WO2005074824A1

WO2005074824A1 - Piece of equipment enabling osteosynthesis of cervical vertebrae

Info

Publication number: WO2005074824A1
Application number: PCT/IB2005/000336
Authority: WO
Inventors: Alex Autericque; Jean-Claude Huot; Bernard Villaret
Original assignee: Medicrea Technologies
Priority date: 2004-01-27
Filing date: 2005-01-21
Publication date: 2005-08-18
Also published as: FR2865374A1; FR2865374B1

Abstract

This equipment (1) is characterized in that it comprises: - at least two vertebra-supported platelets (2) , each exhibiting two portions (10, 11) forming an angle between themselves, a first of these portions (10) being sized for insertion between the articular faces (101) of two adjacent vertebrae (100) and the second portion (11) being sized and oriented with respect to the first portion (10) in order to be able to rest against the body of the vertebra (100) when said first portion (10) is inserted between said articular faces (101), each portion (10, 11) being drilled with a reception hole (12, 13), along a direction perpendicular to said second portion (13), for an anchoring screw (3) of the platelet (2) to the vertebra (100) ; - at least one connection rod (4) capable of connecting two vertebrae (100), and - connection means (4, 5, 7), capable of assembling a connection rod (4) to two platelets (2) attached to the vertebrae (100) to be treated.

