Spinal fixation device

Abstract

The application discloses a vertebral fixation device, which comprises a plurality of pedicle screws and a connecting rod connected with the pedicle screws. The connecting rod comprises a heating rod, a plurality of memory plastic wires capable of being deformed by heat and a plurality of support tubes arranged in sequence. Each memory plastic wire is spirally wound on the heating rod to form a core rod in cooperation with each other, the support tubes are sleeved outside the core rod, and the memory plastic wires are connected with the support tubes. The vertebral fixation device further comprises an electric heating mechanism for heating the heating rod, the temperature of the memory plastic wires changes, and the memory plastic wires are transformed between a first state and a second state. In the first state, the support tubes abut against each other. In the process of transforming to the second state, the distance between the support tubes gradually increases. The vertebral fixation device of the application solves the defect that the rigidity of a traditional connecting rod is not adjustable by optimizing the connecting rod from a solid alloy rod to a combination of the heating rod, the memory plastic wires and the support tubes.

Description

Technical Field

[0001] This invention relates to the field of medical devices, and more particularly to a spinal fixation device. Background Technology

[0002] Posterior spinal fixation is a commonly used surgical procedure in spinal surgery for various spinal diseases, including spinal deformities and degenerative spinal diseases.

[0003] Posterior spinal fixation typically uses a combination of pedicle screws, connecting rods, and transverse fixation rods to stabilize the spine.

[0004] However, in current posterior spinal fixation surgeries, the connecting rods used are typically solid alloy rods. Solid alloy rods usually have high rigidity, making them crucial for maintaining spinal stability. However, high-rigidity rods can significantly restrict the movement of the fixed segment (the range of vertebral bodies connected by internal fixation devices), such as lumbar rotation, which can hinder patients' daily lives. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention discloses a spinal fixation device with adjustable stiffness of its connecting rod to meet the daily needs of patients.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A spinal fixation device includes a plurality of pedicle screws and a connecting rod connected to each of the pedicle screws. The connecting rod includes a heating rod, a plurality of shape-memory plastic filaments that deform upon heating, and a plurality of sequentially arranged support tubes. The shape-memory plastic filaments are spirally wound around the heating rod to form a core rod. The support tubes are sleeved on the outside of the core rod, and the shape-memory plastic filaments are connected to the support tubes. The device also includes an electric heating mechanism for heating the heating rod. The temperature of the shape-memory plastic filaments changes and transitions between a first state and a second state. In the first state, the support tubes abut against each other. During the transition to the second state, the projected length of the shape-memory plastic filaments in the axial direction of the heating rod gradually increases, causing the distance between the support tubes to gradually increase.

[0008] Furthermore, the electric heating mechanism includes a control unit, a nano-triboelectric power generation unit electrically connected to the control unit, an electric heating unit controlled by the control unit, and a battery unit that supplies power to the electric heating unit; the nano-triboelectric power generation unit generates an electrical signal and transmits it to the control unit, and the control unit controls the change of the heating power intensity of the electric heating unit.

[0009] Furthermore, the nano-triboelectric power generation unit consists of an upper friction plate, a lower friction plate, and a limiting mechanism; after the upper friction plate and the lower friction plate are attached, the limiting mechanism restricts the upper friction plate and the lower friction plate to move only in a single direction; the friction between the upper friction plate and the lower friction plate generates an electrical signal.

[0010] Furthermore, the nano-triboelectric power generation unit comprises two units: a lateral power generation unit for generating a first electrical signal and a longitudinal power generation unit for generating a second electrical signal. The lateral and longitudinal power generation units have identical structures. The control unit includes a receiving unit and a comparison unit electrically connected to the receiving unit. The receiving unit receives the electrical signals generated by the lateral and longitudinal power generation units, and the comparison unit compares the strengths of the first and second electrical signals. If the strength of the first electrical signal is greater than or equal to that of the second electrical signal, the electric heating unit is controlled to execute a first heating power, and the memory plastic filament is in the second state. If the strength of the first electrical signal is less than that of the second electrical signal, the electric heating unit is controlled to execute a second heating power, and the memory plastic filament is in the first state. If the strengths of both the first and second electrical signals are zero, the electric heating unit is controlled to execute a third heating power, wherein the first heating power > the third heating power > the second heating power.

[0011] Furthermore, the nano-triboelectric power generation unit also includes a flexible tube, with the upper friction plate and the lower friction plate both fixed on the inner wall of the flexible tube, and the upper friction plate and the lower friction plate arranged opposite to each other.

[0012] Furthermore, during the transition between the first and second states, a portion of the memory plastic filament located within the support tube undergoes deformation.

[0013] Furthermore, the support tube includes a round tube and a connector fixed to the inner wall of the round tube, the connector being connected to the memory plastic filament.

[0014] Furthermore, the support tube includes a narrow tube and a wide tube, which are coaxially arranged and connected to each other, and the memory plastic filament is connected to the inner wall of the narrow tube; between adjacent support tubes, the narrow tube and the wide tube are nested and fitted together.

