A bionic intervertebral disc with mechanical anisotropy

Abstract

A bionic intervertebral disc with mechanical anisotropy includes an upper end plate, a core and a lower end plate, wherein the upper end of the core is fixed to the lower surface of the upper end plate, and the lower end of the core is fixed to the upper surface of the lower end plate. The core includes an outer annulus fibrosus, a transition zone in the middle and an inner nucleus pulposus, wherein the annulus fibrosus is composed of collagen fiber sheets and collagen fibers, wherein the collagen fibers are attached to the surface of the collagen fiber sheets and have an inclination angle, and adjacent collagen fiber sheets are arranged crosswise. The elastic fibers in the transition zone form a honeycomb structure with a matrix layer, wherein the honeycomb grid size of the structure is smaller and more compact near the transition zone of the annulus fibrosus, and the honeycomb grid size near the transition zone of the nucleus pulposus is larger and more sparse. The mechanical properties of different regions of the intervertebral disc are regulated by the difference in the inclination angle and elastic modulus of the collagen fibers in the annulus fibrosus, thereby realizing the anisotropy of the mechanical properties of the intervertebral disc, and further making the bionic intervertebral disc more naturally matched with the physiological movement of the vertebrae after implantation. The present invention has the function of anisotropy of mechanical properties.

Description

Technical Field

[0001] The invention relates to a bionic intervertebral disc with mechanical anisotropy, belonging to the technical field of implant instruments. Background Art

[0002] Degenerative disc disease is a common disease in humans. There are two main treatment methods: traditional treatment and surgical treatment. Traditional treatment methods include physical therapy and drug therapy, and surgical treatment methods include fusion and replacement. For patients with mild symptoms, physical therapy or traditional drug treatment is mainly used. However, since traditional treatment methods can only relieve pain symptoms but cannot completely cure, surgical treatment has gradually become the first choice for patients after traditional treatment methods have not achieved satisfactory results.

[0003] Fusion has the characteristics of maintaining intervertebral height and improving patient pain, but fusion will cause loss of vertebral segmental mobility and accelerate degenerative changes in adjacent vertebral segments; while total disc replacement not only retains the range of motion of the vertebral segments, but also significantly reduces the risk of adjacent segment degeneration, effectively solving the shortcomings of fusion, thus becoming a more advanced and effective treatment option. Currently, the commonly used artificial intervertebral discs in the world are mainly ball-and-socket joint type and integrated type. Almost all of them adopt isotropic structural design or homogeneous materials, which makes their mechanical properties in all directions the same, resulting in the range of motion of the vertebral segment where the intervertebral disc prosthesis is located after implantation. It cannot match the physiological movement, which leads to abnormal intervertebral motion and load transfer, and even causes problems such as sinking and dislocation of the artificial intervertebral disc prosthesis. The available patents for variable stiffness bionic intervertebral discs mainly achieve variable stiffness of the structure by adjusting the elastic modulus of collagen fibers, thus having functional characteristics similar to the anisotropic stiffness of biological intervertebral discs to a certain extent, but they do not take into account the changes in the inclination angles of the collagen fibers of the annulus fibrosus in different regions of the biological intervertebral disc and the structural and material characteristics of the transition zone. Biomechanical studies have shown that the changes in the inclination angles of the collagen fibers of the annulus fibrosus in different regions of the biological intervertebral disc seriously affect the force of the annulus fibrosus and thus affect the overall mechanical anisotropy of the intervertebral disc. At the same time, the transition zone, as the only connecting area between the nucleus pulposus and the annulus fibrosus, also plays an important role in mechanical regulation, especially under low loads. The structural characteristics and material properties of the two are crucial to the mechanical performance of the intervertebral disc. It can be seen that the biological intervertebral disc of the human body has excellent mechanical anisotropy due to the fine structure and material properties of the annulus fibrosus and the transition zone, thus showing different physiological movement patterns, and the current artificial intervertebral disc cannot reproduce this characteristic, resulting in a series of adverse clinical problems after its implantation in the human body; therefore, it is urgent to develop a bionic intervertebral disc with mechanical anisotropy. Summary of the invention

[0004] In order to solve the technical problems existing in the existing artificial intervertebral discs, the present invention provides a bionic intervertebral disc with mechanical anisotropy, which has structural characteristics and material properties similar to those of the human biological intervertebral disc, and can reproduce the characteristics of the mechanical anisotropy of the human biological intervertebral disc, so that the bionic intervertebral disc can match the physiological movement of the vertebrae more naturally after implantation.

