A magnesium alloy composite material, application and cervical spinal canal opening device and preparation method

Abstract

The present application relates to a magnesium alloy composite material, application and cervical spinal canal opening device and preparation method. The magnesium alloy composite material comprises a magnesium alloy base and a protective coating arranged on the surface thereof; the protective coating is a coating capable of reducing the degradation rate of the magnesium alloy. The present application also provides an application of the magnesium alloy composite material in the preparation of biomedical materials. The present application also provides a cervical spinal canal opening device comprising a support plate and a screw made of the magnesium alloy composite material; the support plate comprises an opening side, an opening area and a door shaft side, the opening side and the door shaft side are connected to the bone tissue through the screw; the door shaft side and the screw are loaded with a substance promoting the growth of bone tissue in the micropores of the protective coating, and the screw head is loaded with a substance having swelling property in body fluid and being non-conductive. The present application solves the problem that the existing titanium and titanium alloy material made fixing plate is not biodegradable, thereby requiring secondary surgery to cause damage to the human body or long-term retention in the body to cause rejection reaction and the like.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials technology, specifically to a magnesium alloy composite material, its application, a cervical spinal canal opening device, and its preparation method. Background Technology

[0002] Cervical spinal stenosis is common in middle-aged and elderly people. It is often caused by factors such as developmental cervical spinal stenosis, degenerative cervical spinal stenosis, multi-segmental cervical disc herniation, and ossification of the posterior longitudinal ligament of the cervical spine, resulting in stenosis of one or more cervical vertebrae. This leads to impaired spinal cord blood circulation and compression of the spinal cord and nerve roots, resulting in corresponding spinal cord and nerve root symptoms. Posterior cervical laminoplasty remains one of the classic surgical procedures recognized by the academic community for the treatment of severe multi-segmental cervical spinal stenosis. This surgical method directly lifts the lamina, widening the sagittal diameter of the spinal canal to relieve pressure on the spinal cord and nerve roots from the anterior and posterior sides of the spinal canal, thus achieving decompression. This surgery provides relatively thorough decompression, is relatively safe, and has a definite postoperative effect. However, there is a possibility of "re-closure" postoperatively, with the recurrence of cervical spinal stenosis symptoms. To address this issue, several implantable lamina opening devices for internal fixation have been developed, such as Arch, Centerpiece, and Neulen, which are already in clinical use. These devices use titanium plates to fix the opened lamina, effectively solving the problem of "re-closing" after surgery.

[0003] However, the titanium and titanium alloy materials used in these fixation plates are non-biodegradable. After bony healing is completed on the axial side of the opened cervical vertebral hilum, a second surgery is required to remove them. Otherwise, the foreign body remaining in the body for a long time may lead to rejection reactions (such as swelling and pain). Furthermore, titanium and titanium alloys are not bioactive and can only maintain the stability of the opening area, but do not help the bone tissue healing on the axial side of the hilum. Even more disadvantageous is that titanium and titanium alloys have a high elastic modulus, which creates a stress shielding effect on the bone tissue at the implantation site (preventing the biostimulation of external forces on the bone tissue), thereby inhibiting the healing of the bone tissue.

[0004] Therefore, it is necessary to develop higher-performance spinal canal opening instruments to improve the effectiveness of spinal canal opening surgery, accelerate the healing of the surgical site, and reduce the burden on patients. Summary of the Invention

[0005] The purpose of this invention is to provide a magnesium alloy composite material, its application, a cervical spinal canal opening device, and its preparation method, in order to solve the problems of existing fixation plates made of titanium and titanium alloy materials being non-biodegradable, thus requiring secondary surgery and causing further damage to the human body, or long-term retention causing rejection reactions with foreign objects in the body.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A magnesium alloy composite material includes a magnesium alloy matrix and a protective coating disposed on the surface of the magnesium alloy matrix; the composition of the magnesium alloy matrix includes, by mass percentage: 0.1-1.0% calcium (Ca), 0.1-5.0% zinc (Zn), with the balance being magnesium (Mg) and unavoidable impurities, the content of which does not exceed 0.01%.

[0008] The protective coating is a coating that can reduce the degradation rate of the magnesium alloy substrate.

[0009] Based on the aforementioned technical methods, by using a magnesium alloy matrix that can naturally degrade in the human body as the substrate of the fixation plate, the problems of existing fixation plates made of titanium and titanium alloy materials being non-biodegradable, thus requiring secondary surgery and causing further damage to the body, or long-term retention leading to rejection reactions with foreign bodies, are effectively solved. Since magnesium alloy degrades relatively quickly in the human body, a coating is applied to the surface of the magnesium alloy to slow down the degradation rate of the magnesium alloy matrix, thereby controlling the degradation rate of the magnesium alloy in the human body and ensuring that the manufactured fixation plate produces the expected therapeutic effect, thus allowing sufficient time for bone tissue healing. Furthermore, it has the advantages of simple material composition and low manufacturing cost.

[0010] The yield strength of the magnesium alloy composite material of this invention is measured to be 150-200 MPa, and the elongation is not less than 15%. When a 2mm thick sheet is bent 180 degrees, no surface cracks occur. For clinical use, the magnesium alloy composite material needs good on-site shaping properties so that doctors can appropriately shape it according to the actual size and opening of the patient's cervical spinal canal. Therefore, the magnesium alloy needs to meet certain mechanical property requirements. If the yield strength is higher than 200 MPa, it is difficult to meet the on-site shaping requirements of the magnesium alloy composite material in actual use; an elongation of more than 15% is necessary for both the plastic processing during the manufacture of support plates and screws and to prevent cracking during on-site shaping.