[0015] Furthermore, the first end of the circular tube is provided with a first inclined surface surrounding the outer wall of the circular tube, and the second end of the circular tube is provided with a second inclined surface surrounding the inner wall of the circular tube; between adjacent support tubes, the first inclined surface and the second inclined surface cooperate with each other.

[0016] Furthermore, the limiting mechanism includes a protrusion on the upper friction plate and a groove on the lower friction plate, wherein the protrusion and the groove cooperate with each other.

[0017] Compared with existing technologies, the beneficial effects of this invention are as follows: By optimizing the connecting rod from a solid alloy rod to one composed of a heating rod, shape memory plastic wires, and a support tube, the state of the shape memory plastic wires and support tube changes according to the temperature of the heating rod. This change in the state of the shape memory plastic wires and support tubes causes a change in the stiffness of the connecting rod. The different stiffnesses of the connecting rod meet the needs of patients undergoing posterior spinal internal fixation surgery in various scenarios, such as postoperative lumbar rotation and spinal support during sitting. This solves the defect of the non-adjustable stiffness of solid alloy rods. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the spinal fixation device in the first state of the memory plastic filament in this invention;

[0019] Figure 2 This is a schematic diagram of the spinal fixation device in the second state of the memory plastic filament in this invention;

[0020] Figure 3 This is a schematic diagram of the connecting rod structure when the memory plastic filament is in the second state in this invention;

[0021] Figure 4 This is a schematic diagram of the structure of the nano-triboelectric power generation unit in this invention;

[0022] Figure 5 This is a schematic diagram of the support tube structure when the support tube adopts the first structure in this invention;

[0023] Figure 6 yes Figure 5 Sectional view of section AA;

[0024] Figure 7 This is a schematic diagram of the support tube structure when the support tube adopts the second structure in this invention;

[0025] Figure 8 yes Figure 7 Sectional view of section BB.

[0026] In the picture:

[0027] 1 – Pedicle screw; 2 – Connecting rod; 2a – Heating rod; 2b – Memory plastic wire; 2c – Support tube; 2ca – Round tube fitting; 2cb – Connector; 2cc – Narrow tube; 2cd – Wide tube; 2ce – First inclined surface; 2cf – Second inclined surface; 2cg – Fixation zone; 2ch – Deformation zone; 3 – Upper friction plate; 4 – Lower friction plate; 5 – Flexible tube. Detailed Implementation

[0028] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0030] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. Furthermore, the technical features involved in the different embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] Posterior spinal fixation is a common surgical procedure in spinal surgery. It involves implanting pedicle screws, connecting rods, and other internal fixation devices at the back of the spine to achieve spinal stability, repositioning, and fusion. It is mainly used to treat various spinal diseases, such as spinal deformities and degenerative spinal diseases.

[0032] In traditional solid alloy connecting rods, the high rigidity of the rod is crucial for maintaining spinal stability, primarily ensuring good spinal support for surgical patients in sitting or standing positions. However, due to this high rigidity, its elastic modulus is much greater than that of bone tissue. Commonly used solid alloy metal rods, such as titanium alloys, have an elastic modulus of approximately 110 GPa, while the elastic modulus of the compact bone of the human spine is 11 to 13 GPa. Therefore, traditional solid alloy connecting rods may conflict with the normal physiological function of the spine, leading to a series of drawbacks, such as:

[0033] First, the high rigidity of solid alloy connecting rods significantly restricts the movement of the fixed spinal segments, causing the load originally borne by the fixed segments to be transferred to adjacent non-fixed segments (especially 1-2 segments above and below the fixed segment). That is, the mechanical load (such as compressive force and shear force) originally borne by the intervertebral discs, facet joints, and other structures of the fixed segments cannot be dispersed through the micromotion of the fixed segments themselves, but can only be transmitted to the adjacent non-fixed segments through the rigid internal fixation system.

[0034] Second, solid alloy connecting rods achieve stability of fixed segments through "rigid locking," but they completely restrict the physiological activities of that segment, such as flexion and extension of the lumbar spine.

[0035] To address the excessive stiffness of solid alloy connecting rods, published literature has explored the use of shape memory alloys (MMA) to fabricate connecting rods in a spring-like form. This maintains the connecting rod's support and flexibility, resulting in lower stiffness. While the elastic modulus of MMA is lower than that of alloys like titanium, it is still significantly higher than that of the cortical bone of the human spine. Furthermore, MMA is expensive. Additionally, medical devices made of MMA have an electroplated coating; long-term deformation may damage this coating, leading to the release of nickel ions and potential nickel poisoning. Moreover, there is a possibility that the spring could trap muscle when it expands.

[0036] In other literature, PEEK material is currently widely used in human implants. Although PEEK material has a certain degree of elasticity and sufficient compressive strength, connectors made solely of PEEK material suffer from poor bending resistance and insufficient fatigue strength.