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

[0006] The present invention is inspired by the structural characteristics and material properties of a biological intervertebral disc of the human body. The biological intervertebral disc of the human body is composed of an outer annulus fibrosus, a middle transition zone and an inner nucleus pulposus. The annulus fibrosus is composed of collagen fiber sheets and collagen fibers. The collagen fibers are attached to the surface of the collagen fiber sheets and have an inclination angle, and are arranged crosswise between adjacent sheets. The inclination angle is the angle between the collagen fibers and the horizontal plane. The inclination angle of the front part of the intervertebral disc is 20 degrees, and the inclination angle of the back part is 70 degrees. The inclination angle increases from front to back, and the inclination angles on both sides of the sagittal plane of the intervertebral disc are symmetrically distributed. The transition zone includes a matrix layer and elastic fibers. The elastic fibers are attached to the surface of the matrix layer, and the elastic fibers are composed of coarse elastic fibers and fine elastic fibers. The elastic fibers and the matrix layer form a honeycomb structure. The honeycomb grid size of the structure is smaller and more compact near the transition zone of the annulus fibrosus, and the honeycomb grid size is larger and more sparse near the transition zone of the nucleus pulposus. The diameter of the elastic fibers located in the front part of the intervertebral disc is larger than that in the back part, and thin elastic fibers are interspersed between the thick elastic fibers. During the movement of the vertebrae, the nucleus pulposus in the biological intervertebral disc is compressed to produce deformation and expansion, which successively squeezes the honeycomb elastic fibers and fiber rings in the surrounding transition zone. The honeycomb elastic fibers and fiber rings in the transition zone limit the deformation and expansion of the nucleus pulposus through tension. However, due to the different tensions of elastic fibers and collagen fibers in different regions, and the different inclination angles of collagen fibers at different positions of the collagen fiber layer, when limiting the expansion of the nucleus pulposus, the difference in tension at different positions of the intervertebral disc is further magnified, resulting in different deformations at each position of the intervertebral disc, thereby giving the biological intervertebral disc the function of mechanical anisotropy.

[0007] Based on the structural characteristics and material properties of human biological intervertebral discs, a bionic intervertebral disc with mechanical anisotropy includes an upper end plate, a core and a lower end plate; the upper end of the core is fixed to the lower surface of the upper end plate, and the lower end of the core is fixed to the upper surface of the lower end plate; the upper surface of the upper end plate has upper end plate spikes, and the lower surface of the lower end plate has lower end plate spikes, and the upper and lower spikes play a good initial fixation role after the bionic intervertebral disc is implanted.

[0008] The core includes an outer annulus fibrosus, a middle transition zone and an inner nucleus pulposus. The annulus fibrosus is composed of collagen fiber sheets and collagen fibers. The collagen fibers are attached to the surface of the collagen fiber sheets and have an inclination. Adjacent sheets are arranged crosswise. The upper ends of the collagen fibers are closely connected to the upper end plates, and the lower ends of the collagen fibers are closely connected to the lower end plates.

[0009] The transition zone comprises a matrix layer and elastic fibers. The elastic fibers are attached to the surface of the matrix layer and are composed of coarse elastic fibers and fine elastic fibers.

[0010] The elastic fibers in the transition zone and the matrix layer form a honeycomb structure, in which the honeycomb grid size is smaller and more compact near the transition zone of the annulus fibrosus, and the honeycomb grid size is larger and more sparse near the transition zone of the nucleus pulposus. The diameter of the elastic fibers located in the front of the intervertebral disc is larger than that in the back. The front elastic fibers can withstand greater tension than the back. Thin elastic fibers are interspersed between the coarse elastic fibers, and the thin elastic fibers play a major role under low load conditions. The heterogeneous material of the honeycomb elastic fiber tissue in the transition zone can effectively reduce the stress gradient from the outside to the inside of the bionic intervertebral disc.

