FR2919997A1 - INTERVERTEBRAL STABILIZATION ASSEMBLY FOR ARTHRODESIS - Google Patents

Abstract

Intravertebral stabilization assembly for connecting at least two adjacent vertebrae (V1, V2), comprising: - at least one extra-disc element (40), intended to be disposed behind the intervertebral space (10), which is capable of preventing any displacement between two adjacent vertebrae in the direction of the intervertebral flexion, and- at least one intra-discal element, of cage type (42), capable of ensuring an intervertebral spacing function, this cage having a first introduction configuration between the two adjacent vertebrae, in which this cage cooperates with the vertebrae placed in an insertion position, this cage further having a configuration of lordosis, in which it cooperates with the vertebrae also placed in a configuration of lordosis, the intra-discal element being able to deform in a reversible manner between its introduction configuration and its configuration of set in lordosis.

Description

INTERVERTEBRAL STABILIZATION ASSEMBLY FOR ARTHRODESIS

  The present invention relates to an intervertebral dynamic stabilization assembly for arthrodesis. The invention is in the field of arthrodesis, namely bone fusion between at least two adjacent vertebrae. The known state of the art uses an intra-disc cage, intended to increase the height of the disk, namely the distance separating the two successive vertebral bodies. This cage is associated with a rod or a neutralization plate, which is intended to ensure the stability of the assembly assembly, in particular to prevent the migration of the aforementioned cage outside the intervertebral space. In the usual way, this rod or this plate is made integrally with pedicle screws, which penetrate into the vertebral bodies opposite. In addition, these rigid assemblies often extend regionally, namely that they connect several vertebral stages. This known solution, however, involves certain disadvantages. Indeed, it has been found that patients with these components are subject to pain, as well as to poor positions, in particular to lordosis deficiency. Under these conditions, these patients suffer in particular premature wear of the disc placed immediately above the upper vertebra, among those receiving the pedicle screws.

