Intelligent screw capable of monitoring bone mechanical signals in real time

Abstract

The invention relates to an intelligent screw capable of monitoring bone mechanical signals in real time. The intelligent screw is composed of one or more passive wireless pressure sensors and a screw with a sensor mounting groove. The passive wireless pressure sensor is composed of a primary loop and a secondary loop which are coupled through an inductor. The primary loop comprises an LRC circuit packaged by Gr-PDMS, and the LRC circuit is composed of a spiral inductor, a snakelike variable resistor and a capacitor which are connected in parallel. As a fracture fixture, the intelligent sensor is mounted on the fracture fixture, mechanical data displayed by the intelligent sensor is transmitted to terminal equipment through a passive signal transmission technology, and a doctor can evaluate fracture healing and mechanical conditions by using the received data, so that the dependence on traditional imaging examination is reduced, and the medical cost is reduced; the medical treatment convenience is improved, and the life quality of patients is improved.

Description

Technical Field

[0001] This invention belongs to the field of medical device technology, and specifically relates to a smart screw that can monitor bone biomechanical signals in real time. Background Technology

[0002] Internal fixation in orthopedics is one of the important methods for treating fractures. Fracture healing typically uses plates and screws as internal fixation devices to aid bone healing. However, to ensure proper healing of the fracture site, patients need regular follow-up examinations, including physical examinations and imaging studies (such as X-rays). These examinations are not only time-consuming and resource-intensive but also increase patient inconvenience, especially given the limitations of remote monitoring. Furthermore, traditional imaging examinations may expose patients to ionizing radiation, which may pose health risks during long-term follow-up.

[0003] Currently, clinical healing standards rely on physician judgment and a series of physical examinations and imaging assessments. Due to the complexity of the fracture healing process and significant individual variability, existing methods cannot provide real-time, continuous data support, making it difficult to detect delayed or nonunion fractures early. Therefore, there is an urgent need to develop a fracture healing monitoring device that simplifies follow-up procedures, enables remote monitoring, and is non-invasive and radiation-free. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a smart screw that can monitor bone biomechanical signals in real time. The smart screw serves as a fixation device for fractures and is equipped with a smart sensor. The biomechanical data displayed by the smart sensor is transmitted to a terminal device through passive signal transmission technology. Doctors can use the received data to assess fracture healing and limb stress, thereby reducing reliance on traditional imaging examinations, lowering medical costs, improving the convenience of medical treatment, and improving the quality of life of patients.

[0005] This invention provides a smart screw capable of real-time monitoring of skeletal biomechanical signals. The smart screw consists of one or more passive wireless pressure sensors and a screw (LCP) containing a sensor mounting slot. The passive wireless pressure sensor consists of a primary circuit and a secondary circuit connected by inductive coupling. The primary circuit includes an LRC circuit encapsulated using Gr-PDMS material, which consists of a helical inductor, a serpentine variable resistor, and a capacitor connected in parallel.

[0006] Preferably, the Gr-PDMS material is prepared by dissolving polydimethylsiloxane in an organic solvent, then adding graphene for shear mixing, and then adding a curing agent for stirring.

[0007] Preferably, the doping concentration of the graphene is 0.1-3%.

[0008] Preferably, the LRC circuit is fabricated as follows: the LRC circuit is obtained by printing on the surface of a cylindrical flexible substrate (such as polyester PET), and electronic components are printed on the circumference of the rotating cylinder. The conductive tracks can be printed with ink. The spiral inductor adopts a single-layer thin-film square coil antenna design and uses conductive silver paste or carbon-based conductive ink as the resistive material. The capacitor uses an insulating material (such as polyimide PI) as the dielectric layer, and the capacitance value is designed by controlling the size and spacing of the conductive plates to manufacture the inductor-capacitor circuit. The conductive material (such as conductive silver paste) is printed on the inductor-capacitor circuit using printing technology to form a serpentine variable resistor.

[0009] Preferably, the LRC circuit is placed inside a mold, injected with Gr-PDMS encapsulation material, and dried in a vacuum drying oven to form a primary circuit.

[0010] Preferably, the screw is used to secure the primary circuit of the passive wireless implantable pressure sensor.

[0011] Preferably, the secondary circuit includes a reading inductor to measure the resistance change value through the resonant vibration of the primary circuit.

[0012] Preferably, the reading inductor is obtained by manufacturing a single-layer thin-film square copper coil using a photolithography process.

[0013] Preferably, the plurality of passive wireless pressure sensors are mounted on an LCP steel plate containing sensor mounting slots to monitor the strain in different areas of the steel plate or bone surface.

[0014] Beneficial effects (1) As a fixation device for fractures, the present invention is equipped with a smart sensor. The mechanical data displayed by the smart sensor is transmitted to the terminal device through passive signal transmission technology. Doctors can use the received data to assess fracture healing and limb stress, thereby reducing reliance on traditional imaging examinations, reducing medical costs, improving the convenience of medical treatment, and improving the quality of life of patients.