[0011] The collagen fibers are polymer materials with different elastic moduli, and the elastic moduli change gradually from the front to the back and gradually decrease, and the elastic moduli of the collagen fibers on both sides of the sagittal plane of the intervertebral disc are symmetrically distributed. Since the elastic moduli of the collagen fibers at different positions of each layer of the annulus fibrosus are different, when restricting the expansion of the nucleus pulposus, the annulus fibrosus at different positions have different tensile forces, thereby realizing the anisotropy of the mechanical properties of the intervertebral disc, which is manifested in different degrees of deformation of the intervertebral disc at different positions in terms of external morphology, thereby making the bionic intervertebral disc more naturally matched with the physiological movement of the vertebrae after implantation.

[0012] The fiber ring is divided into an odd-numbered fiber ring and an even-numbered fiber ring; the number of collagen fiber sheets is 4 to 25, and the collagen fiber sheets are odd-numbered collagen fiber sheets and even-numbered collagen fiber sheets.

[0013] The odd-numbered layers of annulus fibrosus include odd-numbered layers of annulus fibrosus collagen fiber sheets and odd-numbered layers of annulus fibrosus collagen fibers. The odd-numbered layers of annulus fibrosus collagen fibers on the right side of the sagittal plane tilt counterclockwise from the bottom end to the top end, and the odd-numbered layers of annulus fibrosus collagen fibers on the left side of the sagittal plane tilt clockwise from the bottom end to the top end.

[0014] The even-numbered layers of annulus fibrosus include even-numbered layers of annulus fibrosus collagen fiber sheets and even-numbered layers of annulus fibrosus collagen fibers. The even-numbered layers of annulus fibrosus collagen fibers on the right side of the sagittal plane tilt clockwise from the bottom end to the top end, and the even-numbered layers of annulus fibrosus collagen fibers on the left side of the sagittal plane tilt counterclockwise from the bottom end to the top end.

