EP0993280A1

EP0993280A1 - Adjustable fixing device for straightening and supporting the back bone

Info

Publication number: EP0993280A1
Application number: EP98933734A
Authority: EP
Inventors: David Attali; Jean Luc Chauvin; David Attia
Original assignee: Individual
Current assignee: Individual
Priority date: 1997-06-27
Filing date: 1998-06-26
Publication date: 2000-04-19
Also published as: FR2765093B1; AU8345198A; FR2765093A1; WO1999000065A1; KR20010020503A

Abstract

The invention concerns an adjustable fixing device for straightening and supporting the bone system, in particular the back bone, comprising at least an anchoring element (1) with at least one part (5) capable of being fixed relative to the bone, a head (3) with an axis (XX'), an intermediate ring (9), and a blocking element (6) capable of being fixed on the head (3) end (7). The invention is characterised in that the surface (61) pressing the blocking element (6) against a clamping member (8) for locking in an orifice (10) lateral relative to the axis (XX') a rod connecting (4) several fixing devices, is hollow and spherical and the zone pressing (91) the intermediate ring against this clamping member (8) is an internal circular ridge; and said clamping member (8) consists of at least two separable parts (81, 82) each comprising a half-collar (121, 122) forming together said clamping orifice (10) and a part forming a bore (11) flange (131, 132) adapted to be threaded on said head (3) and whereof the external pressing surface (141, 142) has a spherical shape matching with the intermediate ring corresponding (9) pressing shapes and of the blocking element (6).

Description

ADJUSTABLE FIXING DEVICE FOR STRAIGHTENING AND SHRINKING OF THE RACHIS

The present invention relates to orientable fixing devices for the straightening and shoring of a bone system.

The technical sector of the invention is the field of the manufacture of osteosynthesis implants.

The main application of the invention is the straightening and propping up of a spine called a spine, of man or even possibly of animal. These two operations are necessary inter alia in the event of a fracture of the vertebrae or in the event of deviation of the spinal column resulting for example from scoliosis, kyphosis or disc disease. Various devices are known for ensuring said straightening and shoring operations and some of which have been the subject of patent applications such as, for example, patent application WO 9101691 (MARNAY Thierry), FR 2624720 ( COTREL Yves) or that FR 271 1909 (by the same applicants as the present invention): these various devices described all consist of fixing implants screwed along the curvature of the spine and connecting these by one or two rods parallel to the backbone to serve as a forestay; the rods are introduced longitudinally into grooves made in the screw heads forming the bodies of the implants and are locked in the bottom of the grooves by means of screws and / or nuts screwed onto these heads.

There are also systems which do not use screw implants but hooks or straps around the lamar, spinous, transverse or articular regions of each vertebra. In all these systems or devices, the connecting rod between the various anchoring elements has a fixed orientation relative to them, namely orthogonal and cannot be modified, which requires on the one hand to have a very high precision in the alignment of the various anchoring elements, which is not often possible and is often very random, and on the other hand as a result of bending the connecting rods to make up for any shifts between these elements anchoring: to minimize deformation of said rod, different devices were then developed to allow orientation thereof relative to each anchoring element.

Some of these devices have been the subject of patent applications such as application WO 96/27340 (STE STRYKER FRANCE) which teaches an element for receiving / blocking the rod forming a clamp, in one piece and of which the locking axis is offset from that of the anchoring element, said clamp comprising, in the cavity inside which passes said rod, a compressible ring allowing a certain movement of the parts relative to the other. There is also application FR 2693365 (VIGNAUD Jean-Louis) also describing a clamp device for lateral attachment of the rod and comprising an oblong hole to be threaded on the head of the anchoring screw and allow a clearance, depending on the orientation of the oblong hole, of the receiving / blocking part with respect to the anchoring screw. These two devices both comprise a clamping element of the rod which therefore makes it possible to immobilize the latter laterally with respect to the anchoring element, as, moreover, this is retained in the present invention.

There are also anchoring systems allowing the rod to be oriented relative to the anchoring element but in the axis of the latter as described in patents EP 242708 and WO 89/00028.

