CAGE

The present invention relates to the field of medical devices, and more particularly to an assembly comprising a delivery system and an interbody cage.

Certain pathologies of the human spine, such as degenerated discs, facettes diseases, and dislocation of vertebrae, compromise the support capacity of the column and the sharing of the load.

The treatment of such pathologies in their advanced stages is achieved by various stabilization systems with intra-discal implants such as interbody cages, whether or not coupled with extra-discal systems, which combine the use of vertebral screws and plates or rods. Such intra-discal implants have significantly improved the treatment of pathologies of the human spine, in restoring the intervertebral space, which results in the decompression of the nerve roots and the acceleration of bony fusion of the adjacent vertebrae together. Impactation cages represent an important category among interbody cages. These cages, which have a substantially parallelepiped shape, are inserted between the vertebrae by impactation. The downside of these cages is the difficulty of their insertion into the intervertebral space, notably through posterior or unilateral approaches notably transforaminal, lateral, oblique or anterio lateral, but also for anterior cages. The crenellations and dents which are integrated on the superior and inferior surfaces of the cage for the purpose of anchoring the cage into the vertebral plates to prevent its migration, once it is in its final position, represent an additional obstacle to its insertion.

WO 2009092960 describes a cage with a delivery system comprising of two retractable rods, said rods, when fully assembled with the cage, are not protruding from the superior and inferior surfaces of the cage, at their highest distance apart.

US 9,289,314 discloses an interbody cage comprising a cage with rods protruding from some of its surfaces, which rods are retractable or fully removable from the cage.

US 201 1 /0071637 discloses an assembly of a cage and delivery system, where the delivery system has elongated members covering at least three surfaces of a cage and are arranged with a flange which engages in grooves arranged on the superior and inferior surfaces of the cage.

The purpose of the present invention is to provide an assembly comprising an interbody cage and a delivery system for inserting the interbody cage between two vertebrae, wherein the delivery system comprises two opposing rods positioned within two opposing grooves of compatible volumes arranged on the superior and inferior surfaces of the interbody cage, which rods protect the two vertebrae of a vertebral segment from the crenellated surfaces of the interbody cage when said interbody cage is inserted in the intervertebral space by means of the delivery system.

The characteristics of the invention will appear more clearly from the description of various embodiments, which are solely provided as examples and are not limitative, and in which references will notably be made to the horizontal plane of the cage which will be assumed to be in a parallel plane to the plane of the adjoining vertebral bodies, and to the vertical plane of the cage which is the plane perpendicular to the horizontal plane. In addition, the anterior side of the delivery system or the cage designates that side which is adjusted against the vertebrae just before the introduction of said delivery system in that space, and the posterior side of the delivery system or the cage means the side opposite to the anterior side. The description of these various embodiments refers to the attached schematic Figures in which: Figure 1 represents a perspective view of the delivery system according to the first embodiment.

Figure 2 represents a front view of the same delivery system as in Figure 1 .

Figure 3 represents a lateral view of the same delivery system as in Figures 1 and 2, with an added mobile push rod.

Figure 4 represents a perspective view of the cage according to the first embodiment with grooves on its superior and inferior surfaces.

Figure 5 represents a front view of the same cage as in Figure 4.

Figure 6 represents a perspective view of an assembly of the fully engaged delivery system and cage of the first embodiment.

Figure 7 represents a perspective view of the assembly of Figure 6 with a partly disengaged delivery system and cage.

Figure 8a represents a lateral view of two schematic sections of two vertebral bodies and of a delivery system fully assembled with a cage, with its anterior part being introduced between the two vertebrae.

Figure 8b represents a lateral view of the same assembly as in Figure 8a with the delivery system and cage mostly engaged between two vertebrae.

Figure 8c represents a lateral view of the same assembly as in Figures 8a and 8b with the delivery system being retracted from the cage and from the intervertebral space.

Figure 8d represents a lateral view of the cage and two vertebrae as in Figures 8a to 8c without the delivery system.

Figure 9a represents a perspective view of an assembly of a cage with rectangular cross-sectioned grooves, fully engaged with the delivery system.