Description

PIECE OF EQUIPMENT ENABLING OSTEOSYNTHESIS OF CERVICAL VERTEBRAE The present invention concerns a piece of equipment enabling osteosynthesis of cervical vertebrae. It is well know to perform the osteosynthesis of two cervical vertebrae by placing, following an anterior route, an intervertebral implant and/or a plate attached to the bodies of the vertebrae. This anterior surgical approach makes the operation relatively complex and delicate to perform. The posterior surgical approach is less complicated and delicate to implement, and the purpose of the present invention is essentially to provide a piece of equipment which may be implanted by posterior approach for the osteosynthesis of two or several cervical vertebrae. According to the invention, the equipment comprises: - at least two vertebra-supported platelets, each exhibiting two portions forming an angle between themselves, a first of these portions being sized for insertion between the articular faces of two adjacent vertebrae and the second portion being sized and oriented with respect to the first portion in order to be able to rest against the body of the vertebra when said first portion is inserted between said articular faces, each portion being drilled with a reception hole, along a direction perpendicular to said second portion, for an anchoring screw of the platelet to the vertebra; - at least one connection rod capable of connecting two vertebrae, and - connection means, capable of assembling a connection rod to two platelets attached to the vertebrae to be treated. Thanks to their shape, the platelets may rest stably on the vertebrae to be treated and may, thanks to the holes that they comprise, be attached solidly to these vertebrae. The connection rod may then be assembled to these platelets thanks to said connection means, this rod and these platelets thereby ensuring perfect immobilisation of the vertebrae with respect to one another. The angle between both portions of a same platelet may be comprised between approx. 130° and approx. 145°. Preferably, the equipment comprises a set of platelets having different angulations between their first and second portions, the platelet having the angulation closest to the patient's anatomy being chosen within this set of platelets. For example, the equipment may comprise platelets having respective angulations of 130°, 135°, 140° and 145° between their first and second portions. Said second portion of a platelet may have such a length that after placing this platelet over a vertebra, this second portion extends along the upper articular face of the underlying vertebra, and the hole provided in said first portion of the other platelet may be sized and positioned in order to receive the anchoring screw engaged through the hole of said second portion of the first platelet mentioned. A same anchoring screw is thus used to attach said second portion of the first platelet and said first portion of the second platelet. A connected is therefore established between both vertebrae treated at this anchoring location of the platelets, contributing to the realisation of a perfect osteosynthesis. The hole of said first portion of the second platelet may be oblong, with its length oriented along the longitudinal direction of this first portion, for easier engagement of the anchoring screw therethrough. Generally, along the same line, the holes of the first portions of all the platelets of the equipment according to the invention are oblong with their lengths oriented along the longitudinal direction of these first portions. The means for connecting a rod to a platelet may consist of: - a threaded stud connected to the platelet; - a connection piece in the form of a yoke, i.e. including two parallel branches drilled with holes which enable the engagement thereof on the stud and a slightly deformable rounded portion, connecting one end of these branches; this rounded portion defines a bore for receiving the rod, and enables mobility of the branches between a normal spacing position and a closing-in position, whereas said bore may receive with a close-fit the rod when the branches are spaced apart and said rounded portion clamping the rod when the branches are brought closer to one another, this clamping enabling immobilisation of the rod with respect to the connection piece; and - where a nut may be screwed to the stud for clamping the connection piece between said nut and the platelet in order to bring said branches closer to one another and for clamping thereby said rounded portion around the rod. The stud may be fixed with respect to the platelet or be mobile with respect to this platelet, notably be articulated. This mobility facilitates the engagement of the yoke on the stud. To provide this mobility, the stud may comprise a spherical portion at its end connected to the platelet and the platelet may comprise a spherical cavity for receiving this spherical portion and a wall for retaining this spherical portion in this cavity. This wall may notably be deformable in order to be able to be closed around said spherical portion after engagement in the cavity. The stud, when it is mobile to swivel round its axis with respect to the platelet, as it is the case of an articulated stud by dint of a spherical portion and of a spherical cavity as mentioned above, and the connection piece, may comprise means enabling immobilisation of the stud in rotation around its axis when this connection piece is placed on this stud. The stud is thus held in rotation when clamping the nut, without resorting to a retention instrument. These means may notably be in the form of longitudinal flat surfaces arranged on the stud and of oblong holes laid out in the branches of the connection piece. The stud may besides comprise a proximal portion protruding axially, for the assembly of an extension rod for easier descent of the connection piece on the stud. The stud may also comprise a tapered portion enabling to sever beyond the nut after placing this nut on this stud, in order to reduce the height of the stud. At least one platelet may exhibit, by at least one screw reception hole it comprises, a slot which goes therethrough and which extends along this hole on a portion of the perimeter of this hole, this hole and this slot delineating thus between themselves a band of material exhibiting resilient flexibility along a substantially radial direction with respect to the hole; the screw intended to be placed in this hole then comprises a faceted portion, notably hexagonal in shape, whereas said band may clear away, as the screw is swivelling, to let through before itself an angle delineated by two facets and coming back, thanks to its resilient flexibility, in a contact position with a facet when this facet lies along it. This band thus constitutes a means enabling to limit the swivelling of the screw and therefore to oppose any risk of loosening thereof under the effect of repeated loads transmitted to the platelet by the vertebrae. The invention will be better understood, and other characteristics and advantages thereof will appear, with reference to the appended schematic drawing, representing, as a non-limiting example, a preferred embodiment of the equipment of interest. Figure 1 is an exploded perspective view of the different types of elements forming said equipment; Figure 2 is a view of these types of elements under another angle; Figure 3 is a side view of a sub-assembly formed by this equipment, placed on cervical vertebrae, and Figure 4 is a view