CN111388764A

CN111388764A - Degradable metal anastomosis nail and preparation method thereof

Info

Publication number: CN111388764A
Application number: CN202010262841.5A
Authority: CN
Inventors: 杨静馨; 成秉禄; 马永新; 徐平国; 王训伟
Original assignee: Beijing Union University
Current assignee: Beijing Union University
Priority date: 2020-04-03
Filing date: 2020-04-03
Publication date: 2020-07-10
Anticipated expiration: 2040-04-03
Also published as: CN111388764B

Abstract

A degradable metal anastomosis nail and a preparation method thereof belong to the technical field of medical appliances. The nail comprises a nail body which is formed by processing medical degradable zinc alloy wires and a degradable organic polymer surface layer which is attached to the surface of the nail body. The staple body is staple-like. The degradable anastomotic nail can be naturally degraded in a living body, and can be degraded in the body within a certain time after reaching the medical effect.

Description

Degradable metal anastomosis nail and preparation method thereof

Technical Field

The invention relates to the technical field of design and production of medical instruments, in particular to an anastomosis nail which is clinically used for postoperative repair and reconstruction and has excellent biocompatibility, proper biomechanical property and biodegradability and a preparation method thereof.

Background

The invention and application of the suture-free surgical technique are great progress and development in the surgical field, and the suture-free surgical technique is simple and rapid to operate, shortens the operation time, is easy to complete the suture and anastomosis of narrow operation fields, deep parts and difficult manual operation, enlarges the operation range, reduces the operation complications and shortens the hospitalization time. As a result, the use of seamless anastomosis has become increasingly widespread as one of the most successful surgical techniques at present. The anastomat is used for replacing the traditional manual suturing method by doctors, adopts a tool for suturing tissues or organs to be anastomosed by the suture nail, and has the advantages of quick suturing, simple and convenient operation, few side effects, few operation complications and the like. In 1908, hungarian made the first stapler in the world, and then continuously improved and gradually popularized in clinic, especially in the last decade, the stapler has become a conventional tool for digestive tract operation in the countries of europe and america, has also become popular in China and has become an indispensable tool for gastrointestinal tract operation. According to market survey aiming at the sales condition of the medical anastomat, the quantity of anastomotic staples is more than 500 ten thousand in every year in China. The stapler is a device used in medicine to replace manual suture, and the main working principle is to use titanium nails to perform anastomosis on tissues, similar to a stapler. According to different application ranges, the surgical stapler mainly comprises a skin stapler, a circular stapler for digestive tracts (esophagus, stomach and intestine and the like), a rectal stapler, a circular hemorrhoid stapler, a circumcision stapler, a blood vessel stapler, a hernia stapler, a lung cutting stapler and the like, but the current traditional stapler staples are made of titanium alloy or tantalum metal with excellent chemical stability, and the staples exist in a patient body for a long time after operation, so that part of patients have foreign body sensation for a long time, and can also cause artifacts and local soft tissue injury (nuclear magnetism can cause metal heating) at the positions of the staples in the body when receiving medical examination such as nuclear magnetic resonance and the like in the future, thereby affecting the examination effect and accuracy, particularly possibly causing tissue hyperplasia at the suture positions, postoperative cavity stenosis and the like. The degradable metal nail is suitable for a tubular anastomat and an anorectal anastomat, is mainly used for anastomosis of various cavities and tracts, is disposable, and has the working principle that two rows of annularly and crossly arranged staples which are impacted into cavity and tract tissues can sew the two layers of cavity and tract tissues together, and the built-in annular knife cuts off redundant cavity and tract tissues at the same time, so that a circular anastomosis opening is formed, and the cavity and tract anastomosis is completed. The tubular anastomat is mainly used for the operations of digestive tract reconstruction under open and endoscopic surgery, peritomy of mucous membrane on hemorrhoids and the like in clinic, and has the typical advantages that the tubular anastomat is used for the anastomosis of aorta and the implantation of artificial blood vessels in foreign countries: small wound, less time consumption, low incidence rate of postoperative anastomotic fistula, anastomotic hemorrhage, anastomotic stenosis and the like.

