Unilateral and bilateral lumbar spine shock absorbing facet joint prosthesis

Abstract

The application provides a unilateral or bilateral lumbar spine shock-absorbing zygapophyseal prosthesis, which comprises one or a pair of prosthesis devices arranged in the same structure and opposite directions, and the prosthesis device comprises an upper fixing component, a lower fixing component, a ball-and-socket joint device and a shock-absorbing device; wherein the upper fixing component is fixed to the oblique upper side of the ball-and-socket joint device, the bottom of the ball-and-socket joint device is connected to the shock-absorbing device, and the lower fixing component is fixed to one side of the shock-absorbing device. The application can selectively fix the prosthesis device on one side or two sides according to the actual situation of the patient. In summary, the application has small volume, low destructiveness, high flexibility and shock-absorbing property due to the ball-and-socket joint device and the shock-absorbing device, and the integrated structure simplifies the operation steps in the operation, and only needs to be fixed by screws, so that the operation is good.

Description

Technical Field

[0001] This invention belongs to the field of orthopedic spinal surgery implant technology, specifically relating to a unilateral or bilateral lumbar spine shock-absorbing facet joint prosthesis. Background Technology

[0002] The intervertebral discs and paired facet joints in a single segment of the spine are often collectively referred to as the three-joint complex. As true synovial joints, such as... Figure 1 As shown, each facet joint consists of the superior articular process of the lower vertebral body facing posterolaterally, the inferior articular process of the upper vertebral body facing anteromedially, and the joint capsule. The shape and orientation of these facet joints determine their primary function: to prevent excessive spinal movement, while simultaneously transmitting and bearing some stress. The facet joints of the lumbar spine tend to be oriented in the sagittal plane, which restricts axial rotation of the spine but reduces the restriction on shear stress. It is this unique orientation that allows the lumbar spine to perform a relatively large range of flexion and extension. During lumbar flexion, the superior vertebral body of two adjacent vertebrae slides horizontally forward relative to the inferior vertebral body in cross-section, while simultaneously rotating forward along the transverse axis.

[0003] Currently, lumbar facet joint disorders account for 15% of chronic low back pain, drawing significant attention from clinicians. Lumbar facet joint pain often has an insidious onset, and in addition to its own degeneration, instability, misalignment, and anatomical abnormalities, it is often accompanied by pre-existing lumbar spondylolisthesis and intervertebral disc degeneration. In particular, severe intervertebral disc degeneration can cause long-term biomechanical abnormalities, leading to compensatory degeneration of the posterior facet joints and resulting in pain. Therefore, in lumbar disc replacement or laminectomy, research has begun to explore facet joint replacement and reconstruction to maintain posterior stability of the affected segment and preserve normal function. However, current facet joint prostheses still have some design flaws, including: 1. Large size: They require the removal of not only the facet joints on both sides of the affected segment, but also the spinous process and surrounding ligaments of the corresponding segment to provide implantation space, resulting in significant damage; 2. Complexity of use: The design has many components, requiring multiple screw tightening and assembly during surgery, making operation inconvenient; 3. Poor mobility: The overall design uses metal and other materials for connection and fixation, focusing on stabilizing the posterior lumbar spine structure, but the range of motion is not sufficient to meet natural conditions, resulting in limited movement; 4. Limited function: The prosthesis structure and function are relatively simple, failing to restore the three-joint complex, and cannot restrict excessive movement or help distribute stress. Summary of the Invention

[0004] In view of the problems existing in the prior art, the purpose of the present invention is to provide a unilateral or bilateral lumbar spine shock-absorbing facet joint prosthesis.

[0005] To achieve the above objectives, the present invention employs the following technical solution:

[0006] A unilateral or bilateral lumbar spine shock-absorbing facet joint prosthesis, comprising one or a pair of prosthesis devices arranged in the same structure and opposite directions, the prosthesis device comprising an upper fixing component, a lower fixing component, a ball-and-socket joint device and a shock-absorbing device; wherein the upper fixing component is fixed to the upper and oblique side of the ball-and-socket joint device, the bottom of the ball-and-socket joint device is connected to the shock-absorbing device, and the lower fixing component is fixed to one side of the shock-absorbing device.