similar to Figure 3, after placing a second sub- assembly on the vertebrae. Figures 1 and 2 represent an equipment 1 enabling osteosynthesis of cervical vertebrae, including at least two vertebra-supported platelets 2, at least four screws 3 for anchoring the platelets 2 to the vertebrae, at least one connection rod 4 capable of connecting two vertebrae, at least two threaded studs 5 intended to be connected to the platelets 2, at least two connection pieces 6 and at least two nuts 7. Each platelet 2 exhibits two portions 10, 11 forming an angle between themselves. The equipment 1 may comprise a set of platelets 2 having different angulations between their first and second portions 10, 11 , notably pairs of platelets 2 having respective angulations of 130°, 135°, 140° and 145° between these first and second portions. As it appears with reference to Figures 3 and 4, the portion 10 of each platelet 2 is sized to be inserted between the articular faces 101 of two adjacent vertebrae 100 and the portion 11 is sized and oriented with respect to the portion 10 in order to be able to rest against the body of the vertebra 100 when the portion 10 is inserted between said articular faces 101. Each portion 10, 11 is drilled with a reception hole 12, 13, along a direction perpendicular to the portion 11, of a screw 3. The hole 12 of each portion 10 is oblong, with its length oriented along the longitudinal direction of this portion, and, on the portion 11 side, is delineated by a bore 14 whereof the axis is perpendicular to the plane of the portion 11 to receive a screw 3 along a direction substantially perpendicular to the plane of this portion 11. The hole 13 of each portion 11 is mostly rounded and exhibits a rectilinear edge parallel to a longitudinal edge of the portion 11. The latter comprises a slot running therethrough along this rectilinear edge and which extends along the hole 13 beyond this edge, on a portion of the perimeter of this hole 13. This hole 13 and this slot delineate thus between themselves a band 15 of material exhibiting resilient flexibility along a direction substantially radial with respect to the hole 13 (the platelet 2 is made of implantable metal material, notably titanium). Between the hole 13 and the portion 10, the portion 11 comprises a peripheral wall 16 delineating internally a spherical cavity 17 and having a deformable structure, this cavity 17 being designed to receive a spherical portion interconnected with the stud 5 and the wall 16 being designed to retain this spherical portion with a possibility of articulation, by crimping around this spherical portion, as described below. Each screw 3 comprises a thread adapted for insertion in the body of the vertebrae 100, and exhibits, below its head, a faceted portion 20, hexagonal in shape. The hole 13 and this portion 20 are sized so that near completion of the screwing process, each angle delineated by two consecutive facets of the portion 20 bears against said band 15, which clears away to let through said angle ; the band 15, upon completion of said passage, resumes, thanks to its resilient flexibility, a position of contact with a facet of the portion 20 when this facet lies along it; upon completion of the screwing process, a facet lies along the band 15, and in superficial contact therewith. This contact enables to limit the swivelling of the screw 3 and therefore to counteract any risk of loosening for this screw 3 under the effect of the repeated loads transmitted to the platelet 2 by the vertebrae 100. The rod 4 is cylindrical and has, in the example represented, rounded ends. It is made of rigid material, notably implantable titanium, and may exhibit a slight possibility of deformation to be adapted, if necessary, to the desired position wherein the vertebrae 100 are immobilised. The stud 5 is threaded in order to be able to receive the nut 7 screwed thereon. At its end intended for connection with the platelet 2, the stud 5 comprises a sphere 21 capable of being engaged in the cavity 17 and of being articulated therein in order to enable multi-directional backlash of the stud 5 with respect to the platelet 2. As indicated above, the wall 16 is closed by crimping around the sphere 21 after engagement in the cavity 17, to enable the retention of this sphere in this cavity. The stud 5 also comprises two longitudinal flat surfaces 22 laid out thereon, to enable its immobilisation in rotation around its axis with respect to the platelet 2, a threaded proximal portion 23, protruding axially, for screwing an extension (not represented) facilitating the descent of the connection piece 6 on the stud 5, and a tapered portion 24 enabling to sever this stud 5 beyond the nut 7 after placement of said nut thereon. The connection piece 6 is in the form of a yoke, i.e. comprises two parallel branches 25 drilled with oblong holes 26 which enable shrink-fitting thereof on the stud 5 and a rounded portion 27 slightly deformable, connecting one end of these branches 25. This rounded portion 27 defines a bore for receiving the rod 4, and enables mobility of the branches 25 between a normal spacing position and a closing position; said bore may, in spacing position of the branches 25, receive the rod 4 with a close fit, but with the possibility of sliding, and, in closing-in position of the branches 25, the rounded portion 27 clamps the rod 4 which enables immobilisation of the rod 4 with respect to the connection piece 6. The distal branch 25 comprises a cavity of spherical shape for resting on the wall 16, which wall has a spherical external shape, these spherical shapes enabling the connection piece 6 to rest superficially against the wall 16 regardless of the orientation of the stud 5 with respect to the platelet 2. The proximal branch 25 exhibits a spherical bowl 28 coaxial to the hole 26, for the reception of a corresponding spherical portion of the nut 7. The latter exhibits perpendicular transversal slots delineating notches forming a resting point for a tool intended for the clamping thereof. In practice, as shown on Figure 3, the portion 11 of a platelet 2 is engaged between the articular faces 101 of two consecutive vertebrae 100 and the portion 10 is pressed against the body of the underlying vertebra 100, then the screw 3 are placed. It appears on Figure 4 that, when two platelets 2 are placed on two consecutive vertebrae 100, the hole 12 of the underlying platelet 2 faces the hole 13 of the overlying platelet 2, which enables placing a single screw 3 through both these holes 12, 13. A link is thereby established between both vertebrae 100 at this anchoring point of the platelets 2, contributing to the realisation of a perfect osteosynthesis. The extension rods are then placed on the proximal portions 23 of the studs 5 and the connection pieces 6, with the rod 4 engaged through their rounded sections 27, are brought down on these extension rods, then on the studs 5. The nuts 7 are then screwed, then the studs 5 are severed by the tapered portions 24 to reduce their height. As appears from the foregoing, the invention provides an equipment enabling osteosynthesis of cervical vertebrae exhibiting, with respect to analogue equipment of the previous art, the decisive advantage of being implantable by posterior approach to perform the osteosynthesis of two or several cervical vertebrae. It goes without saying that the invention is not limited to a given embodiment described above for exemplification purposes, but extends to all embodiments covered by the appended claims.