Therefore, the material selected not only requires simple operation and less complications, but also requires repeated shaping, provides stability of the suture, and is absorbed by the human body after the completion of the operation. To date, there is no ideal prosthetic material that has excellent mechanical properties and biological compatibility, can induce soft tissue healing, and can degrade or be absorbed by itself completely to achieve physiological healing. The currently applied staple materials mainly comprise two types, namely non-degradable metal and degradable high molecular polymer. The common metal is tantalum and titanium alloy plate or stainless steel, which is convenient for molding, but as a permanent implant, the long-term physical stimulation and the long-term foreign body stimulation cause complications and local chronic inflammatory reaction. While these metal staples are temporarily satisfying clinical needs at the present stage, there has been a trend in the long term to develop biodegradable staples with higher biocompatibility. Although the degradable high polymer material can be used as a degradable anastomosis nail for repair, the mechanical property of the degradable high polymer material is relatively poor, and the acidic degradation product is easy to cause acute or chronic inflammation and the like. The development of biodegradable metal staples is therefore one of the important directions in which staple research is becoming a present stage. In addition, the degradable metal nail can be coated by an ion beam assisted deposition method, an electrodeposition method, chemical vapor deposition, arc deposition, ion implantation, a thermal spraying method and a laser cladding method, has compact structure and is firmly combined with a metal implant, so that the degradation rate of the degradable metal is controlled on one hand, and the implant has excellent bioactivity and biocompatibility on the other hand. The degradable anastomosis nail for the anastomat is convenient to use, safe and effective.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention adopts the technical scheme that the degradable metal anastomosis nail and the preparation method thereof.

Degradable anastomotic nail that anastomat used, its characterized in that comprises staple body (1) that forms, degradable organic polymer superficial layer (2) attached to zinc alloy suturing staple body surface by processing of medical degradable zinc alloy silk material. The nail of sewing up the nail body is like the staple form, and nail body structure: the middle long section round wire A (3), both ends have a short section round wire B (4) perpendicular to long section round wire A separately, short section round wire B and long section round wire A are the integrated structure namely it is the same zinc alloy round wire to adopt, two short section round wires B locate at long section round wire A same side, and in long section round wire A coplanar, this level is called C; the tail end of the short section round wire B, namely the end which is not connected with the long section round wire, is provided with a wedge-shaped structure, the wedge-shaped structure is formed by cutting the short section round wire B from the outer side by adopting a plane D vertical to a plane C, and preferably, the included angle between the plane D and the short section round wire B is an acute angle, preferably 45-60 degrees; the axial length of the long section of round wire A is the length of the staple body, and the axial length of the short section of round wire B is the height of the staple body; the diameters of the long section round wire A and the short section round wire B can be designed according to requirements. The thickness of the degradable polymer surface layer is 5-30 microns. The length of the stitching nail is 63-103mm, and the allowable error is +/-2 mm; the height of the staple is 3.8-4.5mm, and the allowable error is +/-0.2 mm.

The degradable zinc alloy comprises the components of zinc with the content of more than or equal to 95 percent, and also can contain one or more of Mg, Sr, L i, Mn, Fe, Ca, Cu and Ag, wherein the total weight content of the elements of calcium, copper and silver is less than or equal to 3 percent, the total weight content of the elements of Mg, Ca, Sr, L i, Mn and Fe is less than or equal to 1 percent, and other impurities or other elements which are 0 or indispensable are contained.

The degradable high polymer material is selected from chitosan and polylactic acid; chitosan is a natural high molecular polymer with viscosity, good biocompatibility, biodegradability, film-forming property and drug-carrying property, and is often used as a growth factor carrier and a scaffold material to be applied to bone tissue engineering.

The preparation of the degradable anastomotic nail used for the anastomat comprises the following steps:

(1) the staple body is prepared by smelting and casting as-cast alloy with high-purity zinc (99.9 wt%) and intermediate alloy in a resistance furnace filled with protective gas; preparing raw materials according to the designed component proportion; and after the raw materials are completely melted, fully stirring and standing, and casting the melted materials onto a mold, wherein protection gas needs to be introduced in the process.