  For this purpose, it relates to an intervertebral stabilization assembly for arthrodesis, intended to connect at least two neighboring vertebrae, comprising: - at least one extra-disc element, intended to be disposed at the rear of the intervertebral space, which is capable of substantially preventing any displacement between two adjacent vertebrae at least in the direction of the intervertebral flexion, and - at least one intra-discal element, cage-type, capable of ensuring an intervertebral spacing function, this cage having a first insertion configuration between the two adjacent vertebrae, in which this cage cooperates with the vertebrae placed in an insertion position, this cage also having a configuration of lordosis, different from its introduction configuration, in which it cooperates with the vertebrae placed also in a configuration of lordosis, the intra-discal element being clean to reversibly deform between its introduction configuration and its lordosis configuration. According to other features - each intra-discal element is formed by a band of folded material, having in particular a C-shape or a loop shape, this band of folded material being able to deform in a reversible manner between the configuration of introduction and configuration of lordosis setting; each intra-discal element comprises: - a front element, formed by at least a first band of folded material, - at least one rear element, formed by at least one other band of folded material, able to be deformed in a reversible manner, between the introductory configuration and the lordosis configuration, and - a mechanical junction zone between the front and rear elements, allowing intervertebral spacing to be maintained; a single front element is provided, as well as two rear elements forming a V seen from above; the intra-discal element comprises a main body in the form of a loop, as well as a reinforcing wall connecting two zones distant from this body; the intra-discal element is provided with abutment means adapted to limit the amplitude of its movement, during the transition from the introducer configuration to the configuration of lordosis. ; the or each extra-discal element cooperates with two pedicular screws implanted in two adjacent vertebrae, and this extra-disc element has at least one, in particular three degrees of freedom in rotation relative to each of these pedicle screws; the intra-discal element is a flexible body intended to be placed in the intra-disc space so as to fill the latter; - The flexible body is deformable, while not substantially compressible. The subject of the invention is also a method of laying the above assembly, in which: the cage is introduced, in its introduction configuration, between the two vertebrae which are themselves in their introductory configuration corresponding to a neutral physiological position, or even to a position of kyphosis, - pedicular screws are placed in the corresponding vertebrae, - the screws are brought together, so as to place the vertebrae in their lordosis configuration, and thus to dispose also each cage in its configuration of lordosis. According to an advantageous characteristic, between two adjacent vertebrae a lordosis angle greater than 15, preferably 20, is formed. The invention will be described below, with reference to the accompanying drawings, given solely by way of non-limiting examples, in which: - Figure 1 is a side view, illustrating an intervertebral stabilization assembly according to the invention; ; FIG. 2 is a rear view illustrating the intervertebral stabilization assembly shown in FIG. 1; Figure 3 is a side view, similar to Figure 1, illustrating an intra-discal element belonging to the stabilization assembly of the preceding figures, in its insertion position between two vertebrae; FIG. 3A is a graph illustrating the operation of the intervertebral stabilization assembly of FIGS. 1 to 3; FIGS. 4, 4A and 5 are perspective views, illustrating three alternative embodiments of the intra-discal element belonging to the stabilization assembly of the preceding figures; FIGS. 6 and 7 are respectively side and perspective views, illustrating two additional variants of embodiment of this intra-discal element; FIGS. 8 to 10 are perspective views, illustrating a further alternative embodiment of this intra-disc element, in three different configurations; - Figures 11 and 12 are side views, illustrating yet another alternative embodiment of this intra-discal element, in two different configurations - Figures 13 and 14 are side views, illustrating two other variants of this embodiment. intra-discal element; FIG. 15 is a perspective view illustrating a further variant of this intra-disc element; - Figure 16 is a side view, illustrating yet another alternative embodiment of this intra-discal element; and FIGS. 17A to 17C are side views, illustrating two steps of setting up a stabilization assembly according to another variant embodiment of the invention. Figures 1 to 3 illustrate a first embodiment of an intervertebral stabilization assembly according to the invention. In these figures, there are firstly two adjacent vertebrae VI and V2, each of which comprises a respective vertebral body 12 and 22. These two vertebrae define an intervertebral space 10, as well as an anterior hinge 11. Moreover, on the FIG. 2 shows the sagittal axis of the patient. Two pedicle screws 14 and 24 are attached in the respective vertebral bodies 12 and 22, in a manner known per se. In addition, each pair of pedicle screws, located on the same side of the sagittal axis, is connected by a corresponding stay. In the illustrated example, there are two plates 40, forming such stays, which are arranged on either side of the axis A. Each plate is for example in accordance with the teaching of US-A4 743 260. In the example illustrated in Figures 1 to 3, there is shown extra-disc elements made in the form of plates. However, by way of variant not shown, it is possible to use any type of element which provides a function of stay, so as to prevent any displacement between the two vertebrae V-1 and V2, at least in the direction of the intervertebral flexion, even in the sense of extension. Thus, one can use, as extra-discal element, a rod, or a bar.

  Advantageously, each extra-disc type guy-type element has a proper shape. This means that it is likely to keep the same geometry in the absence of external constraints, especially under the effect of gravity alone. In addition, in this case, its geometry does not vary substantially during the usual constraints to which it is subjected, once implanted on the patient. The stabilization assembly according to the invention further comprises an intra-discal element, which is in this case a spring blade 42, C-shaped, which has a core 421 provided opposite the plate 40, that is to say in the vicinity of the anterior hinge 11. This soul is extended by two wings 422, each of which bears against a respective vertebral body 12 or 22. This leaf spring 42 thus has an open end 423, facing the back of the patient that is, it is adjacent to the plate 40. This leaf spring 42 is made of any suitable biocompatible material, or a composite material.

  As illustrated in FIG. 2, it is advantageous to use two spring blades 42a and 42b provided on either side of the sagittal axis A. This makes it possible to separately adjust the mechanical characteristics of these two leaf springs. to account for any lateral dissymmetrical collapse of the disc.