All of these known devices, some of which have therefore been protected, however offer the possibility of rotation of the connecting rod with respect to the anchoring screws which is fairly reduced both in amplitude of angle and in degrees of freedom; moreover most of these devices offer only a contact and tightening surface between the rod and the various parts of the anchoring element which is quite small, which does not make it possible to resist, especially over time, significant forces. . Some of them are also quite complex to implement such as the first cited which requires prior threading of the clamps along the connecting rod before engaging them simultaneously on the anchoring elements which is not not a very simple handling and installation, and can be very delicate;

Thus the problem posed is to produce an orientable fixing device, for the straightening and shoring up of the bone system, ie essentially the spine such that one can orient in as many directions as possible and with an angle of at least 10 ° in each direction, the connecting rod with respect to each anchoring system fixed to the bone, and this with a clamping element of the connecting rod which is offset thus allowing the choice of the placement of the rod on one side or the other of the axis of the anchoring system and reduce the overall height and thus bring the connecting rod closer to the bone to be straightened and propped up, while ensuring effective and lasting immobilization of all the mobile elements relative to each other after tightening and allowing not only a quick and simple assembly but also an easy adjustment of each part of the assembly. One solution to the problem posed is an orientable fixing device comprising at least one anchoring element having at least one part capable of being fixed relative to the bone, a head forming a boss and a crown intermediate between said anchoring element. and said boss; a clamping means, adapted to immobilize in a hole disposed laterally with respect to said head a connecting rod between several fixing devices, has a compatible bore to be threaded on said head until it comes to bear against the intermediate crown; blocking means, adapted to bear against said clamping means, is fixed to the end of the head; according to the invention: - the bearing surface of the locking means against said clamping means is of spherical hollow shape and the bearing zone of said intermediate crown against this clamping means is an inner circular edge of this crown. The purpose of this edge, which is preferably sharp, is to punch the external surface of the corresponding clamping means: this incrustation which will be called "impaction" makes it possible to obtain an effective immobilization between the clamping means and the element of anchoring after blocking. To obtain a better impaction of the intermediate crown in the spherical part of the clamping means, it can be manufactured with a metal having a lower hardness and / or elastic limit than that of the material of the intermediate crown (for this type of medical application, we mainly use titanium or stainless steel);

- And said tightening means is composed of at least two separable parts each comprising a half collar each forming a kind of stirrup and together said tightening hole of the connecting rod, and a part forming a kind of washer according to said bore and whose outer bearing surface is spherical in shape compatible with corresponding support forms of the intermediate crown and of the locking means and capable of allowing the orientation and the angulation of said tightening orifice of the connecting rod, of at least 5 ° and even 10 ° in all directions with respect to to any axis orthogonal to that of said boss.

In a preferred embodiment, the two said separable parts are identical; they comprise on at least part of their facing surfaces bearing against one another, at least respectively a hollow female part and a protruding male part compatible and cooperating with each other for interlocking in order to position and to immobilize the two parts relative to each other.

In a particular embodiment, the end of the head of the anchoring element has an imprint capable of cooperating with any screwing tool, which makes it possible to maintain said anchoring element during the positioning of the locking means. (this can be a self-locking nut and screwed onto said head) thus avoiding exerting forces on the assembly which would be traumatic for the patient and detrimental to the solidity of the anchoring relative to the bone. Other embodiments are described below and illustrated in the enclosed figures; the result is new devices for straightening and shoring, in particular of a spine, answering the problem posed above and bringing advantages compared to the devices known to date. Indeed, the ball joint design integrated in the head of the anchoring element makes it possible to have:

on the one hand on the side of the clamping means, on a large contact and therefore clamping surface and on the side of the intermediate ring of a large support and blocking perimeter, ensuring good rigidity between the different rooms ;

- On the other hand an angulation of the rod relative to the anchoring system in all directions which can go for example up to at least plus or minus 10 ° relative to a plane perpendicular to the axis of attachment of the anchoring element, and 360 ° in this plane as well as relative to the axis of the rod on itself.

The lateral "stirrup" arrangement of the clamping means ensuring the maintenance of the connecting rod makes it possible to bring the latter as close as possible bones that we want to align: this is due not only to the very design of such a stirrup system, but also to the possibility of rotation by lowering said stirrup as far down as possible. Said clamping element or lateral bracket being produced in two parts which are put in place one before the rod and the other after the latter, allows an implementation of all the elements with respect to one another simple chronological manner and an adjustment not requiring in most cases the bending of the connecting rod; this reduces the intervention time and avoids weakening all the mechanical parts. One could cite other advantages of the present invention but those mentioned above already show enough to prove its novelty and interest.

The description and the figures below represent an exemplary embodiment of the invention but are in no way limiting: other embodiments are possible within the scope of the scope of this invention, in particular by changing the 'anchoring element which is represented here by a screw but which could be constituted by one or more hooks provided with a bent base in the form of a blade or in the form of a fork for fixing externally on the vertebrae. Figure 1 is a perspective view showing three orientable fastening devices according to the invention and connected by a common connecting rod for the straightening and shoring of a spine.

