Intramedullary nail and manufacturing method thereof

Abstract

The present invention provides an intramedullary nail and a method for manufacturing the intramedullary nail. The intramedullary nail is made of silk fibroin and includes a skeleton and multiple fiber layers formed on the skeleton. Each fiber layer is fixed under pressure with a silk fibroin solution. The intramedullary nail and the method for manufacturing the intramedullary nail of the present invention use silk fibroin as a raw material to make the intramedullary nail, so that the intramedullary nail can be self-degraded in the human body, eliminating the process of removing the nail and reducing the harm to the human body. By first forming the skeleton and then forming multiple fiber layers, the intramedullary nail has higher mechanical strength, stronger supporting effect, higher fatigue resistance, and a controllable degradation rate.

Description

Technical Field

[0001] The present invention relates to an intramedullary nail and a method for manufacturing the same. Background Art

[0002] As an internal fixation device for long bone fractures, traditional metal materials (stainless steel, titanium alloy) are difficult to meet the long-term clinical application requirements due to problems such as poor biocompatibility, the need for secondary surgery to remove, and stress shielding. The elastic modulus of metal materials is much higher than that of human bones, resulting in an imbalance in the stress distribution in the bone regeneration area, which may cause inflammatory reactions and osteoporosis.

[0003] Silk fibroin-based materials have become an ideal alternative due to their excellent biocompatibility, degradability, and flexibility. Research shows that silk fibroin materials can promote the growth of bone cells and improve the fracture healing microenvironment, and their flexibility can reduce the stress shielding effect.

[0004] However, existing silk fibroin intramedullary nails have insufficient mechanical properties. Their bending strength is only equivalent to 15% - 30% of the human tibia, unable to meet the load-bearing requirements of large-weight patients. Moreover, the degradation rate of silk fibroin is uncontrollable, and it can only gradually start to degrade some time after fracture recovery. It cannot start to degrade along with the fracture recovery process, nor can it enable the fracture area to be gradually naturally stressed to accelerate fracture recovery.

[0005] In view of this, it is necessary to improve the existing method for manufacturing intramedullary nails to solve the above problems. Summary of the Invention

[0006] The purpose of the present invention is to provide an intramedullary nail and a method for manufacturing the same, so as to solve the problems of insufficient strength and uncontrollable degradation rate of existing silk fibroin.

[0007] To achieve the above purpose, the present invention provides an intramedullary nail made of silk fibroin, which includes a skeleton and multiple fiber layers formed on the skeleton, and each fiber layer is fixed by pressing with silk fibroin solution.

[0008] As a further improvement of the present invention, different drugs are added to each fiber layer of the intramedullary nail.

[0009] As a further improvement of the present invention, the skeleton includes a main body part and multiple branches.

[0010] The present invention also provides a method for manufacturing an intramedullary nail, which includes the following steps:

[0011] S1: Collect human data and design an intramedullary nail;

[0012] S2: Design a skeleton mold and pour silk fibroin solution into the skeleton mold to form a skeleton;

[0013] S3: Spinning silk fibroin on the surface of the framework to form a fiber layer;

[0014] S4: Design an intramedullary nail mold, place the framework with the fiber layer in step S3 into the intramedullary nail mold, and use silk fibroin solution to pour in the intramedullary nail mold to complete the pressure fixation of the fiber layer;

[0015] S5: Repeat steps S3 and S4, spin to form multiple fiber layers, and perform separate pressure fixation on the multiple fiber layers until the production of the intramedullary nail is completed.

[0016] As a further improvement of the present invention, the spinning method in step S3 is the electrospinning method.

[0017] As a further improvement of the present invention, in step S3, the fiber layer is at least divided into a fast degradation layer close to the framework and a slow degradation layer far from the framework. The fiber diameter of the fast degradation layer is smaller than that of the slow degradation layer, and the spinning voltage of the fast degradation layer is lower than that of the slow degradation layer.

[0018] As a further improvement of the present invention, in step S3, the spinning voltage range of the fast degradation layer is 5 - 10 kV, and the spinning voltage range of the slow degradation layer is 15 - 30 kV.

[0019] As a further improvement of the present invention, in step S5, the spinning voltage for weaving the fiber layer in the repeated step S3 gradually increases from the inside to the outside.

[0020] As a further improvement of the present invention, the fiber layer formed in step S3 is added with a drug, and the fiber layer formed in the repeated step S3 in step S5 is added with a different drug.

[0021] As a further improvement of the present invention, in step S4, the silk fibroin solution is added with a drug, and the silk fibroin solution in the repeated step S4 in step S5 is added with a different drug.

[0022] As a further improvement of the present invention, the manufacturing method of the intramedullary nail further includes step S6 after step S5: grinding, polishing, cleaning, and inspecting the manufactured intramedullary nail.

