Non-fusion fixation device for cervical spine

Abstract

The application discloses a non-fusion fixing device for cervical vertebrae in the technical field of medical prosthesis manufacturing, which comprises upper and lower symmetrical end plates, a stabilizing assembly fixedly connected between the end plates, a free movement platform fixedly connected to the top of the stabilizing assembly and a stress buffering assembly fixedly connected to the outer periphery of the stabilizing assembly. The multi-layer structure of the stabilizing assembly and the free movement platform can ensure the stability of the cervical vertebra segment, prevent the injury of the spinal cord nerves, fully retain the activity of the cervical vertebra in each direction within the physiological range, absorb impact energy, shunt load and reduce the risk of adjacent segment degeneration through reasonable structural design, and the device has simple and reliable structure and meets the clinical application requirements.

Description

Technical Field

[0001] This invention belongs to the field of medical prosthesis manufacturing technology, specifically a non-fusion fixation device for the cervical spine. Background Technology

[0002] The cervical spine, as a crucial part of human movement, bears the important mission of supporting the head, ensuring stability and coordination, cushioning impacts on the spine and nerves, protecting blood vessels, and enabling diverse head movements. In the anatomical coordinate system, it can perform flexion, extension, rotation, and lateral flexion movements, and the degree of these movements is defined as cervical range of motion (CROM).

[0003] However, the cervical spine is often damaged due to factors such as trauma, deformity, and disease, leading to atlantoaxial instability and subsequent joint dysfunction. Patients may experience symptoms such as weakness in the limbs, limited neck movement, and difficulty with urination and defecation; in severe cases, it can even lead to paralysis and endanger life. Currently, posterior atlantoaxial bone grafting and internal fixation surgery is a commonly used clinical method for treating reduced atlantoaxial dislocation. This involves implanting a bone graft into the atlantoaxial joint and fixing it with cables, metal hooks, etc. Common fixation methods include the Gallie technique, Broos-Jenkins technique, Sonntag method, Halifax procedure, Apofix procedure, and Magerl procedure. However, these traditional methods have significant drawbacks, causing a substantial reduction or even complete loss of cervical spine mobility, severely impacting the patient's subsequent quality of life.

[0004] With the development of medical technology and patients' increasing demands for quality of life, non-fusion internal fixation systems, which install internal fixation systems but do not implant bone blocks, are gradually being used clinically due to their ability to provide sufficient stability and fewer complications. However, existing non-fusion internal fixation systems still have many shortcomings. For example, the posterior atlantoaxial restrictive internal fixator disclosed in Chinese Patent CN101601603B consists of pedicle screws, atlantoaxial connecting rods, axis connecting rods, and universal fixation rods. Although it preserves the rotation and lateral flexion functions of the atlantoaxial joint to a certain extent, the presence of the universal fixation rods greatly restricts the anteroposterior flexion and extension capabilities of the atlantoaxial joint, preventing patients from restoring normal atlantoaxial mobility. The atlantoaxial dislocation reduction internal fixation device disclosed in Chinese Patent CN106175897B, although it has relatively sliding grooves on the guide plate and adopts a gear and rack structure to ensure a certain range of normal mobility for the patient, has an overly complex structural design, and the range of motion is difficult to determine precisely. The atlantoaxial posterior dynamic fixation device disclosed in Chinese patent CN102225022A uses a universal joint lamina hook as its main structure. Although it can move on the ball head of the pedicle screw after installation and maintain some of the patient's original physiological functions, its relative movement is limited to the ball head and cannot meet the patient's need for a larger range of activities.

[0005] In conclusion, developing a non-fusion fixation device for the cervical spine that can ensure the overall stability of the atlantoaxial and cervical spine, fully preserve the normal range of motion in all directions of the cervical spine, and is simple and reliable in structure is of great clinical significance and an urgent practical need. Summary of the Invention

[0006] To address the aforementioned problems, the present invention aims to provide a non-fusion fixation device for the cervical spine. Through the multi-layered structure of the stabilizing components and the free-movement platform, it can ensure the stability of the cervical segments, prevent spinal cord nerve injury, and fully preserve the range of motion of the cervical spine in all directions within its physiological range. At the same time, through a reasonable structural design, it absorbs impact energy and diverts loads to reduce the risk of degeneration in adjacent segments. Moreover, the structure is simple, reliable, and meets the needs of clinical applications.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: a non-fusion fixation device for the cervical spine, comprising endplates arranged symmetrically at the top and bottom, a stabilizing component fixedly connected between the endplates, a free movement platform fixedly connected to the top of the stabilizing component, and a stress buffering component fixedly connected to the outer periphery of the stabilizing component.

[0008] The stabilizing component is used to achieve dynamic stability control of the cervical spine segments through graded stiffness adjustment. It provides flexible support within the physiological range of motion, achieves linear stiffness increase in the transitional range of motion, and triggers rigid restraint in the state of excessive activity to prevent spinal cord nerve injury.

[0009] The free motion platform is used to simulate the natural movement trajectory of the cervical spine and achieve multi-dimensional motion coupling. It coordinates the three-dimensional rotation of flexion, extension, rotation, and lateral flexion, as well as the three-dimensional translation of forward, backward, left, right, and up and down movements, to ensure motion coordination and reduce energy loss and bone interface damage during movement.

