Expandable Intervertebral Cage

Abstract

An expandable intervertebral cage for spacing two vertebral bodies of a spinal column comprises a first plate and a second plate opposite said first plate, both plates having an axially elongated planar structure along a central longitudinal axis extending from a proximal end to a distal end of the intervertebral cage. The two plates have respective inner surfaces facing each other and respective outer contact surfaces, the latter adapted to receive a corresponding vertebral body for resting. The intervertebral cage comprises a movement and adjustment mechanism of the two plates adapted to facilitate relative mutual translation of the first and second plates parallel to each other to vary the height of the intervertebral cage to space two adjacent vertebral bodies, and rotation of one relative to the other about their respective hinge axes to vary the mutual inclination of the two plates to correct a deformity of the spinal column. The translation and adjustment mechanism comprises a single central shaft coaxial with the central longitudinal axis and having an external thread, and proximal and distal wedges disposed between the first and second plates, the proximal and distal wedges being aligned along the central longitudinal axis and coupled to the external threads of the central shaft centrally inserted into the proximal and distal wedges. The translation and adjustment mechanism further comprises a first actuator and a second actuator, both of which are mounted on the central shaft and disposed at the same proximal end of the intervertebral cage.

Description

[Technical Field]

[0001] The present invention relates to an expandable intervertebral cage.

[0002] In particular, the implant objects of the present invention are used to treat spinal disorders requiring spacing of two adjacent vertebral bodies, such as in the case of a collapsed intervertebral disc, or to restore the correct curvature of the spine where a deformity exists that may cause an unnatural curvature of the spine, such as in the case of kyphosis or lordosis. [Background technology]

[0003] The prior art includes intravertebral surgical implants having a central body, called an intervertebral cage, adapted to be inserted into the intervertebral space using a special insertion tool.

[0004] These cages have an elongated shape and two bearing surfaces suitable for receiving vertebral bodies. When a patient requires correction of spinal curvature, cages are used with contact surfaces that can translate relative to each other or change their mutual inclination to allow for disc and intervertebral spacing while keeping the surfaces parallel.

[0005] Known and currently used expandable intervertebral cages allow the surgeon to space the bearing surfaces parallel to one another in the case of kyphosis or lordosis, or even to change the mutual inclination of the bearing surfaces, by acting on a suitable adjustment mechanism.

[0006] Thus, the surgeon can adjust the inclination of the resting surface to come as close as possible to the correction angle required to restore the correct curvature of the patient's spine.

[0007] However, known expandable intervertebral cages have the drawback that the adjustment mechanism on the surface itself is difficult to activate. Known types of expandable intervertebral cages offer the possibility of changing the inclination of the bearing surfaces by increasing the distance between the bearing surfaces only in the proximal or only in the distal position. This requires the actuation mechanism to be duplicated in both the proximal and distal positions, resulting in the proximal mechanism being more medial and therefore more difficult to reach. This requires the creation of a passageway inside the cage, which results in an increase in the implant dimensions that do not fit the anatomical dimensions of the intervertebral space, or a reduction in the thickness of the implant to limit its overall dimensions, which may lead to fragility or instability of the devices or instruments used for adjustment. This is the case, for example, with the intervertebral cage described in document US 10,285,824, in which the adjustment mechanisms are located in distal and proximal positions on a central hollow shaft through which the adjustment instruments are inserted. Because the diameter of the hole inside the central shaft is small to accommodate the overall dimensions of the cage, the diameter of the inserted instruments is even smaller, making it difficult to apply the torque required to overcome the resistance of the vertebrae compressing the cage plate, which must be long and thin to avoid risk of breaking the instruments themselves.

[0008] Other expandable intervertebral cages have structurally complex movement mechanisms for actuation, as described, for example, in document US6176882, while others are still designed to open by thrusts that entail stresses that do not guarantee optimal stability of the final position of the mounting surface and that can cause breakage or collapse of the cage, as, for example, in the device described in US10441430. Summary of the Invention

[0009] Therefore, the technical problem underlying the present invention is to propose an expandable intervertebral cage that is able to overcome the drawbacks encountered in the prior art.

[0010] In particular, the object of the present invention is to propose an expandable intervertebral cage that allows for the correction of intervertebral distances and / or spinal curvatures in an easy, simple and fast manner for the surgeon in order to restore the correct anatomical structure of the patient.

[0011] A further object of the invention is to propose an expandable intervertebral cage that is compact and rigid and allows the surgeon to use special adjustment tools that are able to overcome the resistance of the vertebrae on the plates of the cage without having to apply excessive force and without the risk of breaking the cage and the adjustment tools.

[0012] Finally, it is an object of the present invention to provide an expandable intervertebral cage that is structurally simple and allows for precise adjustment of the plates that contact the vertebrae.

