Rigidity-variable mechanical self-adaptive interbody fusion cage

Abstract

The rigidity-variable mechanical self-adaptive interbody fusion cage comprises a deformable structure set and two plate bodies, the deformable structure set is arranged between the two plate bodies, the two plate bodies have a critical point distance value, and when the distance between the two plate bodies is larger than the critical point distance value, a plurality of structure parts of the deformable structure set are separated; the deformable structure group has first rigidity, when the distance between the two plate bodies is smaller than or equal to a critical point distance value, the deformable structure group deforms, part of the structure parts of the deformable structure group abut against each other, the mechanical self-adaptive interbody fusion cage has second rigidity, and the second rigidity is larger than the first rigidity. The fusion cage can adapt to the in-vivo mechanical environment through the rigidity change of the fusion cage, the small rigidity can be shown when the fusion cage deals with a low load, the high rigidity can be shown when the fusion cage bears a high load effect, and therefore the mechanical adaptation degree between the fusion cage and an adjacent vertebral body is improved, mechanical load transmission is optimized, collapse of the adjacent vertebral body is reduced, and fusion of the vertebral bodies is facilitated.

Description

Technical Field

[0001] The present application relates to the field of medical devices, and in particular to a mechanically adaptive intervertebral fusion device with variable stiffness. Background Art

[0002] Intervertebral disc degeneration is a common and frequent disease and one of the causes of low back pain. The disease is common between the ages of 20 and 40, with a prevalence of 37% in people aged 20 and 96% in people aged 80. Intervertebral fusion is an important surgical method for treating spinal degenerative diseases. Intervertebral fusion devices are currently mainly made of metal titanium alloy materials or high molecular polymer PEEK materials with good biocompatibility. The transplanted bone is filled inside to promote the fusion of the upper and lower vertebrae. After surgery, it can not only reduce pressure but also better maintain the intervertebral height and physiological curvature of the cervical spine. Existing studies have shown that the use of intervertebral fusion devices for surgical fusion and intervertebral height reconstruction is conducive to relieving compression and supporting intervertebral height, and has achieved good clinical results in surgery. As an important instrument used in intervertebral fusion, intervertebral fusion devices mainly play the role of restoring intervertebral height and physiological curvature, and bear the load, so as to promote intervertebral bony fusion, thereby reducing the occurrence of a series of complications caused by this.

[0003] Initially, the intervertebral fusion device was cylindrical in shape. In clinical practice, it has many disadvantages, such as small contact area with the end plate, small amount of bone graft, inability to maintain intervertebral height, and easy sinking of the fusion device. It has basically withdrawn from the clinical market. Subsequently, the cubic intervertebral fusion device appeared, which is currently the most commonly used intervertebral fusion device in clinical practice. The cubic intervertebral fusion device has a large bone grafting space and a strong load capacity, but has poor anti-rotational stress and self-stabilization performance. In order to improve the self-stabilization performance of the cubic intervertebral fusion device, a self-locking intervertebral fusion device has been used clinically, such as the two intervertebral fusion devices MC+ and ROI-C of the French LDR company. This fusion device consists of an outer PEEK material box and a titanium alloy bone anchoring sheet. The bone graft can be placed in the center of the box. After implantation, the titanium alloy clip below will be embedded in the lower vertebral body (ROI is embedded in the upper and lower vertebral bodies). Clinical studies have shown that this self-locking intervertebral fusion device achieves good bone fusion, but 9% of patients still experience the phenomenon of the device sinking into the vertebra below. In summary, the intervertebral fusion devices currently on the market are poorly matched with patients and have poor treatment effects. In clinical applications, adjacent segmental vertebral collapse, degeneration, fractures and other phenomena occur frequently. In severe cases, secondary surgery is required, which brings great pain to patients.