[0015] The inclination angle is the angle between the collagen fiber and the horizontal plane. The inclination angle of the front part of the intervertebral disc is 20 degrees, and the inclination angle of the back part is 70 degrees. The inclination angle increases from front to back, and the inclination angles on both sides of the sagittal plane of the intervertebral disc are symmetrically distributed. The collagen fiber inclination angles at different positions of the collagen fiber layer are different. When limiting the expansion of the nucleus pulposus, there are different tensions, thereby realizing the anisotropy of the mechanical properties of the intervertebral disc. When flexing forward (in an ideal state without other coupled movements), the collagen fibers of the odd-numbered layers of the annulus fibrosus at the back of the intervertebral disc are subjected to a tension F along the fiber direction. 后胶原纤维 The tensile force F on the collagen fiber is perpendicular to the horizontal plane. 后 The product of the sine of the collagen fiber inclination angle α, that is, F 后胶原纤维 =F 后 sinα°, the collagen fibers of the even-numbered layers of the annulus fibrosus at the posterior part of the intervertebral disc are subjected to a tensile force F along the fiber direction 后胶原纤维 The tensile force F on the collagen fiber is perpendicular to the horizontal plane. 后 The product of the sine of the collagen fiber inclination angle α, that is, F 后胶原纤维 =F 后 sinα°, the tensile force on the collagen fibers of the odd-numbered layers of the annulus fibrosus is the same as that on the even-numbered layers, and is collectively represented as F 后胶原纤维 , the tension F on the vertical horizontal plane 后 is the joint torque M at the posterior part of the intervertebral disc 后 Divided by the force arm (the front-to-back distance of the intervertebral disc, represented by D), during extension (in an ideal state without other coupled motions), the collagen fibers of the annular fibrous ring in the odd-numbered layers of the anterior part of the intervertebral disc are subjected to a tensile force F along the fiber direction. 前胶原纤维 The tensile force F on the collagen fiber is perpendicular to the horizontal plane. 前 The product of the sine of the collagen fiber inclination angle α, that is, F 前胶原纤维 =F 前 sinα°, the collagen fibers of the even-numbered layers of the annulus fibrosus in the anterior part of the intervertebral disc are subjected to a tensile force F along the fiber direction 前胶原纤维 The tensile force F on the collagen fiber is perpendicular to the horizontal plane. 前 The product of the sine of the collagen fiber inclination angle α, that is, F 前胶原纤维 =F 前 sinα°, the tensile force on the collagen fibers of the odd-numbered layers of the annulus fibrosus is the same as that on the even-numbered layers, and is collectively represented as F 前胶原纤维 , the tension F on the vertical horizontal plane 前 is the joint torque M at the anterior part of the intervertebral disc 前 Divided by the force arm (the anterior-posterior distance of the intervertebral disc, represented by D), the literature survey found that the anterior joint torque M 前 The front joint moment M 后The tension F of the annular fibrous collagen fibers in the front and back of the intervertebral disc along the fiber direction can be expressed as F = M / D sinα°, and the inclination angle of the front of the intervertebral disc is 20 degrees, and the inclination angle of the back is 70 degrees. The tension F of the annular fibrous collagen fibers in the front of the intervertebral disc along the fiber direction is 前 =M / Dsin20°, the tension F of the collagen fibers in the posterior annulus fibrosus along the fiber direction 后 =M / D sin70°, so F 前 <F 后 That is, the range of motion of flexion is greater than that of extension, which is consistent with the data of the range of motion of in vitro cadaver tests. Similarly, under the ideal state of pure lateral bending, the inclination angles on the left and right sides are equal, and the tension of the annular fibrous collagen fibers along the fiber direction on both sides of the intervertebral disc is equal, so the left and right lateral bending ranges of in vitro cadaver tests are basically equal; similarly, the inclination angles of the annular fibrous collagen fibers in different regions of the intervertebral disc are different, so the tension of the annular fibrous collagen fibers along the fiber direction is different, thereby regulating the mechanical anisotropy of different regions of the intervertebral disc.

[0016] The nucleus pulposus is "D" shaped, which can increase the force-bearing area of ​​the nucleus pulposus, make the force more uniform, and avoid local stress concentration. The upper end plate, lower end plate and core are "D" shaped, which is more in line with the appearance characteristics of the human biological intervertebral disc, making the overall force more uniform and the supporting effect better.

[0017] The surface of the upper end plate has an upper end plate coating, the surface of the lower end plate has a lower end plate coating, and the surfaces of the upper end plate nail teeth and the lower end plate nail teeth also have coatings. The above coatings are all made of hydroxyapatite. Since the hydroxyapatite coating has an affinity for bone tissue, it can induce undifferentiated mesenchymal cells to differentiate into osteocytes, thereby achieving the purpose of secondary fixation of the intervertebral disc.

[0018] The material of the upper end plate, the lower end plate, the upper end plate nail teeth and the lower end plate nail teeth is polyetheretherketone polymer, which has good hardness and can avoid the problem of prosthesis sinking caused by end plate rupture.

[0019] The nucleus pulposus material is an agarose hydrogel analog; its stiffness can be adjusted by changing the ratio of the base material and the curing agent to produce an appropriate load response at a ratio of 10:1.

[0020] The collagen fiber sheet is made of polyurethane polymer material, and the collagen fibers are made of polyurethane polymer material.

[0021] The matrix layer is made of polyurethane polymer material.

[0022] The elastic fiber is a polyurethane polymer material.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The mechanical properties of different areas of the intervertebral disc are regulated by the different inclination angles of collagen fibers in different positions, thereby achieving the anisotropy of the mechanical properties of the intervertebral disc, and thus making the bionic intervertebral disc more naturally matched with the physiological movement of the vertebrae after implantation.

[0025] 2. The heterogeneous material of the honeycomb elastic fiber structure in the transition zone can effectively reduce the stress gradient from the outside to the inside of the bionic intervertebral disc, so that it exhibits better mechanical properties under low load, and it also plays an important role in mechanical anisotropy.