Figure 9b represents a perspective view of the assembly of Figure 9a with a partially disengaged delivery system and cage.

Figure 10a represents a perspective view of a cage with triangular cross- sectioned grooves. - Figure 10b represents a perspective view of a cage with inversed triangular cross-sectioned grooves.

- Figure 1 1 a represents a front view of a cage with two round cross- sectioned grooves positioned diagonally.

- Figure 1 1 b represents a front view of a cage with two square cross- sectioned grooves positioned in a plane ex-centered from the central longitudinal axis of the cage.

- Figure 1 1 c represents a front view of a cage with two square cross- sectioned grooves arranged on the superior surface and one rectangular groove positioned on the inferior surface.

- Figure 12a represents a perspective view of an assembly of the second embodiment with a broad grooved cage fully engaged with a delivery system with round cross-sectioned shielding rods.

- Figure 12b represents a perspective view of the same assembly as in Figure 1 2a but with a partly disengaged delivery system.

- Figure 13 represents a front view of the assembly of the second embodiment represented in Figure 12a.

- Figure 14 represents a lateral view of the assembly of the second embodiment represented in Figure 12a.

- Figure 15a represents a perspective view of an assembly of the third embodiment with a crescent-shaped cage fully assembled with a delivery system with two opposing rectangular cross-sectioned shielding rods comprising curved rims on their outer sides.

- Figure 15b represents a perspective view of the same assembly as in Figure 15a but with a partly disengaged delivery system.

- Figure 16 represents a top view of the fully assembled delivery system and cage of the third embodiment.

- Figure 17 is a blown-up representation of the cross-section of one shielding rod of the delivery system in Figure 16 arranged with a curved rim on its outer side.

- Figure 18a represents a perspective view of an assembly of the fourth embodiment with a crescent-shaped cage fully assembled with a delivery system with two opposing flexible shielding rods engaged in two curved grooves.

- Figure 18b represents a perspective view of the assembly in Figure 18a with a partially disengaged delivery system from the cage.

- Figure 19 represents a perspective view of a delivery system with two opposing curved and flexible shielding rods.

Figures 1 , 2 and 3 describe the delivery system 1 of the first embodiment of the invention comprising two opposing shielding rods 2a, 2b, which have a half-moon shaped cross-section, with each shielding rod having a distal end 3a, 3b and a proximal end 4a, 4b. The shielding rods 2a, 2b are arranged in two parallel axes and have a curved outer side 5a, 5b and a flat inner side 6a, 6b. The distal ends 3a, 3b of the shielding rods 2a, 2b are beveled in inclined planes P, P' extending from the flat inner sides 6a, 6b at the distal ends 3a, 3b of the shielding rods to their curved outer sides 5a, 5b. The proximal ends 4a, 4b of the shielding rods 2a, 2b are connected to the anterior side 8 of a connecting member 7. The delivery system 1 also comprises a cannulated rod 10 connected at one of its ends to the posterior side 9 of the connecting member 7 and at its other end to a handle. The connecting member 7 may have two teeth 13a, 13b to engage with an interbody cage 14. The connecting member 7 may have a bore 1 1 to allow the pass-through and forward / backwards motions of a mobile push rod 1 2, which has a smaller diameter than the inner cylindrical cavity of the cannulated rod 10, and which may be arranged through the full length of the cannulated rod and through the bore 1 1 of the connecting member 7. The mobile rod 1 2 may be connected at its proximal end to a second handle of the delivery system 1 . The distal end of the mobile rod 12 may be threaded and may be connected with the posterior part 19 of the interbody cage 14 to be implanted between one superior and one inferior vertebra 24a, 24b. According to Figure 2, the distance between the outer sides 5a, 5b of the shielding rods 2a, 2b defines the dimension D. In a variation of the delivery system 1 , the two shielding rods 2a, 2b may be arranged in one single "U shaped" member like a diapason. In such a variation, the connecting member 7 may have a similar cross-section as the rods 2a, 2b but in a bended configuration, and may be arranged with the other features of the connecting member 7, such as the bore 1 1 and the teeth 13a, 13b.

