Metal implant sterilization device and method for sterilizing metal implant

Abstract

A metal implant sterilization device according to the present invention is a sterilization device that controls a current flowing between a counter electrode and each of a first terminal that is electrically connected to a first working electrode and a second terminal that is electrically connected to a second working electrode having an electrical resistance different from that of the first working electrode, and includes an acquisition unit that acquires a first index representing sterilization effects of the first working electrode electrically connected to the first terminal and a second index representing sterilization effects of the second working electrode electrically connected to the second terminal, and a control unit that controls the current flowing between the counter electrode and each of the first terminal and the second terminal on the basis of the first index and the second index such that the sterilization effects of the first working electrode and the sterilization effects of the second working electrode are the same.

Description

Metal implant sterilization device and method for sterilizing metal implants

[0001] The present disclosure relates to a metal implant sterilization device and a method for sterilizing metal implants. Specifically, the present invention relates to an electrochemical sterilization device and a sterilization method for preventing infection of implanted medical devices (implants) in the medical fields of orthopedics or dentistry.

[0002] Conventionally, implanted medical devices (implants) such as artificial joints have been used. By regaining function with implants, patients are expected to have increased activity in daily life and an improved quality of life.

[0003] Here, in the implantation surgery of implants, bacteria may enter the body and cause infection, and may multiply on the implants. The multiplied bacteria form a biofilm on the implants, causing inflammation in the surrounding tissues of the implants.

[0004] When an infection occurs at the site where the implant is implanted, depending on the symptoms, the infected tissue is scraped, and treatments such as washing and administration of antibiotics are performed to calm the infection. On the other hand, the success rate of calming is generally not high, and there is a risk of reinfection. Therefore, when the degree of inflammation due to infection is large, a treatment is also performed in which the implant is removed, antibiotics are administered for several weeks or more, and then the implant is replaced. However, this treatment places a large burden on the patient and has become a problem.

[0005] Therefore, in order to reduce the burden on the patient, it has been proposed to sterilize by passing an electric current through the implant (for example, Patent Document 1). In Patent Document 1, sterilization is performed by applying a voltage between a working electrode, which is a metal implant, and a counter electrode that forms an electrochemical circuit with this working electrode.

[0006] Japanese Patent Application Laid-Open No. 2023-532549, Japanese Patent Application Laid-Open No. 2022-535812

[0007] “Synchronous Periprosthetic Joint Infections: A Scoping Review of the Literature” Andrea Sambri et.al, Diagnostics 2022, 12, 1841

[0008] In the case of an artificial hip joint implant, for example, the implant is formed by a ball-shaped implant member fixed to the femur, a cup-shaped implant member into which the ball-shaped implant member rotatably fits, and an implant member positioned between these two members. Similarly, an implant forming an artificial knee joint includes, for example, a metal femoral component (implant member), a tibial component, and an insert that acts as cartilage. By placing an insert made of ultra-high molecular weight polyethylene, which replaces cartilage, on the upper surface of the tibial component, smooth joint movement is reproduced.

[0009] As described in Non-Patent Document 1, bacteria may proliferate on multiple implant components during artificial joint implantation surgery. In this case, sterilizing each of the multiple implant components requires processing time for each sterilization treatment. Furthermore, when sterilizing each of the multiple implant components, there is a risk that bacteria may migrate from one implant component to another while one implant component is being sterilized.

[0010] Therefore, when sterilizing the site where an implant is embedded, it is preferable to sterilize these multiple implant components simultaneously.

[0011] Multiple implant components may be formed from materials with different electrical resistances. When a voltage is applied between the working electrodes, which are multiple implant components, and the counter electrodes that form an electrochemical circuit with these working electrodes, the electrochemical reactions at each of the working electrodes will differ, which may mean that the same bactericidal effect cannot be obtained from each of the multiple implant components.

[0012] Patent Document 2 discloses a method for detecting the optimal cathode voltage by dynamic polarization scanning of a single electrode, and a sterilization method. When such a method is applied in parallel for sterilizing multiple implant members, it is difficult to accurately detect the optimal cathode voltage using dynamic polarization scanning on two types of alloys with different electrical resistances. Furthermore, when such a method is applied in parallel, new technical problems arise, such as the current concentrating on one of the low-resistance implant members, leading to an overreaction and compromising safety, or the sterilization of the other member becoming insufficient, resulting in an uncontrollable state.

[0013] To avoid the safety risks mentioned above, a method of sterilizing each implant component, which consists of two or more alloys, individually is conceivable. However, this method introduces a new problem: increased sterilization time. Furthermore, when treating each implant using two potentiostat control devices, crosstalk makes it difficult to detect the optimal cathode voltage using polarization scanning, potentially leading to control system failure.

[0014] Therefore, the object of this disclosure is to provide a metal implant sterilization device that can obtain the same sterilization effect with multiple working electrodes having different electrical resistances.

[0015] (1) According to one embodiment disclosed herein, a metal implant sterilization device is provided. The sterilization device controls the current flowing between a counter electrode and a first terminal electrically connected to a first working electrode and a second terminal electrically connected to a second working electrode having a different electrical resistance from the first working electrode, and a first indicator that acquires a first indicator representing the sterilization action of the first working electrode electrically connected to the first terminal and a second indicator representing the sterilization action of the second working electrode electrically connected to the second terminal, and a control unit that controls the current flowing between a counter electrode and each of the first and second terminals so that the sterilization action of the first working electrode electrically connected to the first terminal and the sterilization action of the second working electrode electrically connected to the second terminal are the same, based on the first and second indicators.

[0016] (2) In this sterilization device, it is preferable that the first working electrode and the second working electrode are implant members that constitute a metal implant.

[0017] (3) In this metal implant sterilization device, the first indicator is the first current density of the current flowing between the first terminal and the counter electrode, and the second indicator is the second current density of the current flowing between the second terminal and the counter electrode. The control unit preferably controls the current flowing between the first terminal and the second terminal and the counter electrode so that the first current density and the second current density are the same.

