FR2779941A1 - Intersomatic spinal implant with anchoring elements - Google Patents

Abstract

The implant consists of a body (4) with one or more moving anchoring elements (26) extending from a contact face (6) when actuated by a sliding cam (630). The cam has a threaded surface to interact in the manner of a nut and bolt with an actuator which is accessible from outside the implant body. In a variant of the design the implant can have two cams interacting with two anchoring elements operated by a single actuator.

Description

The invention relates to spinal interbody implants. We know

  according to document FR-2 727 003 a spinal interbody implant intended to be placed in place of an intervertebral disc after ablation, and comprising a body having two planar faces of contact with the adjacent vertebral bodies. It comprises two receptacles for receiving anchor screws, arranged so that the screws project from the respective contact faces so as to be anchored in the adjacent vertebral bodies. Each screw is inclined relative to the associated contact face because the screw head extends to an edge of the body so that it can be operated once the implant has been received between the vertebral bodies. However, the installation of the screws is difficult to perform due to the inclination of their axis. In addition, the positioning of the screws to optimize the quality of the anchoring cannot be improved without harming

accessibility.

  An object of the invention is to facilitate the operation of the anchoring elements and to optimize the anchoring. In order to achieve this goal, there is provided according to the invention a spinal interbody implant comprising a body and at least one anchoring element movable relative to the body to extend projecting from a contact face of the body with a vertebra, the implant comprising at least one cam movable relative to the body and able to move the anchoring element relative to the body by ramp effect with the anchoring element. Thus, the anchoring element is moved through the cam by acting on the latter. Since we no longer act directly on the anchoring element, we largely overcome the constraints linked to the accessibility of the anchoring element. Therefore, the operation of the latter is easier to perform during an intervention. In addition, since it is no longer necessary to make the anchoring element directly accessible, there are many ways to modify its positioning so that it performs its anchoring function as best as possible. Therefore, it facilitates the maneuver for the installation of the anchoring element while allowing

  improve the quality of anchoring.

  The implant according to the invention may also have any one or more of the following characteristics: - the anchoring element is movable to slide relative to the body; - The cam is able to move the anchoring element by cooperating with the body in a screw-nut connection; - The cam is able to move the anchoring element while being movable in rotation relative to the body; - The cam is able to move the anchoring element by sliding relative to the body; - The cam has a thread capable of cooperating in a screw-nut connection with an actuator for maneuvering the cam from outside the body; - The actuator is mounted movable in rotation on the body; - the cam is movably mounted to slide on the body; - The cam has one end providing a clearance face by reference to a direction of movement of the cam for its exit from the body; - The cam and the anchoring element are arranged so that the cam moves the anchoring element in two opposite directions of movement; - The implant comprises at least two anchoring elements capable of being moved by the same cam; - The implant comprises at least two anchoring elements and at least two cams able to move the respective anchoring elements; - The two cams are arranged so that their threads cooperate with a common actuator; - The anchoring element is inclined relative to a general plane of the contact face; - The anchoring element is perpendicular to a general plane of the contact face; - The implant comprises at least two anchoring elements able to extend projecting from the same contact face; - The two anchoring elements are inclined relative to a general plane of the contact face and not parallel to each other; - The implant comprises at least four anchoring elements capable of projecting from the same contact face and arranged in two rows defining directions of alignment parallel to each other; the implant comprises at least two anchoring elements capable of projecting from two respective contact faces of the body with a vertebra; the body has two contact faces with a vertebra and at least one recess extending from one to the other of the faces; - the contact face has a sawtooth transverse profile; and - a part of the anchoring element able to extend projecting from the contact face has undercut faces with respect to a sliding direction of

  the element towards the vertebra.

