WO1996031167A1

WO1996031167A1 - Device for straightening and supporting a backbone

Info

Publication number: WO1996031167A1
Application number: PCT/FR1995/000438
Authority: WO
Inventors: Jean-Luc Chauvin; David Attali
Original assignee: Chauvin Jean Luc; David Attali
Priority date: 1995-04-05
Filing date: 1995-04-05
Publication date: 1996-10-10
Also published as: AU2310595A

Abstract

A device for straightening and supporting an abnormally deviating backbone. Said device includes anchoring screws each having a head (3b) with two side arms defining a through-channel in the head for receiving a link rod that may be locked in place using a nut. The side arms (3c, 3d) of the head (3b) have internal (3h) and external (3g) screw threads so that a threaded link rod (4) may be locked in place using a threaded washer (5) surrounding said arms and engaging the threads on the rod (4), a nut (6) capable of being screwed onto the outside of the arms (3c, 3d) to clamp said washer against the rod (4), and a tapered plug (7) screwed in between said arms to hold them apart and prevent the nut (6) from being rotated and the rod (4) from being translated and rotated about its axis.

Description

DEVICE FOR STRAIGHTENING AND STRAIGHTENING A RACHIS

The present invention relates to a device for the straightening and shoring of a spine having an abnormal deviation. Straightening and ^shoring ^a vertebral column are two necessary operations, among other things, in case of fractures of the vertebrae or in the event of deviation of the spine resulting from, for example, ^a scoliosis or ^a kyphosis.

We know of such devices which have been for a number ^of years for various achievements. It is known from patent application WO91 / 01691 (MARNAY Thierry) devices which consist in fixing implants screwed on each side of the curvature of the spine and in connecting these by at least two rods parallel to the backbones to serve as was.

The rods are introduced longitudinally into grooves made in the head of the screws forming the body of the implants. The rods are locked in the bottom of the grooves by means of a nut with conical thread which allows to bring together by deformation each side of the groove towards the center of the body.

It is also known from patent application FR2 624 720 (COTREL Yves) other devices which consist in that the screwed implants comprise a body provided with a through channel delimited laterally by two vertical branches and externally threaded to receive a connecting rod. This device includes a threaded cap adapted to be screwed onto the lateral branches in order to position the rod on the screwed implants. A needle screw is screwed into a threaded bore formed in the cap so that its point comes to immobilize the rod.

Finally, it is known from the application EP 465 158 (MEHDIAN) a device similar to the preceding further comprising a thrust ^washer on the rod and has an additional locking screw housed ^within the main screw pressing the washer 'support.

Different rectifying devices and ^shoring spine described above do not allow a perfect locking in translation and in rotation of the connecting rod relative to the screw implants. In fact, in the first device, the tightening is obtained by bringing the lateral branches of the groove together, which does not prevent the sliding and rotation of the rod lo s from significant external forces. In other devices described above, the clamping is achieved ^by means ^of a set screw (and optionally ^a ^support ring) which may s ^rapidly damage under significant efforts due to the small supporting area on the rod.

It is these drawbacks ^that meant more particularly to remedy the present invention. The device according to the present invention comprises at least one screw comprising in its upper part two lateral branches internally and externally threaded delimiting an open channel for the establishment of a threaded connecting rod which is immobilized in translation and in rotation by the intermediate a washer surrounding the branches to come to cooperate with the thread of the rod, a nut adapted to be screwed on the outside of the branches in order to tighten the washer on said rod and an additional locking means such as 'a conical plug which is screwed between the arms to spread them apart and lock the nut.

In other words the ^invention provides a dipositif for recovery and shoring up the spine. which comprises several elements, each element comprising a body adapted to be anchored in a vertebra, each of said elements comprising a head adapted to be fixed (or immobilized with respect to) to a rod common to several of said elements, which head comprises a cylindrical upper part threaded and provided with a transverse groove (for through-passage of said rod extending along a longitudinal shaft axis which is perpendicular to ^the main longitudinal axis of each of said elements and / or said head) on both sides ^of which extend two lateral arms, which device comprises, for each said element, a thrust washer on said rod and a clamping means of said support washer against said rod, which ring is adapted to (be engaged and for) sliding around said lateral branches, which device further comprises, for each of said elements, a additional locking means such as an additional locking screw of said rod, (said additional locking screw and said washer and said clamping means extending coaxially along said main longitudinal axis of said element and / or said head) , in which :

- Said rod is a threaded rod. - said tightening means is a nut,

said washer has two threaded notches which are provided with threading parts (female) complementary (identical) to the threading (male) of said threaded rod, - said legs are provided ^with an external thread (male cylindrical) complementary to the thread (female) of said nut to cooperate therewith,

- Said branches are provided with a conical internal thread (female) complementary to the conical thread (male) of said locking means to cooperate therewith.

