FR2861980A1 - Implant system for spinal vertebrae has locking element with surfaces able to engage with anchoring screw threads - Google Patents

Abstract

The system, designed to join a number of vertebrae together, consists of an implant (1) with one or more holes (2) for anchoring screws (110) and locking elements (120). The locking elements are in the form of elastically-deformable rings with surfaces that are able to co-operate with the threads (113) of the anchoring screws and external ribs that clip into the holes. The system, designed to join a number of vertebrae together, consists of an implant (1) with one or more holes (2) for anchoring screws (110) and locking elements (120). The locking elements are in the form of elastically-deformable rings with surfaces that are able to co-operate with the threads (113) of the anchoring screws and external ribs that clip into the holes. The implant and/or fixings can be made from a biocompatible metal such as stainless steel or titanium, or from a polymer.

Description

TECHNICAL FIELD TO WHICH THE INVENTION REFERS

  The present invention relates generally spinal implant systems for securing to one another several vertebrae.

  It relates more particularly to an implant system comprising an implant provided with at least one through opening and means for fixing said implant to a vertebra which comprises, on the one hand, an anchoring screw adapted to pass through said through opening for to be screwed into the vertebra, and, secondly, a locking member adapted to be placed in said through opening to be interposed between the anchor screw and said implant.

  The invention finds a particularly advantageous application in the production of a cervical plate serving to immobilize several vertebrae.

BACKGROUND

  US Pat. No. 5,954,722 discloses an implant system of the aforementioned type in which the implant is a cervical plate which accommodates in each of its through openings a resilient locking ring internally provided with a tapping intended for cooperating with a thread provided on the outer lateral surface of the head of an anchor screw engaged through said corresponding through opening of the cervical plate.

  According to this document, each elastic locking ring is forced into each through opening of the cervical plate so that the outer lateral surface of said ring comes to bear against the spherical side wall complementary to said through opening and retains by friction said ring within said through opening. When the head of the anchor screw is screwed into said ring, it causes the elastic expansion of said ring so as to accentuate this retention by friction of the ring in said through opening.

  The main disadvantage of this spinal implant system is that the force setting of the locking ring in said through opening, before the introduction of the anchor screw through said through opening for its anchoring to a vertebra, is not an easy operation for the surgeon.

  In addition, the frictional retention of the locking ring within the through opening of the implant after the anchor screw has been screwed into said vertebra does not prove to be an effective restraining means in case of an accidental movement of the anchor screw due for example to a disintegration of the bone portion located around the threaded body of said screw. Indeed, under the axial thrust force generated by the recoil movement of the anchor screw, the integral locking ring of the head of the anchor screw can partially out of its housing in the implant which can generate a detrimental game in the connection of the vertebrae considered.

  Furthermore, US Pat. No. 5,931,838 discloses another implant system as defined in the introduction in which the locking member is an elastic ring attached to an annular groove provided on an unthreaded portion of the body of the anchor screw. This elastic ring embedded on said anchoring screw being adapted, during the introduction of the anchoring screw through said through opening to be screwed into the vertebra, to deform elastically to come to wedge against a shoulder of the sidewall of said through opening to axially retain the anchor screw within the latter.

  The major disadvantage of such an implant system lies in the weakness of the retaining means by interlocking the elastic ring on the body of the anchor screw.

  OBJECT OF THE INVENTION In order to overcome the aforementioned drawbacks of the state of the art, the invention proposes an implant system as defined in the introduction, characterized in that the locking member comprises, on the one hand, screwing means adapted to cooperate with the thread of the anchor screw, and secondly, clipping means in said through opening of the implant.

  Thus, advantageously, in case of accidental recoil movement of the anchor screw screwed into the vertebra, due for example to a disintegration of the bone surrounding the threaded body of the anchor screw, the implant system according to the invention. The invention comprises a double level of means for retaining said screw within the implant. The first level of retaining means lies in the cooperation of the screwing means of the locking member with the thread of the anchoring screw to make the anchoring screw and the locking member integral, and the second level of retaining means lies in the clipping of the locking member in said through opening of the implant to effectively retain said locking member within said implant.