[0007] Further, when the prosthesis device comprises a pair of prosthesis devices, the pair of prosthesis devices are fixedly connected by a detachable connecting rod.

[0008] Further, the upper fixing component comprises an upper mounting hole and a matching screw, and the inner wall of the upper mounting hole is provided with a thread.

[0009] Further, the lower fixing component comprises an L-shaped fixing plate, one side of the L-shaped fixing plate is provided with a lower mounting hole, the inner wall of the lower mounting hole is provided with a thread, and the other side is fixedly connected to the shock-absorbing device.

[0010] Further, the ball-and-socket joint device comprises a connecting arm extending obliquely downward from the upper mounting hole of the upper fixing component, a joint ball at the end of the connecting arm, and a joint socket matched with the joint ball, and the joint socket covers at least half of the joint ball.

[0011] Further, the joint socket is provided with an oval opening, the connecting arm enters the joint socket through the oval opening, the long axis of the oval opening is parallel to the sagittal diameter at an angle of 5° to 15°, and the short axis is parallel to the coronal diameter at an angle equal to that between the long axis and the sagittal diameter.

[0012] Further, the shock-absorbing device comprises a housing and a top rod penetrating into the inside of the housing, and the inside of the housing is hollow; the upper end of the top rod is fixed to the bottom of the ball-and-socket joint device, so as to connect the shock-absorbing device and the ball-and-socket joint device into one body.

[0013] A first cavity is arranged between the inner wall and the outer wall of the housing, a piston and a fixed plug are arranged in the housing from top to bottom, the piston is fixedly connected to the lower end of the top rod and can move up and down in the housing, the fixed plug is fixed to the bottom of the inner wall of the housing and has a spacing from the bottom surface of the outer wall of the housing, the upper side of the piston and the space between the piston and the fixed plug form a second cavity and a third cavity respectively; the piston and the fixed plug are connected by a spring; the inside of the housing is filled with a liquid, and the volume of the liquid can at least fill the second and third cavities and at the same time not exceed the total volume of the three cavities.

[0014] A pair of one-way valves in opposite directions are arranged on the piston and the fixed plug, and the liquid flows between the first cavity, the second cavity and the third cavity under the action of pressure through the one-way valves arranged on the piston and the fixed plug.

[0015] Furthermore, the one-way valves on the piston and the fixed plug are positioned in the same direction and correspond to each other.

[0016] Furthermore, the liquid surface is horizontal with the piston when no force is applied.

[0017] Furthermore, the liquid is an oily liquid or other liquid with high viscosity.

[0018] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0019] (1) Small size and minimal damage: Using this prosthesis, only the facet joints and part of the lamina structure on one or both sides of the diseased segment need to be removed, without damaging the spinous process and related ligaments and other anatomical tissues; at the same time, it can be selectively applied on one or both sides according to the patient's actual situation. Both methods preserve the natural structure as much as possible and reduce unnecessary damage.

[0020] (2) Simple to use and easy to operate: The integrated structural design simplifies the operation steps during the operation, requiring only screws for fixation at the top and bottom; the rotatable ball-and-socket joint design provides a certain degree of flexibility in the length of the prosthesis, making it suitable for different individual sizes, and the implantation position is relatively flexible, with strong operability during the operation.

[0021] (3) Multi-axis mobility and good flexibility: The design of the ball-and-socket joint component in the prosthesis ensures a wide range of motion, allowing for full freedom of movement of the lumbar spine, such as flexion, extension, lateral bending, and torsion, through rotation; but at the same time, the design of the size of the joint socket opening can limit the range of motion of each axis as needed, preventing excessive spinal movement.

[0022] (4) Shock-absorbing design and functional enhancement: In addition to the basic structural reconstruction of the facet joints, the prosthesis also incorporates a shock-absorbing structure to help the intervertebral disc bear more load and disperse stress in order to prevent the intervertebral disc from degenerating. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the facet joints of the lumbar vertebrae.