[0010] Stress buffer components are used to absorb impact energy and divert loads to reduce the risk of degeneration in adjacent segments. They absorb the energy generated by sudden external forces through compressive deformation and transfer loads to adjacent vertebrae through the bending deformation of auxiliary support structures, thereby reducing the stress on the core structure, dispersing stress concentration, and reducing the stress peak of adjacent vertebral endplates.

[0011] The basic principle of the design is to achieve non-fusion fixation of the cervical spine through the synergistic action of the endplates, stabilizing components, free-movement platform, and stress-buffering components. The upper and lower endplates provide the basic fixation interface; the stabilizing components provide structural support through the basic load-bearing layer, with spring hinges enabling graded stiffness adjustment, and protruding teeth triggering rigid limits during excessive movement, forming a three-level stabilization mechanism of "flexible support - increasing stiffness - rigid locking"; the free-movement platform simulates the natural movement trajectory of the cervical spine, achieving six-degree-of-freedom motion coupling; the stress-buffering components absorb impact energy and divert loads through the compression deformation of the energy absorption chamber and the bending deformation of the buffer wings, reducing the stress on the core structure and adjacent segments. Through mechanical connections and dynamic coordination, the components ensure cervical spine stability while preserving physiological range of motion, reducing the risk of sports injuries and degeneration.

[0012] The beneficial effects of the basic scheme are: 1. The graded stiffness adjustment mechanism of the stable component provides flexible support within the physiological range of activity to retain ≥90% of the natural range of motion, and triggers rigid limit to prevent spinal cord injury under the condition of exceeding the limit, which solves the problems of loss of mobility in traditional fusion fixation and insufficient stability of existing non-fusion devices.

[0013] 2. The free motion platform achieves six degrees of freedom motion through the coordination of three-dimensional rotation and translation, matching the natural motion trajectory of the cervical spine. The motion angle error is ≤0.5° and the displacement error is ≤0.3mm, reducing energy loss and bone interface damage during motion (average pressure of the endplate is ≤2MPa).

[0014] 3. The stress buffer assembly reduces the peak stress of the adjacent vertebral endplate by ≥25% through the energy absorption cavity (absorbing ≥10J of energy per millimeter of compression) and the buffer wing (transferring 15%-20% of the load).

[0015] 4. The wavy concave-convex layer of the endplate complements the anatomical morphology of the vertebral endplate, and the axial pull-out force of the barbed locking buckle is ≥500N to ensure that the device is firmly fixed; each component adopts a modular design, which is simple in structure and easy to surgically implant, and can be adapted to the differences in cervical spine anatomy of different patients.

[0016] Furthermore, the stabilizing component includes a base bearing layer, which is a mesh support. The bottom wall of the mesh support is circumferentially fixed with barbed buckles. The lower end plate has an annular groove, and the buckles are fixedly connected to the annular groove. The top outer wall of the mesh support has a movable annular groove, which is movably connected to the upper end plate.

[0017] The beneficial effects of the basic scheme are: 1. The basic bearing layer adopts a mesh support structure, combined with the circumferentially distributed barbed buckles and the fixed connection with the annular groove of the lower end plate, which can provide a stable support foundation for the whole device, ensure the connection strength between the device and the lower end plate, and reduce the risk of loosening.

[0018] 2. The movable annular groove on the top outer wall of the mesh support is movably connected to the upper endplate, which not only provides space for the movement of the upper endplate, but also constrains the range of movement of the upper endplate through the annular groove structure, so that the upper endplate can flexibly adjust its position with the movement of the cervical spine, while avoiding excessive displacement.

[0019] 3. The basic load-bearing layer provides an installation carrier and spatial support for the entire device through its own structural design, so that the graded stiffness adjustment function of the stabilizing components can be realized in an orderly manner, and the layers work together to ensure the dynamic stability of the cervical spine.

[0020] 4. The connection method of the barbed buckle and the annular groove, as well as the movable sleeve structure between the movable annular groove and the upper endplate, can better adapt to the anatomical shape and movement characteristics of the cervical spine, reduce stimulation to surrounding tissues, and improve the compatibility and safety of the device in the body.

[0021] Furthermore, the stabilizing component also includes several axially vertically distributed spring hinges. The top wall of the lower end plate is fixedly connected to the bottom end of the spring hinges. The top of each spring hinge is ball-jointed with the bottom wall of the free-moving platform. The spring hinges are all made of Ni-Ti alloy. The elastic modulus of the spring hinges is 10 GPa when the cervical spine flexion and extension movement is 0-25°. When the movement is 25-30°, the number of turns decreases and the stiffness increases linearly to 25 GPa.

[0022] The beneficial effects of the basic scheme are: 1. The Ni-Ti alloy spring hinge exhibits differentiated stiffness in different flexion and extension angle ranges. Through the combination of material properties and structural design, the dynamic adjustment of the stabilizing component is more in line with the physiological movement needs of the cervical spine, and the support strength is gradually enhanced while ensuring mobility.

[0023] 2. The top of the spring hinge is connected to the bottom wall of the free motion platform by a ball joint. Combined with the fixed connection between the bottom end and the end plate, it can not only stably transmit the load, but also provide a flexible connection fulcrum for the multi-dimensional movement of the free motion platform, ensuring that the motion platform can move smoothly with the cervical spine.

[0024] 3. The spring hinge achieves a linear increase in stiffness by reducing the number of turns in the 25-30° range, which can provide progressive mechanical feedback for cervical spine movement, help patients perceive the range of motion, indirectly guide the cervical spine to move within a safe range, and reduce the risk of excessive movement.