[0018] (4) In this metal implant sterilization device, the first indicator is the amount of charge flowing between the first terminal and the counter electrode, and the second indicator is the amount of charge flowing between the second terminal and the counter electrode. The control unit preferably controls the current flowing between the first terminal and the second terminal and the counter electrode so that the total amount of charge flowing between the first terminal and the counter electrode and the total amount of charge flowing between the second terminal and the counter electrode are distributed according to the area ratio of the respective electrodes.

[0019] (5) In addition, in this metal implant sterilization device, the first indicator is the first pH near the first working electrode, and the second indicator is the second pH near the second working electrode, and it is preferable that the control unit controls the current flowing between the first terminal and the second terminal and the counter electrode so that the first pH and the second pH are the same.

[0020] (6) In this metal implant sterilization device, the first indicator is the first pH near the first working electrode, the second indicator is the second pH near the second working electrode, and the control unit preferably controls the current flowing between the first terminal and the second terminal and the counter electrode so that the rate of change of the first pH per unit time and the rate of change of the second pH per unit time are the same.

[0021] (7) In other embodiments disclosed herein, a method for sterilizing a metal implant is provided. This method for sterilizing a metal implant is a sterilization method that controls the current flowing between each of a first terminal electrically connected to a first working electrode and a second terminal electrically connected to a second working electrode having a different electrical resistance from the first working electrode and a counter electrode, characterized in that the sterilization device acquires a first index representing the sterilization action of the first working electrode connected to the first terminal and a second index representing the sterilization action of the second working electrode connected to the second terminal, and performs a process that includes controlling the current flowing between each of the first and second terminals and the counter electrode so that the sterilization action of the first working electrode electrically connected to the first terminal and the sterilization action of the second working electrode electrically connected to the second terminal are the same, based on the first and second indices.

[0022] According to the metal implant sterilization device disclosed herein as described above, a similar sterilization effect can be obtained with multiple working electrodes having different electrical resistances.

[0023] This is a schematic diagram of the metal implant sterilization device of the first embodiment. This is an electrical circuit diagram of the main part of the metal implant sterilization device. This is a hardware configuration diagram of the control device. This is an example of an operation flowchart of the control process of the metal implant sterilization device of the first embodiment. This is an example of an operation flowchart of the control process of the metal implant sterilization device of the second embodiment. This is a diagram illustrating an embodiment. This is a diagram illustrating Comparative Example 1. This is a diagram illustrating Comparative Example 2. This is a diagram illustrating the measurement results of the embodiment. This is a diagram illustrating the measurement results of Comparative Example 1 and Comparative Example 2. This is a diagram illustrating the measurement results of Comparative Example 3.

[0024] Figure 1 is a schematic diagram of the metal implant sterilization device 10 of the first embodiment. Hereinafter, the metal implant sterilization device 10 will also be simply referred to as the sterilization device 10. The sterilization device 10 sterilizes the implant 30 embedded in the hip joint of patient 50. During and after the implantation surgery of the implant 30, bacteria may enter the body of patient 50 and multiply on the implant 30. The multiplied bacteria form a biofilm on the implant 30, causing inflammation in the tissue surrounding the implant 30. The sterilization device 10 supplies power to the implant 30, which reduces water and / or oxygen contained in the tissue surrounding the implant 30 to generate bactericidal substances such as hydroxide ions, and sterilization is performed by these bactericidal substances.

[0025] The implant 30 comprises a first implant member (also called a cup) 31 positioned on the pelvic side and having a hollow, hemispherical shape; a second implant member (also called a ball) 32 positioned on the femur side and having a spherical shape; a third implant member (also called an insert or liner) 33 positioned between the first implant member 31 and the second implant member 32 and having a hollow, hemispherical shape; and a fourth implant member (also called a stem) 34 inserted into the femur. The first implant member 31, the second implant member 32, and the fourth implant member 34 may be formed using electrically conductive materials. The first implant member 31, the second implant member 32, and the fourth implant member 34 constitute a metal implant.

[0026] The second implant member 32 is fixed to the femur by the fourth implant member 34. The second implant member 32 rotatably engages with the third implant member 33.

[0027] The first implant member 31 can be formed from an alloy such as Ti-6Al-4V, a conductor such as titanium, etc. The first implant member 31 is an example of a first working electrode.

[0028] The second implant member 32 and the fourth implant member 34 have different electrical resistances than the first implant member 31. For example, alloys such as Co-Cr-Mo can be used as the second implant member 32 and the fourth implant member 34. The second implant member 32 and the fourth implant member 34 are electrically and physically connected. The second implant member 32 and the fourth implant member 34 are examples of second working electrodes.

[0029] The third implant member 33 may be formed from an insulator such as ultra-high molecular weight polyethylene. The first implant member 31, the second implant member 32, and the fourth implant member 34 may be coated with hydroxyapatite or iodine, etc.

[0030] The sterilization device 10 can, for example, simultaneously sterilize the first implant member 31, as well as the second implant member 32 and the fourth implant member 34.

[0031] The first implant member 31, the second implant member 32, and the fourth implant member 34 are supplied with power as working electrodes, which reduces water and / or oxygen contained in the surrounding tissue, generating bactericidal substances such as hydroxide ions. The greater the amount of bactericidal substances, the stronger the bactericidal effect.

[0032] The amount of bactericidal substance can be estimated, for example, based on the current density per unit surface area flowing through the first implant member 31, as well as the second implant member 32 and the fourth implant member 34. The higher the current density, the greater the amount of bactericidal substance. By measuring the current density, the degree of bactericidal action of the first implant member 31 and the second implant member 32 can be measured.

[0033] Furthermore, the amount of bactericidal substances such as hydroxide ions can be measured as pH. By measuring the pH, the degree of bactericidal activity of the first implant member 31 and the second implant member 32 can be measured.