[0023] As a further improvement of the present invention, the manufacturing method of the intramedullary nail further includes step S7: making nail holes.

[0024] The beneficial effects of the present invention are as follows: For the intramedullary nail and the manufacturing method thereof of the present invention, by using silk protein as a raw material to manufacture the intramedullary nail, the intramedullary nail can be self-degraded in the human body, eliminating the process of removing the nail and reducing the harm to the human body; by first forming a skeleton and then forming multiple fiber layers, the intramedullary nail has higher mechanical strength, stronger supporting effect, higher fatigue resistance, and a controllable degradation rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The drawings described herein are used to provide a further understanding of the present application, and constitute a part of the present application. The schematic embodiments and descriptions thereof of the present application are used to explain the present application, and do not constitute an improper limitation to the present application. In the drawings:

[0026] Figure 1 is a schematic structural diagram of the intramedullary nail of the present invention;

[0027] Figure 2 is a schematic structural diagram of the skeleton of the intramedullary nail of the present invention;

[0028] Figure 3 is a schematic diagram of forming a fiber layer on the skeleton of the intramedullary nail of the present invention;

[0029] Figure 4 is a schematic method diagram of step S3 of the manufacturing method of the intramedullary nail of the present invention;

[0030] Figure 5 is a schematic method diagram of step S4 of the manufacturing method of the intramedullary nail of the present invention;

[0031] Figure 6 is a flow chart of the manufacturing method of the intramedullary nail of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0033] In the description of the present invention, it should be noted that the orientation or positional relationship indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0034] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "installation", "connection", and "coupling" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances. In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0035] As Figure 1 shown, the intramedullary nail of the present invention is made of silk fibroin. The intramedullary nail includes a skeleton and multiple fiber layers formed on the skeleton, and each fiber layer is fixed under pressure by a silk fibroin solution.

[0036] Silk fibroin has good compatibility with the human body, so that the intramedullary nail can be degraded in the human body by itself, eliminating the process of removing the nail and reducing the harm to the human body.

[0037] The skeleton includes a main body portion and multiple branches. The lengths of the multiple branches are different and correspond to the thicknesses of different regions of the intramedullary nail. The branches are longer in the thick places and shorter in the thin places. The design and manufacturing process of the intramedullary nail in this embodiment refer to the heart tissue and the tree trunk at the same time, and the manufactured product principle is relatively similar to the human tissue (bones attached with muscles). The skeleton in this embodiment incorporates the bionics principle. In the design, the flexibility and adaptability of the heart tissue, as well as the firmness and growth characteristics of the tree trunk, are fully borrowed, endowing the intramedullary nail with excellent biocompatibility, mechanical properties, and functional adaptability.

[0038] Different drugs are added to each fiber layer of the intramedullary nail. Here, the drug can enhance bone growth as a bone induction unit or can be used as an anti-inflammatory substance to avoid inflammation problems during the fracture repair process. And adding different substances to different layers can deal with different situations, and the drug will be released after dissolving in the specified silk fiber layer, that is, the drug can be released in a controlled manner.

[0039] The intramedullary nail of the present invention has a stronger supporting effect and higher fatigue resistance.

[0040] The intramedullary nail is manufactured by a manufacturing method of an intramedullary nail.

[0041] The manufacturing method of the intramedullary nail includes the following steps:

[0042] S1: Collect human data and design the intramedullary nail;

[0043] S2: Design a skeletal mold, and use silk fibroin solution to pour in the skeletal mold to form a skeleton;

[0044] S3: Use silk fibroin to spin fibers on the surface of the skeleton to form a fiber layer;

[0045] S4: Design an intramedullary nail mold, put the skeleton with a fiber layer in step S3 into the intramedullary nail mold, and use silk fibroin solution to pour in the intramedullary nail mold to complete the pressure fixation of the fiber layer;

[0046] S5: Repeat steps S3 and S4 to spin multiple fiber layers and perform separate pressure fixation on the multiple fiber layers until the production of the intramedullary nail is completed;

[0047] S6: Grind, polish, clean, and inspect the produced intramedullary nail;

[0048] S7: Make nail holes.

[0049] In step S1, the intramedullary nail is made of real human data. Its inclination angle is adjusted by referring to real data, generally between 5 - 10°. It is divided into main locking nail holes and secondary locking nail holes. The main locking nail holes are generally set at the head and have an inclination angle, which plays an anti-rotation role after the locking screw is placed here. The secondary locking nail holes are generally set at the bottom, and the angle is set according to the situation, generally perpendicular to the axis of the intramedullary nail.

[0050] The fiber spinning method in step S3 is the electrospinning method. The manufacturing principle is to control the direction and diameter of the fibers by adjusting the voltage of the electrospinning machine during electrospinning.

