Interbody fixation device

Abstract

One embodiment of the present invention is an interbody fixation device to be inserted into an intervertebral space between an upper vertebral body and a lower vertebral body. The interbody fixation device includes a plurality of independent elastic members each having a pair of upper and lower contact surfaces configured to be in contact with the endplates of the upper and lower vertebral bodies. Each of the plurality of elastic members has elasticity between the pair of upper and lower contact surfaces. When the vertebral endplates above and below an intervertebral disc space in which the interbody fixation device is implanted are partially fractured (damaged), an elastic member in contact with the fractured part sinks, while propagation of sinking to the other elastic members is suppressed, thereby ensuring stable retention. This makes it possible to provide an interbody fixation device that can be stably retained after implantation, even in cases in which vertebral body bones constituting the intervertebral disc space are fragile due to osteoporosis or the like.

Description

Intervertebral internal fixation device

[0001] The present invention relates to an intervertebral internal fixation device to be inserted and implanted between vertebrae.

[0002] Currently in Japan, the demand for spinal fixation surgery and artificial disc replacement surgery for the elderly is increasing. Spinal fixation surgery is a treatment method for fixing the upper and lower intervertebral discs by implanting a spinal cage, which is a dedicated instrument, into the narrowed intervertebral space (intervertebral disc cavity). The spinal cage is a cage-shaped instrument inserted between vertebrae. While maintaining the height of the intervertebral space, it is intended to be used by putting bone material into the cage to promote the regeneration and fusion of vertebrae. On the other hand, artificial disc replacement surgery is a treatment method for removing a damaged intervertebral disc from the intervertebral disc cavity due to aging, disease, or accident and replacing it with an artificial intervertebral disc. It is ideal for the artificial intervertebral disc to have flexibility comparable to that of the patient's own healthy intervertebral disc, and it is intended to be used to quickly restore the mobility of the affected spine and ultimately restore the quality of life of the patient.

[0003] Patent Document 1 discloses an intervertebral spacer used in spinal fixation surgery and inserted between vertebrae, which is said to have sufficient strength not only against compressive forces from above but also against forces exerted in the anteroposterior and lateral directions.

[0004] Patent Document 2 discloses an implant that is said to provide both minimal deformation over time under pressure and space for bone ingrowth. The implant includes a main body having an annular portion with an opening. The main body defines a cross-section that divides the implant into an upper half and a lower half, and the annular portion defines a radial direction and a circumferential direction. The implant is configured to include a bone contact member attached to the annular portion and extending radially therefrom, and a support member attached to the bone contact member in the attachment region and extending circumferentially (see FIG. 5 of the same document).

[0005] Patent Document 3 discloses an intervertebral implant that is said to provide good fusion, enabling simplified insertion and gradual expansion of the intervertebral space. It is said to consist of an upper wall and a lower wall that engage with the upper and lower vertebral endplates, respectively, and a load transmission part configured to transmit load between the upper and lower walls, and can exhibit a compression state in which the distance between the upper and lower walls is reduced and a protruding state in which the distance is increased.

[0006] Patent Document 4 discloses an intervertebral implant that is said to be easy to handle due to its simple design. Similar to the intervertebral implant disclosed in Patent Document 3, this intervertebral implant is also composed of an upper wall and a lower wall that engage with the upper and lower vertebral endplates respectively, and a load transmission part configured to transmit load between the upper wall and the lower wall, and is said to be able to exhibit a compression state in which the distance between the upper wall and the lower wall is reduced and a protruding state in which the distance is increased.

[0007] Japanese Patent Publication No. 2022-094273, Japanese Patent Publication No. 2022-171947, Japanese Patent Publication No. 2017-000753, Japanese Patent Publication No. 2013-132557

[0008] The intervertebral spacer disclosed in Patent Document 1 and the implant disclosed in Patent Document 2 are classified as spinal cages as described above. They are used to promote vertebral regeneration and fusion by fixing the upper and lower intervertebral discs while maintaining the height of the intervertebral space, and therefore require rigidity, but do not allow for spinal mobility. The intervertebral implants disclosed in Patent Documents 3 and 4 are classified as artificial intervertebral discs as described above. They are elastic and are embedded between vertebral bodies with the aim of restoring the mobility of the affected area of ​​the spine.

[0009] The inventor of this invention, an orthopedic surgeon, noticed that conventional spinal cages and artificial intervertebral discs have the following problems when used to treat intervertebral disc damage or degeneration accompanied by osteoporosis due to aging, etc. Specifically, if a micro-fracture occurs on a part of the surface that contacts the upper and lower vertebral endplates of a conventional spinal cage or artificial intervertebral disc, that fracture may spread to the surrounding area, and there is a risk that the spinal cage or artificial intervertebral disc will sink into the vertebral body.

[0010] In this specification, the spinal cage and artificial intervertebral disc are collectively referred to as intervertebral body fixation devices, and the object of the present invention is to provide an intervertebral body fixation device that can be stably held in place when implanted, even in cases where the vertebral bone constituting the intervertebral disc space is fragile due to osteoporosis or the like.

[0011] The means for solving these problems are described below, but other problems and novel features will become clear from the description and accompanying drawings in this specification.

[0012] According to one embodiment of the present invention, the following applies:

[0013] In other words, it is an intervertebral body fixation device inserted into the intervertebral space between the upper and lower vertebral bodies, and is configured as follows.

[0014] The intervertebral body internal fixation device comprises a base structure extending in the short axis direction at both ends in the long axis direction, a support beam connecting the base structures, and one or more pairs of upper and lower elastic plates extending in the long axis direction and supported by the base structures or the support beams.

[0015] Each of the elastic plates has a contact surface for contacting the endplate of the upper or lower vertebral body, and the contact surfaces are arranged to form surfaces that are generally continuous in the longitudinal direction from the base structure on the upper and lower sides, respectively.

[0016] The intervertebral body internal fixation device is such that the elastic plate can flex in both the vertical and longitudinal directions in response to a vertical load.

[0017] The effects obtained by the above embodiment can be briefly described below.

[0018] In other words, it is possible to provide an intervertebral body fixation device that can be stably held in place when implanted, even in cases where the vertebral bone constituting the intervertebral disc space is fragile due to osteoporosis or other reasons.

[0019] Figure 1 is an explanatory diagram showing one example configuration of the intervertebral body internal fixation device of the present invention. Figure 2 is a perspective view showing one example configuration of the intervertebral body internal fixation device of the present invention. Figure 3 is an explanatory diagram showing the operating principle of the intervertebral body internal fixation device of the present invention. Figure 4 is an explanatory diagram showing an example configuration of the intervertebral body internal fixation device according to the second embodiment of the present invention. Figure 5 is an explanatory diagram showing an example configuration of the intervertebral body internal fixation device according to the third embodiment of the present invention. Figure 6 is an explanatory diagram showing an example configuration of the intervertebral body internal fixation device according to the fourth embodiment of the present invention. Figure 7 is an explanatory diagram showing an example configuration of the intervertebral body internal fixation device according to the fifth embodiment of the present invention. Figure 8 is an explanatory diagram showing an example configuration of the intervertebral body internal fixation device according to the sixth embodiment of the present invention. Figure 9 is an explanatory diagram showing one example configuration of the intervertebral body internal fixation device according to the seventh embodiment of the present invention. Figure 10 is an explanatory diagram showing another example configuration of the intervertebral body internal fixation device according to the seventh embodiment of the present invention. Figure 11 is an explanatory diagram showing one example configuration of the intervertebral body internal fixation device according to the eighth embodiment of the present invention. Figure 12 is an explanatory diagram showing one example configuration of the intervertebral body internal fixation device according to the ninth embodiment of the present invention. Figure 13 is an image diagram showing a perspective view of one example of the configuration of an intervertebral body fixation device according to the 10th embodiment of the present invention. Figure 14 is an explanatory diagram showing an example of the configuration of the main body portion of the intervertebral body fixation device according to the 10th embodiment of the present invention. Figure 15 is an explanatory diagram showing an example of the configuration of the expansion portion and expansion mechanism of the intervertebral body fixation device according to the 10th embodiment of the present invention. Figure 16 is an image diagram showing a perspective view of one example of the configuration of an intervertebral body fixation device according to the 11th embodiment of the present invention. Figure 17 is an explanatory diagram showing an exploded perspective view of an example of the configuration of the main body portion and expansion portion (second and third elastic members and control rod) of the intervertebral body fixation device according to the 11th embodiment of the present invention. Figure 18 is an explanatory diagram showing in detail an example of the configuration of an intervertebral body fixation device according to the 11th embodiment of the present invention (storage state). Figure 19 is an explanatory diagram showing in detail an example of the configuration of an intervertebral body fixation device according to the 11th embodiment of the present invention (protruding state). Figure 20 is an explanatory diagram of the mechanism for transitioning the intervertebral body fixation device according to the 11th embodiment of the present invention from the storage state to the protruding state. Figure 21 is an explanatory diagram showing another configuration example and expansion mechanism of the expansion portion of the intervertebral body internal fixation device according to the 11th embodiment of the present invention. Figure 22 is an explanatory diagram schematically showing the solution principle of the present invention.Figure 23 is a schematic diagram illustrating the mechanism of deformation limitation by adjacent elastic members. Figure 24 is a schematic diagram illustrating the principle of contact surface expansion by the second cage.

[0020] 1. Principle of Solution of the Invention The intervertebral body internal fixation device of the present invention is characterized by having multiple elastic bodies, represented by elastic plates, which are sandwiched between rigid base structures positioned at both the left and right ends and each has a divided contact surface. Furthermore, it is preferable that the multiple elastic bodies are configured so that when the contact surfaces are aligned to the same height as the base structure, their elasticity disappears, and they support vertical loads as a rigid body integrated with the base structure.

[0021] The presence of multiple contact surfaces, each possessing its own elastic function, leads to the following phenomenon: If the vertebral endplate is partially fractured (damaged) at the contact surface bearing the greatest load (the highest contact surface in the intervertebral internal fixation device if the vertebral endplates are parallel), the elastic body including that contact surface will sink into the vertebral body and return to its natural height. At this time, the elastic body that has returned to its natural height will also bear a load in contact with the compressed cancellous bone at the site of the vertebral endplate sinking. This load is smaller than the load it was bearing before sinking, and the remaining load that it was originally bearing is distributed to the other elastic bodies that have not yet sunk. Subsequently, the compressed canyon bone fuses and hardens over a period of two weeks to three months. During this time, if other elastic bodies that have not subsided can support the remaining vertebral endplate, even if a second subsidence of the vertebral endplate occurs at a different contact surface, the elastic function will be restored between the elastic body that subsided the first time and the vertebral endplate that hardened after subsidence, thus maintaining the elastic function of the intervertebral body fixation device itself.

[0022] Thus, by having multiple individually elastic contact surfaces, the risk of the entire intervertebral body fixation device sinking into the vertebral body, which occurred with spinal cages and artificial intervertebral discs that have only one contact surface, can be reduced. In other words, the present invention is characterized by its ability to reduce the risk of premature vertebral body sinking of the entire intervertebral body fixation device by, in a sense, tolerating partial vertebral body sinking, and by utilizing the resulting biological response (bone sclerosis) to restore elastic function and prevent overall sinking. 2. Outline of Embodiments First, an outline of the representative embodiments disclosed in this application will be given. The reference numerals in parentheses in the drawings that are referenced in the outline of the representative embodiments are merely examples of components included in the concept of the components to which they are attached.