[0034] Sensor S1 measures the pH near the first implant member 31. Sensor S2 measures the pH near the second implant member 32 and the fourth implant member 34. Sensors S1 and S2 each output information representing the measured pH to the control device 13. In the first embodiment, sensors S1 and S2 do not necessarily have to be installed.

[0035] Here, the second implant member 32 and the fourth implant member 34 have different electrical resistances than the first implant member 31, and the second implant member 32 and the fourth implant member 34 have different electrochemical properties from the first implant member 31. The amount of bactericidal substance per unit area generated in the second implant member 32 and the fourth implant member 34 may differ from the amount of bactericidal substance per unit area generated in the first implant member 31.

[0036] If the sterilization effects of the first implant member 31, the second implant member 32, and the fourth implant member 34 are different, then when the same amount of sterilization treatment is performed, the sterilization state of the first implant member 31 may differ from that of the second implant member 32 and the fourth implant member 34.

[0037] The sterilization device 10 can perform sterilization treatment similarly on two working electrodes. The sterilization device 10 includes a user interface (UI) 11, a power supply unit 12, a control device 13, a first terminal P1, a second terminal P2, a counter electrode 18, a reference electrode 19, and wiring 17a to 17e. The UI 11, the power supply unit 12, and the control device 13 are communicated together via a communication line 14. The UI 11, the power supply unit 12, and the control device 13 are supplied with power from a power source (not shown). The sterilization device 10 may also have sensors S1 and S2 for measuring pH.

[0038] The UI 11 is controlled by the power supply unit 12 and the control device 13 to notify the user (e.g., a medical professional) of processing information related to the sterilization process. The UI 11 has a display device such as a liquid crystal display or a touch panel to display the processing information. The UI 11 also has an input device for receiving operation information from the user. The UI 11 has, for example, a touch panel or operation buttons as the input device.

[0039] UI11 inputs the first surface area of ​​the portion of the first implant member 31 exposed to the outside as the first working electrode, and the second surface area of ​​the portions of the second implant member 32 and the fourth implant member 34 exposed to the outside as the second working electrodes, and transmits this to the control device 13. UI11 also inputs the target voltage or target current for the sterilization process and transmits this to the control device 13.

[0040] The power supply unit 12 is electrically connected to a first terminal P1 which is electrically connected to the first implant member 31 which is the first working electrode, a second terminal P2 which is electrically connected to the second implant member 32 and the fourth implant member 34 which are the second working electrodes, a counter electrode 18, and a reference electrode 19.

[0041] The power supply unit 12 can control the potential difference between the first terminal P1 and the second terminal P2 and the counter electrode 18 to a target voltage by referring to the potential difference between the wiring 17a and the wiring 17e (reference electrode 19). The power supply unit 12 has a voltage detection circuit, and the electrode potential can be measured using this voltage detection circuit.

[0042] Furthermore, the power supply unit 12 can control the current flowing between the first terminal P1 and the second terminal P2 and the counter electrode 18 by referring to the potential difference between the wiring 17a and the wiring 17e (reference electrode 19) to achieve a target current. The power supply unit 12 has a current-voltage conversion circuit and can measure the current flowing through the electrodes. The power supply unit 12 is formed using, for example, a potentiostat or a galvanostat.

[0043] The power supply unit 12 supplies power to the first implant member 31 via the wiring 17a, the wiring 17b, and the first terminal P1. The first terminal P1 is electrically connected to the first implant member 31. The power supply unit 12 supplies power to the second implant member 32 and the fourth implant member 34 via the wiring 17a, the wiring 17c, and the second terminal P2. The second terminal P2 is electrically connected to the second implant member 32 and the fourth implant member 34. The power supply unit 12 is electrically connected to the counter electrode 18 via the wiring 17d. The power supply unit 12 is electrically connected to the reference electrode 19 via the wiring 17e. The counter electrode 18 and the reference electrode 19 are arranged, for example, on the skin near the base of the patient's leg. The counter electrode 18 and the reference electrode 19 are removably adhered to the skin via, for example, a conductive adhesive material. Alternatively, the counter electrode 18 and the reference electrode 19 are fixed to the skin using, for example, tape or the like.

[0044] Figure 2 is an electrical circuit diagram of the main part of the sterilization device 10. The wiring 17a electrically connects the power supply unit 12 to the wiring 17b and the wiring 17c. The wiring 17b electrically connects the wiring 17a to the first terminal P1. The first terminal P1 electrically connects the wiring 17b to the first implant member 31. The wiring 17c electrically connects the wiring 17a to the second terminal P2. The second terminal P2 electrically connects the wiring 17c to the second implant member 32 and the fourth implant member 34. The first implant member 31, the second implant member 32, the fourth implant member 34, and the counter electrode 18 are electrically connected via the patient 50's body. The wiring 17d electrically connects the counter electrode 18 to the power supply unit 12. The first implant member 31, the second implant member 32, and the fourth implant member 34 are electrically connected in parallel.

[0045] The ammeter A1 measures the current flowing through the wiring 17a. The current flowing through the wiring 17a is the sum of the currents flowing through the wirings 17b and 17c. The ammeter A2 measures the current flowing through the first terminal P1 via the wiring 17b. Each of the ammeter A1 and the ammeter A2 outputs information representing the measured current to the control device 13. The current flowing through the second terminal P2 is represented by the difference between the current measured by the ammeter A1 and the current measured by the ammeter A2. Note that the ammeter A2 may be arranged in the wiring 17c. In this case, the current flowing through the first terminal P1 is represented by the difference between the current measured by the ammeter A1 and the current measured by the ammeter A2. Also, instead of arranging an ammeter in the wiring 17a, an ammeter may be arranged in each of the wirings 17b and 17c.

[0046] The variable resistor 15 controls the current flowing through the wiring 17b by changing the resistance value R1 under the control of the control device 13. The variable resistor 16 controls the current flowing through the wiring 17c by changing the resistance value R2 under the control of the control device 13.

[0047] FIG. 3 is a hardware configuration diagram of the control device 13. The control device 13 executes acquisition processing, control processing, and determination processing. For this purpose, the control device 13 includes a communication interface (IF) 21, a memory 22, and a processor 23. The communication interface 21, the memory 22, and the processor 23 are connected via a signal line 24.