[0004] The spine, as the support of the trunk, transmits the gravity of the head and trunk to the pelvis, allowing the trunk to have sufficient physiological movements in three-dimensional space, such as extension, flexion, and axial rotation. When standing in the anatomical position, the pressure on the intervertebral disc is much greater than the weight of the upper body. When sitting, the pressure on the lumbar intervertebral disc is more than three times that of the trunk. The actual load on the intervertebral disc during jumping and other actions can be more than twice that of the static position. Spinal flexion, extension, and lateral flexion can produce extension stress in some parts of the intervertebral disc. The axial torsion of the trunk can also produce shear load on the intervertebral disc, so the pressure on the intervertebral disc is a composite stress of extension, compression, and shear that changes with time. After being implanted in the human body, the intervertebral fusion device will replace the intervertebral disc. The joint between it and the adjacent vertebrae bears and transmits complex mechanical loads in the body. The stiffness of the intervertebral fusion devices currently on the market is constant, which cannot be well matched with the complex mechanical environment in the body, and cannot achieve high-quality transmission of mechanical loads during human movement, resulting in poor mechanical matching between the intervertebral fusion device and the adjacent vertebrae, inducing clinical problems such as collapse, degeneration, and fracture of adjacent segmental vertebrae.

[0005] In view of this, this application is hereby filed. Summary of the invention

[0006] In order to solve one of the above technical problems, the present invention provides a mechanically adaptive intervertebral fusion cage with variable stiffness.

[0007] The present invention adopts the following technical solutions:

[0008] A mechanically adaptive intervertebral fusion cage with variable stiffness, comprising:

[0009] Two plates, the two plates are arranged at intervals, the spacing between the first ends of the two plates is smaller than the spacing between the second ends of the two plates, a plurality of convex racks are arranged on one side of the plate away from the deformable structure group, the convex racks are arranged in sequence along the length direction of the plate, and the convex racks extend along the width direction of the plate;

[0010] A deformable structure group, wherein the deformable structure component is arranged between the two plates;

[0011] The two plates have a critical point spacing value, when the spacing between the two plates is greater than the critical point spacing value, the multiple structural parts of the deformable structural group are separated, the deformable structural group has a first stiffness, when the spacing between the two plates is less than or equal to the critical point spacing value, the deformable structural group is deformed, some structural parts of the deformable structural group are in contact, and the mechanically adaptive intervertebral fusion cage has a second stiffness;

[0012] Wherein, the second stiffness is greater than the first stiffness.

[0013] Optionally, the plate body and the deformable structure group are integrally formed, and when the two plate bodies are brought closer together, part of the structure of the deformable structure group moves toward each other along the arrangement direction of the two plate bodies until they abut against each other;

[0014] And / or, when the two plates are approaching each other, part of the structural parts of the deformation structure group moves toward each other along a direction perpendicular to the arrangement of the two plates until they abut against each other.

[0015] Optionally, among the structural parts, at least some of the adjacent structural parts have undercut structures formed by being recessed toward each other;

[0016] When the distance between the two plates is greater than the critical point distance value, there is a gap between the undercut structures of adjacent structural parts;

[0017] When the distance between the two plates is equal to or less than the critical point distance value, the undercut structures of the adjacent structural parts offset each other.

[0018] Optionally, the undercut structure comprises a first inclined portion and a second inclined portion;

[0019] There is an angle between the first inclined portion and the second inclined portion;

[0020] One end of the first inclined portion and the second inclined portion are connected to form an abutment portion, and the other end of the first inclined portion and the second inclined portion are separated;

[0021] When the distance between the two plates is greater than the critical point distance value, the abutment parts of the adjacent structural parts are separated;

[0022] When the distance between the two plates is less than or equal to the critical point distance value, at least some of the adjacent structural parts abut against each other.