[0037] To address the excessive stiffness of solid alloy connecting rods, this invention employs a composite material approach to create the connecting rod. Specifically, it utilizes shape memory plastics and alloy materials. Shape memory plastics (i.e., shape-memory plastics) function similarly to shape memory alloys, capable of deformation under temperature, and are less expensive, making them suitable for mass production. Furthermore, they avoid the nickel ion release associated with shape memory alloys, which could lead to poisoning in humans. However, the elastic modulus of shape memory plastics is lower than that of the cortical bone of the human spine, meaning that simple shape memory injection molding materials cannot meet the support requirements. Shape memory plastics can be made from shape memory polyurethane (SMPU) or shape memory polyesters (such as PLA and PCL).

[0038] like Figures 1 to 3 As shown, this invention discloses a spinal fixation device, comprising a plurality of pedicle screws 1 and connecting rods 2 connected to each pedicle screw 1. In use, the spinal fixation device of this invention fixes the pedicle screws 1 within the vertebral column, and the connecting rods 2 serve to connect the pedicle screws 1. Adjacent connecting rods 2 are typically connected by transverse connectors.

[0039] Unlike existing technologies, the connecting rod in this invention is not a solid, one-piece molded rod. Specifically, in this invention, the connecting rod 2 includes a heating rod 2a, several shape-memory plastic filaments 2b that deform upon heating, and several sequentially arranged support tubes 2c. The heating rod 2a is a metal rod, which can be made of titanium alloy or stainless steel, and mainly serves a supporting function to ensure that the rigidity of the entire connecting rod 2 is not too low. The shape-memory plastic filaments 2b are made of shape-memory plastic and deform upon heating. The support tubes 2c are sleeved around the heating rod 2a and the shape-memory plastic filaments 2b, protecting the support tubes 2c that are sleeved on the heating rod 2a, simulating the outer wall of a solid alloy connecting rod. When the pedicle screw 1 is connected and fixed to the connecting rod 2, the pedicle screw 1 is fixed to the outer wall of the support tube 2c. The material of the support tube 2c is preferably PEEK, but it can also be an alloy material. The following describes the structure and usage of the spinal fixation device of this invention in detail, assuming that the support tube 2c is made of PEEK.

[0040] Detailed, such as Figures 1 to 3 As shown. The memory plastic filaments 2b are spirally wound around the heating rod 2a to form a core rod, and the support tube 2c is sleeved on the outside of the core rod. The memory plastic filaments 2b are connected to the inner wall of the support tube 2c.

[0041] In order to achieve the deformation of the memory plastic filament 2b, the spinal fixation device of the present invention also includes an electric heating mechanism for heating the heating rod 2a. When the heating rod 2a is heated and the temperature rises, the heat will be conducted to the memory plastic filament 2b, and the temperature of the memory plastic filament 2b will change, causing the memory plastic filament 2b to switch between a first state and a second state.

[0042] like Figure 1 As shown, in the first state, the shape memory plastic filament 2b is in a fluffy state. At this time, the projected length of the shape memory plastic filament 2b in the radial direction of the connecting rod 2 is relatively long, while its projected length in the axial direction of the connecting rod 2 is relatively short. The supporting tubes 2c abut against each other. In the first state, due to the abutment between the supporting tubes 2c, the overall stiffness of the connecting rod 2 is high, approaching the stiffness of a traditional solid alloy connecting rod; at this time, the stiffness of the connecting rod 2 is at its maximum. The connecting rod 2 in the first state is mainly suitable for scenarios involving human walking, where the connecting rod 2 needs to have high stiffness to support the spine.

[0043] like Figure 2As shown, when the electric heating mechanism heats the heating rod 2a, the total length of the memory plastic filament 2b remains unchanged during the transition to the second state, but its shape gradually changes from a fluffy state to a straight state. That is, the memory plastic filament 2b gradually wraps tightly around the heating rod 2a. The projected length of the memory plastic filament 2b in the axial direction of the heating rod 2a gradually increases, while its projected length in the radial direction of the heating rod 2a gradually decreases. Since the memory plastic filament 2b is connected to the support tubes 2c, it causes the distance between the support tubes 2c to gradually increase. Figure 3 As shown, because there are gaps between the support tubes 2c, the connecting rod 2 in the second state has lower stiffness than the connecting rod 2 in the first state. When the memory plastic wire 2b reaches the second state, the distance between the support tubes 2c reaches its maximum value, and the stiffness of the connecting rod 2 is at its minimum. The connecting rod 2 in the second state is mainly suitable for scenarios where the human body turns over or twists its waist while sleeping.

