Patent Application
20110046736
The present invention relates to an intervertebral stabilization assembly comprising an impaction cage body, and to an ancillary device for implanting this stabilization assembly.
The invention falls within the field of arthrodesis, namely the fusing together of the bone of at least two adjacent vertebrae. It will be recalled that the aim of arthrodesis is to allow only micromovements between the vertebrae, and to deaden vibration. These micromovements amongst other things allow the patient, once he has become ambulant again following the operation, to regain his balance as best he can before the bone graft takes.
Typically, an extra-discal assembly for arthrodesis, within the meaning of the invention, allows a range of movement between two vertebrae which is at best equal to about 10% of the natural physiological range. In other words, if there is a maximum natural range of 10° in rotation between two given vertebrae, the stabilization assembly according to the invention is at best able to allow a travel of 1° between these two vertebrae. This authorized range of movement is established about a chosen position, determined by the surgeon at the time of the operation, notably according to the pathology. It will also be noted that this chosen position, while it does of course fall within the authorized range of movement, does not necessarily lie in the middle thereof.
Usually, an intervertebral cage is intended to replace all or part of a disk when the latter has been destroyed by surgery or disease. The main function of such a cage is to restore the discal height, namely the spacing between two facing vertebral bodies. It also performs an anterior stabilization function, allowing bone fusion to be created, in the case of arthrodesis.
The invention is aimed more specifically at a stabilization assembly which comprises a cage body that can be introduced by impaction into the intervertebral space. The conventional implantation method associated with this type of cage first of all makes use of vertebral dilating bougies of increasing size, the dimensions of which typically vary from 8 to 13 mm.
The intervertebral space is dilated by rotating by a quarter of a turn so that the bougie finds itself edge-on, separating the vertebrae from one another by a distance corresponding to the width of this bougie. Once the volume necessary for introducing the cage has been created, this cage is impacted into the intervertebral space.
Conventional cages have disadvantages associated in particular with the way in which they are implanted. Specifically, these methods prove to be somewhat inconvenient to implement, or even dangerous to the patient, inasmuch as the nerve root is manipulated fairly roughly. Furthermore, the taller the cage, the more difficult this impaction maneuver is to perform.
The invention aims to address these various disadvantages. In particular, it aims to provide an intervertebral stabilization assembly the structure of which allows a cage body to be implanted into the intervertebral space in a way that is simple and less dangerous to the patient.
To this end, the subject of the invention is an intervertebral stabilization assembly for arthrodesis, comprising a cage body, intended to be introduced by impaction into the intervertebral space, this assembly further comprising a nose for introducing the cage body into the intervertebral space, this nose being secured to or able to be secured to this cage body, in an eccentric position, so that when this nose is introduced into the intervertebral space, the rotating of this nose causes this intervertebral space to open up and, at the same time, causes the cage body to move in the manner of a cam.
A further subject of the invention is a method for implanting the above assembly, comprising the following steps:
According to other features:
The invention will be described hereinafter with reference to the attached drawings, given solely by way of nonlimiting examples, in which:
The cage body 1 represents a substantially parallelepipedal shape. When viewed from the side, it has a height that increases substantially continuously in the forward direction. Thus h and H are used to denote the extreme heights, namely respectively the rear and front heights of this cage body 1 (to the left and right in
The longitudinal median axis of the cage body, which extends rear to front, is also denoted A. Finally, α and α′ are used to denote the so-called lordosis-inducing angles, which are formed between the main axis A and the respectively upper 2 and lower 3 surfaces of the cage body.
In terms of numerical values, and purely by way of indication, the height h ranges between 5 and 8 mm, the height H ranges between 7 and 15 mm, the length L ranges between 20 and 25 mm, while the width l ranges between 12 and 14 mm. In addition, the angles α and α′ are advantageously equal, and range in value between 4 and 8°. Under such conditions, the overall lordosis-inducing angle, corresponding to the angle (α+α′), ranges between 8 and 16° and is notably close to 15°.