  The installation of the intervertebral stabilization assembly, comprising the plates 40 and the spring blades 42, is as follows. It is first of all to introduce each spring blade 42 between the two vertebrae, namely within the intervertebral space 10. For this purpose, as illustrated in FIG. 3, each blade is first placed. spring in its introduction position, which corresponds in this case to an absence of stress, so that the wings 422 are substantially parallel or flared relative to each other. Note that the vertebrae VI and V2 are also in a configuration called introduction, in this Figure 3, namely that the walls facing the vertebral bodies are in the neutral position, namely parallel, namely even light kyphosis. Once the cage is introduced into the intervertebral space, the pedicle screws are implanted in the two respective vertebral bodies. However, as an alternative, it is possible to implement these screws before the introduction of spring blades. Then, each pair of adjacent screws is brought together, for example by means of a tool not shown, so as to place the vertebrae in a position of lordosis. This induces the deformation of each spring leaf, by pinching, namely that the free ends of the wings 422 tend to approach each other, as shown in FIG. 1. Under these conditions, each spring blade is in a so-called lordosis position. , while keeping its intervertebral spacing function, or spacer. In addition, the vertebrae VI and V2 are also in a lordosis configuration, as illustrated in this figure 1. Finally, once the screws are close together, each plate is secured to the free ends of these screws. In these conditions, it will be noted that there is a significant interaction between each plate, forming stay, and each leaf spring, forming not only intervertebral retractor, but also intervertebral damper. As will be seen in more detail in the following, each leaf spring also allows the necessary lordosis setting according to the intervertebral stage considered, namely a lordosis angle can for example reach a value up to 25 if necessary, in particularly for stage L5-S1.

  During the lordosis of the patient, the stress thus exerted tends to deform each elastic spring leaf 42, by mutual rapprochement of the wings 422. This blade then exerts a restoring force, indicated by the arrows G in FIG. this fact, it opposes a permanent elastic counter-stress to the extra-discal plate 40. Furthermore, when returning to the neutral position of the patient, namely in his upright position, the latter is in a position of natural lordosis. The plate then plays its usual role of prestressing in lordosis of the intra-discal element, while it continues to perform its function of intervertebral retractor while deforming in the direction of lordosis, under the action of the posterior constraint. In this configuration, the anteroposterior interactive pair, formed by the plate 40 and the cage 42, is adjusted to place the vertebrae in their physiological operating position. Thus, in addition to the intervertebral spacing, there is a real lordosis of the patient, with angulations that correspond to local anatomical needs, for a proper functioning of the erected human position and satisfactory muscular work. The interaction of this anteroposterior pair is more particularly illustrated in FIG. 3A. On the latter, we first find a first marker, consisting of two first axes, namely a first X axis X'1-X1, corresponding to the degree of lordosis, noted a, which is adopted by the patient. In other words, the more one is to the left of the curve and the more kyphosis is pronounced whereas, if one progresses towards the right of this curve, one finds a more and more important lordosis. It is assumed that a zero abscissa corresponds to a position in which the wings 422 of the cage 42 are parallel. On the ordinate we find the posterior clamping force, denoted Fi. This first ordinate axis thus corresponds to the intensity of the force generated by the posterior stay 40. It is assumed that one starts from an initial position, noted Po, which corresponds substantially to that of FIG. 3. In this case the clamping force F is by definition zero since the plate 40 is not yet implanted. In addition, the patient is in kyphosis position, since the wings 422 are slightly apart from each other, namely that the abscissa of this point Po is slightly negative. Then, during the implantation of the posterior stay 40, the clamping force FI of the latter increases, which causes a lordosis of the patient. In other words, the increase in the clamping force induces a displacement of the curve towards positive ordinates, while the setting in lordosis also induces a displacement towards positive abscissas. At the end of the implantation of the stay, the subject is in a neutral position, denoted PN, which corresponds to a physiologically erected position. This phase of implantation of the posterior stay 40 is materialized by the zone I of the curve, which corresponds, as we have seen, to progressive lordosis of the patient as the posterior clamping force increases. . FIG. 3A illustrates, in addition to the implantation phase of the stay 40 described above, the phase of use of the anteroposterior pair thus put in place. For this purpose, starting from the neutral position PN, a second mark is drawn, whose X'2-X2 abscissa axis also corresponds to the lordosis angle of the patient. On the other hand, the Y'2-Y2 ordinate axis now corresponds to the F2 force exerted by the subject. In other words, a positive value of F2, ie towards the top of the curve, corresponds to a subject who exerts a effort to lean back. Conversely, the more the subject exerts an effort to lean forward, the more we are in the lower part of the curve, namely negative ordinates.