[0048] The communication IF 21 has an interface circuit for connecting the control device 13 to the communication line 14. The communication IF 21 inputs information representing the currents of each of the ammeter A1 and the ammeter A2 and outputs it to the processor 23. Also, the communication IF 21 inputs information representing the pH of each of the sensors S1 and S2 and outputs it to the processor 23.

[0049] Memory 22 is an example of a storage unit and may include, for example, a volatile semiconductor memory and a non-volatile semiconductor memory. Memory 22 stores computer programs and various data of applications used in information processing executed by the processor 23. Memory 22 may also have a non-volatile storage unit such as an SSD or HDD.

[0050] Memory 22 stores the first surface area of ​​the portion of the first implant member 31 exposed to the outside as the first working electrode, and the second surface area of ​​the portions of the second implant member 32 and the fourth implant member 34 exposed to the outside as the second working electrodes. The first implant member 31 is an example of the first working electrode, and the second implant member 32 and the fourth implant member 34 are examples of the second working electrode.

[0051] All or part of the functions of the control device 13 are functional modules realized, for example, by a computer program running on the processor 23. The processor 23 has an acquisition unit 231, a control unit 232, and a determination unit 233. Alternatively, the functional modules of the processor 23 may be dedicated arithmetic circuits provided on the processor 23. The processor 23 has one or more CPUs (Central Processing Units) and their peripheral circuits. The processor 23 may further have other arithmetic circuits such as a logic unit, a numerical unit, or a graphics processing unit.

[0052] When the sterilization process begins, the power supply unit 12 controls the power (constant voltage control) so that the voltage between the wiring 17a (working electrodes 31, 32, 34) and the wiring 17d (counter electrode 18) becomes the target voltage, while referring to the potential difference between the wiring 17a (working electrodes 31, 32, 34) and the wiring 17e (reference electrode 19). The constant voltage control by the power supply unit 12 continues even during the control process shown in Figure 4 until the sterilization process is completed.

[0053] The UI 11 may be controlled by the control device 13 to display the pH near the first implant member 31 and the pH near the second implant member 32 and the fourth implant member 34, based on the pH information output from sensors S1 and S2.

[0054] Figure 4 is an example of an operation flowchart of the control process of the sterilization device 10 of the first embodiment. When the sterilization process starts, the sterilization device 10 executes the control process according to the operation flowchart shown in Figure 4 at a control time having a predetermined cycle. Next, the control process of the sterilization device 10 will be described below with reference to the operation flowchart shown in Figure 4. At the start of the sterilization process, the resistance values ​​of the variable resistors 15 and 16 are set to initial values. As initial values, for example, the median value of the variable range of the resistance value can be used.

[0055] First, in step S101, the acquisition unit 231 determines the first current density D1 of the current flowing between the first terminal P1 and the counter electrode 18 based on the second current measured by the ammeter A2 and the first surface area of ​​the portion of the first implant member 31 that is exposed to the outside. The acquisition unit 231 also determines the second current density D2 of the current flowing between the second terminal P2 and the counter electrode 18 based on the difference between the first current measured by the ammeter A1 and the second current measured by the ammeter A2 and the combined second surface area of ​​the portions of the second implant member 32 and the fourth implant member 34 that are exposed to the outside.

[0056] The first current density D1 corresponds to the amount of bactericidal substances such as hydroxide ions generated by the reduction of water and / or oxygen contained in the tissue surrounding the first implant member 31, and therefore serves as the first indicator representing the bactericidal effect of the first implant member 31. The second current density D2 corresponds to the amount of bactericidal substances such as hydroxide ions generated by the reduction of water and / or oxygen contained in the tissue surrounding the second implant member 32 and the fourth implant member 34, and therefore serves as the second indicator representing the bactericidal effect of the second implant member 32 and the fourth implant member 34.

[0057] Next, the determination unit 233 determines whether the first current density D1 is greater than the second current density D2 (step S102). The determination unit 233 may determine that the first current density D1 is greater than the second current density D2 if the first current density D1 is greater than the value obtained by adding an offset value to the second current density D2.

[0058] If the first current density D1 is greater than the second current density D2 (step S102 - Yes), the control unit 232 increases the resistance value R1 of the variable resistor 15 (step S103). For example, the control unit 232 increases the resistance value R1 of the variable resistor 15 by 10 ohms. The control unit 232 controls the current flowing between the first terminal P1 and the second terminal P2 and the counter electrode 18 so that the first current density D1 and the second current density D2 are the same.

[0059] The fact that the first current density D1 is greater than the second current density D2 indicates that the bactericidal effect of the first implant member 31 is greater than that of the second implant member 32 and the fourth implant member 34. Therefore, the current flowing through wiring 17b is reduced and the current flowing through wiring 17c is increased. As a result, the bactericidal effect of the first implant member 31 is reduced and the bactericidal effect of the second implant member 32 is increased.

[0060] Next, in step S104, the acquisition unit 231 acquires the first current density D1 and the second current density D2 based on the first current measured by the ammeter A1 and the second current measured by the ammeter A2. The acquisition unit 231 may acquire the first current density D1 and the second current density D2 after waiting for a predetermined waiting time after the resistance value R1 of the variable resistor 15 has increased.

[0061] Next, the determination unit 233 determines whether the second current density D2 is greater than the first current density D1 (step S105). The determination unit 233 may determine that the second current density D2 is greater than the first current density D1 if the second current density D2 is greater than the value obtained by adding an offset value to the first current density D1.

[0062] If the second current density D2 is greater than the first current density D1 (step S105 - Yes), the control unit 232 reduces the resistance value R1 of the variable resistor 15 (step S106). For example, the control unit 232 reduces the resistance value R1 of the variable resistor 15 by 10 ohms.