[0044] Under normal physiological conditions, spinal stability depends on the coordinated action of bones, ligaments, and muscles. Muscles maintain posture and dynamic stability through continuous contraction, especially during activity, to counteract the load generated by external forces or changes in posture. Traditional high-stiffness connecting rod 2 completely restricts the movement of the fixed segment, preventing muscles from participating in stability regulation through natural contraction. In this case, adjacent segment muscles need to compensate by increasing their contraction force to maintain overall balance, leading to an abnormal increase in tension. However, the variable-stiffness connecting rod 2 can achieve relatively low stiffness, thus retaining some mobility of the fixed segment. This allows muscles to still participate in stability maintenance through physiological contraction, avoiding excessive compensation by adjacent segment muscles. The lower-stiffness connecting rod 2 can also share some of the load when the body twists or turns, reducing excessive tension on back muscles such as the erector spinae.

[0045] An intermediate state exists between the first and second states. In this intermediate state, the memory plastic filament 2b is between fluffy and straight. Although there are gaps between the support tubes 2c, they are not as large as those in the second state. Therefore, the stiffness of the connecting rod 2 in the intermediate state is less than that in the first state, but greater than that in the second state. This intermediate state is primarily designed for static human postures, such as sitting or lying down. In this static state, the stiffness of the connecting rod 2 is less than that of a traditional solid alloy connecting rod, thus reducing the static contraction of muscles to resist the fixed stiffness, thereby alleviating the continuous muscle tension and fatigue caused by maintaining a single posture for extended periods.

[0046] This invention optimizes the connecting rod 2 from a solid alloy rod to a component consisting of a heating rod 2a, a shape memory plastic wire 2b, and a support tube 2c. The cooperation between the shape memory plastic wire 2b and the support tube 2c makes the overall elastic modulus of the connecting rod 2 close to that of the compact bone of the human spine. The state of the shape memory plastic wire 2b and the support tube 2c changes according to the temperature of the heating rod 2a. By changing the distance between the support tubes 2c, the limitation of the non-adjustable stiffness of the solid alloy rod is solved. The change in the state of the shape memory plastic wire 2b and the support tube 2c causes a change in the stiffness of the connecting rod 2. The different stiffnesses of the connecting rod 2 meet the needs of patients undergoing posterior spinal internal fixation surgery in various scenarios, including postoperative lumbar rotation and spinal support during sitting.

[0047] In the spinal fixation device of the present invention, many technical features, such as the detailed structure of the electric heating mechanism and the shape of the support tube 2c, have multiple implementations. Below, for each of these technical features, one implementation is selected for detailed description, and the embodiment in which this implementation is located is referred to as this embodiment. Other implementations of the numerous features, such as the detailed structure of the electric heating mechanism, are referred to as other embodiments, which are briefly described below.

[0048] In this embodiment, the electric heating mechanism includes a control unit, a nano-triboelectric generator unit electrically connected to the control unit, an electric heating unit controlled by the control unit, and a battery unit that powers the electric heating unit. During use, the electric heating mechanism is implanted into the human body along with the pedicle screw 1 and the connecting rod 2. The battery unit uses a wirelessly rechargeable battery. When the human body moves, the nano-triboelectric generator units within the body rub against each other due to the movement of muscles and soft tissues. The nano-triboelectric generator units generate electrical signals, which are transmitted to the control unit. The control unit then controls the heating power intensity of the electric heating unit. The nano-triboelectric generator units act as sensors here, and the number of nano-triboelectric generator units is unlimited.

[0049] Multiple nano-triboelectric generating units can be installed. These units are implanted in different locations within the human body. When the body engages in various activities such as twisting the waist, the amount of movement between muscles and soft tissues in different locations varies, resulting in different electrical signals generated by the nano-triboelectric generating units. Each unit transmits its signal to a control unit, which then determines the current activity state of the body based on the received signals. This allows for targeted control of the heating power of the electric heating unit on the heating rod 2a, thereby adjusting the state of the connecting rod 2. This state can be either the first state, the second state, or a state between the first and second states, ultimately achieving stiffness adjustment of the connecting rod 2 to meet the varying stiffness requirements of different human activities.

[0050] The nano-triboelectric unit can also be configured to have only one unit, used solely for detecting human activity. It can be configured such that when the nano-triboelectric unit does not generate an electrical signal, the shape memory plastic filament 2b is in a first state, where the connecting rod 2 has maximum stiffness to ensure spinal support. When the nano-triboelectric unit generates an electrical signal due to human movement such as twisting the waist, the shape memory plastic filament 2b is in a second state, where the connecting rod 2 has minimum stiffness to facilitate human movement.

[0051] This invention, through the inclusion of a nano-triboelectric power generation unit, can determine the activity state of the human body and thus automatically adjust the stiffness of the connecting rod 2. In other embodiments, the electric heating mechanism may also consist of an electric heating unit, a battery unit that powers the electric heating unit, and a manual control unit. The manual control unit manually adjusts the heating power of the electric heating unit, thereby autonomously controlling the stiffness of the connecting rod 2.

