CN114366271A - Bone screw suitable for biological magnesium alloy and preparation method thereof - Google Patents
Bone screw suitable for biological magnesium alloy and preparation method thereof Download PDFInfo
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B17/00—Surgical instruments, devices or methods, e.g. tourniquets
- A61B17/56—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor
- A61B17/58—Surgical instruments or methods for treatment of bones or joints; Devices specially adapted therefor for osteosynthesis, e.g. bone plates, screws, setting implements or the like
- A61B17/68—Internal fixation devices, including fasteners and spinal fixators, even if a part thereof projects from the skin
- A61B17/84—Fasteners therefor or fasteners being internal fixation devices
- A61B17/86—Pins or screws or threaded wires; nuts therefor
- A61B17/866—Material or manufacture
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C23/00—Extruding metal; Impact extrusion
- B21C23/02—Making uncoated products
- B21C23/04—Making uncoated products by direct extrusion
- B21C23/08—Making wire, bars, tubes
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C31/00—Control devices, e.g. for regulating the pressing speed or temperature of metal; Measuring devices, e.g. for temperature of metal, combined with or specially adapted for use in connection with extrusion presses
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
- C22C1/03—Making non-ferrous alloys by melting using master alloys
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C23/00—Alloys based on magnesium
- C22C23/04—Alloys based on magnesium with zinc or cadmium as the next major constituent
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/06—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of magnesium or alloys based thereon
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Abstract
The invention discloses a bone screw suitable for biological magnesium alloy and a preparation method thereof, and the bone screw comprises the following steps: (1) selecting Mg-Zn-Y-Nd magnesium alloy as a raw material, and determining structural parameters of the bone screw; (2) preparing an Mg-Zn-Y-Nd magnesium alloy ingot; (3) preparing a magnesium alloy bar blank; (4) preparing a magnesium alloy extrusion round bar; (5) and (3) processing the magnesium alloy extruded round bar material obtained in the step (4) into the magnesium alloy bone screw with the structural parameters in the step (1) by a mechanical numerical control processing method, wherein the magnesium alloy bone screw has the extraction force of 98N-110N, the bending load of 230N-260N and the torsion force of 520 & ltn & gt mm.
Description
Technical Field
The invention relates to the field of novel degradable metal osteosynthesis implants and preparation thereof, in particular to a bone screw suitable for biological magnesium alloy and a preparation method thereof
Background
In recent years, the phenomena of fracture and bone injury frequently occur, medical metal materials are widely used as bone fixing instruments for treating fracture, but titanium alloy and stainless steel implanting instruments can generate stress shielding effect and need to be taken out by secondary operation, so that the pain of patients is increased, and the pain is high, and the cost is high; the absorbable polymer implant material can be degraded in vivo, and has insufficient mechanical properties, and the degradation products can cause inflammatory reaction. Magnesium alloys have gained more and more attention for biomaterials, and as a substitute material for bone implantation, compared to other metal biomaterials, magnesium alloys have several advantages: (1) can be completely degraded and absorbed by human body after being implanted, does not need secondary operation, and can be used for non-invasive examination after being implanted. (2) Has good biocompatibility. Magnesium is an element essential for the human body to maintain normal physiological functions. (3) Has proper strength and rigidity, and avoids stress shielding effect. Therefore, the degradable magnesium alloy is the most potential bone implantation device as a new generation of medical metal material and has a plurality of advantages, but the bearing capacity is insufficient, the corrosion resistance and the lower plastic deformation capacity are realized, and the corrosion speed of the stress concentration part in the human body is accelerated. Therefore, on the basis of optimizing the alloy components, the obdurability and uniform degradation performance of the bone implantation instrument are improved by utilizing the proper large plastic deformation processing technology of the magnesium alloy and the optimized design of the instrument structure.
Although the extrusion process can refine grains and improve the mechanical property of the alloy, the alloy still shows obvious pitting phenomenon after extrusion due to the non-uniformity of the structure and the existence of internal stress, which is not allowed to appear as the material of an implantation instrument. After the magnesium alloy is processed by large plastic deformation, a micro-nano structure or an ultra-fine grain structure is obtained, the mechanical property is improved, the degradation rate is obviously reduced, and the uniform degradation trend is presented. Therefore, the microstructure with fine and uniform crystal grains is beneficial to improving the obdurability and uniform degradation performance of the magnesium alloy, and the bone implantation device is not degraded to cause too fast performance attenuation.
