Expandable Intervertebral Cage

Abstract

The present disclosure relates to an expandable intervertebral cage (1) comprising: a base (2) having a circumferential sidewall (7) extending in a first direction (x) and a first bone-interacting surface (5); a stage (3) having a second bone-interacting surface (6) disposed essentially opposite the first bone-interacting surface (5) with respect to the expandable intervertebral cage (1); and a fixation mechanism (4) that fixes the position of the second bone-interacting surface (6) of the stage (3) relative to the first bone-interacting surface (5) of the base (2) at least in the first direction (x) and that is at least partially disposed within the circumferential sidewall (7) of the base (2).

Description

[Technical Field]

[0001] The present disclosure relates to an expandable intervertebral cage, hereinafter also referred to as a cage, which can be brought into an intervertebral space as an implant in a retracted state and, once in place, can be expanded to a desired expanded state. [Background technology]

[0002] Vertebrae are the individual irregular bones that make up the spine, a bending and flexible column under normal circumstances. Humans normally have 33 vertebrae, including five fused together to form the sacrum (the others are separated by intervertebral discs) and four coccyx (tailbone) that form the tailbone. Three upper regions contain the remaining 24 vertebrae, and these regions are designated cervical (7 vertebrae), thoracic (12 vertebrae), and lumbar (5 vertebrae), depending on the region the vertebrae occupy.

[0003] Various devices are known in the prior art that can be inserted between two adjacent vertebrae to adjust the distance and spacing between them. These devices can be used temporarily, for example, during surgery when access to a particular surface of a vertebral member is necessary. The device can also be left permanently in the patient as an implant to stabilize the vertebral member. One such permanent device can be a fusion cage, which provides a filling chamber for inserting a bone graft between adjacent portions of bone. Over time, the bone and bone graft grow together through or around the fusion cage, firmly fusing the bone graft and bone together. One current use of fusion cages is to treat various spinal disorders, including degenerative disc disease, such as lumbar grade I or II spondylolisthesis. A spinal fusion cage (collectively referred to as "fusion cage") is inserted into the disc space between two vertebrae to fuse them together. Spinal fusion cages stabilize the vertebrae by expanding (or distracting) the collapsed disc space between two vertebrae, preventing the vertebrae from moving relative to one another. The application of intervertebral cages for spinal segment fusion in addition to pedicle screws typically increases fusion rates between 10% and 15%. Larger cages, implanted via a lateral or anterior approach, can even be inserted into the intervertebral space standalone without the addition of pedicle or other screws, providing a sufficient mechanical base for a solid fusion. Summary of the Invention [Problem to be solved by the invention]

[0004] Surgical challenges in intervertebral cage placement typically involve limited access space due to bony structures, such as endplates or facet joints, and neural structures, such as the dural sac and nerve roots, in the case of dorsal approaches, and vascular structures in the case of anterior or lateral approaches. The most commonly used approach for cage placement is dorsal in nature and is often referred to as posterior lumbar interbody fusion (PLIF) or lateral lumbar interbody fusion (LLIF). With the PLIF approach, the nerve roots and dural sac are retracted medially to open the disc space and allow for disc removal before inserting the intervertebral cage. Therefore, the intervertebral cage has very limited dimensions to fit into the disc space. Furthermore, once fitted, the intervertebral cage must be accessed (usually on one side) to expand the cage. The challenges of inserting a lumbar lateral interbody fusion (LLIF) cage lie in the limited access space in the soft tissue structures and the difficulty of creating an interbody space large enough to place an optimally sized cage without damaging the vertebral endplates.

[0005] As mentioned above, expandable intervertebral cages are known from the prior art, however these devices typically have rather complex structures and are not self-stabilizing, which often poses a risk of inadvertently collapsing the structures when they are in the intervertebral space. [Means for solving the problem]

[0006] The present disclosure overcomes these challenges by providing a simple yet robust and versatile intervertebral cage having a shallow design that allows the cage to be inserted into the disc space minimally invasively through a relatively small opening compared to prior art.