[0052] In this embodiment, as Figure 4 As shown, the nano-triboelectric power generation unit consists of an upper friction plate 3, a lower friction plate 4, and a limiting mechanism. When the nano-triboelectric power generation unit is implanted in the human body, the upper friction plate 3 and the lower friction plate 4 adhere to each other, and the limiting mechanism restricts their movement to only one direction. With the movement of the human body, the upper friction plate 3 and the lower friction plate 4 rub against each other to generate electrical signals. This invention, through the setting of the limiting mechanism, ensures that the nano-triboelectric power generation unit only generates electrical signals when moving in a single direction.

[0053] The upper friction plate 3 and lower friction plate 4 can only move in one direction, primarily to determine the type of human activity. Taking the restriction that the upper friction plate 3 and lower friction plate 4 can only move laterally as an example: When twisting the waist, the movement between muscles and soft tissues is mostly lateral (horizontal), with a small amount moving in other directions. Therefore, when twisting the waist, the upper friction plate 3 and lower friction plate 4 easily generate friction with each other, thus generating an electrical signal. However, when a person walks, the movement between muscles and soft tissues is mainly vertical (height). Therefore, when a person walks, there is no significant movement between the upper friction plate 3 and lower friction plate 4, and no electrical signal is generated. Therefore, by setting up a limiting mechanism, the control unit can determine the mode of human activity by whether the nano-triboelectric generator generates an electrical signal. In other embodiments, when the number of nano-triboelectric generator units is sufficient, the limiting mechanism may not be required. Taking waist twisting as an example, nano-triboelectric units can be implanted in multiple locations on the waist, back, and legs. During waist twisting, the movement mainly occurs between the muscles and soft tissues of the waist, while there is almost no movement between the muscles and soft tissues of the back and legs. Therefore, the nano-triboelectric units located in the waist generate stronger electrical signals, while the nano-triboelectric units in the back and legs generate weaker electrical signals. By comparing the strength of these electrical signals, it is possible to determine whether the human body is performing waist twisting activities.

[0054] In this embodiment, for ease of surgical implantation, two nano-triboelectric power generation units are provided: a lateral power generation unit for generating a first electrical signal and a longitudinal power generation unit for generating a second electrical signal. Both the lateral and longitudinal power generation units are located close to the connecting rod 2, and their structures are identical. The control unit includes a receiving unit and a comparison unit electrically connected to the receiving unit. The receiving unit receives the electrical signals generated by the lateral and longitudinal power generation units, and the comparison unit compares the strengths of the first and second electrical signals.

[0055] In the horizontal power generation unit, the upper friction plate 3 and lower friction plate 4 are restricted to move only horizontally, while in the vertical power generation unit, they are restricted to move only vertically. The electric heating unit can execute three heating powers: a first heating power, a second heating power, and a third heating power. The heating intensity of these three heating powers, from strongest to weakest, is: first heating power, third heating power, and second heating power. Under the first heating power, the memory plastic wire 2b is in the second state; under the second heating power, the memory plastic wire 2b is in the first state; and under the third heating power, the memory plastic wire 2b is in an intermediate state. This ensures that the stiffness of the connecting rod 2a, under the heating of these three power powers, increases from weakest to strongest in the order of first heating power, third heating power, and second heating power.

[0056] The use of the lateral and longitudinal power generation units is primarily to determine three usage scenarios related to human activity. Patients who have undergone posterior spinal fixation surgery typically do not engage in strenuous activities; therefore, the following three usage scenarios generally meet postoperative needs. These three usage scenarios are: the first scenario, involving lumbar twisting movements such as turning over or twisting the waist while sleeping; the second scenario, involving walking while using the toilet; and the third scenario, involving static states such as sitting or lying down. The determination process for these three usage scenarios is as follows:

[0057] When the human body is stationary, since the body does not move, neither the horizontal nor the vertical power generation unit will generate friction, and therefore no electrical signal will be generated. Because the receiving unit does not receive an electrical signal, the control unit determines that the human body is stationary and controls the electric heating unit to execute the third heating power. At this time, the memory plastic wire 2b is in an intermediate state, there is a slight gap between the support tubes 2c, and the stiffness of the connecting rod 2 is in an intermediate state.

[0058] When the human body is twisting its waist, the muscles and soft tissues mainly move horizontally, with slight vertical movement or no vertical movement at all. Since the horizontal and vertical power generation units have the same structure, the displacement between the upper friction plate 3 and lower friction plate 4 in the horizontal power generation unit is greater than that in the vertical power generation unit. Therefore, the strength of the first electrical signal generated by the horizontal power generation unit is greater than the strength of the second electrical signal generated by the vertical power generation unit (if there is no vertical movement, the strength of the second electrical signal is zero). At this time, the receiving unit simultaneously receives a stronger first electrical signal and a weaker second electrical signal (the value of the second electrical signal may be zero). After the comparison unit determines that the first electrical signal is stronger than the second electrical signal, the control unit can predict that the human body is in a twisting state. Therefore, it controls the electric heating unit to execute the first heating power. Because the first heating power is strong, the temperature of the memory plastic wire 2b is high, and the memory plastic wire 2b is in the second state, while the stiffness of the connecting rod 2 is at its lowest. In some extreme conditions, human activity may also generate the first and second electrical signals. At this time, human activity is usually greater, so the connecting rod 2 also needs to have a lower stiffness. Therefore, in this state, the electric heating unit is also controlled to execute the first heating power.