The reciprocating extrusion technology has the following characteristics: large strain can be obtained, and the grain refining capability is strong; the extrusion and the compression are carried out simultaneously, so that the material can obtain any large strain without the danger of fracture; after repeated deformation, the shape and the size of the material are unchanged; the material is basically in a compressive stress state in the deformation process, and various defects of the initial structure of the material are eliminated. The alloy is subjected to great strain in the reciprocating extrusion process of back and forth extrusion and upsetting deformation, so that the product grains, the second phase and the inclusions can be effectively refined and are uniformly distributed in the matrix again, and fine and equiaxial uniform fine grain structures are obtained, thereby preparing the magnesium alloy with excellent performance.
Aiming at the problems of the magnesium alloy used as the bone joint implant, a finite element numerical calculation method is used for carrying out simulation calculation on the three-point bending performance, the torsion performance and the axial extraction performance. The structural characteristics and the dimensional parameters of the magnesium alloy bone screw thread can influence the external bearing capacity of the magnesium alloy bone screw, the change of the thread pitch can influence the screwing-in and screwing-out performance and the inner diameter of the bone screw, the radial bearing capacity, the occlusal force of the thread and bone and the size of the tooth form angle can influence the bearing capacity of the thread in the axial direction of unit area, and the multi-factor coupling effect needs to be discussed further.
At present, most of the bone screw structures made of metal materials are composed of a screw cap, a screw body and a screw tail 3. The nail body is the main bearing part, and the pitch, the inner diameter and the tooth form angle are the main structural parameters. Aiming at solving the problem of internal fixation of fracture of the magnesium alloy bone screw, the magnesium alloy bone screw has the advantages that the structural characteristics and structural dimension parameters are designed and optimized aiming at the characteristics of the existing bone screw structure, so that the external mechanical bearing capacity of the magnesium alloy bone screw is improved, and the stress concentration degree is reduced, and the magnesium alloy bone screw has great significance.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a bone screw suitable for biological magnesium alloy and a preparation method thereof, so that the stress concentration degree of the bone screw is reduced while the mechanical bearing capacity is improved.
In order to solve the technical problems, the invention provides a bone screw suitable for biological magnesium alloy, and the preparation method comprises the following steps:
(1) selecting Mg-Zn-Y-Nd magnesium alloy as a raw material, and determining structural parameters of the bone screw, wherein the structural parameters comprise a thread pitch P1.3mm-1.7mm of the bone screw, an outer diameter 3.5mm-6mm, an inner diameter 2.6mm-3.2mm, a tooth form angle alpha of 1.5-4 degrees and a tooth form angle beta of 30-40 degrees;
(2) preparing an Mg-Zn-Y-Nd magnesium alloy ingot;
(3) preparing a magnesium alloy bar blank;
(4) preparing a magnesium alloy extrusion round bar;
(5) and (3) processing the magnesium alloy extruded round bar material obtained in the step (4) into the magnesium alloy bone screw with the structural parameters in the step (1) by a mechanical numerical control processing method, wherein the magnesium alloy bone screw has the extraction force of 98N-110N, the bending load of 230N-260N and the torsion force of 520 & ltn & gt mm.
Preferably, in step (1), the bone screw structure parameters are preferably 1.45mm of screw pitch, 6mm of outer diameter, 3.2mm of inner diameter, 2 degrees of tooth form angle alpha and 35 degrees of tooth form angle beta.
Preferably, the specific steps for preparing the Mg-Zn-Y-Nd magnesium alloy ingot in the step (2) are as follows:
1) preparing raw materials according to the chemical components of the Mg-Zn-Y-Nd magnesium alloy;
2) heating 99.98% of high-purity magnesium under the protection of protective gas, after the magnesium is completely melted, sequentially adding Mg-Y intermediate alloy of Mg-25 wt.% Y or Mg-35 wt.% Y, Mg-Nd intermediate alloy of Mg-25 wt.% Nd and 99.98% of high-purity zinc, and stirring after the alloy is completely melted to ensure that the alloy components are uniform;
3) and adding a refining agent for refining after heat preservation, preserving heat again after refining, and then performing semi-continuous casting to prepare the cast ingot.
Preferably, the protective gas is argon or a mixed gas of carbon dioxide and sulfur hexafluoride, and the heat preservation refers to heat preservation at 700-750 ℃ for 20-30 min.