The cage body 1, of parallelepipedal shape, is truncated by a rounded lateral edge 4 that has no sharp edges and the function of which will be detailed hereinbelow. In addition, the rear face 6 of the body 1 is hollowed with a transverse cut 8 which communicates with an axial opening 10 for the passage of a tool. Finally, at the front face 12, this opening 10 opens into a housing 14 of parallelepipedal shape, the walls of which are square in cross section.
The upper 2 and lower 3 surfaces mentioned hereinabove have a notched surface so as, in the conventional way, to catch more firmly on the vertebral plates. A cutout 18 is also hollowed into the cage body 1, connecting these upper and lower surfaces. This cutout allows the passage of a bone graft, in a way also known per se.
The stabilization assembly according to the invention further comprises the aforementioned insert 30, which comprises a parallelepipedal mount 32, the shape of which complements that of the housing 14. This mount 32 is hollowed by an axial tapping 34 which extends in the continuation of the opening 10.
The mount 32 further supports a nose 36, projecting toward the front of the cage body. When viewed from the side, in
More specifically, if the vertical mid-plane of the cage body which contains the axis A is denoted P, the nose 36 is positioned on the opposite side of this mid-plane to the lateral edge 4. The longitudinal axis of the nose, when viewed from above in
The magnitude of the abovementioned offset is denoted d in
The length of the nose, namely the distance by which this nose projects forward, from the front face of the cage body 1, is also denoted L′. Advantageously, this length L′ ranges between 15 and 25% of the total length L of the cage body. Finally, the nose 36 has a tapered end tip 38, allowing this nose to be inserted more easily between the adjacent vertebrae.
In order to implant the cage body 1 and its insert 30 the intervertebral space illustrated schematically in
Moreover, the insert 30 is immobilized with respect to the body 1, while at the same time blocking this body 1 and the ancillary 50 relative to one another. To do this, the mount 32 is positioned in the housing 14 and the threaded end 56 of the rod 54 is screwed into the tapping 34. In addition, the two ribs 58 are locked in the cut 8. Under these conditions, the cage body 1, the insert 30 and the ancillary 50 are secured to one another.
The nose 36 is then introduced into the intervertebral space, via its smallest dimension, namely its width. As
Let P″ be the median horizontal plane of the intervertebral space. Once the nose has been inserted via its smallest dimension, this plane P″ coincides with the main plane P′ of the nose, whereas the main plane P of the cage body 1 is offset from the mid-plane P″. In general, this plane P usually lies below the two planes P′ and P″.
However, if there is only a small offset between the main plane P of the body 1 and the main plane P′ of the nose, it is then possible to position most of the cage body above the mid-plane of the intervertebral space. By contrast, in the event of a larger offset, the option illustrated in
The surgeon then operates the grasping member 52, turning it in the counterclockwise direction embodied by the arrow F (see
In other words, this rotation causes the cage body 1 to move toward the center of the spinal column. In that way, the rounded edge 4 comes into contact with the roots R and endings T, and this tends to push them toward the center of the column, in the direction of the arrow F′. This moving of the nerves is performed gently, given that the lateral edge 4 has no sharp edges and that this movement takes place gradually.
As illustrated in
In
Finally, having caused the nose to pivot, this nose now being in its position of
Once the cage body has been inserted, the rod 54 is unscrewed from the tapping 34 so that the insert 30 supporting the nose 36 is no longer secured to the cage body 1. It then becomes possible for this insert to be pushed back, using a suitable pusher, not depicted. This insert 30 then drops onto the plate of the lower vertebra V2.
Advantageously, the insert 30 is made of a biocompatible material capable of forming a bone graft. Under such conditions, it is, for example, PEEK or BMP (bone morphogenic protein). Finally, once the insert 30 has been detached from the cage body 1, the ribs 58 are withdrawn from the cut 8, to free the ancillary 50 from this cage body set in place in the intervertebral space.