Filettées the notches of the washer allow for locking in rotation and in translation of the rod filettée relative to ^the anchoring member; it should be noted that the locking in translation of the rod is ensured by the washer but that the locking in rotation is ensured in addition and above all by the pressure of the bolt on the washer, the section of which presses the threaded rod; the locking can be further improved by pressing the base of the additional locking screw on the threads of the threaded rod: the conical thread of the locking screw and the branches of the head, allow locking in the locking position, nut and washer.

Said element can be constituted by screws and / or hooks provided ^with a bent base blade-shaped or fork-shaped with at least two teeth.

According to preferred embodiments of the invention:

- The filettées notches extend in two coaxial cylindrical Calotes extending along a common axis which is perpendicular to ^the axis of revolution of said washer having a radius identical to the radius of said rod;

the threads of the thread of said rod and of the corresponding threaded parts or notches of said washer have a curved profile, which is for example substantially semicircular:

- the rod includes a standard thread with a round thread (SNCF type): - said additional locking screw is a hollow headless screw crossed by a bore, for example hexagonal, triangular or square; the head of this locking screw may include a straight imprint for a normal screwdriver to allow disassembly in the event of a problem:

- The device comprises two of said threaded connecting rods substantially parallel to each other and to the spine and connected together by connecting bars, each threaded rod being adapted to be fixed to the vertebrae by several anchoring elements, to ensure distribution forces. The accompanying drawings, to give as ^examples, will allow a better understanding of the invention, its characteristics and the benefits it can provide:

Figure 1 is a perspective view showing the device for straightening and shoring of the spine according to the present invention.

FIG. 2 is an exploded perspective view illustrating the various elements making up the straightening and shoring device according to the invention.

Figures 3 and 4 are sections showing the various elements of shoring device and recovery assembled for ^{immobilization} of the connecting rod relative to the implants.

Figures 5 to 7 illustrate the application of ^the invention to an anchoring element consisting of a hook: Figure 5 illustrates a front view and partial section of a hook according to the invention; Figures 6 and 7 are views of the hook of Figure 5, respectively according to VI and according to VII. FIG. 1 shows a device 1 for straightening and shoring up a spine 2. The latter is generally associated with two identical devices placed in parallel and on each side of its backbones 2a. Each device 1 comprises ^anchoring systems on the lateral apophyses 2b 2c of each vertebra and a connecting rod 4 in order to relieve the intervertebral discs 2d. In other cases, the device 1 can be used to correct deformations of the spine 2, such as kyphosis or scoliosis.

As shown in FIG. 2, the device 1 firstly comprises anchoring elements constituted by screws 3 with self-tapping thread 3a surmounted by a body forming the head 3b of each screw. The head 3b comprises two branches 3c and 3d portion of a circular crown which delimit between them a channel or open transverse groove 3c on either side of the head 3b and perpendicularly to ^the main axis 1 1 of the screw 3.

As illustrated also in Figure 5. The cylindrical bottom ^(of longitudinal axis 21 perpendicular to ^axis 1 1) of the channel 3c has a profile in circle section 3f provided for receiving a threaded rod 4 cvlindriquc ^a longitudinal axis 20 perpendicular to ^axis 11 of the main member 3. Each side arm 3c and 3d includes external threads

3ε and interior 3h which cooperate respectively with the retaining means for blocking the connecting tiεc 4 on the \ is 3. The device 1 straightening and ^shoring comprises, for each screw 3 a washer 5 with ^the inner bore 5a is ^of a slightly larger diameter than the side branches 3c and 3d. The washer 5 is provided with two threaded notches 5b and 5c which are aligned along the same diametrical axis 19 so as to be parallel to the axis 20 of the connecting rod 4. The notches 5b and 5c have a profile in a portion of a circle whose radius is identical to that of the rod 4. The notches 5b and 5c respectively have an identical thread whose pitch is similar to that of the connecting rod 4.

In the representation of FIG. 2. the axes 19, 20 and 21 are mutually parallel and contained in a plane 22 constituting a plane of symmetry of the head 3b of the anchoring element, which plane contains said axis 11.

The means for retaining the rod 4 on the screw 3 consist on the one hand of a nut 6 adapted to be screwed onto the external thread 3g of the lateral branches 3d and 3c of the head 3b and on the other hand of a plug ( or locking screw) 7 conical externally threaded and which cooperates with the internal thread 3h of said branches 3c and 3d. The plug 7 comprises an imprint 7a with a hexagon socket for its rotation drive by means of a hexagon socket key; alternatively perhaps a straight imprint.