[0024] Figure 2 This is a top view of the facet joints of the lumbar vertebrae.

[0025] Figure 3 This is a schematic diagram of the structure of the prosthesis of the present invention. The structure is for the left side of the lumbar spine, and the structure for the right side of the lumbar spine is the same and mirror-symmetrical.

[0026] Figure 4 This is a structural diagram of the ball-and-socket joint component of the prosthesis. The left side is a top view of the elliptical opening on the ball-and-socket joint component.

[0027] Figure 5 This is a schematic diagram of the one-way valve of the shock absorption device for the prosthesis.

[0028] Figure 6 This is a schematic diagram of the process of vibration reduction of the prosthesis.

[0029] Figure 7 This is a schematic diagram of the prosthesis of the present invention after implantation in the lumbar spine.

[0030] The present invention will be further explained and described below with reference to the accompanying drawings and specific embodiments. Detailed Implementation

[0031] like Figure 3 As shown, the unilateral or bilateral lumbar vertebral facet joint prosthesis with shock absorption provided by the present invention includes one or a pair of prosthesis devices with mirror-symmetrical structures. The main body is suitable for unilateral or bilateral placement at the superior and inferior facet joints and nearby lamina on the dorsal side of the disease segment. The prosthesis device includes an upper fixation component 1, a lower fixation component 2, a ball-and-socket joint device 3, and a shock-absorbing device 4. The upper fixation component 1 is fixed to the upper oblique position of the ball-and-socket joint device 3, the bottom of the ball-and-socket joint device 3 is connected to the shock-absorbing device 4, and the lower fixation component 2 is fixed to one side of the shock-absorbing device 4.

[0032] In the above technical solution, the upper fixation component 1 and the lower fixation component 2 are used to fix the ball-and-socket joint device 3 and the shock-absorbing device 4 to the vertebral body, respectively, thereby achieving fixation of the upper and lower parts of the prosthesis on the vertebral body. The ball-and-socket joint device 3 is rotatable, which to a certain extent realizes the variation of the prosthesis height of the present invention, making it suitable for different individual sizes. At the same time, the ball-and-socket joint device 3 ensures a wide range of motion of the prosthesis, and through rotation, it can effectively meet all degrees of freedom of movement of the lumbar spine, such as flexion, extension, lateral bending, and torsion. The shock-absorbing device 4 is used to help the intervertebral disc bear more load and disperse stress to avoid the intervertebral disc degeneration. At the same time, the prosthesis device can be selectively fixed unilaterally or bilaterally according to the actual situation of the patient. In summary, this solution has a small size, which makes it less destructive, while having good flexibility and good vibration damping; the integrated structure simplifies the operation steps during operation, requiring only upper and lower fixation with screws, making it easy to operate.

[0033] Preferably, when a double-sided fixation prosthesis device is required, the two prosthesis devices are connected and fixed at a relative distance by a detachable connecting rod, making the overall structure more stable.

[0034] Preferably, the upper fixation component 1 includes an upper mounting hole 1-1 and a matching screw 1-2. The inner wall of the upper mounting hole 1-1 is threaded (to increase the fixation between the screw and the prosthesis and prevent loosening). The screw 1-2 is used to be screwed into the pedicle through this hole to fix the upper fixation component 1 to the vertebral body. The lower fixation component 2 includes an L-shaped fixation plate 2-1. One side of the L-shaped fixation plate 2-1 is provided with a lower mounting hole 2-2, and its inner wall is threaded so that the matching screw 1-2 can be screwed in to complete the fixation of the lower fixation component 2 on the vertebral body. The other side is fixed to the shock absorption device 4 as a whole (preferably welded).

[0035] like Figure 4 As shown, the ball-and-socket joint device 3 includes a connecting arm 3-1 extending obliquely downward and backward from the upper mounting hole 1-1 of the upper fixing component 1, a ball 3-2 at the end of the connecting arm 3-1, and a matching socket 3-3. Specifically, the socket 3-3 covers the ball 3-2 at least more than half of its surface to prevent the ball 3-2 from dislodging.