[0023] [1] Intervertebral body internal fixation device having multiple individually elastic contact surfaces (Figures 1-3, etc.) A typical embodiment disclosed in this application is an intervertebral body internal fixation device (10) inserted into the intervertebral space between an upper vertebral body and a lower vertebral body, and is configured as follows.

[0024] The intervertebral body internal fixation device comprises a base structure (3) extending in the short axis direction at both ends in the long axis direction, a support beam (4) connecting the base structures, and one or more pairs of upper and lower elastic plates (1-1, 1-2, 1-3) that are supported by the base structures or the support beams and extend in the long axis direction.

[0025] Each of the elastic plates has a contact surface (2-1, 2-2, 2-3) for contacting the endplate of the upper or lower vertebral body, and these contact surfaces are arranged to form surfaces that are generally continuous in the longitudinal direction from the base structure on the upper and lower sides, respectively.

[0026] The intervertebral body internal fixation device is such that the elastic plate can flex in both the vertical and longitudinal directions in response to a vertical load.

[0027] This makes it possible to provide an intervertebral body fixation device that can be stably held in place when implanted, even in cases where the vertebral bone constituting the intervertebral disc space is fragile due to osteoporosis or other reasons. Multiple elastic plates have contact surfaces that come into contact with the endplates of the upper and lower vertebral bodies constituting the intervertebral disc space, and each has individual elasticity against vertical loads. Therefore, even if a small fracture occurs in a part of the endplate, the spread of the fracture is limited to the part in contact with the same contact surface, and the risk of the entire intervertebral body fixation device sinking into the vertebral body is significantly reduced.

[0028] [2] Suppression of excessive deflection by contact of the ends of the elastic plates (Figure 3) In the intervertebral body internal fixation device of [1], each of the elastic plates has adjacent contact surfaces across the gap, a front end that moves in a direction that narrows the gap in response to a vertical load, and a rear end on the opposite side. When the vertical load exceeds a predetermined value, the front ends of adjacent elastic plates across the gap come into contact with each other across the gap.

[0029] This reduces the elasticity (increases the rigidity) of the elastic plate after the gap is eliminated (contact is made). The elastic plate can flex along its long axis as well as vertically, but after contact, the axial flexure is suppressed, and only vertical flexure remains. Excessive flexure of the elastic plate is suppressed, and the risk of the intervertebral body fixation device failing due to metal fatigue is significantly reduced. In addition, the increased rigidity due to the contact of the elastic plate is added to the rigidity of the base structure, and the vertical load is distributed rather than concentrated in one area, thus reducing the risk of the intervertebral body fixation device sinking into the upper and lower vertebral bodies.

[0030] [3] Folding of the elastic plate (Figures 9, 10) In the intervertebral body internal fixation device of [1], at least one pair of elastic plates are bent toward the center in the vertical direction at the end opposite to the end supported by the base structure or the support beam.

[0031] This helps to prevent excessive deflection of the elastic plate.

[0032] [4] Loop-shaped bend of the elastic plate (Figure 10) In the intervertebral body internal fixation device of [3], the bent ends of the at least one pair of elastic plates are connected to the base structure or the support beam.

[0033] This helps to prevent excessive deflection of the elastic plate.

[0034] [5] Multiple elastic plates in the direction of the short axis (Figures 1, 2, 6-10) In the intervertebral body internal fixation device of any one of items [1] to [4], the intervertebral body internal fixation device has multiple elastic plates in the direction of the short axis.

[0035] This divides the contact surface of the elastic plate into multiple areas in two dimensions, which helps to limit the extent to which a minor fracture occurs in a part of the endplate. In addition, since the vertical load is distributed in two dimensions, the risk of the intervertebral body fixation device sinking into the upper or lower vertebral bodies is further reduced.

[0036] [6] Frame consisting of a base structure and support beams on both sides (Figure 11) In the intervertebral body internal fixation device of claim 1, the base structures at both ends in the long axis direction are connected to each other by the support beams at both ends in the short axis direction, at least one pair of elastic plates are integrally formed with the base structure, and at least another pair of elastic plates are connected to and supported by the base structure.

[0037] As a result, multiple pairs of elastic plates are surrounded and stably supported by a frame formed by base structures at both the left and right ends and support beams at both the front and rear ends.

[0038] [7] Intervertebral body internal fixation device having multiple individually elastic contact surfaces A typical embodiment disclosed in this application is an intervertebral body internal fixation device (10) inserted into the intervertebral space between an upper vertebral body and a lower vertebral body, wherein the intervertebral body internal fixation device comprises a plurality of elastic members (1, 1-1, 1-2, 1-3) each having a pair of upper and lower contact surfaces for contacting the endplates of the upper and lower vertebral bodies, and the plurality of elastic members each have elasticity between the pair of upper and lower contact surfaces (2, 2-1, 2-2, 2-3).

[0039] This makes it possible to provide an intervertebral body fixation device that can be stably held in place when implanted, even in cases where the vertebral bone constituting the intervertebral disc space is fragile due to osteoporosis or other conditions.

[0040] Figure 22 is a schematic diagram illustrating the solution principle of the present invention. It is a schematic diagram of the two vertebral bodies of a patient and the intervertebral disc space between them, viewed from the anterior (ventral) side. [A] shows a state in which the intervertebral disc space has narrowed. The intervertebral internal fixation device 10 of the present invention is inserted by widening this intervertebral disc space. The intervertebral internal fixation device 10 is described as comprising a plurality of elastic members, each shaped like a U on its side. Each elastic member is, for example, a structure including a highly rigid support (base) and a plate-shaped member extending to one side from the support. The plate-shaped member acts as a leaf spring, so that each contact surface viewed from the vertical direction has individual elasticity. It is more preferable that the individual elasticity can take on independent values, as will be described later in [8]. [B] shows the unloaded state. This is a state in which no load is applied to the intervertebral internal fixation device 10 from above or below, and the plurality of elastic members maintain their maximum thickness. [C] shows the state in which a load is applied from above or below. If there is no damage to the endplate of the vertebral body, the multiple elastic members of the intervertebral body internal fixation device 10 are uniformly compressed, becoming thinner and supporting the load. Here, although it is said that the load on the multiple elastic members is not necessarily equal due to the unevenness of the endplate, it will vary. However, because the multiple elastic members each have elasticity, they absorb their respective loads (the load on each region when viewed from above). [D] shows the case in which a microfracture occurs in a part of the endplate. The elastic member in the region where the microfracture occurs cannot support the load, and the contact surface may sink into the fractured area. Note that in [D], sinking is shown both above and below the same region, but microfractures do not necessarily occur in the same region above and below. Rather, it is thought that the elastic member with a contact surface that has sunk on one side is released from the load, and sinking on the other side is less likely to occur. In this invention, since the multiple elastic members each have elasticity, even if the contact surface sinks due to a microfracture or other reason, the sinking is less likely to spread to the surrounding area.

[0041] In this explanatory diagram and the following embodiments, the direction in which the plate-shaped member extends from the support column is described as the long axis direction, but this is not the only way to go. For example, an elastic member that functions as a leaf spring may be used, with the plate-shaped member extending from the support column in the short axis direction or other directions. Furthermore, the elastic function is not limited to a leaf spring; a disc spring or any other elastic member may be used.

[0042] [8] Multiple elastic members having independent elasticity in each region In the intervertebral body internal fixation device of [7], the elasticity between the upper and lower paired contact surfaces is independent for each of the multiple elastic members. Here, independent elasticity means that the load applied to one elastic member does not cause other elastic members to expand or contract. Even if a change in the direction of expansion or contraction occurs due to the effect of strain propagated by the integration of the structure, this is excluded as an error. Specifically, unlike an active design that distributes the load applied to one elastic member to other elastic members by connecting a part of the contact surface, the connection by a support member to connect multiple elastic members and support them with the required strength does not affect the independence of the elasticity.

[0043] This allows each contact surface in multiple regions to have independent elasticity, making it possible to prevent the fracture and sinking from spreading to the surrounding regions even if a minute fracture occurs in the vertebral endplate in contact with a certain region and the elastic member in contact with it sinks.

[0044] 〔9〕变形限制构件(图12、14、17) 在〔7〕或〔8〕的椎间内固定器具中,所述多个弹性构件中的至少一部分可以进一步包括变形限制构件(5),当所述上下成对的接触面承受来自上下的载荷且所述接触面之间的距离缩小时,该变形限制构件会在所述接触面的内表面接触并增加刚性。当弹性构件的板结构在承受上下载荷而向中央挠曲时,如果无法如后所述那样与相邻弹性构件的支柱等基座接触,则通过使其与该变形限制构件接触,可以增加弹性构件的刚性,并抑制进一步的挠曲。在此,变形限制不仅指使其不再进一步挠曲的形态,还包括增加刚性以使对载荷的挠曲方式变小的形态。

[0045] 由此,可以抑制压缩到期望厚度的弹性构件的变形。当弹性构件被压缩到期望厚度以上时,周围的弹性构件也会受到压缩力,施加该力的区域的终板发生有限沉降的可能性增加,但是,即使局部发生裂纹(骨折)且仅该弹性构件的接触面沉降到椎体内,如果支撑椎体终板区域的其他弹性构件不发生骨折,则可以抑制沉降扩展到整个椎间内固定器具。通过设置变形限制构件或采用〔10〕中后述的变形限制机构,可以减轻弹性构件的板状构件因反复载荷而发生金属疲劳并折断的危险性。

[0046] 〔10〕相邻弹性构件的变形限制(图6、8、12、14、17、23) 在〔7〕、〔8〕或〔9〕的椎间内固定器具中,所述多个弹性构件沿所述长轴方向并排布置。每个所述多个弹性构件包括形成所述接触面的上下板状构件和沿上下方向延伸的支柱,所述板状构件的一端由所述支柱支撑且另一端开放,从而具有上下方向的弹性,当在所述接触面上施加上下方向的载荷时,所述另一端通过与相邻弹性构件的支柱的上下端部接触来增加所述弹性构件的刚性,并抑制进一步的挠曲。

[0047] As a result, there is provided a support structure for an elastic member that can effectively utilize the space of the intervertebral internal fixation device to achieve deformation restriction against excessive deflection.

[0048] The structure of the deformation restricting member is arbitrary. For example, as illustrated in FIGS. 6, 12, 14, and 17, the elastic members 1-1, 1-2, 1-3 can be formed in a horizontal U-shape. That is, the elastic members 1-1, 1-2, 1-3 are composed of plate-like members that form contact surfaces 2-1, 2-2, 2-3 and vertical columns that support them, and the plate-like members receive a vertical load and contact the columns of the adjacent elastic members 1-1, 1-2, 1-3, thereby increasing the rigidity. That is, the columns of the elastic members 1-1, 1-2, 1-3 function as deformation restricting members. At this time, by appropriately adjusting the height of the columns of the elastic members 1-, 1-2, 1-3, it is possible to adjust at what thickness reduction of the upper and lower pairs of each contact surface 2-1, 2-2, 2-3 the deformation is restricted. As described in "1. Solution principle of the present invention" above, a plurality of elastic bodies can be configured to lose their elasticity when the contact surfaces are aligned at the same height as the base structure and support a vertical load as a rigid body integrated with the base structure, but it is also possible to optimally design at what thickness each individual elastic member loses its elasticity. Furthermore, it is not always necessary to completely eliminate the elasticity, and it is also possible to reduce it to an appropriate magnitude, that is, to give an appropriate rigidity.