[0059] When a person is walking, the muscles and soft tissues mainly move vertically, with slight or no horizontal movement. Similarly, during a twisting motion, the intensity of the second electrical signal generated by the longitudinal power generation unit is greater than the intensity of the first electrical signal generated by the transverse power generation unit (if there is no horizontal movement, the intensity of the first electrical signal is zero). After the comparison unit determines that the first electrical signal is stronger than the second, the control unit can predict that the person is walking. Therefore, it controls the electric heating unit to execute the second heating power. Because the second heating power is weak (it can be zero), the temperature of the memory plastic wire 2b is low, and the memory plastic wire 2b is in its first state, while the stiffness of the connecting rod 2 is at its highest.

[0060] Patients undergoing posterior spinal internal fixation surgery require bed rest. Activities such as using the toilet, walking, sitting, lying down, twisting the waist, and turning over in bed meet most of their daily needs. While there are other scenarios besides using the toilet and walking, such as standing, when the body is stationary, neither the first nor the second electrical signal is generated, and the stiffness of connecting rod 2 is not at its maximum. However, the human body actually requires connecting rod 2 to have maximum stiffness at this time, and the configuration of the transverse and longitudinal power generation units cannot meet the needs of standing. However, patients who have undergone posterior spinal internal fixation surgery typically cannot stand for extended periods, so there is no need to consider other scenarios such as standing, as the probability of such scenarios occurring is low.

[0061] This invention utilizes two nano-triboelectric power generation units—a transverse power generation unit and a longitudinal power generation unit—to automatically identify most common life scenarios encountered by patients undergoing posterior spinal internal fixation surgery during postoperative recovery, such as walking and sitting, and automatically adjust the stiffness of the connecting rod 2. In other embodiments, the number of nano-triboelectric power generation units can also be set to one or more as mentioned above.

[0062] In this embodiment, as Figure 4As shown, the nano-triboelectric unit also includes a flexible tube 5, which is made of polydimethylsiloxane (PDMS), an elastic polymer. The upper friction plate 3 and the lower friction plate 4 are both fixed to the inner wall of the flexible tube 5, and are positioned opposite each other. Before implantation, there is a gap between the upper friction plate 3 and the lower friction plate 4. After implantation, the upper and lower friction plates 3 and 4 are held together, and the flexible tube 5 becomes flatter than before implantation. Due to its elasticity, the upper and lower friction plates 3 and 4 can move relative to each other more easily, making it easier for the nano-triboelectric unit to generate electrical signals. Simultaneously, the flexible tube 5 also protects the upper and lower friction plates 3 and 4, facilitating implantation. In other embodiments, the flexible tube 5 can be omitted, and the upper friction plate 3 can be fixed to soft tissue, while the lower friction plate 4 can be fixed to muscle tissue.

[0063] In this embodiment, as Figure 4 As shown, the limiting mechanism includes a protrusion on the upper friction plate 3 and a groove on the lower friction plate 4. After the upper friction plate 3 and the lower friction plate 4 are fitted together, the protrusion and the groove cooperate, allowing the upper friction plate 3 and the lower friction plate 4 to move only along the axis of the protrusion. In other embodiments, the limiting mechanism can also be limiting blocks on both sides of the upper friction plate 3. The upper friction plate 3 and the limiting blocks together form a U-shaped object. After the upper friction plate 3 and the lower friction plate 4 are fitted together, the lower friction plate 4 is positioned in the recessed area of ​​the U-shaped object.

[0064] In this embodiment, during the transition between the first and second states, a portion of the memory plastic filament 2b located within the support tube 2c deforms. Specifically, since the memory plastic filament 2b needs to connect to the inner wall of the support tube 2c, it is typically fixed to the inner wall of the support tube 2c by adhesive bonding. However, the memory plastic filament 2b bonded to the support tube 2c is less prone to deformation with temperature changes. Therefore, most of the memory plastic filament 2b located within the support tube 2c cannot be bonded to the support tube 2c, facilitating deformation within the support tube 2c and making it easier for the support tubes 2c to be held together. In other embodiments, to enhance the connection strength between the memory plastic filament 2b and the support tube 2c, the memory plastic filament 2b located within the support tube 2c can be completely bonded to the support tube 2c. However, in this case, without external force, since the deformed memory plastic filament 2b is located outside the support tube 2c, it is difficult to ensure that the support tubes 2c can hold together. Therefore, it is necessary to set up additional memory plastic wires 2b to connect adjacent support tubes 2c. The deformation of memory plastic wires 2b pulls the support tubes 2c together to achieve mutual support.