[0063] The fact that the second current density D2 is greater than the first current density D1 indicates that the bactericidal effect of the second implant member 32 and the fourth implant member 34 is greater than that of the first implant member 31. Therefore, the current flowing through wiring 17b is increased and the current flowing through wiring 17c is decreased. As a result, the bactericidal effect of the first implant member 31 is increased and the bactericidal effect of the second implant member 32 and the fourth implant member 34 is reduced.

[0064] Next, after waiting for a predetermined waiting time (step S107), the process proceeds to step S101. The waiting time can be, for example, 1 to 10 seconds.

[0065] On the other hand, if the second current density D2 is not greater than the first current density D1 (step S105-No), the determination unit 233 determines whether the first current density D1 is greater than the second current density D2 (step S108).

[0066] If the first current density D1 is greater than the second current density D2 (step S108 - Yes), the process proceeds to step S103.

[0067] On the other hand, if the first current density D1 is not greater than the second current density D2 (step S108-No), the first current density D1 and the second current density D2 are the same, so the process proceeds to step S107.

[0068] Furthermore, if the first current density D1 is not greater than the second current density D2 (step S102-No), the determination unit 233 determines whether the second current density D2 is greater than the first current density D1 (step S109).

[0069] If the second current density D2 is greater than the first current density D1 (step S109 - Yes), the control unit 232 increases the resistance value R2 of the variable resistor 16 (step S110). For example, the control unit 232 increases the resistance value R2 of the variable resistor 16 by 10 ohms.

[0070] The fact that the second current density D2 is greater than the first current density D1 indicates that the bactericidal effect of the second implant member 32 and the fourth implant member 34 is greater than that of the first implant member 31. Therefore, the current flowing through wiring 17c is reduced and the current flowing through wiring 17b is increased. As a result, the bactericidal effect of the second implant member 32 and the fourth implant member 34 is reduced and the bactericidal effect of the first implant member 31 is increased.

[0071] Next, in step S111, the acquisition unit 231 acquires the first current density D1 and the second current density D2 based on the first current measured by the ammeter A1 and the second current measured by the ammeter A2 (step S111). The acquisition unit 231 may acquire the first current density D1 and the second current density D2 after increasing the resistance value R2 of the variable resistor 16 and then waiting for a predetermined waiting time.

[0072] Next, the determination unit 233 determines whether the first current density D1 is greater than the second current density D2 (step S112).

[0073] If the first current density D1 is greater than the second current density D2 (step S112 - Yes), the control unit 232 reduces the resistance value R2 of the variable resistor 16 (step S113), and the process proceeds to step S107. For example, the control unit 232 reduces the resistance value R2 of the variable resistor 16 by 10 ohms.

[0074] The fact that the first current density D1 is greater than the second current density D2 indicates that the bactericidal effect of the first implant member 31 is greater than that of the second implant member 32 and the fourth implant member 34. Therefore, the current flowing through wiring 17c is increased and the current flowing through wiring 17b is decreased. As a result, the bactericidal effect of the second implant member 32 and the fourth implant member 34 is increased, and the bactericidal effect of the first implant member 31 is reduced.

[0075] On the other hand, if the first current density D1 is not greater than the second current density D2 (step S112-No), the determination unit 233 determines whether the second current density D2 is greater than the first current density D1 (step S114).

[0076] If the second current density D2 is greater than the first current density D1 (step S114 - Yes), the process proceeds to step S110.

[0077] On the other hand, if the second current density D2 is not greater than the first current density D1 (steps S109-No and S114-No), the second current density D2 and the first current density D1 are the same, so the process proceeds to step S107.

[0078] As described in detail above, the sterilization device of this embodiment can obtain the same sterilization effect with multiple working electrodes having different electrical resistances. Furthermore, the sterilization device of this embodiment can also obtain the same sterilization effect with multiple working electrodes formed from different conductors.

[0079] Next, a second embodiment of the sterilization apparatus disclosed herein will be described below with reference to Figure 5. For aspects of the second embodiment not specifically described, the description of the first embodiment above will apply as appropriate.

[0080] In the sterilization device 10 of this embodiment, the first indicator representing the sterilization action of the first working electrode is the first pH near the first working electrode, and the second indicator representing the sterilization action of the second working electrode is the second pH near the second working electrode. The sterilization device 10 controls the current flowing between the first working electrode and the second working electrode and the counter electrode so that the first pH and the second pH are the same.

[0081] Sensor S1 measures the pH near the first implant member 31. For example, sensor S1 measures the pH at a position within 1 cm of the surface of the first implant member 31. Sensor S2 measures the pH near the second implant member 32 and the fourth implant member 34. For example, sensor S2 measures the pH at a position within 1 cm of the surface of either the second implant member 32 or the fourth implant member 34.

[0082] Figure 5 is an example of an operation flowchart of the control process of the sterilization device 10 of the second embodiment. When the sterilization process starts, the control device 13 executes the control process according to the operation flowchart shown in Figure 5 at a control time having a predetermined cycle. Next, the control process of the sterilization device 10 will be described below with reference to the operation flowchart shown in Figure 5. At the start of the sterilization process, the resistance values ​​of the variable resistors 15 and 16 are set to initial values. As initial values, for example, the median value of the variable range of the resistance value can be used.

[0083] First, in step S201, the acquisition unit 231 acquires pH1 measured by sensor S1 and pH2 measured by sensor S2. The pH inside the body is normally around 7. When the concentration of bactericidal substances such as hydroxide ions increases due to sterilization treatment, the pH rises from 7.

[0084] pH 1 corresponds to the amount of bactericidal substances such as hydroxide ions generated by the reduction of water and / or oxygen contained in the tissue surrounding the first implant member 31, and therefore serves as the first indicator representing the bactericidal effect of the first implant member 31. pH 2 corresponds to the amount of bactericidal substances such as hydroxide ions generated by the reduction of water and / or oxygen contained in the tissue surrounding the second implant member 32 and the fourth implant member 34, and therefore serves as the second indicator representing the bactericidal effect of the second implant member 32 and the fourth implant member 34.