[0015] (2) The present invention uses Gr-PDMS for encapsulation, which not only has good biocompatibility, but also improves the sensitivity of the sensor. This material can significantly improve the response speed and detection accuracy while ensuring the stability and reliability of the sensor, thus ensuring the accuracy and real-time performance of the data.

[0016] (3) The present invention, through the multi-point sensor layout, can more accurately reflect the stress distribution at the fracture site and surrounding area, which helps to detect delayed healing or nonunion of fractures at an early stage. This high-precision data acquisition method can provide doctors with more detailed and accurate information, thereby enabling them to formulate more personalized treatment plans.

[0017] (4) This invention employs passive signal transmission technology, avoiding the risk of ionizing radiation in traditional imaging examinations, making fracture healing monitoring safer. This is especially important for patients undergoing long-term follow-up, as they may be exposed to higher radiation doses due to frequent imaging examinations.

[0018] (5) This invention implants the sensor and the steel plate together into the human body, and removes them together during the fixation removal surgery after fracture recovery, without the need for additional surgical steps, thus reducing the burden on the patient. This not only reduces surgical risks but also shortens the patient's recovery time and improves overall medical efficiency. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural diagram of the sensor inside the smart screw.

[0020] Figure 2 This is a schematic diagram showing the preparation process and packaging of Gr-PDMS, the primary circuit encapsulation material of this invention. Figure 3 This invention relates to a fixing method for installing an LRC primary circuit.

[0021] Figure 4 This invention relates to several screw configurations for installing an LRC primary circuit.

[0022] In the diagram, 100 is the serpentine variable resistor in the LRC circuit, 101 is the capacitor in the LRC circuit, 102 is the spiral inductor in the LRC circuit, 103 is the LRC primary circuit packaged with Gr-PDMS material, 104 is the hollow screw, 110 is the FJ300-S high-shear mixer, 111 is the heated magnetic stirrer, and 112 is the mold for packaging the LRC primary circuit. Detailed Implementation

[0023] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0024] Example 1 This embodiment provides a smart screw capable of real-time monitoring of bone biomechanical signals. The smart screw consists of one or more passive wireless pressure sensors and a screw (LCP) containing a sensor mounting slot. The passive wireless pressure sensor comprises a primary circuit and a secondary circuit connected by inductive coupling. The primary circuit includes an LRC circuit packaged in Gr-PDMS, which consists of a helical inductor, a serpentine variable resistor, and a capacitor connected in parallel. By fixing the primary circuit to the screw and electromagnetically coupling it with an external secondary circuit, the resistance changes detected by the passive wireless pressure sensor can be transmitted to an external device, thereby understanding the stress distribution on the bone surface and inside.

[0025] In this embodiment, the primary loop reference... Figure 1 As shown, the LRC circuit is composed of Gr-PDMS material encapsulation. The spiral inductor and capacitor elements are fabricated using photolithography, while the serpentine variable resistor is made by printing silver nanowires onto the pre-fabricated inductor-capacitor circuit using inkjet printing technology. When minute deformations occur, the serpentine variable resistor exhibits a corresponding resistance change, thus reflecting the strain. The entire LRC circuit is encapsulated in Gr-PDMS material to ensure its biocompatibility and sensitivity.

[0026] In this embodiment, the Gr-PDMS material preparation process is referenced. Figure 2 As shown, polydimethylsiloxane (PDMS) is dissolved in dichloromethane, graphite is added to the solution, and the mixture is sheared and mixed using an FJ300-S high-shear mixer. Then, a curing agent (curing agent to PDMS content ratio of 1:10) is added, and the mixture is stirred at 60°C for 1 hour in a heated magnetic stirrer to obtain the Gr-PDMS encapsulation material. Different graphene doping concentrations affect the hardness of the encapsulation material; a 2% doping concentration of Gr-PDMS material is preferred as it has a higher elastic modulus, which can improve sensor sensitivity. The LRC circuit is placed in a polytetrafluoroethylene mold, the prepared Gr-PDMS encapsulation material is poured in, and the mold is dried in a vacuum drying oven at 60°C for 3 hours to form the primary circuit.

[0027] In this embodiment, reference Figure 1 As shown, one or more primary circuits are housed inside the screw, with the ends sealed and secured with a cap. It can respond in real-time to stress changes on the bone surface and within the bone. As the fracture gradually heals, the vibration transmission capacity of the fracture site gradually increases. By applying vibration to one end of the fracture and using sensors mounted on the smart screw to monitor vibration transmission between the two ends of the fracture, the healing status of the fracture can be effectively assessed. Specifically, the passive wireless pressure sensor can capture subtle changes in the bone surface and interior caused by vibration and transmit this information wirelessly to external devices for analysis.