[0026] 3. The mechanical properties of different areas of the intervertebral disc are regulated by the combined effect of the elastic modulus and inclination angle of collagen fibers at different positions, thereby achieving the anisotropy of the mechanical properties of the intervertebral disc, and making the bionic intervertebral disc more naturally matched with the physiological movement of the vertebrae after implantation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the three-dimensional structure of the present invention;

[0028] Figure 2 It is a front view of the present invention;

[0029] Figure 3 for Figure 2 BB section view in;

[0030] Figure 4 It is a schematic diagram of the unfolded structure of the odd-numbered ring layers of collagen fiber sheets;

[0031] Figure 5 Schematic diagram of the unfolded structure of the even-numbered ring layers of collagen fiber sheets.

[0032] In the figure: 1-upper endplate nail teeth; 2-upper endplate coating; 3-upper endplate; 4-core; 5-collagen fibers; 6-lower endplate; 7-lower endplate coating; 8-lower endplate nail teeth; 9-front part of the intervertebral disc; 10-odd-numbered annulus fibrosus layers; 11-even-numbered annulus fibrosus layers; 12-collagen fiber sheets; 13-transition zone near annulus fibrosus; 14-transition zone; 15-transition zone near nucleus pulposus; 16-nucleus pulposus; 17-posterior part of the intervertebral disc; 18-sagittal Left side of the sagittal plane; 19- sagittal plane of the intervertebral disc; 20- right side of the sagittal plane; 21- posterior inclination angle 70°; 22- anterior inclination angle 20° of the intervertebral disc; 23- inclination; 24- annulus fibrosus; 25- matrix layer; 26- elastic fibers; 27- honeycomb structure; 28- horizontal plane; 29- odd-numbered layers of collagen fiber sheets; 30- even-numbered layers of collagen fiber sheets; 31- odd-numbered layers of annulus fibrosus collagen fibers; 32- even-numbered layers of annulus fibrosus collagen fibers. DETAILED DESCRIPTION

[0033] Please refer to Figures 1 to 5 As shown, a bionic intervertebral disc with mechanical anisotropy comprises an upper end plate 3, a core 4 and a lower end plate 6; the upper end of the core 4 is fixed to the lower surface of the upper end plate 3, the lower end of the core 4 is fixed to the upper surface of the lower end plate 6, the upper surface of the upper end plate 3 has an upper end plate spike 1, and the lower surface of the lower end plate 6 has a lower end plate spike 8;

[0034] The core 4 includes an outer annulus fibrosus 24, a middle transition zone 14 and an inner nucleus pulposus 16. The annulus fibrosus 24 is composed of collagen fiber sheets 12 and collagen fibers 5. The collagen fibers 5 are attached to the surface of the collagen fiber sheets 12 and have an inclination angle 23. Adjacent sheets are arranged crosswise. The upper ends of the collagen fibers 5 are closely connected to the upper end plates 3, and the lower ends of the collagen fibers 5 are closely connected to the lower end plates 6.

[0035] The transition zone 14 includes a matrix layer 25 and elastic fibers 26. The elastic fibers 26 are attached to the surface of the matrix layer 25. The elastic fibers 26 are composed of coarse elastic fibers and fine elastic fibers.

[0036] The elastic fibers 26 of the transition zone 14 and the matrix layer 25 form a honeycomb structure 27, in which the honeycomb grid size is smaller and more compact near the annulus fibrosus transition zone 13, and the honeycomb grid size is larger and more sparse near the nucleus pulposus transition zone 15; the diameter of the elastic fibers 26 located in the front part 9 of the intervertebral disc is larger than that in the back part 17, and thin elastic fibers are interspersed between the coarse elastic fibers, and the thin elastic fibers play a major role under low load; the heterogeneous material of the elastic fiber 26 tissue in the softer layer of the transition zone 14 can effectively reduce the stress gradient from the outside to the inside of the bionic intervertebral disc.