Figures 4 and 5 describe a cage 14 suitable to be delivered in the intervertebral space with the delivery system 1 . The cage 14 has superior and inferior surfaces 15a, 15b which are partly covered with crenellations 16a, 1 6b, two lateral sides 17a, 17b, an anterior part 18 and a posterior part 19. The cage 14 may also have a cavity 20 between its superior and inferior surfaces 15a, 15b to allow bone ingrowth, and two indentations 21 a, 21 b arranged on the posterior part 19 of the cage 14 to engage with the teeth 13a, 13b of the connecting member 7 of the delivery system 1 . The cage 14 has a bore 22 in its posterior part 19 which may engage with the tip of the mobile push rod 12 of the delivery system 1 . Two sections of grooves 23a, 23a', 23b, 23b' are arranged on the superior and inferior surfaces 15a, 15b of the cage 14 on the anterior and posterior sides of the cavity 20, said grooves 23a, 23a', 23b, 23b' having a shape compatible with the cross-section of the shielding rods 2a, 2b of the delivery system 1 . The lateral sides of the grooves 23a, 23b arranged on the anterior part 18 of the cage are beveled in the plane along the wedge-shaped surfaces of said anterior part 18 in order to receive the beveled distal ends 3a, 3b of the shielding rods 2a, 2b. As the superior and inferior surfaces 15a, 15b of the cage 14 are not arranged in parallel planes, but arranged in two planes angled relative to each other and converging towards the posterior part 19 of the cage 14, the imprint of the grooves 23a', 23b' on the superior and inferior surfaces 15a, 15b of the posterior part 19 of the cage 14 is shallower than the imprint of the grooves 23a, 23b on the superior and inferior surfaces 15a, 15b of the anterior part 18 of the cage 14. According to Figure 5, the distance between the crenellations 16a, 16b on the superior and inferior surfaces 15a, 15b of the cage 14 at their highest point defines the dimension H.

Figures 6 and 7 describe two configurations of assemblies of the delivery system 1 of Figures 1 , 2 and 3 with the cage 14 of Figures 4 and 5. Figure 6 describes a fully engaged assembly, wherein the anterior side 8 of the connecting member 7 connects with the posterior end 19 of the cage 14 through the engagement of the teeth 13a, 13b arranged on the connecting member 7, with the indentations 21 a, 21 b arranged in the posterior part 19 of the cage 14. The full engagement of the system 1 and the cage 14 may also be actuated through the engagement of the tip of the mobile push rod 12 of the delivery system 1 with the bore 22 in the posterior part 19 of the cage 14. The shielding rods 2a, 2b are fully engaged in the grooves 23a, 23a', 23b, 23b' on the superior and inferior surfaces 15a, 15b of the cage 14. The configuration of Figure 6 is typical of the assembly when it is being inserted between two vertebrae 24a, 24b. As is visible in Figure 6, the two outer surfaces 5a, 5b of the two shielding rods 2a, 2b of the delivery system 1 (which define dimension D), protrude beyond the highest crenellations 16a, 16b of the superior and inferior surfaces 15a, 15b of the cage 14 (which define dimension H). Figure 7 describes a partly disengaged assembly, where the delivery system 1 has been partly retracted, or the cage 14 partly pushed forward. This second configuration of the assembly is typical of the stage of retraction of the delivery system 1 after the cage 14 has been delivered in the intervertebral space.

As shown in Figure 8a to 8d, the purpose of the shielding rods 2a, 2b is to protect the vertebrae 24a, 24b from the abrasion by the crenellations 16a, 16b on the cage 14 when the assembly of the delivery system 1 and the cage 14 are introduced in the intervertebral space. Figure 8a shows the assembly of the delivery system 1 and cage 14 with its wedge-shaped anterior part 18 engaged between the vertebrae 24a, 24b. The planes P, P' of the shielding rods 2a, 2b are similar or close to the diverging planes of the wedge-shaped anterior part 18 of the cage 14. Figure 8b shows the assembly being pushed forward between vertebrae 24a, 24b; the outer sides 5a, 5b of the shielding rods 2a, 2b protect the vertebrae 24a, 24b against the abrasion from the crenellations 16a, 16b, as the assembly progresses into the intervertebral space, gliding on the outer sides 5a, 5b of the shielding rods 2a, 2b. This feature eliminates or greatly reduces the need for impactation of the cage into the intervertebral space. Figure 8c shows the crenellations 16a, 16b on approximately half of the superior and inferior surfaces 15a, 15b of the cage 14 being anchored in the endplates of the vertebrae 24a, 24b, and the delivery system 1 being retracted while the mobile rod 12 of the delivery system 1 serves to hold the cage 14 in place. Figure 8d shows the cage 14 fully implanted between the two vertebrae 24a, 24b.

