FR2805457A1 - INTERVERTEBRAL IMPLANT A BODY AND FACE SUPPORT - Google Patents

Abstract

The invention concerns an intervertebral implant comprising a rigid body having two support surfaces on the end-plates of two adjacent and elastically deformable vertebrae, enabling to bring the two support surfaces closer together, and a cavity for receiving a block of material.

Description

The present invention relates to vertebral binding systems.

In the case of disc diseases, a therapy that is often used consists essentially of performing osteosynthesis by using rigid cages having an open cavity towards the upper and lower vertebrae, capable of receiving bone graft or any other substance that promotes bone regrowth. On the other hand, it is recognized the bone regrowth to obtain the desired fusion is stimulated and accelerated proportionally to the constraints experienced by the graft. However, beyond a certain limit, the stresses become too great and thus have an opposite effect on the quality of the bone regrowth, or even the necrosis of the bone tissues. The currently existing cages absorb almost all stresses without deformation because of their high rigidity. Thus, the graft is almost not stimulated, which does not allow to have the best conditions for obtaining a merger. This is the case of the implant described in WO97 / 37620. This document describes a cage-plate having a rigid open body of globally parallelepipedal or ovoid shape intended to receive graft with open upper and lower faces. The materials used to manufacture such implants do not allow optimization of the fusion.

On the other hand, this type of implantable cage does not allow the surgeon the opportunity to choose the restoration of a certain mobility between the two instrumented vertebrae in place of fusion. Indeed, in some cases, it is more sensible to restore mobility to the pathological vertebral stage than to perform arthrodesis. This is the case for young patients and / or having vertebral bodies in excellent condition, where the subsequent reoperation is certain stages adjacent to the instrumented stage, if performing a fusion.

An object of the present invention is to provide an implant ensuring optimized bone fusion and to allow the choice between this fusion and a restoration of mobility.

In order to achieve this goal, according to the present invention an intervertebral implant comprising a rigid body having two bearing faces on the trays of two adjacent vertebrae and elastically deformable before receiving the block, allowing to bring the two faces closer together. support one another, and a receiving cavity of a block of material.

Thus, in the case of a fusion, the deformability of the body allows a better fusion because the constraints will be better distributed between the structure and the graft. In the case of a mobility restoration, deformability of the body allows the implant to ensure it.

Advantageously, the body is in one piece. Advantageously, the body comprises a folded blade forming bearing faces.

Advantageously, the blade has a non-uniform thickness along the blade. Thus, the deformation of the body is optimized for use of the implant and for the deformation sought.

Advantageously, the blade defines less part of the cavity.

Advantageously, the body has an area of anointing support faces.

Advantageously, the junction zone and the bearing faces give the body a U-shaped profile. Advantageously, at least one of the bearing faces comprises a profile adapted and complementary to the profile of the vertebral plate with which it is intended to come into contact.

Advantageously, the body comprises means for anchoring one side of the vertebrae contiguous vertebral plateau.

Advantageously, the body comprises at least two anchoring tabs to the respective vertebrae, each tab extending in continuity of material with only one of the support faces.

Advantageously, each tab extends in continuity of material with the support surface intended to be resting on the plate of the vertebra associated with this tab.

Advantageously, each tab extends in continuity of material with the bearing surface intended to be supported on the vertebral plate associated with the other leg.

Advantageously, each fixing lug comprises at least one orifice intended to receive a bone screw. Advantageously, the body comprises a block of non-rigid material.

Advantageously, the block comprises bone graft and / or any substance promoting bone regrowth.

Thus the implant can perform a fusion. Advantageously, the block comprises biocompatible polymer (s) and / or any other biocompatible viscoelastic material.

Thus, the implant acts as a disk prosthesis allowing the restoration of mobility.

On the other hand, there is provided a method of implantation of the implant comprising an approach of the spine in an anterior way, a discectomy, an advancement of the lower and upper trays of the disc space, a verification of the dimensions of the spine. disc space, the choice of the next block type that is desired fusion or restoration of mobility, insertion of the implant in the prepared disc space, anchoring of the implant on vertebral bodies, closure of the way first.

Other features and advantages of the invention will become apparent from the following description of a preferred embodiment of a variant given as non-limiting examples. In the accompanying drawings, FIG. 1a is a perspective view of the implant according to the invention according to a first embodiment; FIG. 1b is a view from above of the implant according to the first embodiment; - Figure 2 is a perspective view of one of the screws to Figure 1; FIG. 3 is a perspective view of a block according to the first embodiment; - Figure 4 is a perspective view of the body according to the first embodiment; Figure 5 is a side view of the body according to the first embodiment; FIG. 6 is a body perspective view according to a second embodiment; Figure 7 is a side view of the body according to the second embodiment; - Figure 8 is a side view in a sagittal plane of a cervical vertebra.

