A new type of lumbar facet joint prosthesis

Abstract

The present application belongs to the technical field of spinal surgery implants, and discloses a new lumbar facet joint prosthesis, which comprises a first fixed base and a second fixed base, a central auxiliary support module connecting the first fixed base and the second fixed base, two groups of joint modules, a joint socket and a joint head, the joint head is ellipsoidal, the joint head is arranged in the inner cavity of the joint socket, the joint head and the inner cavity of the joint socket are in clearance fit, a first opening and a second opening are arranged on the joint socket, and the height of the side wall of the joint socket near the central auxiliary support module on one side is higher than that on the opposite side. The two groups of joint modules symmetrically arranged are used for supporting and limiting the two sides of the vertebral body respectively, instead of the arrangement of a single central elastic connecting piece, so that more stable support is provided, and the stability of the prosthesis is improved; through the clearance fit of the ellipsoidal joint head and the joint socket, the two groups of joint modules are dynamically active, the multidimensional movement of the natural facet joint is simulated, and the movement mode of the lumbar vertebrae is more fitted.

Description

Technical Field

[0001] This invention relates to the field of spinal surgical implants, and more particularly to a novel lumbar facet joint prosthesis. Background Technology

[0002] A primary goal of spinal surgery is to decompress nerves, relieving pressure caused by spinal stenosis or herniated discs. After decompression, the bony components of the spinal canal (including the spinous processes, laminae, and facet joints) are removed. These components are crucial for spinal stability; their removal can lead to spinal instability and slippage. Currently, the most common method worldwide to prevent instability and slippage after spinal decompression surgery is rod-and-screw fixation (fusion). While this method achieves stability, it sacrifices the mobility between spinal bones, accelerating degeneration of adjacent spinal segments and potentially triggering further disease; this condition is known as adjacent vertebral dysplasia.

[0003] To mitigate the negative impacts of fusion, various alternatives have been developed internationally, including artificial intervertebral discs, flexible rod-and-screw joints, and traditional facet joint prostheses. However, artificial intervertebral discs, due to their anterior approach and greater surgical complexity, cannot achieve posterior decompression, thus limiting their surgical indications. Flexible rod-and-screw joints do not conform to the biomechanics of spinal movement and cannot prevent degeneration of adjacent segments. Traditional facet joint prostheses, such as the TOPS prosthesis currently used internationally, while retaining some mobility, rely on a central elastic connector to link bilateral pedicle screws for elastic support, failing to achieve complete reconstruction of both facet joints. This results in uneven mechanical transmission, leading to insufficient spinal stability and coordination. Therefore, there is an urgent need for a bilaterally symmetrical lumbar facet joint replacement prosthesis that biomechanically conforms to the natural state of the human body to meet these requirements. Summary of the Invention

[0004] The present invention aims to provide a novel lumbar facet joint prosthesis to solve the biomechanical problems of existing prostheses being unable to perform bilateral symmetrical reconstruction and not conforming well to lumbar spine movement.

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

[0006] A novel lumbar facet joint prosthesis includes:

[0007] The first fixation base and the second fixation base are used to fix and connect with the upper and lower vertebral bodies of the surgical segment, respectively.

[0008] The central auxiliary support module connects the first fixed base and the second fixed base to provide auxiliary support;

[0009] Two sets of joint modules are symmetrically arranged between the first fixed base and the second fixed base. Each set of joint modules includes a joint socket and a joint head. The joint head is ellipsoidal and is connected to the first fixed base through a first connecting post. The joint head is located in the inner cavity of the joint socket, which is an ellipsoidal cavity that matches the joint head. The joint head and the inner cavity of the joint socket are in clearance fit. The joint socket is connected to the second fixed base through a second connecting post. The joint socket is provided with a first opening and a second opening. The first opening is used to allow one end of the joint head to slide out of the joint socket. The side wall of the joint socket near the central auxiliary support module is higher than the opposite side, so that the second opening is inclined at the top of the joint socket.