[0025] Furthermore, the stabilizing component also includes at least two sets of circumferentially arranged protruding teeth and locking grooves. The protruding teeth are all fixedly connected to the bottom wall of the free-moving platform, and the locking grooves are all opened on the inner side wall of the foundation bearing layer. When the cervical spine flexion and extension movement is greater than 30° or the rotation movement is greater than 45°, the protruding teeth are completely locked into the locking grooves to achieve rigid limiting.

[0026] The beneficial effects of the basic scheme are: 1. The circumferentially arranged tooth-locking groove structure triggers rigid limiting when the cervical spine flexion-extension movement is >30° or rotation movement is >45°. It directly restricts excessive movement through mechanical locking, avoids spinal cord nerve damage caused by excessive movement, and provides a clear safe movement boundary for the cervical spine.

[0027] 2. The tooth-locking groove structure complements the graded stiffness adjustment of the spring hinge. In the 0-30° flexion and extension range, the spring hinge achieves flexible control through stiffness changes. When the limit is exceeded, the rigid limit provides ultimate protection, making the dynamic stability control of the stabilizing component more comprehensive, covering physiological activities and dangerous conditions.

[0028] 3. The structure design with at least two sets of circumferential arrangement can simultaneously cope with excessive movement in the flexion, extension and rotation directions. No matter which direction the cervical spine moves excessively, it can effectively limit the movement through the engagement of the corresponding teeth and locking grooves, adapting to the protection needs of multi-dimensional cervical spine movement.

[0029] Furthermore, the free motion platform includes a base, with a spring hinge ball joint on the bottom wall of the base, and a bushing fixedly connected to the top wall of the base. The bushing is made of silicone material, and a horizontal slide rail and a vertical slide rail are fixedly connected to the top wall of the bushing. A horizontal slider and a vertical slider are symmetrically slidably fitted on both the horizontal and vertical slide rails. A buffer pad is fixedly connected to the side wall of the sliding axis of both the horizontal and vertical sliders. Thread grooves are opened on both sides of both the horizontal and vertical slide rails. A shape memory alloy wire is fixedly connected to both sides of both the horizontal and vertical sliders. The other end of the shape memory alloy wire passes through the corresponding thread groove and is fixedly connected to the bushing. The preset phase change temperature of the shape memory alloy wire is 37°C.

[0030] The beneficial effects of the basic scheme are: 1. The horizontal and vertical slide rails are set perpendicularly and intersecting each other. With the symmetrical sliding of the horizontal and vertical sliders, translational movements in the front-back and left-right directions can be realized. Combined with the ball joint connection between the base and the spring hinge, it provides a basis for three-dimensional rotation and simulates the natural movement trajectory of the cervical spine, ensuring the coordination and smoothness of the movement.

[0031] 2. The shape memory alloy wire deforms as the slider slides. At 37°C, it can undergo a phase transition according to the stress change corresponding to the amplitude of movement. It can adjust its own stiffness to adapt to different motion states and maintain appropriate flexibility within the range of physiological activity, providing stable mechanical feedback for the slider to slide.

[0032] 3. The buffer pad on the axial sidewall of the slider can reduce the impact of collision between the slider and the slide rail, and reduce the risk of damage to the bone interface; the wire groove guides the shape memory alloy wire, ensuring that the wire is subjected to uniform force and avoiding structural failure caused by wire deviation.

[0033] 4. The silicone bushing has good elasticity and biocompatibility, which can provide a stable installation base for the slide rail and shape memory alloy wire, and can also buffer part of the motion load through its own deformation, thereby improving the compatibility between the device and human tissue and reducing foreign body reaction.

[0034] Furthermore, the free motion platform also includes articulated ball joints, which contact the bottom wall of the upper endplate. The bottom wall of the articulated ball joints is hinged with three connecting rods that are inclined at an angle of 30° to the axial direction, and the angle between the connecting rods is 120°. The bottom ends of the two connecting rods corresponding to the transverse slide rail are respectively hinged to the transverse slider through fisheye bearings. The other connecting rod corresponds to the longitudinal slide rail. A connecting shaft is fixedly connected between the longitudinal sliders. The connecting rod corresponding to the longitudinal slide rail is hinged to the connecting shaft through fisheye bearings.

[0035] The beneficial effects of the basic scheme are: 1. The joint ball is in contact with the bottom wall of the upper endplate and can rotate flexibly with the movement of the upper endplate, accurately transmitting the complex movement of the cervical spine to the connecting rod; the connecting rod is at a 30° angle to the axis and is distributed at 120° to each other, forming a symmetrical and stable triangular force transmission structure, ensuring that the force is evenly distributed during the transmission process and reducing local stress concentration.

[0036] 2. Two connecting rods correspond to the horizontal slider, and one connecting rod corresponds to the vertical slider via a connecting shaft. Combined with the hinge method of the fisheye bearing, it allows for a small swing between the connecting rod and the slider, so that the sliding motion of the horizontal and vertical slide rails can work together to achieve precise coupling of multi-dimensional movements such as cervical spine flexion, extension, rotation, and lateral flexion, and better simulate the natural movement trajectory.

[0037] 3. The design of the fisheye bearing provides a buffer compensation space for the relative movement of the connecting rod and the slider, which can eliminate the interference caused by the coordinated movement of multiple parts, ensure that the components of the free movement platform can move smoothly when the cervical spine is performing complex movements, and at the same time reduce the traction on surrounding tissues and improve the compatibility of the device with human movement.