[0013] These and other objects are achieved by an expandable intervertebral cage for spacing two vertebral bodies of the spinal column, as set forth in the accompanying claims. Summary of the Invention In particular, the present invention relates to an expandable intervertebral cage for spacing two vertebral bodies of the spinal column, comprising a first plate and a second plate facing opposite each other, both of which have an axially elongated planar structure along a central longitudinal axis extending from the proximal end to the distal end of the cage itself.

[0014] The first and second plates have respective inner surfaces facing each other and respective outer contact surfaces adapted to receive a corresponding vertebral body for placement thereon. The cage further comprises a movement and adjustment mechanism for the first and second plates adapted to facilitate relative translation of the first and second plates parallel to each other to vary the height of the cage to space two adjacent vertebral bodies, and rotation of one relative to the other about respective hinge axes disposed transversely to the central longitudinal axis of the cage and contained between the two plates to vary the relative inclination of the first and second plates to correct a spinal deformity. The moving and adjusting mechanism includes a single central shaft coaxial with the central longitudinal axis and having external threads, and proximal and distal wedges positioned between the first and second plates, aligned along the central longitudinal axis and coupled to the external threads of the central shaft, with the central shaft inserted centrally through and passing through the proximal and distal wedges. The moving and adjusting mechanism also includes first and second actuators, both mounted on the central shaft and located at the same proximal end of the cage.

[0015] The term proximal refers to the portion of the cage closest to the surgeon and facing the surgeon's body when the surgeon holds the cage before placing it inside the patient's body, and the term distal refers to the portion of the cage farthest from the surgeon and facing the patient's body.

[0016] A central shaft adapted to rotate about a central longitudinal axis has a single external thread having a single unidirectional winding direction extending over the entire outer surface of the central shaft.

[0017] The distal wedge includes a threaded portion adapted to be threaded onto the external threads of the central shaft.

[0018] The proximal wedge has an annular disc therein with a threaded portion that mates with the external threads on the central shaft.

[0019] An annular disc is housed inside the proximal wedge and rotates about the central shaft to facilitate translation of the proximal wedge along the central longitudinal axis.

[0020] The first actuator and the second actuator are operable to counter-rotate relative to one another about the central longitudinal axis.

[0021] The proximal and distal wedges are movable independently of one another and simultaneously depending on the relative positions between the first and second plates and the desired opening.

[0022] The first plate and the second plate each have two protruding portions protruding from their respective inner surfaces facing each other and directed toward the inside of the cage, the two protruding portions having inclined planes along which the proximal wedge and the distal wedge slide to facilitate translational and / or rotational movement of the first and second plates relative to each other.

[0023] The inclined planes of the two protruding portions converge towards the same central portion of the cage and together with the inclined planes of the opposing plates define respective V-shaped housings with apexes directed towards said central portion of the cage, within which the proximal and distal wedges slide.

[0024] The inclined surfaces of the distal and proximal wedges abut and slide against the inclined planes of the protruding portions of the two plates, so that following translation of the two wedges along the central longitudinal axis, the relative binding position between the inclined surfaces and the inclined planes changes, and therefore the relative positions of the two plates change.

[0025] The first actuator is adapted to rotate the central shaft to move the distal wedge and the proximal wedge.

[0026] The second actuator is adapted to move only the proximal wedge.

[0027] The first actuator is disposed at the proximal end of the central shaft.

[0028] The first actuator is defined by a polygonal housing formed axially on a central shaft for insertion of a grasping and actuation instrument.

[0029] The second actuator is disposed inside the proximal wedge.

[0030] The second actuator is an annular disk fitted to the central shaft. The annular disk has internal threads that mate with the external threads of the central shaft. The annular disk is housed inside the proximal wedge and is free to rotate by engaging with the external threads of the central shaft, thereby translating the proximal wedge toward the proximal end or central portion of the cage.

[0031] The annular disc has a gripping portion for engaging a gripping and actuating tool.

[0032] The cage also has a containment and connection structure adapted to house the moving and adjusting mechanism, the central shaft, the distal wedge, and the proximal wedge and to connect the first and second plates to one another, the containment structure being disposed at a peripheral location between the first and second plates.

[0033] There are also two pins, each of which is disposed across the central longitudinal axis and is housed between two plates.

[0034] Each pin connects a respective plate to the containment and connection structure.

[0035] The two protruding portions of each of the first and second plates have a respective eyelet at a central location that extends perpendicular to the central longitudinal axis and elongates toward the opposing plate.