[0085] Next, the determination unit 233 determines whether pH1 is greater than pH2 (step S202). The determination unit 233 may determine that pH1 is greater than pH2 if pH1 is greater than the value obtained by adding an offset value to pH2.

[0086] If pH1 is greater than pH2 (step S202 - Yes), the control unit 232 increases the resistance value R1 of the variable resistor 15 (step S203). For example, the control unit 232 increases the resistance value R1 of the variable resistor 15 by 10 ohms. The control unit 232 controls the current flowing between the first terminal P1 and the second terminal P2 and the counter electrode 18 so that pH1 and pH2 become the same.

[0087] A pH of 1 greater than pH 2 indicates that the bactericidal effect of the first implant member 31 is greater than that of the second implant member 32 and the fourth implant member 34. Therefore, the current flowing through wiring 17b is reduced and the current flowing through wiring 17c is increased. This reduces the bactericidal effect of the first implant member 31 and increases the bactericidal effect of the second implant member 32 and the fourth implant member 34.

[0088] Next, in step S204, the acquisition unit 231 acquires pH1 measured by sensor S1 and pH2 measured by sensor S2. The acquisition unit 231 may acquire pH1 and pH2 after waiting for a predetermined waiting time after the resistance value R1 of the variable resistor 15 increases.

[0089] Next, the determination unit 233 determines whether pH2 is greater than pH1 (step S205). The determination unit 233 may determine that pH2 is greater than pH1 if pH2 is greater than the value obtained by adding an offset value to pH1.

[0090] If pH2 is greater than pH1 (step S205 - Yes), the control unit 232 reduces the resistance value R1 of the variable resistor 15 (step S206). For example, the control unit 232 reduces the resistance value R1 of the variable resistor 15 by 10 ohms.

[0091] A pH of 2 greater than pH 1 indicates that the bactericidal effect of the second implant member 32 and the fourth implant member 34 is greater than that of the first implant member 31. Therefore, the current flowing through wiring 17b is increased and the current flowing through wiring 17c is decreased. This increases the bactericidal effect of the first implant member 31 and reduces the bactericidal effect of the second implant member 32 and the fourth implant member 34.

[0092] Next, after waiting for a predetermined waiting time (step S207), the process proceeds to step S201.

[0093] On the other hand, if pH2 is not greater than pH1 (step S205-No), the determination unit 233 determines whether or not pH1 is greater than pH2 (step S208).

[0094] If pH1 is greater than pH2 (step S208 - Yes), the process proceeds to step S203.

[0095] On the other hand, if pH1 is not greater than pH2 (step S208-No), then pH1 and pH2 are the same, so the process proceeds to step S207.

[0096] Furthermore, if pH1 is not greater than pH2 (step S202-No), the determination unit 233 determines whether or not pH2 is greater than pH1 (step S209).

[0097] If pH2 is greater than pH1 (step S209 - Yes), the control unit 232 increases the resistance value R2 of the variable resistor 16 (step S210). For example, the control unit 232 increases the resistance value R2 of the variable resistor 16 by 10 ohms.

[0098] A pH of 2 greater than pH 1 indicates that the bactericidal effect of the second implant member 32 and the fourth implant member 34 is greater than that of the first implant member 31. Therefore, the current flowing through wiring 17c is reduced and the current flowing through wiring 17b is increased. This reduces the bactericidal effect of the second implant member 32 and the fourth implant member 34, and increases the bactericidal effect of the first implant member 31.

[0099] Next, in step S211, the acquisition unit 231 acquires pH1 measured by sensor S1 and pH2 measured by sensor S2 (step S211). The acquisition unit 231 may acquire pH1 and pH2 after waiting for a predetermined waiting time after the resistance value R2 of the variable resistor 16 has increased.

[0100] Next, the determination unit 233 determines whether pH1 is greater than pH2 (step S212).

[0101] If pH1 is greater than pH2 (step S212 - Yes), the control unit 232 reduces the resistance value R2 of the variable resistor 16 (step S213), and the process proceeds to step S207. For example, the control unit 232 reduces the resistance value R2 of the variable resistor 16 by 10 ohms.

[0102] A pH of 1 greater than pH 2 indicates that the bactericidal effect of the first implant member 31 is greater than that of the second implant member 32 and the fourth implant member 34. Therefore, the current flowing through wiring 17c is increased and the current flowing through wiring 17b is decreased. This increases the bactericidal effect of the second implant member 32 and the fourth implant member 34, and reduces the bactericidal effect of the first implant member 31.

[0103] On the other hand, if pH1 is not greater than pH2 (step S212-No), the determination unit 233 determines whether or not pH2 is greater than pH1 (step S214).

[0104] If pH2 is greater than pH1 (step S214 - Yes), the process proceeds to step S210.

[0105] On the other hand, if pH2 is not greater than pH1 (steps S209-No and S214-No), then pH2 and pH1 are the same, and the process proceeds to step S207.

[0106] As described in detail above, the sterilization device of this embodiment makes it possible to obtain the same sterilization effect with multiple working electrodes having different electrical resistances.

[0107] In the present invention, the sterilization apparatus and sterilization method of the embodiments described above can be modified as appropriate without departing from the spirit of the invention. Furthermore, the constituent elements of one embodiment can be appropriately applied to other embodiments.

[0108] For example, in the sterilization apparatus of the first and second embodiments described above, the first implant member, the second implant member, and the fourth implant member were sterilized, but the third implant member and the other implant members may also be sterilized.

[0109] Furthermore, while the sterilization apparatus of the first and second embodiments described above sterilized the first and second working electrodes, the sterilization apparatus can also sterilize three or more working electrodes. For example, the sterilization apparatus includes an acquisition unit that acquires a first indicator representing the sterilization effect of the first working electrode, a second indicator representing the sterilization effect of the second working electrode, and a third indicator representing the sterilization effect of the third working electrode, and a control unit that controls the current flowing between each of the first, second, and third working electrodes and the counter electrode so that the sterilization effects of the first, second, and third working electrodes are the same, based on the first, second, and third indicators.

