A bionic intervertebral disc that prevents bulging and replicates the instantaneous trajectory of joint movement.

Abstract

A biomimetic intervertebral disc that prevents bulging and reproduces the instantaneous trajectory of joint movement includes a superior endplate, a core, and a inferior endplate. The upper end of the core is fixed to the lower surface of the superior endplate, and the lower end of the core is fixed to the upper surface of the inferior endplate. The core includes a protective layer, supporting columns, and a nucleus pulposus. The supporting columns have a concave curved surface structure and a negative Poisson's ratio, thereby preventing disc bulging. The supporting columns are divided into four regions: anterior, posterior, left, and right. By adjusting the cross-section and gap size of the supporting columns in each region, the stiffness of different regions of the intervertebral disc can be adjusted. During the compression and deformation process, the nucleus pulposus changes the support point of the superior endplate, causing the rotation center of the vertebral joint to automatically change according to different rotational movements, thus reproducing the motion trajectory of the instantaneous rotation center of the vertebral joint. This invention has the functions of preventing bulging, varying stiffness, and reproducing the motion trajectory of the instantaneous rotation center of the vertebral joint.

Description

Technical Field

[0001] This invention relates to a bionic intervertebral disc that prevents bulging and reproduces the instantaneous trajectory of joint movement, belonging to the field of implantable device technology. Background Technology

[0002] Lumbar disc degeneration is a major cause of chronic low back pain in adults. Clinical data shows that disc rupture is found in 42% of patients with persistent low back pain, and varying degrees of disc degeneration are clearly visible on clinical CT or MRI images in most patients with chronic low back pain. Currently, the main clinical treatments for this condition are lumbar fusion or total disc replacement. However, lumbar fusion can easily lead to loss of spinal segment mobility and increase the risk of degeneration in adjacent segments. Total disc replacement, on the other hand, preserves the range of motion of the spinal segment and significantly reduces the risk of degeneration in adjacent segments, thus becoming a more advanced and effective treatment option.

[0003] Artificial intervertebral discs are crucial instruments implanted into the spine during total disc replacement surgery. Research has found that most commonly used artificial intervertebral discs worldwide are either ball-and-socket or integrated without joints. Ball-and-socket designs cannot effectively constrain axial rotation, and the rotation center of the vertebral segment after implantation is relatively fixed. Unjointed designs, due to the use of homogeneous materials or isotropic structural designs, exhibit uniform deformation in all directions. This results in a mismatch between the instantaneous rotation center trajectory of the vertebral segment after implantation and physiological movement (they can only approximate each other within a certain plane of motion), leading to abnormal intervertebral movement and load transmission. Human biological intervertebral discs, however, possess variable stiffness, allowing for more flexible and natural flexion, extension, lateral bending, and axial rotation. Furthermore, the instantaneous rotation center trajectory varies with physiological rotation. This mismatch in the instantaneous rotation center leads to abnormal intervertebral movement and abnormal stress on posterior muscles, causing postoperative pain. The study also showed that most artificial intervertebral discs are prone to bulging after a certain period of time, often requiring a second surgery and causing great suffering to patients. Therefore, there is an urgent need to develop a biomimetic variable stiffness artificial intervertebral disc that can effectively prevent bulging after implantation in the human spine and can reproduce the instantaneous rotational trajectory of the original healthy intervertebral disc. Summary of the Invention

[0004] To address the technical problems of existing artificial intervertebral discs, this invention provides a bionic intervertebral disc that prevents bulging and replicates the instantaneous trajectory of joint movement. This enables flexion and extension, lateral bending, axial rotation, translation, and their coupled movements between vertebrae, replicating the physiological movement functions of human biological intervertebral discs and solving the problems of instantaneous rotation center movement trajectory and bulging.