[0023] Optionally, a plurality of undercut structures are arranged on each of the structural parts, and the undercut structures are arranged in sequence along the arrangement direction of the two plates;

[0024] At least some of the undercut structures on adjacent structural parts correspond to each other in position;

[0025] When the distance between the two plates is greater than the critical point distance value, each of the opposite undercut structures on the adjacent structural parts has a gap;

[0026] When the distance between the two plates is less than or equal to the critical point distance value, the abutting tops of the opposite undercut structures on the adjacent structural parts abut against each other.

[0027] Optionally, the adjacent undercut structures in the undercut structures on each of the structural parts are respectively recessed in different directions;

[0028] When the distance between the two plates is less than or equal to the critical point distance value, two adjacent undercut structures on the structural part respectively abut against corresponding undercut structures on the structural parts at both sides.

[0029] Optionally, a connecting beam is connected between two adjacent structural parts.

[0030] Optionally, two undercut structures in two adjacent structural parts that are at least partially recessed in directions away from each other are connected by the connecting beam.

[0031] Optionally, the structural part is in any one of a sheet shape, a strip shape, and a three-dimensional structure formed by connecting a plurality of strips.

[0032] Optionally, the structural parts are arranged in sequence along the length direction of the plate body;

[0033] Alternatively, the structural parts are arranged along the length direction and the width direction of the plate body, and when the spacing between the two plate bodies is greater than the critical point spacing value, adjacent structural parts have a gap along the length direction of the plate body, and adjacent structural parts have a gap along the width direction of the plate body; when the spacing between the two plate bodies is less than or equal to the critical point spacing value, several adjacent structural parts offset each other along the length direction of the plate body, and several adjacent structural parts offset each other along the width direction of the plate body.

[0034] By adopting the above technical solution, the present application has the following beneficial effects:

[0035] The fusion device of the present application can adapt to the internal mechanical environment by changing its own stiffness. It can show lower stiffness when dealing with low loads and higher stiffness when subjected to high loads, thereby improving the mechanical adaptability with adjacent vertebrae, optimizing mechanical load transfer, reducing adjacent vertebral collapse, and promoting vertebral fusion.

[0036] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are part of this application and are used to provide a further understanding of the present invention. The illustrative embodiments of the present invention and their descriptions are used to explain the present invention, but do not constitute an improper limitation of the present invention. Obviously, the drawings described below are only some embodiments. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work. In the drawings:

[0038] Figure 1 A side view of a first mechanically adaptive intervertebral fusion device with variable stiffness provided by an embodiment of the present application is shown;

[0039] Figure 2 A three-dimensional perspective view of a first mechanically adaptive intervertebral fusion device with variable stiffness provided in an embodiment of the present application is shown;

[0040] Figure 3 A three-dimensional perspective view of a second mechanically adaptive intervertebral fusion device with variable stiffness provided in an embodiment of the present application is shown;

[0041] Figure 4 Another stereoscopic view of the third mechanically adaptive intervertebral fusion device with variable stiffness provided by an embodiment of the present application is shown;

[0042] Figure 5 Shows Figure 4 A side view of a third variable stiffness mechanically adaptive interbody fusion cage is shown;

[0043] Figure 6 Shows Figure 4 A front view of a third variable stiffness mechanically adaptive interbody fusion cage is shown;

[0044] Figure 7 A schematic structural diagram of a deformable structure group of a fourth mechanically adaptive intervertebral fusion device with variable stiffness provided by an embodiment of the present disclosure is shown;

[0045] Figure 8 A state diagram showing a fourth mechanically adaptive intervertebral fusion cage with variable stiffness provided by an embodiment of the present disclosure being implanted in a vertebral body;

[0046] Fig. 9 A schematic structural diagram of a deformable structure group of a fifth mechanically adaptive intervertebral fusion device with variable stiffness provided by an embodiment of the present disclosure is shown;

[0047] Fig.10 A state diagram showing a fifth mechanically adaptive intervertebral fusion cage with variable stiffness provided by an embodiment of the present disclosure being implanted in a vertebral body;

[0048] Fig.11 A schematic structural diagram of a sixth deformable structure group of a mechanically adaptive intervertebral fusion device with variable stiffness provided by an embodiment of the present disclosure is shown;

[0049] Fig.12 A schematic structural diagram of a deformable structure group of a seventh mechanically adaptive intervertebral fusion device with variable stiffness provided by an embodiment of the present disclosure is shown.