[0036] Two pins are inserted into the slots to allow the first and second plates to move—that is, rotate relative to each other about their respective pins—away from and toward each other, translate parallel to each other, and tilt diverging or converging toward their distal ends. The pins remain in fixed positions while the plates translate thanks to the play provided by the elongated oval slots. [Brief explanation of the drawings]

[0037] The invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, which are given by way of example only. [Figure 1] FIG. 1 is a perspective view of an expandable intervertebral cage for spacing two vertebral bodies according to the present invention, the cage being in a fully closed, inoperative position and with parallel plates. [Figure 2] 2 shows a cross-sectional side view of the cage shown in FIG. 1. [Figure 3] 1 shows a perspective view of an intervertebral cage according to the invention in a first operating position with parallel spaced apart plates. [Figure 4] FIG. 4 shows a cross-sectional side view of the cage shown in FIG. 3. [Figure 5] 1 shows a perspective view of an intervertebral cage according to the invention in a second operating position with plates diverging in the distal direction. [Figure 6] FIG. 6 shows a cross-sectional side view of the cage shown in FIG. 5. [Figure 7] 1 shows a perspective view of an intervertebral cage according to the invention in a third operating position with plates diverging in the proximal direction. [Figure 8] FIG. 8 shows a cross-sectional side view of the cage shown in FIG. 7. [Figure 9] FIG. 2 shows a side view of the cage shown in FIG. 1. [Figure 10] FIG. 4 shows a perspective view of the cage of FIG. 3 with some parts removed to reveal the internal structure. [Figure 11]1 shows an exploded view of a cage object of the present invention. [Figure 12] 10 shows an alternative configuration of the cage object of the present invention with some parts removed to better view the internal structure. DETAILED DESCRIPTION OF THE INVENTION

[0038] In the accompanying drawings, 1 generally indicates an expandable intervertebral cage for spacing two vertebral bodies according to the invention.

[0039] This cage is placed between two adjacent vertebral bodies in cases of spinal disease, to space them out if they have collapsed, or to correct their angular position relative to one another, restoring the correct curvature of the spine.

[0040] 1, the expandable intervertebral cage according to the present invention comprises a first plate 2 and a second plate 3 opposite the first plate 2, both of which have planar structures and face each other. The first plate 2 and the second plate 3 have planar structures with elongated extensions primarily along the central longitudinal axis 1a of the cage 1, which extends from the proximal end 1p to the distal end 1d of the cage 1.

[0041] The two plates each comprise respective inner surfaces 2i and 3i facing each other and respective outer contact surfaces 2e, 3e suitable for receiving the corresponding vertebral body for seating.

[0042] These outer surfaces 2e and 3e are formed with pointed structures 22, e.g., pyramidal structures, that protrude towards the outside of the cage in order to improve their grip on the respective vertebral bodies to which they are attached.

[0043] The cage 1 also comprises a movement and adjustment mechanism 4 for the first plate 2 and the second plate 3, allowing for the mutual spacing and / or relative inclination to be varied. In particular, the movement and adjustment mechanism 4 is suitable for spacing the two plates 2 and 3 and translating them parallel to one another so as to vary the height of the cage 1, and for rotating the first plate 2 and the second plate 3 about respective hinge axes 1b disposed between the two plates and transverse to the central longitudinal axis 1a of the cage so as to vary the inclination of the two plates and therefore of the two external contact surfaces 2e, 3e to correct spinal deformities.

[0044] By adjusting the inclination of the two plates 2 and 3, they can be moved away towards the distal end 1d or the proximal end 1p of the cage 1 by a variable angle that can be determined arbitrarily, depending on the degree of correction to be given to the curvature of the spine.

[0045] The cage 1 can be configured in various ways depending on the relative positions of the two plates 2 and 3: a loaded configuration shown in Figures 1 and 2 in which the cage is fully closed and compact, with the two plates positioned close to and parallel to one another; a first operational configuration shown in Figures 3 and 4 in which the cage is expanded and the two plates positioned parallel to one another with a space between them; a second operational configuration shown in Figures 5 and 6 in which the cage 1 is at least partially expanded and the two plates are tilted at the same angle relative to the central longitudinal axis 1a so as to move apart toward the proximal end 1p of the cage 1; and a third operational configuration shown in Figures 7 and 8 in which the cage 1 is at least partially expanded and the two plates are tilted at the same angle relative to the central longitudinal axis 1a so as to move apart toward the distal end 1d of the cage 1. As noted above, the magnitude of the angle defined between each of the plates 2 and 3 and the central longitudinal axis 1a can be varied as desired by the surgeon depending on the surgical needs.

[0046] The moving and adjusting mechanism 4 comprises a single central shaft 5 coaxial with the central longitudinal axis 1a and having an external thread 5f formed on an outer surface 5s of the shaft 5. The external thread 5f is continuous and has a single unidirectional winding direction, extending over the entire outer surface 5s of the central shaft 5.

[0047] The central shaft 5 is adapted to rotate clockwise and counterclockwise about a central longitudinal axis 1a.

[0048] The moving and adjusting mechanism 4 further comprises a proximal wedge 6p and a distal wedge 6d disposed between the first plate 2 and the second plate 3. The proximal wedge 6p and the distal wedge 6d are aligned along the central longitudinal axis 1a and are coupled to the central shaft 5 in association with the external threads 5f of the central shaft 5.