Preferably, the magnesium alloy bar blank prepared in the step (3) comprises the following specific steps: processing the ingot obtained in the step (2) into
Cylinder of (2) then sandAnd (3) polishing the paper, removing oxides and oil stains on the surface, and performing reciprocating extrusion processing for four times to prepare the magnesium alloy bar blank.
Preferably, the reciprocating extrusion process parameters are specifically as follows: the diameters of the two extrusion cylinders A, B are 30mm, the lengths are 50mm-60mm, and the diameters of necking areas are 16mm-20 mm; the lubricant of the reciprocating extrusion die adopts graphite emulsion; preheating the blank and the die at 503K-573K; when in reciprocating extrusion, the extrusion temperature is 623K-693K, the extrusion rate is 2mm/s-8mm/s, and the extrusion force is 20MPa-60 MPa.
Preferably, the specific steps for preparing the magnesium alloy extruded round bar material in the step (4) are as follows: and (3) forward extruding and heat treating the magnesium alloy rod blank obtained in the step (3) to obtain a magnesium alloy extruded rod bar with a certain size, wherein the forward extruding process comprises the following steps: the extrusion temperature is 623K-683K, the extrusion rate is 2mm/s-8mm/s, and the heat treatment process parameters are as follows: 513K to 583K, keeping the temperature for 15min to 45min, and then rapidly cooling the extruded bar by water.
Preferably, the magnesium alloy extruded round bar prepared in the step (4) has yield strength of 170MPa-210MPa, tensile strength of 260MPa-330MPa and elongation of 15% -20%.
The raw material proportion of the Mg-Zn-Y-Nd magnesium alloy is common proportion, and specifically can be 1-3% of Zn, 0.23-0.69% of Y, 0.5-1% of Nd and the balance of Mg.
The bone screw structure parameters in the step (1) are preferably determined by the following method:
(1) selecting Mg-Zn-Y-Nd magnesium alloy, and referring to the medical industry standard of titanium alloy and stainless steel bone joint implant, determining the initial structure parameters of the magnesium alloy bone screw including a screw cap and a thread structure, wherein the initial structure parameters of the thread are that the pitch is 1.0mm and more than P and less than 2.0mm, the inner diameter is 2.0mm and more than d2 and less than 3.5mm, the tooth form angle is 1 degree and more than alpha and less than 6 degrees, and the angle is 20 degrees and more than beta and less than 50 degrees; establishing a finite element structure model of the magnesium alloy bone screw by using a finite element numerical optimization method;
(2) optimizing a thread structure: according to the initial thread structure parameters in the step (1), performing simulation operation by adopting a finite element numerical optimization method, performing parameter optimization of a single-factor thread pitch, an inner diameter and a tooth form angle structure, performing comparative analysis on the thread shape, optimizing whether the mechanical property of the hollow structure bone screw is optimized, and performing an orthogonal test to determine the influence sequence of the thread pitch, the inner diameter and the tooth form angle size parameters on the mechanical property of the magnesium alloy bone screw so as to obtain the bone screw structure size with optimal performance requirements, wherein the bone screw structure size comprises the bone screw thread pitch P1.3mm-1.7mm, the outer diameter 3.5mm-6mm, the inner diameter 2.6mm-3.2mm, the tooth form angle alpha is 1.5-4 degrees, and the beta is 30-40 degrees; the extraction force is 98N-110N, the bending load is 240N-260N, and the torsion force is 540-;
(3) determining the structures of the screw cap and the screw tail to obtain the structural parameters of the magnesium alloy bone screw structure which is finally optimized;
during optimization, a bone screw three-dimensional structure model is established by UG software and stored in a prt format, ANSYS is introduced, the bone screw is endowed with Mg-Zn-Y-Nd alloy, a Meshing module in a Workbench platform is used for grid division, nodes or contact units are connected into units, acting force of the model is transmitted by each node, and the grid is a set of the nodes and the units. The grid is locally refined by dimensional control for the threaded portion.
(1) A three-point bending model was used. The actual loading section of the three-point bending experiment is the working length part, so the main thread part of the nail body is intercepted by the model of finite element analysis, simulation is carried out on the uniform straight part, the three-point bending model adopts ten-node tetrahedral units to carry out grid division, 171131 nodes are totally, 111641 units are adopted, the average torsion degree of the grid is 0.2538, and the requirement of the conventional analysis of the finite element is met.