[0038] Furthermore, the stress buffer assembly includes several energy absorption cavities within the foundation bearing layer. The energy absorption cavities are distributed in a ring shape, and each energy absorption cavity has an opening facing the spring hinge. The interior of each energy absorption cavity is filled with a porous polyurethane material with a porosity of 80%.

[0039] The beneficial effects of the basic scheme are: the annular energy absorption cavity is filled with a porous polyurethane material with high porosity, which can absorb the sudden impact energy generated during cervical spine movement through the compression deformation of the material itself, reducing the direct impact of external forces on the core structure and surrounding tissues, and playing a buffering and protective role.

[0040] Furthermore, the stress buffer assembly also includes several buffer winglets, all of which are fixedly connected to the side wall of the end plate via flexible hinges. The flexible hinges are made of titanium alloy. The ends of the buffer winglets are provided with pads, which are bonded to the adjacent vertebrae. After the pads are bonded to the adjacent vertebrae, the pretension is 10-15N.

[0041] The beneficial effects of the basic scheme are: 1. The buffer wing is bonded to the adjacent vertebrae through the padding layer, which can transfer part of the load borne by the core structure to the adjacent vertebrae, reduce the stress burden on the stabilizing components and endplate, reduce the stress concentration of the core structure, and thus reduce the risk of bone interface damage.

[0042] 2. The flexible hinge is made of titanium alloy and has good elastic deformation capability. When the cervical spine is impacted or undergoes large-amplitude movement, the buffer wing can absorb energy through the bending deformation of the flexible hinge. Combined with the energy absorption cavity, it further enhances the overall buffering performance of the device and reduces the impact of sudden external forces on the cervical spine.

[0043] 3. The pre-tension setting after connection ensures that the buffer wing is always kept in a moderate tension state, which ensures the stability of the connection with the adjacent vertebrae without restricting the normal physiological activities of the cervical spine.

[0044] Furthermore, several locking screws are circumferentially distributed along the edges of the end plate.

[0045] The beneficial effects of the basic approach are: enhanced fixation strength between the endplate and the vertebral body: the locking screws distributed circumferentially at the edge of the endplate can be obliquely inserted into the vertebral bone, and the mechanical anchoring effect between the endplate and the vertebral body is enhanced through multi-angle engagement, which significantly improves the fixation stability of the device in the body and reduces the risk of loosening or displacement after surgery.

[0046] Furthermore, the contact surfaces of the endplate and the cervical vertebra are provided with wavy concave-convex layers, which complement the anatomical morphology of the cervical vertebral endplate.

[0047] The beneficial effects of the basic design are: the wavy, concave-convex layer complements the anatomical morphology of the cervical vertebral endplate, increasing the contact area between the endplate and the vertebral body, resulting in a tighter fit, reducing relative slippage, enhancing the initial fixation effect of the device in the body, and lowering the risk of postoperative displacement. The complementary anatomical design allows for even load distribution between the endplate and the vertebral body, avoiding localized stress concentration caused by poor fit, protecting the vertebral endplate and surrounding bone tissue, and reducing the possibility of bone resorption or osteolysis. Attached Figure Description

[0048] Figure 1 This is an isometric view of a non-fusion fixation device for the cervical spine in an embodiment of the present invention.

[0049] Figure 2 This is a side sectional view of a non-fusion fixation device for the cervical spine in an embodiment of the present invention.

[0050] Figure 3 This is a top sectional view of the energy absorption cavity of the non-fusion fixation device for the cervical spine in an embodiment of the present invention.

[0051] Figure 4 This is a top sectional view of the longitudinal slide rail of the non-fusion fixation device for the cervical spine in an embodiment of the present invention.

[0052] Figure 5 This is a top sectional view of the joint ball component of the non-fusion fixation device for the cervical spine in an embodiment of the present invention.

[0053] Figure 6 for Figure 2 Enlarged view of part A in the middle.

[0054] The reference numerals in the accompanying drawings include: 1. Screw; 2. Endplate; 3. Mesh bracket; 4. Buffer wing; 5. Annular groove; 6. Lock; 7. Energy absorption chamber; 8. Porous polyurethane material; 9. Opening; 10. Locking groove; 11. Base; 13. Movable annular groove; 14. Joint ball; 15. Bushing; 16. Protruding tooth; 17. Spring hinge; 18. Transverse slide rail; 19. Transverse slider; 20. Longitudinal slide rail; 21. Shape memory alloy wire; 22. Coupling; 23. Connecting rod; 24. Wire groove. Detailed Implementation

[0055] The following detailed description illustrates the specific implementation method:

[0056] Example 1

[0057] The basics are as follows: Figures 1 to 6 As shown: A non-fusion fixation device for the cervical spine includes endplates 2 arranged symmetrically at the top and bottom, a stabilizing component fixedly connected between the endplates 2, a free-moving platform fixedly connected to the top of the stabilizing component, and a stress buffer component fixedly connected to the outer periphery of the stabilizing component.