[0011] By strictly controlling the impurities in magnesium alloy composites to not exceed 0.01%, the uniformity of the microstructure and properties of magnesium alloy composites is effectively guaranteed, and the biocompatibility of magnesium alloy composites is also effectively guaranteed.

[0012] Preferably, the protective coating is composed of at least one of calcium phosphate, magnesium phosphate, magnesium silicate, and calcium silicate.

[0013] Preferably, the protective coating has a loose structure or has micropores with a pore size between 1 and 5 micrometers, and the micropores are exposed on the surface of the protective coating.

[0014] Preferably, the thickness of the protective coating is between 2 and 20 micrometers.

[0015] The pore diameter and coating thickness in the coating can be measured using a scanning electron microscope.

[0016] Multiple experimental studies have shown that when the thickness of the protective coating is less than 2 micrometers, it is difficult to effectively control the degradation rate. If it is greater than 20 micrometers, large internal stress is easily generated in the protective coating, which makes it prone to cracking and peeling during the plasticization process before implantation and during implantation after it is made into a fixation plate. Therefore, the thickness of the protective coating should be controlled between 2 and 20 micrometers.

[0017] Preferably, the composition of the magnesium alloy matrix includes, by mass percentage: 0.1-1.0% calcium (Ca), 0.1-5.0% zinc (Zn), 0.01-0.2% strontium (Sr), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%.

[0018] To expand the application scenarios of magnesium alloy composites, strontium is added to them, making them suitable for use in human environments where osteoporosis is a risk factor. This enhances the functionality of magnesium alloy composites while ensuring that product costs are not too high, thus reducing the economic burden on users.

[0019] Preferably, the composition of the magnesium alloy matrix includes, by mass percentage: 0.1-1.0% calcium (Ca), 0.1-5.0% zinc (Zn), 0.01-0.2% selenium (Se), with the balance being magnesium (Mg) and unavoidable impurities, the content of which does not exceed 0.01%.

[0020] To expand the application scenarios of magnesium alloy composites, selenium is added to them, making them suitable for use in human environments where bone tumors are a risk factor. This enhances the functionality of magnesium alloy composites while ensuring that product costs remain low, reducing the financial burden on users.

[0021] Preferably, the composition of the magnesium alloy matrix includes, by mass percentage: 0.1-1.0% calcium (Ca), 0.1-5.0% zinc (Zn), 0.01-0.2% strontium (Sr), 0.01-0.2% selenium (Se), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%.

[0022] Ca, the most abundant cation in bone tissue, possesses excellent biocompatibility. In biodegradable magnesium alloys, it can produce good solid solution strengthening and precipitation strengthening effects, improving the mechanical properties of the door opening device. Adding Ca to the magnesium alloy composite material of the door opening device allows for the release of Ca during its degradation process, promoting bone tissue repair. Especially when combined with functional substances that promote bone growth on the door hinge side, it can accelerate the growth of vertebral bone, promote the early formation of stable natural bone support at the door hinge, and prevent the "re-closing" phenomenon caused by the decrease in mechanical support during door opening device degradation. Multiple experimental studies have shown that if the Ca content is below 0.1%, its effect on promoting bone tissue repair is not effective; if the Ca content is above 1%, segregation is likely to occur, significantly reducing the plasticity and corrosion resistance of the magnesium alloy.

[0023] Zinc (Zn) is an essential trace element for the human body, exhibiting excellent biocompatibility. It is also a commonly used alloying element in magnesium alloys, providing effective solid solution strengthening and precipitation strengthening to improve the mechanical properties of door opening devices. Adding Zn to door opening device materials can also release Zn during its degradation process, potentially treating spinal cord injuries sustained during or after door opening surgery and offering some protection to the spinal cord in the opening area. However, numerous experimental studies have demonstrated that if the Zn content is below 0.1%, its strengthening and spinal cord protection effects are not effectively realized; if the Zn content is above 5%, segregation is likely to occur, significantly reducing the alloy's plasticity and corrosion resistance, and increasing the risk of overheating during the hot working of magnesium alloys.

[0024] Sr is an essential trace element for the human body, mainly found in bones. It plays a crucial role in preventing osteoporosis and can promote the absorption of calcium (Ca) by bones. Adding Sr to door opening device materials helps promote the absorption of Ca generated during material degradation by bone tissue, accelerating bone repair and improving the door hinge support function. It can also have a certain therapeutic effect on osteoporosis. Multiple experimental studies have shown that if the Sr content is below 0.01%, its beneficial effects on bone tissue are not effectively realized; if the Sr content is above 0.2%, it easily induces a low-melting-point eutectic structure in magnesium alloys, significantly reducing the alloy's plasticity.

