Inter-somatic cage for vertebral fusion

Abstract

A cage (1) for vertebral interbody fusion is described, to be positioned in place of an intervertebral disc with the aim of stabilising two adjacent vertebral bodies and creating a "bone callus", wherein the cage (1) changes its configuration to restore the correct intervertebral distance and to stabilize the cage (1) in the position in which it was inserted; the cage (1) comprises: a pair of wings (3, 3a), hinged so as to be able to assume a first closed configuration and a second open configuration; a central element (4) in which an axial nut screw (5) is made, a pair of threaded holes (7, 7a) perpendicular to the axis (6), a pair of longitudinal guides (8, 8a) and a circumferential guide (8b); a pair of pins (9, 9a), which are screwed into the threaded holes (7, 7a) and which, being inserted completely into holes (10, 10a) made in the wings (3, 3a), act as the rotation axis of the wings (3, 3a).

Description

[0001] INTER-SOMATIC CAGE FOR VERTEBRAL FUSION

[0002] The present invention refers to a device, called cage for vertebral interbody fusion, which is designed to be positioned in place of an intervertebral disc with the aim of stabilizing the two adjacent vertebral bodies and creating a "bone callus" which causes the two vertebral bodies to fuse together.

[0003] Inter- somatic cages are used in cases of severe degeneration of the intervertebral discs of the lumbar tract, especially if there are situations of stenosis of the spinal canal and / or of the intervertebral foramina with chronic painful symptoms.

[0004] In these cases, restoring the height of the disc and subsequent fusion can allow decompression of the nerve structures, and therefore lead to improvement or resolution of symptoms.

[0005] In essence, these cages are small, of different shapes, sizes and materials, and are inserted into the spaces between two vertebral bodies, those originally occupied by the intervertebral discs that have undergone degeneration. The cages have a three- dimensional shape that resembles spongy bone for complete integration with the vertebral bodies. In fact, the main purpose of the inter-somatic cages is maintaining the correct distance between the vertebrae, so as to maintain a good height of the neuroforamina through which the spinal roots emerge, and to obtain bone growth inside them and create a complete "fusion" between the bones of the two adjacent vertebral bodies, favoring the blocking of the affected section of the spinal column.

[0006] In addition to cages of predefined sizes and shapes, there are cages that, once inserted, can be expanded to help restore the disc space, thus reducing surgical risks.

[0007] W02016144150A1 describes a system for interbody fusion with mechanisms to prevent unwanted lateral movements between its components. The system comprises an expandable cage containing two platforms between which there are windows that are raised by means of a clip to calibrate the expansion, the cage being placed in the intervertebral space by means of fastening means comprising a threaded guide and a series of hollow rods that allow complete control of the cage movements.

[0008] W02008155472A1 describes an inter-somatic cage of the implant type, for the fusion of vertebral bodies by means of a trans foraminal approach, wherein said implant comprises a body with a curved profile suitable for being implanted between the vertebral plates of two ad acent vertebrae. According to the invention, said body with a curved profile comprises a rear driving part and a front attachment part, the latter being composed of a lower tab and an upper tab suitable for receiving between them a spacer element which can slide between an introduction position and a spacing position, thus increasing the thickness by spreading the fins, said spacer element comprising a receiving seat open at the top and bottom.

[0009] Cage systems to be used for the transforaminal mono-portal approach, that is with access only from one side, do not allow good primary stability of the vertebral segment because, in order to introduce them, they are of suboptimal dimensions, with a small area, not sufficient to mechanically stabilize the treated vertebral level, and therefore cannot be used in a standalone way, that is without having to perform a second posterior stabilization procedure with screws and rods, due to the risk that the cage moves in the days following its positioning, goes to compress the nervous structures, or is small and / or unstable so as not to be able to determine a rapid formation of the inter-somatic bone callus. Furthermore, they are not suitable for correcting a scoliosis in the coronal or sagittal direction at the treated level.

[0010] US 2021 / 030561 Al describes a vertebral interbody fusion cage according to the preamble of Claim 1.

[0011] Object of the present invention is solving at least in part the aforementioned prior art problems.