[0058] The stabilizing component is used to achieve dynamic stability control of the cervical spine segments through graded stiffness adjustment. It provides flexible support within the physiological range of motion, achieves linear stiffness increase in the transitional range of motion, and triggers rigid limit in the state of excessive activity to prevent spinal cord injury. The stabilizing component includes a basic support layer, which is a mesh support 3. The bottom wall of the mesh support 3 is circumferentially fixed with barbed buckles 6. The lower endplate 2 has an annular groove 5, and the buckles 6 are all fixedly connected to the annular groove 5. The top outer wall of the mesh support 3 has a movable annular groove 13, which is movably sleeved with the upper endplate 2. The stabilizing component also includes several axially vertically distributed spring hinges 17. The top wall of the lower end plate 2 is fixedly connected to the bottom end of each spring hinge 17. The top ends of each spring hinge 17 are ball-jointed with the bottom wall of the free-movement platform. The spring hinges 17 are all made of Ni-Ti alloy. The elastic modulus of the spring hinges 17 is 10 GPa when the cervical spine flexion-extension movement is 0-25°. When the cervical spine flexion-extension movement is 25-30°, the number of turns decreases and the stiffness increases linearly to 25 GPa. The stabilizing component also includes at least two sets of circumferentially arranged protrusions 16 and locking grooves 10. The protrusions 16 are all fixedly connected to the bottom wall of the free-movement platform. The locking grooves 10 are all opened on the inner side wall of the foundation bearing layer. When the cervical spine flexion-extension movement is >30° or the rotation movement is >45°, the protrusions 16 are completely engaged with the locking grooves 10 to achieve rigid limiting.

[0059] The free motion platform is used to simulate the natural movement trajectory of the cervical spine and achieve multi-dimensional motion coupling. It coordinates flexion, extension, rotation, and lateral flexion in three-dimensional rotation, as well as anterior-posterior, lateral, and posterior-inferior, and lateral-inferior, vertical-vertical translation, ensuring motion coordination and reducing energy loss and bone interface damage during movement. The free motion platform includes a base 11, with a ball joint between the bottom wall of the base 11 and a spring hinge 17. A bushing 15, made of silicone, is fixedly connected to the top wall of the base 11. Perpendicularly intersecting transverse slide rails 18 are fixedly connected to the top wall of the bushing 15. The longitudinal slide rail 20, the transverse slide rail 18, and the longitudinal slide rail 20 are all symmetrically fitted with transverse sliders 19 and longitudinal sliders. The sliding axial sidewalls of the transverse sliders 19 and longitudinal sliders are fixedly connected with buffer pads. The transverse slide rail 18 and the longitudinal slide rail 20 are both provided with wire grooves 24. The transverse sliders 19 and the longitudinal sliders are both fixedly connected with shape memory alloy wires 21. The other end of the shape memory alloy wires 21 passes through the corresponding wire grooves 24 and is fixedly connected to the bushings 15. The preset phase change temperature of the shape memory alloy wires 21 is 37°C. The free motion platform also includes an articulated ball joint 14, which contacts the bottom wall of the upper endplate 2. The bottom wall of the articulated ball joint 14 is hinged with three connecting rods 23 inclined at an angle of 30° to the axial direction, and the angle between the connecting rods 23 is 120°. The bottom ends of two connecting rods 23 corresponding to the transverse slide rail 18 are respectively hinged to the transverse slider 19 through fisheye bearings. The other connecting rod 23 corresponds to the longitudinal slide rail 20. A connecting shaft 22 is fixedly connected between the longitudinal sliders. The connecting rod 23 corresponding to the longitudinal slide rail 20 is hinged to the connecting shaft 22 through fisheye bearings.

[0060] Stress buffer components are used to absorb impact energy and divert loads to reduce the risk of degeneration in adjacent segments. They absorb the energy generated by sudden external forces through compressive deformation and transfer loads to adjacent vertebrae through the bending deformation of auxiliary support structures, thereby reducing the stress on the core structure, dispersing stress concentration, and reducing the stress peak of adjacent vertebral endplates.

[0061] Several locking screws 1 are distributed circumferentially along the edge of the endplate 2. The contact surface between the endplate 2 and the cervical vertebra is provided with a wavy concave-convex layer, which is complementary to the anatomical shape of the cervical vertebral endplate.

[0062] The specific implementation process is as follows: After the cervical spine is implanted with a non-fusion fixation device, the various components that move with the cervical spine will work together. The upper and lower endplates 2, through their wavy concave-convex layers, complement each other with the anatomical shape of the cervical vertebral endplates, forming an initial stable contact. The locking screws 1 at the edge of the endplate 2 are inserted obliquely into the vertebral body at a 15° angle, and mechanical anchoring is used to strengthen fixation and prevent the overall displacement of the device. When the cervical spine produces flexion, extension, rotation, and other movements, the upper endplate 2 moves synchronously with the upper vertebral body, and its bottom wall contacts the joint ball joint 14 of the free movement platform, transmitting the motion force to the free movement platform. The lower endplate 2, through its rigid connection with the stabilizing component, maintains relative fixation with the lower vertebral body, forming a motion reference. Figure 1 and Figure 2 As shown.