[0025] Se (Se) is an essential trace element for the human body and has a good preventive effect against bone tumors. Adding Se to the material of the door opening device allows for the release of Se during its degradation process, generating an anti-bone tumor effect. This makes the door opening device made of the magnesium alloy composite material of this invention usable in certain cases of cervical spinal canal opening with bone tumors, and can produce a certain preventive effect against bone tumors. Multiple experimental studies have shown that if the Se content is below 0.01%, its preventive effect against bone tumors is not effectively demonstrated; if the Se content is above 0.2%, excessive Mg and Se compounds are easily formed in the magnesium alloy, significantly reducing the alloy's plasticity and corrosion resistance.

[0026] Preferably, the yield strength of the magnesium alloy composite material is 150-200 MPa, and the elongation is not less than 15%.

[0027] The present invention also provides a cervical spinal canal opening device, including a support plate and screws;

[0028] The support plate has a Z-shaped structure and includes a door side for connecting the unchanging bone tissue at the vertebral bone cutting site, a door area not for direct contact with bone tissue, and a door hinge side for connecting the vertebral bone cutting site and lifting the bone tissue. The door side and door hinge side are connected to the corresponding bone tissue by the screws.

[0029] The support plate and screw are made of the magnesium alloy composite material described in this invention. The micropores of the protective coating on the side surface of the door hinge and the screw shaft surface are loaded with substances that promote bone tissue growth. The micropores of the protective coating on the screw head surface are loaded with substances that are swollen in body fluids and are non-conductive.

[0030] Based on the aforementioned technical means, the support plate and screws of the cervical spinal canal opening device are made of a fully biodegradable magnesium alloy composite material. After the device is implanted in the cervical spine, the support plate expands the vertebral laminae to widen the sagittal diameter of the spinal canal (forming an "opening"). The opening area of ​​the support plate forms a "doorway" at the opened position of the spinal canal, directly facing the gap created by the opening surgery, without directly contacting the bone tissue. The opening side of the support plate is used to connect to the unchanged side of the spinal canal bone resection site, meaning the bone tissue on that side remains unchanged. The opening side is fixed to the bone tissue with screws. The hinge side is the side where the vertebral canal is cut, meaning the cut vertebral canal is lifted from this side to create an "opening" effect. Therefore, the bone tissue on this side will fracture to some extent. The hinge side is fixed to the lifted bone tissue with screws. The opening side and hinge side of the support plate are fixed to the cervical vertebrae with screws, effectively preventing the "closing" of the door. After the bone tissue on the hinge side at the opening position of the vertebral canal heals and forms a stable bony support, the magnesium alloy composite material can be completely degraded, thus effectively avoiding the safety hazards caused by secondary surgery and long-term retention of foreign objects in the body.

[0031] Since the opening area of ​​the support plate does not directly contact the bone tissue, and the bone tissue in contact with the opening side remains unchanged, the protective coating of the opening area and the opening side of the support plate does not need to be loaded with other substances. Because the vertebral bone in contact with the hinge side of the support plate has a certain degree of fracture, the screw shaft needs to be driven into the bone tissue, causing bone damage. Therefore, functional substances that promote bone tissue growth are introduced into the protective coating on the hinge side and the screw shaft surface to effectively promote the repair of damaged bone tissue. Since the screw head contacts the threaded hole on the support plate and forms a tight fit, crevice corrosion can occur on the contact surface under the influence of body fluids, leading to early loosening and worsening the "opening" effect. Therefore, a substance with swelling properties in body fluids and which is non-conductive is introduced into the protective coating on the screw head surface. After implantation, this substance expands in volume to fill the crevice, preventing body fluids from entering the crevice and causing corrosion. Furthermore, this substance itself is non-conductive and can also create an isolation effect between the screw and the support plate, further inhibiting corrosion.

[0032] Preferably, a first threaded hole is provided on the door opening side, and the head of one screw is completely inserted into the first threaded hole; a second threaded hole is provided on the door hinge side, and the head of another screw is completely inserted into the second threaded hole.

[0033] By setting a first threaded hole on the opening side of the support plate, a screw is driven into the bone tissue on the unchanged side of the spinal canal cut position after passing through the first threaded hole. At the same time, a second threaded hole is set on the door hinge side of the support plate, so that the screw of another screw is driven into the bone tissue on the lifted side of the spinal canal cut position after passing through the second threaded hole. The support plate is fixed on both sides of the cut position, so that the matching cut surfaces have sufficient distance to form an effective "opening" size, thereby achieving the purpose of treating cervical spinal stenosis.

[0034] Preferably, the micropores of the protective coating are loaded with at least one of bone morphogenetic protein, parathyroid hormone, and fibroblast growth factor, with a loading amount of 0 to 30 micrograms.

[0035] Preferably, the micropores of the protective coating are loaded with at least one of sodium alginate, guar gum and xanthan gum, with a loading amount of 0 to 30 micrograms.

[0036] The loading of the two types of substances was determined by testing the mass difference before and after the treatment.

[0037] Bone morphogenetic protein, parathyroid hormone, and fibroblast growth factor are substances that promote bone tissue growth. Sodium alginate, guar gum, and xanthan gum are substances that swell in body fluids and are non-conductive.

[0038] The present invention also provides an application of the magnesium alloy composite material as described herein, wherein the magnesium alloy composite material is used in the preparation of biomedical materials.

[0039] The present invention also provides an application of the magnesium alloy composite material as described herein, wherein the magnesium alloy composite material is used in the preparation of a spinal canal opening device.