[0036] Preferably, considering that the facet joints need to prevent excessive movement of the lumbar spine (normal range of motion of a single lumbar spine segment: flexion and extension 12-20 degrees, rotation 2-3 degrees, lateral bending 3-11 degrees), the opening of the glenoid fossa 3-3 should not be too large. Only an elliptical opening is left on the spherical surface of the upper outer quadrant. The connecting arm 3-1 enters the glenoid fossa 3-3 through this elliptical opening, and the angle between the major axis of the ellipse and the sagittal diameter is 5° to 15° to ensure a large range of flexion and extension movements. The angle between the minor axis of the ellipse and the coronal diameter is equal to the angle between the major axis and the sagittal diameter to limit relatively small lateral bending movements.

[0037] The shock-absorbing device 4 includes a housing 4-1 and a push rod 4-2 whose lower end extends into the housing 4-1. Specifically, the housing 4-1 is hollow inside to store liquid. The upper end of the push rod 4-2 is welded and fixed to the bottom of the ball-and-socket joint device 3, thereby connecting the shock-absorbing device 4 and the ball-and-socket device 3 into one unit. When the lumbar spine moves, compressive or tensile stress can be transmitted downward through the ball-and-socket device 3 via the push rod 4-2. Preferably, a through hole is opened on the upper surface of the housing 4-1, and the lower end of the push rod 4-2 extends into the housing 4-1 through the through hole. A sealing ring is provided in the through hole. The sealing ring between the push rod 4-2 and the hole ensures that the liquid inside the housing 4-1 does not leak out.

[0038] Specifically, a first cavity is provided between the inner and outer walls of the housing 4-1. A piston 4-3 and a fixed plug 4-5 are arranged from top to bottom inside the housing 4-1. The piston 4-3 is fixedly connected to the lower end of the push rod 4-2 and can move up and down inside the housing 4-1 with the push rod 4-2. The fixed plug 4-5 is fixed to the bottom of the inner wall of the housing 4-1 and has a gap between it and the bottom surface of the outer wall of the housing 4-1 (the gap length is at least sufficient for the movement of the one-way valve). A second cavity and a third cavity are formed above the piston 4-3 and between the piston 4-3 and the fixed plug 4-5, respectively. The piston 4-3 and the fixed plug 4-5 are connected by a spring 4-4. The housing 4-1 is filled with liquid 4-7, the liquid volume of which is sufficient to fill at least the second and third cavities to maximize shock absorption while avoiding excessive vibration. The total capacity of the three cavities should exceed the limit, and the liquid level should ideally be at the level of piston 4-3 under no-force conditions. Oily liquids are preferred due to their good resistance and energy absorption properties, which can provide shock absorption. Other liquids with high viscosity can also be used; water, due to its low viscosity, is not recommended. A pair of one-way valves 4-6 in opposite directions are provided on both piston 4-3 and fixed plug 4-5 (for better compression and shock absorption, it is preferable that the one-way valves on the piston and fixed plug are positioned in the same direction). The one-way valves 4-6 connect the first, second, and third cavities of the housing 4-1. Under pressure, the oil flows between the first, second, and third cavities through the one-way valves 4-6 on piston 4-3 and fixed plug 4-5.

[0039] Under the structural design of the aforementioned shock-absorbing device 4, when the lumbar spine moves, the push rod 4-2 drives the piston 4-3 to move up and down inside the housing 4-1, while the fixed plug 4-5 located at the bottom of the housing 4-1 is fixed to the housing 4-1. When no external force is applied, the spring 4-4 ​​between the piston 4-3 and the fixed plug 4-5 is in a certain degree of compression (but not fully compressed, still having room for compression when subjected to force). It supports the piston 4-3 through its upward elastic force, maintaining the shock-absorbing device 4 at a certain height, thus ensuring its functional state.