In variations of the first embodiment of the invention, the cross-section of the opposing shielding rods 2a, 2b may be different, and accordingly, the shapes of the grooves 23a, 23a', 23b, 23b' are adjusted to engage with those shapes of the cross-sections of the shielding rods 2a, 2b, such that only the outer sides 5a, 5b of the shielding rods exceed the highest level of the crenellations 16a, 16b of the cage 14. Figures 9a and 9b describe a cage 14.1 with rectangular cross-sectioned grooves 23.1 a, 23.1 a', 23.1 b, 23.1 b', which are suitable to match shielding rods 2.1 a, 2.1 b with a rectangular cross-sections, or a cross-section with three straight sides and a convex outer side 5.1 a, 5.1 b as described in Figures 9a and 9b. A rectangular cross-sectioned groove 23.1 a, 23.1 a', 23.1 b, 23.1 b' is also capable of receiving a shielding rod 2.1 a', 2.1 b' which has an "L" shaped cross-section, with its outer side 5.1 a', 5.1 b' arranged as a flange extending over a narrow portion of the crenellated superior or inferior surfaces 15.1 a, 15.1 b of the cage 1 .1 .

A variation of this embodiment may comprise shielding rods with a wedged outer side 5.1 a", 5.1 b", which define a thin ridge between the distal parts 3.1 a", 3.1 b" and the proximal parts 4.1 a", 4.1 a" of the shielding rods 2.1 a", 2.1 b". In other variations, a cage 14.1 may be arranged with square cross-sectioned grooves 23.12a, 23.12a' matching shielding rods 2.1 a'", 2.1 b'" having a square, rectangular, oblong or elongated half-moon cross-section. Figures 10a and 10b describe a cage 14.2 with triangular cross-sectioned grooves 23.2a, 23.2a', 23.2b, 23.2b', which are suitable to match shielding rods 2.2a, 2.2b with a triangular cross-sections, which may be arranged with the edge as outer side 5.2a, 5.2a, compatible with the cage 14.2 in Figure 10a, or with the edge as inner side 6.2a, 6.2b compatible with the grooves 23.21 a, 23.21 a', 23.21 b, 23.21 b' of the cage 14.2' in Figure 10b. In other variations of the first embodiment, the cross-sections of the grooves 23a, 23a', 23b, 23b' may have any other shape compatible with the cross-sections of the shielding rods 2a', 2b'. In an additional variation of this embodiment, the shielding rods 2a', 2b' can be arranged with a flat distal end 3a', 3b', instead of a beveled distal end. If such flat distal ends 3a', 3b' are arranged so as not to protrude beyond the gradients of the wedge-shaped anterior part 18, of the cage 14, their design does not represent an obstacle to the insertion of the cage, as the vertebrae are initially only engaged by the wedge-shaped anterior part of the cage 14, and only in a second step by the outer sides 5a', 5b', of the shielding rods 2a', 2b'.