[0040] Preferably, the method for preparing the cervical spinal canal opening device includes the following steps:

[0041] Magnesium alloy matrix was prepared by vacuum melting, using magnesium with a purity of not less than 99.99% (weight percentage), zinc with a purity of not less than 99.99% (weight percentage), strontium with a purity of not less than 99.95% (weight percentage), selenium with a purity of not less than 99.99% (weight percentage), and MgCa20 master alloy with a total impurity content of not more than 0.01% (weight percentage) as raw materials. The melting temperature was 700-800℃, the melting time was 10-30 minutes, and the furnace pressure was not more than 0.01Pa.

[0042] Then, through extrusion, rolling, and drawing, magnesium alloy matrix sheets and magnesium alloy matrix wires are produced.

[0043] A magnesium alloy substrate sheet is processed into a support plate using a stamping process, and a first threaded hole and a second threaded hole are machined on the support plate.

[0044] Magnesium alloy base wire is machined into screws using machining processes;

[0045] A protective coating is formed on the surface of the support plate and screws using anodizing or liquid phase deposition methods.

[0046] A selective liquid-phase impregnation method is used to load a substance that promotes bone tissue growth onto the protective coating of the hinge side surface of the support plate and the screw shank surface, and to load a substance that is swellable in body fluids and non-conductive onto the protective coating of the screw head surface. The solution used in the selective liquid-phase impregnation method is ultrapure water as the solvent, wherein the concentration of the substance that promotes bone tissue growth or the substance that is swellable in body fluids and non-conductive is 1-10% (weight percentage), the impregnation temperature is 30℃-100℃, and the impregnation time is 10-60 minutes.

[0047] The beneficial effects of this invention are:

[0048] 1) The magnesium alloy composite material of this invention effectively solves the problems of existing fixation plates made of titanium and titanium alloys being non-biodegradable, thus requiring secondary surgery and causing further damage to the body, or causing rejection reactions due to long-term retention in the body, by using a magnesium alloy matrix that can biodegrade naturally in the human body as the substrate of the fixation plate. Since magnesium alloys degrade relatively quickly in the human body, a coating is applied to the surface of the magnesium alloy to reduce the degradation rate of the magnesium alloy matrix, thereby regulating the degradation rate of the magnesium alloy in the human body and ensuring that the finished fixation plate produces the expected therapeutic effect, thus allowing sufficient time for bone tissue healing. It also has the advantages of simple material composition and low manufacturing cost.

[0049] 2) The cervical spinal canal opening device of the present invention uses a support plate and screws made of a fully biodegradable magnesium alloy composite material. After implantation into the cervical spine, the support plate expands the vertebral laminae to enlarge the sagittal diameter of the spinal canal (forming an "opening"). The opening area of ​​the support plate forms a "doorway" at the opened position of the spinal canal, directly facing the gap created by the opening surgery, without directly contacting the bone tissue. The opening side of the support plate is used to connect to the unchanged side of the spinal bone resection position, meaning the bone tissue on that side remains unchanged. The opening side is fixed to the bone tissue by screws, and the door hinge side is attached to the spinal bone. The side of the vertebral canal that is lifted at the cut site creates an "opening" effect. As a result, the bone tissue on this side will fracture to some extent. The door hinge side is fixed to the lifted bone tissue with screws. The opening side and door hinge side of the support plate are fixed to the cervical vertebrae with screws, effectively preventing the "closing" of the door. After the bone tissue on the door hinge side of the opened vertebral canal heals and forms a stable bony support, the magnesium alloy composite material can be completely degraded. This effectively avoids the safety hazards caused by secondary surgery and long-term retention of foreign bodies in the body. It has application value in the field of biomedical materials technology. Attached Figure Description

[0050] Figure 1 This is a structural schematic diagram of the support plate;

[0051] Figure 2 This is another structural schematic diagram of the support plate;

[0052] Figure 3 This is a schematic diagram of the screw structure;

[0053] Figure 4 The image shows the surface morphology of the magnesium alloy composite material prepared in Example 1.

[0054] Figure 5 This is a cross-sectional morphology diagram of the magnesium alloy composite material prepared in Example 2;

[0055] Figure 6The image shows the surface morphology of the magnesium alloy composite material prepared in Example 3.

[0056] Figure 7 This is a cross-sectional morphology diagram of the magnesium alloy composite material prepared in Example 4;

[0057] Figure 8 The surface morphology of test sample 1;

[0058] Figure 9 The surface morphology of test sample 1;

[0059] Among them, 1-support plate, 11-door opening side, 111-first threaded hole, 12-door opening area, 13-door hinge side, 131-second threaded hole; 2-screw, 21-screw rod, 22-nail head. Detailed Implementation

[0060] The embodiments of the present invention will be described below with reference to the accompanying drawings and preferred embodiments. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention and not for limiting the scope of protection of the present invention.

[0061] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0062] Example 1

[0063] A magnesium alloy composite material includes a magnesium alloy matrix and a protective coating disposed on the surface of the magnesium alloy matrix; the composition of the magnesium alloy matrix, by mass percentage, includes: 0.5% calcium (Ca), 4.5% zinc (Zn), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%; the alloy melting temperature is 720℃, the melting time is 30 minutes, and the furnace pressure is maintained below 0.01 Pa;

[0064] The protective coating is a coating that can reduce the degradation rate of the magnesium alloy substrate. The protective coating is composed of calcium phosphate and is grown on the surface of the magnesium alloy substrate by anodizing. The protective coating has micropores with an average pore size of about 4 micrometers that are exposed on the surface, and the average thickness of the protective coating is 15 micrometers.