(2) And (4) twisting the analysis model. Referring to the medical industry standard of YY0018-2008 metal bone screw for bone joint implant, 5 complete threads are exposed from the calculation of the threads close to the head of the screw, and considering that the main stress of the bone screw is concentrated at the first threads connected with the screw cap and the screw body in the screwing process, the tail of the screw has little influence on the finite element analysis result, so that the rear threads and the tail of the screw are cut off by all torsion analysis models, the number of calculated grids is reduced, and the time for simulation calculation analysis is shortened.
(3) The analytical model was pulled axially.
According to the anti-pull-out test, the use of standard polyurethane rigid foam as standard material test orthopedic equipment and instruments is referred to in ASTM F1839-2008, 6mm long cubic test blocks are established for pull-out models, high-density foam in the literature is selected as the material, the density is 0.32g cm < -3 >, the Poisson ratio is 0.2, the elastic modulus is 267MPa, and the yield stress is 5.9 MPa; the model is calculated by a structural statics analysis module by performing Boolean difference calculation on the magnesium alloy bone screw and the high-density foam test block.
After the technical scheme is adopted, the invention at least has the following beneficial effects:
the magnesium alloy bone screw has less research on the structural parameters, and the invention has the advantages of innovation and obvious effects: the main bearing function of the bone screw structure is a thread part, and the obtained bone screw structure improves the mechanical bearing capacity and reduces the stress concentration degree compared with the bone screw structure before optimization by adopting a structural parameter optimization technology; establishing an integral structural parameter system of the magnesium alloy bone screw, and providing data reference for further structural design, application and clinic; based on the simulation analysis of the three-point bending performance, the torsion performance and the axial extraction performance of the magnesium alloy bone screw, the screw thread structure characteristics and the size parameters of the bone screw are optimized, and the comprehensive mechanical bearing capacity of the bone screw is improved.
The blank of the magnesium alloy bone screw is subjected to optimized reciprocating extrusion, forward extrusion processing and heat treatment to obtain a fine and uniform fine grain structure, and has excellent toughness and uniform degradation performance. And then mechanically and precisely processed into the magnesium alloy bone screw which meets the clinical application.
Drawings
The invention is further described with reference to the following figures and detailed description.
Fig. 1 shows specific dimensional parameters of the bone screw. (a) A nail cap; (b) punching in the nail groove; (c) thread parameters;
FIG. 2 is a schematic diagram of the overall size of an optimized magnesium alloy bone screw
FIG. 3 magnesium alloy bone screw
Detailed Description
The technical solutions in the embodiments of the present invention will be described in detail below, and it should be apparent that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive work, based on the embodiments of the present invention, belong to the scope of the present invention.
Example 1
Selecting Mg-Zn-Y-Nd magnesium alloy as a raw material, and determining structural parameters of the bone screw by adopting the optimization method, wherein the structural parameters comprise a screw thread pitch P1.3mm-1.7mm of the bone screw, an outer diameter P3.5 mm-6mm, an inner diameter 2.6mm-3.2mm, a tooth form angle alpha of 1.5-4 degrees and a tooth form angle beta of 30-40 degrees; on the basis of the optimal structure parameters obtained by optimization: the thread pitch is 1.45mm, the outer diameter is 6mm, the inner diameter is 3.2mm, the tooth form angle alpha is 2 degrees, and the tooth form angle beta is 35 degrees;
(2) preparing an Mg-Zn-Y-Nd magnesium alloy ingot;
(3) preparing a magnesium alloy bar blank;
(4) preparing a magnesium alloy extrusion round bar;
(5) and (3) processing the magnesium alloy extruded round bar material obtained in the step (4) into a magnesium alloy bone screw with the structural parameters in the step (1) by a mechanical numerical control processing method, wherein the magnesium alloy bone screw has the extraction force of 102N, the bending load of 242N and the torsion force of 540 N.mm. The optimized mechanical properties are shown in tables 1-2. The bending load of the optimized common bone screw is improved by 83.5 percent compared with that of the common bone screw before optimization; the torque is improved by 24.2%.