[0049] Figure 23 is a schematic diagram illustrating the mechanism of deformation limitation by adjacent elastic members. Each elastic member 1-1 to 1-4 is a structure that includes rigid support columns (which may also be called bases) 21-1 to 21-4, plate-like members 22-1u to 22-4u extending to one side from the upper end of the support columns 21-1 to 21-4, and plate-like members 22-1d to 22-4d extending to the same one side from the lower end. The upper and lower plate-like members 22-1u to 22-4u and 22-1d to 22-4d are open on sides other than those connected to the upper and lower ends of the support columns 21-1 to 21-4, and the upper and lower plate-like members 22-1u to 22-4u and 22-1d to 22-4d function as leaf springs. The upper surfaces of the upper plate-like members 22-1u to 22-4u and the lower surfaces of the lower plate-like members 22-1d to 22-4d function as a contact surface 2, and when a vertical load is applied, they exhibit elasticity by bending inward (vertically).

[0050] The elastic members 1-1 to 1-4 are arranged in a line along the long axis (left-right direction in Figure 23), and the upper and lower plate-like members 22-1u to 22-4u and 22-1d to 22-4d have their ends opposite to the ends connected to the support columns 21-1 to 21-4 widened in the vertical direction, and are positioned adjacent to the support columns of adjacent elastic members 1-1 to 1-4 so that their positions when viewed from above overlap.

[0051] For example, in Figure 23, elastic members 1-2 and 1-3 face each other across the center, and elastic members 1-1 and 1-4 are arranged on the outside of them, facing the same direction. The upper plate-shaped member 22-1u of elastic member 1-1 has its left end connected to the upper end of the support column 21-1, and its right end is open and spread outwards (upwards), so that its tip aligns with the support column 21-2 of the adjacent elastic member 1-2 when viewed from above. The lower plate-shaped member 22-1d of elastic member 1-1 has its left end connected to the lower end of the support column 21-1, and its right end is open and spread outwards (downwards), so that its tip aligns with the support column 21-2 of the adjacent elastic member 1-2 when viewed from below. A similar configuration is adopted for elastic members 1-3 and 1-4 on the opposite side of the center. In the example shown in Figure 23, since the members are arranged symmetrically with the center in between, the upper and lower plate-shaped members 22-2u and 22-2d and plate-shaped members 22-3u and 22-3d of the central elastic members 1-2 and 1-3 do not have adjacent elastic member supports on their tip side, so a separate deformation limiting member 5 is provided.

[0052] In this way, by arranging the elastic members 1 adjacent to each other such that the tip of the plate-shaped member 22 overlaps with the support column 21 of the adjacent elastic member 1, when subjected to a vertical load, the plate-shaped member 22 bends inward. Furthermore, as the load increases and the tip of the plate-shaped member 22 comes into contact with the support column 21 of the adjacent elastic member 1, the elasticity decreases or disappears, and the rigidity increases. In the example in Figure 23, [A] is the unloaded state. The plate-shaped member 22 is not bending, and the thickness T1 of the intervertebral body internal fixation device 10 is at its maximum. When a load is applied, as shown in [B], the plate-shaped member 22 of the elastic member 1 with the contact surface 2 that receives the load first begins to bend sequentially, and the load is supported by multiple surfaces. At this time, the thickness T2 of the intervertebral body internal fixation device 10 is smaller than T1 and is about the same as the distance between the upper and lower surfaces of the plate-shaped members 22 of the multiple elastic members 21. As the load increases further, as shown in [C], the plate-shaped member 22 comes into contact with the support column 21 or deformation-limiting member 5 of the adjacent elastic member 1, causing the elasticity to decrease or disappear and the rigidity to increase. The thickness T3 of the intervertebral body internal fixation device 10 is even smaller than T1 and T2. If the support column 21 and the deformation-limiting member 5 are made of rigid bodies, elasticity is lost and rigidity increases after contact, but if they are made of elastic bodies, the elasticity of the elastic member 1 is not lost at all, but only decreases.

[0053] The vertical thickness of the multiple elastic members 1 can also be optimized to match the intervertebral disc space of the patient. If the vertical distance of the intervertebral disc space is greatest in the center, the elastic member 1 located in the center of the intervertebral body fixation device can be shaped to have the greatest vertical thickness, thereby making the stress on the contact surface 2 of each elastic member 1 uniform. If the vertebral endplates of the upper and lower vertebrae in contact are parallel, the load will first be applied to the elastic member 1 with the greatest vertical thickness, and the plate-shaped member 22 will bend until it contacts the support 21 or deformation limiting member 5 of the adjacent elastic member 1. However, because the plate-shaped members 22 constituting each elastic member 1 are inclined, the load will begin to be applied to the contact surface 2 of another elastic member 1 before the rigidity of the elastic member 1 located on the central side increases, making it possible for the load from the vertebral endplates of the upper and lower vertebrae to be distributed and received by the multiple elastic members 1. Figure 23 shows an example where one end of the plate-like members 22-1u to 22-4u and 22-1d to 22-4d is connected to the upper and lower ends of the support columns 1-1 to 21-4. However, the connection points of the plate-like members to the support columns are not limited to the upper and lower ends of the support columns. Furthermore, there may be no clear distinction between the plate-like members and the support columns, and they may be composed of a single, integrated member that curves with a continuous curvature.

[0054]

[11] Support structure for elastic member (Figures 12, 14, 17) In [7], [8], [9] or

[10] , the intervertebral body internal fixation device further comprises a base structure (3) extending in the short axis direction at both ends in the long axis direction and a support beam (4) connecting the base structure.

[0055] The plurality of elastic members are supported by the base structure or the support beam and arranged in the longitudinal direction, and the contact surfaces are arranged to form surfaces that are substantially continuous with the base structure in the longitudinal direction on the upper and lower sides, respectively.

[0056] As a result, multiple pairs of elastic members are supported in an H-shape by the base structures at both the left and right ends and the support beams along the long axis, thereby stabilizing the multiple elastic members.

[0057]

[12] Second cage (Figures 13-21, 24) In the intervertebral body internal fixation device of

[11] , the support beam is referred to as the first support member and the elastic member as the first elastic member, and the intervertebral body internal fixation device further comprises one or more second elastic members (12, 12-1, 12-2, 12-3) supported by the second support member (6-2).

[0058] The intervertebral body internal fixation device is configured to be able to take two states: one in which one or more second elastic members are housed in the gaps between the plurality of first elastic members, and another in which, when viewed from above, the second elastic member protrudes from the first elastic members in one direction in the short axis direction.

[0059] This allows the elastic member to protrude forward (ventrally) or backward (dorsally) after the intervertebral body fixation device has been inserted into the patient's intervertebral disc space, thereby expanding the area on which the intervertebral body fixation device can contact the endplate. This further distributes the load from the endplates of the upper and lower vertebrae, reducing the risk of the entire intervertebral body fixation device sinking into the spine.

[0060] Figure 24 is a schematic diagram illustrating the principle of contact surface expansion by the second cage (second elastic member and its support member). It shows the intervertebral stabilization device 10 embedded in the intervertebral disc space between the two upper and lower vertebral bodies on the left side of the patient. The left side of the drawing is the anterior, ventral side of the patient, and the right side of the drawing is the posterior, dorsal side of the patient. [A] shows the patient in an upright position, and [B] shows the patient flexed forward, with the ventral side of the intervertebral disc space narrowed. The illustrated intervertebral stabilization device 10 is configured so that the second elastic member 12 can expand ventrally, and Figure 24 shows the expanded state. The second elastic member 12 has a support column 21 and a plate-like member 22 that extends from the support column 21 to one side (anterior, ventral). As a result, when the lumbar spine is flexed forward, as shown in [B], the load is mainly applied to the second elastic member 12, and the plate-like member 22 flexes, distributing and receiving the load. Furthermore, although not shown in Figure 24, if multiple second elastic members 12 are arranged in a row, the risk of intravertebral sinking can be further reduced as these multiple second elastic members 12 flex individually. Compared to when the load is received by the first elastic member 1 alone, the contact surface 2 is expanded by the second elastic members 12, allowing the load to be received by a wider area and more elastic members, thus greatly reducing the risk of the entire intervertebral fixation device 10 sinking into the vertebral body. In particular, since a large load is placed on the ventral side during flexion, providing the second elastic members 12 to expand to the ventral side and receive that load is extremely effective in reducing the risk of the entire intervertebral fixation device 10 sinking into the vertebral body.

[0061] Excessive deflection of the plate-shaped member 22 of the second elastic member 12 may be mitigated by reducing or eliminating the elasticity of the second elastic member 12 and increasing its rigidity, as shown in [C], by placing the deformation limiting member 5 at a position that overlaps with the tip of the plate-shaped member 22 of the second elastic member 12 when viewed from above.

[0062] Figure 24 shows an example in which the second cage (second elastic member 12 and its support member) is extended anteriorly, towards the ventral side of the patient, but it may also be configured to be extendable posteriorly. By providing the second cage, the load applied to the intervertebral internal fixation device 10 during movement of the upper and lower vertebrae in lumbar flexion and extension positions can be distributed and received by the second cage as well.

[0063]

[13] Transition to an expanded state by a control rod (Figure 15) In the intervertebral body internal fixation device of

[12] , the intervertebral body internal fixation device further comprises a control rod (8), and the support beam comprises a hollow portion in the longitudinal direction and a control window (7) in the short direction.

[0064] The second support member is inserted into the hollow portion through the control window and supported, and can slide in the short axis direction. The control rod is inserted into the hollow portion from the long axis direction and pushes the second support member in the short axis direction, thereby transitioning the second elastic member from the housed state to the protruding state.

[0065] This enhances safety during surgery to implant the intervertebral body fixation device of the present invention into the patient's intervertebral disc space. Specifically, by inserting the device into the patient's intervertebral disc space with the second elastic member (second cage) housed in the main body, and then pushing the control rod (8) deeply, the second elastic member (12) can be pushed out and transitioned to an expanded state. This reduces the risk of the second elastic member, etc., damaging the surrounding tissues of the intervertebral disc space compared to inserting it in an expanded state.

[0066]

[14] Third cage (Figures 16-21) In the intervertebral body internal fixation device of

[12] , the intervertebral body internal fixation device further comprises one or more third elastic members (13-1, 13-2, 13-3) supported by a third support member (6-3), wherein in the housing state, the one or more third elastic members are housed in the gaps between the plurality of first elastic members, and in the protruding state, when viewed from above, the third elastic member protrudes from the first elastic member in the other direction in the short axis direction.

[0067] This allows the elastic members to protrude not only to one side but also to the other (not only the second cage protruding forward but also the third cage protruding backward) after the intervertebral body internal fixation device has been inserted into the patient's intervertebral disc space, further expanding the area on which the intervertebral body internal fixation device can contact the endplate. In the same principle as explained above with reference to Figure 24 in

[12] , the risk of spinal subsidence of the entire intervertebral body fixation device can be reduced, and the load can be distributed not only when the patient flexes forward but also when they flex backward.

[0068]

[15] Transition to an expanded state by a control rod (Figure 20) In the intervertebral body internal fixation device of

[14] , the intervertebral body internal fixation device further comprises a control rod (8). The support beam comprises a hollow portion in the longitudinal direction, one first control window (7) in the short direction, and the other second control window (7) in the short direction. The second support member is inserted into the hollow portion from the first control window and supported, and can slide in the short direction. The third support member is inserted into the hollow portion from the second control window and supported, and can slide in the short direction.