[0007] The present disclosure relates to an expandable intervertebral cage including a base and a stage displaceable relative to the base. The base includes a peripheral sidewall extending in a first direction and having a first bone-interacting surface. The stage has a second bone-interacting surface disposed essentially opposite the first bone-interacting surface relative to the expandable intervertebral cage. For improved fusion capability, the first bone-interacting surface and / or the second bone-interacting surface may at least partially surround an opening for a filling chamber for receiving a bone graft. The base and / or the stage may include multiple components that are connected to each other.

[0008] Depending on the application, the stage can be displaced relative to the base only in the first direction. In that case, the first bone-interacting surface and the second bone-interacting surface can be arranged at a fixed angle relative to each other so that the lumbar angle of the vertebra can be taken into account. However, if individual adjustment of the lumbar angle is required, the stage can be further tilted about an additional direction. Depending on the application of the cage (e.g., LLIF or PLIF), the stage can be tilted about a second direction or a third direction. In the context of the present disclosure, the first direction, the second direction, and the third direction are essentially perpendicular to each other. For lumbar lateral interbody fusion (LLIF) applications, the stage is advantageously tiltable relative to the base about the second direction. Meanwhile, for lumbar posterior interbody fusion (PLIF) applications, the stage is preferably tiltable relative to the base about the third direction. Thereby, the second direction and the third direction can be further defined as follows: That is, when the cage has an essentially rectangular parallelepiped shape, the peripheral side wall can be divided into a first side wall, a second side wall, a third side wall, and a fourth side wall, and the first and second side walls are shorter than the third and fourth side walls. The third and fourth side walls can then extend in the second direction. As a result, the first and second side walls can extend in the third direction. Therefore, for lumbar lateral interbody fusion applications, the stage preferably tilts about a second direction parallel to the third and fourth walls, while for lumbar posterior interbody fusion applications, the stage can tilt about a third direction parallel to the first and second walls.

[0009] For reliable positioning and expansion, the cage can be expanded with the aid of a tool instead of housing a complex expansion mechanism within the cage. Such a tool can be inserted into the cage and serves to expand the cage from the retracted state to at least one expanded state by lifting and / or tilting the stage relative to the base. However, for fine adjustment, the cage can be expanded from the retracted state to multiple (intermediate) expanded states until the fully expanded state is achieved. Advantageously, the cage can be expanded from a minimum height of 5-13 mm in the retracted state to a maximum height of 9-19 mm in the fully expanded state. Furthermore, if tilting is intended, the tilting angle can be in the range of 0-15°. However, even if expansion can be performed by an external tool, the cage needs to provide a looking mechanism to lock the cage in at least one expanded state (such as intermediate expanded state(s) and / or the fully expanded state) and thus avoid accidental collapse of the cage. Therefore, the locking mechanism preferably includes at least one latch displaceable between a locked position and an unlocked position relative to a first direction, particularly in a second direction. This allows the stage to be supported and fixed relative to the base in a first direction in the fixed position. Meanwhile, in the unlocked position, at least one latch is displaceable relative to the base in the first direction. Furthermore, in the unlocked position, the base and the stage can be disengaged and therefore disassembled. Depending on the application, the number of latches may vary. Advantageously, the latches are disposed within the peripheral sidewall of the base in the fixed and unlocked positions. If the stage only needs to be lifted relative to the base in the first direction, one latch is sufficient. If the stage is to be tiltable further, two latches (e.g., a first latch and a second latch) may also be used.

[0010] However, if only one latch is used, it may be advantageous for the latch to be frame-shaped having first, second, third, and fourth inner walls, the first and second inner walls being shorter than the third and fourth inner walls. In the attached position, the first inner wall may be positioned adjacent to the first side wall of the base, the second inner wall may be positioned adjacent to the second side wall of the base, and so on. For superior fusion capabilities, the frame-shaped latch may enclose a fill chamber for accommodating bone graft.