[0012] The above and other objects and advantages of the invention, as will become apparent from the following description, are achieved with a device such as that described in claim 1. This device, called a cage for interbody vertebral fusion, is designed to be positioned in place of an intervertebral disc with the aim of stabilizing the two adjacent vertebral bodies and creating a "bone callus" that causes the two vertebral bodies to fuse together. This cage is of the type that can re-expand the intervertebral space in multiple subsequent ways: it is introduced in its smallest dimension, then, by rotating it 90°, it re-expands the height of the disc by the millimeters chosen by the operator, choosing the size of the wings, and furthermore, after being introduced into the intervertebral disc space, it changes its configuration, significantly increasing the area between the wings, to restore the correct intervertebral distance and to stabilize itself in the position in which it was inserted.

[0013] This cage is characterized in that it includes: a pair of wings, hinged so as to be able to assume a first closed configuration and a second open configuration, on which a plurality of teeth are obtained; furthermore, each of the wings can be chosen with rectangular dimensions, lordotic or kyphotic, so as to correct mono-segmental scoliosis both in the coronal and sagittal direction; a substantially cylindrical central element, in which an axial nut is made, a pair of threaded holes perpendicular to the axis of said cylindrical element, a pair of longitudinal guides and a circumferential guide; a pair of pins which screw into said threaded holes and which act as the rotation axis of said toothed wings; an ellipsoidal cage provided with a pair of teeth, suitable for inserting into said longitudinal and circumferential guides of said central element, a plurality of anchoring slats and a pair of longitudinal guides .

[0014] Preferred embodiments and non-trivial variants of the present invention form the subject matter of the dependent claims.

[0015] It is understood that all attached claims form an integral part of this description.

[0016] The cage according to the invention has significant advantages over prior art devices. These advantages will become more evident as the description continues.

[0017] First of all, there are operational advantages as a tool kit is provided which makes positioning easy at the inter-somatic level, making the operation minimally invasive. This kit allows the cage to be inserted from one side only and ensures adequate stability and bilateral housing. Furthermore, the cage is easily removable in the event of incorrect positioning or the need for removal. Furthermore, it has excellent primary stability right from insertion and effectively promotes bone fusion, reducing the risk of subsidence or dislocation.

[0018] It will be immediately obvious that countless variations and modifications can be made to what is described (for example relating to shape, dimensions, arrangements and parts with equivalent functionality) without departing from the scope of the invention as appears from the attached claims.

[0019] The present invention will be better described by a preferred embodiment, provided by way of example and not limitation, with reference to the attached drawings, in which:

[0020] FIG. 1 to 4 show an example of embodiment of the cage according to the present invention;

[0021] FIG. 5 to 7 show instruments used to introduce the cage into its place, between two consecutive vertebrae;

[0022] FIGS. 8 to 10 show the sequence of configurations that the cage according to the invention assumes during introduction into its seat;

[0023] FIG. 11 shows the complete cage in its final configuration .

[0024] Referring to FIG. 1, (1) indicates an inter- somatic cage for vertebral fusion according to the present invention.

[0025] This cage (1) is designed to be inserted between two consecutive vertebrae of a spinal column, to restore the intervertebral distance following damage to the relative disc, due to trauma and / or disease.

[0026] The cage (1) is shown in a closed configuration in FIG. la, as it appears before the introduction in place of an intervertebral disc, and in an open configuration, in FIG. lb, as it appears after the introduction between two consecutive vertebrae.

[0027] In FIG. 2a the cage (1) is shown is inserted between two consecutive vertebrae of the lumbar region. The cage (1) is made to have a thickness such that, when inserted by force between the two consecutive vertebrae, it restores the correct intervertebral space. In practice, the cage is inserted from the side of minimum thickness, then rotated by 90°, thus creating an adequate disc space, without disturbing the nerve roots and the dural sac.

[0028] In particular, in FIG. 2b the cage (1) , in the closed configuration, is shown being inserted through a hole (2) to access the disc space, subsequently the cage (1) is opened (FIG. 1c) and is firmly locked between the vertebrae, restoring their distance.

[0029] This cage (1) includes: a pair of wings (3, 3a) , hinged along an axis (3b) , on which a plurality of teeth (la) are preferably obtained; a central element (4) (FIG. 3) , substantially cylindrical, in which an axial nut (5) is made, with axis (6) , a pair of threaded holes (7, 7a) perpendicular to said axis (6) , a pair of longitudinal guides (8, 8a) and a circumferential guide (8b) ; a pair of pins (9, 9a) , which are screwed into the threaded holes (7, 7a) and which, by inserting themselves into the holes (10, 10a) of the toothed wings (3, 3a) , act as the rotation axis of said toothed wings (3, 3a) ; an ellipsoid cage (11) , shown in two views in FIG. 4 (a, b) , provided with a pair of teeth (12) , suitable for inserting into said longitudinal guides (8, 8a) and circumferential (8b) of said central element (4) , a plurality of anchoring slats (13) and a pair of longitudinal guides (14) .