[0050] In the figure: 100, intervertebral fusion cage; 1, plate body; 2, deformable structure group; 21, structure part; 21a, through hole; 211, undercut structure; 211a, first inclined part; 211b, second inclined part; 211c, abutment top; 22, connecting beam; 200, cone.

[0051] It should be noted that these drawings and textual descriptions are not intended to limit the conceptual scope of the present invention in any way, but are intended to illustrate the concept of the present invention for those skilled in the art by referring to specific embodiments. DETAILED DESCRIPTION

[0052] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. The following embodiments are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0053] In the description of the present invention, it should be noted that the terms "upper", "lower", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or component referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention.

[0054] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] See also Figures 1 to 12As shown, the present application provides a mechanically adaptive intervertebral fusion device 100 with variable stiffness, comprising: two plates 1 and a deformable structure group 2. The two plates 1 are arranged at intervals, and the spacing between the first ends of the two plates 1 is smaller than the spacing between the second ends of the two plates 1. A plurality of convex racks are arranged on the side of the plate 1 away from the deformable structure group, and each of the convex racks is arranged in sequence along the length direction of the plate 1, and the convex racks extend along the width direction of the plate 1. The two plates 1 are used to cooperate with the upper and lower vertebrae respectively, and the deformable structure group 2 is arranged between the two plates 1. The deformable structure group 2 can have a plurality of structural parts 21, and each structural part 21 can be connected to each other or independent of each other. Each structural part 21 can also be partially connected and partially independent. In the process of relative movement of the two plates 1, each structural part 21 can move relative to each other and change position. The two plates 1 have a critical point spacing value. When the spacing between the two plates 1 is greater than the critical point spacing value, the multiple structural parts 21 of the deformable structural group 2 are separated, and the deformable structural group 2 has a first stiffness. When the spacing between the two plates 1 is less than or equal to the critical point spacing value, the deformable structural group 2 is deformed, and at least some of the structural parts 21 of the deformable structural group are in contact with each other, and the mechanically adaptive intervertebral fusion cage has a second stiffness. The second stiffness is greater than the first stiffness.

[0056] It should be noted that the first stiffness and the second stiffness can be a single value or a range.

[0057] The surgeon can implant the intervertebral fusion cage 100 provided in the present application between the cones 200 inside the human body with the help of a clamp, and can implant nail rods on the outside of the vertebral body 200 to fix the cone to achieve a stabilizing effect. Figure 8 and Fig.10 The two state diagrams of the intervertebral fusion cages 100 provided in the embodiments of the present application being implanted into the vertebral body 200 are respectively illustrated.

[0058] The fusion device of the present application can adapt to the internal mechanical environment by changing its own stiffness. It can show lower stiffness when dealing with low loads and higher stiffness when subjected to high loads, thereby improving the mechanical adaptability with adjacent vertebrae, optimizing mechanical load transfer, reducing adjacent vertebral collapse, and promoting vertebral fusion.

[0059] In some possible implementations, see Figure 7 , Fig.11 and Fig.12As shown, the plate body and the deformable structure group are integrally formed. When the two plate bodies 1 are brought closer together, a partial structural portion 21 (the position indicated by reference numeral 211) of the deformable structure group moves toward each other along the arrangement direction (such as the up and down direction) of the two plate bodies 1, that is, moves roughly along the thickness direction of the plate body 1 until they collide with each other, thereby causing a sudden change in the stiffness of the intervertebral fusion device to facilitate bearing high loads.