[0011] Regardless of the application, the at least one latch preferably includes at least one first tooth configured to latch with at least one second tooth arranged on the base in the fixed position. However, for fine adjustment of height (in the first direction) and / or tilt angle, multiple first and / or second teeth are advantageous. The multiple first and / or second teeth are preferably arranged in rows, with the multiple teeth in each row spaced apart from one another in the first direction. This allows at least one row of the multiple first teeth to be arranged on the outer side of the at least one latch. The outer side of the latch thereby faces the inner side of the peripheral side wall of the base in the mounted position. For a frame-shaped latch, the rows of first teeth can be arranged opposite each other on the third and fourth inner walls of the latch, for example. Thus, at least one row of the multiple second teeth can be arranged on the inner side of the peripheral side wall (particularly the third and fourth side walls). Preferably, grooves extending in the first direction are arranged adjacent to the second row of teeth on the inner side. Thus, in the second direction, the second row of teeth is arranged adjacent to the respective grooves. Also, on the outer side of the latch, respective grooves may be arranged adjacent to the first row of teeth. Thus, on the inner and / or outer sides, grooves and rows may be arranged alternately next to each other. By displacing at least one latch in the second direction, the first tooth (or at least one row of first teeth) of the latch disengages from the second tooth (or at least one row of second teeth). In the unlocked position, the first tooth (or at least one row of first teeth) is then arranged in the respective grooves of the peripheral side wall. Additionally or alternatively, the second tooth (or at least one row of second teeth) is arranged in the respective grooves of the latch. Thus, in the unlocked position, no undercut is formed between the latch and the base in the first direction. If the cage has an essentially rectangular parallelepiped shape, the second teeth or rows of second teeth may be arranged only on the third and fourth side walls, whereby a pair of oppositely arranged rows of second teeth is advantageous for the overall stability of the cage.Thus, preferably, at least one row of second teeth is disposed on the third side wall opposite a corresponding row of second teeth disposed on the fourth side wall. If only one latch is used, the rows of first teeth of the latch may also be disposed in pairs opposite each other relative to the latch.

[0012] To move the at least one latch from the locked position to the unlocked position, the at least one latch may include a thread extending to the latch in the second direction. A screw extending from the base or stage to the latch may further engage the thread. By operating the screw, the respective latch is displaced relative to the base in the second direction, thereby displacing the first tooth from the locked position to the unlocked position. Preferably, the screw is operable through an opening disposed in a first side wall of the peripheral side walls. Further, a tool opening for receiving a tool to expand the cage may be disposed in the first side wall. Preferably, the tool opening is centered on the first side wall in the third direction. When inserted, the tool may engage with a tool connecting surface on the cage (preferably also centered on the cage in the third direction) to temporarily attach the tool during operation or cage expansion.

[0013] As described above, the expandable intervertebral cage can include more than one latch, specifically a first latch and a second latch. Having two latches allows the stage to tilt relative to the base. Thus, the first and second latches can be independently displaced relative to each other in a second direction from their respective locked positions to unlocked positions. In the unlocked position, each latch in the unlocked position can also be displaced in the first direction. Therefore, a fixation mechanism including two latches displaceable in a second direction from a locked position to an unlocked position, as described in more detail below, is particularly suitable for lumbar lateral interbody fusion applications, whereby the stage can be tilted about a second direction parallel to the third and fourth walls. The first latch can thereby extend along the third side wall, and the second latch can extend along the fourth side wall of the cage's peripheral side walls. In this case, the first tooth of the first latch can engage with the second tooth located on the third side wall when the first latch is in its locked position, and the first tooth of the second latch can engage with the second tooth located on the fourth side wall when the second latch is in its locked position. As described above, each latch can have a screw thread for displacing each latch independently of the other. Thus, the two screws that operate each latch can be positioned opposite each other with respect to the tool opening (extending through the first side wall). As described above, the tool opening serves to insert a tool into the cage so that the tool can be interconnected with the tool connection surface of the cage.