Figure 2 is a perspective view of a fixing device according to the invention mounted with a connecting rod. Figure 3 is a sectional view along the plane (Y Y ', ZZ') of Figure 2.

Figure 4 is a perspective view of the different separable parts of Figure 2 before assembly.

There is shown in Figure 1 three straightening and shoring devices of a spine 2 as described in Figures 2 to 4 and connected by a smooth rod, or not, connecting 4. The spine 2 is generally supported by two identical sets and systems placed parallel and on each side of the backbone 2a. Each assembly therefore includes fixing devices shown here with anchoring screws 5 on the lateral processes 2b of each vertebra 2c. Such an assembly thus relieves the 2d intervertebral discs and can be used to correct the spinal deformities 2 such as kyphosis, scoliosis or disc disease.

Each orientable fixing device comprises in a known manner at least: - an anchoring element 1 having at least one part 5 capable of being fixed relative to the bone, a head 3 forming a boss of axis ZZ 'and between the two an intermediate crown 9,

- A clamping means 8 able to immobilize in a hole 10, disposed laterally with respect to the axis ZZ 'a connecting rod 4 of axis XX' between several fixing devices and comprising a bore 11 compatible to be threaded on said head 3 until it comes to bear against the intermediate crown 9,

- And a locking means 6 adapted to come into abutment against said clamping means 8 and to be fixed on the end 7 of the head 3. According to the invention the surface 6 _j of support of the locking means 6 against said clamping means 8 is of hollow spherical shape and the bearing zone 9 ₁ of said intermediate ring 9 against this clamping means 8 is an inner circular edge of this ring which can be the inside edge of the end of a section cylindrical (with a height of the order of 0.1 to 0.4 mm for example for device dimensions as indicated in the description below) and which surrounds the cavity 9 ₂ in which the part can rotate spherical clamping means 8 which is housed there as described below.

Said locking means 6 and said intermediate ring 9 therefore take up the clamping means 8 which is, for its part concerned as described below, of spherical shape symmetrical with respect to the axis ZZ 'of the head 3: thus during the final tightening of the locking means 6 there is an impact of the entire perimeter of the edge 9 _X of the intermediate crown 9 on the spherical part of the tightening means 8 thus ensuring complete immobilization between these two parts in the chosen position.

Said clamping means 8 is itself composed of at least two separable parts 8 _1} 8 ₂ each comprising a half-collar 12 _{l 5} 12 ₂ together forming said orifice 10 for tightening the connecting rod 4 and a part each forming a washer 13 _ls 13 ₂ following and constituting said bore 11; the external support surfaces 14 ^ 14 ₂ of these "washers", against the corresponding support forms respectively 9 _1; of the intermediate crown and 61 of the blocking means are therefore spherical in shape compatible with these support forms with which they are therefore in contact and cooperate with them by being able to rotate 1 in the manner of a ball joint during adjustment of implementation. To allow such rotation, in addition to the complementary spherical shapes of said parts, the outer perimeters of said surfaces 9, and zone (y _χ of support of the locking means 6 and of said intermediate ring 9 are spaced from each other in leaving a peripheral opening "a" around the axis ZZ 'of the head 3 and through which can therefore be rotated 360 ° relative to this axis ZZ', the two said separable parts 81, 8 ₂ forming the means tightening the connecting rod 4: the part 19 connecting the half-collars 12 _{1 (} 12 ₂ with the washers 13 t, 13 _? form a neck of thickness b less than the height of the space "a", allowing thus an angle orientation α of said collar 12 of at least 10 ° for example up and down relative to the plane (XX ', YY'), and in the plane (YY \ ZZ '): this angle may be more important if the outer perimeter of the surface 9 _1} and of the zone 6j of ap pui then increasing the distance a, to the detriment however of the surfaces and support zones, which can however be compensated by increasing the diameter of the spheres.

It is also possible to tilt all of the half-collars 12 at an angle β of at least 10 ° in a direction perpendicular to that defined for the angle α along the plane of Figure 3 and as shown in the Figure 2 or in fact in the plane XX ', ZZ': thus the combination of the inclinations along the angles α and β and the rotation of 360 ° around the axis ZZ 'even gives any latitude in orientation of the axis XX 'of the connecting rod 4 relative to the axis ZZ' of the anchoring element.