(2) Obtaining zinc alloy wire

Carrying out heat treatment on the zinc alloy ingot casting material obtained in the step (1), and drawing the zinc alloy ingot casting material into a required wire material; in the initial stage of the successive drawing process, the section is annealed at 500 ℃, so that the corrosion resistance of the zinc alloy is improved from the inside; bending the wire material according to the design size to prepare a suture nail;

(3) performing surface alkali heat treatment on the formed zinc alloy staple:

corroding the suture nail obtained in the step (2) by adopting acid (1 wt% nitric acid solution), cleaning and increasing the surface unevenness; preparing 1M NaOH aqueous solution in advance, putting the sample subjected to acid etching into a small reaction kettle, and adding the prepared alkaline solution to completely submerge the sample; sealing the reaction kettle, horizontally putting the reaction kettle into an oven, and heating the reaction kettle at the temperature of 120-150 ℃ for 5-8 h; slowly cooling along with the furnace, taking out a sample, ultrasonically cleaning the sample by using deionized water, and drying the sample in a drying oven to obtain a treated zinc alloy suture nail;

(4) forming a degradable polymeric coating

Preparing a degradable high polymer material into a solution, sucking the solution by using an injector at room temperature, injecting the solution into a groove mold with the same structure as the stitching nail, slightly placing the stitching nail in the step (3) in the center of the mold, slowly injecting the solution into the mold, quickly transferring the mold into a refrigerator, pre-freezing the mold, placing the mold into a freeze-drying machine, and taking out the material after drying and forming; or directly coating the degradable high polymer material solution on the seam nail and then drying.

Further preferred is the heat treatment described in the step (2): the zinc alloy ingot requires a further heat treatment process of hot rolling and hot extrusion in order to improve mechanical properties. Hot rolling, cutting the as-cast zinc alloy ingot into thick plates, preheating to 250 ℃, and rolling thinner plates after 3 hours; the thickness of the steel plate is reduced by heating the steel plate to 0.2mm in a single pass, and the steel plate is reheated to 250 ℃ between each pass and is kept warm for 10 minutes; hot extrusion, which is first cut into larger diameter cylinders, preheated to 210 ℃ for 3 hours, and then extruded into relatively smaller diameter cylinders.

The anastomat is made of degradable anastomosis nails, the entity is made of degradable zinc alloy wires, and the surface layer is made of a degradable high-molecular surface layer. The entity and surface layer materials are also degradable in vivo and have excellent biocompatibility. Compared with the prior art, the invention has the beneficial effects that:

(1) the degradable anastomotic nail can be naturally degraded in a living body, can be degraded in the body within a certain time after reaching the medical effect, and avoids the physiological and mental burden of patients caused by foreign matters in the body.

(2) The degradable anastomosis nail in the organism avoids using Al and rare earth metal in the component design, and ensures the biological safety of the material from the material selection.

(3) The degradable anastomosis nail in the organism has high corrosion resistance, good plastic deformation capability and good biocompatibility, meets the requirement of the implanted material on the corrosion rate, has no obvious cytotoxicity, has good histocompatibility, and can meet the requirement of the implanted material on the biocompatibility.

(4) The degradable anastomosis nail in the organism adopts polylactic acid high molecular polymer, on one hand, the mechanical property of the anastomosis nail can be adjusted, so that the mechanical property can meet the function of anastomosis maintenance as much as possible, and on the other hand, the corrosion resistance of the magnesium alloy bracket can be improved to a certain extent.

(5) In the process of heat treatment, after the section is extruded and formed, the section is annealed at 500 ℃, so that the corrosion resistance of the zinc alloy is improved from the inside; the subsequent alkali heat treatment improves the corrosion resistance of the zinc alloy from the outside.

Drawings

FIG. 1 is a 3D modeling of stapler staples;

FIG. 2 is a finished stapler nail;

FIG. 3 is a metallographic photograph;

FIG. 4XRD diffractogram;

FIG. 5 is a graph of the mass loss rate of zinc-magnesium alloy in normal saline;

FIG. 6 is a line graph showing the pH value of physiological saline of a zinc-magnesium alloy.

Detailed Description

The present invention will be further described with reference to the following examples, which are illustrative only and not intended to be limiting, and the scope of the present invention is not limited thereby.

Example 1

The anastomat is composed of a stitching nail body formed by processing medical degradable zinc alloy wires and a degradable high-molecular surface layer attached to the surfaces of the zinc alloy wires and used for hole sealing treatment. The entity is characterized by a staple-like shape. The basic size of the suture length of the anastomat using the degradable staples is 63-103mm, and the allowable error is +/-2 mm. The basic size of the height of the degradable staple used by the anastomat is 3.8-4.5mm, and the allowable error is +/-0.2 mm. As shown in fig. 2.