[0014] When two latches are present, the tool connection surface is preferably disposed between the first and second latches in the third direction. Thus, in the unlocked position, a tool can support the first and second latches to prevent the latches from disconnecting from the base. Meanwhile, in the locked position, the first and second latches can support each other in the third direction, thus preventing the latches from disconnecting from the base in the absence of a tool. Thus, the first latch can include a first support, and the second latch can include a second support. In the locked position, the first support and the second support can then brace each other in the third direction. For space-saving design, it is advantageous if the first support and the second support are disposed at the mounting position opposite the tool opening. Thus, the first and second supports can be disposed adjacent to the second side wall of the peripheral side wall.

[0015] Instead of two latches, other mechanisms can be used for tilting. For example, the latch and stage can be displaced together (to an unfixed position) relative to the base in a first direction (allowing for height adjustment of the cage), and the stage can tilt independently of the latch and base (allowing for lumbar angle adjustment of the patient). Thus, the intervertebral cage can include, for example, a rotatable camshaft configured to tilt the stage relative to the base and latch. Preferably, the camshaft extends in a second direction. Thus, by rotating the camshaft, the cam lifts the stage from the latch on one side of the cage, thereby tilting the stage relative to the base (and latch). The camshaft can be attached to the latch and / or a mounting frame, as described in more detail below. Thus, the latch can have at least one opening or recess for mounting the camshaft. For this application, it can be advantageous if the latch is further frame-shaped, as described above. The camshaft can then be positioned adjacent to the third inner wall of the latch, and a linear guide structure, described below, can be positioned on the fourth inner wall of the latch, interconnecting the latch and the stage.

[0016] Alternatively, the intervertebral cage may also include a displaceable wedge that facilitates tilting of the stage relative to the latch and base. The wedge may be displaceable in either a second or third direction. The wedge may be disposed between the latch and the stage in the first direction. The wedge has a first smooth surface and a second smooth surface, such that the first and second smooth surfaces are angled relative to each other in the direction of wedge displacement. During displacement, the first smooth surface interacts with a contact surface of the stage, and the second smooth surface interacts with a contact surface of the latch. Thus, by displacing the wedge, the stage is locally raised (only on one side of the cage) relative to the base in the first direction, resulting in tilting of the stage relative to the base (and latch). For this application, it may also be advantageous for the latch to be frame-shaped, as described above. A wedge can then be placed between the third interior wall and the stage, and a linear guide structure, described below, can be placed on the fourth interior wall.

[0017] For reliable displacement, the expandable intervertebral cage may further comprise at least one linear guide structure interconnecting the at least one latch to the stage and configured to support displacement of the at least one latch in the second direction. When two latches are present, two independent linear guide structures per latch are advantageous. Depending on the application, each linear guide structure may be configured to allow rotation of the latch relative to the stage about the second direction. This is particularly useful when tilting is intended, for example, when the at least one linear guide structure may include a rod extending in the second direction interconnecting the stage with the respective latch.

[0018] To further reduce undesired displacement of the base relative to the stage in the second direction, the cage may include at least one strut extending from the stage to the peripheral sidewall of the base at the mounting location.

[0019] If tilting is not intended, at least one latch can be displaceably attached to the stage. However, for tilting applications, the cage can include a mounting frame for mounting a latch that can be displaced in a second direction. The mounting frame can be at least partially disposed within a peripheral side wall of the base, thereby allowing the mounting frame to brace against the peripheral side wall of the base. To attach the latch to the mounting frame, at least one rod can extend at least partially through the latch to the mounting frame. Furthermore, the latch can be interconnected to the stage by a linear guide structure, allowing the stage to tilt relative to the latch and base. Thus, the latch and stage can be displaced together in a first direction (allowing for height adjustment of the cage), and the stage can tilt independently of the latch and base (allowing for lumbar angle adjustment of the patient).

[0020] It is to be understood that both the foregoing general description and the following detailed description are intended to present embodiments and provide an overview and framework for understanding the nature and character of the present disclosure.

[0021] The accompanying drawings are included to provide a further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate various embodiments and, together with the description, serve to explain the principles and operation of the disclosed concepts.