[0030] For the insertion of the cage (1) between the vertebrae, the invention provides for the use of a specific kit of tools which includes : a first introducer instrument (20) , (FIG. 5a) essentially consisting of a cylindrical rod having a threaded end (21) , said thread being suitable for being screwed into the axial nut (5) of the central element (4) ; a second introducer instrument (22) , (FIG. 5b) comprising a tubular rod into whose axial hole (23) said first introducer instrument (20) is inserted, said second introducer instrument (22) being provided at one end with a closing element (24) for the toothed wings (3, 3a) of the cage (1) , the function of which will be specified below; a third introducer instrument (25) , (FIG. 6) comprising a tubular rod into the hole (26) of which said first introducer instrument (20) is inserted, said third introducer instrument (25) being provided, at one end, with a flat part with rounded edges (27) , the function of which will be described below; a fourth introducer instrument (30) , shown in two views rotated by 90° around its longitudinal axis in FIGS. 7 (a, b) , one of the two ends of said fourth introducer instrument (30) being shaped so as to fit into the guides (14) of the ellipsoid cage (11) •

[0031] The introduction of the cage (1) between the vertebrae involves the following steps, provided to facilitate understanding of the invention:

[0032] Step 1 - starting from the cage (1) assembled as shown in FIG. la, the first introducer instrument (2) is screwed into the nut (5) of the central element (4) (FIG. 8a) ;

[0033] Step 2 - the second introducer instrument (22) is inserted onto the first introducer instrument (20) taking care that the closing element (24) keeps the toothed wings (3, 3a) closed;

[0034] Step 3 - the cage (1) is inserted into the disc space (FIG. 2b) ;

[0035] Step 4 - the second introducer instrument (22) is extracted and replaced with the third introducer instrument (25) , inserting the flat part (27) between the toothed wings (3, 3a) of the cage (1) (FIG.9a) ;

[0036] Step 5 - the third introducer instrument (25) is rotated 90° around its axis, consequently obtaining the opening of the toothed wings (3, 3a) (FIG. 9b) ;

[0037] Step 6 - the third introducer instrument (25) is extracted and in its place the fourth introducer instrument (30) is introduced with the ellipsoidal cage (11) applied, which is inserted onto the central element (4) by sliding the teeth (12) of the ellipsoidal cage (11) into the straight guides (8, 8a) obtained on the cylindrical body (4) (FIG. 10a) ;

[0038] Step 7 - the fourth introducer instrument (30) is rotated 90° around its longitudinal axis, sliding the teeth (12) of the ellipsoidal cage (11) into the circumferential guide (8b) of the central element (4) , said ellipsoid cage (11) , locking itself between the intervertebral plates (3, 3a) by engaging the anchoring slats (13) against the surface of the inter-somatic plates (3, 3a) (FIG. 10b) ;

[0039] Step 8 - the fourth introducing instrument (30) is extracted, leaving the cage (1) , with the toothed wings (3,3a) open in the disc space in which it was inserted (FIG. 11) , remaining blocked by the combined effect of the pressure exerted by the vertebrae on the cage (1) itself and of the teeth (la) .

[0040] After an adequate amount of time, a callus forms inside the cage (1) and the two vertebrae are fused together.

[0041] According to a preferred embodiment, the cage (1) and the ellipsoidal cage are made of PEEK (Poly Ether Ether Ketone) carbon fiber composite coated in titanium or tantalum, or in ceramic material (for example zirconium oxide) .