  It will be assumed in the following that each plate 40 is hollowed out with two oblong holes 40 'and 40 ", more particularly shown in FIG. 2. The length of these orifices is greater than the diameter of the pedicle screws 14 and 24, so that these The latter are capable of moving along these orifices It is assumed that in FIG. 1, which corresponds to the neutral position PN, the pedicle screws 14 and 24 are in abutment against the opposite walls of these oblong orifices. 3A, if it is assumed that the patient is leaning backwards, the pedicle screws 14 and 24 are therefore free to move towards each other, within the oblong holes 40 'and 40 ". The curve thus tends to move towards positive values of a, which increase in a linear manner as a function of the force thus applied by the subject. The corresponding area is assigned reference II in Figure 3A.

  On the other hand, if the patient tries to lean forward from the neutral position PN of FIG. 1, the stay prevents any intervertebral flexion, by placing the pedicle screws against the walls of the orifices 40 'and 40 ". Under these conditions, when the force F2 moves towards negative values, this however does not induce any displacement of the curve towards negative values of 0. The corresponding zone is materialized by the reference III in FIG. III, the bending forces, generated by the patient, result in compressive forces in the cage 42, namely a damping in kyphosis.It will be noted that, in accordance with the invention, a position of equilibrium, such as than that PN, which is not substantially accompanied by a degree of freedom.This is therefore favorable for a good arthrodesis.In contrast, the location of this equilibrium position can be modified depending on the parameter. es, such as the position of the subject. The difference between the object of the invention and a prosthesis is thus seen, which is by definition associated with the existence of at least one degree of permanent freedom. In addition, it should be noted that the invention is advantageous in that it connects the vertebral vertebrae by vertebra. This is to be compared with the prior art, which uses regional implants, which connect several vertebral stages to each other. Consequently, this notion of segmentation, on which the invention is based, makes it possible to satisfactorily treat the various pathologies that the vertebral column may have. Note further that the plate 40 is preferably articulated relative to the pedicle screws 14 and 24. This means that in the neutral position of Figure 1, there is at least one, in particular three degrees of freedom in rotation between the plate 40 and each of the screws 14 and 24. This is advantageous over the embodiments of the prior art, wherein the rod or the plate connecting two vertebrae is mounted integrally on the pedicle screws. As a variant not shown, it can be provided to use an additional extra-discal member, ensuring an intervertebral strut function. This stay is then associated with the stay 40 of Figure 1.

  FIG. 4 illustrates an alternative embodiment of the spring blade, in which the latter is associated with a secondary spring 143, connecting the opposite wings 1422. Thus, during the deformation of the leaf spring 142 due to the setting in lordosis of the patient, the spring 143 opposes a resistance of controlled intensity.

  In this regard, it will be appreciated that it is possible to vary the mechanical characteristics of this spring 143, depending on the pathology that is to be treated, and in particular if the collapse of the disk is asymmetrical right-left type. In the latter case, there are two different leaf springs, on either side of the axis A. As a variant not shown, the spring 143 can be replaced by a leaf spring, similar to that 142, which has lower dimensions as well as lower resistance. FIG. 4A illustrates an alternative embodiment of the leaf spring 142 ', in which the opposite wings 142' 2 thereof are extended by returns 143 ', which extend towards one another. Thus, during the deformation of this blade 142 ', the nip of the wings is limited in its amplitude by the returns 143', which abut against each other. This embodiment is advantageous, insofar as it makes it possible to avoid a too strong degree of lordosis, as well as an additional compression of the nerve roots. It will be noted that, in all the embodiments of the present application, the various intra-disc elements may be equipped with such limiters of deformation limitation. FIG. 5 illustrates a further variant embodiment of the intra-discal elastic member of the preceding figures. In this embodiment, the leaf spring 142 is replaced by a solid body 242, also generally having a shape of C, which is provided with a core 2421 from which extend two wings 2422. The core is hollowed a notch 244, allowing the deformation of this massive body in the manner of a clothespin. Figure 6 illustrates a further variant embodiment of the intra-disc elastic member. The latter, affected in its entirety by the reference 342, differs from that 42 of FIG. 1 in that it comprises a non-deformable rigid body 345, made for example in the form of a cylindrical axis, extending transversely. This rigid body 345, which is fixed by any suitable means against the core 3421 of the spring blade 342, makes it possible to maintain substantially constant the height of this blade 342, at least in the vicinity of this body 345, whatever the level of imposed constraint. Under these conditions, this blade 342 is able to reliably ensure its intervertebral spacing function. In this regard, it should be noted that this elastic member 342 can be divided into two regions. The first region 342A, located at the front, namely opposite the plate 40, is substantially rigid with respect to a vertical compression force, so that it more particularly ensures the spacing function intervertebral. Furthermore, the second region 342B, facing the plate 40, is adapted to be crushed during the lordosis, while providing a controlled resistance as has been explained in the foregoing. Note that the rigid body 345 can equip the implant of Figures 4 and 5. In particular, in the case of Figure 5, it can be housed in the notch 244. With reference to Figure 2, we note that the two spring blades 42a and 42b are placed substantially parallel to each other, on either side of the sagittal axis A. However, as a variant, it is possible for these two spring blades to be placed obliquely, so as to form views from above generally a V, the tip is facing forward, ie opposite the plate 40.