[0063] The stabilizing components employ graded dynamic stabilization control. The mesh support 3 of the base bearing layer is rigidly connected to the annular groove 5 of the lower endplate 2 via barbed latches 6, providing a support frame for the overall structure. The top movable annular groove 13 is movably fitted with the upper endplate 2, allowing the upper endplate 2 to slide and rotate slightly along the groove, while limiting excessive offset through the sidewalls of the groove. The spring hinge 17 undergoes adaptive stiffness adjustment. When the cervical spine flexion-extension angle is within the physiological range of 0-25°, the Ni-Ti alloy spring hinge 17 provides flexible support with an elastic modulus of 10 GPa, undergoing bending deformation with the swing of the free-moving platform. Absorbing part of the load and ensuring flexibility of movement, when the angle increases to the transition range of 25-30°, the number of turns of the spring hinge 17 decreases, resulting in a linear increase in stiffness to 25GPa. This increases deformation resistance, providing mechanical feedback to the human body in anticipation of exceeding limits. When the angle exceeds 30°, the convex tooth 16-locking groove 10 structure is triggered. The convex tooth 16 on the bottom wall of the free-moving platform engages with the platform's swing and locks into the locking groove 10 on the inner side wall of the foundation bearing layer, achieving rigid limitation through mechanical locking. Similarly, when the rotation angle exceeds 45°, the circumferentially arranged convex tooth 16-locking groove 10 will also engage, preventing dangerous movements that could compress the spinal cord. Figure 3 and Figure 4 As shown.

[0064] The free-motion platform achieves multi-dimensional motion coupling. The slide rail and slider coordinate translation. When the cervical spine translates forward and backward, the upper endplate 2 pushes the corresponding connecting rod 23 through the articulated ball joint 14. The connecting rod 23 drives the transverse slider 19 to slide along the transverse slide rail 18. When translating left and right, the longitudinal slider slides along the longitudinal slide rail 20. The connecting shaft 22 ensures that the two longitudinal sliders move synchronously. When the slider slides, the memory alloy wires 21 on both sides are in a stable austenitic state at a human body temperature of 37°C. With the slider being stretched or compressed, they provide a reverse constraint force through their own elastic deformation. The buffer pad reduces the impact of collision between the slider and the end of the slide rail. The connecting rod 23 and the joint conduct rotational transmission. When the cervical spine rotates, the articulated ball joint 14 rotates with the upper endplate 2. The three wires are arranged in a 12-degree angle. The 0° angled connecting rod 23, through the multi-angle movement characteristics of the fisheye bearing, decomposes the rotational force into the reverse sliding of the transverse slider 19 and the lateral sliding of the longitudinal slider. Combined with the ball joint rotation of the base 11 and the spring hinge 17, it achieves the coupling of three-dimensional rotation and translation. For example, during left lateral flexion, the left connecting rod 23 is compressed, pushing the transverse slider 19 to the left; the right connecting rod 23 is pulled, causing the slider to move to the right. Simultaneously, the spring hinge 17 is compressed and bent on the left and stretched on the right, working together to complete the lateral flexion action. The bushing 15 serves as a buffer and fitment element. The silicone bushing 15 compensates for the assembly error between the slide rail and the slider through its own elastic deformation, reducing mechanical noise during movement. It also isolates the metal parts from direct contact with bone tissue, reducing the risk of foreign body reaction. Figure 5 and Figure 6 As shown.

[0065] In summary, this device achieves a balance between stability and mobility through the coordinated operation of its components. The graded stiffness adjustment preserves more than 80% of the natural movement trajectory within the physiological range of motion of the cervical spine, while mechanically limiting dangerous movements, thus resolving the contradiction between the "rigidity" of traditional fusion surgery and the "instability" of simple non-fusion devices. It exhibits good motion coordination and low damage, with a multi-dimensional motion coupling structure that accurately simulates the natural movement of the cervical spine. The shape memory alloy wire 21 and the buffer pad reduce motion energy loss, and the corrugated endplate 2 reduces stress concentration at the bone interface. Combined with biocompatible materials, it significantly reduces the risk of adjacent segment degeneration and foreign body reaction.

[0066] Example 2

[0067] The difference from the above embodiments is that the stress buffer assembly includes several energy absorption cavities 7 opened in the basic bearing layer. The energy absorption cavities 7 are distributed in a ring shape. Each energy absorption cavity 7 has an opening 9 facing the elastic hinge. The interior of each energy absorption cavity 7 is filled with a porous polyurethane material 8 with a porosity of 80%.

[0068] The stress buffer assembly also includes several buffer wing pieces 4. The buffer wing pieces 4 are all fixedly connected to the side wall of the end plate 2 by flexible hinges. The flexible hinges are made of titanium alloy. The end of the buffer wing piece 4 is provided with a pad, which is bonded to the adjacent vertebra. After the pad is bonded to the adjacent vertebra, the pretension is 10-15N.

[0069] The specific implementation process is as follows: When the cervical spine performs daily activities or is subjected to external impact, the energy absorption cavity 7 of the stress buffer component works in conjunction with the buffer wing 4. The energy absorption cavity 7, which is distributed in a ring shape within the basic bearing layer, can accurately receive the energy transmitted by the elastic hinge during movement through the opening 9 facing the elastic hinge. When the cervical spine is subjected to a sudden external force, such as a rapid head-down or head-turning motion, the impact force generated by the elastic hinge is transmitted to the energy absorption cavity 7 through the opening 9. The porous polyurethane material 8, which has a porosity of 80%, filling the cavity will rapidly undergo compression deformation, converting the kinetic energy generated by the external force into the elastic potential energy of the material, thereby absorbing a large amount of impact energy, effectively reducing the instantaneous load on the core structure, and avoiding damage to the device or excessive compression of the vertebral body due to excessive force. Figure 2 and Figure 5 As shown.