[0060] In some possible implementations, see Figures 1 to 6 as well as Fig. 9 As shown, when the two plates 1 are approaching each other, the partial structural portion 21 of the deformation structure group moves toward each other along a direction perpendicular to the arrangement of the two plates 1 , that is, moves approximately along the length direction of the plates 1 until they collide with each other.

[0061] See also Figure 7 As shown, in the process of the two plates 1 approaching each other, the partial structure part 21 (the position indicated by the reference numeral 211) of the deformation structure group moves toward each other along the arrangement direction (such as the up-down direction) of the two plates 1 until they abut against each other. The partial structure part 21 of the deformation structure group moves toward each other along the arrangement direction perpendicular to the two plates 1, that is, moves approximately along the length direction of the plates 1 until they abut against each other.

[0062] When the intervertebral fusion device is under a small load, a large number of structural parts 21 of the deformable structural group have gaps between each other and are not in contact. The entire intervertebral fusion device has low elasticity and is easy to deform, and the reaction force on the vertebral middle plate is small. If the patient lifts heavy objects, the intervertebral fusion device is subjected to a large force, and the two plates 1 are close to each other until a large number of structural parts 21 are against each other, and the stiffness of the intervertebral fusion device suddenly increases, and the supporting performance is significantly improved.

[0063] In some possible embodiments, among the structural portions 21, at least some adjacent structural portions 21 have side concave structures 211 that are recessed toward each other, and when the spacing between the two plate bodies 1 is greater than the critical point spacing value, there is a gap between the side concave structures 211 of adjacent structural portions 21, and when the spacing between the two plate bodies 1 is equal to or less than the critical point spacing value, the side concave structures 211 of adjacent structural portions 21 offset each other.

[0064] The structure of the undercut structure 211 itself is not straight, and it is easy to deform after being subjected to force. When the undercut structure 211 extends along the first direction as a whole, when the two ends of the undercut structure 211 are subjected to a force of compression, the undercut structure 211 can bulge in the second direction. That is, when the undercut structure 211 is subjected to an external force in the first direction, it will obviously deform and move in the second direction. The first direction and the second direction can be perpendicular to each other. One of the first direction and the second direction can be the thickness direction of the plate body 1, and the other can be the length direction of the plate body 1.

[0065] In some possible implementations, see Figure 1 As shown, the undercut structure 211 includes a first inclined portion 211a and a second inclined portion 211b, and there is an angle between the first inclined portion 211a and the second inclined portion 211b. One end of the first inclined portion 211a and the second inclined portion 211b are connected to form an abutment top portion 211c, and the other ends of the first inclined portion 211a and the second inclined portion 211b are separated. When the spacing between the two plates 1 is greater than the critical point spacing value, the abutment top portions 211c of the adjacent structural portions 21 are separated. When the spacing between the two plates 1 is less than or equal to the critical point spacing value, at least some of the abutment top portions 211c of the adjacent structural portions 21 abut against each other. The first inclined portion 211a and the second inclined portion 211b can be a straight structure, or an arc-shaped structure, etc., and the present application does not limit the specific structure of the inclined portion.

[0066] It should be noted that when the distance between the two plates 1 is less than or equal to the critical point distance value, the structural parts 21 can be in pairs, that is, the structural parts 21 can be in pairs, or multiple structural parts 21 can be in contact with each other.

[0067] In some possible implementations, see Figures 4 to 6 As shown, a plurality of undercut structures 211 are arranged on each of the structural portions 21, and the undercut structures 211 are arranged in sequence along the arrangement direction of the two plate bodies 1, and at least some of the undercut structures 211 on adjacent structural portions 21 correspond to each other in one-to-one position. When the spacing between the two plate bodies 1 is greater than the critical point spacing value, the opposite undercut structures 211 on the adjacent structural portions 21 have gaps, and when the spacing between the two plate bodies 1 is less than or equal to the critical point spacing value, the abutting top portions 211c of the opposite undercut structures 211 on the adjacent structural portions 21 abut against each other.

