Implantable bone fracture electrical stimulation method and apparatus

Abstract

This invention discloses an implantable fracture electrical stimulation method and device. The system consists of an external excitation device that generates an alternating electromagnetic field and a highly integrated implantable bone plate. The implantable device uses a medical-grade metal bone plate as its base. By integrating a platinum-iridium alloy energy receiving coil on the non-bone contact surface and encapsulating a miniature energy processing circuit within the bone plate chamber, it achieves a structural-functional integration of mechanical fixation and electrical stimulation. Its core technology lies in utilizing an LCL-LCL resonant network for wireless energy transmission. This ensures that even when tissue impedance dynamically changes during fracture healing, the system maintains a constant voltage output independent of the load, thereby precisely applying a stable electric field of approximately 100V / m to the lesion to promote osteoblast proliferation. Furthermore, the device integrates a Bluetooth monitoring module for real-time feedback on treatment status. This not only completely eliminates the infection risks associated with percutaneous leads and the lifespan limitations of built-in batteries, but also maintains the same shape and fixation method as traditional bone plates, significantly improving patient compliance and treatment safety without altering the surgeon's surgical habits.

Description

Technical Field

[0001] This invention belongs to the field of medical device and wireless power transmission technology, specifically relating to an implantable fracture electrical stimulation method and device for promoting bone tissue regeneration. Background Technology

[0002] In recent years, electrical stimulation has been shown to promote tissue healing and regeneration in animal experiments and clinical treatments.

[0003] Current methods of electrical stimulation mainly include: capacitive coupling, which generates an electric field and induces a weak current within the tissue by placing parallel electrode plates outside the body; minimally invasive electrode stimulation, which uses electrodes to perform electrical stimulation through a minimally invasive incision at the lesion; and pulsed electrical stimulation, which utilizes Faraday's law of electromagnetic induction to allow time-varying electromagnetic waves to pass through muscle tissue and bone cells, generating an induced eddy current electric field. These methods suffer from limitations in precisely applying the electric field to the lesion, and the minimally invasive approach carries the risk of secondary infection. Therefore, applying wireless energy transfer technology to tissue regeneration has become a significant research focus in the medical field.

[0004] In the field of tissue regeneration therapy, electrical stimulation technology has been widely proven to have significant therapeutic effects due to its ability to directly regulate the proliferation and differentiation of osteoblasts and muscle cells. However, traditional electrical stimulation protocols rely on percutaneous leads or implanted batteries for power, which have significant clinical limitations: the risk of infection caused by percutaneous leads forces patients to undergo repeated debridement surgeries, while the size and limited lifespan of built-in batteries not only increase the risk of foreign body reactions, but also require a second surgery to replace the battery after it is depleted, which greatly reduces patient compliance.

[0005] To address the current problems, there is an urgent need to propose a new method of electrical stimulation that can reduce the impact of secondary surgery and accurately and efficiently apply electromagnetic fields to the lesion site, thereby promoting the proliferation and differentiation of bone cells and muscle cells. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of existing technologies and propose an implantable fracture electrical stimulation method. This method highly integrates energy reception, electrical energy conversion, and electrical stimulation functions within the structure of a traditional bone setter. Through wireless energy transmission technology, it can provide stable and precise electrical stimulation to the bone healing site without the need for percutaneous leads and implanted batteries.

[0007] The core structure of the implantable fracture electrical stimulation method is a redesigned internal fixation plate. The plate integrates an energy receiving unit, an electrical stimulation generating unit, and at least one pair of stimulation electrodes. The plate is made of medical-grade titanium alloy or cobalt-chromium-molybdenum alloy and features an innovative integrated structural and functional design while retaining the mechanical support and fixation functions of traditional orthopedic bone plates.

[0008] The energy receiving unit is a coil tightly wound or printed on the non-bone contact surface of the bone plate body. The coil is completely encapsulated by a biocompatible material (such as medical silicone or polyimide), forming a robust integral structure with the bone plate body. The coil's wiring path has been optimized through electromagnetic simulation, and its trajectory is cleverly arranged around the screw holes used for fixation and the central circuit module housing to ensure that it can efficiently receive alternating electromagnetic field energy from outside the body while providing mechanical fixation.

[0009] The exciter includes a battery-powered module, an H-bridge inverter module, a resonant matching network, a transmitting coil, a monitoring module, and a Bluetooth module.