[0065] The magnesium alloy composite material in this embodiment can be applied to a human body environment with healthy bones.

[0066] Example 2

[0067] A magnesium alloy composite material includes a magnesium alloy matrix and a protective coating disposed on the surface of the magnesium alloy matrix; the composition of the magnesium alloy matrix, by mass percentage, includes: 0.1% calcium (Ca), 5.0% zinc (Zn), 0.2% strontium (Sr), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%; the alloy melting temperature is 700℃, the melting time is 20 minutes, and the furnace pressure is maintained below 0.01 Pa;

[0068] The protective coating is a coating that can reduce the degradation rate of the magnesium alloy substrate. The protective coating is a mixture of calcium phosphate and magnesium phosphate in a mass ratio of 1:1. The protective coating is formed on the surface of the magnesium alloy substrate by anodizing. The protective coating has micropores with an average pore size of 10 micrometers exposed on the surface and a thickness of 20 micrometers.

[0069] The magnesium alloy composite material in this embodiment can be applied to human environments with a risk of osteoporosis.

[0070] Example 3

[0071] A magnesium alloy composite material includes a magnesium alloy matrix and a protective coating disposed on the surface of the magnesium alloy matrix; the composition of the magnesium alloy matrix, by mass percentage, includes: 0.8% calcium (Ca), 0.2% zinc (Zn), 0.2% selenium (Se), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%; the alloy melting temperature is 760℃, the melting time is 25 minutes, and the furnace pressure is maintained below 0.01 Pa;

[0072] The protective coating is a coating that can reduce the degradation rate of the magnesium alloy substrate. The protective coating is composed of magnesium silicate and is deposited on the surface of the magnesium alloy substrate by liquid phase deposition. The protective coating has a loose structure and an average thickness of 4 micrometers.

[0073] The magnesium alloy composite material in this embodiment can be applied in human environments with a risk of bone tumors.

[0074] Example 4

[0075] A magnesium alloy composite material includes a magnesium alloy matrix and a protective coating disposed on the surface of the magnesium alloy matrix; the composition of the magnesium alloy matrix, by mass percentage, includes: 1.0% calcium (Ca), 0.1% zinc (Zn), 0.01% strontium (Sr), 0.01% selenium (Se), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%; the alloy melting temperature is 800℃, the melting time is 15 minutes, and the furnace pressure is maintained below 0.01 Pa;

[0076] The protective coating is a coating that can reduce the degradation rate of the magnesium alloy substrate. The protective coating is a mixture of magnesium silicate and calcium silicate in a mass ratio of 1:1. The protective coating is deposited on the surface of the magnesium alloy substrate by liquid phase deposition. The protective coating has a loose structure and an average thickness of 2 micrometers.

[0077] The magnesium alloy composite material in this embodiment can be applied in human environments with potential risks of bone tumors and osteoporosis.

[0078] Example 5

[0079] like Figures 1 to 3 As shown, a method for preparing a cervical spinal canal opening device includes the following steps:

[0080] S1. A magnesium alloy matrix is ​​prepared by smelting, and then extruded, rolled, and drawn to produce magnesium alloy matrix sheets and wires. The material composition of the obtained magnesium alloy matrix sheets and wires, by mass percentage, includes: 0.3% calcium (Ca), 3% zinc (Zn), 0.05% strontium (Sr), 0.05% selenium (Se), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%. The alloy smelting temperature is 750℃, the smelting time is 30 minutes, and the furnace pressure is maintained below 0.01 Pa.

[0081] The obtained magnesium alloy sheet has a yield strength of 150 MPa, an elongation of 20%, and no surface cracks after bending the 2 mm thick sheet 180 degrees.

[0082] S2. The magnesium alloy substrate sheet is processed into a support plate 1 by stamping process. The support plate 1 has a Z-shaped structure and includes an opening side 11 for connecting the unchanging bone tissue of the vertebral bone cutting site, an opening area 12 for not directly contacting the bone tissue, and a door hinge side 13 for connecting the vertebral bone cutting site and lifting the bone tissue. The opening side 11 and the door hinge side 13 are connected to the corresponding bone tissue by the screw 2. A first threaded hole 111 is processed on the opening side 11 of the support plate 1 and a second threaded hole 131 is processed on the door hinge side 13.

[0083] S3. The magnesium alloy base wire is processed into screw 2 by machining process. Screw 2 includes screw 21 and screw head 22.

[0084] S4. A protective coating is formed on the surface of the support plate 1 and the screw 2 by anodizing. The protective coating is composed of calcium phosphate and has micropores with an average pore size of 5 micrometers exposed on the surface. The thickness of the protective coating is 15 micrometers.

[0085] S5. Bone morphogenetic protein was loaded into the micropores of the protective coating on the surface of the door hinge side 13 of the support plate 1 and the surface of the screw 21 of the screw 2 using a selective liquid phase impregnation method. The concentration of bone morphogenetic protein in the impregnation solution prepared with ultrapure water as solvent was 2%, the impregnation temperature was 45°C, the time was 40 minutes, and the loading amount was 8 micrograms. Sodium alginate was loaded into the micropores of the protective coating on the surface of the screw head 22 of the screw 2. The concentration of sodium alginate in the impregnation solution prepared with ultrapure water as solvent was 1%, the impregnation temperature was 30°C, the time was 60 minutes, and the loading amount was 30 micrograms.