Claims

CLAIMS1. Cage (1) for intervertebral fusion, suitable for being positioned in place of an intervertebral disc with the aim of stabilising the two adjacent vertebral bodies and creating a "bone callus", which causes the said two vertebral bodies to fuse together, of a type which, after being introduced into the intervertebral disc space, changes its configuration to restore the correct intervertebral distance and to stabilize said cage (1) in the position in which it was inserted, said cage (1) comprising: a pair of wings (3, 3a) , hinged so that they can assume a first closed configuration and a second open configuration; a central element (4) , substantially cylindrical, in which an axial nut (5) is made, which is arranged along the longitudinal axis (6) of said central element (4) , a pair of threaded holes (7, 7a) perpendicular to said axis (6) , a pair of longitudinal guides (8, 8a) and a circumferential guide (8b) ; a pair of pins (9, 9a) , which are screwed into the threaded holes (7, 7a) and which, being inserted completely into holes (10, 10a) obtained in the wings (3, 3a) , act as the rotation axis of said wings (3, 3a) , characterized in that it further comprises an ellipsoid cage (11) , provided with a pair of teeth (12) , suitable for inserting into said longitudinal guides (8, 8a) and said circumferentialguide (8b) of said central element (4) , a plurality of anchoring slats (13) and a pair of longitudinal guides (14) .

2. Cage (1) for vertebral interbody fusion according to claim 1, characterized in that a plurality of teeth (la) are formed on said wings ( 3 , 3a ) .

3. Kit comprising the cage (1) for vertebral interbody fusion according to claim 1, and at least one introducer instrument (20, 22, 25, 30) suitable for inserting the cage (1) between the vertebrae .

4. Kit according to claim 3, characterized in that it includes a first introducer instrument (20) , essentially consisting of a cylindrical rod having a threaded end (21) , said thread being suitable for being screwed into the axial nut (5) of the central element ( 4 ) .

5. Kit according to claim 3, characterized in that it includes a second introducer instrument (22) , comprising a tubular rod in whose axial hole (23) said first introducer instrument (20) is inserted and provided at one end with a closing element (24) of the wings (3, 3a) of the cage (1) .

6. Kit according to claim 3, characterized in that it includes a third introducer instrument (25) , comprising a tubular rod into the hole (26) of which said first introducer instrument (20) is inserted, said third introducer instrument (25) being provided, at one end, with a flat part with rounded edges (27) .. Kit according to claim 3, characterized in that it includes a fourth introducer instrument (30) , one of the two ends of said fourth introducer instrument (30) being shaped so as to fit into the guides (14) of said ellipsoidal cage (11) .

8. Cage (1) for vertebral interbody fusion or kit according to claims 1 to 7, characterized in that it is made of PEEK, Poly Ether Ether Ketone, carbon fiber composite coated in titanium or tantalum, or in ceramic material, namely zirconium oxide.

9. Method for operating the cage (1) for interbody fusion vertebral kit according to claims 1 to 8 , characterised in that the introduction of said cage (1) between two consecutive vertebrae comprises the following steps:Step 1 - starting from the assembled cage (1) , the first introducer instrument (2) is screwed into the nut (5) of the central element (4) (FIG. 8a) ;Step 2 - the second introducer instrument (22) is inserted onto the first introducer instrument (20) taking care that the closing element (24) keeps the wings (3, 3a) closed;Step 3 - the cage (1) is inserted into the disc space;Step 4 - the second introducer instrument (22) is extracted and replaced with the third introducer instrument (25) , inserting the flat part (27) between the wings (3, 3a) of the cage (1) ;Step 5 - the third introducing instrument (25) is rotated 90° around its axis, consequently obtaining the opening of thewings ( 3 , 3a ) .

10. Method according to claim 9, characterised in that the introduction of said cage (1) between two consecutive vertebrae further comprises the following steps:Step 6 - the third introducer instrument (25) is extracted and in its place the fourth introducer instrument (30) is introduced with the ellipsoidal cage (11) applied, which is inserted onto the central element (4) by sliding the teeth (12) of the ellipsoidal cage (11) into the straight guides (8, 8a) obtained on the cylindrical body (4) ;Step 7 - the fourth introducer instrument (30) is rotated 90° around its longitudinal axis, sliding the teeth (12) of the ellipsoidal cage (11) into the circumferential guide (8b) of the central element (4) , said ellipsoid cage (11) , locking itself between the wings (3, 3a) of the cage (1) by engaging the anchoring slats (13) against the surface of the intervertebral plates so as to determine primary stability;Step 8 - the fourth introducer instrument (30) is extracted, leaving the cage (1) , with the wings (3,3a) open in the disc space in which it was inserted, remaining blocked by the pressure exerted on the cage (1) itself by the adjacent vertebrae.

10. Cage (1) for vertebral interbody fusion or kit according to claims 1 to 7, characterized in that it is made of PEEK, Poly Ether Ether Ketone, carbon fiber composite coated in titanium ortantalum, or in ceramic material, namely zirconium oxide.

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