[0049] As can be seen in the attached figure, the proximal wedge 6p and the distal wedge 6d each have two inclined surfaces 6'p and 6'd, each facing the respective plates 2 and 3. These inclined surfaces 6'p and 6'd lie on respective inclined planes, face the inner surfaces 2i and 3i of the plates and converge towards the central part 1m of the cage.

[0050] The distal wedge 6d and the proximal wedge 6p have a central through-housing 7 into which the central shaft 5 is inserted.

[0051] 11, the distal wedge 6d includes a threaded portion 6f adapted to be threaded onto the external threads 5f of the central shaft 5. The threaded portion 6f of the distal wedge 6d is formed in a surface that defines a housing 7 into which the central shaft 5 is inserted.

[0052] Meanwhile, the proximal wedge 6p has an internal annular disc 8 having a threaded portion 8f that mates with the external threads 5f of the central shaft 5. The annular disc 8 has a central circular cavity 9 disposed in the housing 7 of the proximal wedge 6p. The threaded portion 8f of the annular disc 8 is formed on a surface that defines said circular cavity 9.

[0053] An annular disc 8 is housed within and nested within the proximal wedge 6p and is rotatable about the central shaft 5 to facilitate translation of the proximal wedge 6p along the central longitudinal axis 1a. The movement of the proximal wedge 6p and the distal wedge 6d is described in more detail below.

[0054] The moving and adjusting mechanism 4 further comprises a first actuator 10 and a second actuator 11, both of which are provided on the central shaft 5 and arranged at the same proximal end 5p of the central shaft 5.

[0055] The first actuator 10 and the second actuator 11 are operable to counter-rotate relative to one another about the central longitudinal axis 1 a. The first actuator 10 and the second actuator 11 act on the central shaft 5, the distal wedge 6 d, and the proximal wedge 6 p to translate the proximal wedge 6 p and the distal wedge 6 d along the central longitudinal axis 1 a to facilitate translation and tilting of the plate.

[0056] In particular, the first actuator 10 is adapted to rotate the central shaft 5 to move the distal wedge 6d and the proximal wedge 6p, as will be explained below.

[0057] On the other hand, the second actuator 11 is suitable for moving only the proximal wedge 6p.

[0058] The proximal wedge 6p and the distal wedge 6d are actuatable and therefore movable independently and simultaneously depending on the relative position between the two plates and the desired opening. In other words, the two wedges are moved simultaneously or separately by the same pitch along the central shaft 5 depending on how far apart the two plates are desired to be parallel or how far the two plates are desired to be tilted.

[0059] The cage 1 further comprises a first pin 12 and a second pin 13, each of which is arranged transversely to the central longitudinal axis 1a and is housed between the first plate 2 and the second plate 3.

[0060] The first plate 2 and the second plate 3 rotate about respective hinge axes 2a, 3a which pass through pins 12, 13.

[0061] Plates 2 and 3 vary their inclination symmetrically with respect to a plane of symmetry X which passes through a central longitudinal axis 1 a disposed between and parallel to plates 2 and 3 when the cage is in the resting configuration or the first operating configuration.

[0062] In the resting or first operating configuration, the plane of symmetry X is equidistant from the two plates, whereas in the second and third operating configurations the two plates are inclined and lateral to the plane of symmetry X, each defining an angle with said plane of symmetry X having the same magnitude, which can be arbitrarily varied depending on the desired adjustments required at the surgical stage. The two plates 2, 3 are always axially symmetrical with respect to this plane of symmetry X.

[0063] In particular, the first pin 12 and the second pin 13, about which the first plate 2 and the second plate 3 respectively rotate, are orthogonal to the central longitudinal axis 1a and parallel to the plane of symmetry X.

[0064] Each pin 12 and 13 therefore has a respective longitudinal axis 12a and 13a perpendicular to the central longitudinal axis 1a and parallel to the plane of symmetry X, which each define a respective hinge axis 1b about which the first plate 2 and the second plate 3, respectively, rotate.

[0065] The first plate 2 and the second plate 3 each have two protruding portions 14 that protrude from their respective internal surfaces 2i and 3i facing each other and directed towards the inside of the cage 1. Each protruding portion 14, preferably two for each individual plate, is arranged along a respective long side of the first plate 2 and the second plate 3 and extends parallel to the central longitudinal axis 1a. The two protruding portions 14 of each individual plate are parallel to each other.

[0066] Each of these protruding portions 14 has two inclined planes 15 along which the proximal wedge 6p and the distal wedge 6d slide to facilitate the movement of the first plate 2 and the second plate 3.

[0067] These inclined planes 15 converge towards the central portion 1m of the cage 1 and, together with the inclined planes of the opposing plates, define respective V-shaped housings with apexes directed towards the central portion 1m. Each individual V-shaped housing houses a respective (proximal or distal) wedge slidably movable therein.