[0069] The control rod is inserted into the hollow portion from the long axis direction, pushing the second support member in the short axis direction and the third support member in the other direction in the short axis direction, thereby transitioning the second and third elastic members from the housed state to the protruding state.

[0070] This enhances safety during surgery to implant the intervertebral body fixation device of the present invention into the patient's intervertebral disc space. Specifically, by inserting the device into the patient's intervertebral disc space with both the second elastic member (second cage) and the third elastic member (third cage) housed in the main body, and then pushing the control rod (8) deeply, both the second elastic member (12) and the third elastic member (13) can be pushed out and transitioned to an expanded state. This reduces the risk of the second and third elastic members damaging the surrounding tissues of the intervertebral disc space compared to inserting the device in an expanded state.

[0071] 3. Details of the Embodiments The embodiments will be described in more detail below.

[0072] [Embodiment 1] Figure 1 is an explanatory diagram showing one example of the configuration of the intervertebral body internal fixation device 10 of Embodiment 1, with a top view in the upper section, an XX cross-section in the middle section, and a YY cross-section in the lower section. Figure 2 is a perspective view. The intervertebral body internal fixation device 10 comprises a base structure 3 extending in the short axis direction from both ends in the long axis direction, a support beam 4 connecting the base structures 3 at both ends, and three pairs of elastic plates 1-1, 1-2, and 1-3 extending in the long axis direction from each of the base structures 3 at both ends toward the center, further arranged in left-right pairs. That is, the three pairs of elastic plates 1-1, 1-2, and 1-3 are provided in left-right pairs in two rows at both ends of the base structure 3 in the short axis direction.

[0073] Each of the elastic plates 1-1, 1-2, and 1-3 has a contact surface 2-1, 2-2, and 2-3 on its central side for contacting the endplate of the upper or lower vertebral body, and these contact surfaces 2-1, 2-2, and 2-3 are arranged to form a generally continuous surface with a gap in the longitudinal direction on the upper and lower sides, respectively. The elastic plates 1-1, 1-2, and 1-3 are configured to bend both vertically and along their longitudinal axis toward the center in response to loads applied to the intervertebral body internal fixation device 10 from above and below.

[0074] Here, the intervertebral body internal fixation device 10 is inserted into the intervertebral space between the upper and lower vertebral bodies, assuming the patient is in an upright position. Typically, one device is embedded in each intervertebral space so that its long axis is in the left-right direction of the patient. Accordingly, in this specification, the long axis direction of the intervertebral body internal fixation device 10 may be referred to as the left-right direction, and the short axis direction as the anterior-posterior direction. Furthermore, regarding the contact surfaces, "continuous" means that when adjacent contact surfaces in the long axis direction are smoothly connected, the inclination in the long axis direction does not change abruptly but remains constant or changes gradually. "Generally continuous" means that it is permissible to include a minute step or a minute steep area in part of that inclination. This is common throughout this specification.

[0075] This makes it possible to provide an intervertebral body internal fixation device 10 that can be stably held in place when implanted, even in cases where the vertebral bone constituting the intervertebral disc space is fragile due to osteoporosis or the like. Multiple elastic plates 1-1, 1-2, 1-3 have contact surfaces 2-1, 2-2, 2-3 in contact with the endplates of the upper and lower vertebral bodies constituting the intervertebral disc space, and each has individual elasticity against vertical loads. Therefore, even if a small fracture occurs in a part of the endplate, the expansion of the fracture is limited to the part in contact with the same contact surface, and the risk of the entire intervertebral body internal fixation device 10 sinking into the vertebral body is significantly reduced. In this embodiment 1, 12 contact surfaces 2-1, 2-2, 2-3, divided into two rows of six plates each, are in contact with the upper and lower endplates. In other words, there are 12 pairs of elastic bodies, one above the other, which individually flex and absorb the load in the vertical direction. If a minute fracture occurs at one of the twelve contact surfaces 2-1, 2-2, or 2-3 of the upper and lower endplates that are in contact, the force applied to the endplate as a reaction from the contact surface to the vertical load may cause the fracture to spread to the surrounding area. However, it is expected that the spread of the fracture will be limited to that contact surface, and that the contact surface will only sink into the vertebral body. This is because the surrounding endplates are supported by the other eleven contact surfaces, so it is expected that the minute fracture that occurred will not spread further to the surrounding area.

[0076] As described above, the intervertebral body internal fixation device 10 of the present invention is capable of reducing and distributing the stress on the vertebral endplates that come into contact with the contact surfaces 2-1, 2-2, and 2-3, thereby reducing the risk of the entire device sinking into the vertebral body.

[0077] [Suppression of excessive deflection by contact of the ends of the elastic plates] As described above with reference to Figure 1, the elastic plates 1-1, 1-2, and 1-3 each have contact surfaces 2-1, 2-2, and 2-3 on their central side for contacting the endplate of the upper or lower vertebral body, and these contact surfaces 2-1, 2-2, and 2-3 are arranged to form generally continuous surfaces with a gap in the longitudinal direction on the upper and lower sides, respectively. A more specific example of generally continuous surfaces is shown below.

[0078] As shown in the cross-section of Figure 1, the intervertebral body internal fixation device 10 of this embodiment has a length L and a thickness H2, and the thickness of the base structure 3 is H1. The lengths of the contact surfaces 2-1, 2-2, 2-3 and the upper and lower surfaces of the base structure 3 are L1, L2, L3, and L4, respectively. There is a gap of size S1 between the contact surfaces 2-1 of the left and right elastic plates 1-1 located in the center of the intervertebral body internal fixation device 10, a gap of size S2 between the contact surface 2-2 of the outer elastic plate 1-2 and the contact surface 2-2 of the elastic plate 1-3, and further outside, a gap of size S3 between the contact surface 2-2 of the elastic plate 1-2 and the contact surface 2-3 of the elastic plate 1-3, and a gap of size S4 between the contact surface 2-3 of the elastic plate 1-3 and the upper and lower surfaces of the base structure 3. The vertical distance between the contact surfaces 2-1 of the left and right elastic plates 1-1 located in the center of the intervertebral body internal fixation device 10 is equal to the thickness H2 of the intervertebral body internal fixation device 10. As you move away from the center, the vertical distance between the contact surfaces 2-3, 2-3 gradually decreases toward the thickness H1 of the base structure 3 (the thickness of the intervertebral body internal fixation device 10 gradually decreases).

[0079] The upper and lower elastic plates 1-1, 1-2, and 1-3 are each supported diagonally from the center in the thickness direction of the base structure 3 toward the center of the intervertebral body internal fixation device 10. Therefore, in response to loads applied from above and below, they can flex both vertically and along their long axis toward the center. The elastic plates 1-1, 1-2, and 1-3 are directly or indirectly connected to and supported by the base structure 3, and they intersect vertically and extend toward the center. The length from the point of support increases in the order of elastic plates 1-1, 1-2, and 1-3, and their thickness increases in that order as well. Elastic plate 1-1, being the longest, acts in the direction of greatest elasticity, but its elasticity can be reduced by increasing its thickness.

[0080] Figure 3 is an explanatory diagram illustrating the operating principle of the elasticity loss of the intervertebral body internal fixation device 10 of the present invention. The top row is a cross-sectional view when there is no load (a), the middle row is a cross-sectional view when there is an intermediate load (b), and the bottom row is a cross-sectional view when there is a maximum load (c). In the intervertebral body internal fixation device 10, each of the elastic plates 1-1, 1-2, and 1-3 has a central front end and an opposite rear end on adjacent contact surfaces 2-1, 2-2, and 2-3 separated by gaps S1, S2, and S3. When an upward load is applied to adjacent elastic plates 1-1 separated by the central gap S1, they bend towards the center, and the left and right contact surfaces 2-1 come into contact in the center, eliminating the gap S1. When further load is applied, elastic plate 1-1 does not deflect in the central direction but only in the vertical direction, while elastic plate 1-2 deflects in both the vertical and central directions. Eventually, as shown in (b), the front end of the contact surface 2-2 of elastic plate 1-2 comes into contact with the rear end of the contact surface 2-1 of elastic plate 1-1 (the gap S2 disappears). When the load applied in the vertical direction becomes even larger, since elastic plates 1-1 and 1-2 are already in contact, deflection in the central direction is suppressed, and deflection occurs only in the thickness direction. Eventually, as shown in (c), the front end of the contact surface 2-3 of elastic plate 1-3 comes into contact with the rear end of the contact surface 2-2 of elastic plate 1-2 (the gap S3 disappears). Even if a load greater than this is applied, if the base structure 3 is not elastic, deflection in the thickness direction is suppressed, excessive deflection of elastic plates 1-1, 1-2, and 1-3 is prevented, and the risk of the intervertebral body internal fixation device 10 breaking due to metal fatigue is significantly reduced. In other words, in the intervertebral body internal fixation device 10 of the present invention, when a certain load is applied, the contact surfaces come into contact, reducing their elasticity, which reduces the risk of the contact surfaces being destroyed by the load and makes it less likely for the metal to deform. Furthermore, the intervertebral body internal fixation device 10 not only has a rigid base structure 3, but the rigidity of the part that contacts the central part of the vertebra is also increased, so the vertical load can be distributed and absorbed two-dimensionally, and the risk of the entire device sinking into the vertebra can be suppressed and reduced.

[0081] The above explanation was based on the simplified assumption that the endplates of the upper and lower vertebral bodies are parallel and that the load is applied in the vertical direction perpendicular to them. However, since the contact surfaces are arranged two-dimensionally in the front-to-back and left-to-right directions, the function of absorbing load and preventing excessive deflection under loads above a certain level is the same even for localized loads caused by the patient's forward and backward bending or tilting of the posture to the left or right.

[0082] Furthermore, depending on the condition of the affected area (for example, a situation where the vertebral body has degenerated and the intervertebral disc space has narrowed), the size and thickness of each contact surface, and the height of each contact surface may be adjusted.

[0083] [Multiple Elastic Plates in the Short-Axis Direction] The intervertebral body internal fixation device 10 of this embodiment 1, illustrated in Figures 1 and 2, is provided with six pairs of elastic plates 1-1, 1-2, and 1-3 in the vertical and horizontal directions, and two sets in the anterior-posterior direction in the short-axis direction. In the intervertebral body internal fixation device 10 of the present invention, multiple pairs of elastic plates (upper and lower and left and right pairs) may also be provided in the short-axis direction (anterior-posterior direction), and the contact surfaces of each may be arranged to form a generally continuous surface with a gap in between on the upper and lower sides in the short-axis direction.

[0084] This divides the contact surface of the elastic plate into multiple sections, spreading out two-dimensionally. Furthermore, since each elastic plate supporting each contact surface has its own individual elasticity, each contact surface can absorb the load individually. Therefore, even if a small fracture occurs in a part of the endplate, the area over which it spreads can be limited.

[0085] [Support beam] The intervertebral body internal fixation device 10 of the present invention may have a support beam 4 connecting the base structures 3 at both ends in the longitudinal direction, as illustrated in Figures 1 and 2. The support beam 4 may be hollow or not, as shown in the figures. This strengthens the overall rigidity of the intervertebral body internal fixation device 10 and reduces the risk of damage due to aging or impact.