[0086] S6. Drying, sterilization, and packaging yield a biodegradable spinal canal opening device.

[0087] Example 6

[0088] like Figures 1 to 3 As shown, a method for preparing a cervical spinal canal opening device includes the following steps:

[0089] S1. A magnesium alloy matrix is ​​prepared by smelting, and then extruded, rolled, and drawn to produce magnesium alloy matrix sheets and magnesium alloy matrix wires. The material composition of the obtained magnesium alloy matrix sheets and magnesium alloy matrix wires, by mass percentage, includes: 0.8% calcium (Ca), 2% zinc (Zn), 0.1% strontium (Sr), 0.15% selenium (Se), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%. The alloy smelting temperature is 780℃, the smelting time is 20 minutes, and the furnace pressure is maintained below 0.01Pa. The obtained magnesium alloy sheet has a yield strength of 200MPa, an elongation of 15%, and no surface cracks after bending a 2mm thick sheet 180 degrees.

[0090] S2. The magnesium alloy substrate sheet is processed into a support plate 1 by stamping process. The support plate 1 has a Z-shaped structure and includes an opening side 11 for connecting the unchanging bone tissue of the vertebral bone cutting site, an opening area 12 for not directly contacting the bone tissue, and a door hinge side 13 for connecting the vertebral bone cutting site and lifting the bone tissue. The opening side 11 and the door hinge side 13 are connected to the corresponding bone tissue by screws 2. A first threaded hole 111 is processed on the opening side 11 of the support plate 1 and a second threaded hole 131 is processed on the door hinge side 13.

[0091] S3. The magnesium alloy base wire is processed into screw 2 by machining process. Screw 2 includes screw 21 and screw head 22.

[0092] S4. A protective coating is formed on the surface of the support plate 1 and the screw 2 by anodizing. The protective coating is composed of magnesium silicate and calcium silicate in a mass ratio of 1:1. The protective coating has micropores with an average pore size of 5 micrometers that are exposed on the surface. The average thickness of the protective coating is 20 micrometers.

[0093] S5. Fibroblast growth factor (FGF) is loaded into the micropores of the protective coating on the surface of the door hinge side 13 of the support plate 1 and the surface of the screw 21 of the screw 2 using a selective liquid phase impregnation method. The FGF concentration in the impregnation solution prepared with ultrapure water as the solvent is 5%, the impregnation temperature is 60°C, the time is 20 minutes, and the loading amount is 10 micrograms. Xanthan gum is also loaded into the micropores of the protective coating on the surface of the screw head 22 of the screw 2. The xanthan gum concentration in the impregnation solution prepared with ultrapure water as the solvent is 7%, the impregnation temperature is 50°C, the time is 30 minutes, and the loading rate is 25 micrograms.

[0094] S6. Drying, sterilization, and packaging yield a biodegradable spinal canal opening device.

[0095] Comparative Example 1

[0096] A conventional magnesium alloy material, the composition of which, by mass percentage, includes: 0.3% calcium (Ca), 4.5% zinc (Zn), the balance being magnesium (Mg) and unavoidable impurities, the content of which does not exceed 0.01%.

[0097] Comparative Example 2

[0098] A conventional magnesium alloy material, the composition of which, by mass percentage, includes: 0.8% calcium (Ca), 3% zinc (Zn), 0.05% strontium (Sr), 0.03% selenium (Se), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%.

[0099] Detection and Analysis

[0100] 1. Degradation rate test

[0101] The corrosion degradation rates of the magnesium alloy composite materials prepared in Examples 1–6 and the conventional magnesium alloy materials prepared in Control Examples 1–2 were tested in simulated body fluids, which are widely used for in vitro biocorrosion evaluation. The test method was polarization curve method. The results are shown in Table 1.

[0102] Table 1. Test results of corrosion degradation rates of different materials

[0103]

[0104]

[0105] The corrosion degradation rate (CR) is calculated using the following formula: CR=(3270*I*H) / (2*D)

[0106] In the formula: I is the corrosion current density, and H is the alloy density (unit: g / cm³). 3 ), where D is the relative atomic weight of the alloy and CR is the corrosion degradation rate.

[0107] In Examples 5 and 6, the magnesium alloy composite materials used for corrosion performance testing were magnesium alloy matrices prepared under the same conditions as in S1, and samples were loaded with a protective coating under the same conditions as in S4 and samples with a substance that swells in body fluid and is non-conductive under the same conditions as in S5.

[0108] The results in Table 1 show that the magnesium alloy composite materials prepared in Examples 1-4 exhibited a significantly lower corrosion degradation rate compared to the conventional magnesium alloy materials prepared in Control Examples 1-2. This demonstrates that the surface protective coating proposed in this invention significantly improves the corrosion resistance of magnesium alloys in biomimetic environments and reduces the corrosion degradation rate. Furthermore, the corrosion degradation rates of the magnesium alloy composite material samples used for corrosion performance testing in Examples 5 and 6 were significantly lower than those prepared in Examples 1-4. This further demonstrates that loading a swellable and non-conductive substance in body fluid into the micropores of the protective coating further reduces the corrosion degradation rate.