[0010] The bone plate body is equipped with a control chip compartment to house an integrated micro-control and stimulation generation circuit. This circuit is connected to the receiving unit and stimulation electrodes via wires, and is used to rectify, stabilize, and modulate the alternating current induced by the receiving unit to generate an electrical stimulation signal that meets the requirements of osteogenic bioelectricity.

[0011] The circuit module receiving compartment has a dedicated square groove or through hole in the central region of the bone plate body. The compartment's dimensions are precisely designed to accurately accommodate and secure a highly integrated, packaged circuit module. This design transforms the traditional external circuit module into an embedded structure, significantly reducing the overall size and thickness of the implant.

[0012] After assembly, the circuit module (including rectifier and voltage regulator components) is potted with biocompatible medical-grade silicone to form a robust, insulated, and moisture-proof independent module. This module is then embedded and fixed in the circuit module housing, and finally covered with a sealing cover plate by laser welding or biocompatible adhesive, so that its surface is flush with or slightly lower than the bone plate body to avoid additional irritation to the surrounding soft tissue.

[0013] The bone plate itself can serve as an electrode for electrical stimulation, or the output of the circuit processing can be connected to the bone plate via internal wires; alternatively, two independent electrodes, insulated from the bone plate, can be led out as stimulation contacts, or the fixation pins can be used directly. This ensures that electrical stimulation can be precisely applied to the bone healing area.

[0014] When the device is in operation, the exciter emits electromagnetic energy of a specific frequency (e.g., 450 kHz) into the body through its transmitting coil. An energy receiving unit implanted in the bone plate efficiently couples the magnetic field and generates an induced current. This current is processed by a resonant compensation network and rectifier / regulator circuit integrated within the circuit module housing, ultimately outputting a stable DC or pulsed voltage independent of changes in the load (bone tissue) impedance. This voltage is applied to the bone tissue through the bone plate body or dedicated electrode contacts, creating a favorable electric field environment that promotes osteoblast proliferation and differentiation.

[0015] This invention pioneers a new tissue regeneration treatment approach, achieving an innovative breakthrough in "structure-function integration." The platinum-iridium alloy coil, wound around the microgrooves on the surface of the titanium alloy bone plate, efficiently captures external magnetic field energy, which is then converted into precise electrical stimulation through a miniaturized rectification-stabilization module, completely eliminating the risk of infection associated with percutaneous channels.

[0016] The voltage regulator module includes a low-dropout linear regulator, which has fewer components and features low output voltage ripple and strong electromagnetic interference resistance, making it very suitable for voltage stabilization control of implantable devices.

[0017] The monitoring module includes temperature monitoring, voltage monitoring, and Bluetooth feedback modules, which can monitor the working status of the implantable wireless power transmission device in real time and provide feedback to ensure patient safety.

[0018] Optionally, the resonant matching network topology is LCL-LCL.

[0019] Furthermore, the coil wires are made of biocompatible, high-strength materials; Furthermore, the outer insulation layer of the coil conductor is made of polytetrafluoroethylene, which is resistant to corrosion by body fluids.

[0020] Furthermore, the filled material is installed in the screw holes of the bone plate or in the slots of the bone plate to reduce volume occupation, prevent additional protrusions from the wound, and improve the patient's experience.

[0021] In summary, the beneficial effects of the present invention are as follows: 1. This invention realizes a novel method of electrical stimulation, which involves wrapping a wire around a bone plate and implanting and removing it from the human body without additional surgery, reducing operational steps. As a wireless energy receiver, it can precisely apply an electromagnetic field to the lesion site. 2. The implantable electrical stimulation method of the present invention completely eliminates the risk of infection and activity restriction caused by percutaneous leads. Compared with traditional external electrical stimulation methods, it is more convenient and flexible in application scenarios. Patients only need to wear an external stimulator during rest to receive treatment, which greatly improves compliance and quality of life.

[0022] 3. The electrical stimulation method of the present invention can omit the step of measuring the wound impedance value before stimulation, because during the wound healing process, factors such as inflammation and mineralization of the tissue cause the wound impedance value to change dynamically. Thanks to its special electrical stimulation method, it can be guaranteed to be applicable throughout the entire wound healing process.

[0023] 4. This invention, through its implanted monitoring and Bluetooth module, compared to traditional electrical stimulation which can only monitor the electromagnetic parameters of the exciter, enables real-time monitoring of the electrodes, i.e., the lesion, during electrical stimulation. This ensures that the entire stimulation process is within a safe and controllable range and that the electromagnetic parameters of the electrical stimulation are within the optimal range, greatly promoting wound healing efficiency.