  Other features and benefits of

  the invention will also appear in the description

  following of five preferred embodiments given by way of nonlimiting examples. In the accompanying drawings: - Figures 1 and 2 are two perspective views respectively in the assembled and exploded state of an implant according to a first embodiment of the invention; - Figures 3 and 4 are two sectional views of the implant of Figure 1 during two respective stages of its installation; - Figure 5 is a view similar to Figure 4 showing the implant between two vertebrae; - Figures 6 and 7 are two views respectively in exploded perspective and in section of an implant according to a second embodiment of the invention; - Figure 8 is a perspective view of the cam of an implant according to a third embodiment of the invention; - Figure 9 is a sectional view of the cam of Figure 8 according to the plane IX-IX; - Figure 10 is a perspective view of an implant according to a fourth embodiment of the invention; - Figure 11 is a perspective view of the implant of Figure 10 with the upper part of the body removed; - Figures 12 and 13 are perspective views respectively in the assembled and exploded state of an implant according to a fifth embodiment of the invention; and - Figure 14 is a partial view in axial section of

  the cam and the screw of figure 13.

  A first embodiment of the implant will be described with reference to FIGS. 1 to 5. The implant 102 comprises a body 4 in the general shape of a rectangular parallelepiped flattened along a dimension so as to define two large upper and lower faces 6 and four side faces 8. The edges and corners of the body are rounded so as not to injure the tissues of the human body for which the implant is intended. The upper and lower faces 6 have a generally planar shape and a sawtooth or zigzag transverse profile, the tops of the teeth defining continuous edges parallel to each other. These edges ensure a good grip of the upper and lower faces 6 on the plates of the vertebral bodies of the destination vertebrae 9, as shown in FIG. 5. The body 4 has two through recesses 10 extending near two opposite edges of the body and from one to the other of the upper and lower faces 6 leading to these. In addition, each lateral face 8 has an orifice 12 opening into one of the recesses 10 midway between the two upper and lower faces 6. When the implant is placed, the recesses 10 are filled with graft which will thus be able to grow in the direction of the vertebral plates through the recesses 10 and the orifices 12. The body 4 has a cylindrical conduit 14 extending with its axis 16 from one to the other of two edges of the body opposite one to the other and distant from the recesses 10, parallel to a general plane of the upper and lower faces 6. The duct 14 opens at its two ends. In the vicinity of one distal of the ends, it has a section 18 of narrowed and threaded diameter. The rest of the duct 14 constitutes a smooth section 20 of larger diameter by

comparison with section 18.

  The body 4 has channels 22 of cylindrical shape extending from the section 20 to the upper and lower faces 6. All the channels 22 have an axis 24 which intersects the axis 16 of the section 20, here at right angles. There are twelve channels 22 here. They are divided into two groups of six channels 22. In each group, the six channels 22 are mutually parallel, coaxial in pairs, and located in the same plane including the axis 16. It is in such a plane that The cutting of Figures 3 and 4 has been carried out so that the six channels of a single group are visible in these figures. This plane is inclined relative to the general plane of the upper and lower faces 6 so that the axes 24 of the channels 22 are also. The inclinations are symmetrical and of the same value for the two groups of channels. In each group of six channels 22, three lead to the upper face 6 and three to the lower face 6. Each channel 22 which opens into the upper face 6 is coaxial with one of those of the same group which opens onto the lower face . In each group, the three channels 22 which open on the same face are spaced at the same pitch. Thus on each face 6, open channels 22 distributed in two rows defining directions of alignment parallel to each other, the channels of each row having

opposite inclinations.

  Each channel 22 receives, movable to slide in the channel, an anchoring element which is here a pin 26 having a smooth cylindrical body having at one end closest to the face 6 a point and at the other end a head with convex spherical face of greater radius than the radius of channel 22 and of greater width than the diameter of associated channel 22. The head is located in the section 20 and thus retains the pin 26 trapped against its total output by

the associated side 6.

  The implant comprises a cam 130 in the shape of a revolution about an axis coaxial with the axis 16. It has a face at a distal axial end

  cylindrical threaded 134 suitable for forming a screw connection

  nut with the section 18 of the body. At a proximal axial end 136, it has a head of larger diameter than the diameter of the section 20 of the body to come into abutment externally against the body. The head has a hexagonal imprint, for example hexagonal, to allow the cam 130 to rotate around its axis by means of a suitable tool.

such as a key.