[0110] Furthermore, in the sterilization apparatus of the first embodiment described above, the control unit controlled the sterilization action of each working electrode using a variable resistor to keep the amount of charge supplied per unit area constant, but the method of controlling the sterilization action of the electrodes is not limited to this. For example, the control unit may control the power supplied to each working electrode so that the total amount of charge supplied during the sterilization process is constant. Specifically, the first indicator is the amount of charge flowing between the first working electrode and the counter electrode, and the second indicator is the amount of charge flowing between the second working electrode and the counter electrode. The control unit may use a power supply unit that supplies power to the first and second working electrodes to control the current flowing between each of the first and second working electrodes and the counter electrode. The power supply unit controls the power to achieve a target voltage or target current. The amount of charge flowing between the first working electrode and the counter electrode is calculated as the product of current and time. The amount of charge flowing between the second working electrode and the counter electrode is calculated as the product of current and time. The control unit controls the current flowing between the first working electrode and the second working electrode and the counter electrode so that the total amount of charge flowing between the first working electrode and the counter electrode and the total amount of charge flowing between the second working electrode and the counter electrode are distributed according to the surface area ratio of the respective electrodes. For example, if the ratio of the surface area of ​​the first working electrode to the surface area of ​​the second working electrode is 2:1, the control unit controls the current flowing between the first working electrode and the counter electrode and the counter electrode so that the total amount of charge flowing between the first working electrode and the counter electrode and the total amount of charge flowing between the second working electrode and the counter electrode are in a ratio of 2:1. The control unit may also use a power supply unit to perform PWM control of the voltage between the first working electrode and the second working electrode and the counter electrode. For example, it is preferable for the control unit to use a DC-DC converter (linear regulator or switching regulator) to perform PWM control of the voltage.

[0111] Furthermore, in the sterilization apparatus of the second embodiment described above, the control unit controlled the current flowing between the first working electrode and the second working electrode and the counter electrode so that the first pH and the second pH would be the same. However, the method of controlling the sterilization action of the working electrodes is not limited to this. For example, the control unit may control the current flowing between the first working electrode and the second working electrode and the counter electrode so that the rate of change of the first pH per unit time and the rate of change of the second pH per unit time are the same. Since the initial values ​​of the first pH and the second pH are both about 7, the first pH and the second pH can also be controlled to be the same by controlling them so that the rate of change of the first pH per unit time and the rate of change of the second pH per unit time are the same. Here, upper limits may be set for both the first pH and the second pH, and the control unit may control the current flowing between the first working electrode and the second working electrode and the counter electrode so that the rate of change of the first pH per unit time and the rate of change of the second pH per unit time are the same, so that neither the first pH nor the second pH exceeds the upper limit. The upper limits for the first pH and the second pH can be appropriately determined from the viewpoint of bactericidal effect and safety.

[0112] Furthermore, in the sterilization apparatus of the first and second embodiments described above, the potential difference between the first working electrode and the second working electrode and the counter electrode was controlled to reach a target voltage by referring to the potential difference between the first working electrode and the second working electrode and the reference electrode. However, the sterilization apparatus may also control the current flowing between the first working electrode and the second working electrode and the counter electrode to reach a target current by referring to the potential difference between the first working electrode and the second working electrode and the reference electrode.

[0113] Furthermore, in the first embodiment described above, steps S104 to S108 and steps S111 to S114 may be omitted. In this case, the process proceeds to step S107 after step S103, and to step S107 after step S110.

[0114] Similarly, in the second embodiment described above, steps S204 to S208 and steps S211 to S214 may be omitted. In this case, the process proceeds to step S207 after step S203, and to step S207 after step S210.

[0115] The sterilization apparatus and sterilization method disclosed herein will be further described below with reference to examples. However, the scope of the present invention is not limited to these examples.

[0116] (Example) First, a simulated test specimen 45, as shown in Figure 6, was prepared. An aqueous solution containing 3% agar (Cat #010-15815, Fujifilm Wako Pure Chemical Industries, Ltd.) and 0.9% sodium chloride (Cat #191-01665, Fujifilm Wako Pure Chemical Industries, Ltd.) was prepared, and this aqueous solution was heat-treated at 121°C for 20 minutes using an autoclave to prepare an agar solution. This agar solution was poured into a glass container (AGC Techno Glass Co., Ltd., W25.5 × D21 × H6 cm), cooled to room temperature and allowed to solidify completely to obtain the simulated test specimen 45.

[0117] Wells 41, 42, and 43 were prepared in the simulated test specimen 45, and 100 mL of equilibrium salt solution (D-PBS(-), Cat#045-29795, Fujifilm Wako Pure Chemical Industries, Ltd.) was injected into each of the wells 41, 42, and 43. The first working electrode 31a was placed in well 41, the second working electrode 32a was placed in well 42, and the counter electrode 18 was placed in well 43. The exposed surface area of ​​the first working electrode 31a was 10.5 cm². ２ A Ti-6Al-4V alloy piece was used. The second working electrode 32a had an exposed surface area of ​​10.5 cm². ２A Co-Cr-Mo alloy piece was used. A Pt mesh (Tanaka Kikinzoku Kogyo Co., Ltd., 100 mm x 100 mm, wire diameter Φ0.076, plain weave, 80 mesh) was used as the counter electrode 18. An Ag / AgCl electrode (Cat# MSGLT-08G, medico) was used as the reference electrode 19. The first working electrode 31a, the second working electrode 32a, the counter electrode 18, the reference electrode 19 were electrically connected to the power supply unit 12 (Cat# HA-151B, Meiden Hokuto Denko Co., Ltd.). Titanium wire (Cat# TIS-3, Sunhayato Co., Ltd.) was used as the first terminal P1 and the second terminal P2. The titanium wire was electrically insulated except for the connection part with the alloy piece.

[0118] Furthermore, as shown in the electrical circuit diagram in Figure 2, ammeters A1 and A2, variable resistor 15, and variable resistor 16 were arranged.