  Other non-limiting and advantageous features of the implant system according to the invention are the following: said means for clipping the locking member comprise an axial support means adapted, after introduction of the locking member into said through opening, to abut against an axial bearing means of the implant, one of the two axial support means being able to retract relative to the other during the introduction of the locking member in through opening; said axial bearing means of the locking member is a rib which projects from the external lateral surface of the locking member; said axial bearing means of the implant is a flange which borders the inlet of said through opening; said rib is rigid and is attached to an elastically deformable portion of the locking member; said flange is capable of flexing elastically as the blocking member passes through the inlet of said through opening; the locking member is an elastically deformable washer; the washer constituting the locking member is split; the locking member has a spherical outer lateral surface of which only a part is intended to slide on a seat of complementary spherical shape formed in the implant at the outlet of said through opening; said through opening comprises an inlet, a median part and an outlet, said median part being delimited by a lateral wall arranged so that when the blocking member is placed in said through opening, there is a clearance between said side wall and said outer lateral surface of the locking member; - The screwing means of the locking member comprises a primer which protrudes from the inner side surface of the locking member and adapted to cooperate with a thread of the thread of the anchoring screw; the internal lateral surface of the locking member locally forms a seat of frustoconical shape adapted to receive a frustoconical portion of the external lateral surface of the head of the anchoring screw; said primer is issued from the frustoconical portion of said internal lateral surface of the locking member; the implant is a cervical plate provided with several through openings, each accommodating a fixing means; and the implant and / or the fixing means are advantageously made of a biocompatible metallic material such as a titanium or stainless steel alloy or a polymeric material such as polyaryletheretherketone.

  DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

  The following description with reference to the accompanying drawings, given as non-limiting examples, will make it clear what the invention consists of and how it can be achieved.

  In the accompanying drawings: FIG. 1 is a diagrammatic view from above of an implant system according to the invention attached to two vertebrae of a spine; FIG. 2 is a schematic perspective exploded view of a preferred embodiment of a fastening means of the implant system of FIG. 1; - Figure 3 is a schematic perspective view from below of a locking member of the fixing means of Figure 2; Figure 4 is a partial schematic perspective view of the cervical plate of the implant system of Figure 1 with the locking member of Figure 3 positioned above a through opening of said cervical plate; Figure 5 is a simplified schematic perspective view of the cervical plate of the implant system of Figure 1 with a locking member inserted into each of its through openings; Figure 6 is a sectional view along the plane A-A of Figure 5; - Figure 7 is a sectional view along the plane B-B of Figure 8; Figure 8 is a schematic perspective view from below of a portion of the implant system according to the invention; and Figure 9 is a view identical to that of Figure 7 wherein the anchor screws are fully engaged in the locking members housed in the corresponding through openings of the cervical plate.

  FIG. 1 shows an implant system comprising a cervical plate 1 fixed on two vertebrae V by four fixing means 100.

  For this purpose, the cervical plate 1 has four through openings 2 in each of which engages the head of the anchoring screw of a fixing means 100 which will be described in more detail below.

  In addition, here the cervical plate 1 has two openings 6 of smaller diameter than the through openings 2.

  These openings 6 of smaller diameter are intended to accommodate rods (not shown) to maintain the cervical plate 1 in position on the vertebrae V during the drilling phase of the holes for receiving the anchoring screws of the fastening means 100.

  Figures 2 to 9, there is shown a preferred embodiment of a fastening means 100 for fixing the cervical plate 1 on the vertebrae V. This fastening means 100 comprises an anchoring screw 110 of X axis provided with a threaded body 112 and a head 111 overlying the body 112.

  As shown more particularly in Figures 7 to 9, the body 112 of the anchoring screw 110 is able to pass through a through opening 2 of the cervical plate 1 to anchor in the vertebra V considered.

  The head 111 of the anchor screw 110 is intended to be housed in said through opening 2 to press the cervical plate 1 against the vertebra V. Here, the head 111 of the anchoring screw 110 has a generally cylindrical shape of revolution around the axis X with, in its center, a blind hole 114 axial to accommodate the tip of a gripping and screwing tool. According to the example shown, the blind hole 114 is delimited by a hexagonal side wall. At its base, the head 111 of the anchoring screw 110 has a frustoconical portion 111A (see Figure 7).