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

[0006] Based on the characteristic of negative Poisson's ratio structures to contract under compression and expand under tension, this invention employs a support column with an inwardly concave curved surface structure, which can contract inward under compression in all directions, thereby solving the problem of intervertebral disc bulging. Literature review revealed that in the L2-3 segment of the human lumbar intervertebral disc, the vertebral body flexion angle is approximately 5.9 degrees, extension angle is approximately 2.3 degrees, lateral rotation angles are equal at approximately 0.8 degrees, and lateral bending angles are equal at approximately 3.5 degrees. The range of motion in other segments is similar to that of the L2-3 segment. To achieve the above physiological range of motion of the human lumbar intervertebral disc, this invention can adjust the support strength of different areas of the intervertebral disc by adjusting the cross-section and gap size of the support column, achieving variable stiffness. This better meets the movement characteristics of flexion and extension, lateral bending, and axial rotation, thus replicating the anisotropic functional characteristics of the human intervertebral disc. The three-layered support columns divide the area into four regions: front, rear, left, and right. The front columns have the smallest cross-section and the largest gap; the left and right side columns have larger cross-sections and smaller gaps than the front columns; and the rear columns have the largest cross-section and the smallest gap, thus allowing for the control of stiffness in the four different regions. Furthermore, the nucleus pulposus has a strong deformation capacity. During compression deformation, it interacts with the support columns. The greater the pressure, the more the nucleus pulposus deforms and fills the gaps between the bent support columns, resulting in a larger contact area with them. The support columns also come into contact with each other, forming a unified structure similar to the hydrostatic structure of a human intervertebral disc, making the support more stable. The change in the support center thus replicates the motion trajectory of the instantaneous rotation center of the vertebral joint.

[0007] A biomimetic intervertebral disc that prevents bulging and reproduces the instantaneous trajectory of joint movement includes a superior endplate, a core, and a inferior endplate. The upper end of the core is fixed to the lower surface of the superior endplate, and the lower end of the core is fixed to the upper surface of the inferior endplate. The upper surface of the superior endplate has superior endplate screw teeth, and the lower surface of the inferior endplate has inferior endplate screw teeth. The superior and inferior endplate screw teeth provide initial fixation for the intervertebral disc. The surfaces of the superior and inferior endplates, the superior and inferior endplate screw teeth, and the inferior endplate screw teeth are coated with a hydroxyapatite layer. Because the hydroxyapatite coating has an affinity for bone tissue, it can induce undifferentiated mesenchymal cells to differentiate into osteocytes, thereby achieving secondary fixation of the intervertebral disc.

[0008] The core consists of an outer protective layer, a middle supporting column, and an inner nucleus.

[0009] The protective layer is made of polycarbonate-based polyurethane. When the vertebral body undergoes flexion and extension, lateral bending, axial rotation, translation and their coupled movements, the protective layer will deform accordingly and can recover, thus having strong durability.

[0010] The supporting columns include small supporting columns, left middle supporting columns, large supporting columns, and right middle supporting columns.

[0011] The supporting column has an external planar structure, an internal arc structure, and an inward concave surface. Because the supporting column has an internal gap formed by the inward concave surface, the rotation of the intervertebral disc is achieved through the self-rotation deformation of the supporting column, which is more likely to meet the rotation characteristics of the human biological intervertebral disc. The supporting column has a negative Poisson's ratio characteristic, has a simple structure, and is suitable for solving the problem of intervertebral disc bulging.

[0012] The nucleus pulposus is D-shaped, which increases the stress-bearing area of ​​the nucleus pulposus, making the stress more uniform and avoiding local stress concentration.

[0013] The upper endplate, lower endplate, and core are D-shaped, which better conforms to the shape characteristics of the human intervertebral disc, making the overall force distribution more uniform and the support effect better.

[0014] The supporting column can consist of two or more layers from the outside to the inside. Preferably, the supporting column has three layers from the outside to the inside: an outer supporting column, a middle supporting column, and an inner supporting column, ensuring that the nucleus pulposus has a volume similar to that of a human intervertebral disc. When the intervertebral disc undergoes coupled movements such as rotation or translation, the middle supporting column can provide sufficient gaps to allow the nucleus pulposus 7 to fill it, interacting with the supporting column 16 to form a whole similar to the hydrostatic structure of a human intervertebral disc, achieving a better support effect for the spine.