[0086] In this first embodiment, the elastic plates 1-1, 1-2, and 1-3 are shown as being composed of a flat plate and a sharply bent portion, but they may also be smoothly bent. Furthermore, although the elastic plates 1-1, 1-2, and 1-3 intersect near the center in the vertical direction, they may also be attached to the support beam 4 or the base structure 3, as in embodiments 3 and 4 described later.

[0087] Not limited to this first embodiment, the intervertebral body internal fixation device 10 of the present invention, including other embodiments 2 to 4, can be manufactured, for example, from titanium or a titanium alloy using a metal 3D printer.

[0088] [Embodiment 2] Figure 4 is an explanatory diagram showing an example of the configuration of an intervertebral body internal fixation device 10 according to a second embodiment of the present invention. Similar to Figure 1, Figure 4 shows a top view in the upper section, an XX cross-section in the middle section, and a YY cross-section in the lower section. The intervertebral body internal fixation device 10 of this second embodiment is equipped with two support beams 4 that connect the left and right elastic plates 1-1, in addition to the support beams 4 that connect the base structures 3 at both ends in the longitudinal direction. This further strengthens the overall rigidity of the intervertebral body internal fixation device 10 and reduces the risk of damage due to aging deterioration or impact. Other configurations and functions are the same as those of the intervertebral body internal fixation device 10 of Embodiment 1, so their description is omitted.

[0089] [Embodiment 3] Figure 5 is an explanatory diagram showing an example of the configuration of an intervertebral body internal fixation device 10 according to the third embodiment of the present invention. Figure 5 corresponds to the XX cross-section of Figure 1 and is an enlarged view from the left end to the center. Similar to Embodiment 2 shown in Figure 4, the intervertebral body internal fixation device 10 of this embodiment 4 is equipped with a support beam 4 that connects the left and right base structures 3, and the elastic plates 1-1, 1-2, and 1-3 are each connected to the support beam 4.

[0090] [Embodiment 4] Figure 6 is an explanatory diagram showing an example of the configuration of an intervertebral body internal fixation device 10 according to the fourth embodiment of the present invention. Similar to Figure 1, Figure 6 shows a top view in the upper section, an XX cross-section in the middle section, and a YY cross-section in the lower section. In this fourth embodiment of the intervertebral body internal fixation device 10, a support beam 4 connecting the base structures 3 at both ends in the long axis direction is positioned in the central part in the short axis direction, and the left and right elastic plates 1-1, 1-2, and 1-3 are supported so as to protrude from the support beam 4. Other configurations and functions are the same as those of the intervertebral body internal fixation device 10 of Embodiment 1, so their description is omitted.

[0091] This simplifies the structure of the intervertebral body internal fixation device 10, reducing the risk of damage due to aging or impact.

[0092] [Embodiment 5] Figure 7 is an explanatory diagram showing an example of the configuration of an intervertebral body internal fixation device 10 according to the fifth embodiment of the present invention. Similar to Figure 1, Figure 7 shows a top view in the upper section, an XX cross-section in the middle section, and a YY cross-section in the lower section. In the intervertebral body internal fixation device 10 of this embodiment 6, the sizes of the elastic plates 1-1, 1-2, and 1-3 are asymmetrical on the left and right sides, and the gap that disappears due to vertical load is offset from the center. Other configurations and functions are the same as those of the intervertebral body internal fixation device 10 of embodiment 1, so their description is omitted.

[0093] In this way, the position of the gap that disappears due to vertical load, that is, the position where the elastic plates 1-1 face each other, can be adjusted as appropriate. In Figure 7, the number of elastic plates is 3 pairs on both the left and right sides × 2 pairs in the front and back, but the number may also be asymmetrical. This allows for the adoption of a structure suitable for the condition of the patient's vertebral body.

[0094] [Embodiment 6] Figure 8 is an explanatory diagram showing an example of the configuration of an intervertebral body internal fixation device 10 according to the sixth embodiment of the present invention. Similar to Figure 1, Figure 8 shows a top view in the upper section, an XX cross-section in the middle section, and a YY cross-section in the lower section. In the intervertebral body internal fixation device 10 of this embodiment 6, the most central elastic plate 1-1 is supported in a direction extending from the center toward the base structure 3 and is positioned facing the elastic plate 1-2. The elastic plate 1-3 is positioned on the outer side of the elastic plate 1-2 toward the base structure 3. Other configurations and functions are the same as those of the intervertebral body internal fixation device 10 of embodiment 1, so their description is omitted.

[0095] To describe the characteristic structure of this embodiment in other words, the elastic plate is provided not in one location in the left-right direction, but in two locations, and if the front-back direction is included, in four locations. At these four locations, the gap decreases in response to the vertical load, and after the gap disappears due to a load above a certain level, the elasticity decreases rapidly. As a result, the number of locations that exhibit rigidity in accordance with the base structure 3 can be increased by four, and the vertical load can be distributed and supported. Figure 8 shows an example in which a gap is left between the central elastic plates 1-1, but the central portions of the central elastic plates 1-1 may be brought into contact to eliminate the gap, or they may even be integrated.

[0096] In this embodiment 6, elastic plates are positioned facing each other at two locations on the left and right sides, and two locations at the front and back. However, the placement and number of plates are arbitrary, including making them asymmetrical on the left and right sides and / or front and back. This allows for the adoption of a structure suitable for the condition of the patient's vertebral bodies.

[0097] [Embodiment 7] Figures 9 and 10 are explanatory diagrams showing an example of the configuration of an intervertebral body internal fixation device 10 according to the seventh embodiment of the present invention. Figures 9 and 10 show a top view in the upper section and a side view in the lower section, respectively. The side view has a viewpoint in the front direction and is not a cross-section, but hatching is applied to facilitate understanding. The intervertebral body internal fixation device 10 of this embodiment 7 is characterized in that the central elastic plate 1-1 is bent toward the center in the vertical direction on the side opposite to the side that is connected to and supported by the base structure 3.

[0098] In the example shown in Figure 9, the beam is further bent along the support beam 4 towards the base structure 3, with the end open. In the example shown in Figure 10, the beam is also further bent along the support beam 4 towards the base structure 3, but the end is connected to the support beam 4.

[0099] In this way, the elasticity of the intervertebral body internal fixation device 10 near the center can be adjusted by folding back the side of the central elastic plate 1-1 that is not connected to and supported by the base structure 3. Since the length of the central elastic plate 1-1 from the supported base structure 3 is longer than that of the other elastic plates 1-2 and 1-3, its elasticity against vertical loads tends to be greater than that of the other elastic plates 1-2 and 1-3. The elasticity can be reduced by bending it to follow the support beam 4 or by connecting it to the support beam 4.

[0100] Furthermore, in the intervertebral body internal fixation device 10 shown in Figure 9, the folded portion of the contact surface 2-1 of the elastic plate 1-1 comes into contact with the support beam 4 when the contact surface 2-1 is deeply pressed in, so the elasticity is lost or significantly reduced when subjected to a load above a certain level in the vertical direction. In the intervertebral body internal fixation device 10 shown in Figure 10, the elasticity is adjusted by the fact that the elastic plate 1-1 is folded in to form a loop, and when the contact surface 2-1 is sandwiched between the contact surface 2-1 and the support beam 4, the elasticity is lost or significantly reduced when subjected to a load above a certain level in the vertical direction when the contact surface 2-1 is deeply pressed in.

[0101] In both Figure 9 and Figure 10, if the position of the contact surface 2-1 is aligned with the thickness of the base structure 3 in the thickness direction, the entire intervertebral body internal fixation device 10 will have rigidity, and the contact surfaces 2-1 to 2-3 will form a surface that is generally continuous with the base structure 3 in the longitudinal direction, allowing the vertical load to be distributed evenly across the entire surface.

[0102] Furthermore, in both Figure 9 and Figure 10, the intervertebral body internal fixation device 10 is bent at a right angle toward the support beam 4 in the center, and further bent toward the supporting base structure 3. However, it is also acceptable to bend it only at a right angle toward the support beam 4 in the center. The bent portion can be configured to lose its vertical elasticity when it comes into contact with the support beam 4. In this case, the length of the bend should be adjusted so that the contact surface 2-1 aligns with the base structure 3 when the tip comes into contact with the support beam 4 and loses its elasticity. Moreover, instead of bending the elastic plate 1-1, another component may be attached. In addition, although this embodiment describes a mechanism in which elasticity is lost by contact with the support beam 4, the elasticity may also be lost when the bent portions of the upper and lower elastic plates 1-1 or the components attached in their place come into contact with each other vertically.

[0103] [Embodiment 8] Figure 11 is an explanatory diagram showing an example of the configuration of an intervertebral body internal fixation device 10 according to the eighth embodiment of the present invention. In Figure 11, the top view is shown in the upper section and the side view is shown in the lower section. In the intervertebral body internal fixation device 10, the base structures 3 at both ends (left and right) in the long axis direction are connected to each other at both ends in the short axis direction by support beams 4. The support beams 4 are in the shape of an infinity symbol when viewed from the side and are integrated with the base structures 3 to form a frame. The elastic plates 1-2 are integrally formed with the left and right base structures 3, and the elastic plate 1-1 is connected to and supported by the base structures 3, crossing in the middle and extending towards the center. The contact surfaces 2-1, 2-1 have anti-slip irregularities formed on them.

[0104] As a result, multiple pairs of elastic plates 1-1 and 1-2 are surrounded and stably supported by a frame formed by the base structure 3 at both the left and right ends and the support beams 4 at both the front and rear ends. Although the support beams 4 are shown as an example in the shape of an infinity symbol (∞), their shape can be arbitrary, such as a rod or plate, as long as it does not interfere with the deformation of the elastic plates 1-1 and 1-2. The support beams 4 at both the front and rear ends may be connected near the center by another beam. This beam may be two rods parallel to the short axes or an X shape intersecting in the center. This helps to suppress deformation of the frame, such as distortion or twisting, which is formed integrally with the base structure 3.

[0105] [Embodiment 9] Figure 12 is an explanatory diagram showing one example of the configuration of the intervertebral body internal fixation device 10 according to this embodiment 9. Similar to Figure 1, Figure 12 shows a top view in the upper section, an XX cross-section in the middle section, and a YY cross-section in the lower section.

[0106] In this embodiment 9, the intervertebral body internal fixation device 10 has a support beam 4 connecting the base structures 3 at both ends in the long axis direction, positioned in the central part in the short axis direction, and the front, rear, and central elastic plates 1-1, 1-2, and 1-3 constituting the first elastic member 1 are supported so as to protrude from the support beam 4 in pairs vertically. Note that the elastic plates 1-1, 1-2, and 1-3 function as leaf springs, and in consideration of their functional aspect, they may be given the same reference numerals and referred to as elastic members 1-1, 1-2, and 1-3. The support beam 4 only needs to be able to connect the base structures 3 to form a basic structure and support the elastic plates 1-1, 1-2, and 1-3, and its shape can be arbitrary, such as a cylindrical shape or a rectangular prism whether it is hollow or not, and it may also be called a support member. The support beam 4 is preferably hollow in the long axis direction. When inserting the intervertebral body internal fixation device 10 into the patient's intervertebral disc cavity, a guide pin is first placed in the intervertebral disc cavity, and while inserting the guide pin into the hollow structure, the intervertebral body internal fixation device 10 can be easily inserted into the optimal position by sliding it in over the guide pin. Furthermore, the support beam 4 connecting the base structures 3 at both ends in the long axis direction is not necessarily in the central part in the short axis direction, but can be located anteriorly or posteriorly, and its location is arbitrary.