[0024] 5. The internal fixation bone plate of the present invention uses small-volume components to form an energy receiving unit, which is then encapsulated and installed in the opening of the bone plate, making reasonable use of excess volume without increasing the volume occupied by the implant; at the same time, the natural electromagnetic shielding effect of the titanium alloy hole wall suppresses most of the external electromagnetic interference.

[0025] 6. The internal fixation bone plate of this invention uses inert components and safe encapsulation technology, which can completely eliminate the risk of biotoxicity caused by long-term implant retention. The medical-grade polyetheretherketone shell and Parylene-C coating form a double ion permeability barrier. At the same time, the oxidation and corrosion rate of the inert ceramic-based components in the body fluid environment is close to zero. Combined with platinum-iridium alloy electrodes, the release of allergens is avoided from the material source. This design has been verified by triple testing of cytotoxicity, systemic toxicity and genotoxicity, which significantly reduces the interference of foreign body reaction on bone integration and avoids the risk of secondary surgery due to material degradation, providing a core guarantee for lifelong implantation.

[0026] 7. The shape and fixation method of the internal fixation plate described in this invention are basically the same as those of traditional bone plates. Surgeons do not need to change their existing surgical habits, making it easy to promote and apply in clinical practice. Attached Figure Description

[0027] The accompanying drawings of this invention are intended to provide a more intuitive and clear explanation of the technical content of the invention. As an integral part of the specification, the drawings, through graphical presentation, overcome the limitations of textual descriptions in demonstrating structural forms, connections, and operational processes, enabling those skilled in the art to more accurately and quickly understand the overall concept of the invention, the specific construction of each component, and their interactions, thereby fully grasping the essence of the invention's technical solution.

[0028] Figure 1 A method for implementing an implantable electrical stimulation device in a circumferential manner; Figure 2 This is a direct-facing implementation method for implantable electrical stimulation devices; Figure 3 A schematic diagram of the overall structure of an implantable electrical stimulation bone plate; Figure 4 This is a schematic diagram of the wireless power transfer circuit topology based on the LCL-LCL resonant network of the present invention; Figure 5 This describes the energy flow path during the use of this invention, as well as the related monitoring modules; Figure 6 This is a schematic diagram of the simulation model; Figure 7 This refers to the load voltage at the fracture wound site. Figure 8 The simulation results are shown in the figure. Figure reference numerals: 1. Medical bone plate body, 2. Screw hole, 3. Circuit module housing, 4. Energy receiving unit, 5. Tibia, 6. Muscle tissue, 7. Exciter; 1-1. Fractured tibia, 1-2. Internal fixation bone plate, 1-3. Electrical stimulation unit, 1-4. Fractured tibia, 2-1. Internal fixation bone plate, 2-2. Electrical stimulation unit, 2-3. Exciter, 2-4. Detailed Implementation

[0029] To clearly explain the research and development objectives, technical solutions, and core advantages of this invention, a detailed description will be provided below in conjunction with the accompanying drawings and specific embodiments. It should be clarified that the embodiments listed herein are merely for assisting in interpreting the technical content of this invention and are not intended to limit its scope of protection.

[0030] This embodiment describes in detail a specific method for preparing the implantable electrical stimulation bone plate: The bone plate substrate is made of medical-grade TA4 pure titanium or TC4 titanium alloy sheet, and is precision machined by CNC to form the bone plate body 1 of the required length and shape, and screw holes 2 are drilled. In the middle of the bone plate body 1, a square groove with a depth of 8mm is milled out as a circuit module housing 4.

[0031] The coil uses a 1mm diameter platinum-iridium alloy wire with a polytetrafluoroethylene (PTFE) insulation layer as the conductor. Automated precision winding equipment is used to tightly wind the conductor onto the surface of the bone plate body 1. The winding path is pre-optimized using electromagnetic simulation software (such as COMSOL Multiphysics) to ensure it surrounds the screw holes 2 and covers the treatment area, while simultaneously forming a receiving unit 3 with inductance meeting design requirements. After winding, biocompatible epoxy resin is used to fix the conductor to the bone plate surface.

[0032] Miniature components such as the receiving end resonant capacitor (ceramic capacitor, 0402 package) and the Schottky diode rectifier bridge (chip-scale package) are soldered onto a flexible printed circuit board (FPCB). This FPCB module is placed into the square recess, and its input terminals are soldered to the leads of coil 3. Subsequently, medical-grade silicone rubber is used for potting, filling the entire recess and completely covering the circuit module to form an integrated package structure.