[0070] The buffer wing 4 is hinged to the sidewall of the endplate 2 via a flexible hinge made of titanium alloy. Its end pad is bonded to the adjacent vertebral body. The pretension after connection is maintained at 10-15N. This pretension ensures the stability of the connection between the buffer wing 4 and the adjacent vertebral body without restricting normal physiological movement of the cervical spine. During normal cervical spine movements, with the slight deformation of the basic load-bearing layer, the buffer wing 4 undergoes adaptive bending deformation through the flexible hinge. This deformation transfers part of the load borne by the core structure to the adjacent vertebral body, achieving load diversion. In this way, the stress burden on the stabilizing components and endplate 2 is reduced, stress concentration areas are dispersed, and the stress peak of the adjacent vertebral endplate is significantly reduced, minimizing the risk of osteolysis and adjacent segment degeneration during long-term use.

[0071] The combination of energy absorption cavity 7 and buffer wing 4 forms a multi-layered stress buffering mechanism. Energy absorption cavity 7 mainly deals with the instantaneous energy brought by sudden impact, while buffer wing 4 focuses on continuously diverting the load generated by normal motion. The two work together to greatly improve the overall stress buffering performance of the device and ensure the long-term stability and safety of the cervical spine.

[0072] The specific experimental procedure is as follows: I. Experimental Objectives

[0073] Verification of device performance: dynamic stability (graded stiffness adjustment and rigid limit function); motion fidelity (accuracy of six-degree-of-freedom motion trajectory); stress optimization effect (energy absorption and load diversion capability).

[0074] II. Experimental Grouping

[0075] Experimental group: cervical spine motion segments (C1-C2) implanted with this device; Control group: healthy cervical spine specimens (without any device implanted); Comparative experimental group: implanted with a traditional non-fusion device, with a sample size n of 8 for both groups.

[0076] III. Experimental Procedure

[0077] 1. Dynamic stability test

[0078] (1) Fix the specimen in a biomechanical testing machine and preload it axially with 50N to simulate the weight of the head.

[0079] (2) Flexion / extension / rotation direction loading: increase from 0° to 40° (flexion) or 50° (rotation) at a rate of 2° / s.

[0080] (3) Record the load-displacement curves and stiffness changes at 5° intervals within the range of 0-40°.

[0081] (4) Over-limit test: When the bending angle is >30° and the rotation is >45°, check the locking triggering status of the convex tooth 16-locking groove 10.

[0082] 2. Motion fidelity test

[0083] (1) Affix reflective markers to the end plate 2 and connecting rod 23, with a sampling frequency of 100Hz.

[0084] (2) Simulate cervical spine physiological movements: flexion and extension (0-25°), lateral flexion (0-15°), rotation (0-40°).

[0085] (3) Record the deviation of the motion trajectory between the experimental group and the control group (angle error Δα, displacement error Δd).

[0086] 3. Stress distribution test

[0087] (1) Apply pressure-sensitive pads (pressure range 0.5-10MPa) to the adjacent vertebral endplate (C3 superior endplate 2).

[0088] (2) Apply vertical impact load: 200J energy (simulating fall impact).

[0089] (3) Record the peak stress and distribution area of ​​the final plate 2 of the experimental group / control device group.

[0090] (4) Finite element simulation: Analyze the load transfer path of buffer wing 4 (the force ratio of adjacent pedicles).

[0091] 4. Fatigue durability test

[0092] (1) Simulate a 10-year usage cycle: perform 5 million flexion and extension movements (0-25°) at a frequency of 2Hz.

[0093] (2) Every 500,000 tests: ① Lock pull-out force 6 ② Spring hinge plastic deformation 17 ③ Slide rail wear.

[0094] IV. Experimental Results

[0095] As shown in the table below:

[0096] Table 1. Graded Stiffness Characteristics Data (Buckling-Extension Direction)

[0097]

[0098]

[0099] Table 2. Comparison of motion errors in six degrees of freedom

[0100]

[0101] Table 3. Stress distribution test results

[0102]

[0103] Table 4. Changes in Key Indicators of Fatigue Testing

[0104]

[0105] V. Experimental Conclusions

[0106] The graded stiffness mechanism is effective: it provides near-natural flexible support (stiffness 10 GPa) from 0-25°, linearly increases stiffness to 25 GPa from 25-30°, and triggers rigid locking (to prevent spinal cord injury) at >30°. In contrast, the device lacks transitional stiffness adjustment, resulting in a high risk of excessive movement.

[0107] The six-degree-of-freedom motion error (Δα≤0.47°, Δd≤0.31mm) is significantly better than that of the traditional device (p<0.01), and the average pressure of the endplate is 1.85MPa < the bone resorption threshold (3MPa). The shape memory alloy wire phase change activation mechanism ensures motion coordination.

[0108] The dual-path buffer design reduces the peak stress near the end plate by 37.9% (up to 1.85 MPa), and the load split ratio of 18.7% is close to the theoretical value. Porous polyurethane (80% porosity) achieves efficient energy absorption (10.75 J / mm).

[0109] The structure remained intact after 5 million fatigue tests, and the latch pull-out force (487N) was still higher than the safety threshold (450N). The amount of wear did not affect the movement function.