[0015] The supporting columns are divided into four regions: front, rear, left, and right. In each region, ① represents the cross-section of the small supporting column, ② the cross-section of the medium supporting column, and ③ the cross-section of the large supporting column. The cross-sections of the supporting columns in the four regions, from smallest to largest, are as follows: the cross-section ① of the small supporting column in the front region is smaller than the cross-section ② of the medium supporting column in the left region; the cross-section ② of the medium supporting column in the left region is smaller than the cross-section ③ of the large supporting column in the rear region; and the cross-section ② of the medium supporting column in the left region is equal to the cross-section ② of the medium supporting column in the right region. This layout allows for the easiest forward flexion of the vertebral body, followed by lateral flexion, with a smaller range of motion during posterior extension. The overall range of motion better matches the characteristics of the human intervertebral disc.

[0016] The supporting columns are divided into four regions: front, rear, left, and right. The spacing between the supporting columns in each region, from largest to smallest, is as follows: the largest gap (i) between the front columns is larger than the middle gap (iv) between the left columns; the middle gap (iv) between the left columns is larger than the smallest gap (iii) between the rear columns; and the middle gap (iv) between the left columns is equal to the middle gap (ii) between the right columns. This layout makes forward flexion of the vertebral body easiest, followed by lateral flexion, and results in a smaller range of motion during posterior extension. Overall, the range of motion more readily accommodates the movement characteristics of the human intervertebral disc.

[0017] The upper endplate, lower endplate, upper endplate nail teeth, and lower endplate nail teeth are made of polyetheretherketone polymer material.

[0018] The core material is an agarose hydrogel analog; the supporting column is made of silicone resin, and its stiffness can be adjusted by changing the ratio of the substrate and the curing agent to produce an appropriate load response at a ratio of 10:1.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1. The support column with a concave curved surface structure can contract inward when compressed in all directions, and the new negative Poisson's ratio structure solves the problem of intervertebral disc bulging.

[0021] 2. By adjusting the cross-section and gap size of the supporting columns, the support strength of different areas of the intervertebral disc can be controlled, thereby realizing the variable stiffness characteristics of different areas of the human biological intervertebral disc and replicating the anisotropic physiological activity range of the human intervertebral disc.

[0022] 3. The nucleus pulposus is made of agarose hydrogel, which has strong deformation capacity. During the process of compression and deformation, it interacts with the support column. The greater the pressure, the more stable the support. By changing the center of support, it can reproduce the motion trajectory of the instantaneous rotation center of the vertebral joint. Attached Figure Description

[0023] Figure 1 This is a three-dimensional structural diagram of the present invention;

[0024] Figure 2 This is a front view of the present invention;

[0025] Figure 3 for Figure 2 EE section view;

[0026] Figure 4 A schematic diagram of the structure supporting the columns;

[0027] Figure 5 A schematic diagram of the front small-section support column;

[0028] Figure 6 This is a schematic diagram of the supporting column on the left side at the mid-section.

[0029] Figure 7 This is a schematic diagram of the support column at the right mid-section;

[0030] Figure 8 This is a schematic diagram of the large-section support column at the rear.

[0031] In the diagram: 1-Upper endplate nail teeth; 2-Upper endplate; 3-Upper endplate coating; 4-Core; 5-Lower endplate; 6-Lower endplate coating; 7-Nucleus pulposus; 8-Lower endplate nail teeth; 9-Small support column; 10-Left middle support column; 11-Large support column; 12-External planar structure; 13-Internal arc structure; 14-Concave curved surface; 15-Protective layer; 16-Support column; 17-Right middle support column; Ⅰ-Outer support column; Ⅱ-Middle support column; Ⅲ-Inner support column; ①-Cross-section of small support column; ②-Cross-section of middle support column; ③-Cross-section of large support column; A-Front part; LB-Left side part; RB-Right side part; P-Rear part; i-Large gap between front columns; ii-Middle gap between right side columns; iii-Small gap between rear columns; iv-Middle gap between left side columns. Detailed Implementation

[0032] like Figure 1 As shown, a biomimetic intervertebral disc that prevents bulging and reproduces the instantaneous trajectory of joint movement includes a superior endplate 2, a core 4, and a inferior endplate 5. The upper end of the core 4 is fixed to the lower surface of the superior endplate 2, and the lower end of the core 4 is fixed to the upper surface of the inferior endplate 5. The upper surface of the superior endplate 2 has superior endplate screw teeth 1, and the lower surface of the inferior endplate 5 has inferior endplate screw teeth 8. The superior endplate screw teeth 1 and inferior endplate screw teeth 8 provide initial fixation for the intervertebral disc. The surfaces of the superior endplate 2, inferior endplate 5, superior endplate screw teeth 1, and inferior endplate screw teeth 8 are coated with a hydroxyapatite layer 3. Because the hydroxyapatite coating 3 has an affinity for bone tissue, it can induce undifferentiated mesenchymal cells to differentiate into osteocytes, thereby achieving secondary fixation of the intervertebral disc.