[0010] Furthermore, the central auxiliary support module includes a protrusion disposed at the center of the first fixed base and a recessed block adapted to the protrusion, the recessed block being disposed on the base, and the base being disposed on the second fixed base.

[0011] Furthermore, a pad is provided between the recess and the base. The pad has a preset thickness. The top and bottom surfaces of the pad are provided with locking strips, which are respectively locked in the locking grooves on the recess and the base. A fixing plate is provided at the end of the locking strip. Two sets of bolts are provided on the fixing plate, and the two sets of bolts are respectively inserted into the recess and the base.

[0012] Furthermore, a polymer material bushing is provided on the top surface of the concave block and the inner cavity of the joint socket.

[0013] Furthermore, a sealing sleeve is provided on the concave block, the sealing sleeve covers the protrusion, a sealing capsule is provided outside the joint socket, and both the joint socket and the joint head are covered inside the sealing capsule. Both the first connecting post and the second connecting post penetrate the sealing capsule.

[0014] Furthermore, the first connecting post is slidably inserted into the first fixed base, and the second connecting post is slidably inserted into the second fixed base. Both the first and second fixed bases are provided with locking seats, and the locking seats are provided with a first set screw, which is used to lock the first connecting post and the second connecting post.

[0015] Furthermore, both the first and second fixing bases are provided with fixing modules. The fixing module includes a fixing block, a universal pedicle screw, and a No. 2 set screw. The fixing block is slidably sleeved on both the first and second fixing bases. The top of the universal pedicle screw passes through one side of the fixing block, and the No. 2 set screw passes through the other side of the fixing block for locking the fixing block.

[0016] The principles and beneficial effects of the technical solution are as follows:

[0017] This invention provides a novel lumbar facet joint prosthesis.

[0018] 1. The first and second fixed bases are connected to the upper and lower vertebral bodies respectively to form a stable base. Two sets of symmetrical joint modules support and connect the two sides, replacing the traditional single central elastic connector. They support and limit the two sides of the vertebral body respectively, providing more stable support and improving the stability of the prosthesis.

[0019] 2. By fitting the ellipsoidal articular head with the glenoid socket, the multi-dimensional movement of the natural facet joint is simulated. During flexion, the articular heads on both sides slide towards the No. 1 opening behind the glenoid socket, and the tip of the ellipsoidal articular head can extend out of the No. 1 opening. During lateral flexion, the articular head on the compressed side moves and rotates towards the higher side wall of the glenoid socket, pressing against the side wall to provide support. Meanwhile, the articular head on the symmetrical other side moves towards the lower side wall of its glenoid socket and is lifted upward, with its top extending out of the No. 2 opening. This achieves compression support on one side and independent movement on the other side, avoiding mutual interference. This allows the joint module to achieve independent support, balancing stability and mobility, and better conforming to the movement pattern of the human lumbar spine.

[0020] 3. Adjust the first connecting post to slide through the first fixed base, and the second connecting post to slide through the second fixed base, and lock them with the first set screw. By adjusting the positions of the first and second connecting posts, the surgeon can precisely adjust the position of the joint module between the upper and lower vertebral bodies according to the patient's specific anatomy, making the prosthesis more adaptable and improving the surgical effect.

[0021] 4. By selecting pads of different thicknesses and adjusting the distance between the first and second bases, it can be adapted to patients with different lumbar intervertebral spaces, restoring intervertebral height and physiological curvature. At the same time, the combination of protrusions and recesses provides auxiliary support and stability. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the present invention;

[0023] Figure 2 This is a schematic diagram of the assembly structure of the present invention;

[0024] Figure 3 for Figure 2 Enlarged view of point A in the middle;

[0025] Figure 4 This is a schematic diagram of the structure of the first fixed base and the second fixed base in this invention;

[0026] Figure 5 This is a schematic diagram of the structure of the articular head and articular fossa in this invention;

