium alloy hollow nail bodies

[0115]

[0116] Table 4. Open circuit potential and current density of the magnesium alloy hollow nail body after adding inorganic ceramic coating.

[0117]

[0118] Example 3: Performance Comparison of Different Use Methods of the Magnesium Alloy Implant Device of the Present Invention

[0119] 1. Experimental Methods

[0120] Experimental group 1 and comparative examples 1 and 2 were set up respectively for implementation 1. The instruments in experimental group 8, comparative examples 1 and 2 were used as subjects in in vitro simulated degradation experiments. A schematic diagram of the in vitro simulated magnesium alloy degradation experimental apparatus (i.e., the hydrogen evolution experimental apparatus) is shown below. Figure 11 As shown, this method determines the hydrogen production volume by water displacement, thereby obtaining the degradation rate of magnesium alloys.

[0121] (1) The experimental groups are specifically set up as follows:

[0122] Experimental Group 1: Magnesium alloy implantation device (an assembly of a hollow magnesium alloy core and a magnesium alloy guide needle) prepared according to the method of Experimental Group 1 in Example 1;

[0123] Comparative Example 1: The difference from Experimental Group 1 is that only a magnesium alloy hollow nail (with coating) is provided, without a built-in magnesium alloy guide pin;

[0124] Comparative Example 2: The difference from Experimental Group 1 is that only a magnesium alloy hollow nail body is provided, without an inorganic ceramic coating or a built-in magnesium alloy guide pin.

[0125] Comparative Example 3: Using existing magnesium alloy WE43.

[0126] (2) Specific experimental steps and conditions: Immerse the magnesium alloy instruments of each group in PBS buffer solution. The specific apparatus is as follows: Figure 11 Install as shown. After installation, record the hydrogen drainage volume and indoor temperature daily, and replace the degradation simulation solution weekly.

[0127] 2. Experimental Results and Analysis

[0128] Following the above method, samples from each experimental group were simulated for in vitro degradation in PBS buffer for 2 months. The cumulative volume curves of hydrogen release from magnesium alloys in each group are shown below. Figure 12 As shown. During the first week of simulated degradation, the hydrogen release rates of the magnesium alloy implants in the three test groups were similar, but subsequently, differences emerged:

[0129] ① Comparative Example 2 without coating or guide pin: obvious pitting corrosion points formed on the surface of the hollow nail body, the hydrogen release volume increased rapidly, and the nail lost its mechanical support after 30 days of degradation and broke at the corrosion point.

[0130] ② Comparative Example 1 of coated magnesium alloy hollow nail: The hydrogen release rate of this magnesium alloy hollow nail is relatively stable, and the release curve is linear. Within 30 days of degradation, it tends to be uniformly corroded. After 30 days, pitting corrosion points appear. After 60 days of degradation, the nail loses mechanical support and breaks.

[0131] ③ Comparative Example 3: Magnesium alloy WE4 was pulverized and degraded within one week.

[0132] ④ Experimental Group 1: Due to the coating and the combination with the magnesium alloy hollow nail, the hydrogen release rate of this group is slow, uniform and stable. After 60 days of continuous degradation, corrosion was found at both ends of the nail, but no pitting corrosion was found in the middle section, which can maintain the mechanical support function. Based on the hydrogen release rate in the early stage, the complete degradation cycle of the magnesium alloy instrument in this group is estimated to be 2 years.

[0133] Based on the above experimental results, it can be seen that the magnesium alloy implantation device provided in this application protects the magnesium alloy hollow nail with high open circuit potential by sacrificing the magnesium alloy guide needle through the mutual cooperation of the self-corrosion potential difference magnesium alloy hollow nail and magnesium alloy guide needle, so that the main load-bearing unit can provide longer mechanical support.

[0134] Example 4: Optimization Experiment of Magnesium Alloy Hollow Nail Body Material

[0135] 1. Experimental Method:

[0136] (1) Preparation of magnesium alloy hollow nail body material (or magnesium alloy guide needle):

[0137] This embodiment sets up experimental groups 4 to 7. The formulations of the magnesium alloy hollow nail body material for each experimental group are shown in Table 5. The preparation methods and conditions are the same as in Example 1.

[0138] Table 5. Material formulations of magnesium alloy hollow nail bodies for each experimental group.