  As a further variant, illustrated in FIG. 7, these two spring blades can be grouped into a single intradiscal elastic member, generally designated by the reference 442. The latter comprises first of all a median rigid body 445 made by example in the form of a sphere, providing the effect of spacing, similarly to the rigid body 345 of Figure 6. This rigid body 445 is for example placed in the vicinity of the sagittal axis A of the patient. In addition, two pairs of elastic wings 44221 and 44222 extend from the median body 445, namely on either side of the sagittal axis A, respectively to the left and to the right thereof. Thus, seen from above, the elastic member 442 has a shape of V, the tip is turned forward. Each pair of wings 44221 and 44222 is of elastic and deformable nature, so that they provide resistance to the extra-disc stay, similarly for example to the wings 422 equipping the implant of Figure 1. As in the case of Figure 2, it can be provided that these two pairs of wings have different mechanical characteristics, so as to oppose variable resistances, especially in the case of a lateral dissymmetrical collapse of the disc. In the previous embodiments, described with reference to FIGS. 4 and following, the insertion position of each intradiscal element corresponds to a configuration, in which the wings are substantially parallel, or even flared in the direction of their free end.

  On the other hand, the position of setting in lordosis corresponds to a configuration, in which the free ends of these wings are brought together, which leads to a pinch of these wings opposite. FIGS. 8 to 10 illustrate a further variant embodiment of the intra-discal organ, which is assigned reference numeral 542. In this embodiment, this member 542 is constituted by a leaf spring, folded on itself at the way of a ring. Thus, compared to the embodiment of the preceding figures, this intra-discal organ does not have an open end towards the rear, namely on the right of the sheet. Note however that it is not closed laterally, namely towards the front or back of the sheet. In its introduction configuration between the vertebrae, as shown in Figure 9, the annular spring blade 542 tends to flatten, while having a height that is substantially constant from back to front. In contrast, in its configuration of lordosis, illustrated in Figure 12, this body is deformed by decreasing the radius of curvature of its rear portion, combined with an increase in the radius of curvature of its front portion. FIGS. 11 and 12 illustrate a last variant embodiment of the invention, in which the intra-disc elastic member 542 'differs from that 542 of the preceding figures, in that it is provided with a rigid sphere 544', movable relative to the blade spring back and forth thereof. In this respect, it will be noted that the spring blade 542 'is advantageously closed on its sides, namely towards the front and the rear of the sheet, so as to prevent this sphere from escaping from its interior volume. In addition, this interior volume can be filled by means of a fluid to facilitate, or otherwise to slow the movement of this sphere.

  As shown in Figure 11, in the insertion position of the intra-discal organ, the sphere is substantially in the middle position. In contrast, in its position of lordosis, the sphere tends to move forward, as shown in Figure 12. This ensures the intervertebral spacing function, while creating a lordosis effect. In the previous embodiments, the intra-discal element is formed by a single band folded in particular in the manner of a loop, or a C. In the following embodiments, we will describe elements intra-discal. discs which consist of several of these loops.

  Thus, in FIG. 13, the intra-discal element 642 is formed of two C-shaped spring blades, 6421 and 6422 respectively, intended to be placed respectively at the front and at the rear of the intervertebral space. Note that the front blade 6421 has a shorter length than the rear blade 6422. In addition, these two blades are arranged back to back, namely that the open ends of the two C are opposite. Finally, these two bands 6421 and 6422 define a median junction zone 6423, which makes it possible to guarantee the intervertebral spacing function.