[0040] Specifically, such as Figure 5 As shown, the one-way valve 4-6 only allows liquid to flow in one direction. When the piston 4-3 is pressed down by the push rod 4-2, the pressure of the oil 4-7 in the lower part of the piston 4-3 is upward, causing the one-way valve 4-6 on the right side of the piston 4-3 to be pushed up. This allows the oil 4-7 in the third cavity to flow through the gap into the second cavity in the upper part of the piston 4-3, while the one-way valve on the left side is closed, and no liquid flows through. When the piston 4-3 is pulled up, the situation is exactly the opposite. The same applies to the one-way valve 4-6 on the fixed piston 4-5. The oil flows between the third cavity and the first cavity, following the piston's movement. The distribution of oil in the three cavities increases and decreases, forming a complementary relationship.

[0041] Therefore, the complete damping process of the above-mentioned damping device 4 is as follows: Figure 6As shown, when the prosthesis of this invention is subjected to stress, the push rod 4-2 pushes the piston 4-3 downward to compress the spring 4-4. At the same time, the one-way valve on the right side of the piston 4-3 and the one-way valve on the left side of the fixed plug 4-5 open, and the oil 4-7 inside the third cavity begins to flow into the second cavity and the first cavity above the piston 4-3, completing the shock-absorbing compression. When the stress dissipates, the compressed spring 4-4 ​​pushes the piston 4-3 upward through its own elasticity, and the oil 4-7 flows back from the second cavity to the third cavity, and part of it flows back to the first cavity. The shock-absorbing device 4 returns to its original height, thus completing one stress movement.

[0042] Preferably, all components of the prosthesis of the present invention are made of high-strength medical-grade metal materials (including but not limited to: medical stainless steel, titanium and its alloys, cobalt-based alloys). The screws 1-2 used in the upper fixation component 1 and the lower fixation component 2 are spinal fixation screws (including but not limited to: ordinary screws, cortical bone screws, universal screws). In summary, the present invention uses a combination of hydraulic damping and spring damping, rather than relying solely on spring damping. The main reason is that after the spring is removed from its compressive force, it will repeatedly bounce up and down, generating damped vibrations, which are detrimental to structural stability. Hydraulic fluid has strong energy absorption and damping properties, which can avoid excessive damped vibrations and control the damping device to achieve fast compression and slow rebound, resulting in a more ideal effect.

[0043] Specifically, the usage process of the unilateral and bilateral lumbar spine shock-absorbing facet joint prostheses of the present invention is as follows:

[0044] Step 1: Expose the posterior anatomical structures of the lumbar spine during surgery, and remove the inferior articular process of the superior vertebra and the superior articular process of the inferior vertebra of the affected segment. Place the prosthesis of this invention on a trial basis. To accommodate the size of the prosthesis, if necessary, part of the lamina may be removed to expand the posterior space, and the cut surface may be trimmed to allow the L-shaped plate to fit snugly for more stable fixation. Then, prepare 1-2 screws for fixation.

[0045] Step 2: Screws 1-2 are screwed into the vertebral body through the lower mounting hole 2-2 and the pedicle, thereby fixing the shock absorption device 4 to the lower vertebral body. Figure 7As shown. The ideal entry point is similar to the various sites used in conventional pedicle screw fixation, with the preferred entry point recommended by the "AO" method being the intersection of the tangent to the outer edge of the superior articular process and the midline of the transverse process. This point is located at the angle between the base of the transverse process and the superior articular process. The implantation angle is perpendicular to the posterior edge of the vertebral body and tilted inward at a certain angle (this angle is the same as the angle between the major axis of the elliptical opening and the sagittal diameter, ranging from 5° to 15°). The screw depth should be at least 50% but not more than 80% of the anteroposterior diameter of the vertebral body; thicker and longer screws are preferred for safety. The screw head should be close to the bone surface. If necessary, a small amount of transverse process bone should be removed to make the screw head as anterior as possible, shortening the distance from the lumbar spine motion axis and positioning it lateral to the articular process. Then, screws 1-2 are installed in the upper mounting hole 1-1 according to the same requirements to fix the ball-and-socket joint device 3 to the vertebral body.