[0139]

[0140] (2) Take the magnesium alloy hollow nail body material of experimental group 4-7 and test its mechanical properties (tensile strength, ductility) and electrochemical properties (open circuit potential). The test method is as follows: refer to GB / T 228.1 Metallic materials tensile test part 1: room temperature test method YY / T1552-2017 Surgical implant evaluation of metal implant materials and long-term corrosion behavior of medical devices open circuit potential measurement method; the magnesium alloy element content is analyzed by inductively coupled plasma optical emission spectrometry (ICP-OES).

[0141] (3) To evaluate the corrosion performance of the above materials, in vitro degradation and weight loss experiments were conducted on the magnesium alloy hollow nail samples of experimental groups 4 and 6. According to ASTM G1-03 standard, the corrosion rate was calculated according to the following formula:

[0142] Corrosion rate = (K×W) / (A×T×D)

[0143] Where, K = 8.76 × 10 4 W represents the weight loss (g), and A represents the sample surface area (cm²). 2 T is the soaking time (h), and D is the sample density (g / cm³). 3 ).

[0144] 2. Experimental Results and Analysis

[0145] (1) As can be seen from the results in Table 6, 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 the material suitable for clinical fixation screws is generally not less than 10%. Therefore, both Mg-2Ca-1Zn and Mg-4Ca-1Zn can meet the requirements, while Mg-2Ca-1Zn is more ideal as a material for fixing screw processing.

[0146] Analysis of the corrosion resistance of the materials shows that as the Ca ratio increases, the open circuit potential of the alloy gradually decreases, indicating that its corrosion resistance weakens. From an electrochemical perspective, it is also proven that Mg-2Ca-1Zn and Mg-4Ca-1Zn have good corrosion resistance potential.

[0147] Table 6 Mechanical and Electrochemical Properties of Magnesium Alloy Materials

[0148] 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

[0149] (2) The results in Table 7 show that the proportions of each alloying element are within the control range. The main impurities in the alloy are Al and Fe, while other impurities are all <0.0001 and are not shown in the table. The total impurity content is controlled within the range of <0.1%. Based on the above analysis of the physical properties of the materials, the materials of experimental group 4 (Mg-2Ca-1Zn) and experimental group 6 (Mg-4Ca-1Zn) are ideal magnesium alloy implant materials.

[0150] Table 7 Elemental Content Analysis of Magnesium Alloys

[0151]

[0152]

[0153] (3) The results of the 130-day weightlessness test on the uncoated magnesium alloy hollow nail body (or magnesium alloy guide pin) are shown in Table 8. The corrosion appearance is as follows: Figure 4 As shown.

[0154] Preliminary material degradation tests show that Mg4CaZn and Mg2CaZn have slow corrosion rates, with Mg4CaZn exhibiting a slower corrosion rate, which corresponds to the magnitude of the material's open-circuit potential.

[0155] Based on all the aforementioned 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. Among them, Mg-2Ca-1Zn has a higher elongation and better corrosion resistance. Therefore, in subsequent embodiments, the magnesium alloy hollow nail bodies of Mg-2Ca-1Zn will be used as the object for further experiments.

[0156] Table 8. Results of weight loss experiments on untreated alloys

[0157]

[0158] Example 5: Optimization of Inorganic Ceramic Coatings

[0159] Using the magnesium alloy hollow nail body prepared by experimental group 4 (Mg-2Ca-1Zn) in Example 2 as the object, the bioceramic coating was processed to prepare magnesium alloy hollow nails, optimize the voltage parameters applied by micro-arc oxidation, and explore the effects of voltage, frequency, duty cycle on coating thickness, roughness and calcium content of coating.

[0160] 1. The effect of voltage on coating

[0161] (1) Experimental and testing methods

[0162] The bioceramic coating processing method in this embodiment is performed according to the steps and methods of experimental group 1 in Example 1. Specifically, the forward voltage of the micro-arc oxidation treatment is set as a variable, and the effect of changes in the forward voltage on the coating thickness, calcium content, and surface roughness of the magnesium alloy hollow nail is analyzed.

[0163] (2) Experimental Results and Analysis

[0164] The test results are as follows Figure 5 As shown, with the increase of voltage, the thickness and calcium content of the bioceramic coating of the magnesium alloy hollow nail gradually increase. The surface roughness of the magnesium alloy hollow nail is better at around 380V. Therefore, a positive voltage of 380-420V was used to conduct subsequent experiments to optimize the micro-arc oxidation conditions.