[0033] like Figure 1 , Figure 2 and Figure 3 As shown, the core 4 is composed of an outer protective layer 15, a middle supporting column 16, and an inner nucleus pulposus 7.

[0034] The protective layer 15 is made of polycarbonate-based polyurethane. When the vertebral body undergoes flexion and extension, lateral bending, axial rotation, translation and their coupled movements, the protective layer 15 will deform accordingly and can recover, thus having strong durability.

[0035] like Figure 3 , Figure 5 , Figure 6 , Figure 7 and Figure 8 As shown, the supporting column 16 includes a small supporting column 9, a left middle supporting column 10, a large supporting column 11, and a right middle supporting column 17.

[0036] like Figure 4As shown, the supporting column 16 has an outer planar structure 12, an inner arc structure 13, and an inner concave curved surface 14. Because the supporting column 16 has an internal gap formed by the inner concave curved surface 14, the rotation of the intervertebral disc is achieved through the self-rotation deformation of the supporting column 16, which is more likely to meet the rotation characteristics of the human biological intervertebral disc. The supporting column 16 has a structure with negative Poisson's ratio characteristics, is simple in structure, and is suitable for solving the problem of intervertebral disc bulging.

[0037] like Figure 3 As shown, the nucleus pulposus 7 is "D" shaped, which can increase the stress-bearing area of ​​the nucleus pulposus 7, making the stress more uniform and avoiding local stress concentration.

[0038] like Figure 1 , Figure 2 and Figure 3 As shown, the upper endplate 2, lower endplate 5, and core 4 are "D" shaped, which better conforms to the shape characteristics of the human intervertebral disc, making the overall force distribution more uniform and the support effect better.

[0039] like Figure 3 , Figure 5 , Figure 6 , Figure 7 and Figure 8 As shown, the supporting column 16 can be composed of two or more layers from the outside to the inside. In this embodiment, the supporting column 16 is preferably composed of three layers from the outside to the inside: an outer supporting column I, a middle supporting column II, and an inner supporting column III, ensuring that the nucleus pulposus 7 has a volume similar to that of a human intervertebral disc. When the intervertebral disc undergoes coupled movements such as rotation or translation, the supporting column 16 in the middle can provide sufficient gaps to allow the nucleus pulposus 7 to fill it, interacting with the supporting column 16 to form a whole similar to the hydrostatic structure of a human intervertebral disc, achieving a better support effect for the spine.

[0040] like Figure 3 , Figure 5 , Figure 6 , Figure 7 and Figure 8 As shown, the supporting column 16 forms four regions: a front region A, a rear region P, a left side region LB, and a right side region RB. In these four regions, ① represents the cross-section of the small supporting column, ② represents the cross-section of the medium supporting column, and ③ represents the cross-section of the large supporting column. The cross-sections of the supporting columns 16 in the four regions, from smallest to largest, are as follows: the cross-section ① of the small supporting column in the front region is smaller than the cross-section ② of the medium supporting column in the left side region; the cross-section ② of the medium supporting column in the left side region is smaller than the cross-section ③ of the large supporting column in the rear region; and the cross-section ② of the medium supporting column in the left side region is equal to the cross-section ② of the medium supporting column in the right side region. This layout allows for the easiest forward flexion of the vertebral body, followed by lateral flexion, with a smaller range of motion during posterior extension. The overall range of motion better matches the characteristics of the human intervertebral disc.