Claims

1. A unilateral or bilateral lumbar spine shock-absorbing facet joint prosthesis, characterized in that, The device includes one or a pair of mirror-symmetrical prosthetic devices, the prosthetic device including an upper fixation component (1), a lower fixation component (2), a ball-and-socket joint device (3) and a shock-absorbing device (4); wherein the upper fixation component (1) is fixed to the upper side of the ball-and-socket joint device (3), the bottom of the ball-and-socket joint device (3) is connected to the shock-absorbing device (4), and the lower fixation component (2) is fixed to one side of the shock-absorbing device (4); The ball-and-socket joint device (3) includes a connecting arm (3-1) extending obliquely downward from the upper mounting hole (1-1) of the upper fixing component (1), a ball (3-2) at the end of the connecting arm (3-1), and a matching socket (3-3), wherein the socket (3-3) covers the ball (3-2) for at least more than half of the spherical surface. The articular fossa (3-3) has an elliptical opening, through which the connecting arm (3-1) enters the articular fossa (3-3). The angle between the major axis of the ellipse and the sagittal diameter is 5° to 15°, and the angle between the minor axis and the coronal diameter is equal to the angle between the major axis and the sagittal diameter. The shock-absorbing device (4) includes a housing (4-1) and a top rod (4-2) with its lower end inserted into the housing (4-1). The housing (4-1) is hollow inside. The upper end of the top rod (4-2) is fixed to the bottom of the ball joint device (3), thereby connecting the shock-absorbing device (4) and the ball joint device (3) into one unit. A first cavity is provided between the inner and outer walls of the housing (4-1). A piston (4-3) and a fixed plug (4-5) are arranged from top to bottom inside the housing (4-1). The piston (4-3) is fixedly connected to the lower end of the push rod (4-2) and can move up and down inside the housing (4-1) with the push rod (4-2). The fixed plug (4-5) is fixed to the bottom of the inner wall of the housing (4-1) and has a gap with the bottom surface of the outer wall of the housing (4-1). A second cavity and a third cavity are formed above the piston (4-3) and between the piston (4-3) and the fixed plug (4-5), respectively. The piston (4-3) and the fixed plug (4-5) are connected by a spring (4-4). The housing (4-1) is filled with liquid (4-7), and the volume of the liquid is at least enough to fill the second and third cavities, but does not exceed the total capacity of the three cavities. A pair of one-way valves (4-6) with opposite directions are provided on both the piston (4-3) and the fixed piston (4-5). Under pressure, the oil flows between the first cavity, the second cavity and the third cavity through the one-way valves (4-6) provided on the piston (4-3) and the fixed piston (4-5).

2. The unilateral or bilateral lumbar spine shock-absorbing facet joint prosthesis as described in claim 1, characterized in that, When a pair of the prosthetic devices is included, the pair of prosthetic devices are fixedly connected by a detachable connecting rod.

3. The unilateral or bilateral lumbar spine shock-absorbing facet joint prosthesis as described in claim 1, characterized in that, The upper fixing component (1) includes an upper mounting hole (1-1) and its matching screw (1-2), and the inner wall of the upper mounting hole (1-1) is provided with threads.

4. The unilateral or bilateral lumbar spine shock-absorbing facet joint prosthesis as described in claim 1, characterized in that, The lower fixing component (2) includes an L-shaped fixing plate (2-1). One side of the L-shaped fixing plate (2-1) is provided with a lower mounting hole (2-2), and its inner wall is provided with threads. The other side is fixed to the shock absorption device (4) as a whole.

5. The unilateral or bilateral lumbar spine shock-absorbing facet joint prosthesis as described in claim 1, characterized in that, The one-way valves on the piston and the fixed piston are positioned in the same direction and correspond to each other.

6. The unilateral or bilateral lumbar spine shock-absorbing facet joint prosthesis as described in claim 1, characterized in that, The liquid level is horizontal with piston (4-3) when there is no force applied.

7. The unilateral or bilateral lumbar spine shock-absorbing facet joint prosthesis as described in claim 1, characterized in that, The liquid used is an oily liquid or other highly viscous liquid.

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