[0022] The invention described herein will be more fully understood from the detailed description and accompanying drawings set forth herein below and should not be considered as limiting the invention as set forth in the appended claims. [Brief explanation of the drawings]

[0023] [Figure 1] 1 shows a first variant of an expandable intervertebral cage in a perspective view. [Figure 2] 2 shows a first variant of the expandable intervertebral cage according to FIG. 1 in a top view. [Figure 3] 3 shows a cross-sectional view of the expandable intervertebral cage according to FIG. 2 along line AA. [Figure 4] 2 shows a first variant of the expandable intervertebral cage according to FIG. 1 in an exploded view. [Figure 5] 1 shows a second variant of the expandable intervertebral cage in a perspective view. [Figure 6] 6 shows a second variant of the expandable intervertebral cage according to FIG. 5 in a top view. [Figure 7] 7 shows a cross-sectional view of the expandable intervertebral cage BB according to FIG. 6 in the retracted state. [Figure 8] 7 shows a cross-sectional view of the expandable intervertebral cage according to FIG. 6 in the expanded state. [Figure 9] 6 shows a second variant of the expandable intervertebral cage according to FIG. 5 in an exploded view. [Figure 10] 1 shows a third variant of the expandable intervertebral cage in an exploded view. [Figure 11] 1 shows a fourth variant of the expandable intervertebral cage in an exploded view. DETAILED DESCRIPTION OF THE INVENTION

[0024] Reference will now be made in detail to certain embodiments, example embodiments of which are illustrated in the accompanying drawings, in which some, but not all, features are shown. Indeed, the embodiments disclosed herein may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will satisfy applicable legal requirements. Wherever possible, like reference numerals are used to refer to like components or parts.

[0025] Figures 1 to 4 show a first variant of the expandable intervertebral cage 1, which is not tiltable. Figures 5 to 9 show a second variant of the expandable intervertebral cage 1, Figure 10 shows a third variant of the expandable intervertebral cage 1, and Figure 11 shows a fourth variant of the expandable intervertebral cage 1. In the second, third, and fourth variants, the stage is tiltable relative to the base.

[0026] In all variations, the expandable intervertebral cage comprises a base 2 and a stage 3 displaceable relative to the base 2 in a first direction (x). The base 2 has a peripheral sidewall 7 extending in the first direction and a first bone-interacting surface 5, and the stage 3 has a second bone-interacting surface 6 disposed essentially opposite the first bone-interacting surface 5 with respect to the expandable intervertebral cage 1. To fix the stage 3 relative to the base 2 in the first direction or the position of the second bone-interacting surface 6 of the stage 3 relative to the first bone-interacting surface 5 of the base 2, the cage comprises a fixation mechanism 4 having at least one latch that supports the stage 3 in a fixed position in the first direction. For a space-saving design, the fixation mechanism 4 can be located entirely within the peripheral sidewall 7 of the base 2, as shown.

[0027] In a first variant shown in FIGS. 1 to 4 , the locking mechanism 4 includes one latch 8 that is displaceable in a second direction (z) essentially perpendicular to the first direction (x) between a locked position and an unlocked position. In the locked position, the stage 3 is supported and fixed in the first direction. In the unlocked position, the latch 8 is displaceable relative to the base 2 in the first direction. The latch 8 thereby includes a plurality of first teeth 10 arranged in rows 14 on an outer side 13 of the latch 8. The first teeth 10 of the rows 14 are spaced apart from one another in the first direction, as can be seen in FIG. 4 . Correspondingly, a plurality of second teeth 11 are arranged in rows 15 on an inner side 12 of the peripheral side wall 7 of the base 2. In the illustrated variant, there are six rows 14 and 15 of each of the first teeth 10 and second teeth 11. In this regard, the second row of teeth 15 is arranged in pairs opposite each other on the peripheral side wall 7, particularly on a portion of the peripheral side wall 7 extending in the second direction (z). The first row of teeth 14 of the latch 8 is also arranged in pairs opposite each other with respect to the latch 8. When the first tooth 10 and the second tooth 11 are engaged, the latch 8 is latched in the locked position. By displacing the latch in the second direction, the first tooth and the second tooth disengage. In the unlocked position, the first row of teeth 14 is located in the respective grooves 18 of the peripheral side wall 7 extending in the first direction. Therefore, no undercut is formed between the latch 8 and the base 2 in the first direction.