Figures 1 1 a, 1 1 b and 1 1 c describe the grooves may be positioned outside of the medial plane of the cage perpendicular to the superior and inferior surfaces 15a, 15b. Figure 1 1 a describes two diagonally and symmetrically positioned circular grooves 23.3a, 23.3b, while Figure 1 1 b describes two ex-centered opposing square grooves 23.31 a, 23.31 b, arranged towards the lateral side 17.31 a of the superior and inferior surfaces 15.31 a, 15.31 b of the cage 14.31 and which do not cross the cavity 20 of the cage 14.31 . Figure 1 1 c shows a cage combining two square shaped grooves 23.32a, 23.33a positioned on the superior surface 15.32a and one single rectangular shaped groove 23.1 b, 23.1 b' positioned on the inferior surface 15.32b. All types of shapes of grooves 23a, 23a', 23b, 23b' may be combined in additional variations of cages. In other variations, a groove may be arranged as longitudinal recess 23.34a, 23.34a' carved in the edges between the lateral sides 17.34a, 17.34a' and superior and inferior surfaces 15.34a, 15.34b of a cage 14.34; such a cage 14.34 may be assembled with "L"-shape cross- sectioned shielding rods 2.1 a', 2.1 b', such that the flange portion may cover a narrow portion of the superior and inferior surfaces 15.34a, 15.34b of the cage 14.34.

All of these cages 14 with multiple groove configurations may be assembled with delivery systems 1 which have multiple shielding rods 2a, 2b with compatible cross-sections to engage the multiple grooves. Cages may also be configured in different variations with one single groove 23a, or one single set of grooves 23a, 23a' on a single superior or inferior surface 15a, 15b of the cage 14. In additional variations, the grooves 23a, 23a' on the superior surface 15a may be arranged in non-parallel axes relative to the grooves 23b, 23b' on the inferior surface 15b of the cage, or in case of multiple grooves 23.32a, 23.33a arranged on one same superior 15.32a or inferior surface, be arranged in non-parallel axes relative to each other.

Figures 12a, 12b, 13 and 14 describe a second embodiment of the invention, wherein the opposing shielding rods 2.4a, 2.4b of the delivery system 1 .4, which have a round cross-section, are assembled with a cage 14.4 having grooves 23.4a, 23.4a', 23.4b, 23.4b' which have a different cross-section, in the shape of a broad "U" shape as shown in Figure 13. The superior and inferior surfaces 15.4a, 15.4b of the cage 14.4 have an ellipsoidal shape when viewed laterally, as represented in Figure 14. According to Figures 12a and 13, the shielding rods 2.4a, 2.4b do not engage the grooves 23.4a 23.4b arranged at the anterior part 18.4 of the cage 14.8 even when the assembly is fully engaged as in Figure 12a, and the inner side of the shielding rods 2.4a, 2.4b are barely in contact with the grooves 23.4a', 23.4b' arranged on the posterior part 19.4 of the cage 14.4, even when the cage and the delivery system 1 .4 are fully assembled as in Figure 12a. In this second embodiment the lateral sides of the shielding rods 2.4a, 2.4b do not engage any grooves at all. The method of insertion of the assembly of the second embodiment between two vertebrae 24a, 24b, and the delivery of the cage 14.4 is similar to the insertion and retraction method described in Figures 8a to 8d for the first embodiment. In variations of the first and second embodiments, the shielding rods 2a, 2.4a, 2.b, 2.4b may be arranged so as to not engage any portion of the bottom of any of the groove 23a, 23a', 23.4a, 23.4a', 23b, 23b', 23.4b, 23.4b' of the cage, even when the cage 14, 14.1 , 14.4 and the delivery system 1 , 1 .1 , 1 .4 are in a fully assembled configuration as shown in Figures 6, 9a and 12a.

Figures 15a to 16 describe a third embodiment of the invention, wherein the delivery system 1 .5 is arranged with rectangular cross-sectioned shielding rods 2.5a, 2.5b, the outer sides 5.5a, 5.5b of which comprise, on a portion between their distal ends 3.5a, 3.5b and proximal ends 4.5a, 4.5b, a longitudinal curved rim 25a, 25b. The rims 25a, 25b are arranged to each define a curved ridge 26a, 26b which is a suitable profile to engage the vertebrae 24a, 24b and thereby cause a thin carving in their endplates. The rims 25a, 25b may also have different cross-sections, such as be arranged with two parallel ridges along their longitudinal axes. According to Figure 15b, the distal ends 3.5a, 3.5b of the shielding rods are not beveled as in the first and second embodiment, but flat.