[0051] In step S3, the fiber layer is at least divided into a fast-degrading layer close to the skeleton and a slow-degrading layer far from the skeleton. The fiber diameter of the fast-degrading layer is smaller than that of the slow-degrading layer. Among them, the spinning voltage of the fast-degrading layer is lower than that of the slow-degrading layer. The slow-degrading layer has a larger fiber diameter, so it can achieve slow degradation and play a good supporting effect before the fracture site is completely healed.

[0052] In step S3, the spinning voltage range of the fast-degrading layer is 5 - 10 kV, and the spinning voltage range of the slow-degrading layer is 15 - 30 kV.

[0053] Moreover, in step S5, the electrospinning voltage for fabricating the fiber layer in the repeated step S3 gradually increases from the inside to the outside. It should be emphasized that the electrospinning voltages of both the fast-degrading layer and the slow-degrading layer gradually increase from the inside to the outside. First, the internal fast-degrading layer is fabricated. When fabricating, the voltage range of the electrospinning machine is relatively low. For example, first, a layer of fibers is fabricated on the scaffold surface using 5 kV, and then the second layer of fibers is fabricated using 5.5 kV, and so on. The voltage gradient is determined by how many layers of fibers are to be fabricated. The fiber diameter of the fast-degrading layer is smaller, so it can degrade quickly. The fiber diameter of the slow-degrading layer is larger and denser, and the voltage range is 15 - 30 kV.

[0054] It gradually degrades as the fracture heals, and its supporting strength gradually decreases during the recovery process. The fracture area can continuously and gradually increase the bearing force, helping the functional recovery of the fracture site to be more natural. Specifically, the silk fibroin fiber diameter and density on the outside are larger, and it can be determined that degradation gradually begins after the initial fracture recovery. Then, after the thick fibers on the outside are completely degraded, at this time the fracture has basically healed, and the degradation rate of the fine fibers inside is faster, and they can be degraded within a short period of time. And the scaffold will continuously maintain the integral nail supporting strength during the degradation process, avoiding the phenomenon of uneven stress distribution caused by fiber degradation.

[0055] Step S3 is to fabricate silk fibroin fibers with inconsistent arrangement directions in multiple layers, so as to increase the supporting strength and controllable degradation rate. Such an arrangement mimics the arrangement of myocardial fibers in the heart. Because the heart is composed of multiple layers of myocardial fibers with different arrangements, the myocardial fibers arranged in different directions are intertwined with each other, just like constructing an intricate network structure. This structure endows the heart with good stability and makes it not easily deformed in shape. Therefore, by setting step S3, the obtained intramedullary nail has better stability. In addition, the present invention can adjust the fiber direction to enhance the force-bearing situation of the intramedullary nail in different regions. During fabrication, only the voltage of the electrospinning machine needs to be adjusted to change the fiber direction (the voltage can be continuously changed), and the adjustment is more convenient.

[0056] The fiber layer formed in step S3 is added with drugs, and the fiber layer formed in the repeated step S3 in step S5 is added with different drugs. Due to the setting of multiple fiber layers and each fiber layer being independently electrospun, the effect of adding different drugs in different fiber layers can be achieved.

[0057] The purpose of step S4 is to perform pressure fixation. This operation is to press and fix the produced silk fibroin fibers on the scaffold. The specific process is to place the scaffold after electrospinning inside the intramedullary nail mold, and then pour the silk fibroin solution from the main pouring port of the upper mold. The silk fibroin solution will pour into the corresponding intramedullary nail area from the sub-pouring ports of the silk fibroin, and pressure is applied from the main pouring port to enhance the contact between the solutions.

[0058] In addition to adding drugs in step S3, different drugs are added to the silk fibroin solution in the repeated step S4 in step S5. Drugs can be added in two steps or in one step. When adding drugs in step S3, the drugs can be dissolved in the silk fibroin solution and then spun, or the drugs can be sprinkled on the limiting layer after the fiber layer is made, and then poured with the silk fibroin solution to cover the drugs; when adding drugs in step S4, the drugs are directly mixed with the silk fibroin solution and then poured.

[0059] In addition, in this embodiment, multiple fiber layers are provided, which allows this intramedullary nail to carry multiple drugs, can ensure the release of different drugs at different times, and increase the versatility of the intramedullary nail.

[0060] In step S5, after solidification, it is taken out of the mold, and the operations of electrospinning and pressure fixation are repeated until the preliminary production of the intramedullary nail is completed.

[0061] After the preliminary production of the intramedullary nail, that is, when the intramedullary nail has reached the expected diameter, it is necessary to go through step S6 for grinding to eliminate the fine defects, protrusions and unevenness on the surface of the intramedullary nail one by one. The grinding process requires high-precision grinding equipment and delicate sandpaper, following the grinding order from coarse to fine. First, use coarse sandpaper to initially grind off the more obvious rough parts, and then switch to fine sandpaper for fine grinding to make the surface of the intramedullary nail smoother. During grinding, the grinding force and speed should be strictly controlled to avoid deviation of the diameter of the intramedullary nail due to excessive grinding, which affects its fit with the medullary cavity.