TABLE 1 optimized front and rear screw Loading bending loads corresponding to 0.25mm
TABLE 2 simulation of front and rear bone screws optimized and torque values corresponding to experimental 2 ° torsion angles
Claims (9)
1. A preparation method of a bone screw suitable for biological magnesium alloy is characterized by comprising the following steps:
(1) selecting Mg-Zn-Y-Nd magnesium alloy as a raw material, and determining structural parameters of the bone screw, wherein the structural parameters comprise a screw thread pitch P1.3mm-1.7mm of the bone screw, an outer diameter of 3.5mm-6mm, an inner diameter of 2.6mm-3.2mm, a tooth form angle alpha of 1.5-4 degrees and a tooth form angle beta of 30-40 degrees;
(2) preparing an Mg-Zn-Y-Nd magnesium alloy ingot;
(3) preparing a magnesium alloy bar blank;
(4) preparing a magnesium alloy extrusion round bar;
(5) and (3) processing the magnesium alloy extruded round bar material obtained in the step (4) into the magnesium alloy bone screw with the structural parameters in the step (1) by a mechanical numerical control processing method, wherein the magnesium alloy bone screw has the extraction force of 98N-110N, the bending load of 230N-260N and the torsion force of 520 & ltn & gt mm.
2. The method for preparing a bone screw according to claim 1, wherein: in the step (1), the structural parameters of the bone screw are preferably 1.45mm in thread pitch, 6mm in outer diameter, 3.2mm in inner diameter, 2 degrees in tooth form angle alpha and 35 degrees in tooth form angle beta.
3. The method for preparing a bone screw according to claim 1, wherein: the specific steps for preparing the Mg-Zn-Y-Nd magnesium alloy ingot in the step (2) are as follows:
1) preparing raw materials according to the chemical components of the Mg-Zn-Y-Nd magnesium alloy;
2) heating 99.98% of high-purity magnesium under the protection of protective gas, after the magnesium is completely melted, sequentially adding Mg-Y intermediate alloy of Mg-25 wt.% Y or Mg-35 wt.% Y, Mg-Nd intermediate alloy of Mg-25 wt.% Nd and 99.98% of high-purity zinc, and stirring after the alloy is completely melted to ensure that the alloy components are uniform;
3) and adding a refining agent for refining after heat preservation, preserving heat again after refining, and then performing semi-continuous casting to prepare the cast ingot.
4. The method for preparing a bone screw according to claim 3, wherein: the protective gas is argon or a mixed gas of carbon dioxide and sulfur hexafluoride, and the heat preservation refers to heat preservation at 700-750 ℃ for 20-30 min.
5. The method for preparing a bone screw according to claim 1, wherein: the magnesium alloy bar blank prepared in the step (3) comprises the following specific steps: processing the ingot obtained in the step (2) into
And then, polishing by using sand paper, removing surface oxides and oil stains, and performing reciprocating extrusion processing for four times to prepare the magnesium alloy bar blank.
6. The method for preparing a bone screw according to claim 5, wherein: the reciprocating extrusion process parameters are as follows: the diameters of the two extrusion cylinders A, B are 30mm, the lengths are 50mm-60mm, and the diameters of necking areas are 16mm-20 mm; the lubricant of the reciprocating extrusion die adopts graphite emulsion; preheating the blank and the die at 503K-573K; when in reciprocating extrusion, the extrusion temperature is 623K-693K, the extrusion rate is 2mm/s-8mm/s, and the extrusion force is 20MPa-60 MPa.
7. The method for preparing a bone screw according to claim 1, wherein: the specific steps for preparing the magnesium alloy extruded round bar in the step (4) are as follows: and (3) forward extruding and heat treating the magnesium alloy rod blank obtained in the step (3) to obtain a magnesium alloy extruded rod bar with a certain size, wherein the forward extruding process comprises the following steps: the extrusion temperature is 623K-683K, the extrusion rate is 2mm/s-8mm/s, and the heat treatment process parameters are as follows: 513K to 583K, keeping the temperature for 15min to 45min, and then rapidly cooling the extruded bar by water.
8. The method for preparing a bone screw according to claim 1, wherein: the magnesium alloy extruded round bar prepared in the step (4) has yield strength of 170MPa-210MPa, tensile strength of 260MPa-330MPa and elongation of 15% -20%.
9. A bone screw suitable for use in biological magnesium alloys, prepared by the method of any one of claims 1 to 8.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116616883A (en) * | 2023-07-21 | 2023-08-22 | 苏州奥芮济医疗科技有限公司 | Pure magnesium metal bone screw and processing technology thereof |
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