Implant

Abstract

The present invention provides a hollow implant that can effectively inhibit infection. The implant (1) includes an implant body (2) and an antibacterial property imparting unit (3). The implant body (2) is inserted into biological tissue and has a hollow portion (2c) that penetrates the implant body (2). The antibacterial property imparting unit (3) imparts antibacterial property to at least the hollow portion (2c) of the implant body (2).

Description

Technical Field

[0001] The present invention relates to an implant, and particularly to an implant having antibacterial properties. Background Art

[0002] Conventionally, in orthopedic surgery, as a treatment method for fractures and the like, osteosynthesis using a bone plate and bone screws has been performed (for example, refer to Patent Document 1). As an adverse condition in the clinic of osteosynthesis, infection accounts for a large proportion, and a reduction in the infection rate is required. Therefore, an implant having an antibacterial treatment applied to its surface is used (for example, refer to Patent Document 2).

[0003] Prior Art Documents

[0004] Patent Documents

[0005] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2015-167779

[0006] Patent Document 2: Japanese Patent No. 5590596 Summary of the Invention

[0007] Problems to be Solved by the Invention

[0008] As a bone screw, in order to improve the surgical operability and reduce the invasion to the patient, a hollow screw is sometimes used. After inserting such a hollow implant into a body tissue such as a bone, inside the tissue, a space communicating with the outside is formed by the hollow portion of the implant. This space may become one of the main infection paths.

[0009] The present invention has been made in view of the above circumstances, and an object thereof is to provide a hollow implant capable of effectively suppressing infection.

[0010] Means for Solving the Problems

[0011] In order to achieve the above object, the present invention provides the following method.

[0012] One aspect of the present invention is an implant including an implant body and an antibacterial property imparting unit. The implant body is an implant body to be inserted into a living tissue and has a hollow portion penetrating the implant body, and the antibacterial property imparting unit imparts antibacterial properties to at least the hollow portion of the implant body.

[0013] In a state where the implant body is inserted into the tissue of a living body, a space communicating with the outside of the body is formed inside the tissue by the hollow portion. The space formed by the hollow portion may become one of the main infection paths. According to this method, antibacterial properties can be imparted to the hollow portion by the antibacterial property imparting unit. And since the hollow portion does not directly contact the tissue, the influence on the healing of the implant body and the tissue and the influence on the cells around the implant body are not increased, and the antibacterial property of the hollow portion can be improved. Thereby, infection can be effectively suppressed.

[0014] In the above method, the antibacterial property imparting unit may impart higher antibacterial properties to the hollow portion than the outer surface of the implant body.

[0015] The antibacterial property of the outer surface of the implant body that directly contacts the tissue is different from that of the hollow portion, and it will directly affect the healing with the tissue and the cells. According to this structure, by reducing the antibacterial property of the outer surface, the influence on the healing with the tissue and the cells can be effectively suppressed.

[0016] In the above method, the outer surface of the implant body may not be subjected to antibacterial treatment.

[0017] According to this structure, the biocompatibility of the outer surface of the implant body that directly contacts the tissue can be improved, and the influence on the healing with the tissue and the cells can be further suppressed.

[0018] In the above method, it may also be that: the antibacterial property imparting unit is an antibacterial layer formed by antibacterial treatment of the surface of the implant body, and the antibacterial layer is formed at least on the inner surface of the hollow portion.

[0019] According to this structure, the implant body itself can have antibacterial properties.

[0020] In the above method, the antibacterial layer may be a silver layer.

[0021] Silver has high antibacterial properties and high biocompatibility has been confirmed. Therefore, by using a silver layer as the antibacterial layer, the antibacterial property and biocompatibility of the implant can be taken into account. In order to suppress the influence of the silver layer on the healing with the tissue and the cells, it is preferred that the silver layer is formed only on the inner surface of the hollow portion among the surfaces of the implant body.

[0022] In the above method, it is preferred that the film thickness of the silver layer is 0.1 μm or more and 10 μm or less.

[0023] When inserting the implant body into the biological tissue, since the instrument inserted into the hollow portion contacts the silver layer on the inner surface of the hollow portion, there is a possibility that the silver layer may peel off. By limiting the film thickness to 10 μm or less, the amount of peeling of the silver layer can be suppressed. In addition, by making the film thickness of the silver layer 0.1 μm or more, the antibacterial property of the silver layer can be ensured.

[0024] In the above manner, it may also be that: the inner surface of the hollow portion has a concave portion recessed toward the outside of the implant body, and the antibacterial layer is formed in the concave portion.