The anastomat is prepared by adopting degradable zinc alloy wires as degradable anastomosis nail entities and adopting a degradable polymer surface layer as a surface layer. Making it also degradable in vivo and having excellent biocompatibility. Is suitable for anastomotic suture of gastrointestinal tract and esophagus in human digestive tract operation.

The preparation method comprises the following steps:

(1) preparing a zinc-calcium alloy:

the experiments used master alloys of as-cast alloy raw materials including high purity zinc (99.9 wt%) and magnesium or/and magnesium oxide. Smelting and casting in a resistance furnace filled with mixed protective gas; preparing raw materials according to the proportion of Zn-1% Mg (or adopting calcium oxide intermediate alloy corresponding to Zn-1% Ca); and (3) completely melting the raw materials, fully stirring and standing. The molten material is cast onto the mold (this process requires venting of the protective gas).

(2) Obtaining a zinc alloy wire

The method comprises the steps of carrying out heat treatment on a zinc alloy ingot casting material (for a rolled sample, the as-cast zinc alloy ingot is cut into thick plates, preheated to 250 ℃, and then rolled into a thinner plate after 3 hours, wherein the thickness of the steel plate is reduced by heating the steel plate in a single pass by 0.2mm, and the steel plate is reheated to 250 ℃ between each pass and is kept warm for 10 minutes. At the beginning of the successive drawing process, the profile was completely annealed at 500 ℃. The length of the anastomat is 63mm in basic size and the height of the anastomat is 3.8mm in basic size. And bending the wire material into a staple shape according to the design size.

(3) Performing surface alkali heat treatment on the formed zinc alloy anastomosis nail:

preparing a low-concentration 1M NaOH alkaline solution in advance, putting a sample (1 wt% nitric acid solution) subjected to acid etching in advance into a 25ml small-sized reaction kettle, and adding the prepared alkaline solution to completely submerge the sample. And (4) sealing the reaction kettle, horizontally placing the reaction kettle into an oven, and heating the reaction kettle for 6 hours at the temperature of 140 ℃. Slowly cooling along with the furnace, taking out a sample, ultrasonically cleaning the sample with deionized water for three times, and drying the sample in a drying oven at 37 ℃ for 15min to obtain the treated zinc alloy anastomosis nail.

(4) Forming a degradable polymeric coating

Preparing chitosan into a solution, sucking the solution by using an injector at room temperature, injecting the solution into a mold, slightly placing a zinc alloy wire in the center of the mold, slowly injecting the solution into the mold, quickly transferring the mold into a refrigerator with the temperature of-20 ℃, pre-freezing for 12 hours, then placing the mold into a freeze dryer for 24 hours, and taking out the material after drying and forming. The degradable high molecular polymer coating with the thickness of about 10 microns is formed.

(5) Use of intestinal anastomoses:

the proximal intestinal canal of the anastomotic stoma is subjected to purse-string suture, the nail seat is placed and tightened, the anastomat is inserted into the distal intestinal cavity, penetrates out of the central puncture outfit of the anastomat and is connected with the central rod of the nail abutting seat of the proximal anastomat, the intestinal wall of the distal intestinal canal and the proximal intestinal canal is gradually closed by rotating the knob, and the distance between the nail abutting seat and the base of the anastomat is adjusted according to the thickness of the intestinal wall or the rotation of the hand is limited to be tight. Opening the insurance; the closing anastomosis wrench is pinched with force, and the cutting anastomosis is finished by hearing the 'clicking' sound. The stapler is unscrewed and gently pulled out from the distal end, and the distal-proximal end intestinal tube excision circle is checked for completeness.

The following are metallographic photographs, hardness values, XRD results and in-vitro simulated environment degradation experimental data of the zinc-magnesium alloy:

(1) metallography

Referring to FIG. 3, it can be seen from the structural morphology of the obtained zinc-magnesium binary alloy that the structure of the zinc alloy is refined with the addition of magnesium, and the lighter part in the figure is α -Zn.