[0062] After grinding, a comprehensive cleaning treatment is carried out on the intramedullary nail. Using an ultrasonic cleaner, metal debris, abrasive particles and other impurities remaining on the surface of the nail body during the grinding process are thoroughly removed to ensure that the surface of the intramedullary nail is clean and free of dirt.

[0063] Subsequently, a surface polishing treatment is carried out on the intramedullary nail. Through methods such as electrochemical polishing or mechanical polishing, the surface finish of the intramedullary nail is further improved, and its surface roughness is reduced. This not only helps to reduce the frictional damage to the surrounding tissues after the intramedullary nail is implanted into the human body, but also enhances its corrosion resistance and extends its service life.

[0064] After the polishing is completed, strict quality inspection of the intramedullary nail is also required. Using high-precision measuring instruments, check whether the key dimensions such as its diameter and length meet the standards. Use an electron microscope to observe the surface microstructure and check for defects such as microcracks generated during the grinding or polishing process.

[0065] There are two ways to make the nail holes in step S7. One way is to use a specific rod to fix it on the skeleton before production, and then perform subsequent operations. After the production is completed, remove the rod, and the reserved space is the designated nail hole. If this method is adopted, step S7 is not limited to be executed after step S6.

[0066] Another way is to use a drilling tool to drill holes after the production is completed. It should be noted that when drilling, drills with gradually increasing diameters are used in sequence. First, use a small-diameter drill to drill a positioning hole, and then use drills with increasing diameters in sequence to expand the diameter of the nail hole. This can avoid problems such as nail hole rupture. If this method is adopted, step S7 needs to be executed after step S6.

[0067] For the intramedullary nail and the manufacturing method thereof of the present invention, by using silk fibroin as a raw material to manufacture the intramedullary nail, the intramedullary nail can be degraded automatically in the human body, eliminating the process of removing the nail and reducing the harm to the human body; by first forming a skeleton and then forming multiple fiber layers, the intramedullary nail has higher mechanical strength, stronger supporting effect, higher fatigue resistance, and a controllable degradation rate.

[0068] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0069] The above-described embodiments only represent several implementation manners of the present invention. Their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A manufacturing method of an intramedullary nail, characterized in that: The manufacturing method of the intramedullary nail comprises the following steps: S1: Collect human data and design the intramedullary nail; S2: Design a skeleton mold, and use silk fibroin solution to pour in the skeleton mold to form a skeleton; S3: Use silk fibroin to electrospin on the surface of the skeleton to form a fiber layer; the electrospinning method in step S3 is the electrospinning method. In step S3, the fiber layer is at least divided into a fast-degrading layer close to the skeleton and a slow-degrading layer far from the skeleton. The fiber diameter of the fast-degrading layer is smaller than that of the slow-degrading layer. Among them, the electrospinning voltage of the fast-degrading layer is lower than that of the slow-degrading layer; S4: Design an intramedullary nail mold, put the skeleton with the fiber layer in step S3 into the intramedullary nail mold, and use silk fibroin solution to pour in the intramedullary nail mold to complete the pressure fixation of the fiber layer; S5: Repeat steps S3 and S4, electrospin to form multiple fiber layers, and perform separate pressure fixation on the multiple fiber layers until the production of the intramedullary nail is completed.

2. The manufacturing method of the intramedullary nail according to claim 1, characterized in that: In step S3, the electrospinning voltage range of the fast-degrading layer is 5-10 kV, and the electrospinning voltage range of the slow-degrading layer is 15-30 kV.

3. The manufacturing method of the intramedullary nail according to claim 1, characterized in that: In step S5, the electrospinning voltage of the electrospun fiber layer in the repeated step S3 gradually increases from the inside to the outside.

4. The manufacturing method of the intramedullary nail according to claim 1, characterized in that: The fiber layer formed in step S3 is added with drugs, and the fiber layer formed in the repeated step S3 in step S5 is added with different drugs.

5. The manufacturing method of the intramedullary nail according to claim 1, characterized in that: In step S4, the silk fibroin solution is added with drugs, and the silk fibroin solution in the repeated step S4 in step S5 is added with different drugs.

6. The manufacturing method of the intramedullary nail according to claim 1, characterized in that: The manufacturing method of the intramedullary nail further includes step S6 after step S5: grinding, polishing, cleaning and inspecting the manufactured intramedullary nail.

7. The manufacturing method of the intramedullary nail according to claim 6, characterized in that: The manufacturing method of the intramedullary nail further includes step S7: making nail holes.

Images