[0025] The antibacterial layer in the concave portion is difficult to contact the instrument in the hollow portion. Therefore, peeling of the antibacterial layer caused by contact with the instrument can be prevented.

[0026] In the above manner, the antibacterial property imparting unit may also be an antibacterial member inserted into the hollow portion.

[0027] According to this structure, antibacterial property can be imparted to the hollow portion only by a simple operation of inserting the antibacterial member into the hollow portion. In addition, as the implant body, an implant body without antibacterial property in the hollow portion can be used.

[0028] In the above manner, it may also be that: the implant is a bone screw having a screw body screwed into the bone as the implant body, and the hollow portion penetrates the screw body in the direction along the long axis of the screw body.

[0029] Advantages of the Invention

[0030] According to the present invention, there is an effect that infection can be effectively suppressed. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 are a (a) side view and (b) a plan view observed from the head side of a bone screw which is an implant according to an embodiment of the present invention.

[0032] Figure 2 is Figure 1 a longitudinal sectional view of the bone screw.

[0033] Figure 3A is a view showing an example of the antibacterial layer formed in the concave portion on the inner surface of the hollow portion.

[0034] Figure 3B is a view showing another example of the antibacterial layer formed in the concave portion on the inner surface of the hollow portion.

[0035] Figure 4 is a longitudinal sectional view of a bone screw according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0036] Hereinafter, an implant according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0037] As Figure 1 and Figure 2 shown, the implant 1 according to this embodiment is a bone screw, and includes a hollow screw body (implant body) 2 that is screwed into a bone (biological tissue) and an antibacterial property imparting unit 3 that imparts antibacterial properties to the screw body 2.

[0038] The screw body 2 has a shaft portion 2a extending along the long axis A, a head portion 2b connected to the proximal end of the shaft portion 2a, and a hole that penetrates the screw body 2 in the direction along the long axis A, that is, a hollow portion 2c.

[0039] External threads for fixing the screw body 2 to the bone are provided on the outer peripheral surface of the shaft portion 2a, and external threads for fixing the screw body 2 to a bone plate described later are provided on the outer peripheral surface of the head portion 2b. When the screw body 2 is screwed into the bone, a guide pin for guiding the screw body 2 is inserted into the hollow portion 2c.

[0040] The screw body 2 is formed of a biocompatible material commonly used in bone screws. For example, the screw body 2 is formed of a metal such as a titanium alloy or pure titanium, a synthetic resin such as PEEK (polyetheretherketone), or a ceramic.

[0041] The antibacterial property imparting unit 3 is an antibacterial layer that coats the surface of the screw body 2 and is formed by an antibacterial treatment on the surface of the screw body 2. In the antibacterial layer 3, as antibacterial components that exhibit antibacterial properties in the body, for example, metal ions such as silver ions or copper ions, ceramics such as silicon nitride, iodine, or known antibacterial drugs are included. The antibacterial layer 3 preferably has an antibacterial activity value of 2.0 or more. The antibacterial activity value is measured by an antibacterial test method based on JIS Z 2801. It is also possible to slowly release antibacterial components from the antibacterial layer 3 into the space inside the hollow portion 2c.

[0042] The antibacterial layer 3 is formed only on the inner surface 2e of the hollow portion 2c within the surface of the screw body 2. The outer surface 2d has lower antibacterial properties than the antibacterial layer 3, for example, an antibacterial activity value of less than 2.0. For example, on the outer surface 2d, the biocompatible material forming the screw body 2 is exposed.

[0043] For example, by performing the antibacterial treatment described later on the screw body 2 in a state where the outer surface 2d is masked by a masking material, it is possible to selectively perform antibacterial treatment on the inner surface 2e of the hollow portion 2c to form the antibacterial layer 3. With such an antibacterial layer 3, higher antibacterial properties can be imparted to the hollow portion 2c than to the outer surface 2d. The antibacterial layer 3 is formed on at least a part of the inner surface 2e, and preferably formed on the entire inner surface 2e.

[0044] The antibacterial treatment is a surface treatment for imparting antibacterial properties to the surface of the screw body 2 by modifying the surface of the material of the screw body 2. As the surface treatment, either a dry process or a wet process can be used.

[0045] Examples of the dry process are dry plating, sputtering, thermal spraying, or heat treatment. Dry plating is, for example, vacuum evaporation plating, physical vapor deposition (PVD), or chemical vapor deposition (CVD). Heat treatment is, for example, carburizing and quenching, nitriding, soft nitriding, or high-frequency quenching.

[0046] Examples of the wet process are wet plating. Wet plating is, for example, electroplating, electroless plating, or chemical conversion treatment.