According to Figure 15b, the cage 14.5 of the assembly of the third embodiment has the shape of a crescent along its longitudinal axis, but any other shapes of cages, including cages 14 to 14.4 of the first and second embodiments, would also be suitable for the assembly of the third embodiment. The cage 14.5 has superior and inferior surfaces 15.5a, 15.5b which are angled relative to each other in the cage's lateral axis, the distance between the superior and inferior surface 15.5a, 15.5b on the lateral side 17.5b of the cage 14.5 being longer than the distance between the superior and inferior surface 15.5a, 15.5b on the other lateral side 17.5a of the cage. The cage 14.5 has grooves 23.5a', 23.5b' arranged on the posterior part 19.5 of the cage 14.5, while there are no grooves on the anterior part 18.5 of the cage, but two respective closure components 27a, 27b instead. The beveled plane of the closure component 27a, 27b has a similar gradient as the planes of the wedge- shaped anterior part 18.5 of the cage 14.5. In variations of the third embodiment, grooves 23.5a, 23.5b may be arranged on the anterior part 18.5 of the cage 14.5 in lieu of the closure components 27a, 27b, or both the closure components 27a, 27b and a section of grooves 23.5a, 23.5b may be arranged together on the anterior part 18.5 of the cage 14.5.

According to Figure 1 6, the benefit of the curved rims 25a, 25b is to slightly carve into the vertebrae 24a, 24b, and as the assembly is pushed forward through one directional force "F" into the intervertebral space, to cause the assembly to follow the curve of the ridge 26a, 26b and follow a different trajectory "V than that of the directional force "F". The cannulated rod 10.5 is preferably articulated towards its distal end near the connecting member 7.5, such that a portion of said cannulated rod 10.5 between said articulation and the posterior side 9.5 of the connecting member 7.5 may, together with the connecting member 7.5 and the shielding rods 2.5a, 2.5b engaged with the cage 10.4, change the trajectory from the first trajectory imposed by force "F' to a trajectory closer to trajectory "T". The articulation on the cannulated rod 10.5 may be any type of articulation such as a cannulated ball-and-socket articulation to allow the motion of a flexible mobile rod 12.5. The articulation of that portion of the cannulated rod 10.5 may also be arranged as a flexible section of the cannulated rod 10.5 itself.

In variations of the third embodiment, the rims 25a, 25b may also be straight, in order to stabilize a straight trajectory of the delivery system 1 .5. In additional variations, the shapes, lengths and profiles of the rims 25a, 25b may also vary between the shielding rods 2.5a and 2.5b, and / or with the shapes, lengths and profiles of the rims 25a, 25b arranged on any additional set of shielding rods 2a', 2b', having any type of cross-section. According to different variations, the distal ends 3.5a, 3.5b of the shielding rods 2.5a, 2.5b may be rotund, stumped, pyramidal, wedged, concave or have any other possible shape.

Figures 18a and 18b describe a fourth embodiment of the invention, wherein a crescent-shaped cage 14.6 is assembled with a delivery system 1 .6 arranged with flexible shielding rods 2.6a, 2.6b. The flexible shielding rods 2.6a, 2.6b are represented in their curved configuration in Figure 19. They may be made of any material ensuring rigidity in the axis between the outer edge 5.6a, 5.6b and inner base 6.6a, 6.6b and flexibility in the lateral axis, or may be made in homogenous yet flexible material, which does not impair the structure or ability of the outer edges 5.6a, 5.6b to engage the vertebrae 24a, 24b. For instance, the shielding rods may be made of memory shape alloy. The cage 14.6 has a curved groove 23.6a, 23.6b arranged on each of the lateral portions of its superior and inferior surfaces 15.6a, 15.6b near the lateral side 17.6b of the cage. Figure 18a describes the assembly of the delivery system 1 .6 and the cage 14.6 fully engaged. This is the configuration for the insertion of the assembly between two vertebrae 24a, 24b, as described in Figures 8a and 8b for the first embodiment. Figure 18b describes the assembly of the delivery system 1 .6 and the cage 14.6 partially dis-engaged. This is the configuration for the removal of the delivery system 1 .6 from the interbody space, as described in Figure 8c for the first embodiment.