  In the introduction configuration between the vertebrae, it is possible to pinch the wings of the band before 6421, to facilitate this operation. At the same time, the wings of the rear band 6422 are kept substantially parallel.

  Then, after introduction of the extra-disc stay, the intradiscal element 642 is deformed, until adopting its position of lordosis. In this latter configuration, the wings of the rear band 6422 are pinched, namely that they are close to each other. In the example of FIG. 13, two C-shaped folded strips have been used. However, as a variant, one and / or the other of these strips can be folded back on itself, the way of a loop. As a further variant, illustrated in FIG. 14, the intra-discal element 742 has a front band 7421 disposed in an inverted manner, namely that its free end joins the web of the rear band 7422 at a junction 7423. This embodiment is advantageous, especially during the introduction, since it avoids contact of the free ends of the band before 7421 with the vertebral bodies. FIG. 15 illustrates a further alternative embodiment, in which the intra-discal element 842 comprises a front band 8421, folded into a C shape whose end is open towards the front. In addition, there are two rear bands 8422, which are mutually secured, while also being secured to the front band 8421. Each rear band also has a shape of C, whose end is open to the rear. Alternatively, as in the previous embodiments, at least one of these strips may be in the form of a closed loop. Note further that, in top view, the two rear legs 8422 substantially form a V, similarly to the embodiment of Figure 7. The junction area 8423 between the different bands provides an intervertebral spacing function. In the insertion position of the intra-discal element, the wings of the front band 8421 are possibly brought closer to each other. In addition, after installation of the posterior stay, the wings of each back branch 8422 are plucked, namely close to one another, which thus defines the configuration of lordosis of this intra-discal element 842. FIG. 16 illustrates a further variant embodiment of the invention, in which the intra-discal element 942 firstly comprises a peripheral body 9421, forming a ring. There is also provided an intermediate wall 9422 connecting the opposite walls of the ring, so as to divide the latter into two approximately symmetrical portions. This intra-discal element 942 may be made of a suitable material, for example a slightly deformable plastic material. It will be noted that the presence of the intermediate wall 9422 makes it possible to limit the collapse in height of the element 942, while ensuring a damping function of the vibrations. In its introduction configuration, the element 942 has a substantially constant height, or possibly a slightly greater height at its rear portion. On the other hand, after placing the posterior stay, the rear part of this element 942 is slightly crushed. In this respect, the mechanical properties of the material constituting the element 942 are adjusted in order to allow controlled deformation and elongation of the latter.

  Figures 17A to 17C illustrate a further alternative embodiment of the invention. This variant is more particularly its application in the case where the vertebrae have suffered a very significant collapse. This situation is illustrated in FIG. 17A, where it can be seen that the adjacent vertebral bodies 12 and 22 are considerably closer together, resulting in a sharp decrease in the volume of the intervertebral space. In this embodiment, it firstly uses a flexible body 100 whose function is to ensure the filling of this intervertebral space. Such a flexible member is for example made of a silicone-type elastomer or a composite material. Such a flexible member is deformable, while being substantially non-compressible. Under these conditions, it is first of all to introduce this flexible body into the intradiscal space 10 by any appropriate means, as shown in Figure 17B, which ensures a filling of the cavity of the degenerative disc. This fill, type stuffing, is intended to allow the extension of the disc cavity under pressure, so as to put in tension all the peripheral elements of the disc, and in particular the hinge anterior 11. Moreover, this operation s accompanied by a release of the lateral foramens and the nerve root they surround, which induces a spacing effect, spacer type. Once the flexible body 100 is put in place, it is then possible to implant the pedicle screws, the ligaments and the or each elastic pad (not shown in FIGS. 17), as described above, which leads to the reversible deformation of the body 100. There is therefore an association of three elements. Firstly, spacing and pressurization of a cavity that is still partially closed but collapsed, then a rear closure by guying so as to obtain the lordosis necessary for the intra-discal imprisonment of the flexible body, as well as a good erect position of the patient. The use of the flexible body 100 is particularly advantageous, especially in the case of a disc that has collapsed very significantly. Indeed, in the absence of such a flexible body, this collapse would make it very difficult the guying provided by the ligament, which would no longer manage to lordose the joint to stabilize it. In other words, the establishment of a ligament in the absence of the flexible body 100 would require applying a very high tension on this ligament, which would generate additional mechanical stresses on the facets and foramens already shrunk .