[0047] In a preferred example, the antibacterial layer 3 is a silver layer mainly composed of silver. The silver layer may further contain impurities corresponding to the antibacterial treatment for forming the silver layer in addition to silver. In one example, the silver layer is formed by evaporation plating or plating.

[0048] In the case of evaporation plating, the silver can be evaporated by heating a thin silver wire inserted into the hollow portion 2c, thereby forming a silver layer on the inner surface 2e.

[0049] In the case of plating, a silver layer is formed on the entire surface of the screw body 2, and then the unnecessary silver layer is removed. Alternatively, the plating treatment is performed in a state where the surface of the screw body 2 except for the inner surface 2e is masked.

[0050] The film thickness of the silver layer 3 is preferably 0.01 μm or more and 100 μm or less.

[0051] By contacting the silver layer 3 on the inner surface 2e through the guide pin, the silver layer 3 can be peeled off from the inner surface 2e. The peeled piece of the silver layer 3 peeled off from the inner surface 2e moves to the outside of the hollow portion 2c, and may affect the cells around the screw body 2. Therefore, it is preferable that the peeling amount of the silver layer 3 is small. By limiting the film thickness to 100 μm or less, even if the silver layer 3 is peeled off, the peeling amount can be suppressed.

[0052] In addition, in order to ensure sufficient antibacterial properties of the silver layer 3, the film thickness is preferably 0.01 μm or more. Technically, it is difficult to control the film thickness to a level less than 0.01 μm.

[0053] From the viewpoints of suppressing the peeling amount of the silver layer 3 and high antibacterial properties, the film thickness is more preferably 0.1 μm or more and 10 μm or less. In order to further suppress the peeling amount of the silver layer 3, the film thickness can be 1 μm or less.

[0054] Next, the action of the bone screw 1 will be described.

[0055] In an example of the use of the bone screw 1, the bone screw 1 is used to fix a bone plate disposed at a fracture site of a patient to a bone. The bone plate has an internal thread fastened to the head 2b.

[0056] First, a guide pin is inserted into the bone along the path where the screw body 2 should be screwed in, and the bone plate is disposed on the surface of the bone in such a way that the guide pin passes through the internal thread. Then, the shaft portion 2a of the screw body 2 is screwed into the bone along the guide pin inserted into the hollow portion 2c. Then, the head 2b is fastened to the internal thread of the bone plate, thereby fixing the bone plate to the bone.

[0057] In a state where the screw body 2 is screwed into the bone, a space communicating with the outside of the patient is formed inside the bone through the hollow portion 2c. That is, the hollow portion 2c may become one of the main infection paths. In addition, during the operation, since instruments such as a guide pin are to be inserted into the hollow portion 2c, bacteria easily transfer from the instruments to the air and the inner surface 2e in the hollow portion 2c. Therefore, in the case of the hollow bone screw 1, it is important to prevent infection via the hollow portion 2c.

[0058] According to the present embodiment, the antibacterial layer 3 covering the inner surface 2e imparts antibacterial properties to the hollow portion 2c. Thereby, it is possible to effectively prevent infections that may occur during the operation.

[0059] In addition, from the viewpoints of the influence on the bone healing between the screw body 2 and the bone and the influence on the cells around the screw body 2, it is difficult to provide an antibacterial layer with high antibacterial properties on the outer surface 2d of the screw body 2 that is in direct contact with the bone. In contrast, since the hollow portion 2c is not in direct contact with the bone, it is possible to increase the antibacterial properties of the antibacterial layer 3 without increasing the influence on bone healing and cells. For example, it is possible to provide the antibacterial layer 3 containing a strong antibacterial component or the antibacterial layer 3 with a high concentration of antibacterial component on the inner surface 2e of the hollow portion 2c while suppressing the influence on bone healing and cells. Through such an antibacterial layer 3 with high antibacterial properties, it is possible to more effectively prevent infections.

[0060] In addition, assuming that the outer surface 2d is covered with an antibacterial layer, as described above, the antibacterial properties of the antibacterial layer on the outer surface 2d may have an impact on bone healing and cells. According to the present embodiment, the outer surface 2d of the screw body 2 exposed to the bone has low antibacterial properties or no antibacterial properties. Therefore, it is possible to effectively suppress infections while suppressing the influence on bone healing and the bone.

[0061] Furthermore, during the process of screwing the screw body 2 into the bone, the outer surface 2d will rub against the bone, and thus the antibacterial layer on the outer surface 2d is likely to peel off. In contrast, since the inner surface 2e of the hollow portion 2c does not contact the bone, it is difficult for the antibacterial layer 3 to peel off. After the screw body 2 is screwed into the bone, the antibacterial layer 3 also persists on the inner surface 2e. Therefore, after the screw body 2 is screwed into the bone, the antibacterial property of the antibacterial layer 3 against the hollow portion 2c can be reliably exerted.