Claims

CLAIMS 1 - Equipment (1) enabling osteosynthesis of cervical vertebrae (100) characterized in that it comprises : - at least two vertebra-supported platelets (2) , each exhibiting two portions (10, 11) forming an angle between themselves, a first of these portions (10) being sized for insertion between the articular faces (101) of two adjacent vertebrae (100) and the second portion (11) being sized and oriented with respect to the first portion (10) in order to be able to rest against the body of the vertebra (100) when said first portion (10) is inserted between said articular faces (101), each portion (10, 11) being drilled with a reception hole (12, 13), along a direction perpendicular to said second portion (13), for an anchoring screw (3) of the platelet (2) to the vertebra (100) ; - at least one connection rod (4) capable of connecting two vertebrae (100), and - connection means (4, 5, 7), capable of assembling a connection rod (4) to two platelets (2) attached to the vertebrae (100) to be treated.

2 - Equipment (1) according to claim 1 , characterized in that it comprises a set of platelets (2) having different angulations between their first and second portions (10, 11).

3 - Equipment (1) according to claim 1 or claim 2, characterized in that said second portion (11) of a platelet (2) has such a length that after placing this platelet (2) over a vertebra (100), this second portion (11) extends along the upper articular face (101) of the underlying vertebra (100), and the hole (12) provided in said first portion (10) of the other platelet (2) is sized and positioned in order to receive the anchoring screw (3) engaged through the hole(13) of said second portion (11) of the first platelet (2) mentioned.

4 - Equipment (1) according to claim 3, characterized in that the hole (12) of said first portion (10) of the second platelet (2) is oblong, with its length oriented along the longitudinal direction of this first portion (10).

5 - Equipment (1) according to any of claims 1 to 4, characterized in that the holes (12) of the first portions (10) of all the platelets (2) are oblong with their lengths oriented along the longitudinal direction of these first portions (10).

6 - Equipment (1) according to any of claims 1 to 5, characterized in that the means for connecting a rod to a platelet (2) consists of : - a threaded stud (5) connected to the platelet (2) ; - a connection piece (6) in the form of a yoke, i.e. including two parallel branches (25) drilled with holes (26) which enable the engagement thereof on the stud (5) and a slightly deformable rounded portion (27), connecting one end of these branches (25) ; this rounded portion (27) defines a bore for receiving the rod (4) , and enables mobility of the branches (25) between a normal spacing position and a closing-in position, whereas said bore may receive with a close-fit the rod (4) when the branches (25) are spaced apart and said rounded portion (27) clamping the rod (4) when the branches (25) are brought closer to one another, this clamping enabling immobilisation of the rod (4) with respect to the connection piece (6) ; and -a nut (7) which may be screwed to the stud (5) for clamping the connection piece (6) between said nut and the platelet (2) in order to bring said branches (25) closer to one another and for clamping thereby said rounded portion (27) around the rod (4).

7 - Equipment (1) according to claim 6, characterized in that the stud (5) is mobile with respect to the platelet (2), notably articulated.

8 - Equipment (1) according to claim 7, characterized in that the stud (5) comprises a spherical portion (21) at its end connected to the platelet (2) and the platelet (2) comprises a spherical cavity (17) for receiving this spherical portion (21) and a wall (16) for retaining this spherical portion (21) in this cavity (17).

9 - Equipment (1) according to claim 7 or claim 8, characterized in that the stud (5) and the connection piece (6), comprises means (22, 26) enabling immobilisation of the stud (5) in rotation around its axis when this connection piece (6) is placed on this stud (5).

10 - Equipment (1) according to any of claims 6 to 9, characterized in that the stud (5) comprises a proximal portion (23) protruding axially, for the assembly of an extension rod.

11 - Equipment (1) according to any of claims 6 to 10, characterized in that the stud (5) comprises a tapered portion 24 enabling to sever this stud (5) beyond the nut (7) after placement of this nut on this stud (5).

12 - Equipment (1) according to any of claims 1 to 11 , characterized in that at least one platelet (2) exhibits, by at least one screw (3) reception hole

(13) it comprises, a slot which goes therethrough and which extends along this hole (13) on a portion of the perimeter of this hole, this hole (13) and this slot delineating thus between themselves a band (15) of material exhibiting resilient flexibility along a substantially radial direction with respect to the hole (13) ; the screw (3) intended to be placed in this hole (13) then comprises a faceted portion (20), notably hexagonal in shape, whereas said band (15) may clear away, as the screw (3) is swivelling, to let through before itself an angle delineated by two facets and coming back, thanks to its resilient flexibility, in a contact position with a facet when this facet lies along it.