[0107] Unlike the intervertebral body internal fixation devices 10 of Embodiments 1 and 4, this device includes elastic members 1-1, 1-2, and 1-3 arranged along the long axis in the center of the short axis. The elastic members 1-1, 1-2, and 1-3 each have contact surfaces 2-1, 2-2, and 2-3 on the centerline (W-W) side for contacting the endplates of the upper and lower vertebral bodies, respectively, in the anterior-posterior (upper and lower in the top view) and central directions. These contact surfaces 2-1, 2-2, and 2-3 are arranged to form generally continuous surfaces with a gap in between in the long axis direction on the upper and lower sides, similar to Embodiments 1 and 4, and further arranged to form generally continuous surfaces with a gap in between in the short axis direction. Here, "continuous in the short axis direction" means not only the continuity in the long axis direction mentioned above, but also that when adjacent contact surfaces in the short axis direction are smoothly connected, the slope in the short axis direction changes constant or gradually without becoming abrupt. "Generally continuous" means that it is permissible to include minute steps or steep minute regions in part of that slope.

[0108] Each elastic member 1-1, 1-2, and 1-3, as explained with reference to Figure 23, has a U-shape on its side and is a structure that includes a rigid support column and a plate-like member extending from the support column to one side. The plate-like member functions as a leaf spring, and the plate-like member extending to one side functions as a contact surface 2. The plate-like members extending from each support column and forming the contact surfaces 2-1, 2-2, and 2-3 are preferably inclined in the longitudinal direction, and configured so that the support column of the adjacent elastic member is located directly below or directly above the tip of the plate-like member. As a result, when the upper and lower pair of plate-like contact surfaces 2-1, 2-2, and 2-3 are subjected to loads from the upper and lower vertebrae, the plate-like members forming the contact surfaces 2-1, 2-2, and 2-3 deflect in the vertical and longitudinal directions, and further deflection is suppressed by contacting the support columns of the adjacent elastic members 1-1, 1-2, and 1-3. The vertical thickness of the multiple elastic members 1-1, 1-2, and 1-3 can be adjusted to match the structure of the patient's intervertebral disc cavity. For example, if the vertical distance of the intervertebral disc cavity is greatest in the center, the elastic member 1 located in the center of the intervertebral body fixation device 10 can be made to have the greatest vertical thickness, thereby making the load on the contact surface 2 of each elastic member 1 uniform. If the vertebral endplates of the upper and lower vertebrae in contact were parallel, the load would first be applied to the elastic member 1 with the greatest vertical thickness and compressed until deformation was limited. However, because the plate-like members constituting each elastic member 1 are inclined, the load begins to be applied to the contact surface 2 of the other elastic members 1 before deformation is limited to the elastic member 1 located in the center, making it possible for the load from the vertebral endplates of the upper and lower vertebrae to be distributed and received by the multiple elastic members 1. The multiple elastic members 1 are structured to sink individually into the vertebral body, and even if a few contact surfaces 2 sink into the vertebral body, the risk of the entire intervertebral body internal fixation device 10 sinking into the vertebral body is reduced as long as the remaining vertebral endplates do not fracture.

[0109] The intervertebral body internal fixation device 10 of this embodiment 9 further includes a deformation limiting member 5 in the center, straddling the centerline (W-W). When the plate-shaped member of the elastic member 1-1 is subjected to a vertical load and bends towards the center, it cannot contact the support column of the adjacent elastic member 1. Therefore, by making it contact this deformation limiting member 5 instead, further bending of the elastic member 1-1 can be suppressed. More specifically, when the elastic member 1-1 is subjected to a vertical load and bends, the inner side of the elastic member 1-1 (the side opposite to the contact surface 2-1) contacts the deformation limiting member 5. By making contact, the rigidity of the elastic plate 1-1 in the vertical direction increases, and the gap between the contact surfaces 2-1 (the thickness of the elastic member 1-1) becomes less likely to decrease further. The deformation limiting member 5 can be either a rigid or elastic structure, and is adjusted to increase its rigidity in response to an appropriate load. If the deformation limiting member 5 is a rigid body without elasticity, then after contact, it loses its elasticity, and the gap between the contact surfaces 2-1 (the thickness of the elastic member 1-1) will not decrease any further.

[0110] Other configurations and functions are the same as those of the intervertebral body internal fixation device 10 in Embodiment 1, so their description is omitted. The elastic members 1-1, 1-2, and 1-3 are plate-shaped members similar to those in Embodiment 1, and may be called elastic plates 1-1, 1-2, and 1-3, but may be changed to other elastic bodies such as disc springs.

[0111] This simplifies the structure of the intervertebral body internal fixation device 10, reducing the risk of damage due to metal fatigue from repeated loading, aging deterioration, impact, etc. It is simpler and more stable than the deformation limiting mechanism described in Embodiment 1.

[0112] [Embodiment 10] Figure 13 is an image diagram showing a perspective view of one example of the configuration of the intervertebral body internal fixation device 10 according to this embodiment 10. The intervertebral body internal fixation device 10 has a configuration mainly consisting of elastic members 1-1, 1-2, and 1-3, similar to the embodiment 9 described above, and also includes a second elastic member 12 supported by a support member 6-2. The second elastic member 12 is configured to be able to take on a housed state in which it is housed in the gap between the elastic members 1-1, 1-2, and 1-3, and a protruding state in which it extends forward (ventrally) from the elastic members 1-1, 1-2, and 1-3 when viewed from above. In Figure 13, the protruding state is shown on the upper side and the housed state on the lower side. This allows the second elastic member 12 to be extended forward (ventrally) from the elastic members 1 after the intervertebral body internal fixation device 10 has been inserted between the patient's vertebrae. If medically necessary, it can also be used to protrude backward (dorsally) structurally. This allows the elastic member to protrude forward (ventrally) or backward (dorsally) after the intervertebral body fixation device 10 is inserted into the patient's intervertebral disc space, thereby expanding the area on which the intervertebral body fixation device 10 can contact the endplate. As a result, the load from the endplates of the upper and lower vertebrae can be distributed, reducing the risk of the entire intervertebral body fixation device 10 sinking into the spine.

[0113] The configuration of the second elastic member 12 is arbitrary, but it is preferable to configure it to include a support column and a plate-like spring-like member extending from the support column to one side, similar to the first elastic member 1 described with reference to Figure 23. This allows the load to be distributed to the second elastic member 12 in addition to the first elastic member 1 when the lumbar spine is flexed or extended. The second elastic member 12 is composed of multiple members as shown in Figure 13, and when a load is applied, the risk of spinal recession can be reduced by allowing not only the first elastic member 1 but also the multiple second elastic members 12 to bend individually. By providing the second elastic member 12 and making it protruding, the load applied to the intervertebral internal fixation device 10 during movement of the upper and lower vertebrae in lumbar flexion and extension positions can be mainly received by the second elastic member 12. As described above with reference to Figure 24, the contact surface 2 is expanded by the second elastic member 12 compared to when the load is received by the first elastic member 1 alone. This allows the load to be received by a wider area and more elastic members, significantly reducing the risk of the entire intervertebral body fixation device 10 sinking into the vertebral body. In particular, a large load is placed on the ventral side during flexion, so providing the second elastic member 12 to expand to the ventral side and receive that load is extremely effective in reducing the risk of the entire intervertebral body fixation device 10 sinking into the vertebral body.

[0114] Figure 14 is an explanatory diagram showing an example of the configuration of the main body portion of the intervertebral body internal fixation device 10 according to this embodiment 10. The top row shows a top view, the second row shows an X-X cross-section, the third row shows a front view, and the fourth row shows a Z-Z cross-section.

[0115] As shown in the front view, the intervertebral body internal fixation device 10 of this embodiment 10 has a control window 7 that opens in the short axis direction (anterior-posterior direction) near the center of the support beam 4, and as shown in the Z-Z cross section, unlike the posterior side shown in the X-X cross section, gaps are provided in the elastic members 1-1, 1-2, and 1-3 on the anterior side. The support member 6-2 that constitutes the second elastic member 12 can be fitted into these gaps. The other configurations are the same as those of embodiment 9 described with reference to Figure 12.

[0116] Figure 15 is an explanatory diagram showing an example of the configuration and expansion mechanism of the expansion portion of the intervertebral body internal fixation device 10 according to this embodiment 10. The intervertebral body internal fixation device 10 of this embodiment 10 has a second elastic member 12 as an expansion portion, as described above. The second elastic member 12 is supported by a support member 6-2 and consists of a total of six pairs of elastic members 12-1, 12-2, and 12-3 that are symmetrical left and right and paired up and down. Each pair of elastic members 12-1, 12-2, and 12-3 has its own individual elasticity. In this respect, it is the same as the elastic members 1-1, 1-2, and 1-3 of the main body portion. The individual elastic members 12-1, 12-2, and 12-3 have a support column and a plate-shaped member extending from the support column, similar to the elastic members 1-1, 1-2, and 1-3 of the main body portion, and function as a leaf spring. Multiple second elastic members 12-1, 12-2, and 12-3 are connected to a support member 6-2 and arranged in the longitudinal direction (lateral direction), with each plate-like member configured to protrude forward. The connection points between the multiple second elastic members 12-1, 12-2, and 12-3 and the support member 6-2 are configured to fit into notch structures (gaps, groove structures) provided in front of the elastic members 1-1, 1-2, and 1-3. The size of the notches is adjusted so as not to impair the rigidity of the support columns constituting the elastic members 1-1, 1-2, and 1-3.

[0117] Although not shown in Figure 15, it is even preferable to provide a deformation limiting member 5, as explained with reference to [B] and [C] in Figure 24. The contact surfaces of the individual elastic members 12-1, 12-2, and 12-3 are deflected towards the center by the load from above and below, and come into contact with the deformation limiting member 5, preventing further deflection. This reduces the risk of the plate-shaped members fracturing due to metal fatigue caused by repeated loading on the elastic members 12-1, 12-2, and 12-3.

[0118] Figure 15 shows a top view when housed, illustrating the state in which the second elastic member 12 is housed in the space formed in the elastic member 1 (see the Z-Z cross-section in Figure 14), and a top view when protruded, illustrating the state in which it extends forward (ventral) from the elastic member 1. The top and middle sections show a Z-Z cross-section. The main body shown in Figure 14 is shown by a dashed line, while the extended parts, elastic members 12-1, 12-2, 12-3, support member 6-2, and control rod 8, are shown by solid lines.

[0119] The intervertebral body internal fixation device 10 of this embodiment 10 has a structure in which elastic members 12-1, 12-2, and 12-3 can be housed in spaces formed in the elastic members 1-1, 1-2, and 1-3 of the main body portion (see the Z-Z cross-sectional view in Figure 14), as shown in the Z-Z cross-sectional view of Figure 15.

[0120] The rear side (upper side in the top view) of the support member 6-2 is triangular when viewed from above, so that it can be inserted into the control window 7 located in the center of the support beam 4 of the main body when it is in its retracted state. The support beam 4 is hollow, and the control rod 8 is inserted into the hollow portion of the support beam 4 and can be slid in the longitudinal direction (left-right direction). The tip of the control rod 8 has a taper, and by pressing the right triangular side of the support member 6-2 when it is in its retracted state, the support member 6-2 is pushed forward, and the elastic members 12-1, 12-2, and 12-3 are pushed forward through the notched structure (gap, groove structure) formed in the elastic member 1 of the main body, thereby transitioning to a protruding state. The shape of the support member 6-2 does not need to be a strict triangle; it is sufficient if it has a sloping structure in the longitudinal direction and can transition to a protruding state when the control rod 8 is inserted.