[0037] The collagen fibers 5 are polymer materials with different elastic moduli. The elastic modulus changes gradually from the front part 9 to the back part 17 of the intervertebral disc and gradually decreases. The elastic modulus of the collagen fibers 5 on both sides of the sagittal plane 19 of the intervertebral disc is symmetrically distributed. Since the elastic moduli of the collagen fibers 5 at different positions of each layer of the annulus fibrosus 24 are different, when restricting the expansion of the nucleus pulposus 16, the annulus fibrosus 24 at different positions have different tensile forces, thereby realizing the anisotropy of the mechanical properties of the intervertebral disc. The external morphology is manifested as different degrees of deformation of the intervertebral disc at different positions, thereby making the bionic intervertebral disc more naturally matched with the physiological movement of the vertebrae after implantation.

[0038] The annulus fibrosus 24 is divided into an odd-numbered annulus fibrosus layer 10 and an even-numbered annulus fibrosus layer 11 ; the number of the collagen fiber sheets 12 is 4 to 25 layers, and in the specific embodiment of the present invention, there are 4 layers, and the collagen fiber sheets 12 are respectively an odd-numbered collagen fiber sheet 29 and an even-numbered collagen fiber sheet 30 .

[0039] The odd-numbered annulus fibrosus 10 comprises an odd-numbered annulus fibrosus collagen fiber sheets 29 and an odd-numbered annulus fibrosus collagen fiber 31. The odd-numbered annulus fibrosus collagen fiber 31 tilts counterclockwise from the bottom end to the top end on the right side 20 of the sagittal plane, and tilts clockwise from the bottom end to the top end on the left side 18 of the sagittal plane.

[0040] The even-numbered annulus fibrosus 11 comprises an even-numbered annulus fibrosus collagen fiber sheets 30 and an even-numbered annulus fibrosus collagen fiber 32. On the right side 20 of the sagittal plane, the even-numbered annulus fibrosus collagen fiber 32 tilts clockwise from the bottom end to the top end. On the left side 18 of the sagittal plane, the even-numbered annulus fibrosus collagen fiber 32 tilts counterclockwise from the bottom end to the top end.