[0165] 2. Parameter testing of micro-arc oxidation treatment

[0166] (1) Experimental method:

[0167] Based on the aforementioned preliminary experiments, the range of process parameters for surface coating research was confirmed. The specific research parameters are shown in Table 9. Micro-arc oxidation experiments were conducted on three magnesium alloy materials with different elemental compositions according to these parameter settings (the specific operation method is referred to in Example 1). These three magnesium alloy materials are Mg2CaZn alloy, EZ30 magnesium alloy, and WE43 magnesium alloy.

[0168] Table 9. Settings of Micro-arc Oxidation Parameters

[0169]

[0170] (2) Test method:

[0171] A. Test and evaluation methods for degradation rate of material surface coating parameters:

[0172] The samples (φ16mm*3mm) prepared for the micro-arc oxidation parameter investigation were immersed in 3.5% NaCl solution for 180 days. After that, they were taken out, washed with water to remove the surface degradation products, and dried to evaluate the coating corrosion.

[0173] B. In vitro degradation weight loss experiment: Following the method in Example 2, the Mg2CaZn alloy and Mg4CaZn alloy materials after inorganic ceramic coating were tested after 120 days of treatment.

[0174] (3) Experimental Results and Analysis

[0175] ①Based on Figure 6 The corrosion results of the coatings of various materials were evaluated, and the optimal parameters for the micro-arc oxidation process were set as follows: voltage 400V, frequency 1000Hz, duty cycle 10%, and processing time 10min; and the Mg2CaZn alloy coating of this application has the best corrosion resistance.

[0176] ② A comprehensive analysis of the 120-day in vitro degradation and weight loss test results in Table 10 shows that the magnesium alloy hollow nail body material (Mg2CaZn) in Experimental Group 1) of Example 1 has a lower degradation and corrosion rate and is more corrosion resistant after surface treatment.

[0177] Table 10 Results of weight loss experiments on the alloy after coating addition

[0178]

[0179] Example 6: Determination of the physical properties of magnesium alloy hollow nails

[0180] 1. Experimental Methods

[0181] Scanning electron microscopy was performed on the magnesium alloy hollow nail body of Experiment Group 1 in Example 1 before and after the coating was added, and elemental analysis and analysis of the second phase in the alloy were also performed.

[0182] 2. Experimental Results and Analysis

[0183] (1) As Figure 7 and Figure 9 As shown, the magnesium alloy hollow nail body (or magnesium alloy rod) exhibits a typical dynamic recrystallization structure—fine equiaxed grains; the average grain size, measured by the intercept method, is 2.8 ± 0.3 μm. The uniform and small grains contribute to the material's homogeneity, and the smaller grain size improves corrosion resistance.

[0184] from Figure 8 The analysis of the results showed that the proportions of Ca and Zn elements in the material were basically consistent with the material design composition; no obvious inclusions or defects were found in the microstructure.

[0185] (2) Figure 13The image shows the SEM characterization results of the through holes of magnesium alloy hollow nails with and without coating. As can be seen from the comparison of the images, after coating treatment, a uniform ceramic coating with a thickness of about 5-10 μm is generated on the inner surface of the through holes of magnesium alloy hollow nails, and the coating surface has an uneven structure.

[0186] Figure 14 The image shows an SEM image of the ceramic coating on the outer surface of a magnesium alloy hollow nail. As can be seen from the image, the micro-arc oxidation layer on the nail surface is uniform and flat, and can completely cover the surface of the magnesium alloy nail. At the same time, the surface of the layer has uniformly distributed blind holes with a diameter of about 1-5 μm.

[0187] It is understood that those skilled in the art can make equivalent substitutions or modifications to the technical solutions and concepts of this invention, and all such substitutions or modifications should fall within the protection scope of the appended claims.

Claims

1. A magnesium alloy implantable device, characterized in that, The device includes a magnesium alloy hollow nail and a magnesium alloy guide pin used in conjunction with the magnesium alloy hollow nail. The magnesium alloy hollow nail consists of a magnesium alloy hollow nail body and an inorganic ceramic coating covering the surface of the magnesium alloy hollow nail body. The inorganic ceramic coating is also uniformly distributed on all inner surfaces of the through hole. The magnesium alloy hollow nail body has a through hole along its central axis for the magnesium alloy guide pin to pass through. The magnesium alloy guide pin has a rod-shaped structure, with its outer diameter slightly smaller than the inner diameter of the through hole of the magnesium alloy hollow nail, and its length greater than that of the magnesium alloy hollow nail. Both ends of the magnesium alloy guide pin are exposed outside the through hole. The outer wall of the magnesium alloy hollow nail body has threads distributed along its length. The self-corrosion potential of the inorganic ceramic coating is higher than that of the magnesium alloy hollow nail body. The material of the magnesium alloy guide pin is the same as that of the magnesium alloy hollow nail body. The threaded portion includes a first threaded portion and a second threaded portion distributed on the outer surface of the magnesium alloy body. The two threaded portions are arranged adjacent to each other or spaced apart. A set groove is provided on the outer end face of the head of the magnesium alloy hollow nail body.