[0068] These structures can be independent of each other and connected to the plate body 1, or they can be connected to each other to form a complex overall structure. When the distance between the two plate bodies 1 is large, multiple side concave structures 211 can be provided on the structure part 21. The structure part 21 can be roughly wavy, and the two ends are respectively connected to the two plate bodies 1. Providing more side concave structures 211 on the structure part 21 is conducive to increasing the stability of the intervertebral fusion cage.

[0069] Specifically, the adjacent undercut structures 211 of the undercut structures 211 on each of the structural parts 21 are respectively recessed in different directions, and when the spacing between the two plates 1 is less than or equal to the critical point spacing value, the two adjacent undercut structures 211 on the structural part 21 are respectively abutted against the corresponding undercut structures 211 on the structural parts 21 on both sides. By setting the adjacent undercut structures 211 to be recessed in different directions, the density of the effective abutting top 211c can be increased, the stability of the intervertebral fusion device is increased, the service life of the intervertebral fusion device is extended, and the reliability of the intervertebral fusion device is improved.

[0070] In some possible implementations, see Figure 5 , Figure 6 and Fig.11 A connecting beam 22 is connected between two adjacent structural parts 21. Thus, each structural body is connected to form an integral structure, so that the deformation of the deformable structural body is controllable, and the deformation dislocation of the deformable structural group 2 in the length direction of the plate body 1 is prevented from being too large, and the stability of the deformable structural group 2 is further improved.

[0071] Specifically, the two side concave structures 211 in two adjacent structural parts 21 that are at least partially concave in the direction away from each other are connected by the connecting beam 22. The distance between the abutting tops 211c between the two side concave structures 211 that are concave in the direction away from each other is relatively large, and each is suitable for setting a connecting beam 22, and the connecting beam 22 is connected to the concave side of the abutting top 211c, which does not affect the abutting cooperation between the abutting top 211c and the corresponding abutting top 211c in the adjacent structural part 21.

[0072] In some possible implementations, the structure part 21 is in any of a sheet, a strip, and a three-dimensional structure formed by connecting multiple strips. The structure of the present application can be in different shapes, and the present application does not limit the specific structure of the structure part 21. When the structure 21 is in a sheet shape, a through hole 21a can be opened in the structure 21.

[0073] In some possible implementations, see Figures 4 to 6 As shown, each of the structural parts 21 is arranged in sequence along the length direction of the plate body 1, or each of the structural parts 21 is arranged along the length direction and the width direction of the plate body 1. When the distance between the two plates 1 is greater than the critical point distance value, see Figure 5 As shown, in the length direction of the plate body 1, adjacent structural parts 21 have a gap, see Figure 6 As shown, there is a gap between adjacent structural parts 21 in the width direction of the plate body 1. When the distance between the two plate bodies 1 is less than or equal to the critical point distance value, several adjacent structural parts 21 abut against each other in the length direction of the plate body 1, and several adjacent structural parts 21 abut against each other in the width direction of the plate body 1.

[0074] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this patent can make some changes or modify the technical contents suggested above into equivalent embodiments without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the solution of the present invention.

Claims

1. A mechanically adaptive intervertebral fusion cage with variable stiffness, characterized in that: include: Two plates, the two plates are arranged at intervals, the spacing between the first ends of the two plates is smaller than the spacing between the second ends of the two plates, a plurality of convex racks are arranged on one side of the plate away from the deformable structure group, the convex racks are arranged in sequence along the length direction of the plate, and the convex racks extend along the width direction of the plate; A deformable structure group, wherein the deformable structure component is arranged between the two plates; The two plates have a critical point spacing value, when the spacing between the two plates is greater than the critical point spacing value, the multiple structural parts of the deformable structural group are separated, the deformable structural group has a first stiffness, when the spacing between the two plates is less than or equal to the critical point spacing value, the deformable structural group is deformed, some structural parts of the deformable structural group are in contact, and the mechanically adaptive intervertebral fusion cage has a second stiffness; Wherein, the second stiffness is greater than the first stiffness.