[0062] In addition, after the screw body 2 is screwed into the bone, body fluids such as blood that move between the hollow portion 2c and the bone transport the antibacterial components contained in the antibacterial layer 3 to the periphery of the screw body 2. Thereby, it is possible to expect infection suppression not only in the hollow portion 2c but also outside the screw body 2.

[0063] In the present embodiment, the inner diameter of the front end side of the hollow portion 2c may also be larger than the inner diameter of the base end side of the hollow portion 2c. For example, the inner diameter of the hollow portion 2c may gradually increase from the base end side toward the front end side. The difference between the inner diameter of the front end side and the inner diameter of the base end side is preferably 0.01 mm or more and 1 mm or less.

[0064] According to this structure, it is possible to reduce the contact between the guide pin and the antibacterial layer 3 on the inner surface 2e on the front end side of the hollow portion 2c, and it is possible to further reduce the peeling of the antibacterial layer 3.

[0065] In the present embodiment, the film thickness of the antibacterial layer 3 may be uniform or non-uniform. For example, in order to suppress the peeling amount of the antibacterial layer 3 on the front end side of the hollow portion 2c, the film thickness may gradually become thinner from the base end side toward the front end side.

[0066] In addition, the antibacterial layer 3 may also be formed only on a part of the inner surface 2e. When the antibacterial layer 3 is formed only on a part of the inner surface 2e, in order to obtain antibacterial property over the entire length of the hollow portion 2c, the antibacterial layer 3 may be distributed over the entire length of the hollow portion 2c. For example, the antibacterial layer 3 may be formed only on a part of the circumferential direction of the smooth cylindrical inner surface 2e.

[0067] As Figure 3A shown, the inner surface 2e of the hollow portion 2c may have a recess 2f that is recessed radially outward of the screw body 2, and the antibacterial layer 3 may be formed only within the recess 2f. For example, the recess 2f is a spiral-shaped, thread-shaped, or linear groove. The depth of the recess 2f is preferably 0.1 mm or more and 1 mm or less. The antibacterial layer 3 within the recess 2f is difficult to contact the guide pin inserted into the hollow portion 2c, and thus the peeling of the antibacterial layer 3 can be prevented.

[0068] As Figure 3BAs shown, an antibacterial layer 3 can also be formed on the inner surface 2e outside the recess 2f. In this case, the antibacterial layer 3 inside the recess 2f becomes thicker, and the antibacterial layer 3 outside the recess 2f becomes thinner.

[0069] The hollow portion 2c can also receive the liquid injected from one of the openings on the head 2b side and the front end side of the shaft portion 2a, and discharge the liquid that has passed through the hollow portion 2c to the other opening. In addition, it can also be configured such that by providing holes or slits that connect the inner peripheral surface of the hollow portion 2c to the outer peripheral surface of the shaft portion 2a, the injected liquid is also discharged from the outer peripheral surface of the shaft portion 2a.

[0070] An antibacterial liquid medicine, a growth factor that promotes bone formation, components from autologous tissue (PRP, bone marrow), bone cement, etc. can also be injected percutaneously into the hollow portion 2c of the bone screw 1 retained in the bone. Such postoperative percutaneous liquid injection may occur multiple times, and new bacteria may invade the hollow portion 2c. According to this embodiment, the antibacterial layer 3 on the inner surface 2e of the hollow portion 2c can prevent the proliferation and infection of bacteria.

[0071] The front end portion of the injection device for injecting liquid into the hollow portion 2c is preferably structured to seal the entrance of the hollow portion 2c in such a way that the liquid does not leak from the entrance of the hollow portion 2c. For example, the front end portion of the injection device can also be a structure that can be fitted to the entrance of the hollow portion 2c by a threaded portion formed inside the hollow portion 2c or a threaded portion of a member disposed in the hollow portion 2c or a pressing force other than the threaded structure. In order to reduce the work during injection after the operation, the front end portion of the injection device can also be an indwelling needle or a tube that can be indwelled. In addition, the injection device is preferably subjected to antibacterial treatment in the same manner as the bone screw 1.

[0072] In this embodiment, the antibacterial property imparting unit is the antibacterial layer 3, but it can also be replaced by other units.