(2) Hardness of

TABLE 1 hardness of the zinc-magnesium alloy obtained (test using a sample in the form of a cylinder having an axial length of 25mm and a diameter of 30mm, L1 and L2 being distances axially from both end faces, D1 and D2 being distances radially from the periphery, respectively, and hardness being average hardness)

According to the metallographic results, the addition of magnesium in the zinc-magnesium alloy refines the crystal grains, increases the grain boundary area of the alloy, increases the resistance of dislocation slip, and macroscopically shows that the hardness of the alloy is increased. According to the international hardness comparison table, the Vickers hardness of magnesium is between 40 and 60HV, while the Vickers hardness of iron is about 315HV, and according to experiments, the hardness of the zinc-magnesium alloy is in front of that of magnesium and iron, the alloy has good plastic toughness capacity, and in addition, a plurality of researchers find that the hardness and the plasticity of the cast zinc-magnesium alloy can not achieve the effect of supporting the degradable biological material on the human body, and generally adopt certain processing means such as processing hardening and the like to change the mechanical property of the zinc-magnesium alloy, so that the zinc-magnesium alloy achieves the effect of supporting the zinc-magnesium alloy on the human body.

(3) XRD diffractogram

FIG. 4 shows the X-ray diffraction test results of the obtained zinc-magnesium binary alloy, which shows that the alloy contains pure zinc, and magnesium mainly exists in a compound state in the alloy, and the compound in the alloy is mainly MgZn according to the inference₂And MgZn11, according to a binary phase diagram of the zinc-magnesium alloy, the zinc-magnesium alloy firstly precipitates α -Zn phase during equilibrium crystallization and then precipitates a zinc-magnesium eutectic structure along grain boundaries, wherein the eutectic structure is α -Zn and Mg2Zn 11.

(4) Simulating corrosion speed of human body environment

And (3) analyzing a mass loss rate graph of the obtained zinc-magnesium alloy in a normal saline solution.

As shown in FIG. 5, the mass of the zinc-magnesium alloy before degradation in physiological saline is about 0.11 g. The mass loss rate of the material has an upward trend, the degradation rate can be seen to be basically kept in a uniform degradation mode through the height difference of adjacent reduced mass average values, the image is basically proportional to a proportional function, and the situation that a plurality of problems are caused by unstable degradation rate when the material is implanted into a human body can be inferred.

The pH values of the samples of the zinc-magnesium alloy on the 1 st, 3 th, 5 th and 7 th days in the physiological saline are averaged to be 7.19,8.28, 8.62 and 9.39 respectively, and then a broken line statistical graph is drawn, as shown in a broken line graph of the pH value of the physiological saline in FIG. 6, the pH value is shown to be in a rising trend along with the time, the pH value in the physiological saline is shown to be slowly raised, and the pH value of the initial solution is changed most compared with the pH value on the seventh day. Wherein, the alkalinity of the solution indicates that the solution is alkaline due to the rich hydroxide radical, and at the beginning of the experiment, the generation of gas on the surface of the stone block can be observed, so that the generation of hydrogen can be inferred.

After the surface adopts the degradable high molecular material, on one hand, the degradation rate of the degradable metal is controlled, and on the other hand, the implant has excellent bioactivity and biocompatibility.

(5) Other studies on biocompatibility include blood compatibility, cytotoxicity, in vivo biocompatibility, etc.

The results show that the hemolysis rates of the Zn-1Mg, Zn-1Ca and Zn-1Sr (i.e., Zn-1Sr alloy can also be used) alloys are all very low (< 0.2%) and much lower than the hemolysis safety value of 5%. The observation of a scanning electron microscope on the platelets adhered to the surface of the material shows that all the platelets are spherical and do not spread out pseudopodically, which indicates that the materials have good blood compatibility.

The cell survival rate of all zinc alloy leaching liquor is higher than that of a pure Zn control group. For Vascular Smooth Muscle Cells (VSMC), the addition of Mg, Ca and Sr did not act to promote VSMC cell proliferation compared to the negative control. In the case of human osteosarcoma cells (MG63), the addition of the alloying element promotes the proliferation of the cells.