[0027] Figure 6 This is a front view of the articular fossa in this invention;

[0028] Figure 7 This is a schematic diagram of the forward bending state structure of the present invention;

[0029] Figure 8 This is a side view of the forward flexion state of the present invention;

[0030] Figure 9 This is a schematic diagram of the lateral bending state structure of the present invention;

[0031] Figure 10 This is a side view of the lateral flexion state of the present invention;

[0032] The corresponding labels in the attached diagram are named as follows: 1. First fixed base; 101. Locking seat; 102. No. 1 set screw; 2. Second fixed base; 201. Base; 202. Slot; 3. Joint module; 301. Joint socket; 3011. No. 1 opening; 3012. No. 2 opening; 302. Joint head; 303. No. 1 connecting post; 304. No. 2 connecting post; 305. Sealing capsule; 4. Central auxiliary support module; 401. Protrusion; 402. Concave block; 403. Pad; 404. Locking strip; 405. Fixing plate; 406. Bolt; 407. Sealing sleeve; 5. Fixing module; 501. Fixing block; 502. Universal pedicle screw; 503. No. 2 set screw. Detailed Implementation

[0033] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments:

[0034] like Figures 1-10 As shown, a novel lumbar facet joint prosthesis includes:

[0035] The first fixation base 1 and the second fixation base 2 are both U-shaped structures made of medical titanium alloy (such as Ti6Al4V). The first fixation base 1 is an upright U-shape, used for fixed connection with the upper vertebral body of the surgical segment, and the second fixation base 2 is an inverted U-shape, used for fixed connection with the lower vertebral body of the surgical segment.

[0036] The central auxiliary support module 4 is located between the two sets of joint modules 3, connecting the first fixed base 1 and the second fixed base 2, and is used to provide auxiliary support;

[0037] Two sets of joint modules 3 are symmetrically arranged between the first fixed base 1 and the second fixed base 2. Each set of joint modules 3 includes a joint socket 301 and a joint head 302. The joint head 302 is ellipsoidal, with its major axis parallel to the sagittal plane and its minor axis parallel to the coronal plane. This ellipsoidal design allows the joint head 302 to have different radii of curvature in the sagittal and coronal planes, thus enabling different degrees of sliding within the joint socket 301. The top of the joint head 302 is integrally formed or threadedly connected to a first connecting post 303. The first connecting post 303 is cylindrical, and the joint head 302 is connected to the first fixed base 1 through the first connecting post 303. The joint head 302 is located in the inner cavity of the joint socket 301, which is an ellipsoidal cavity that matches the joint head 302. Furthermore, the articular head 302 and the inner cavity of the articular socket 301 are fitted with a clearance. The clearance is designed as follows: 0.2-0.6 mm in the anterior-posterior direction (sagittal plane), 0.1-0.2 mm in the lateral direction (coronal plane), and 0.1-0.2 mm in the vertical direction. This allows the articular head 302 to slide a large range in the anterior-posterior direction during flexion, meeting the physiological angle requirements of flexion. However, it can only slide a small range during lateral flexion, meeting the physiological angle requirements of lateral flexion while preventing dislocation. The vertical clearance allows one side to be compressed and the other side to lift and separate during lateral flexion, avoiding interference. The bottom of the articular socket 301 is integrally formed or connected by a threaded second connecting post 304. The second connecting post 304 is cylindrical, and the articular socket 301 is connected to the second fixing base 2 through the second connecting post 304.