  Between these two ends, the cam 130 has three wide cylindrical faces 138, three narrow cylindrical faces 140 with reference to the wide faces 138, and three frustoconical faces 142 inclined in the direction of the threaded distal end 134. These faces are alternated and distributed in three consecutive groups each comprising in the proximal-distal direction a wide face 138, a frustoconical face 142 and a narrow face, the frustoconical face 142 constituting a level transition between the two other faces. The lengths of the faces along the axis 16 are identical for each type of face. These lengths are adapted so that, with reference to FIG. 3, when the threaded distal end 134 of the cam is engaged with only the proximal end of the section 18, the heads of the pins 26 are in abutment on the narrow faces 140, each narrow face 140 being in contact with the heads of four pins 26 whose axes 24 are coplanar in a plane perpendicular to the axis 16, while with reference to FIG. 4, when the head of the cam 130 is in abutment on the body, the heads of the pins 26 are in abutment on the wide faces 138, each wide face 138 being in contact with the four aforementioned pins 26. The diameter of the narrow faces 140 is such that in the position of FIG. 3, which we will call "retracted position", the point of the pins 26 does not extend projecting from the associated face 6, or extends so moderately in projection that it does not significantly impede the installation of the implant 102 between the vertebral bodies. The diameter of the wide faces 138 is such that in the position of FIG. 4, which we will call "extended position", the pins 26 extend projecting from the face 6, for example on the quarter or a third of their length, and penetrate the associated vertebral body enough to prevent removal of the implant. The implant is placed as follows. After removal of an intervertebral disc, and after filling the recesses 10 with graft as mentioned above, the implant 102 is introduced between the vertebral bodies of the vertebrae 9 associated with the removed disc. The height of the body 4 of the implant corresponds to the thickness of the removed disc. The implant is introduced so that the threaded section 18 is substantially in the posterior position. The faces 6 extend opposite the respective vertebral plates,

  parallel to them and in contact with them.

  The implant is introduced in the retracted configuration of

Figure 3.

  Once the implant in its location, the head of the cam 130 located in the anterior position is operated using a key to rotate the cam around its axis 16. Taking into account the screw-nut connection between the distal end 134 of the cam and the section 18, the cam therefore follows a helical trajectory along its axis 16. For each group of four pins, the contiguous frustoconical face 142 comes progressively into contact with the heads of the pins and constitutes a ramp which , given its displacement towards the section 18, urges the four pins to make them slide towards the outside of the body. As their projecting extension, the pins 26 penetrate into the vertebral plates to anchor the implant in the vertebrae. The four pins 26 then come to bear on the adjoining wide face 138 and extend projecting from the respective faces 6, in the output configuration. At the end of the operation of the cam 130, the head of the cam bears against the body and its end

  distal 134 is at the distal end of section 18.

  In a variant of this first mode, the screw-nut connection between the cam 130 and the body 4 may be replaced by a snap or clipping immobilizing the cam relative to the body after a simple push on the cam parallel to its axis. The cam is then movable to slide relative to the body. It can then have transversely to its axis a

  non-circular section, for example rectangular.

  We will now describe a second embodiment of the implant with reference to Figures 6 and 7. The references of elements different from those of

  first mode have been increased by 100.

  In the implant 202, the body 4 has substantially the same configuration as in the previous mode, except that the wide, smooth section 20 constitutes the entire cam duct 14. The cam 130 is here replaced by a set of three cams 230 and a screw 250. The screw 250 has an operating head 236 forming a stop on the body, similar to that of the cam 130. The screw has a

threaded rod 252.

  The three cams 230 are identical to each other.

  Each cam 230 has a generally cylindrical shape. It has a threaded cylindrical conduit 253 capable of

  cooperate with the rod 252 according to a screw-nut connection.

  Each cam 230 has four grooves 254 associated respectively with one of the four pins 26 intended to be actuated by the cam. Each throat 254

  extends in a plane radial to the axis 16 of the cam.

  Each groove 254 has a shallow upper part 238, a lower part 240 deep with respect to the upper part, and an intermediate part 242 forming

  level transition between the upper and lower parts.

  The upper parts of the four grooves 254 of the same cam

  are contiguous to the proximal end of this cam.