[0073] Figure 4 Reference numeral 11 denotes a bone screw according to another embodiment of the present invention. The bone screw 11 includes an antibacterial member 4 having antibacterial properties and inserted into the hollow portion 2c as an antibacterial property imparting unit. For example, the antibacterial member 4 is a member whose surface is coated with an antibacterial layer containing an antibacterial component. The bone screw 11 can also include an antibacterial layer 3 in addition to the antibacterial member 4.

[0074] Figure 4 The antibacterial member 4 is a long columnar member that is disposed over substantially the entire length in the longitudinal direction of the hollow portion 2c and blocks substantially all of the hollow portion 2c. The antibacterial member 4 can also be a lid-shaped member that is disposed only at the end on the head 2b side of the hollow portion 2c and blocks only the end of the hollow portion 2c.

[0075] By inserting the antibacterial member 4 into the hollow portion 2c, it is possible to block the communication between the hollow portion 2c, which is the cause of infection, and the outside of the body, and it is possible to impart antibacterial properties to the hollow portion 2c with a simple operation. In addition, as the screw body 2, a screw that has not been subjected to antibacterial treatment on the inner surface 2e or has low antibacterial properties on the inner surface 2e can be used.

[0076] In the present embodiment, an antibacterial layer is not formed on the outer surface 2d of the screw body 2, but an antibacterial layer may be formed on the outer surface 2d as long as the hollow portion 2c has higher antibacterial properties than the outer surface 2d. That is, an antibacterial layer having lower antibacterial properties than the antibacterial layer of the hollow portion 2c may be formed on a part or the whole of the outer surface 2d.

[0077] In the above-described embodiment, the bone screws 1, 11 have been described, but the antibacterial property imparting units 3, 4 of the present embodiment can also be applied to other types of orthopedic implants having a hollow portion. That is, the implant of the present invention is not limited to a bone screw, and may be other types of orthopedic implants having a hollow portion. For example, the implant may be a hollow pin inserted into a bone or other living tissue, or a threaded hollow pin having an external thread on a part thereof.

[0078] Reference Signs

[0079] 1, 11: bone screw, implant; 2: screw body, implant body; 2a: shaft portion; 2b: head; 2c: hollow portion; 2d: outer surface; 2e: inner surface; 2f: recess; 3: silver layer, antibacterial layer, antibacterial property imparting unit; 4: antibacterial member, antibacterial property imparting unit.

Claims

1. A bone screw, which is a bone screw with a long axis for fixing an osteosynthesis plate to a bone, comprising: A bone screw body, which is inserted into the bone and has a hollow portion penetrating the bone screw body in the long axis direction; and An antibacterial property imparting unit that imparts antibacterial properties to the hollow portion of the bone screw body, wherein, The antibacterial property imparting unit is an antibacterial layer formed by antibacterial treatment of the surface of the bone screw body, and this antibacterial layer is only coated on the inner surface of the hollow portion. The antibacterial activity value of JIS Z 2801 on the outer surface of the bone screw body is less than 2.

0.

2. The bone screw according to claim 1, wherein, Antibacterial treatment is not performed on the outer surface of the bone screw body.

3. The bone screw according to claim 1, wherein, The antibacterial layer is a silver layer.

4. The bone screw according to claim 3, wherein, The film thickness of the silver layer is 0.1 μm or more and 10 μm or less.

5. The bone screw according to claim 1, wherein, The inner surface of the hollow portion has a recess that is recessed outward from the bone screw body, and the antibacterial layer is formed within the recess.

6. A bone screw, which is a bone screw with a long axis for fixing an osteosynthesis plate to a bone, comprising: A bone screw body, which is inserted into the bone and has a hollow portion penetrating the bone screw body in the long axis direction; and An antibacterial property imparting unit that imparts antibacterial properties to the hollow portion of the bone screw body, wherein, This antibacterial property imparting unit is an antibacterial member inserted into the hollow portion, and this antibacterial member is a columnar member that is disposed over the entire length in the longitudinal direction of the hollow portion to block the hollow portion. The antibacterial activity value of JIS Z 2801 on the outer surface of the bone screw body is less than 2.

0.

7. A bone screw, which is a bone screw with a long axis for fixing an osteosynthesis plate to a bone, comprising: A bone screw body, which is inserted into the bone and has a hollow portion penetrating the bone screw body in the long axis direction; and An antibacterial property imparting unit that imparts antibacterial properties to the hollow portion of the bone screw body, wherein, This antibacterial property imparting unit is an antibacterial member inserted into the hollow portion, and this antibacterial member is a lid-shaped member that is disposed only at one end in the longitudinal direction of the hollow portion to block only the one end of the hollow portion. The antibacterial activity value of JIS Z 2801 on the outer surface of the bone screw body is less than 2.0.

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