[0038] The articular fossa 301 is provided with a first opening 3011 and a second opening 3012. The first opening 3011 is located at the rear of the articular fossa 301 (i.e., the side facing the surgical approach). The inner diameter of the first opening 3011 is less than 2 / 3 of the maximum outer diameter along the long axis of the ellipsoidal articular head 302, allowing one end of the articular head 302 to slide out of the articular fossa 301 a short distance, providing space for flexion movement. The second opening 3012 is located at the top of the articular fossa 301, and is inclined. The second opening 3012 is elliptical and fits the articular head 302. The area of ​​the second opening 3012 is smaller than that of the articular head 301. 2. The maximum cross-sectional area of ​​the horizontal section is used to limit the articular head 302 and prevent it from completely separating from the articular socket 301. The side wall height of the articular socket 301 on the side closer to the central auxiliary support module 4 is higher than that on the opposite side. Specifically: in the left articular module 3, the height of the left wall (away from the midline of the spine) is 4-5 mm, and the height of the right wall (close to the midline of the spine) is 3-3.5 mm; in the right articular module 3, the height of the right wall (away from the midline of the spine) is 4-5 mm, and the height of the left wall (close to the midline of the spine) is 3-3.5 mm; at the same time, the height of the anterior wall (close to the vertebral body) of the articular socket 301 is 4-5 mm.

[0039] In this embodiment, the central auxiliary support module 4 includes a protrusion 401 disposed at the center of the first fixed base 1 and a recess 402 adapted to the protrusion 401. The recess 402 is disposed on the base 201, and the base 201 is disposed on the second fixed base 2. Through the cooperation of the protrusion 401 and the recess 402, auxiliary support is provided for the first fixed base 1 and the second fixed base 2, reducing the impact of running and jumping movements on the joint head 302 and joint socket 301 in the joint module 3 during the patient's daily life, reducing the wear of the prosthesis, and extending its service life.

[0040] In this embodiment, a pad 403 is provided between the recess 402 and the base 201. The pad 403 is made of rigid biocompatible materials such as titanium alloy or PEEK and has a preset thickness (e.g., 1mm, 2mm, 3mm, 5mm, etc.). The top and bottom surfaces of the pad 403 are provided with locking strips 404, which are respectively locked in the locking grooves 202 on the recess 402 and the base 201. The end of the locking strip 404 is provided with a fixing plate 405. The fixing plate 405 is provided with two sets of bolts 406, which are respectively inserted into the recess 402 and the base 201 to lock the relative positions of the recess 402, the pad 403 and the base 201. By selecting a pad 403 of appropriate thickness, the distance between the recess 402 and the base 201 can be adjusted, thereby adjusting the height of the entire central auxiliary support module 4 so that it can adapt to different intervertebral heights and make the prosthesis more adaptable.

[0041] In this embodiment, both the top surface of the concave block 402 and the inner cavity of the joint socket 301 are provided with polymer material bushings. The polymer bushings are made of cross-linked ultra-high molecular weight polyethylene (XPE) in the prior art, which has the characteristics of high strength, stable chemical properties and smooth surface. The inner surface of the polymer material bushing in the inner cavity of the joint socket 301 is precisely processed into an ellipsoidal surface that matches the joint head 302, and the polymer material bushing on the top surface of the concave block 402 is adapted to the top surface of the concave block 402. The polymer material bushings can reduce friction and debris generation and extend the service life of the prosthesis.

[0042] In this embodiment, a sealing sleeve 407 is provided on the concave block 402, which covers the protrusion 401 and forms a seal with it. A sealing capsule 305 is provided outside the joint socket 301, and both the joint socket 301 and the joint head 302 are covered inside the sealing capsule 305. The first connecting post 303 and the second connecting post 304 both penetrate the sealing capsule 305 and are sealed to it. The sealing sleeve 407 and the sealing capsule 305 are both made of medical-grade polycarbonate polyurethane (PCU) to isolate external tissues. At the same time, they can be filled with lubricating fluid to reduce debris generation.

[0043] In this embodiment, a first connecting post 303 is slidably inserted into the first fixed base 1, and a second connecting post 304 is slidably inserted into the second fixed base 2. Both the first fixed base 1 and the second fixed base 2 are provided with locking seats 101, each containing a first set screw 102. The first set screw 102 is used to lock the first connecting post 303 and the second connecting post 304. By adjusting the position of the first connecting post 303 on the first fixed base 1 and the position of the second connecting post 304 on the second fixed base 2, the position of the joint module 3 relative to the first fixed base 1 and the second fixed base 2 can be adjusted. Then, by tightening the first set screw 102, the joint is locked. This allows medical personnel to adjust the prosthesis according to the actual situation, better adapting it to the patient and improving the surgical outcome.