  In addition, the fixing means 100 comprises a locking member 120 adapted to be placed in the through opening 2 to be interposed between the anchoring screw 110 and said cervical plate 1.

  More particularly, the locking member 120 is able to be interposed between the head 111 of the anchor screw 110 and the side wall 3, 5 of the through opening 2 of the cervical plate 1 in which the head 111 is engaged. anchoring screw 110 for holding said head 111 in said through opening 2 after anchoring the anchor screw 110 in the vertebra V (see Figure 9).

  Advantageously, and according to an essential characteristic of the implant system according to the invention, the locking member 120 comprises, on the one hand, screwing means capable of cooperating with the thread 113 of the anchoring screw 110, and on the other hand, clipping means in said through opening 2 of the cervical plate 1.

  Said clipping means of the locking member 120 comprise an axial bearing means 121A adapted, after introduction of the locking member 120 into said through opening 2, to abut against an axial bearing means 4 of the cervical plate 1, one of the two axial support means being able to retract relative to the other during the introduction of the locking member 120 in the through opening 2.

  According to the embodiment shown in the figures, said axial support means of the locking member 120 is a rib 121A which protrudes from the external lateral surface 121 of the locking member 120. This rib 121A is rigid and is attached to an elastically deformable portion of the locking member 120.

  Preferably, the locking member 120 is an elastically deformable washer whose outer lateral surface 121 is of spherical shape. This washer is slotted with a slot 124 extending along the axis X 'of the washer (see FIG. 6) to increase the elastic deformation capacity of said washer.

  The axial bearing means of the cervical plate 1 is an annular flange 4 which borders the inlet of said through opening 2 (see FIG. 6). This flange 4 extends transversely to the Y axis of said through opening 2 so that the latter has a reduced inlet section.

  Here, the flange 4 of the cervical plate 1 is rigid, but according to an alternative embodiment not shown it can be provided that the locking member is elastically deformable and that said flange is able to flex elastically during the passage of the body of blocking through the inlet of said through opening to allow said protruding rib to project from the outer lateral surface of the locking member.

  Said through opening 2 of the cervical plate 1 comprises, in addition to a reduced-section entrance bordered by the rim 4, a middle portion and an outlet.

  The middle portion of said through opening 2 is delimited by a side wall 3, here cylindrical of revolution about the axis Y, arranged so that when the locking member 120 is placed in said through opening 2 there is a gap between said side wall 3 and said external lateral surface 121 of the locking member 120.

  More particularly, as shown in Figure 6, the diameter of the through opening 2 taken at its middle portion is slightly greater than the outer diameter of the locking member 120, at most, it is identical to the external template of the locking member 120 not resiliently retracted, so that when the latter is introduced into said through opening 2, it does not bear against said side wall 3 thereof.

  As shown in Figures 6, 7 and 9, the outer spherical surface 121 of the locking member 120 has a portion for sliding on a seat 5 of complementary spherical shape formed in the cervical plate 1 at the exit of said opening through 2.

  Thus, by a ball-and-socket effect, the locking member 120 can take different angular orientations in said through-opening 2 of the cervical plate 1 so as to be able to introduce the anchoring screw 110 associated in an inclined manner with respect to the Y axis. of said through opening 2. The angle of inclination formed between the X axis of the anchor screw 110 and the Y axis of the through opening 2 may be at most about 10 degrees (see FIGS. and 9).

  Moreover, according to the preferred embodiment shown in the figures, the screwing means of the locking member 120 comprise a primer 123 which projects from the internal lateral surface 122 of the locking member 120 and which is able to cooperate with a thread 113A of the thread 113 of the anchoring screw 110.