[0041] The inclination angle 23 is the angle between the collagen fiber 5 and the horizontal plane 28. The inclination angle of the front part of the intervertebral disc is 20 degrees 22, and the inclination angle of the back part is 70 degrees 21. The inclination angle increases from front to back, and the inclination angles on both sides of the sagittal plane 19 of the intervertebral disc are symmetrically distributed; the collagen fibers 5 at different positions of the collagen fiber layer 12 have different inclination angles 23, and when limiting the expansion of the nucleus pulposus 16, different tensions are exerted, thereby realizing the anisotropy of the mechanical properties of the intervertebral disc; when flexing forward (in an ideal state without other coupled motions), the collagen fibers 5 of the odd-numbered layers of the annulus fibrosus 10 in the back part 17 of the intervertebral disc are subjected to a tension F along the fiber direction. 后胶原纤维 The tensile force F on the collagen fiber 5 is perpendicular to the horizontal plane 28. 后 The product of the sine of the inclination angle α of the collagen fiber 5, that is, F 后胶原纤维 =F 后 sinα°. The collagen fibers 5 of the even-numbered layers of the annulus fibrosus 11 in the posterior part of the intervertebral disc are subjected to a tensile force F along the fiber direction. 后胶原纤维 The tensile force F on the collagen fiber 5 is perpendicular to the horizontal plane 28. 后 The product of the sine of the collagen fiber inclination angle 23α, that is, F 后胶原纤维 =F 后 sinα°, the tensile force of the odd-numbered layers of annulus fibrosus 10 collagen fibers 5 along the fiber direction is consistent with that of the even-numbered layers, and is collectively expressed as F 后胶原纤维 , the tension F on the vertical horizontal plane 后 is the joint torque M of the posterior disc 17 后 Divided by the force arm (the front-to-back distance of the intervertebral disc, represented by D); during extension (in an ideal state without other coupled motions), the anterior part of the intervertebral disc 9 odd-numbered layers of the annulus fibrosus 10 collagen fibers 5 are subjected to a tensile force F along the fiber direction 前胶原纤维 The tensile force F on the collagen fiber 5 is perpendicular to the horizontal plane 28. 前 The product of the sine of the collagen fiber inclination angle 23α, that is, F 前胶原纤维 =F 前 sinα°; the front part of the intervertebral disc 9 even-numbered layers of the annulus fibrosus 11 collagen fibers 5 are subjected to a tensile force F along the fiber direction 前胶原纤维The tensile force F on the collagen fiber 5 is perpendicular to the horizontal plane 28. 前 The product of the sine of the collagen fiber inclination angle 23α, that is, F 前胶原纤维 =F 前 sinα°, the tensile force of the odd-numbered layers of annulus fibrosus 10 collagen fibers 5 along the fiber direction is consistent with that of the even-numbered layers, and is collectively expressed as F 前胶原纤维 , the tension F on the vertical horizontal plane 28 前 is the joint torque M of the anterior disc 前 Divide by the force arm (the distance between the front and back of the intervertebral disc, represented by D); Literature research found that the joint torque M of the anterior part of the intervertebral disc 前 The front joint moment M 后 The tension F of the annular collagen fibers 5 of the front part 10 and the back part 17 of the intervertebral disc along the fiber direction can be expressed as F = M / D sinα°. The inclination angle 23 of the front part 9 of the intervertebral disc is 20 degrees, and the inclination angle 23 of the back part 17 is 70 degrees. The tension F of the annular collagen fibers 5 of the front part 9 of the intervertebral disc along the fiber direction is 前 =M / Dsin20°, the tension F of the collagen fibers 5 in the annulus fibrosus at the posterior part of the intervertebral disc along the fiber direction 后 =M / D sin70°, so F 前 <F 后 , that is, the range of motion of flexion is greater than that of extension, which is consistent with the range of motion data of the cadaver test; similarly, in the ideal state of pure lateral bending, the inclination angle 23 on the left and right sides is equal, and the tension of the annular fibrous collagen fibers along the fiber direction on both sides of the intervertebral disc is equal, so the range of motion of the left and right lateral bending in the cadaver test is basically equal. Similarly, the inclination angle 23 of the annular fibrous collagen fibers 5 in different regions of the intervertebral disc is different, so the tension of the annular fibrous collagen fibers 5 along the fiber direction is different, thereby regulating the mechanical anisotropy of different regions of the intervertebral disc.

[0042] The nucleus pulposus 16 is "D" shaped, which can increase the stress-bearing area of ​​the nucleus pulposus 16, make the stress more uniform, and avoid local stress concentration; the upper end plate 3, the lower end plate 6 and the core 4 are "D" shaped, which is more in line with the appearance characteristics of the human biological intervertebral disc, making the overall stress more uniform and the supporting effect better.

[0043] The surface of the upper end plate 3 has an upper end plate coating 2, the surface of the lower end plate 6 has a lower end plate coating 7, and the surfaces of the upper end plate nail teeth 1 and the lower end plate nail teeth 8 are also coated. The above coatings are all made of hydroxyapatite. Since the hydroxyapatite coating has an affinity for bone tissue, it can induce undifferentiated mesenchymal cells to differentiate into osteocytes, thereby achieving the purpose of secondary fixation of the intervertebral disc.

[0044] The material of the upper end plate 3, the lower end plate 6, the upper end plate spikes 1 and the lower end plate spikes 8 is polyetheretherketone polymer, which has good hardness and can avoid the problem of prosthesis sinking due to end plate rupture.

[0045] The material of the nucleus pulposus 16 is an agarose hydrogel analog; its stiffness can be adjusted by changing the ratio of the base material and the curing agent to produce an appropriate load response at a ratio of 10:1.

[0046] The collagen fiber sheet 12 is made of polyurethane polymer material, and the collagen fibers 5 are made of polyurethane polymer material.

[0047] The matrix layer 25 is made of polyurethane polymer material. The elastic fiber 26 is made of polyurethane polymer material.