[0121] For the sake of understanding, the control rod 8 is illustrated and explained as having a triangular tip when viewed from above, and as sliding parallel to the long axis. However, it is preferable to employ a mechanism in the support member 6-2 that can apply greater force. In practice, pushing the elastic member 12 into the intervertebral disc cavity may require, for example, pushing open the vertebral endplate compressed from above and below, or pushing back the remaining intervertebral disc tissue inside, which may require a large force. For example, as will be detailed with reference to Figure 20 in the following embodiment 11, a screw groove may be formed on the right end of the support beam 4 of the main body, and the tip of the control rod 8 may be made tapered, such as conical or hemispherical, with screw threads formed all over, so that it can be screwed into the screw groove formed on the right end of the support beam 4. By rotating the control rod 8 and advancing it to the left, the tapered structure of the tip, such as conical or hemispherical, can push the right triangular side of the support member 6-2, thereby pushing the support member 6-2 forward. As a result, the torque that rotates the control rod 8 is converted into a force that pushes the support member 6-2 forward, allowing the elastic members 12-1, 12-2, and 12-3 to be pushed out with greater force. Furthermore, since the control rod 8 remains screwed into the support beam 4 and remains in the intervertebral fixation device 10 implanted in the patient's body even after surgery, it is preferable to configure it so that it does not fall out by the aforementioned screw structure, another screw structure, or other fixing means.

[0122] [Embodiment 11] Figure 16 is an image diagram showing a perspective view of one example of the configuration of the intervertebral body internal fixation device 10 according to this embodiment 11. The protruding state is shown on the upper side, and the retracted state is shown on the lower side. The intervertebral body internal fixation device 10 has a configuration that mainly consists of elastic members 1-1, 1-2, and 1-3, similar to the embodiment 9 described above, and also includes a second elastic member 12 supported by a support member 6-2, similar to the embodiment 10, and a third elastic member 13 further supported by a support member 6-3. In the retracted state, the second elastic member 12 is housed in the gap on the front side of the elastic members 1-1, 1-2, and 1-3 of the main body, and the third elastic member 13 is housed in the gap on the rear side. In the protruding state, the second elastic member 12 can protrude from the front side (ventral side) and the third elastic member 13 can protrude from the rear side (dorsal side) of the elastic members 1-1, 1-2, and 1-3 of the main body. This allows the elastic member to be extended not only anteriorly (ventrally) but also posteriorly (dorsally) after the intervertebral body fixation device 10 is inserted into the patient's intervertebral disc cavity. This allows the elastic member to protrude not only in one direction but also in the other after the intervertebral body fixation device 10 is inserted into the patient's intervertebral disc cavity, further expanding the area on which the intervertebral body fixation device 10 can contact the endplate. In the same principle as explained above with reference to Figure 24 in

[12] , the risk of spinal subsidence of the entire intervertebral body fixation device 10 can be reduced, and the load can be distributed not only when the patient flexes forward but also when the spine deforms due to extension.

[0123] Figure 17 is an explanatory diagram showing an exploded, perspective view of the main body portion and extension portion (second and third elastic members 12, 13 and control rod 8) of the intervertebral body internal fixation device 10 according to this embodiment 11. The main body portion is shown in the upper section, the second and third elastic members 12 and 13 and control rod 8 in the retracted state are shown in the middle section, and the second and third elastic members 12 and 13 and control rod 8 in the protruding state are shown in the lower section, all in perspective views. The main body portion is omitted in the middle and lower sections.

[0124] The main body consists of six first elastic members 1 arranged in the longitudinal direction and three in the transverse direction, with the contact surface 2 visible on the upper surface. Anti-slip protrusions are formed on the contact surface 2. The contact surface 2 is also divided into 18 regions in a 6x3 arrangement, each possessing independent elasticity. The base structure 3 at the right end of the intervertebral body internal fixation device 10 has a hole that communicates with the hollow support beam 4, and a screw groove is formed on its inner wall. The control rod 8 shown in the middle and lower sections of Figure 17 has a head and a shaft, with the tip of the shaft being conical or hemispherical, and screw threads are formed on both the shaft and the head. These will be described in detail as the mechanism for transitioning from the retracted state to the protruding state with reference to Figure 20, so a detailed explanation is omitted here.

[0125] In the housing state (middle section), the second elastic member 12 and the third elastic member 13 are housed in a notched structure (groove structure) provided in the main body, and when viewed from above, they do not extend outward from the contact surface 2 of the main body. The middle section of Figure 17 is a perspective view image in which the main body is not drawn. The housing state as referred to in this invention does not mean that the second elastic member 12 and the third elastic member 13 are not allowed to protrude from the main body at all; it is sufficient that the second and third elastic members 12 and 13 are housed to the extent that they do not hinder the insertion of the intervertebral body internal fixation device 10 into the intervertebral disc cavity of the patient. The anterior (ventral) second elastic member 12 is divided into multiple sections along its long axis, and each section is connected to a support member 6-2 to form an integral structure. Similarly, the posterior (dorsal) third elastic member 13 is also divided into multiple sections along its long axis, and each section is connected to a support member 6-3 to form an integral structure. The connecting portion of the second elastic member 12 in support member 6-2 and the connecting portion of the third elastic member 13 in support member 6-3 are configured to fit into notched structures (groove structures) provided on the front and rear of elastic members 1-1, 1-2, and 1-3, respectively. By adjusting the size of the notches, the rigidity of the base portion constituting elastic members 1-1, 1-2, and 1-3 can be maintained.

[0126] Support members 6-2 and 6-3 are inserted into control windows 7 formed in the main support beam 4 (not shown), and are supported so as to slide in the front-rear direction. Within the same control window 7, they are assembled and housed so as not to interfere with each other in the short axis direction. As shown in the middle section, the housed support members 6-2 and 6-3 are pushed out by inserting the control rod 8 into the main body from the right side (downward right direction of the paper), transitioning to the protruding state shown in the lower section. The mechanical mechanism at this time will be described in detail later with reference to Figure 20. In addition, the amount of forward (ventral) or rearward (dorsal) protrusion of the second and third elastic members 12 and 13 can be adjusted according to the shape of the area near the center (long axis) of the short axis of support members 6-2 and 6-3. For example, depending on the individual patient's intervertebral disc cavity condition, the second and third elastic members 12 and 13, each having support members 6-2 and 6-3 of an appropriate shape, or the second elastic member 12 in which the support member 6-2 in embodiment 10 is appropriately designed, can be selected and used in combination with the main body portion of the intervertebral body fixation device 10.

[0127] Figures 18 and 19 are explanatory diagrams that show in detail an example of the configuration of the intervertebral body internal fixation device 10 of this embodiment 11. Figure 18 shows the housed state, and Figure 19 shows the protruding state. In both figures, the first row is a plan view, the second to fifth rows show cross-sectional views A-A, E-E, F-F, and G-G in order, and below that, from left to right, cross-sectional views H-H, D-D, I-I, C-C, and J-J in order, with a part of cross-sectional view A-A shown on the right as detail view B. Note that, to avoid making the figures cluttered, only some of the reference numerals are indicated by leader lines.

[0128] As shown in cross-sectional diagrams E-E and F-F, the thickness of the elastic members 1-1 to 1-3 of the main body is thicker near the center in the left-right direction and becomes thinner towards the periphery. As shown in cross-sectional diagrams H-H, I-I, C-C, and J-J, the front side (ventral side, lower part of the paper) is thicker than the rear side (dorsal side, upper part of the paper). The second elastic member 12 housed on the front side (ventral side) has two elastic plates each at the top and bottom, supported by the support member 6-2, while the third elastic member 13 housed on the rear side (dorsal side) has one elastic plate each at the top and bottom, supported by the support member 6-3.

[0129] Cross-sectional diagram A-A shows a cross-section slightly anterior to the long axis of the intervertebral body internal fixation device 10, with a detailed diagram B, which is an enlarged portion of the cross-sectional diagram, on the right, and cross-sectional diagram G-G shown in the fifth row. As shown in cross-sectional diagram A-A, the elastic plates 1-1, 1-2 and the deformation limiting member 5 are supported by the support beam 4, and as shown in detailed diagram B, the support members 6-2 and 6-3 of the second and third elastic members 12 and 13 are inserted into and supported by the control window 7 formed in the support beam 4.

[0130] In the retracted state, as shown in the cross-sectional view G-G of Figure 18, support members 6-2 and 6-3 are combined near the center in the short axis direction, and as shown in the cross-sectional view A-A, one or both are inserted into and supported by a control window 7 formed in the support beam 4. In the protruding state, as shown in the cross-sectional view G-G of Figure 19, when the control rod 8 is inserted, support member 6-2 is pushed forward (ventral side) and support member 6-3 is pushed backward (dorsal side), and as shown in the plan view of Figure 19, the second elastic member 12 supported by them protrudes forward (ventral side) and the third elastic member 13 protrudes backward (dorsal side) from the first elastic member.

[0131] Figure 20 is an explanatory diagram of the mechanism for transitioning the intervertebral body internal fixation device 10 of this embodiment 11 from the retracted state to the protruding state. It corresponds to the cross-sectional view G-G in Figures 18 and 19, with the retracted state shown in the upper section, the transition state to the protruding state in the middle section, and the protruding state in the lower section. Note that reference numerals are only shown in some parts of the figure to avoid making the figure cluttered.

[0132] In the housing state, the support member 6-2 of the second elastic member 12 and the support member 6-3 of the third elastic member 13 are inserted into a control window 7 (not shown in the figure) formed in the support beam 4 and are joined together near the center in the short axis direction. Here, being joined together means that they are inserted sharing a region within a single control window 7, and in Figure 20, they are inserted sharing a region on the left and right sides, similar to Figures 18 and 19. The support beam 4 has a through hole in the long axis direction, and a hole is formed on the right side of the main body portion of the intervertebral body internal fixation device 10 that communicates from the base structure 3 to the through hole in the support beam 4, with a small-diameter screw groove 41 and a large-diameter screw groove 42 formed concentrically. The right end of support member 6-3 and the second from the right of support member 6-2 have a slope that opens more to the right in the front-to-back direction. The control rod 8 has a tapered structure, such as a conical or hemispherical tip, and is inserted into a through-hole in the support beam 4. It is configured so that its tip can be moved in the longitudinal direction (left-right direction). A screw groove 41 is formed on the right end of the support beam 4, and a screw thread 81 is formed on the shaft 83 of the control rod 8 that engages with the screw groove 41. By rotating and screwing in the control rod 8, the right inclined surface of the support member 6-3 in its housing state is pushed, pushing the support member 6-3 backward and pushing out the third elastic member 13 from the notch formed in the elastic member 1 of the main body. By further rotating and screwing in the control rod 8, the right inclined surface of the support member 6-2 is pushed, pushing the support member 6-2 forward and pushing out the second elastic member 12 from the notch formed in the elastic member 1 of the main body. The control rod 8 is then fixed in a position where it is pushed all the way to its end. The control rod 8 has a screw thread 81 in the center of the shaft 83, which is provided for a mechanism to push the support members 6-2 and 6-3 forward or backward, respectively, and also has a fixing screw thread 82 on the head of the control rod 8. The fixing screw thread 82 can be screwed into a large-diameter screw groove 42 separately provided at the entrance of the intervertebral body internal fixation device 10, fixing the control rod 8 in a pushed position within the main body. When fastened with a torque above a certain level, it functions as a locking screw, creating a large fixing force between the control rod 8 and the intervertebral body internal fixation device 10, preventing the control rod 8 from easily coming out of the intervertebral body internal fixation device 10.