[0110] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0111] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A non-fusion fixation device for the cervical spine, comprising endplates (2) symmetrically arranged vertically, characterized in that: A stabilizing component is fixedly connected between the end plates (2), a free-moving platform is fixedly connected to the top of the stabilizing component, and a stress buffer component is fixedly connected to the outer periphery of the stabilizing component; The stabilizing component is used to achieve dynamic stability control of the cervical spine segments through graded stiffness adjustment. It provides flexible support within the physiological range of motion, achieves linear stiffness increase in the transitional range of motion, and triggers rigid restraint in the state of excessive activity to prevent spinal cord nerve injury. The free motion platform is used to simulate the natural movement trajectory of the cervical spine and achieve multi-dimensional motion coupling. It coordinates the three-dimensional rotation of flexion, extension, rotation, and lateral flexion, as well as the three-dimensional translation of forward, backward, left, right, and up and down movements, to ensure motion coordination and reduce energy loss and bone interface damage during movement. Stress buffer components are used to absorb impact energy and divert loads to reduce the risk of degeneration in adjacent segments. They absorb the energy generated by sudden external forces through compressive deformation and transfer loads to adjacent vertebrae through the bending deformation of auxiliary support structures, thereby reducing the stress on the core structure, dispersing stress concentration, and reducing the stress peak of adjacent vertebral endplates.

2. The non-fusion fixation device for the cervical spine according to claim 1, characterized in that: The stabilizing component includes a base bearing layer, which is a mesh support (3). The bottom wall of the mesh support (3) is fixedly connected with barbed buckles (6). The lower end plate (2) has an annular groove (5). The buckles (6) are all fixedly connected to the annular groove (5). The top outer wall of the mesh support (3) has a movable annular groove (13). The movable annular groove (13) is movably connected to the upper end plate (2).

3. The non-fusion fixation device for the cervical spine according to claim 2, characterized in that: The stabilizing component also includes several axially vertically distributed spring hinges (17). The top wall of the lower end plate (2) is fixedly connected to the bottom end of the spring hinges (17). The top of the spring hinges (17) is ball-jointed with the bottom wall of the free motion platform. The spring hinges (17) are all made of Ni-Ti alloy. The elastic modulus of the spring hinges (17) is 10 GPa when the cervical spine flexion and extension movement is 0-25°. When the movement is 25-30°, the number of turns decreases and the stiffness increases linearly to 25 GPa.

4. The non-fusion fixation device for the cervical spine according to claim 3, characterized in that: The stabilizing component also includes at least two sets of circumferentially arranged protruding teeth (16) and locking grooves (10). The protruding teeth (16) are all fixedly connected to the bottom wall of the free movement platform, and the locking grooves (10) are all opened on the inner side wall of the foundation bearing layer. When the cervical spine flexion and extension movement is >30° or the rotation movement is >45°, the protruding teeth (16) are completely inserted into the locking grooves (10) to achieve rigid limiting.

5. The non-fusion fixation device for the cervical spine according to claim 1, characterized in that: The free motion platform includes a base (11), the bottom wall of the base (11) is ball-jointed with a spring hinge (17), the top wall of the base (11) is fixedly connected with a bushing (15), the bushing (15) is made of silicone material, the top wall of the bushing (15) is fixedly connected with a horizontal slide rail (18) and a vertical slide rail (20) that are perpendicular to each other, a horizontal slider (19) and a vertical slider are symmetrically slidably fitted on the horizontal slide rail (18) and the vertical slide rail (20), a buffer pad is fixedly connected to the sliding axis side wall of the horizontal slider (19) and the vertical slider, a wire groove (24) is opened on both sides of the horizontal slide rail (18) and the vertical slide rail (20), a memory alloy wire (21) is fixedly connected to both sides of the horizontal slider (19) and the vertical slider, the other end of the memory alloy wire (21) passes through the corresponding wire groove (24) and is fixedly connected to the bushing (15), the memory alloy wire (21) is preset to a phase change temperature of 37°C.

6. The non-fusion fixation device for the cervical spine according to claim 5, characterized in that: The free motion platform also includes a joint ball joint (14), which contacts the bottom wall of the upper endplate (2). The bottom wall of the joint ball joint (14) is hinged with three connecting rods (23) that are inclined at an angle of 30° to the axial direction, and the angle between the connecting rods (23) is 120°. The bottom ends of two connecting rods (23) corresponding to the transverse slide rail (18) are respectively hinged to the transverse slider (19) through a fish-eye bearing. The other connecting rod (23) corresponds to the longitudinal slide rail (20). A connecting shaft (22) is fixedly connected between the longitudinal sliders. The connecting rod (23) corresponding to the longitudinal slide rail (20) is hinged to the connecting shaft (22) through a fish-eye bearing.

7. The non-fusion fixation device for the cervical spine according to claim 1, characterized in that: The stress buffer assembly includes several energy absorption cavities (7) in the foundation bearing layer. The energy absorption cavities (7) are distributed in a ring shape. Each energy absorption cavity (7) has an opening (9) facing the spring hinge (17). The interior of each energy absorption cavity (7) is filled with a porous polyurethane material (8) with a porosity of 80%.

8. The non-fusion fixation device for the cervical spine according to claim 7, characterized in that: The stress buffer assembly also includes several buffer wing pieces (4). The buffer wing pieces (4) are all fixedly connected to the side wall of the end plate (2) by flexible hinges. The flexible hinges are made of titanium alloy. The end of the buffer wing piece (4) is provided with a pad. The pad is bonded to the adjacent vertebra. After the pad is bonded to the adjacent vertebra, the pretension is 10-15N.

9. The non-fusion fixation device for the cervical spine according to claim 1, characterized in that: Several locking screws (1) are distributed circumferentially along the edge of the end plate (2).

10. The non-fusion fixation device for the cervical spine according to claim 1, characterized in that: The endplate (2) and the cervical vertebrae are both provided with a wavy concave-convex layer, which is complementary to the anatomical shape of the cervical vertebral endplate.

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