[0028] As can be seen in Figure 3, the latch 8 can be displaced by means of a screw 27 that engages with the internal thread 16 of the latch 8. The screw 27 extends through the stage 3 into the latch 8. Furthermore, the latch 8 can be interconnected with the stage 3 by a linear guide structure 17. In the variant shown, the linear guide structure 17 comprises a rod 25 that is attached to the stage 3 and extends through an opening 26 in the latch 8 (compare Figure 4). The rod 25 and the opening 26 extend in the second direction.

[0029] An expansion tool can be inserted into a tool opening 22 located between the base 2 and the stage 3. The tool supports and displaces the stage 3 in a first direction relative to the base 2 in an unlocked position. Once the desired extended position is achieved, the latch 8 can be moved back to the locked position by turning the screw 27. In the locked position, the expansion tool can be removed.

[0030] In the first variation of the expandable intervertebral cage, the first bone-interacting surface 5 and the second bone-interacting surface 6 are disposed at a fixed angle relative to one another, whereas the second, third and fourth variations of the expandable intervertebral cage allow for a variety of different angles between the first bone-interacting surface 5 and the second bone-interacting surface 6, as will be described in more detail below.

[0031] Thus, in the second variant as shown in FIGS. 5 to 9 , the locking mechanism 4 includes a first latch 8 and a second latch 9, which are displaceable in a second direction (z) essentially perpendicular to the first direction (x) between a locked position and an unlocked position. The second latch is thus displaceable independently from the first latch in the first and / or second directions to allow tilting of the stage 3 relative to the base 2 about the second direction (z). The second variant is suitable for LLIF applications. As can be seen in FIG. 9 , the base 2 has a peripheral sidewall 7 extending in the first direction and a first bone-interacting surface 5 (similar to the first variant). A plurality of second teeth 11 are arranged in four rows 15 on the inner side 12 of the peripheral sidewall 7. The plurality of second teeth 11 in each row 15 are spaced apart from one another in the first direction. Similarly, a respective groove 18 extending in the first direction is arranged adjacent to each row 15. The rows 15 (and grooves 18) are arranged in pairs opposite each other relative to the peripheral sidewall 17. Similarly, the first latch 8 and the second latch 9 each include a plurality of rows 14 of first teeth 10, with the number of rows 14 of the first latch 8 and the second latch 9 in the illustrated variation being half the number of rows 15 of the second teeth 11. Each latch 8, 9 includes a thread 16 that engages with a screw 27 extending in the second direction. Rotating the screw 27 with a tool displaces the respective latch 8, 9 in the second direction relative to the base 2, thereby displacing the first teeth 10 from a locked position (in which the first and second rows of teeth 14, 15 are engaged) to an unlocked position (in which the first and second rows of teeth 14, 15 are disposed within the grooves 18).

[0032] The cage further includes, for each latch 8, 9, a linear guide structure 17 configured to position the respective latch 8, 9 relative to the stage 3 in a first direction while supporting displacement of the respective latch 8, 9 in a second direction. In the case of the first latch 8, the linear guide structure 17 includes an omega-shaped guide element 28 (integral) disposed on the first latch 8 and extending in the second direction. When attached, the guide element 28 is positioned and guided by a respective notch 29 in the stage 3 (compare, e.g., FIG. 7 ). In the case of the second latch 9, the linear guide structure 17 includes a rod 25 that extends through a respective opening 26 in the second latch 9 in the second direction and is attached to the stage 3. Both variations of the linear guide structure 17 allow rotation about the second direction. The degree of freedom about the second direction is important for the second cage variation because it allows the cage to tilt about the second direction to account for the patient's lumbar angle. During insertion of the cage between the vertebrae, the cage is in an initial retracted state. Once positioned between the vertebrae, the locking mechanism can be brought to an unlocked position and a tool can be inserted into the tool opening. The tool can be temporarily attached to the cage 1 by the tool interface 23 during operation. With the attached tool, the stage 3 can be lifted in a first direction and tilted relative to the base 2 about a second direction. Once the desired expanded state of the stage 3 is achieved, the screw 27 can be rotated so that the first latch 8 and the second latch 9 are displaced in the second direction and the teeth re-engage in the locked position. As can be seen in FIG. 7 , the first latch 8 further includes a first support 19 that interacts with the second support 20 of the second latch 9 in the locked position. The first support and second support brace against each other in a third direction (y).