  Each groove, perpendicular to the axis 16, has an arcuate profile open towards the outside and extending over more than a semicircle, of constant radius along the groove, the edges of the arc of circle being extended outwards at the level of the intermediate and lower parts by two flat sides parallel to each other. Each groove is adapted to receive in the axial direction by each end the head of the associated pin 26, by preventing the exit of the head in the radial direction to the cam. The bottom of each groove 254 constitutes a first ramp for sliding the associated pin 26 outwards when the cam slides towards the distal end of the duct 14. One advantage of this embodiment is that it is reversible. Indeed, the head of each pin 26 being trapped in the associated groove 254, the edges of this groove constitute a second ramp which makes it possible to replace the pin in the retracted position when the cam 254 slides towards

the proximal end of the canal.

  The assembly of the different parts of the implant is carried out as follows. After receiving the pins 26 in their conduits 22 of the body 4, one of the cams 230 is made to slide to the central position associated with the pins 26 in the middle of the row. For this, the cam 230 must "cross" the four pins 26 of one of the ends of the rows, for example the four pins 26 of the distal end if the cam is introduced by this end. This step is obtained by introducing the cam 232 into the distal end of the conduit 14 by inserting the pins 26 into the respective grooves 254. 30 The pins 26 being initially projecting, the cam is continued to be pushed towards the center of the conduit which , taking into account the ramp effects by the grooves, places the pins 26 in the retracted configuration. While continuing to push the cam, the pins exit through the distal end of the grooves in the lower part 240. We finish pushing the cam to introduce the pins from the center of the rows into the grooves 254 in the upper part 238 and finally get them to the lower part 240 of the cam. The cam 230 is then introduced in the same way to be placed in the distal position. Then the cam 230 intended to occupy the most proximal position is likewise introduced by the proximal end. All the pins 26 being in the lower part 240 of the grooves, in the retracted configuration, the screw 250 is screwed into the cams 230 for the

put in contact with these.

  After installation of the implant between the vertebrae, the screw 250 is pushed in the direction of the distal end of the conduit 14, which causes the cams 230 to slide in the same direction. By ramp effect on the bottom of the grooves 254, the pins then slide in their conduit to pass from the lower part 240 to the upper part and end up in the extended position. In view of the above-mentioned reversibility, by means of steps opposite to those used for assembly, it is therefore possible

  remove the implant from its location between the vertebrae.

  A third embodiment is illustrated in FIGS. 8 and 9. In this embodiment, where the different elements have references increased by, two parallel rows of pins 26 are associated with each face 6 but the pins, instead of being opposite each other from one row to another, are offset by half a step parallel to the direction of the row. In this embodiment, the cam 330 is in one piece. It has six grooves 354 extending circumferentially around the axis 16. Each groove 354 is divided into two symmetrical parts and

  diametrically opposite on either side of the axis 16.

  Each part has a bottom 342 in a spiral section around the axis 16, that is to say approaching the axis as one rotates around the axis. This bottom 342 has a circular arc profile in a plane radial to the axis 16. Each part has edges capable of holding a pin head 26 captive as mentioned above, except at the point where the bottom is highest view of introducing the head into the throat. At its highest part, each bottom is limited by a stop 347. The cam 330 has a cylindrical outer face 349 whose disjointed sections extend between the adjacent grooves 354. This face has a diameter smaller than that of the conduit 14 and making it possible to slide the cam 330 there to accommodate it in the conduit 14, while the pins 26 are in the output configuration. As before, it has an operating head 336 capable of

form a stop against the body 4.

  To assemble and mount the implant, the pins 26 are introduced into their channels, then the cam 330 is slid into the conduit 14, placing each pin 26 at

  the entry of one of the upper parts into the groove 354.

  The cam is then rotated about its axis. The head of each pin being held captive by the edges of the groove, these, by ramp effect, slide the corresponding pin in the direction of the axis 16 to place it in the retracted position. We can then introduce

the implant between the vertebrae 9.