[0044] In this embodiment, both the first fixing base 1 and the second fixing base 2 are provided with fixing modules 5. The fixing module 5 includes a fixing block 501, a universal pedicle screw 502, and a second setter screw 503. The fixing block 501 is slidably sleeved on both the first fixing base 1 and the second fixing base 2. The top of the universal pedicle screw 502 is hemispherical and passes through a socket on one side of the fixing block 501, forming a universal connection. A second setter screw 503 passes through the other side of the fixing block 501 to lock the fixing block 501. 501 is slidably sleeved on the first fixed base 1 or the second fixed base 2, and its position can be adjusted along the length of the base. With the help of the universal pedicle screw 502, it can be fixed more conveniently. After the universal pedicle screw 502 is driven in, the first fixed base 1 and the second fixed base 2 are respectively inserted into the corresponding fixed block 501, and then the No. 2 set screw 503 is tightened to lock the fixed module 5 to the first fixed base 1 and the second fixed base 2, thereby completing the installation of the first fixed base 1 and the second fixed base 2.

[0045] Taking the L4-L5 segment of the lumbar spine as an example, during the insertion of this prosthesis, two universal pedicle screws 502 are inserted into the pedicle of L5. The two ends of the two sets of joint modules 3 are respectively inserted into the first fixation base 1 and the second fixation base 2. Then, the vertical section of the second fixation base 2 is inserted into the fixing block 501 at the top of the universal pedicle screw 502 on L5. Next, two universal pedicle screws 502 are inserted into the pedicle of L4. At this point, the prosthesis is pushed upwards so that the vertical section of the first fixation base 1 is inserted into the fixing block 501 at the top of the universal pedicle screw 502 on L4. After adjusting to the appropriate position, the No. 2 set screws 503 are tightened to fix the first fixation base 1 to the L4 segment. 4. The second fixing base 2 is fixed on L5. Then, adjust the insertion length of the first connecting post 303 and the second connecting post 304 to adjust their position relative to L4 and L5, so that they match the patient's physiological structure. Then tighten each of the first set screws 102. At this time, the concave block 402 is connected to the first fixing base 1 through the sealing sleeve 407, and the protrusion 401 is completely located inside the sealing sleeve 407, with a certain distance between it and the concave block 402. Select a pad 403 of appropriate thickness and install it between the concave block 402 and the base 201 through the clip 404 and the slot 202, so that the concave block 402 and the protrusion 401 are in contact, thus completing the installation of the prosthesis.

[0046] Under lumbar load-bearing conditions, L4 and its ligaments and muscles move the first fixation base 1 downwards, causing the articular head 302 to be located at the bottom of the glenoid cavity 301. This, along with the protrusion 401 and concave block 402, supports the patient's lumbar spine. When the patient flexes forward, L4 and its ligaments and muscles cause the first fixation base 1 to deflect forward, causing the articular head 302 to slide in the glenoid cavity 301 towards the first opening 3011. A portion of the articular head 302 extends beyond the first opening 3011 to accommodate a larger angle of flexion. During extension, the articular head 302 slides in the opposite direction and, after sliding a certain distance, is blocked by the anterior wall of the glenoid cavity 301, restricting extension. The angle is adjusted to avoid excessive extension. During lateral flexion, such as left lateral flexion, L4 and ligaments and muscles cause the first fixed base 1 to shift to the left, causing the left joint head 302 to slide towards the left wall within the left joint socket 301 and rotate at a certain angle. The left joint head 302 is limited by the left wall. At this time, the right joint head 302 moves towards the left wall of the right joint socket 301 and is lifted upward, so that a part of the top of the right joint head 302 extends out of the second opening 3012 at the top of the right joint socket 301. This achieves the effect of one side bearing the weight and the other side being separated and movable, avoiding interference between the two sets of joint modules 3, which would prevent lateral flexion.