[0065] In this embodiment, two structures of the support tube 2c are listed. The function of both structures is to ensure that when the support tubes 2c are in contact with each other, they are all coaxially aligned, thus forming a continuous circular rod. This makes the connecting rod 2 formed by connecting the support tubes 2c almost identical in appearance to a traditional solid alloy connecting rod, achieving a low-notch design. A low-notch design means less friction on the muscle, resulting in less irritation. The two structures of the support tube 2c are the first structure and the second structure.

[0066] In the first structure, such as Figure 5 and Figure 6 As shown, the support tube 2c includes a circular tube 2ca and a connector 2cb fixed to the inner wall of the circular tube 2ca. The connector 2cb is located in the middle of the circular tube 2ca and is connected to a memory plastic filament 2b. The connector 2cb can be annular, and the connector 2cb and the circular tube 2ca are arranged coaxially. Therefore, the central hole area of ​​the annular connector 2cb is the fixed area 2cg. The heating rod 2a and the memory plastic filament 2b pass through the fixed area 2cg, and each memory plastic filament 2b is bonded to the connector 2cb. The memory plastic filament 2b located in the fixed area 2cg cannot deform. The area inside the circular tube 2ca other than the fixed area 2cg is the deformation area 2ch. Since the memory plastic filament 2b in the deformation area 2ch is not connected to the circular tube 2ca, the memory plastic filament 2b can deform freely within the deformation area 2ch. When the heating rod 2a is arranged coaxially with the circular tube 2ca, the support tubes 2c change from a state with gaps between them to a state of mutual abutment. The support tubes 2c still easily maintain their coaxial arrangement, and they sequentially abut each other to form an elongated rod shape. Furthermore, during the mutual abutment process of the support tubes 2c, the memory plastic filaments 2b in the deformation zone 2ch abut against the inner wall of the circular tube 2ca, thus increasing the overall rigidity of the connecting rod 2 when the support tubes 2c abut against each other.

[0067] In the first structure, such as Figure 6 As shown, the first end of the circular tube 2ca has a first inclined surface 2ce surrounding the outer wall of the circular tube 2ca, and the second end of the circular tube 2ca has a second inclined surface 2cf surrounding the inner wall of the circular tube 2ca. The first inclined surface 2ce and the second inclined surface 2cf cooperate with each other between adjacent support tubes 2c. The arrangement of the first inclined surface 2ce and the second inclined surface 2cf makes it easier for the support tubes 2c to maintain a coaxial alignment when they change from a state with gaps between them to a state of mutual contact. In some other embodiments, the first inclined surface 2ce and the second inclined surface 2cf can also be replaced by protrusions and grooves.

[0068] In the second structure, such as Figure 7 and Figure 8As shown, the support tube 2c includes a narrow tube 2cc and a wide tube 2cd, which are coaxially arranged and interconnected. The memory plastic wire 2b is connected to the inner wall of the narrow tube 2cc. Between adjacent support tubes 2c, the narrow tube 2cc and the wide tube 2cd are nested together. During the assembly process of each support tube 2c, the narrow tube 2cc and the wide tube 2cd are nested together, and there is a gap between the outer wall of the narrow tube 2cc and the inner wall of the wide tube 2cd. At this time, the area inside the narrow tube 2cc is the fixed area 2cg, while the area inside the wide tube 2cd after removing the area occupied by the narrow tube 2cc is the deformation area 2ch. Regardless of how the memory plastic wire 2b deforms within the deformation area 2ch, the narrow tube 2cc always remains within the wide tube 2cd, but it will move within the wide tube 2cd as the memory plastic wire 2b deforms. When the memory plastic filament 2b is in the second state, the narrow tube 2cc is about to detach from the wide tube 2cd. Because there is a gap between the outer wall of the narrow tube 2cc and the inner wall of the wide tube 2cd, the connecting rod 2 can deform slightly by means of these gaps. However, when the memory plastic filament 2b is in the first state, the wide tubes 2cd of the adjacent support tubes 2c abut against each other, and the connecting rod 2 is difficult to deform at this time.

[0069] In other embodiments, the structure of the support tube 2c can also be a simple circular tube. However, in this case, during the mutual support process, misalignment can easily occur between the support tubes 2c, which can easily cause injury to the human body.

[0070] In summary, the spinal fixation device of the present invention solves the problem of the inability to adjust the stiffness of the solid alloy rod by replacing the solid alloy connecting rod with a heating rod 2a, a memory plastic wire 2b, and a support tube 2c. This is achieved by changing the distance between the support tubes 2c through temperature variations. Furthermore, the stiffness of the connecting rod 2 is automatically adjusted according to human activity through the inclusion of a nano-triboelectric power generation unit. A limiting mechanism restricting the upper friction plate 3 and lower friction plate 4 to movement in only one direction facilitates the determination of human activity patterns. The stiffness of the connecting rod 2 is automatically adjusted through the inclusion of transverse and longitudinal power generation units. The flexible tube 5 facilitates the generation of electrical signals by the nano-triboelectric power generation unit and protects the upper and lower friction plates 3 and 4. The memory plastic wire 2b located within the support tube 2c is mostly not bonded to the support tube 2c, allowing for easier bonding of the support tubes 2c together. Finally, the shape of the support tube 2c is defined to achieve a low-notch design for the connecting rod 2.