[0119] A voltage was applied between the first working electrode 31a and the second working electrode 32a and the counter electrode 18 to achieve a target voltage of 1.8V, and sterilization was performed. The sterilization device 10 controlled the current flowing between the first working electrode 31a and the second working electrode 32a and the counter electrode 18 so that the first current density and the second current density were the same. In each of wells 41 and 42, 5 mL of D-PBS(-) was taken every 20 minutes, and a new 5 mL of D-PBS(-) was injected. The pH of the taken D-PBS(-) was measured. The pH measurement results for the example are shown in Figure 9. The pH values ​​of the first working electrode 31a and the second working electrode 32a were approximately the same, and the changes over time were also similar.

[0120] (Comparative Example 1) As shown in Figure 7, Comparative Example 1 was obtained in the same manner as in the embodiment, except that the well 42 was not provided and the wiring connecting the second working electrode and the power supply unit 12 to the second working electrode was not provided. The first working electrode 31a is not connected in parallel with the second working electrode.

[0121] (Comparative Example 2) As shown in Figure 8, Comparative Example 2 was obtained in the same manner as in the embodiment, except that the well 41 was not provided and the wiring connecting the first working electrode and the power supply unit 12 to the first working electrode was not provided. The second working electrode 32a is not connected in parallel with the first working electrode.

[0122] Figure 10 shows the pH measurement results for Comparative Example 1 (first working electrode) and Comparative Example 2 (second working electrode). The pH of the second working electrode 32a increased at a faster rate than that of the first working electrode 31a and showed a higher value than that of the first working electrode 31a. It is considered that the rate of bactericidal substance generation in the second working electrode 32a is higher than that of the first working electrode 31a. This is thought to be because the electrical resistance of the Co-Cr-Mo alloy piece forming the second working electrode 32a is lower than that of the Ti-6Al-4V alloy piece forming the first working electrode 31a.

[0123] (Comparative Example 3) Comparative Example 3 was obtained in the same manner as in the Example, except that the control device 13 did not control the current flowing between the first working electrode 31a and the second working electrode 32a and the counter electrode 18 so that the first current density and the second current density were the same. The first working electrode 31a and the second working electrode 32a were electrically connected in parallel. The pH measurement results for Comparative Example 3 are shown in Figure 11. The pH of the first working electrode 31a increased compared to Comparative Example 1, but the pH of the second working electrode 32a was the same as in Comparative Example 2. This suggests that when two working electrodes with different electrical resistances are connected in parallel, the bactericidal effect of the two working electrodes differs significantly.

[0124] On the other hand, in the example, the pH values ​​of the two working electrodes with different electrical resistances were almost the same, and the changes over time were also similar, so it is presumed that a similar bactericidal effect can be obtained. Although the pH in the example is lower than that of the second working electrode in the comparative example, the pH can be increased by increasing the target voltage.

[0125] 10 Metal implant sterilization device 11 User interface 12 Power supply unit 13 Control unit 14 Communication line 21 Communication interface 22 Memory 23 Processor 231 Acquisition unit 232 Control unit 233 Determination unit 24 Signal line

Claims

1. A metal implant sterilization device that controls the current flowing between each of a first terminal electrically connected to a first working electrode and a second terminal electrically connected to a second working electrode having a different electrical resistance from the first working electrode, and a counter electrode, comprising: an acquisition unit that acquires a first indicator representing the sterilization action of the first working electrode electrically connected to the first terminal and a second indicator representing the sterilization action of the second working electrode electrically connected to the second terminal; and a control unit that controls the current flowing between each of the first terminal and the second terminal and the counter electrode, based on the first indicator and the second indicator, so that the sterilization action of the first working electrode electrically connected to the first terminal and the sterilization action of the second working electrode electrically connected to the second terminal are the same.

2. The metal implant sterilization apparatus according to claim 1, wherein each of the first working electrode and the second working electrode is an implant member constituting a metal implant.

3. The metal implant sterilization apparatus according to claim 1, wherein the first indicator is a first current density of the current flowing between the first terminal and the counter electrode, the second indicator is a second current density of the current flowing between the second terminal and the counter electrode, and the control unit controls the current flowing between the first terminal and the second terminal and the counter electrode so that the first current density and the second current density are the same.

4. The metal implant sterilization apparatus according to claim 1, wherein the first indicator is the amount of charge flowing between the first terminal and the counter electrode, the second indicator is the amount of charge flowing between the second terminal and the counter electrode, and the control unit controls the current flowing between each of the first terminal and the second terminal and the counter electrode so that the total amount of charge flowing between the first terminal and the counter electrode and the total amount of charge flowing between the second terminal and the counter electrode are distributed according to the area ratio of the respective electrodes.

5. The metal implant sterilization apparatus according to claim 1, wherein the first indicator is the first pH near the first working electrode, the second indicator is the second pH near the second working electrode, and the control unit controls the current flowing between the first terminal and the second terminal and the counter electrode so that the first pH and the second pH are the same.

6. The metal implant sterilization apparatus according to claim 1, wherein the first indicator is a first pH near the first working electrode, the second indicator is a second pH near the second working electrode, and the control unit controls the current flowing between the first terminal and the second terminal and the counter electrode such that the rate of change of the first pH per unit time and the rate of change of the second pH per unit time are the same.

7. A method for sterilizing a metal implant, comprising controlling the current flowing between each of a first terminal electrically connected to a first working electrode and a second terminal electrically connected to a second working electrode having a different electrical resistance from the first working electrode, and a counter electrode, wherein the sterilization device acquires a first index representing the sterilization action of the first working electrode electrically connected to the first terminal and a second index representing the sterilization action of the second working electrode electrically connected to the second terminal, and, based on the first and second indices, controls the current flowing between each of the first and second terminals and the counter electrode so that the sterilization action of the first working electrode electrically connected to the first terminal and the sterilization action of the second working electrode electrically connected to the second terminal are the same.

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