[0033] A 0.2mm thick titanium alloy sheet is used as a cover plate and is welded to the groove using laser sealing welding to restore the surface of the bone plate to flatness. The output of the voltage regulator circuit is connected to the bone plate body 1 through internal wires to serve as the negative stimulation electrode; the positive stimulation electrode is connected to an independent spherical electrode contact made of platinum-iridium alloy, which is fixed to one end of the bone plate by an insulating support.

[0034] This embodiment illustrates how the entire device works in concert to achieve constant pressure stimulation: The external actuator generates a 450kHz high-frequency alternating current, which is transmitted through a transmitting coil. The energy receiving unit 3, implanted on the surface of the bone plate, couples the energy and, together with the resonant capacitor encapsulated within the chamber, forms an LCL resonant network. The parameters of this network are rigorously designed so that the output voltage of the system is independent of the load impedance at resonance. This voltage is applied between the bone plate body 1 (negative electrode) and the positive electrode of the spherical electrode contact, thereby creating a constant DC electric field of approximately 100V / m in the bone tissue, effectively promoting osteoblast proliferation.

[0035] This embodiment aims to provide a specific and feasible technical solution, and elaborates in detail how to implement the proposed implantable fracture electrical stimulation method and the use of the device.

[0036] The system consists of two parts: an external actuator and an implantable bone stimulation plate. The external actuator generates a high-frequency electromagnetic field through its H-bridge inverter circuit, LCL resonant network, and transmitting coil, wirelessly transmitting energy into the body. The implantable electrostimulation plate is one of the core components of this method. It is made of medical-grade metal, with an integrated energy receiving unit on its surface and built-in circuitry for energy processing. This design fundamentally eliminates the reliance on built-in batteries and solves the risks and costs associated with the additional surgery required for battery replacement in traditional implantable devices.

[0037] In the specific parameter design, we followed a rigorous process. First, we determined the system's operating specifications, such as setting the operating frequency to 450 kHz. Then, based on the physical dimensions of the bone plate and coil, we estimated the coil's inductance. Finally, according to the constant voltage output condition of the LCL-LCL resonant network, we calculated the specific parameters of the compensation network to ensure that the system achieves zero-phase operation in the resonant state, thereby providing a stable output. The generated electric field strength is approximately 100 V / m, an intensity that has been proven to have a positive effect on osteoblast proliferation. This embodiment, through this refined design, provides a solid technical foundation for addressing the clinical challenges of inconsistent parameters and difficulty in standardizing efficacy in existing electrical stimulation therapies. parameter numerical values parameter numerical values Operating frequency 450kHz Load impedance Parametric scanning Primary inductor current 20mA Zener capacitor 2.2uF Primary-side compensating inductor 108.32uH Secondary inductor 2.01uH Primary-side compensation capacitor 1.155nF Secondary side compensation capacitor 62.388nF Primary inductor 108.32uH Secondary compensation inductor 2.01uH

[0038] This embodiment aims to provide a simulation verification model. To verify the therapeutic effect of the implantable electrical stimulation method described in this invention, we established an accurate model of the bone plate, including the tibia, soft tissue, and integrated coil, using COMSOL Multiphysics simulation software. We then performed simulation analysis on its key parameters (shown in the table above). See attached... Figure 7 , 8 As shown, when the system operates at 450kHz, although the load impedance simulating bone tissue impedance varies over a wide range of 400 to 1800 Ω (covering the dynamic impedance changes during fracture healing from inflammatory edema to mineralization sclerosis), the output voltage across the load remains highly stable, with fluctuations well below 10%. This fully demonstrates that the resonant network used in this invention successfully achieves load-independent constant voltage output characteristics, ensuring the stability of energy supply.

[0039] Output stability is crucial for ensuring clinical efficacy. Bone healing is a lengthy process, and its tissue impedance changes significantly during the repair process. Studies have shown that effective osteogenic stimulation requires maintaining the electric field strength within a relatively narrow optimal window (approximately 10-100 V / m); too low a value is ineffective, while too high a value may cause inhibition. The constant voltage output characteristic of the device of this invention means that the electric field strength applied to the bone tissue will not attenuate due to impedance changes, thereby ensuring that the electrical stimulation signal remains above the effective treatment threshold throughout the entire treatment cycle. The electric field mode distribution is shown in the attached figure. Figure 4 (The field strength in the bone tissue region is 60-120 V / m) This conclusion corroborates the previous one, proving that the electrical stimulation method can produce effective stimulation and ensure its long-term stability under the current parameters.