  Once the implant in place between the vertebrae, the cam 330 is rotated about its axis in the opposite direction to the first rotation. By the ramp effect of the head of the pins against the bottom of the grooves 354, the pins are urged to slide towards the outside of the body. Here again, the implant allows reversible operation for its disassembly, the edges of the groove parts being configured as seen during assembly to produce a ramp effect capable of pulling the pins towards the axis 16 when the cam undergoes a

counterclockwise rotation.

  In the fourth embodiment, illustrated in FIGS. 10 and 11 with certain references increased by

  300,! E body 4 has in plan a general shape in half

  disc, limited by a flat side wall 8 intended to be in the posterior position and a side wall

  circular 8 intended to be in the anterior position.

  Each side wall 8 has orifices 12 opening into the recesses 10 as mentioned above. The body 4 this time comprises two upper 4a and lower 4b parts meeting along a joint plane parallel to the upper and lower faces 6 each carrying one of these faces 6, and fixed to one another by means of screws 5. The conduits 22 are still twelve in number but they are oriented with their axes

  perpendicular to the upper and lower faces 6.

  The cam duct 14 has a generally rectangular cross section perpendicular to its axis 16 and is defined for half by each part 4a, 4b of the body. Cam 430 has a rectangular male section

  corresponding to that of female conduit 14 receiving it.

  It is able to slide there along its axis. The cam has a general shape of a rectangular parallelepiped. The two longitudinal side faces 460 of the cam 430 each have six grooves 454 capable of receiving the pins 26 in their own right, respectively. To this end, the pins each have in place of their head a protrusion received in the groove, oriented towards the other row of pins, and giving them a general shape of "L". Each groove 454 has two flat faces or ramps 462, mutually parallel, perpendicular to the associated lateral face 460, and inclined relative to the sliding direction so that the end of the groove 454 closest to the associated face 6 is furthest from the end

proximal of the cam.

  The cam 430 has a threaded conduit passing through it along its axis. The implant 402 comprises a screw 450 having a threaded rod capable of cooperating in threaded connection with the cam 430. The screw 450 has a groove receiving a collar 466 secured to the body 4, so that the screw 450 is mounted so that it can rotate in the body while the cam 430 is movable to slide in the body. After installation of the implant 402 between the vertebrae 9 with the pins 26 in the retracted position, when the head 436 of the screw is operated, the rotation of the screw causes the cam 430 to slide in the direction of the distal end of the conduit 14, here blind, and by ramp effect on the faces 462 of the grooves oriented towards the associated face 6, the sliding of the pins 26 for their projection and

in the extended position.

  The operation of the implant 402 is still reversible, the faces 462 of the grooves oriented in the opposite direction to the associated face 6 being able to place the pins 26 in the retracted position when the cam

  430 slides towards the proximal end of the duct 14.

  In this case, the proximal end, associated with the screw head 436, opens onto the left part of the curved side wall 8. The pins 26 present here in the vicinity of their point, on their section intended to be projecting, circumferential grooves 70 having a tapered face relative to the direction of sliding of the pins for their projection and improving their anchoring by allowing growth

bone in the grooves.

  Figures 12 and 13 show a fifth embodiment with certain references increased by 400. The pins 26 are here four in number for each face 6 and are oriented as in the fourth embodiment. The grooves 562 are similar to those of the fourth mode but are oriented in the opposite direction so that the sliding of the cam 530 towards the distal end of the cam duct 14 produces the projection of the pins 26. The implant 502 has a screw 550 in screw-nut connection with the body 4 coaxially with the cam duct and able to push the cam 530 at its proximal end into its duct in

  S direction of the distal end of the conduit.

  Referring to FIG. 14, the proximal end of the cam has a cutout 572 capable of slidingly receiving the end of the screw 550 for its abutment on the cam 530. Between the bottom of the cutout and its edge, the cam 530 has a groove 574 having a flank 576 in relief with reference to the direction of sliding of the cam towards the proximal end of the conduit. This face 576 is for example an annular plane, perpendicular to the axis 16 of the cam and oriented in

  direction opposite to the proximal end.