  As shown more particularly in FIGS. 2 and 6, the internal lateral surface 122 of the locking member 120 comprises several sections, including: a first frustoconical section 122A which forms, starting from an edge 120A of said locking member 120, a flared entrance to facilitate the introduction of the anchoring screw 110 through said blocking member 120, a second portion 122B of cylindrical revolution about the axis X 'of the locking member 120 whose section is equal to the play near to that of the head 111 of the anchoring screw 110, a third frustoconical section 122C which locally forms a seat adapted to receive in abutment the frustoconical portion 111A of the external lateral surface of the head 111 of the anchoring screw 110, and - A fourth section 122D of cylindrical revolution about the axis X 'of the locking member 120 which adjoins the other edge 120B of the locking member and which allows the body 112 of the anchor screw 110 out of said block member age 120.

  Said primer 123 of the locking member 120 comes from the third frustoconical section 122C of said internal lateral surface 122 of the locking member 120.

  In fact, the fourth cylindrical section 122D of the internal lateral surface 122 of the locking member 120 is formed during a recovery operation performed on said third frustoconical section 122 so as to open the outlet section of said locking member for allow the threaded body 112 of the anchor screw to pass through said outlet section.

  During this recovery step part of this third truncated conical section 122C is not milled or machined to produce said primer 123 which forms a projection or an advance in the outlet section of the locking member 120 adapted to cooperate with the threading 113 of the anchoring screw 110 to the passage of its body 112 through said locking member 120.

  The establishment of the attachment means 100 described above of the cervical plate 1 is carried out as follows.

  The cervical plate 1 and the blocking member 120 are assembled, before being used by the surgeon, by clipping the blocking member 120 into the corresponding through opening 2 of the cervical plate 1.

  To clip the locking member 120 is clamped so as to close its slot 124 and reduce its section to allow its introduction through the inlet section of said through opening 2. In fact, this pinch of the organ blocking 120 makes it possible, when the latter passes through the inlet of the through opening 2, to retract the rib 121A which it carries relative to the flange 4 bordering said inlet of the through opening 2.

  When the locking member 120 is introduced into said through opening 2 of the cervical plate 1, it elastically relaxes to return to its original configuration because the cross section of the middle portion of said through opening 2 is greater than or equal to close to that of the non-retracted locking member 120. The locking member 120 then does not rub against the side wall 3 of the through opening 2 but is retained within said through opening 2 by abutting its rib 121A (forming an axial bearing means) against the rim 4 of the cervical plate 1 (forming another axial support means).

  The surgeon receives the cervical plate 1 equipped with the locking members and places it on the vertebrae to be immobilized.

  Before introducing the anchoring screw 110 into the hole he has drilled in the vertebra considered, he can rotate the locking member 120 in the through opening 2 of the cervical plate 1 by sliding its surface outer spherical side 121 against the seat 5 of spherical shape provided at the outlet of said through opening 2 of the cervical plate 1 so as to orient the axis X 'of said locking member 120 according to the orientation chosen for the anchor screw 110 to anchor in the vertebra V. Then the surgeon screws the anchor screw 110, oriented at the selected inclination, through the locking member 120 to anchor it in the vertebra V considered. As it passes, the thread 113 of the threaded body 112 of the anchoring screw 110 hooks on said primer 123 of the locking member 120. The screwing of the anchoring screw 110 into the locking member 120 does not causes no expansion of the locking member 120 which is retained within the through opening 2 only by the abutment of its rib 121A forming a means of axial support against the flange 4 of the cervical plate 1 forming the other means of axial support.

  At the end of screwing, the head 111 of the anchoring screw 110 is housed in the locking member 120 and the frustoconical portion 111A of its external lateral surface provided at the base of said head 111 bears against the third section 122C frustoconical of the inner lateral surface 122 of the locking member 120.

  This support of frustoconical surfaces allows the anchoring screw 110 to correct a slight orientation defect of the locking member 120 by slightly rotating it in the through opening 2 to place its axis X 'according to the inclination of the X axis of the anchor screw 110.

  In this state, the anchoring screw 110 secures the cervical plate 1 to the vertebra, the head 111 of the anchor screw 110 housed in the locking member 120 pressing the cervical plate 1 against the vertebra V. The net 113A provided at the base of the head 111 of the anchoring screw 110 is attached to the primer 123 of the locking member 120 so that the anchoring screw 110 and the locking member 120 form a fixed assembly retained at within the cervical plate 1.