To Figures 3 and 4, there is shown the device 1 in the mounted position and it is noted that Técrou 6 makes it possible ^to immobilize the washer 5 in a position ^of support on the connecting rod 4 ^via notches filettées of the washer, while the cap 7 by its conical shape is immobilized on ^the one hand the ^nut ^(> in rotation and on ^the other hand the rod 4 in translation and in rotation about its axis. When the holding means are completely greenhouses, the upper edge of the ^nut 6 in order to ^avoid any risk of collision with external elements is noted that the upper face of the conical cap 7 is flush. in addition, there may be provided a cap 8 which covers ^the whole compound of the ^nut 6 and washer 5 and the stopper 7 to protect the threads 3g and 3h of the side 3c and 3d branches of the external elements such as the flesh. the threaded notches 5b and 5c further enable ^the operator to r o achieve a perfect adjustment of the desired length of the threaded rod 4, between two points 3 (or mild) ^anchor. In addition, the screw 3 is pierced (or not) in the middle in the known manner of a through hole 3i which allows to guide said screw during its establishment in the processes 2b of each of the corresponding vertebrae 2c. By reference to Figures 5 to 7. ^the ^invention applies to an element 3 configured as hook 14 whose base 16 bent ^extends peφendiculairement the longitudinal axis 11 of the implant of coφs 3: the bent base of the hook 14 may be fork-shaped and provided at its free end with two teeth 17. The angle 10 of the frustoconical surface 12 along which the thread of the screw extends

7 and the internal thread of the branches of the head, can be of the order of 3 degrees for example; the locking screw 7 is traversed by a bore 18.

The rod 4 is equipped at the end with a hexagon enabling a derotation prescribed in certain indications to be carried out. The shape of the inner cone and the pressure surface and the volume of the two lateral branches ensure complete locking of the nut.

It should ^moreover be understood that the above description has been given only as an example and does not limit the scope of the invention which would not depart by replacing the described execution details by all other equivalents.

Claims

1. Device for straightening and shoring a vertebral column comprising anchoring screw provided with a head comprising two lateral branches delimiting an open channel on both sides ^of said head for the passage of a rod connection which is immobilized by a nut, characterized in that the lateral branches (3c, 3d) of the head (3b) are internally threaded (3h) and externally (3g) to immobilize a threaded connecting rod (4) by the through a threaded washer (5) surrounding said branches and cooperating with the threads of the rod (4). a nut (6) adapted to be screwed onto the outside of the arms (3c) and (3d) in order to tighten said washer on the rod (4) and a conical plug (7) which is screwed between said arms to separate them and immobilize on the one hand the nut (6) in rotation and ^{on the} other hand the rod (4) in translation and in rotation about its axis.

2. Device according to claim 1. characterized in that the washer (5) comprises two opposite notches (5b, 5c) respectively comprising threads which cooperate with that of the rod (4) to allow perfect adjustment of the latter between two anchor points.

3. Device for straightening and shoring up a spine, which comprises several elements (3). each element having a body (3a) adapted to be anchored in a vertebra (2c), each of said elements comprising a head (3b) adapted to be fixed to a rod (4) common to several of said elements, which head comprises an upper part cylindrical threaded and provided with a groove (3c) extending transversely on either side of which there extend two lateral branches (3c, 3d), which device comprises for each of said elements, a washer (5) ^bearing on said rod and means (6) for clamping said washer pressing against said rod, which washer is adapted to slide around said lateral branches, which device further comprises, for each of said elements, means (7) for additional blocking of said rod, characterized in that:

• said rod is a threaded rod.

• said clamping means (6) is a nut, • said washer comprises two threaded notches (5b, 5c) which are provided with threading portions complementary to the threading of said threaded rod.

• said legs are provided ^with a complementary external thread to the thread of said nut. • said legs are provided ^with a complementary conical internal thread the conical thread of said locking means (7).

4. Device according to claim 3 wherein said locking means (7) is constituted by a locking screw.

5. Device according ^to any one of claims 3 or 4 wherein said elements are at least partly constituted by screws.

6. Device according ^to any one of claims 3 or 4 wherein said elements are at least partly constituted by hooks (14) having a bent base shaped blade or fork (16).

7. Device according ^to any one of claims 3 to 6 wherein the threads of the thread of said rod and threaded portions of said washer or corresponding notches have a curved profile.

8. Device according ^to any one of claims 4 to 7 wherein said additional locking screw is a hollow screw passing through a bore (18) and with an imprint.

9. Device for straightening and shoring a spine according to any one of claims 1 to 8 comprising two threaded connecting rods (4) disposed substantially parallel to each other and connected by connecting bars, each rod being suitable to be fixed to the vertebrae by several anchoring elements (3).