[0041] like Figure 3 , Figure 5 , Figure 6 , Figure 7 and Figure 8 As shown, the column gaps in the four regions formed by the supporting columns 16—the front A, rear P, left LB, and right RB—are arranged in descending order of size as follows: the largest gap i between the front columns is larger than the middle gap iv between the left columns; the middle gap iv between the left columns is larger than the smallest gap iii between the rear columns; and the middle gap iv between the left columns is equal to the middle gap ii between the right columns. This layout makes forward flexion of the vertebral body easiest, followed by lateral flexion, and the range of motion is smaller when extending backward. Overall, the range of motion more easily meets the characteristics of human intervertebral disc movement.

[0042] The upper end plate 2, lower end plate 5, upper end plate nail tooth 1 and lower end plate nail tooth 8 are made of polyetheretherketone polymer material;

[0043] The nucleus pulposus 7 is made of an agarose hydrogel analogue; the supporting column 16 is made of silicone resin, and its stiffness can be adjusted by changing the ratio of the substrate and the curing agent to produce an appropriate load response at a ratio of 10:1.

Claims

1. A biomimetic intervertebral disc that prevents bulging and replicates the instantaneous cardiac trajectory of joint movement, characterized by: It includes an upper end plate (2), a core (4) and a lower end plate (5); the upper end of the core (4) is fixed to the lower surface of the upper end plate (2), and the lower end of the core (4) is fixed to the upper surface of the lower end plate (5). The upper surface of the upper end plate (2) has upper end plate nail teeth (1), and the lower surface of the lower end plate (5) has lower end plate nail teeth (8). The core (4) consists of an outer protective layer (15), a middle supporting column (16) and an inner nucleus (7); the supporting column (16) includes a small supporting column (9), a left middle supporting column (10), a large supporting column (11) and a right middle supporting column (17). The supporting column (16) has an external planar structure (12), an internal arc structure (13), and an inward concave curved surface (14); the supporting column (16) consists of two or more layers from the outside to the inside; the supporting column (16) forms four regions: front (A), rear (P), left side (LB), and right side (RB). The cross-sections of the supporting columns (16) in the four regions are arranged in ascending order as follows: the cross-section of the small supporting column in the front region is smaller than the cross-section of the middle supporting column in the left side region, the cross-section of the middle supporting column in the left side region is smaller than the cross-section of the large supporting column in the rear region, and the cross-section of the middle supporting column in the left side region is equal to the cross-section of the middle supporting column in the right side region.

2. The bionic intervertebral disc that prevents bulging and reproduces the instantaneous cardiac trajectory of joint movement according to claim 1, characterized in that: The surfaces of the upper end plate (2), lower end plate (5), upper end plate nail tooth (1) and lower end plate nail tooth (8) are coated with a hydroxyapatite layer (3).

3. The biomimetic intervertebral disc that prevents bulging and reproduces the instantaneous cardiac trajectory of joint movement according to claim 1, characterized in that: The supporting column (16) consists of three layers from the outside to the inside: outer supporting column (Ⅰ), middle supporting column (Ⅱ), and inner supporting column (Ⅲ).

4. The bionic intervertebral disc that prevents bulging and reproduces the instantaneous cardiac trajectory of joint movement according to claim 1, characterized in that: The supporting column (16) has four regions with column gaps: front (A), rear (P), left (LB) and right (RB). The gaps between the supporting columns (16) in each region are arranged from largest to smallest as follows: the large gap (i) between the front columns is larger than the medium gap (iv) between the left columns, the medium gap (iv) between the left columns is larger than the small gap (iii) between the rear columns, and the medium gap (iv) between the left columns is equal to the medium gap (ii) between the right columns.

5. The bionic intervertebral disc that prevents bulging and reproduces the instantaneous cardiac trajectory of joint movement according to claim 1, characterized in that: The nucleus pulposus (7) is of type "D", and the upper endplate (2), lower endplate (5) and core (4) are of type "D".

6. The biomimetic intervertebral disc that prevents bulging and reproduces the instantaneous cardiac trajectory of joint movement according to claim 1, characterized in that: The upper end plate (2), lower end plate (5), upper end plate nail tooth (1) and lower end plate nail tooth (8) are made of polyetheretherketone polymer; The nucleus pulposus (7) is made of agarose hydrogel; The supporting column (16) is made of silicone resin; The protective layer (15) is made of polycarbonate-based polyurethane.

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