The benefit of the flexible shielding rods 2.6a, 2.6b arranged in curved grooves 23.6a, 23.6b of the fourth embodiment, is to allow a steering along trajectory "T" (as described in Figure 16 for the cage 14.5) of the cage 14.6 when the outer edges 5.6a, 5.6b of the shielding rods 2.6a, 2.6b engage the vertebrae 24a, 24b during the insertion process. The second benefit of the flexible shielding rods 2.6a, 2.6b is that their removal is facilitated at the step of the disengagement of the delivery system 1 .6 from the cage, as shown in Figure 18b: the delivery system may be pulled out along any desired axis. Also, the cannulated rod 10.6 of the delivery system 1 .6 does not need to be articulated. In a variation of the fourth embodiment, the shielding rods 2.6a', 2.6b' may be made of rigid material in their curved shape.

In variations of the fourth embodiment, the grooves 23.6a, 23.6b may be arranged with variations in their axes or curves, such as be straight on a certain portion and be curved on another, or have different angles of curves within the same groove 23.6a, 23.6b or even be "S" shaped. Due to their flexible properties in the lateral axis, the flexible rods 2.6a, 2.6b may be arranged in any type of groove axis or curve.

In variations of the first, second, third and fourth embodiments, the cross- sections of the shielding rods 2a, 2b may be not constant, such that they may be arranged to be higher or lower in certain sections in order to protrude more extensively or less extensively from the crenellated surfaces 16a, 16b during certain steps of the insertion process. The cross-sections of the shielding rods 2a, 2b may also have different shapes than those described in the figures, such as race-track, oblong, oval, elongated half-moon, trapezoidal, rhombic or polygonal shapes to match corresponding cross-sections of grooves 23a, 23b or be arranged with broader grooves 23.4a, 23.4a', 23.4b, 23.4b' with compatible cross-sections.

In other variations of the four embodiments, an assembly may combine a delivery system 1 ' with one or more straight shielding rods 2a, 2b, 2.1 a, 2.1 b and one or more flexible rods 2.6a, 2.6b and a cage 14.6' arranged with one or more straight grooves 23a, 23b and one or more curved grooves 23.6a, 23.6b. Such a construct gives the ability to steer the delivery system 1 ' and the cage 14.6' within the interbody space along different sequential trajectories by engaging the vertebrae 24a, 24b alternatively with one and then the other of the shielding rods or sets of shielding rods.

In all embodiments of the invention, the steering rods 2a, 2b may be detachable from the delivery system 1 , or may be arranged to be mobile relative to the connecting member 7 of the delivery system, for instance connected to a mobile push rod passing through a bore arranged in such connecting member 7, or be fully independent from the delivery system 1 .

According to additional variations of the four embodiments, the distance between the inner sides 6a, 6b of the shielding rods 2a, 2b may be increased or decreased to adjust to different heights of various sizes of cages 14 in order to fit the grooves 23a, 23a', 23b, 23b'. This is advantageous as one single delivery system may be used for different heights of cages. The adjustment may be achieved through any technical means arranged in the connecting member 7, such as a rack-and-pinion system or a sliding-and-lock mechanism.

In variations of the first to fourth embodiments of the invention, the delivery system may comprise only one shielding rod 2a or 2b engaging with only one of the superior or inferior surfaces 15a, 15b of the cage 14 through one groove, or set of grooves 23a, 23a', 23b, 23b'.

Each of the first to fourth embodiments of the invention and their variations may comprise an assembly, arranged with shielding rods that only engage one vertebra at a given time during the insertion of the cage.

All embodiments of the invention may combine assemblies of delivery systems and interbody cages which are not made in one single block, such as expandable cages wherein two essentially flat-surfaced components, reflecting the features of the superior and inferior surfaces of the cages of the four embodiments of the invention, are arranged to engage the vertebrae, such essentially flat-surfaced components being mobile relative to each other and are connected anywhere between their posterior and anterior parts through a hinge or other connecting means.

All assemblies of the embodiments of the invention may also combine a delivery system with any other interbody implant which is not designed to promote bony fusion, but to remain articulate, such as disc prostheses.