To allow said orientation, the diameters of the internal bores 11 of the parts forming washers 13 _ls 13 ₂ of the separable parts 8 _1; 8 ₂ are greater than the external diameter of the part of the anchoring head 3 which they surround, leaving a clearance 15 between them, symmetrical in revolution when the axis XX 'is orthogonal to the axis ZZ', and asymmetrical well heard until even canceled by contact of the parts with respect to each other when the angle α and / or β reaches its maximum.

So that the two said separable parts 8,, 8 ₂ , which can be made themselves in several parts but integral by construction and stirrup, cooperate well with each other and ensure good tightening and immobilization on the connecting rod 4:

on the one hand, the bottom of the half-collars 12 _j may include ridges, threads or other roughness to increase the adhesion of the rod 4 against the walls of the orifice 10 which they constitute, and

- on the other hand their facing surface and coming to bear against one another, comprise at least respectively a hollow female part and a protruding male part 14 compatible and cooperating with each other by interlocking preferably at the level of their half-collar portion 12 _{l 5} 12 ₂ .

Preferably the two said separable parts 8,, 8 ₂ are identical so that they can be used either as a lower part or as an upper part and can be mixed without the operator needing to choose an upper or lower part; this is perfectly achieved thanks to the spherical and symmetrical shapes with respect to the axis ZZ 'and to the plane XX', YY 'of said parts forming washers 13 ^ 13 ₂ and also with regard to the parts forming half-collars 12,, 12 ₂ with nestable surfaces 14 having a symmetrical profile with respect to the axis YY 'of said parts, such as a separation surface in the form of a sinusoid as shown in FIG. 2.

The end 7 of the head 3 of the anchoring element preferably comprises an imprint 16 able to cooperate with any screwing tool such as for example of hollow hexagonal shape with even at the bottom of this imprint a channel, not shown on the figures which can open up to the other end of part 5 of the anchoring element capable of being fixed in the bone, when the latter is a screw as shown in the attached figures; such screws are called cannulated pedicles and allow the orientation of the screw to be controlled when it is screwed, by means of a pin around which said internal hollow part of the screw is slid. The screws may of course not be thus cannulated.

To ensure the screwing of the latter into the bone, said intermediate crown 9 can be of polygonal external shape such as for example hexagonal: this intermediate crown 9 being of a relatively large diameter such as for example 10 mm for a length L total of the anchoring element from 40 to 70 mm allows to have a large bearing surface with the screwing key, avoiding any risk of matting and allowing a good screwing torque which can even avoid tapping the bone beforehand. For such dimensions of the body of the screw 5, the height of the head 3 of this screw can be of the order of 15 mm between the intermediate ring 9 and its end 7, with a diameter of the part receiving the bore 11 of the clamping element of the order of 4.5 to 5 mm, the internal diameter of said bore 11 being from 6 to 6.5 mm.

As shown in the attached figures, the locking means 6 is a nut, preferably self-locking, screwed onto the threaded end 7 of the anchoring head 3 and which may be of a diameter greater than the part of the head 3 around which can rotate the washer portions 13 of the parts of the clamping means 8; the use of a self-locking nut avoids an additional locking system of the lock nut type and therefore promotes compactness of the assembly.

The lateral arrangement of the orifice 10 of the clamping means 8 relative to the axis ZZ 'of the anchoring element thus makes it possible:

- On the one hand to bring the connecting rod 4 of the backbone 2a of the spine even if the axis of the anchoring elements such as the fixing screws 5 are distant from said backbone which can simplify the setting in place, - on the other hand to pass said rod 4 as close as possible to the profile of the spine by orienting the collar portion 12 of tightening by a maximum angle α in an anticlockwise direction as shown in the figure 3 thus bringing the tightening orifice 10 closer to the bone itself.

Preferably the body of the screw 5 comprises a so-called lower part 5 on the side of its end, the tops of the threads 17 follow a cylinder of the same external diameter d and the thread bottoms 18 follow a conical surface converging towards the end of screw 5; the height h of this lower part 5 ₂ can be approximately two thirds of the total thread length of the screw 5; by way of example, the external diameter D can be of the order of 6 mm for a total length of screw 5 from 25 to 50 mm with a thread pitch of 3 mm, and a diameter of the thread bottom passing from 4 to 4.5 mm, up to 3 to 3.5 mm, in seven to eight thread pitches; said thread having a triangular profile whose front face 20 is inclined in the direction of screwing and the rear face is almost perpendicular to the axis ZZ 'of the screw 5 in order to oppose a maximum force to the tearing Such thread profiles avoid the risk of loosening and facilitate the initiation of screwing, avoiding pre-tapping; increasing the height of the thread towards the end of the screw 5 also improves the anchoring in the cancellous bone. The end 22 of said screw 5 can be of slightly conical shape with an angle of the order of 30 ° and have two self-tapping flats 23 as shown in FIG. 4 while having a non-aggressive rounded end.