In contrast to the first embodiment, there is no collaboration here between two ribs and a transverse cut. By contrast, the grasping member 52′ is provided with two fingers 58′ which penetrate blind holes 8′ formed opposite in the cage body 1′.
In order to secure the ancillary 50′ to the cage body 1′ the fingers 58′ are introduced into the blind holes 8′, screwing the threaded end 56′ into the tapping 34′. The cage body 1 is implanted by means of the nose 36′ in a similar way to the way described with reference to the first embodiment. This first alternative form is advantageous insofar as it ensures satisfactory grasp of the cage at the time of turning.
By contrast with the first two embodiments, the nose 36″ is made as a single piece with the cage body 1″. In other words, this body and this nose form a one-piece assembly. As a result, the cage body has no housing, like the housing 14 of the first embodiment. Its front face 12″ is extended directly by the nose 36″ which is formed as an integral part thereof.
Furthermore, the implanting ancillary, not depicted, is analogous to one of these described with reference to the first two embodiments. However, this ancillary has no rod, like the rod 54 in
This second alternative form is advantageous, notably in terms of simplicity. Specifically, this cage has a simple mechanical structure accompanied by good robustness. In addition, it entails a low number of handling operations.
According to an additional alternative form, the cage body may be associated with a nose, which is not attached removably as in
In the first of these axial positions, the nose projects beyond the cage body 201 so that it can be introduced into the intervertebral space in order to perform the cam effect of the eccentric cage body. This nose is then turned, as explained previously, so as to make the intervertebral space taller, then the cage is inserted axially into this space. Finally, this nose is retracted into the cage body so that it no longer projects toward the front thereof. This is advantageous because this nose then does not occupy any additional space within the intervertebral space.
In the alternative form of
The cage body 101 differs from that 1 of the first embodiment notably in that it has no transverse cut. The latter is replaced by two longitudinal grooves 108 and 109 hollowed out respectively in the upper 102 and lower 103 surfaces.
When viewed from above, these two grooves extend along an axis A″ which is offset from the main axis A of the cage body. By comparison with
In addition, by comparison with the first embodiment, the cage body 101 has no axial opening like the one 10. Nor is there any housing like the housing 14.
The cage body 101 is associated with an implanting member 150, which has a grasping body 152 extended by two rods 154 and 155 capable of penetrating the grooves 108 and 109. When viewed from the side, these two branches extend such that they diverge from the body 152, at the angles α and α′ that correspond to the lordosis-inducing angles of the cage body, the height of which increases toward the front.
Each rod 154, 155 ends in a respective end-piece 136, 137. Unlike these branches, these end-pieces 136 and 137 are “straight”, namely parallel to the main axis A when viewed from the side. Finally, the body 152 is provided with a piston 159 able to move between a retracted position and a position in which it projects forward.
The implanting member 150 and the cage body 101 are secured to one another as follows. First of all, the branches 154 and 155 have to be introduced into the grooves 108 and 109. After this, the end-pieces 136 and 137 project, from the front face 112 of the cage body 101, by a distance L′ substantially corresponding to the length of the nose in the first embodiment.
As
Next, the assembly made up of the cage body 101 and of the implanting member 150 is pivoted in the counterclockwise direction as illustrated in
After a rotation through a quarter of a turn, the end-pieces 136 and 137 are now positioned one above the other, so that the intervertebral space E is made significantly taller (
In this example, the deformable cage body 301 is C shaped. However, provision could be made for it to be in accordance with any one of the embodiments described in FR-A-2 913 328 in the name of the present applicant. Thus, the cage body may notably be in the form of a strip defining a closed loop.
Returning to
These
Thus, for the purposes of implantation, the unit has first of all to be inserted between the two flanges of the cage body, in the position of
Once the cage body has been fitted into the intervertebral space, the auxiliary unit is removed using any appropriate means. Under these conditions, this cage body is then able, first of all, to deform so as to allow the vertebrae to be placed in the chosen lordosis position, notably under the action of posterior bracing, then to perform the arthrodesis function as defined hereinabove. In addition, the presence of the unit 350 covers the sharp edges of the C, thus preserving the nerve root.