  In case of disintegration of the bone provided around the threaded body 112 of the anchoring screw 110, any recoil movement of said anchoring screw 110 causing the exit of the head 111 of the screw from the cervical plate 1 is this is avoided, on the one hand, by the cooperation by screwing of said anchoring screw 110 with the locking member 120, and, on the other hand, by the retention of the locking member 120 within the through opening 2 by the abutment cooperation of the axial bearing means that constitute here the rib 121A and the flange 4.

  Of course, the various elements described above of the implant system according to the invention are advantageously made of a biocompatible metallic material such as a titanium or stainless steel alloy or a polymeric material such as polyaryletheretherketone. In particular, the spring washer constituting the locking member is made by machining and milling.

  The present invention is not limited to the embodiment described and shown, but the art can apply any variant within his mind.

Claims (15)

  An implant system comprising an implant (1) provided with at least one through opening (2) and means (100) for attaching said implant (1) to a vertebra (V) which comprises, on the one hand, an anchoring screw (110) adapted to pass through said through opening (2) to be screwed into the vertebra (V), and, secondly, a locking member (120) adapted to be placed in said through opening ( 2) to be interposed between the anchoring screw (110) and said implant (1), characterized in that the locking member (120) comprises, on the one hand, screwing means able to cooperate with the threading (113) of the anchor screw (110), and secondly, clipping means in said through opening of the implant.   2. Implant system according to claim 1, characterized in that said clipping means of the locking member (120) comprise an axial support means adapted, after introduction of the locking member (120) in said through opening (2), to abut against an axial support means of the implant (1), one of the two axial support means being able to retract relative to the other during the introduction of the locking member (120) in the through opening (2).   3. Implant system according to claim 2, characterized in that said axial support means of the locking member (120) is a rib (121A) which projects from the external lateral surface (121) of the locking member (120).   4. Implant system according to one of claims 2 or 3, characterized in that said axial bearing means of the implant (1) is a flange (4) which borders the inlet of said through opening (2). ).   Implant system according to one of claims 3 or 4, characterized in that said rib (121A) is rigid and is attached to an elastically deformable portion of the locking member (120).   6. Implant system according to claim 4, characterized in that said flange is able to flex elastically to the passage of the locking member through the inlet of said through opening.   7. Implant system according to one of claims 1 to 6, characterized in that the locking member (120) is an elastically deformable washer.   8. implant system according to claim 7, characterized in that the washer constituting the locking member (120) is slotted.   9. Implant system according to one of claims 1 to 8, characterized in that the locking member (120) has a spherical outer lateral surface (121) of which only a part is intended to slide on a seat (5). ) of complementary spherical shape formed in the implant (1) at the outlet of said through opening (2).   10. Implant system according to one of the preceding claims, characterized in that said through opening (2) comprises an inlet, a median portion and an outlet, said median portion being delimited by a side wall (3) arranged so that when the locking member (120) is placed in said through opening (2) there is a clearance between said side wall (3) and said outer lateral surface (121) of the locking member (120).   11. Implant system according to one of the preceding claims, characterized in that the screwing means of the locking member comprises a primer (123) which projects from the internal lateral surface (122) of the organ of blocking (120) and adapted to cooperate with a thread of the thread (113) of the anchor screw.   12. Implant system according to one of the preceding claims, characterized in that the inner side surface (122) of the locking member locally forms a frustoconical shaped seat adapted to receive in abutment a frustoconical portion (111A) of the outer lateral surface of the head (111) of the anchor screw (110).   13. Implant system according to claims 11 and 12, characterized in that said primer (123) is derived from the frustoconical portion (122C) of said inner lateral surface (122) of the locking member (120).   14. Implant system according to one of the preceding claims, characterized in that the implant (1) is a cervical plate provided with a plurality of through openings (2) each receiving a fixing means (100).   15. Implant system according to any one of the preceding claims, characterized in that the implant and / or the fixing means are advantageously made of a biocompatible metallic material such as a titanium alloy or stainless steel or a polymeric material such as polyaryletheretherketone.