  The introduction of the flexible body 100 in the intraluminal cavity first ensures a filling of the latter, which again guarantees an acceptable intervertebral height, for the establishment of ligaments. It will be noted that the posterior bracing, provided by these ligaments, finds its stability by re-tensioning all the ligamentary elements remaining intact, while resting on the intradiscal flexible member in a three-point type system. The use of this flexible member also has the advantage of absorbing shocks and vibrations.

  Finally, it should be noted that the main function of the flexible body 100 is to ensure a filling of the extra-disc space, and the pressurization of this space as in the physiology of the disc where this pressure is hydraulic type, thus creating the spacing effect necessary for therapy. Since this flexible body is deformable, it is likely to switch to lordosis by responding to the mechanical stresses of the posterior guying, especially for osteosynthesis respecting the balance of a biped erect position. In these conditions, the structure of this flexible body is much simpler than that of a partial or total disc prosthesis, which generally includes components of different natures, which are animated by friction, sources of wear. In addition, the implementation of these pro-theses requires surgery by anterior route, with destruction of the peripheral ligaments, in particular of the anterior hinge, which are the only elements of residual stability in this degenerative context. As has been explained in the various embodiments above, the intra-discal element according to the invention has two different configurations, respectively corresponding to its intervertebral insertion and its deformation in lordosis after placement of the posterior stay . Furthermore, in all these embodiments, this intra-discal element is likely to pass reversibly from one to the other of its two configurations, in particular thanks to the nature of its constituent material.

Claims (9)

  Intervertebral stabilization assembly for arthrodesis, intended to connect at least two neighboring vertebrae (VI, V2), comprising: at least one extra-disc element (40) intended to be disposed behind the intervertebral space (10), which is capable of substantially preventing any displacement between two adjacent vertebrae at least in the direction of the intervertebral flexion, and - at least one intra-discal cage-type element (42; 42a, 42b; 142; 242; 342; 442; 542; 642; 742; 842; 942), adapted to provide an intervertebral spacing function, this cage having a first insertion configuration between the two adjacent vertebrae, in which this cage cooperates with the vertebrae placed in an insertion position, this cage further having a configuration of lordosis, different from its introduction configuration, in which it cooperates with the vertebrae also placed in a configuration d it is placed in lordosis, the intra-discal element being able to deform in a reversible manner between its introduction configuration and its configuration of lordosis.   2. stabilization assembly according to claim 1, characterized in that each intra-discal element (42; 142; 242; 342; 542) is formed by a band of folded material, in particular having a shape of C or a form of loop this folded material web being adapted to reversibly deform between the introducer configuration and the lordosis configuration.   3. Stabilization assembly according to claim 1, characterized in that each intra-discal element (642; 742; 842) comprises: - a front element (6421; 7421; 8421) formed by at least a first band of folded material at least one rear element (6422; 7422; 8422) formed by at least one other folded material web adapted to be reversibly deformed between the introduction configuration and the lordosis configuration, and a mechanical junction zone (6423; 7423; 8423) between the front and rear elements, allowing intervertebral spacing to be maintained.   4. stabilization assembly according to the preceding claim, characterized in that there is provided a single front element (8421), and two rear elements (8422) forming a V seen from above.   Stabilization assembly according to claim 3, characterized in that the intra-discal element (942) comprises a loop-shaped main body (9421) and a reinforcing wall (9422) connecting two zones distant from each other. this body.   6. stabilization assembly according to any one of the preceding claims, characterized in that the intra-discal element (142) is provided with abutment means (143) adapted to limit the amplitude of its movement, during the passage of the introductory configuration to the lordosis setting.   7. stabilization assembly according to any one of the preceding claims, characterized in that the or each extra-discal element (40) cooperates with two pedicle screws (14, 24) implanted in two adjacent vertebrae, and this extra-discal element has at least one, in particular three degrees of freedom in rotation relative to each of these pedicle screws.   8. stabilization assembly according to any one of the preceding claims, characterized in that the intra-discal element is a flexible body (100) intended to be placed in the intradiscal space so as to fill the latter.   9. stabilization assembly according to claim 8, characterized in that the flexible body (100) is deformable, while not substantially not compressible.