[0047] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific technical solutions or characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements 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 novel lumbar facet joint prosthesis, characterized in that, include: The first fixing base (1) and the second fixing base (2) are used to fix and connect with the upper and lower vertebral bodies of the surgical segment, respectively. The central auxiliary support module (4) connects the first fixed base (1) and the second fixed base (2) to provide auxiliary support; Two sets of joint modules (3) are symmetrically arranged between the first fixed base (1) and the second fixed base (2). Each set of joint modules (3) includes a joint socket (301) and a joint head (302). The joint head (302) is ellipsoidal and is connected to the first fixed base (1) through a connecting post (303). The joint head (302) is disposed in the cavity of the joint socket (301). The cavity of the joint socket (301) is an ellipsoidal cavity that matches the joint head (302). The joint head (302) and the joint socket (301) are aligned. The inner cavity is clearance fit. The joint socket (301) is connected to the second fixed base (2) through the second connecting column (304). The joint socket (301) is provided with a first opening (3011) and a second opening (3012). The first opening (3011) is used to allow one end of the joint head (302) to slide out of the joint socket (301). The side wall of the joint socket (301) near the central auxiliary support module (4) is higher than the opposite side, so that the second opening (3012) is inclined at the top of the joint socket (301).

2. The novel lumbar facet joint prosthesis according to claim 1, characterized in that: The central auxiliary support module (4) includes a protrusion (401) disposed at the center of the first fixed base (1) and a concave block (402) adapted to the protrusion (401). The concave block (402) is disposed on the base (201), and the base (201) is disposed on the second fixed base (2).

3. A novel lumbar facet joint prosthesis according to claim 2, characterized in that: A pad (403) is provided between the recess (402) and the base (201). The pad (403) has a preset thickness. The top and bottom surfaces of the pad (403) are provided with clips (404), which are respectively clipped into the slots (202) on the recess (402) and the base (201). A fixing plate (405) is provided at the end of the clip (404). Two sets of bolts (406) are provided on the fixing plate (405). The two sets of bolts (406) are respectively inserted into the recess (402) and the base (201).

4. A novel lumbar facet joint prosthesis according to claim 3, characterized in that: The top surface of the concave block (402) and the inner cavity of the joint socket (301) are both provided with polymer material bushings.

5. A novel lumbar facet joint prosthesis according to claim 4, characterized in that: A sealing sleeve (407) is provided on the concave block (402), the sealing sleeve (407) covers the protrusion (401), a sealing capsule (305) is provided outside the joint socket (301), the joint socket (301) and the joint head (302) are both covered in the sealing capsule (305), and the first connecting post (303) and the second connecting post (304) both penetrate the sealing capsule (305).

6. A novel lumbar facet joint prosthesis according to claim 5, characterized in that: The first connecting post (303) is slidably inserted into the first fixed base (1), and the second connecting post (304) is slidably inserted into the second fixed base (2). Both the first fixed base (1) and the second fixed base (2) are provided with locking seats (101). The locking seat (101) is provided with a first set screw (102), which is used to lock the first connecting post (303) and the second connecting post (304).

7. A novel lumbar facet joint prosthesis according to claim 1, characterized in that: The first fixing base (1) and the second fixing base (2) are each provided with a fixing module (5). The fixing module (5) includes a fixing block (501), a universal pedicle screw (502) and a No. 2 set screw (503). The fixing block (501) is slidably sleeved on the first fixing base (1) and the second fixing base (2). The top end of the universal pedicle screw (502) passes through one side of the fixing block (501), and the No. 2 set screw (503) passes through the other side of the fixing block (501) to lock the fixing block (501).

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