[0071] It should be emphasized that the above are merely preferred embodiments of the present invention and are not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A spinal fixation device, comprising a plurality of pedicle screws (1) and a connecting rod (2) connected to each of the pedicle screws (1), characterized in that, The connecting rod (2) includes a heating rod (2a), a plurality of memory plastic filaments (2b) that deform when heated, and a plurality of support tubes (2c) arranged in sequence. Each memory plastic filament (2b) is spirally wound around the heating rod (2a) to form a core rod. The support tube (2c) is sleeved on the outside of the core rod. The memory plastic filaments (2b) are connected to the support tube (2c). It also includes an electric heating mechanism for heating the heating rod (2a); the temperature of the memory plastic filament (2b) changes and transitions between a first state and a second state; In the first state, each of the support tubes (2c) abuts against each other; During the transition to the second state, the projected length of the memory plastic filament (2b) in the axial direction of the heating rod (2a) gradually increases, causing the distance between each of the support tubes (2c) to gradually increase; The electric heating mechanism includes a control unit, a nano-triboelectric power generation unit electrically connected to the control unit, an electric heating unit controlled by the control unit, and a battery unit that supplies power to the electric heating unit; the nano-triboelectric power generation unit generates an electrical signal and transmits it to the control unit, and the control unit controls the change of the heating power intensity of the electric heating unit.

2. The spinal fixation device according to claim 1, characterized in that, The nano-triboelectric power generation unit consists of an upper friction plate (3), a lower friction plate (4), and a limiting mechanism; After the upper friction plate (3) and the lower friction plate (4) are attached, the limiting mechanism restricts the upper friction plate (3) and the lower friction plate (4) to move only in a single direction; the friction between the upper friction plate (3) and the lower friction plate (4) generates an electrical signal.

3. The spinal fixation device according to claim 2, characterized in that, The nano-triboelectric power generation unit comprises two units: a lateral power generation unit for generating a first electrical signal and a longitudinal power generation unit for generating a second electrical signal. The lateral and longitudinal power generation units have identical structures. The control unit includes a receiving unit and a comparison unit electrically connected to the receiving unit. The receiving unit receives the electrical signals generated by the lateral and longitudinal power generation units, and the comparison unit compares the strengths of the first and second electrical signals. If the strength of the first electrical signal is greater than or equal to the strength of the second electrical signal, then the electric heating unit is controlled to perform the first heating power, and the memory plastic filament (2b) is in the second state; If the strength of the first electrical signal is less than that of the second electrical signal, the electric heating unit is controlled to perform the second heating power, and the memory plastic filament (2b) is in the first state; If both the strength of the first electrical signal and the strength of the second electrical signal are zero, then the electric heating unit is controlled to execute the third heating power. The first heating power > the third heating power > the second heating power.

4. The spinal fixation device according to claim 3, characterized in that, The nano-triboelectric power generation unit also includes a flexible tube (5), the upper friction plate (3) and the lower friction plate (4) are both fixed on the inner wall of the flexible tube (5), and the upper friction plate (3) and the lower friction plate (4) are arranged opposite to each other.

5. The spinal fixation device according to claim 1, characterized in that, During the transition between the first and second states, a portion of the memory plastic filament (2b) located within the support tube (2c) undergoes deformation.

6. The spinal fixation device according to claim 5, characterized in that, The support tube (2c) includes a round tube (2ca) and a connector (2cb) fixed to the inner wall of the round tube (2ca), the connector (2cb) being connected to the memory plastic filament (2b).

7. The spinal fixation device according to claim 5, characterized in that, The support tube (2c) includes a narrow tube (2cc) and a wide tube (2cd). The narrow tube (2cc) and the wide tube (2cd) are coaxially arranged and connected to each other. The memory plastic filament (2b) is connected to the inner wall of the narrow tube (2cc). Between adjacent support tubes (2c), the narrow tube (2cc) and the wide tube (2cd) are nested and fitted together.

8. The spinal fixation device according to claim 6, characterized in that, The first end of the circular tube (2ca) is provided with a first inclined surface (2ce) surrounding the outer wall of the circular tube (2ca), and the second end of the circular tube (2ca) is provided with a second inclined surface (2cf) surrounding the inner wall of the circular tube (2ca); between adjacent support tubes (2c), the first inclined surface (2ce) and the second inclined surface (2cf) cooperate with each other.

9. The spinal fixation device according to claim 3, characterized in that, The limiting mechanism includes a protrusion on the upper friction plate (3) and a groove on the lower friction plate (4), wherein the protrusion and the groove cooperate with each other.

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