It will also be noted that the nose, in addition to acting as a cam, performs an additional function of mechanically stabilizing the deformable cage body. Thus, in the example illustrated, this nose prevents the cage body from collapsing near its web.
An additional embodiment according to the invention is illustrated in
The implantation member 450 differs from that 150 in that it has rods or branches 454 and 455 which end in end-pieces 436 and 437 that extend in the continuation of these rods. In other words, not only the end-pieces but also the rods are parallel to the main axis of the cage body, when viewed from the side.
These rods and these end-pieces enter grooves 408 and 409 formed in the cage body, and which also run parallel to the main axis A, because the branches are not inclined. Finally, the implanting member 450 is provided with a threaded rod 459 able to penetrate a tapped hole 411 formed in the cage body. This allows the cage body to be grasped and, therefore, fitted, more easily.
The various steps in the implanting of the cage body are analogous to those described hereinabove with reference to
The invention is not restricted to the embodiments described and depicted.
Thus, in most of the embodiments set out hereinabove, the cage body has a height which increases toward the front. However, by way of alternative, an eccentric nose according to the invention can be associated with any type of impaction cage, the height of which is invariable, or even increases in the direction of its rear part.
An embodiment such as this is illustrated in
As
It will further be noted that, in the various embodiments hereinabove, the nose is eccentric with respect to the cage body, namely that the main axes thereof are separate. However, by way of alternative as depicted in
This alternative form is illustrated in
This cage body 501 collaborates with an implanting member 550 which is provided with two branches 554 and 555 each of which ends in a respective end-piece 536 and 537 which extends in the continuation of this branch. When the aforementioned branches are slipped into the openings 508 and 509, the end-pieces 536 and 537 project in the opposite direction, namely to the right in
The invention makes it possible to achieve the aforementioned objectives.
Specifically, the cage body according to the invention, aside from performing its conventional intervertebral spacer function, performs an additional function of moving the nerve root aside. This then simplifies the insertion operation, making it less dangerous to the nerve tissue than in the prior art. In addition, by virtue of the invention, it is possible to admit into the intervertebral space cages the height of which is greater than could be admitted in the prior art. Specifically, such tall cages could not be inserted easily using the techniques employed in the prior art.
Finally, the invention makes it possible considerably to simplify the implantation of the intervertebral cage. Specifically, the surgeon is able, in a single action, to perform something that requires several hands in the prior art. This also allows for better control, reduces the number of operations performed “blind” and allows the cage to be fitted more gently.
Various additional alternative forms of the invention will now be described. For each alternative described, the mechanical elements analogous to those of the preceding figures are increased by 100 with respect to the alternative form that immediately precedes it.
The nose 636 may be associated with a wire-like member 646 which notably allows it to be positioned optimally during placement. This wire-like member can also allow the nose to be removed once the cage has been fitted. With a view to insertion, the two branches 654 and 655 are first of all fixed with respect to the nose 636, for example by screwing. It will be noted that, in this embodiment, the branches do not have to extend at the periphery of the cage body 601, namely they may be positioned centrally with respect thereto.
Next, a leg 610 provided with a crosspiece 611 is attached so as to join the two branches together to form a fork. The cage body is then introduced into the intervertebral space as described hereinabove, using the nose 636 and, if appropriate, the wire-like member 646, to achieve better positioning of the nose.
Once the cage body is in place, the two branches are removed from the nose then the nose itself is removed using the wire-like member 646. This removal of the nose can be performed either from the outside of the cage body 601, as in
In addition, as illustrated in
By way of additional alternative form, the nose 736 may be formed of a number of elements other than three. In addition, the geometric shape of these elements may be other than that described in this figure.