2. The magnesium alloy implant device according to claim 1, characterized in that, The magnesium alloy hollow nail body material comprises the following components by mass percentage: 1.0-6.0% Ca, 0.8-1.2% Zn, less than 0.1% total impurities, and the remainder being Mg.

3. The magnesium alloy implant device according to claim 1, characterized in that, The inorganic ceramic coating is a micro-arc oxidation coating, which includes the following elements in mass percentage: Mg 20-40%, O 20-40%, P 8-20%, Ca 3-6%, F 15-25%.

4. The method for preparing the magnesium alloy guide needle of the magnesium alloy implantable device as described in claim 1, characterized in that, The preparation method is as follows: first, a magnesium alloy rod is prepared, and then the magnesium alloy rod is machined into a magnesium alloy guide needle by a lathe; wherein, the magnesium alloy rod includes the following components in the following mass percentages: 1.0-6.0% Ca, 0.8-1.2% Zn, total impurities less than 0.1%, and the remainder is Mg.

5. The method for preparing the magnesium alloy hollow nail of the magnesium alloy implant device as described in claim 1, characterized in that, Includes the following steps: S1. Prepare magnesium alloy rods and process them into magnesium alloy hollow nail bodies using a lathe. The magnesium alloy rods contain the following components by mass percentage: 1.0-6.0% Ca, 0.8-1.2% Zn, less than 0.1% total impurities, and the remainder being Mg. S2. A layer of inorganic ceramic coating is processed on the surface of the magnesium alloy hollow nail body to obtain a magnesium alloy hollow nail.

6. The method for preparing the magnesium alloy hollow nail of the magnesium alloy implant device according to claim 5, characterized in that, The preparation method of magnesium alloy rods is as follows: S11. Under the protection of a mixed protective gas atmosphere, melt pure magnesium at 750~800℃ and hold for 30~60 min; add the corresponding mass percentage of high-purity zinc and pure calcium, stir mechanically for 3-5 min, hold for 20~30 min; cool to 700~730℃ and pour into ingots. S12. Under the conditions of extrusion ratio of 20~80, extrusion temperature of 250~400℃, and extrusion shaft speed of 0.1~1.0 mm / s, a low-temperature extrusion molding process is carried out to obtain magnesium alloy rods.

7. The method for preparing the magnesium alloy hollow nail of the magnesium alloy implant device according to claim 5, characterized in that, The processing method for inorganic ceramic coatings includes the following steps: S21. Weigh out the corresponding amounts of nano-hydroxyapatite, ethylene glycol, and triethanolamine respectively and add them to water to prepare solution A. Place the solution in an ultrasonic generator for ultrasonic-assisted maturation for 40-60 minutes. S22. Weigh out sodium hexametaphosphate and potassium fluoride dihydrate and add them to water to prepare solution B. S23. Slowly add an equal volume of solution A to solution B and stir until homogeneous to obtain solution C; S24. 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. S25. Rinse the magnesium alloy hollow nails obtained in the previous step with water and ethanol and dry them.

8. The method for preparing the magnesium alloy hollow nail of the magnesium alloy implant device according to claim 7, characterized in that, In solution A, the mass concentration of nano-hydroxyapatite is 3-5 g / L, the volume concentration of ethylene glycol is 0.015-0.025%, and the volume concentration of triethanolamine is 0.025-0.035%. In solution B, the mass and volume concentration of sodium hexametaphosphate is 4-8 g / L, and the mass and volume concentration of potassium fluoride dihydrate is 14-18 g / L.

9. The application of the magnesium alloy implant device as described in claim 1, characterized in that, The application method is as follows: the magnesium alloy hollow nail is used in combination with a magnesium alloy guide pin that penetrates its through hole; both ends of the magnesium alloy guide pin are exposed outside the magnesium alloy guide pin, and the material of the magnesium alloy guide pin is the same as the material of the magnesium alloy hollow nail body.

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