2. The mechanically adaptive intervertebral fusion cage with variable stiffness according to claim 1, characterized in that: The plate body and the deformable structure group are integrally formed, and when the two plate bodies are brought close to each other, part of the structure of the deformable structure group moves toward each other along the arrangement direction of the two plate bodies until they abut against each other; And / or, when the two plates are approaching each other, part of the structural parts of the deformation structure group moves toward each other along a direction perpendicular to the arrangement of the two plates until they abut against each other.

3. The mechanically adaptive intervertebral fusion cage with variable stiffness according to claim 1, characterized in that: Among the structural parts, at least some of the adjacent structural parts have undercut structures formed by being recessed toward each other; When the distance between the two plates is greater than the critical point distance value, there is a gap between the undercut structures of adjacent structural parts; When the distance between the two plates is equal to or less than the critical point distance value, the undercut structures of the adjacent structural parts offset each other.

4. The mechanically adaptive intervertebral fusion cage with variable stiffness according to claim 3, characterized in that: The undercut structure comprises a first inclined portion and a second inclined portion; There is an angle between the first inclined portion and the second inclined portion; One end of the first inclined portion and the second inclined portion are connected to form an abutment portion, and the other end of the first inclined portion and the second inclined portion are separated; When the distance between the two plates is greater than the critical point distance value, the abutting tops of the adjacent structural parts are separated; When the distance between the two plates is less than or equal to the critical point distance value, at least some of the adjacent structural parts abut against each other.

5. The mechanically adaptive intervertebral fusion cage with variable stiffness according to claim 3, characterized in that: A plurality of undercut structures are arranged on each of the structural parts, and the undercut structures are arranged in sequence along the arrangement direction of the two plates; At least some of the undercut structures on adjacent structural parts correspond to each other in position; When the distance between the two plates is greater than the critical point distance value, each of the opposite undercut structures on the adjacent structural parts has a gap; When the distance between the two plates is less than or equal to the critical point distance value, the abutting tops of the opposite undercut structures on the adjacent structural parts abut against each other.

6. The mechanically adaptive intervertebral fusion cage with variable stiffness according to claim 5, characterized in that: Adjacent undercut structures in each of the undercut structures on each of the structural parts are respectively recessed in different directions; When the distance between the two plates is less than or equal to the critical point distance value, two adjacent undercut structures on the structural part respectively abut against corresponding undercut structures on the structural parts at both sides.

7. The mechanically adaptive intervertebral fusion cage with variable stiffness according to claim 6, characterized in that: A connecting beam is connected between two adjacent structural parts.

8. The mechanically adaptive intervertebral fusion cage with variable stiffness according to claim 7, characterized in that: The two undercut structures in two adjacent structural parts, which are at least partially recessed in directions away from each other, are connected by the connecting beam.

9. The mechanically adaptive intervertebral fusion cage with variable stiffness according to any one of claims 1 to 8, characterized in that: The structural part is in any one of a sheet shape, a strip shape, and a three-dimensional structure formed by connecting a plurality of strips.

10. The mechanically adaptive intervertebral fusion cage with variable stiffness according to any one of claims 1 to 8, characterized in that: The structural parts are arranged in sequence along the length direction of the plate body; Alternatively, the structural parts are arranged along the length direction and the width direction of the plate body, and when the spacing between the two plate bodies is greater than the critical point spacing value, adjacent structural parts have a gap along the length direction of the plate body, and adjacent structural parts have a gap along the width direction of the plate body; when the spacing between the two plate bodies is less than or equal to the critical point spacing value, several adjacent structural parts offset each other along the length direction of the plate body, and several adjacent structural parts offset each other along the width direction of the plate body.

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