With reference to FIGS. 1a to 5, the implant 1 comprises a body 2 elastically deformable, a block 3 included within the body 2 and bone screws 4 fixing.

The body 2 is formed of a blade describing a path resembling a. The loop of the a comprises a lower bearing face 10, a posterior wall 11 connecting the face 10 to an upper bearing face 12, the assembly describing a U-shape. The bearing faces 10, 12 are opposite to each other and generally extend in two planes parallel to each other. This loop is of generally parallelepipedal shape to fill the disc space as much as possible. This loop defines a cavity 20 which is able to receive the block 3. This block 3 may consist of either bone graft or any other substance that promotes bone regrowth such as bone substitutes, or a biocompatible polymer or any other biocompatible viscoelastic material. In the first case, the implant 1 will be used in order to obtain a fusion between the two instrumented vertebrae. The elastic deformability of the blade allows to obtain a distribution of stresses between the body 2 and the block 3 consisting of bone graft Thus the stresses supported by the graft allow the latter to produce a bone of better quality for fusion. In the second case, the implant 1 will be used in order to restore the mobility between the two instrumented vertebrae. The elastic deformability of the blade associated with the viscoelasticity of block 3 makes it possible to reproduce the mechanical reactions of the healthy natural vertebral disc replaced by implant 1.

The branches of the profile a of the body 2 comprise two lugs 13 extending the lower bearing surface 10 at right angles thereto and allowing the attachment of the implant 1 to the body of the upper vertebra, and a lug 14 extending the upper bearing surface 12 at right angles thereto and allowing the fixation of the implant on the body of the lower vertebra. From above, as shown in Figure lb, the tabs 13,14 are inclined relative to each other to be oriented to follow the curvature of the anterior wall of the vertebral bodies to which they are attached. Each of the lugs 13, 14 comprise at least one orifice 15 which is able to receive a bone screw 4 with a head 5 for fixation in the vertebral body. The orifice 15, of generally circular cross section preferably, comprises a surface 18 adapted to receive the head 5 of the bone screw 4. The surface 18 is substantially complementary to the surface 7 of the head 5 of the adjacent bone screw 4 to the threaded rod. On the other hand, each of the bone screws 4 comprises processing means 8 in the form of a cavity recess of hexagonal section, a bone thread 6 and a notch 9 located at the opposite end of the head. 5, according to the axis of the screw that allows the self-tapping of the screw in the vertebral body.

The parts of the blade acting as lower and upper bearing faces 12 are shaped to conform as much as possible to the shape of the vertebral plates with which they are in contact. Thus, the implant is better stabilized in the disc space. In the embodiment shown in FIGS. 1a to 5, the bearing faces 10, 12 are shaped to fit the vertebral endplates of a cervical vertebra 40 shown in FIG. 8. The cervical vertebra 40 has a vertebral body 41 having an upper plate with a face 43 and a lower plate with a face 42. In section along the median sagittal plane in Figure 8, the upper plate 43 of the vertebra to a profile substantially straight horizontal whereas the lower plate 42 has a concave profile in the airplane wing complementary to the convex one of the upper plate 12 of the body 2 as described below. The lower bearing surface 10 of the body 2 is able to come into contact with the plate 43 of the vertebra 40. As a result, the lower bearing face 10 has a substantially horizontal straight profile in the sagittal plane. The upper bearing face 12 of the body 2 is able to come into contact with the plate 42 of the vertebra 40. As a result, the upper bearing face 12 has a profile consisting of two sections of generally rectilinear shape 16, 17 inclined relative to each other to give this profile a convex shape. The rear section 16 is longer than the two sections. It extends, in the sagittal plane, about 80% of the length of the body 2 The section 16 is slightly inclined towards the rear of the body 2. It is therefore slightly inclined relative to the face lower support 10. The section 17 is inclined towards the front of the body more strongly than the inclination of the rear section 16 towards the rear. Its length is approximately equal to a quarter of that rear section 16. The two sections 16,17 give the upper bearing surface 12 a profile close to that of an aircraft wing.

The bearing faces 10, 12 comprise at least one orifice 30 passing through the thickness of the blade, of preferentially circular section. This orifice 30 communicates the internal cavity 20 to the structure 2 with the bearing surface 12 or the bearing face 10. In the case of the choice of a fusion, this orifice 30 allows the progression of the fusion towards the trays 42.43 adjacent vertebrae. In the case of the choice of a mobility restoration, this orifice 30 makes it possible to strengthen the anchoring, since there is bone regrowth within the orifice 30 which will recomble it on the thickness of the blade. Preferably, the faces 10,12 include a plurality of orifices 30 of circular section and 'formally distributed on bearing faces 10, 12.

The deformation of the body 2 is controlled by the variations in the thickness of the blade along the profile described by the bearing face 12, the posterior wall 11 and the bearing face 10. Thus, the distribution of stresses between the body 2 and block 3 is optimized.