[0068] In particular, the inclined surfaces 6'p and 6'd of the proximal wedge 6p and the distal wedge 6d abut against and slide relative to the inclined planes 15 of the two plates. That is, by sliding the proximal wedge 6p and / or the distal wedge 6d along the central longitudinal axis 1a, the inclined surfaces 6'p and 6'd of the two wedges interact with the inclined planes 15 of the two plates by abutting against and changing their relative positions relative to them, and function as resting surfaces that accompany the closing of the plates (and thus the closing of the cage) when the wedges advance simultaneously or individually towards the central portion 1m of the cage (thus causing them to move apart from each other) or as resting surfaces that accompany the closing of the plates (thus causing the cage to close) when the wedges move simultaneously or individually away from the central portion 1m.

[0069] In an alternative embodiment shown in FIG. 12, the distal wedge 6d may have two rollers 20 on the inclined surface 6'd that facilitate surface sliding between the inclined surface 6'd and the inclined plane 15 and reduce friction therebetween.

[0070] The cage 1 further comprises a storage and connection structure 16 suitable for accommodating the moving and adjusting mechanism 4, the central longitudinal shaft 1a, the distal wedges 6d and the proximal wedges 6p therein. The storage and connection structure 16 is arranged between the first plate 2 and the second plate 3 at a peripheral position so as to laterally surround the cage on all four sides and is suitable for connecting the first plate 2 and the second plate 3 to each other. The first plate 2 and the second plate 3 remain outside the storage structure 16, above and below it.

[0071] The containment structure 16 has an opening 16a, such as a window, formed in the containment structure 16 itself at the proximal end 1p of the cage to allow access to the proximal end 5p of the central shaft 5 and the proximal wedge 6p.

[0072] The central shaft 5 is connected to the storage structure 16 by a ring 23, which blocks the distal end 5d of the central shaft 5 around which the ring 23 is arranged by interference inside a seat 24 formed in the storage structure 16.

[0073] The first pin 12 and the second pin 13 are arranged transversely to the central longitudinal axis 1a and are housed between the first plate 2 and the second plate 3 and extend between two protruding portions 14 of each respective plate.

[0074] Furthermore, each pin 12 , 13 connects the respective plate 2 , 3 to a containment and connection structure 16 .

[0075] The projecting portion 14 of each of the first and second plates 2, 3 has a respective central eyelet 17 extending perpendicular to the central longitudinal axis 1a and elongated towards the opposing plate.

[0076] The pins 12, 13 are inserted into these small holes 17 to allow the first plate 2 and the second plate 3 to move away from or towards each other.

[0077] The two pins 12, 13 remain in a fixed position, while the two plates 2 and 3 translate relative to these pins thanks to the play provided by the elongated oval slots.

[0078] The movement of the proximal wedge 6p and the distal wedge 6d is caused by a first actuator 10 and a second actuator 11, both of which are mounted on the central shaft 5 and located at the same proximal end 5p of the central shaft 5.

[0079] The first actuator 10 is disposed at the proximal end 5p of the central shaft 5. Specifically, as can be seen, for example, in Figures 1, 5 and 7, the first actuator 10 is defined by a polygonal housing 18 formed axially on the central shaft 5. The polygonal housing 18 is adapted to receive a grasping and actuation instrument by interference coupling.

[0080] On the other hand, the second actuator 11 is disposed inside the proximal wedge 6p. Specifically, the second actuator 11 is the above-mentioned annular disc 8. The annular disc 8 is fitted onto the central shaft 5 and has an internal thread 8f that mates with the external thread 5f of the central shaft 5, as described above.

[0081] The annular disc 8 has a gripping portion 19 suitable for receiving by coupling a gripping and actuation tool.

[0082] When in use, the plate positions are adjusted as follows:

[0083] Figures 1 and 2 show the cage object of the present invention in a non-operating configuration, with the distal wedge 6d and the proximal wedge 6p positioned at the distal end 5d and the proximal end 5p of the central shaft 5, respectively, and therefore positioned at a position where they are spaced apart from each other to the greatest extent and where the two plates are fully closed, parallel, and closest to each other.

[0084] Rotation of the central shaft 5 can be facilitated by inserting a gripping and actuating tool inside the polygonal housing 18 through the opening 16a of the storage structure 16. The gripping and actuating tool engages the polygonal housing 18, and rotating it in one direction, e.g., clockwise, rotates the central shaft 5 about the central longitudinal axis 1a. A single rotation of the central shaft 5, which has a single thread 5f with a single winding direction, translates the distal wedge 6d and the proximal wedge 6p toward the same end of the shaft itself, or toward the proximal end, or toward the distal end. In other words, rotating only the central shaft 5 activates simultaneous translation of the two wedges along the same direction by the same amount along the central longitudinal axis 1a.

[0085] Thus, if one wishes to open the cage by translating the first and second plates parallel to one another and away from one another, one must also act on the annular disc by applying a counter-rotation twice as large as that imposed on the central shaft, so as to move the two wedges in opposite directions and thus closer to the central portion 1m.