[0109] 2. Cell compatibility test

[0110] The magnesium alloy composite materials prepared in Examples 1-6 and the conventional magnesium alloy materials prepared in Examples 1-2 were subjected to CCK-8 cytotoxicity tests using the extraction method. The cells used in the tests were 3T3-E1 osteoblasts. The extraction solution was prepared as follows: the materials were sterilized with ultraviolet light for 24 hours, and then... 2 Add high-glucose DMEM complete medium containing 10% fetal bovine serum at a ratio of / mL (surface area / extraction medium volume), and extract for 24h in a 37℃, 5% CO2 incubator. Filter the extract through a 0.22μm pore size filter membrane and collect for later use.

[0111] After culturing the prepared 3T3-E1 osteoblasts in 100% extract for 24 h, CCK-8 cytotoxicity test was performed, and the results are shown in Table 2.

[0112] Table 2. Cytotoxicity test results of different materials

[0113]

[0114]

[0115] In Examples 5 and 6, the magnesium alloy composite materials used for cytotoxicity testing were magnesium alloy matrices prepared under the same conditions as in S1, and samples with a protective coating loaded under the same conditions as in S4 and samples with a substance promoting bone tissue growth loaded in the micropores of the protective coating under the same conditions as in S5.

[0116] Table 2 shows that the conventional magnesium alloy materials prepared in Comparative Examples 1 and 2 exhibit cytotoxicity to osteoblasts, with a rating of Grade 2, and cannot be directly used as implantable materials. The magnesium alloy composite materials prepared in Examples 1 to 4, after being treated with a protective coating, showed improved cell compatibility and a toxicity rating reduced to Grade 1, meeting the requirements for biological implantable materials. The magnesium alloy composite materials in Examples 5 and 6, after loading substances that promote bone tissue growth into the micropores of the protective coating, showed further improved cell compatibility and a toxicity rating of Grade 0, significantly promoting osteoblast proliferation and exhibiting excellent bone tissue growth promoting properties.

[0117] 3. Observation of coating morphology

[0118] The microstructure of the magnesium alloy composite materials prepared in Examples 1 to 6 was analyzed using scanning electron microscopy, and the results are as follows: Figures 4 to 9 As shown.

[0119] Figure 4 The image shows the surface morphology of the magnesium alloy composite material prepared in Example 1. Figure 4 Observations revealed that the magnesium alloy substrate surface has a uniformly distributed protective coating with an average pore size of about 4 micrometers. Figure 5 This is a cross-sectional morphology diagram of the magnesium alloy composite material prepared in Example 2. Figure 5 Observations revealed that the average thickness of the protective coating on the surface of the magnesium alloy substrate was approximately 20 micrometers. Figure 6 The image shows the surface morphology of the magnesium alloy composite material prepared in Example 3. Figure 6 Observations revealed that the magnesium alloy substrate surface has a loosely structured protective coating; Figure 7 This is a cross-sectional morphology image of the magnesium alloy composite material prepared in Example 4. Figure 7 Observations revealed that the average thickness of the protective coating on the surface of the magnesium alloy substrate was approximately 20 micrometers. Figure 8 Test sample 1 was a magnesium alloy matrix prepared under the same conditions as in S1 in Example 5, and a protective coating was loaded under the same conditions as in S4, and bone morphogenetic proteins were loaded into the micropores of the protective coating under the same conditions as in S5. (Surface morphology images are shown.) Figure 8Observations revealed that the sample surface became smooth overall and was diffusely distributed with fine particles, indicating that bone morphogenetic proteins were successfully loaded. Figure 9 Test sample 2 was a magnesium alloy substrate prepared under the same conditions as in S1 in Example 6, and a protective coating was loaded under the same conditions as in S4, and xanthan gum was loaded into the micropores of the protective coating under the same conditions as in S5. (Surface morphology images are shown.) Figure 9 Observation revealed that the sample surface became smooth overall and contained fine fibrous material, indicating that xanthan gum was successfully loaded.

[0120] In summary, the magnesium alloy composite material of this invention, by using a biodegradable magnesium alloy matrix as the substrate of the fixation plate, effectively solves the problems of existing fixation plates made of titanium and titanium alloys being non-biodegradable, thus requiring secondary surgery and causing further harm to the body, or causing rejection reactions due to long-term retention in the body. Since magnesium alloys degrade relatively quickly in the human body, a coating is applied to the surface of the magnesium alloy to reduce the degradation rate of the magnesium alloy matrix, thereby controlling the degradation rate of the magnesium alloy in the human body and ensuring that the prepared fixation plate produces the expected therapeutic effect, thus allowing sufficient time for bone tissue healing. Furthermore, it has the advantages of simple material composition and low manufacturing cost.