The envelope has a main part ending in a projection 836′ intended to form a nose 836 according to one or other of the preceding embodiments. This envelope defines an interior volume V, being formed, for example, of a thin wall of an appropriate material, notably a biocompatible plastic or metal.
The first insert has the same shape as the envelope and, in particular, a projection 836″ similar to the one 836′. When it has been inserted into its interior volume, this insert 801′ does not project beyond the front of this envelope (
Once this insertion has been performed, the first insert needs to be removed from the interior volume of the envelope, leaving this envelope between the vertebrae. It will be noted that the material of which this envelope is made needs to be strong enough that it does not become crushed during the operation, once the first insert has been removed. It will also be noted that this strength does not need to be extremely high because the load exerted by the vertebrae of the anesthetized patient is relatively low. In addition, as will be seen later on, it is advantageous for the envelope to be able to be crushed if a greater force is applied.
Next, as illustrated in
By contrast with the previous embodiment, the envelope 901′ is substantially cylindrical, with an anterior part in the form of a section of a sphere, so as to form an opening d of a diameter smaller than that of the cylinder. Moreover, the implanting insert 901″ first of all comprises a main part, of the same shape as the walls of the envelope, which ends in an end-piece 936 forming an eccentric nose within the meaning of the invention (see
The assembly formed by this envelope and this first insert can then be positioned between the vertebrae according to one of the methods described hereinabove. Next, this first insert 901″ is removed and replaced, in this instance, by two additional inserts 903 and 905 (see
Once these two additional inserts have been positioned in the interior volume of the envelope, a posterior force F can be applied tending to move the two vertebrae closer together (
In the insertion position illustrated in
This end-piece may project through the cutout, so as to form the insertion nose. Then, once insertion has been performed in the conventional way, this end-piece can be retracted so as to prevent the envelope from collapsing, as in the previous embodiment (
The C-shaped envelope of
Use is made of an insertion fork, the branches 1254 and 1255 of which run longitudinally across the two plates. In addition, a nose 1236 collaborates with these forks, as for example in the embodiment of
In addition, in
In
Of the arrangements depicted in
In the various embodiments set out hereinabove, cage bodies intended to be introduced into the intervertebral space have been described. These may be associated with at least one extra-discal posterior element connecting two vertebrae, particularly two adjacent vertebrae. An extra-discal element such as this is able to limit, or even prevent, intervertebral flexion and/or extension movements, so as to remain within the area of arthrodesis.
Such extra-discal elements of the posterior type may be produced in any appropriate form. Mention may, for example, be made of the use of plates or even of more refined devices such as those described in any one of the following French patent applications filed in the name of the applicant:
Advantageously, these extra-discal elements are segmented, namely connect two adjacent vertebrae. Likewise advantageously, they are articulated on the two screws, notably of the pedicle screw type, that they connect. Finally, these extra-discal elements are tensioned so as to form a brace or a stay, it being understood that it is possible to combine two distinct elements respectively forming a brace and a stay.
According to an advantageous alternative form of the invention which has not been depicted, existing cage bodies can be equipped with attached elements intended to form the insertion nose. These attached elements are thus somewhat like caps that are fitted to the anterior face of the conventional cage body. Such a cap can be positioned against the cage body or alternatively can be connected more firmly to this cage body. In the latter option, provision may be made for the cap to have a relatively flexible fixing region able to fit over the cage body, and a rigid end region forming the nose.
In the various embodiments described hereinabove as forming part of the invention, use is made of mechanical components suited to performing arthrodesis as defined at the beginning of the present description. The person skilled in the art will therefore assign the appropriate features to these components, particularly in terms of their stiffness, while at the same time taking into consideration the way in which they are combined with any posterior element that might be used.
| Number | Date | Country | Kind |
|---|---|---|---|
| 08 50220 | Jan 2008 | FR | national |
| 08 52208 | Apr 2008 | FR | national |
| 08 56560 | Sep 2008 | FR | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/FR2009/050048 | 1/14/2009 | WO | 00 | 11/10/2010 |