Claims

1. A bionic intervertebral disc with mechanical anisotropy, characterized in that: It comprises an upper end plate (3), a core (4) and a lower end plate (6); the upper end of the core (4) is fixed to the lower surface of the upper end plate (3), the lower end of the core (4) is fixed to the upper surface of the lower end plate (6), the upper surface of the upper end plate (3) has an upper end plate spike tooth (1), and the lower surface of the lower end plate (6) has a lower end plate spike tooth (8); The core (4) includes an outer annulus fibrosus (24), a middle transition zone (14) and an inner nucleus pulposus (16), the annulus fibrosus (24) is composed of collagen fiber sheets (12) and collagen fibers (5), the collagen fibers (5) are attached to the surface of the collagen fiber sheets (12) and have an inclination angle (23), and adjacent sheets are arranged crosswise, the upper ends of the collagen fibers (5) are closely connected to the upper end plate (3), and the lower ends of the collagen fibers (5) are closely connected to the lower end plate (6); The collagen fibers (5) are polymer materials with different elastic moduli, and the elastic modulus changes gradually from the front part (9) to the back part (17) of the intervertebral disc and gradually decreases, and the elastic moduli of the collagen fibers (5) on both sides of the sagittal plane (19) of the intervertebral disc are symmetrically distributed; The transition zone (14) comprises a matrix layer (25) and elastic fibers (26), wherein the elastic fibers (26) are attached to the surface of the matrix layer (25), and the elastic fibers (26) are composed of coarse elastic fibers and fine elastic fibers; The elastic fibers (26) of the transition zone (14) and the matrix layer (25) form a honeycomb structure (27), wherein the honeycomb grid size of the structure is smaller and more compact near the annulus fibrosus transition zone (13), and the honeycomb grid size of the structure is larger and more sparse near the nucleus pulposus transition zone (15), the diameter of the elastic fibers (26) located in the front part (9) of the intervertebral disc is larger than that in the rear part (17), and thin elastic fibers are interspersed between the thick elastic fibers; The inclination angle (23) is the angle between the collagen fiber (5) and the horizontal plane (28), the inclination angle of the front part of the intervertebral disc is 20 degrees (22), and the inclination angle of the back part is 70 degrees (21), the inclination angle increases from front to back, and the inclination angles on both sides of the sagittal plane (19) of the intervertebral disc are symmetrically distributed; The annulus fibrosus (24) is divided into an odd-numbered annulus fibrosus layer (10) and an even-numbered annulus fibrosus layer (11); the number of the collagen fiber sheets (12) is 4 to 25, and the collagen fiber sheets (12) are respectively an odd-numbered collagen fiber sheet (29) and an even-numbered collagen fiber sheet (30); The odd-numbered layers of annulus fibrosus (10) include an odd-numbered layers of annulus fibrosus collagen fiber sheets (29) and an odd-numbered layers of annulus fibrosus collagen fibers (31), wherein the odd-numbered layers of annulus fibrosus collagen fibers (31) are inclined counterclockwise from the bottom end to the top end on the right side (20) of the sagittal plane, and the odd-numbered layers of annulus fibrosus collagen fibers (31) are inclined clockwise from the bottom end to the top end on the left side (18) of the sagittal plane; The even-numbered layers of annulus fibrosus (11) include an even-numbered layers of annulus fibrosus collagen fiber sheets (30) and an even-numbered layers of annulus fibrosus collagen fibers (32). On the right side (20) of the sagittal plane, the even-numbered layers of annulus fibrosus collagen fibers (32) are inclined clockwise from the bottom end to the top end, and on the left side (18) of the sagittal plane, the even-numbered layers of annulus fibrosus collagen fibers (32) are inclined counterclockwise from the bottom end to the top end.

2. The bionic intervertebral disc with mechanical anisotropy according to claim 1, characterized in that: The material of the upper end plate (3), the lower end plate (6), the upper end plate spike teeth (1) and the lower end plate spike teeth (8) is polyetheretherketone polymer; The material of the nucleus pulposus (16) is an agarose hydrogel analog; The collagen fiber sheet (12) is made of a polyurethane polymer material, and the collagen fibers (5) are made of a polyurethane polymer material; The matrix layer (25) is a polyurethane polymer material; The elastic fiber (26) is a polyurethane polymer material.

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