The cavity 20 capable of receiving the block 3. The choice of the composition of the block 3 depends on the will of the surgeon to obtain either a fusion between the two vertebrae as part of an arthrodesis, or to restore a mobility between the two vertebrae. In the first case, the block 3 will consist of bone graft and / or any other substance promoting bone growth. In the second case, the block 3 will consist of one or more biocompatible polymers or any other biocompatible viscoelastic material. The block 3 has an external surface complementary to that of the cavity for a perfect match with the shape of the cavity 20 which is delimited by the profile of the blade of the body 2: the surface 10a is complementary to the lower bearing face 10 of the 2. The surface 12a is complementary to the upper bearing face 12 of the body 2 and consists of two sections 16a, 17a complementary to the sections <B> 16,17 </ B> of the bearing face 12. From even, the surface 11a is complementary to the inner face of the posterior wall 11 of the body 2.

Implantation of the implant 1 into the body of the patient takes place through an anterior approach which allows direct access to the vertebral bodies, and on their anterior face. The practitioner performs a discectomy of the damaged intervertebral disc then brightens the lower trays of the superior vertebra, and superior of the lower vertebra delimiting the disc space. After verifying the size of this disc space thus cleared, practitioner prepares the implant 1 for implantation: if the practitioner decides to perform a fusion, he introduces into the cavity 20 a block 3 of graft and / or other substance promoting bone regrowth; if the practitioner decides to restore the mobility, he introduces into the cavity 20 a block 3 made of biocompatible polymer (s) or any other biocompatible viscoelastic material. Once prepared, the practitioner sets up the implant 1 which he fixes with the bone screws 4 to the vertebral bodies, through orifices 15 of the fixing lugs 13, 14. He then closes the way first.

In a second embodiment illustrated in FIGS. 6 and 7, the body 102 of the implant is always formed of a blade that describes a path resembling a U. It always has a lower bearing surface 110 similar to the previous bearing surface 10, a rear wall 111 similar to the previous wall 11, an upper bearing face 112 similar to the upper bearing surface 12 above. The attachment to the overlying vertebra is effected by a fixing lug 113 extending the upper bearing face 112. The attachment to the underlying vertebra is effected by two fixing lugs 114 extending the lower bearing surface. 110. The anchoring means are identical to those of the previous embodiment. The blade here has a U-shape and no longer a shape so that the two branches su U intersect, as in the previous mode. The U-shaped blade of the body 112 defines an identical cavity 20 capable of receiving the block 3. The implementation of this second embodiment does not differ from the implementation of the first embodiment.

blade can be replaced a helical spring adapted to receive a block of biomaterials in his soul.

bone screws may have a locking mechanism vis-à-vis the brackets to prevent their recoil.

Bone screws may be polyaxial with respect to mounting lugs.

Claims (16)

<U> Claims </ U> 1. Intervertebral implant comprising a rigid body (2; 102) having two bearing faces on the plates of two adjacent vertebrae a cavity (20) for receiving a block (3) of material, characterized in that the deformable body elastically before receiving the block, allowing to bring the two support faces of one another. 2. Implant according to claim 1 characterized in that the body is in one piece. 3. Implant according to claim 1 or 2 characterized in that the body comprises a folded blade forming the bearing faces. 4. Implant according to claim characterized in that the blade has a non-uniform thickness along the blade. 5. Implant according to claim 3 or 4 characterized in that the blade defines at least in part the cavity. 6. Implant according to one of claims 1 to 5 characterized in that the body has a junction zone of the bearing faces. 7. Implant according to claim characterized in that the junction zone and the bearing faces give the body a U-shaped profile. 8. Implant according to one of claims 1 to 7 characterized in that at least one of the bearing faces comprises a profile adapted and complementary to the profile of the vertebral plate with which it is intended to come into contact. 9. Implant according to one of claims 1 to 8 characterized in that the body comprises means for anchoring to one side of the vertebrae contiguous to the vertebral plateau. 10. Implant according to one of claims 1 to 9 characterized in that the body comprises at least two anchoring tabs to the respective vertebrae, each tab extending in continuity of material with only one of the bearing faces 11. Implant according to claim 10 characterized in that each tab extends continuously material with the bearing surface intended to be supported on the vertebra plate associated with this leg 12. Implant according to claim 10 characterized in that each tab extends in continuity of material with the bearing surface intended to be supported on the vertebral plate associated with the other leg. 13. Implant according to one of claims 10 to 12 characterized in that each fixing lug comprises at least one orifice for receiving bone screws. 14. Implant according to one of claims 1 to 13 characterized in that it comprises a block of non-rigid material. 15. Implant according to claim 14 characterized in that the block comprises bone graft and / or any substance promoting bone regrowth 16. Implant according to claim 14 characterized in that the block comprises biocompatible polymer (s) and / or any other biocompatible viscoelastic material.