[0121] The cervical spinal canal opening device of the present invention uses a support plate and screws made of a fully biodegradable magnesium alloy composite material. After implantation into the cervical spine, the support plate expands the vertebral laminae to enlarge the sagittal diameter of the spinal canal (forming an "opening"). The opening area of ​​the support plate forms a "doorway" at the opened position of the spinal canal, directly facing the gap created by the opening surgery, without direct contact with bone tissue. The opening side of the support plate is used to connect to the unchanged side of the spinal canal bone resection position, meaning the bone tissue on that side remains unchanged. The opening side is fixed to the bone tissue by screws, and the door hinge side is located at the spinal canal bone resection position. The fractured vertebral canal bone is lifted from the side of the fracture site to create an "opening" effect. As a result, the bone tissue on this side will fracture to some extent. The door hinge side is fixed to the lifted bone tissue with screws. The opening side and door hinge side of the support plate are fixed to the cervical vertebrae with screws, effectively preventing the "closing" of the door. After the bone tissue on the door hinge side of the open vertebral canal heals and forms a stable bony support, the magnesium alloy composite material can be completely degraded. This effectively avoids the safety hazards caused by secondary surgery and long-term retention of foreign objects in the body. It has application value in the field of biomedical materials technology.

[0122] The above embodiments are merely preferred embodiments provided to fully illustrate the present invention, and the scope of protection of the present invention is not limited thereto. Equivalent substitutions or modifications made by those skilled in the art based on the present invention are all within the scope of protection of the present invention.

Claims

1. A cervical spinal canal opening device, characterized in that, Includes a support plate (1) and screws (2); The support plate (1) has a Z-shaped structure and includes a door side (11) for connecting the unchanging bone tissue at the vertebral bone cutting site, a door area (12) that does not directly contact the bone tissue, and a door hinge side (13) for connecting the vertebral bone cutting site and lifting the bone tissue. The door side (11) and the door hinge side (13) are connected to the corresponding bone tissue by the screw (2). The support plate (1) and screw (2) are made of magnesium alloy composite material, which includes a magnesium alloy matrix and a protective coating disposed on the surface of the magnesium alloy matrix. The magnesium alloy matrix comprises, by mass percentage: 0.1-1.0% calcium (Ca), 0.1-5.0% zinc (Zn), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%; the protective coating is selected from at least one of calcium phosphate, magnesium phosphate, magnesium silicate, and calcium silicate; the protective coating structure has micropores with a pore size between 1 and 5 micrometers; the thickness of the protective coating is between 2 and 20 micrometers. The protective coating on the surface of the hinge side (13) and the surface of the screw (21) of the screw (2) contains a substance that promotes bone tissue growth, and the micropores of the protective coating on the surface of the screw head (22) of the screw (2) contain a substance that is swollen in body fluids and is non-conductive.

2. The cervical spinal canal opening device according to claim 1, characterized in that, The composition of the magnesium alloy matrix is ​​replaced by: 0.1-1.0% calcium (Ca), 0.1-5.0% zinc (Zn), and 0.01-0.2% strontium (Sr) by mass percentage, with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%; Alternatively, the composition of the magnesium alloy matrix may be replaced with: 0.1-1.0% calcium (Ca), 0.1-5.0% zinc (Zn), and 0.01-0.2% selenium (Se) by mass percentage, with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%.

3. The cervical spinal canal opening device according to claim 1, characterized in that, The composition of the magnesium alloy matrix is ​​replaced with: comprising, by mass percentage 0.1-1.0% calcium (Ca), 0.1-5.0% zinc (Zn), 0.01-0.2% strontium (Sr), 0.01-0.2% selenium (Se), with the balance being magnesium (Mg) and unavoidable impurities, the impurity content not exceeding 0.01%.

4. The cervical spinal canal opening device according to claim 1, characterized in that, The magnesium alloy composite material has a yield strength of 150~200MPa and an elongation of not less than 15%.

5. The cervical spinal canal opening device according to claim 1, characterized in that, The substance that promotes bone tissue growth is at least one of bone morphogenetic protein, parathyroid hormone, and fibroblast growth factor, with a loading amount of 0-30 micrograms. Furthermore, the substance that swells in body fluids and is non-conductive is at least one of sodium alginate, guar gum, and xanthan gum, with a loading amount of 0-30 micrograms.

6. A method for preparing the cervical spinal canal opening device as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Magnesium alloy matrix is ​​prepared using MgCa20 master alloy with a purity of not less than 99.99%, zinc with a purity of not less than 99.99%, strontium with a purity of not less than 99.95%, selenium with a purity of not less than 99.99%, and a total impurity content of not more than 0.01% as raw materials. The melting temperature is 700~800℃, the melting time is 10~30 minutes, and the furnace pressure is not more than 0.01Pa. Then, magnesium alloy matrix sheets and magnesium alloy matrix wires are produced by extrusion, rolling and drawing. A magnesium alloy substrate sheet is processed into a support plate (1) by stamping process, and a first threaded hole (111) and a second threaded hole (131) are processed on the support plate (1). Magnesium alloy base wire was machined into screws using machining processes (2); A protective coating is formed on the surface of the support plate (1) and screw (2) by anodizing or liquid phase deposition. A substance that promotes bone tissue growth is loaded into the protective coating on the hinge side (13) of the support plate (1) and the screw (21) of the screw (2) using a selective liquid phase impregnation method, and a substance that is swellable and non-conductive in body fluids is loaded into the protective coating on the head (22) of the screw (2). The solution used in the selective liquid phase impregnation method is ultrapure water as the solvent, wherein the concentration of the substance that promotes bone tissue growth or the substance that is swellable and non-conductive in body fluids is 1~10%, the impregnation temperature is 30℃~100℃, and the impregnation time is 10~60 minutes.

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