[0086] The distal wedge 6d engages directly with the threads 5f of the central shaft 5 and is therefore actuated directly and only by rotations imposed on the central shaft 5. Rotation of the shaft advances the distal wedge 6d by a pitch N.

[0087] On the other hand, the proximal wedge 6p does not directly engage the central shaft 5, and therefore, to advance the proximal wedge 6p in the direction opposite to the translation direction of the distal wedge, it is necessary to act on the annular disc 8. Using the same gripping and actuating instrument inserted into the polygonal housing 19 of the central shaft 5 to rotate the central shaft 5, the same gripping and actuating instrument simultaneously acts on the annular disc 8, rotating it in the direction opposite to the rotation imposed on the central shaft. The counter-rotation between the annular disc 8 and the central shaft 5 is necessary to translate the two wedges along the same axial direction, caused by the central longitudinal axis 1a, but in opposite directions. Specifically, to advance the proximal wedge 6p toward the central portion 1m by the same pitch N by which the distal wedge 6d was shifted, it is necessary to impart two rotations to the annular disc 8 in the direction opposite to the rotation imposed on the central shaft 5. In fact, a rotation imparted to the annular disc 8 in a counter-rotational direction relative to that of the central shaft 5 cancels the rotation of the central shaft 5 which causes a translation of the proximal wedge 6p in the same direction as the distal wedge moves, while a second rotation imposed on the annular disc 8 causes an effective translation of the annular disc 8, and therefore of the proximal wedge 6p, by a pitch N in the direction opposite to the direction of movement of the distal wedge. Thus, if it is desired to increase the height of the cage by moving the two plates apart, one acts via the first actuator 10 on the central shaft 5 by applying a certain number of rotations K which causes a translation of the distal wedge 6d by a certain number of pitches Nx towards the central portion 1m, and at the same time a double and opposite rotation (-2K) is applied to the annular disc 8 so that the proximal wedge translates by the same number of pitches Nx towards the central portion 1m.

[0088] The annular disc 8 is housed within the body of the proximal wedge 6p, as described above, and is free to rotate therein. The proximal wedge 6p has an opening 21 facing outward from the cage, through which the gripping portion 19 of the annular disc 8 is accessible.

[0089] Rotation of the annular disc 8 about the central shaft 5 causes its translation along the central longitudinal axis 1 a. That is, by shifting along the central longitudinal axis, the annular disc 8, which is encased inside the proximal wedge 6 p, causes the proximal wedge 6 p to translate axially.

[0090] By moving the wedges closer to the central portion 1m of the cage by the same number of pitches, the first plate 2 and the second plate 3 shift parallel to each other and away from each other relative to the central shaft 5, as shown in Figures 3 and 4. This occurs because, following axial translation towards the central portion 1m, sliding the wedges towards the apex of their respective V-shaped housings causes the inclined surfaces 6'p and 6'd of the distal and proximal wedges 6d, 6p to slide against the inclined plane 15, moving the two plates apart.

[0091] When it is desired to close the two plates, the exact opposite effect is achieved by shifting the wedges away from each other by the same number of pitches N, imparting to the central shaft 5 a rotation opposite to that previously imparted, and imparting to the annular disc 8 a rotation twice as long, always opposite to that now imparted to the central shaft 5. In this way, the wedges move away from each other and return to the initial positions of their distal and proximal ends 5d, 5p, bringing the plates 2 and 3 closer together.

[0092] As can be seen in Figures 5 and 6, when the cage is opened such that the plate slopes away from the proximal end 1p of the cage 1, the proximal wedge 6p will advance towards the central portion 1m.

[0093] To do this, assuming one wishes to open the cage away from the proximal end 1p starting from the inoperative configuration shown in Figure 1, the central shaft 5 must be held stationary and the annular disc 8 must be rotated to advance the proximal wedge 6p towards the central portion 1m.

[0094] Conversely, as can be seen in Figures 7 and 8, when opening the cage so that the plate slopes away from the distal end 1d of the cage 1, the distal wedge 6dp must be advanced towards the central portion 1m.

[0095] To do this, assuming one wishes to open the cage away towards the distal end 1d starting from the inoperative configuration shown in Figure 1, the central shaft 5 must be rotated in a direction that causes the distal wedge 6d to advance towards the central portion, and the annular disc 8 must be rotated in the opposite direction the same number of rotations as imposed on the central shaft 5. This is because in order to open the cage towards the distal end 1d, the proximal wedge 6p must remain stationary; i.e., this occurs when the rotation of the central shaft 5 is cancelled by the reverse rotation of the annular disc 8 the same number of rotations.