Thanks to the various characteristics described above, an orientable fixing device according to the invention can be fixed in a simple and rapid manner according to the following operations:

- the body of the screws 5 is screwed into each vertebra 2c after having previously drilled them, by means of a key which is fitted onto the intermediate crown 9 of polygonal shape and this without therefore having to pre-tap a hole in the bone: the screw can also be guided on a spindle entering the internal channel provided for this purpose,

one of the separable parts 8 ₂ of the clamping means 8 forming half-stirrup is engaged on each screw head 3,

the rod 4 is positioned in the half-housings 10 provided for this in the half-collars 12 ₂ ,

- the second separable part 8 ₂ is put in place, forming the other half-stirrup, on the screw head 3 and coming to cover and enclose the rod 4, which second stirrup automatically aligns with the lower stirrup due to its symmetrical and complementary shape with it, - the nut 6 is screwed by means of a tubular key which allows the passage for example of a screwdriver coming to be housed in the cavity 16 located at the top of the screw head 3: it is thus possible to maintain the assembly of the screw 5 and to avoid its driving in rotation during the tightening of the nut 6, - the rod 4 is ideally oriented and positioned connecting several anchoring devices before the final tightening of the nuts 6, immobilizing the rod and therefore all of the vertebrae 2c in the desired position.

Claims

1. Orientable fixing device for straightening and shoring up a bone system comprising at least one anchoring element (1) having at least one part (5) capable of being fixed relative to a bone, a head ( 3) forming an axis boss (ZZ ¹ ), an intermediate ring (9) between said anchoring element (1) and said boss (3), and a clamping means (8) able to immobilize, in an orifice (10) disposed laterally with respect to the axis (ZZ '), a connecting rod (4) between several fixing devices, which clamping means (8) comprising a bore (1 1) compatible to be threaded on said head (3) until it comes to bear against the intermediate crown (9), and a locking means (6) capable of coming to bear against said clamping means (8) and to be fixed on the end (7) of the head (3), characterized in that:

- the support surface (6 _j ) of the locking means (6) against said clamping means (8) is of spherical hollow shape and the support zone

(9 j) of said intermediate ring (9) against this clamping means (8) is an inner circular edge of this ring;

- Said clamping means (8) is composed of at least two separable parts (8 _1; 8 ₂ ) each comprising a half collar (12 _1} 12 ₂ ) together forming said orifice (10) for clamping the connecting rod (4), and a part each forming a washer (13,, 13 ₂ ) along said bore (1 1) and the external support surface (14 ^ 14 ₂ ) of which is spherical in shape compatible with the support forms. corresponding to the intermediate crown (9) and the locking means (6), and capable of allowing the orientation and the angulation of said orifice 10, of at least 5 ° in all directions with respect to any axis orthogonal to ZZ '.

2. Fastening device according to claim 1, characterized in that the two said separable parts (8 ^ 8 ₂ ) are identical.

3. Fastening device according to any one of claims 1 or 2, characterized in that the facing surfaces and coming to bear against one another, said separable parts (8 d, 8 ₂ ) comprise at at least one hollow female part and a protruding male part (14) compatible and cooperating with each other by interlocking.

4. Device according to any one of claims 1 to 3, characterized in that the internal diameter of the bore (11) of the separable parts (8 _1} 8 ₂ ) is greater than the external diameter of the part of the head ( 3) of the anchoring element which they surround.

5. Device according to any one of claims 1 to

4, characterized in that the end (7) of the head (3) of the anchoring element comprises an imprint (16) capable of cooperating with any screwing tool.

6. Device according to any one of claims 1 to

5, characterized in that said intermediate ring (9) is of polygonal outer shape.

7. Device according to any one of claims 1 to

6, characterized in that the locking means (6) is a self-locking nut, screwed onto the threaded end (7) of the anchoring head (3).

8. Device according to any one of claims 1 to

7, characterized in that the anchoring part (5) capable of being fixed relative to the bone is a screw.

9. Fastening device according to claim 8, characterized in that the body of the screw (5) comprises a part, called the bottom (5 ₂ ) on the side of its end, the tops of the threads (17) follow a cylinder of same external diameter (d) and the thread bottoms (18) follow a conical surface converging towards the end of the screw (5).

10. Device according to any one of claims 8 or 9, characterized in that the screw (5) is hollow longitudinally along its axis (ZZ ') said hollow opening on one side at its end and the other in that (7) of the head (3).