The mice are used as animal models to evaluate the biosafety and degradation behavior of different binary rolling Zn-1Mg, Zn-1Ca and Zn-1Sr alloys in vivo. The rolled Zn-1Mg, Zn-1Ca and Zn-1Sr alloy still keeps complete appearance after being implanted into a mouse body for 8 weeks, which shows that the rolled binary Zn-1Mg, Zn-1Ca and Zn-1Sr alloy can still provide enough mechanical support after being implanted into the mouse body for a certain time, and the implant can not be disintegrated due to too high corrosion rate. Thereby effectively avoiding the problem of implant failure caused by premature loss of implant strength. Meanwhile, the new bone generation thickness around the implant is observed to be larger than that of the control group, which shows that the binary zinc alloy can promote bone healing and new bone formation, thereby shortening the fracture repair cycle. The results of immunohistochemical staining also show that the intramedullary needle implant made of rolled Zn-1Mg, Zn-1Ca and Zn-1Sr alloys can obviously promote the formation of new bones, the thickness of the new bones is far greater than that of a control group, and the new bone formation capability of the Zn-1Sr alloy is highest.

Claims

1. The utility model provides a degradable identical nail that anastomat used which characterized in that, sews nail body (1) by processing of medical degradable zinc alloy silk material, adheres to degradable organic polymer superficial layer (2) on zinc alloy sews nail body surface and constitutes.

2. The degradable staple for use in a stapler according to claim 1, wherein the thickness of the surface layer of degradable polymer is 5 to 30 μm.

3. The degradable staple used in the stapler according to claim 1, wherein the staple body is staple-like, and the staple body structure is: the middle long section round wire A (3), both ends have a short section round wire B (4) perpendicular to long section round wire A separately, short section round wire B and long section round wire A are the integrated structure namely it is the same zinc alloy round wire to adopt, two short section round wires B locate at long section round wire A same side, and in long section round wire A coplanar, this level is called C; the tail end of the short section round wire B, namely the end which is not connected with the long section round wire, is provided with a wedge-shaped structure, the wedge-shaped structure is formed by cutting the short section round wire B from the outer side by adopting a plane D vertical to a plane C, and preferably, the included angle between the plane D and the short section round wire B is an acute angle, preferably 45-60 degrees; the axial length of the long section of round wire A is the length of the stitching nail body, and the axial length of the short section of round wire B is the height of the stitching nail body.

4. The degradable staple for use in a stapler according to claim 1, wherein the staple length is 63-103mm with a tolerance of ± 2 mm; the height of the staple is 3.8-4.5mm, and the allowable error is +/-0.2 mm.

5. The degradable anastomosis nail for the anastomat according to claim 1, wherein the content of alloy elements in the degradable zinc alloy is within the biomedical requirement range, so that degradation products of the alloy elements do not cause tissue toxicity reaction, and the degradable zinc alloy is binary or ternary zinc alloy selected from pure zinc series or zinc-magnesium series, zinc-calcium series, zinc-lithium series, zinc-strontium series, zinc-manganese series, zinc-iron series, zinc-copper series and zinc-silver series, wherein the degradable zinc alloy comprises the following components, namely the zinc content is more than or equal to 95%, and simultaneously one or more of Mg, Sr, L i, Mn, Fe, Ca, Cu and Ag elements can be contained, wherein the total weight content of the calcium, copper and silver elements is less than or equal to 3%, the total weight content of the Mg, Ca, Sr, L i, Mn and Fe is less than or equal to 1%, and other elements are 0 or indispensable impurities or other elements.

6. The degradable staple for use in a stapler according to claim 1, wherein the degradable polymer material is selected from chitosan and polylactic acid.

7. The method for preparing a degradable staple for a stapler according to any one of claims 1-6, comprising the steps of:

(1) the staple body is prepared by smelting and casting as-cast alloy with high-purity zinc (99.9 wt%) and intermediate alloy in a resistance furnace filled with protective gas; preparing raw materials according to the designed component proportion; after the raw materials are completely melted, fully stirring and standing, and casting the melted materials onto a mold, wherein protection gas needs to be introduced in the process;

(2) obtaining zinc alloy wire

(3) performing surface alkali heat treatment on the formed zinc alloy staple:

adopting acid corrosion to the suture nail obtained in the step (2), cleaning, and increasing the surface unevenness; preparing 1M NaOH aqueous solution in advance, putting the sample subjected to acid etching into a small reaction kettle, and adding the prepared alkaline solution to completely submerge the sample; sealing the reaction kettle, horizontally putting the reaction kettle into an oven, and heating the reaction kettle at the temperature of 120-150 ℃ for 5-8 h; slowly cooling along with the furnace, taking out a sample, ultrasonically cleaning the sample by using deionized water, and drying the sample in a drying oven to obtain a treated zinc alloy suture nail;

(4) forming a degradable polymeric coating