[0096] Considering that the distal wedge 6d is actuated only by the rotation of the central shaft 5 and that a rotation of the central shaft in one direction causes a translation of the distal wedge 6d by a pitch N towards the central portion 1m or towards the distal wedge 6d, while the shift of the proximal wedge 6p is caused by the rotation of the central shaft 5 and by the rotation of the annular disc 8 around the central shaft 5, depending on the starting positions of the wedges 6d and 6p and therefore where they are located along the central shaft 5, one or the other wedge must be shifted towards the central portion 1m of the cage and / or towards the distal end 1d and / or towards the proximal end 1p. Therefore, depending on whether the central shaft 5 is rotating or not, it needs to be evaluated whether the rotation of the shaft 5 must be cancelled out, keeping in mind the direction in which the proximal wedge is translated and by how many pitches it is shifted. In order to keep the distance between the two wedges constant, it is only necessary to act on the central shaft 5 when shifting the two wedges in the same direction, towards the distal end 1d or towards the proximal end 1p. In this case, it is not necessary to cancel the rotation of the central shaft 5 by the double reverse rotation of the annular disc 8.

[0097] If the proximal wedge 6p has reached the end of its stroke relative to the storage structure 16 but the distal wedge 6d needs to be further translated towards the central portion 1m, the annular disc 8 needs to be rotated in the opposite direction to the rotation imparted by the central shaft 5 with more rotations to cause the proximal wedge 6p to translate towards the central portion 1m, and then only the central shaft 5 needs to be rotated again to move the two wedges together again towards the proximal end 1p.

[0098] The present invention achieves its intended purpose in that the described cages are constructed to allow for quick, easy, and precise adjustment of the plate aperture and / or inclination to allow for correction of intervertebral spacing and / or spinal curvature to restore the patient's correct anatomy. The specific location of the actuators located at the same end allows the surgeon immediate access to the adjustment sites.

[0099] The double actuator ensures easy and instant adjustment of the position of the wedges and thus accurate and timely change of the distance between the plates and their mutual tilt.

[0100] A central shaft with a single thread with a single winding direction allows for quick assembly of the components and allows for the possibility of maximizing the dimensions of the threaded shaft compared to the rest of the cage. Conversely, with two threads, a mechanical stop is provided between the two threads to prevent the wedge, once it has reached the end of its stroke, from disengaging from the corresponding thread. Therefore, compared to the prior art, a single unidirectional thread requires less mechanical work (which stresses the shaft), greater resistance, less material removal, faster production speeds, and lower production costs.

[0101] Additionally, the described cages are compact and rigid, allowing the surgeon to use appropriate adjustment tools that can overcome the resistance offered by the vertebrae on the cage plates without having to apply excessive force and without risking damage to the cage and adjustment tools. This is achieved thanks to the location of the actuators, which are close to the surgeon, in a position that allows for a larger interface between the cage and the grasping and adjustment tools themselves. [Prior art documents] [Patent documents]

[0102] [Patent Document 1] US10285824 [Patent Document 2] US6176882 [Patent Document 3] US10441430

Claims

1. 1. An expandable intervertebral cage for spacing two vertebral bodies of a spinal column, comprising: A first plate (2) and a second plate (3) facing the first plate (2), Both the first plate (2) and the second plate (3) have an axially elongated planar structure along a central longitudinal axis (1a) extending from the proximal end (1p) to the distal end (1d) of the intervertebral cage (1); the first plate (2) and the second plate (3) have respective inner surfaces (2i, 3i) and respective outer contact surfaces (2e, 3e) facing each other, Each of said external contact surfaces (2e, 3e) is adapted to receive a corresponding vertebral body for placement thereon, and said intervertebral cage comprises: a movement and adjustment mechanism (4) for the first plate (2) and the second plate (3) adapted to facilitate a mutual translation of the first plate (2) and the second plate (3) parallel to each other so as to vary the height of the intervertebral cage (1) to space two adjacent vertebral bodies, and a rotation of one relative to the other about respective hinge axes (1b) accommodated between the first plate (2) and the second plate (3) and disposed transversely to the central longitudinal axis (1a) of the intervertebral cage so as to vary the mutual inclination of the first plate (2) and the second plate (3) to correct a deformity of the spine; The moving and adjusting mechanism (4) comprises: a single central shaft (5) coaxial with said central longitudinal axis (1a) and having an external thread (5f); a proximal wedge (6p) and a distal wedge (6d) disposed between the first plate (2) and the second plate (3), the proximal wedge (6p) and the distal wedge (6d) being aligned along the central longitudinal axis (1a) and coupled to the male thread (5f) of the central shaft (5) inserted into the center of the proximal wedge (6p) and the distal wedge (6d); The moving and adjusting mechanism (4) further comprises a first actuator (10) and a second actuator (11), both of which are provided on the central shaft (5) and located at the same proximal end (1p) of the intervertebral cage (1); the central shaft (5) adapted to rotate about the central longitudinal axis (1a) has a single external thread (5f) having a single unidirectional winding direction extending over the entire outer surface (5s) of the central shaft (5); The proximal wedge (6p) has an annular disc (8) therein having a threaded portion (8f) that engages with the external thread (5f) of the central shaft (5f); The annular disc (8) is housed inside the proximal wedge (6p) and rotates around the central shaft (5) to facilitate translation of the proximal wedge (6p) along the central longitudinal axis (1a).