[0133] As explained above, we have exemplified a configuration in which a mechanism is used to convert the torque of the control rod 8 into a pushing force using a screw structure, but the control mechanism for switching between the retracted state and the protruding state can be changed as needed.

[0134] As described above, Figure 20 illustrates a structure in which the area of ​​one control window 7 is divided left and right by support members 6-2 and 6-3, but a structure in which it is divided vertically can also be adopted.

[0135] Figure 21 is an explanatory diagram showing a modified example of a control mechanism for switching between the retracted and extended states. It corresponds to the cross-sectional view G-G in Figures 18 and 19, with the retracted state shown in the upper section and the extended state in the lower section, although the main body portion has been changed to a dashed line. The W-W cross-section is shown to the left of each.

[0136] In this modified example, the internal cavity of the support beam 4 in the main body is enlarged by changing the through-hole from circular to square. The support beam 4 is provided with control windows 7 at multiple locations, similar to those shown in Figure 17. By enlarging the internal cavity of the support beam 4 in the main body, the control windows 7 can open widely in the vertical direction. The support members 6-2 and 6-3 have a width that allows them to be inserted into the control window 7, which is slightly narrower than the width of the control window 7 when viewed from above, and are plate-like in shape that overlap vertically within the control window 7. As shown in the lower part of Figure 21, the support members 6-2 and 6-3 have a slope that opens wider front to back (up and down of the paper) as they move to the right along the long axis when viewed from above. In the housing state, because they overlap vertically, as shown in the upper part of Figure 21, only the slope of support member 6-3 is visible, and the slope of support member 6-2 is hidden below it.

[0137] The tip of the control rod 8 is triangular or conical in shape. By moving the control rod 8 from right to left, the support member 6-2 is pushed forward, pushing the second elastic member 12 out of the notch structure in the elastic member 1 of the main body. By pushing the right inclined surface of the support member 6-3, the support member 6-3 is pushed backward, pushing the third elastic member 13 out of the notch structure formed in the elastic member 1 of the main body. The portions of the support members 6-2 and 6-3 that are inserted into the control window 7 can each be formed in a plate shape on the same plane, and their inclinations can be formed across multiple locations, so the angle of inclination can be made smaller compared to the example in Figure 20. The tip of the control rod 8 is triangular or conical in shape so that it can push this inclination. By making the angle of inclination smaller in this way, the ratio of the distance the support members 6-2 and 6-3 move outward to the distance the control rod 8 moves to the left can be made smaller compared to the case where the angle of inclination is large, so that the force required to push out the second and third elastic members 12 and 13 can be reduced.

[0138] In Figure 21, the tip of the control rod 8 is shown as sharp, matching the inclination of the support members 6-2 and 6-3. However, it may be a blunt triangle or cone, or even an arc (hemispheric), cylinder, or rectangular prism. Matching the inclination at the same angle allows for stable force transmission by applying pressure across a surface. However, even if it is a blunt triangle, cone, or other shape, the only difference is that the contact changes from a surface to a point; the ratio of the outward movement distance of the support members 6-2 and 6-3 to the leftward movement distance of the control rod 8 remains unchanged.

[0139] Furthermore, the mechanism for moving the control rod 8 in the longitudinal direction is optional. Similar to Figure 20, a screw groove is provided on the right end side of the support beam 4 of the main body, and the control rod 8 is configured to have a conical or hemispherical tip with screw threads on the shaft portion that screw into the screw groove of the support beam 4. In this way, similar to Embodiment 10, the control rod 8 can be rotated and moved from right to left, and the torque at that time can be converted into a force that pushes out the second and third elastic members 12 and 13. This allows for pushing with an even greater force.

[0140] The present invention has been specifically described above based on embodiments, but it goes without saying that the present invention is not limited thereto and can be modified in various ways without departing from its essence. That is, the intervertebral body internal fixation device 10 of the present invention is preferably equipped with multiple elastic bodies, represented by elastic plates (1-1, 1-2, 1-3, etc.), each having a plurality of divided contact surfaces (2-1, 2-2, 2-3, etc.) sandwiched between rigid base structures 3 arranged at both the left and right ends. Furthermore, it is preferable that the multiple elastic bodies are configured such that when the contact surfaces are aligned to the same height as the base structure 3, their elasticity disappears, and they support vertical loads as a rigid body integrated with the base structure 3. In each embodiment, multiple elastic members are shown, each having a pair of upper and lower contact surfaces and individual elasticity, but they do not necessarily have to be in pairs. That is, the regions of the upper and lower contact surfaces do not need to be the same. For example, the upper surface supporting the vertebral endplate may have an elastic member with six contact surfaces, while the lower surface supporting the vertebral endplate may have an elastic member with two contact surfaces, thus differentiating the number of contact surfaces between the upper and lower surfaces. In other words, multiple elastic members, each with independent elasticity in a specific region, may be arranged in different numbers on the upper and lower surfaces. Furthermore, the term elasticity as used herein is also used to mean ease of deformation under load, or flexibility. A reduction in the elasticity of an elastic member means that it becomes more difficult to deform under load, thus increasing its rigidity. As long as the gist of this invention is not departed, various methods can be used to divide the contact surfaces and to mount the elastic body.

[0141] This invention can be used in intervertebral body internal fixation devices that are inserted and implanted between vertebral bodies.

[0142] 1, 1-1, 1-2, 1-3 Elastic plate (first elastic member) 2, 2-1, 2-2, 2-3 Contact surface 3 Base structure 4 Support beam (first support member) 5 Deformation limiting member 6-2, 6-3 (second and third) support members 7 Control window 8 Control rod 10 Intervertebral body internal fixation device 12, 12-1, 12-2, 12-3 Second elastic member 13, 13-1, 13-2, 13-3 Third elastic member 21, 21-1, 21-2 Support column 22, 22-1, 22-2 Plate-shaped member 41, 42 Screw groove 80 Tip 81, 82 Screw thread 83 Shaft

Claims

1. An intervertebral fixation device inserted into the intervertebral space between an upper vertebral body and a lower vertebral body, wherein the intervertebral fixation device comprises a plurality of elastic members, each having a pair of upper and lower contact surfaces for contacting the endplates of the upper and lower vertebral bodies, and the plurality of elastic members each have elasticity between the pair of upper and lower contact surfaces.

2. The intervertebral body internal fixation device according to claim 1, wherein the elasticity between the paired upper and lower contact surfaces is independent for the plurality of elastic members.

3. The intervertebral body internal fixation device according to claim 1 or 2, further comprising a base structure extending in the short axis direction at both ends in the long axis direction, and a support beam connecting the base structure, wherein each of the plurality of elastic members comprises a pair of upper and lower elastic plates, is supported by the base structure or the support beam and arranged in the long axis direction, the contact surfaces are arranged to form surfaces that are substantially continuous with the base structure in the long axis direction on the upper and lower sides, and the intervertebral body internal fixation device is such that the elastic plates can bend along the long axis as well as in the vertical direction in response to a vertical load.

4. The intervertebral body internal fixation device according to claim 3, wherein each of the elastic plates has a front end that moves in a direction that narrows the gap in response to a vertical load and a rear end on the opposite side, and the front ends of adjacent elastic plates across the gap come into contact when the vertical load exceeds a predetermined value.

5. The intervertebral body internal fixation device according to claim 3, wherein at least one pair of elastic plates are bent toward the vertical center at the end opposite to the end supported by the base structure or the support beam, in the direction of the long axis.

6. The intervertebral body internal fixation device according to claim 5, wherein the bent ends of the at least one pair of elastic plates are connected to the base structure or the support beam.

7. An intervertebral body internal fixation device according to any one of claims 1 to 6, wherein the elastic plate is a plurality of plates in the direction of the short axis.

8. The intervertebral body internal fixation device according to claim 3, wherein the base structures at both ends in the longitudinal direction are connected to each other by the support beams at both ends in the longitudinal direction, at least one pair of elastic plates are integrally formed with the base structure, and at least one other pair of elastic plates are connected to and supported by the base structure.

9. The intervertebral body fixation device according to claim 1 or 2, wherein at least a portion of the plurality of elastic members further comprises deformation-limiting members that contact the inner surfaces of the contact surfaces and increase rigidity when the distance between the paired upper and lower contact surfaces is reduced and the contact surfaces are subjected to loads from above and below.

10. The intervertebral body internal fixation device according to claim 1, 2, or 9, wherein the plurality of elastic members are arranged in line along the longitudinal axis, and each of the plurality of elastic members comprises upper and lower plate-like members forming the contact surface and a support column extending in the vertical direction, the plate-like members having vertical elasticity by having one end supported by the support column and the other end open, and the rigidity increasing when a vertical load is applied to the contact surface by the other end contacting the upper and lower ends of the support column of an adjacent elastic member.

11. The intervertebral body internal fixation device according to claim 1, 2, 9, or 10, further comprising a base structure extending in the short axis direction at both ends in the long axis direction and a support beam connecting the base structure, wherein the plurality of elastic members are supported by the base structure or the support beam and arranged in the long axis direction, and the contact surfaces are arranged to form surfaces that are substantially continuous in the long axis direction from the base structure on the upper and lower sides, respectively.

12. The intervertebral body internal fixation device according to claim 11, wherein the support beam is a first support member, the elastic member is a first elastic member, the intervertebral body internal fixation device further comprises one or more second elastic members supported by a second support member, and the intervertebral body internal fixation device is configured to be able to take two states: one in which the one or more second elastic members are housed in the gaps between the plurality of first elastic members, and one in which the second elastic members protrude from the first elastic members in one direction in the short axis direction when viewed from above.

13. The intervertebral body internal fixation device according to claim 12, further comprising a control rod, the support beam comprising a hollow portion in the longitudinal direction and a control window in the short direction, the second support member being inserted into and supported in the hollow portion through the control window and capable of sliding in the short direction, and the control rod being inserted into the hollow portion from the longitudinal direction and pushing the second support member in the short direction, thereby transitioning the second elastic member from the housing state to the protruding state.

14. The intervertebral body internal fixation device according to claim 12, further comprising one or more third elastic members supported by a third support member, wherein in the housing state, the one or more third elastic members are housed in the gaps between the plurality of first elastic members, and in the protruding state, when viewed from above, the third elastic member protrudes from the first elastic members in the other direction in the short axis direction.

15. The intervertebral body internal fixation device according to claim 14, further comprising a control rod, the support beam comprising a hollow portion in the longitudinal direction, a first control window in the short direction, and the other second control window in the short direction, the second support member being inserted into and supported in the hollow portion from the first control window and capable of sliding in the short direction, the third support member being inserted into and supported in the hollow portion from the second control window and capable of sliding in the short direction, and the control rod being inserted into the hollow portion from the longitudinal direction to push the second support member in the short direction and push the third support member in the other direction in the short direction, thereby transitioning the second and third elastic members from the housing state to the protruding state.

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