[0040] Compared to traditional percutaneous electrical stimulation (PES) or internal battery-based PES, this invention exhibits significant advantages. Traditional methods suffer from inherent drawbacks such as difficulty in precisely reaching bone tissue with the electric field, the risk of infection due to percutaneous leads, and the need for secondary surgery to replace the battery. This invention, through the integrated design of wireless energy transmission technology and the bone plate's structure and function, fundamentally eliminates the risks associated with percutaneous channels and internal batteries. More importantly, simulation results, combined with the load-independent resonant circuit design of this invention, demonstrate that it can maintain a stable and effective stimulation electric field at the lesion site throughout the entire bone healing process (dynamic changes in tissue impedance), solving the clinical problem of inconsistent treatment effects caused by impedance changes or voltage attenuation in traditional methods. Therefore, this invention ensures treatment precision and safety while achieving stable and reliable stimulation parameters throughout the treatment course, providing a more advantageous active repair solution for fracture healing.

Claims

1. An implantable fracture electrical stimulation method and device, characterized in that, include: An external excitation device is used to generate an alternating electromagnetic field; An implantable device includes: a medical bone plate having at least two screw holes for receiving fixation screws; an energy receiving coil integrated on the medical bone plate for receiving the alternating electromagnetic field and generating an induced current; a circuit module receiving compartment disposed on the medical bone plate; an energy processing circuit disposed within the circuit module receiving compartment, the input terminal of which is electrically connected to the energy receiving coil for processing the induced current into a specific electrical stimulation signal; and a stimulation electrode electrically connected to the output terminal of the energy processing circuit for applying the electrical stimulation signal to the fracture site.

2. The implantable fracture electrical stimulation system as described in claim 1, characterized in that, The external stimulator is configured with different physical forms to adapt to different clinical anatomical sites; including but not limited to, a first form being a surround structure in which the stimulator is configured to be arranged around the limb; a second form being a face-to-face structure in which the stimulator is configured to be arranged face-to-face with the target area on the body surface; the system may also include other forms capable of realizing electrostimulation therapy.

3. The system according to claim 1, characterized in that, The implantable medical device is a bone plate used for internal fixation in orthopedics, and the bone plate body is made of a biocompatible metal material.

4. The system according to claim 2, characterized in that, The bone plate body integrates an energy receiving unit and an energy processing circuit. The energy receiving unit is a coil made of conductive material with several turns. The coil is wound or printed on the non-bone contact surface of the bone plate body in an embedded or surface micro-machining manner.

5. The implantable fracture electrical stimulation bone plate as described in claim 4, characterized in that, The surface of the bone plate body is provided with exposed or coated active material stimulation electrode contacts. The stimulation electrode contacts are electrically connected to the output terminal of the energy processing circuit to precisely apply electrical stimulation to the bone tissue.

6. The system according to claim 4, characterized in that, The winding path of the energy receiving unit is electromagnetically optimized to ensure that it can still achieve the highest receiving efficiency and generate an electric field distribution that is safe for the human body, even with the screw holes and circuit module housings on the bone plate in place.

7. The system according to claim 1, characterized in that, The energy processing circuit integrated within the implantable medical device includes a resonant capacitor, which together with the energy receiving coil forms a resonant network. This network enables the system to achieve load-independent constant voltage output at a specific frequency of wireless energy transmission, thereby providing stable electromagnetic physical quantities even when bone tissue impedance changes dynamically.

8. The system according to claim 1, characterized in that, The external actuator includes an H-bridge inverter circuit for converting direct current into high-frequency alternating current, and a transmitting coil for transmitting the alternating current into the body.

9. A method for obtaining electrical physical quantities wirelessly within the body to promote the healing of biological tissues, characterized in that, The method includes the following steps: a. Surgically fix the implanted device to the fracture site; b. The medical device generates a corresponding electrical stimulation signal via an external stimulator; c. Receive the electromagnetic energy through the energy receiving unit; d. The alternating current is processed by the circuit processing module into an electromagnetic physical quantity that remains stable within a preset target range, the physical quantity including but not limited to voltage or electric field strength; e. Apply the stable electrical physical quantity to the target tissue to provide a continuous and consistent therapeutic stimulus.

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