  To remove the implant, the screw 550 is removed, then a tool capable of coming into abutment on the face 576 in clearance is inserted into the cam duct 14 to hang it and pull the cam towards the proximal end of the duct, which causes the pins 26 to be put in the retracted configuration. This embodiment avoids making a threaded conduit passing through the cam 530 right through. It therefore makes it possible to reduce the dimensions of the cam 530 and to increase that of the

recesses 10 receiving the graft.

Claims (22)

  1. Spinal interbody implant comprising a body (4) and at least one anchoring element (26) movable S relative to the body to extend projecting from a contact face (6) of the body with a vertebra (9 ), characterized in that it comprises at least one cam (130; 230; 330; 430; 530) movable relative to the body (4) and able to move the anchoring element (26) relative to the   body by ramp effect with the anchoring element.   2. Implant according to claim 1, characterized in that the anchoring element (26) is movable at   sliding relative to the body (4).   3. Implant according to claim 1 or 2, characterized in that the cam (130) is able to move the anchoring element (26) by cooperating with the body (4) following a screw-nut connection.   4. Implant according to claim 1 or 2, characterized in that the cam (330) is capable of moving the anchoring element (26) while being movable in rotation by relation to the body (4).   5. Implant according to claim 1 or 2, characterized in that the cam (230; 430; 530) is able to move the anchoring element (26) by sliding by relation to the body (4).   6. Implant according to any one of   Claims 1 to 5, characterized in that the cam   (230; 430) has a thread capable of cooperating in a screwed connection with an actuator (250; 450) to   operate the cam from outside the body (4).   7. Implant according to claim 6, characterized in that the actuator (450) is mounted movable in rotation on the body (4).   8. Implant according to any one of   claims 5 to 7, characterized in that the cam   (430; 530) is movably mounted to slide on the body (4). 9. Implant according to any one of   claims 5 to 8, characterized in that the cam   (530) has an end providing a face (576) in relief by reference to a direction of movement of the cam for its exit from the body (4).   10. Implant according to any one of   Claims 1 to 9, characterized in that the cam   (230; 330; 430; 530) and the anchor (26) are arranged so that the cam moves the anchor   (26) in two opposite directions of movement.   11. Implant according to any one of   Claims 1 to 10, characterized in that it comprises   at least two anchoring elements (26) capable of being   moved by the same cam (130; 330; 430; 530).   12. Implant according to any one of   Claims 1 to 11, characterized in that it comprises   at least two anchoring elements (26) and at least two cams (230) able to move the respective anchoring elements. 13. Implant according to claim 12 and one   any of claims 6 to 8, characterized in that   that the two cams (230) are arranged so that their   threads cooperate with a common actuator (250).   14. Implant according to any one of   claims 1 to 13, characterized in that the element   anchor (26) is inclined relative to a general plane of the contact face (6).   15. Implant according to any one of   claims 1 to 13, characterized in that the element   anchor (26) is perpendicular to a general plane of the contact face (6).   16. Implant according to any one of   Claims 1 to 15, characterized in that it comprises   at least two anchoring elements (26) able to extend   projecting from the same contact face (6).   17. Implant according to claim 16, characterized in that the two anchoring elements (26) are inclined relative to a general plane of the contact face (6) and not parallel to each other.   18. Implant according to any one of   Claims 1 to 17, characterized in that it comprises   at least four anchoring elements (26) capable of projecting from the same contact face (6) and arranged in two rows defining directions   parallel alignment between them.   19. Implant according to any one of   Claims 1 to 18, characterized in that it comprises   at least two anchoring elements (26) capable of projecting from two respective contact faces (6) of the body (4) with a vertebra (9).   20. Implant according to any one of   claims 1 to 19, characterized in that the body   (4) has two contact faces (6) with a vertebra (9) and at least one recess (10) extending from one to the other of the faces (6).   21. Implant according to any one of   Claims 1 to 20, characterized in that the face of   contact (6) has a sawtooth transverse profile.   22. Implant according to any one of   claims 1 to 21, characterized in that part   of the anchoring element (26) able to extend projecting from the contact face (6) has faces (70) in clearance with respect to a sliding direction of   the element (26) in the direction of the vertebra (9).