[0033] In the first and second variants, the cage 1 further comprises struts 21 extending from the stage 3 to the peripheral side wall 7 of the base 2 at the attachment location to prevent undesired displacement in the second direction and / or undesired tilting about the third direction. Both variants further feature a filling chamber 24 for receiving a bone graft. The filling chamber 24 can be accessed through openings in the first bone-interacting surface 5 and / or the second bone-interacting surface 6.

[0034] In the third variant as shown in FIG. 10 , the fixing mechanism 4 includes only one latch 8, as described in the context of the first variant of the cage 1. However, in contrast to the first variant, the cage 1 further includes a camshaft 30 and a mounting frame 31 to facilitate tilting of the stage 3 relative to the base 2. As can be seen, the camshaft 30 extends in the second direction (z) and is attached between the latch 8 and the mounting frame 31. In the illustrated variant, the linear guide structure 17 includes an omega-shaped guide element 28 (integral with) the latch 8 and extending in the second direction. Once attached, the guide element 28 is positioned and guided in a respective notch in the stage 3. This allows the linear guide structure 17 to rotate about the second direction, so that when the camshaft 30 is rotated and the stage 3 is locally lifted by the cam of the camshaft 30, the stage 3 can be tilted about the second direction relative to the base 2 to take into account the patient's lumbar angle.

[0035] 11 , the cage 1 features the latch 8 and the locking mechanism as described in the context of the first cage 1 variant. However, in contrast to the first variant, the cage 1 further comprises a wedge 32 to facilitate tilting of the stage 3 relative to the base 2. The wedge 32 is disposed between the stage 3 and the latch 8 in a first direction (x), such that a first smooth surface 33 of the wedge 32 interacts with a contact surface of the stage 3, and a second smooth surface 34 of the wedge 32 interacts with a contact surface 35 of the latch 8. Thus, by displacing the wedge 32 in the second direction (z) with a tool, the stage 3 is lifted from the base 2 in the first direction on one side, resulting in tilting of the stage 3 relative to the base 2. In the variant shown, the linear guide structure 17 also includes an omega-shaped guide element 28 arranged on the first latch 8 and extending in a second direction, allowing rotation about the second direction, so that when the wedge 32 is displaced and the stage 3 is locally lifted, the stage 3 can tilt relative to the base 2 about the second direction. It will be understood that the terms used herein are terms of description rather than limitation, and that various changes may be made without departing from the scope of the invention. [Explanation of symbols]

[0036] 1 Expandable Intervertebral Cage 2. Bass 3 Stages 4 Fixing mechanism 5 First bone-interacting surface 6 Second bone-interacting surface 7 Peripheral wall 8 First Latch 9 Second Latch 10 First tooth 11 Second tooth 12 Inside 13 Outside 14 First row of teeth 15 Second row of teeth 16 threads 17 Linear guide structure 18 Groove 19 First support 20 Second Support 21 Strut 22 Tool opening 23 Tool connection surface 24 Filling chamber 25 rods 26 Aperture 27 Screw 28 Guide Elements 29 notches 30 Camshaft 31 Mounting frame 32 Wedge 33 First Smooth Surface 34 Second Smooth Surface 35 Contact surface (latch)