[0028] This embodiment diagnoses fracture healing based on vibration detection principles. When a doctor applies vibration to one end of the fracture, the vibration on the bone surface and internally causes minute deformations, resulting in changes in the serpentine resistance in the primary circuit, which in turn alters the resistance value in the LRC parallel circuit. In the early stages of fracture healing, the vibration transmission capacity is weak due to incomplete healing. At this time, the resistance in the primary circuit on the vibrating side will record a larger resistance change because that side bears more vibration energy; while on the side farther from the vibration source, the stress detected by the primary circuit is smaller due to insufficient vibration transmission, and the corresponding resistance change is also smaller. However, as the fracture healing process progresses, the vibration transmission capacity of the fracture area gradually increases. This means that even the primary circuit on the side farther from the vibration source can more accurately sense the stress changes induced by vibration, causing the resistance changes recorded by the sensors on both sides to tend to be consistent. This consistency reflects the recovery of the mechanical properties of the fracture site, indicating that the fracture is approaching complete healing.

[0029] This embodiment requires maintaining a constant distance between the primary and secondary circuits. In this case, the impedance phase of the system at the resonant frequency changes only with resistance. This change can be measured using an impedance phase analyzer connected to the secondary circuit. By comparing the impedance phase shifts at both ends of the fracture, the ability of the callus tissue to transmit vibrations can be assessed, thereby determining the fracture healing status.

[0030] Example 2 This embodiment provides a smart screw capable of real-time monitoring of bone biomechanical signals, including a passive wireless implantable pressure sensor system and an LCP steel plate with a sensor mounting slot. The sensor capacitance changes are transmitted to the outside world through electromagnetic coupling between a primary circuit mounted on the steel plate and a secondary circuit in the outside world, thereby revealing the stress distribution on the bone surface.

[0031] In this embodiment, the primary circuit is an LRC circuit packaged with Gr-PDMS material, the same as in Embodiment 1.

[0032] In this embodiment, the primary circuit mounting slot is embedded inside the hollow screw, as shown in the reference. Figure 3 As shown, this device is used to detect the load on the steel plate when the human body bears a load. Multiple smart screws can also be implanted simultaneously or in combination with other implants.

[0033] In this embodiment, by installing a sensor inside a hollow screw, the stress distribution on the hollow screw equipped with a passive wireless implantable pressure sensor system can be obtained. Because a smart screw is used to fix a fracture, in the early stages of fracture healing, the force under mechanical stimulation is mainly transmitted along the screw; in the middle stages of fracture healing, the force transmission gradually shifts from the screw to the bone; and in the late stages of fracture healing, the force is mainly transmitted along the bone. Therefore, during the fracture healing process, the amplitude of the real-time monitored mechanical signal fed back by the smart screw will gradually decrease with the mechanical stimulation of the affected limb.

[0034] In this embodiment, the healing process can be analyzed when the body is standing or under appropriate load. The hollow screw carrying the passive wireless implantable pressure sensor system deforms under stress, causing a change in the resistance of the primary circuit on the screw. This change in resistance in the LRC circuit is detected by a secondary circuit impedance phase analyzer, thus analyzing the load on the hollow screw. As the fracture heals, under the same load, the force on the hollow screw gradually shifts to the force on the human bone, resulting in a decrease in the sensor's resistance change. This allows for a mechanical assessment of fracture healing.

Claims

1. A smart screw capable of real-time monitoring of bone biomechanical signals, characterized in that: The smart screw consists of one or more passive wireless pressure sensors and a screw with a sensor mounting slot; the passive wireless pressure sensor consists of a primary circuit and a secondary circuit coupled inductively; the primary circuit includes an LRC circuit encapsulated using Gr-PDMS material, the LRC circuit consisting of a helical inductor, a serpentine variable resistor and a capacitor connected in parallel.

2. The smart screw according to claim 1, characterized in that: The Gr-PDMS material is prepared by dissolving polydimethylsiloxane in an organic solvent, then adding graphene for shear mixing, followed by adding a curing agent and stirring.

3. The smart screw according to claim 2, characterized in that: The doping concentration of the graphene is 0.1-3%.

4. The smart screw according to claim 1, characterized in that: The LRC circuit is fabricated as follows: the spiral inductor adopts a single-layer thin-film square coil antenna design and uses photolithography to manufacture copper coils; the capacitor uses metal as electrodes and insulating material as dielectric layer, and the capacitance value is designed by controlling the size and spacing of the conductive plates to manufacture the inductor-capacitor circuit; silver nanowires are printed on the inductor-capacitor circuit using inkjet printing technology to form a serpentine variable resistor.

5. The smart screw according to claim 1, characterized in that: The LRC circuit is placed in a mold, injected with Gr-PDMS encapsulation material, and dried in a vacuum drying oven to form a primary circuit.

6. The smart screw according to claim 1, characterized in that: The screw is used to secure the primary circuit of the passive wireless implantable pressure sensor.

7. The smart screw according to claim 1, characterized in that: The secondary circuit includes a reading inductor, which measures the resistance change by the resonance of the primary circuit.

8. The smart screw according to claim 7, characterized in that: The reading inductor is obtained by using photolithography to manufacture a single-layer thin-film square copper coil.

9. The smart screw according to claim 1, characterized in that: The aforementioned passive wireless pressure sensors are mounted on an LCP steel plate containing sensor mounting slots to monitor the strain in different areas of the steel plate or bone surface.

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