2. The expandable intervertebral cage according to claim 1, wherein the distal wedge (6d) comprises a threaded portion (6f) suitable for being screwed onto the external thread (5f) of the central shaft (5).

3. 3. The expandable intervertebral cage of claim 1 or 2, wherein the first actuator (10) and the second actuator (11) are operable to counter-rotate about the central longitudinal axis (1a).

4. 3. The expandable intervertebral cage according to claim 1 or 2, wherein the proximal wedge (6p) and the distal wedge (6d) are movable independently and simultaneously depending on the relative position between the first plate (2) and the second plate (3) and the desired opening.

5. 3. The expandable intervertebral cage according to claim 1, wherein the first plate (2) and the second plate (3) each have two protruding portions (14) protruding from the respective inner surfaces (2i, 3i) facing each other and directed towards the inside of the intervertebral cage (1), the protruding portions (14) having inclined planes (15) along which the proximal wedge (6p) and the distal wedge (6d) slide to facilitate mutual translational and / or rotational movement of the first plate (2) and the second plate (3).

6. 6. The expandable intervertebral cage according to claim 5, wherein the inclined planes (15) converge towards the same central portion (1m) of the intervertebral cage (1) and together with the inclined surfaces (6'd, 6'P) of the opposing plates define respective V-shaped housings with apexes directed towards the central portion (1m) of the intervertebral cage (1), within which the proximal wedges (6p) and the distal wedges (6d) slide.

7. 3. The expandable intervertebral cage according to claim 1 or 2, wherein the first actuator (10) is adapted to rotate the central shaft (5) and move the distal wedge (6d) and the proximal wedge (6p).

8. The expandable intervertebral cage according to claim 1 or 2, wherein the second actuator (11) is adapted to move the proximal wedge (6p).

9. The expandable intervertebral cage according to claim 1 or 2, wherein the first actuator (10) is arranged at the proximal end of the central shaft (5).

10. 10. The expandable intervertebral cage of claim 9, wherein the first actuator (10) is defined by a polygonal housing (18) formed axially on the central shaft (5) for inserting a grasping and actuation instrument.

11. The expandable intervertebral cage according to claim 1 or 2, wherein the second actuator (11) is arranged inside the proximal wedge (6p).

12. 3. The expandable intervertebral cage according to claim 1, wherein the second actuator (11) is the annular disc (8) fitted onto the central shaft (5), the annular disc (8) having an internal thread (8f) that mates with the external thread (5f) of the central shaft (5).

13. 13. The expandable intervertebral cage according to claim 12, wherein the annular disc (8) is freely rotatable by being completely housed within the proximal wedge (6p) and engaging with the external thread (5f) of the central shaft (5), thereby translating the proximal wedge towards the proximal end (1p) of the intervertebral cage (1) or towards the same central part (1m) of the intervertebral cage (1).

14. 2. The expandable intervertebral cage of claim 1, wherein the annular disc (8) has a gripping portion (19) for engaging with a gripping and actuation tool.

15. 3. The expandable intervertebral cage according to claim 1, wherein the expandable intervertebral cage comprises a storage and connection structure (16) adapted to house the moving and adjusting mechanism (4), the central shaft (5), the distal wedges (6d) and the proximal wedges (6p) therein and to connect the first plate (2) and the second plate (3) to each other, the storage and connection structure (16) being disposed at a peripheral position between the first plate (2) and the second plate (3).

16. 3. The expandable intervertebral cage according to claim 1 or 2, wherein the expandable intervertebral cage comprises two pins (12, 13), each of which is arranged transversely to the central longitudinal axis (1 a) and is housed between the first plate (2) and the second plate (3).

17. The expandable intervertebral cage comprises two pins (12, 13), each of which is disposed transversely to the central longitudinal axis (1 a) and is housed between the first plate (2) and the second plate (3); 16. The expandable intervertebral cage according to claim 15, wherein each pin (12, 13) connects a respective one of said plates (2, 3) to said containment and connection structure (16).

18. 6. The expandable intervertebral cage according to claim 5, wherein the protruding portions (14) of the first plate (2) and the second plate (3) each have a respective eyelet (17) in the center extending perpendicular to the central longitudinal axis (1 a) and towards the opposing plate.

19. The expandable intervertebral cage comprises two pins (12, 13), each of which is disposed transversely to the central longitudinal axis (1 a) and is housed between the first plate (2) and the second plate (3); 19. The expandable intervertebral cage of claim 18, wherein the pins (12, 13) are inserted into the eyelets (17) to allow the first plate (2) and the second plate (3) to translate parallel to each other, moving away from and towards each other, and rotate relative to each other about their respective pins (12, 13) to tilt away from or converge towards the distal end (1d).

Images