Claims

1. An expandable intervertebral cage (1), comprising: a. a base (2) having a peripheral sidewall (7) extending in a first direction (x) and a first bone-interacting surface (5); b. a stage (3) having a second bone-interacting surface (6) positioned essentially opposite the first bone-interacting surface (5) with respect to the expandable intervertebral cage (1); c. a fixation mechanism (4) at least partially disposed within the peripheral sidewall (7) of the base (2) for fixing the position of the second bone-interacting surface (6) of the stage (3) relative to the first bone-interacting surface (5) of the base (2) in at least the first direction (x) and for fixing the expandable intervertebral cage (1) in at least one expanded state; Equipped with d. The securing mechanism (4) comprises at least one latch (8, 9), i. a fixed position in the first direction (x), in which the stage (3) is supported and fixed relative to the base (2) in the first direction (x) by the at least one latch (8, 9); ii. an unlocked position in the first direction (x), in which the at least one latch (8) is displaceable relative to the base (2) in the first direction (x); and at least one latch (8, 9) disposed displaceably in a second direction (z) essentially perpendicular to the first direction (x) between the first and second latches (8, 9).

2. 2. The expandable intervertebral cage (1) according to claim 1, wherein the at least one latch (8, 9) comprises at least one first tooth (10) configured to latch with at least one second tooth (11) arranged on the base (2) in the fixed position.

3. 3. The expandable intervertebral cage (1) according to claim 2, wherein at least one row (14) of a plurality of first teeth is arranged on an outer side (13) of the at least one latch (8, 9), and the plurality of first teeth (10) of each row (14) are spaced apart from one another in the first direction (x).

4. 4. The expandable intervertebral cage (1) according to claim 2 or 3, wherein at least one row (15) of a plurality of second teeth is arranged on the inner side (12) of the peripheral side wall (7), and the plurality of second teeth (11) of each row (15) are spaced apart from one another in the first direction (x).

5. 4. The expandable intervertebral cage (1) according to any one of claims 1 to 3, wherein the at least one latch (8, 9) is arranged displaceably in the second direction (z) by means of a screw thread (16).

6. 4. The expandable intervertebral cage (1) according to any one of claims 1 to 3, wherein the expandable intervertebral cage (1) comprises a linear guide structure (17) interconnecting the at least one latch (8, 9) to the stage (3) and configured to support displacement of the at least one latch (8, 9) in the second direction (z).

7. 4. The expandable intervertebral cage (1) according to any one of claims 1 to 3, comprising a first latch (8) and a second latch (9) arranged so as to be independently displaceable relative to each other in the first direction (x) and / or the second direction (z).

8. 8. The expandable intervertebral cage (1) according to claim 7, wherein the first latch (8) and the second latch (9) support each other in a third direction (y) in the fixed position.

9. 4. The expandable intervertebral cage (1) according to any one of claims 1 to 3, wherein the expandable intervertebral cage (1) comprises struts (21) extending from the stage (3) to the peripheral side wall (7) at attachment locations such that undesired displacement of the base (2) relative to the stage (3) in the second direction (z) is prevented.

10. 4. The expandable intervertebral cage (1) according to any one of claims 1 to 3, wherein the expandable intervertebral cage (1) comprises a rotatable camshaft (30) or a displaceable wedge (32) for locally lifting the stage (3) relative to the base (2) so that the stage (3) tilts relative to the base (2).

11. The expandable intervertebral cage (1) according to claim 10, wherein the camshaft (30) or the wedge (32) is arranged between the stage (3) and the at least one latch (8) in the first direction.

12. 4. The expandable intervertebral cage (1) according to claim 1, wherein a tool opening (22) configured to receive a tool for displacing the stage (3) relative to the base (2) in the first direction (x) is disposed between the base (2) and the stage (3).

13. 13. The expandable intervertebral cage (1) according to claim 12, wherein the base (2) and / or the stage (3) comprises a tool connection surface (23) for temporary attachment of the tool during operation.

14. 4. The expandable intervertebral cage (1) according to any one of claims 1 to 3, wherein the first bone-interacting surface (5) and the second bone-interacting surface (6) are arranged at an angle relative to each other.

15. 4. The expandable intervertebral cage (1) according to any one of claims 1 to 3, wherein said at least one latch is in the form of a frame surrounding a filling chamber (24) for accommodating a bone graft.

Images