WO1995008298A1

WO1995008298A1 - Device for joining vertebrae, and bridge used for this purpose

Info

Publication number: WO1995008298A1
Application number: PCT/BE1994/000058
Authority: WO
Inventors: Louis François Charles BECKERS
Original assignee: Beckers Louis Francois Charles
Priority date: 1993-09-21
Filing date: 1994-09-20
Publication date: 1995-03-30
Also published as: BE1007550A3

Abstract

Device for joining vertebrae, comprising firstly a joining element (3); secondly at least one securing element (4) with an end part (8) having an opening (9) therethrough for a screw (10) or other fastening member; and thirdly attachment means (11) for attaching said at least one securing element (4) to the joining element (3), characterised in that the opening (9) in the end part (8) is slot-shaped, and in that the securing element (4) is provided with means (12) which lend lateral stability to the screw (10) or other fastening member which is fitted through the opening (9) in the end part (8).

Description

Device for joining vertebrae, and bridge used for this purpose

This invention concerns a device for joining vertebrae together, as well as a bridge used for this purpose. Such devices are also referred to as pedicle bridges.

In particular, the invention concerns a device of the type that consists of, firstly, a joining element, such as a frame, and secondly, at least one securing element with an end part, having an opening therethrough for a screw or suchlike, and thirdly, attachment means for attaching said at least one securing element to the joining element.

Devices of the above-mentioned type are known, in which two securing elements, having coplanar end parts, are connected by a bridging element.

These known devices have the disadvantage that the openings in the coplanar end parts at each bridging element only permit the screws to be mounted at predefined distances from each other. In the case where the screws are located at different distances, different bridging elements must be kept ready during the surgical operation. At present, pedicle bridges exist in four sizes, with respectively 67 mm, 63 mm, 59 mm and 55 mm between the openings.

However, it is not always easy to select the correct bridge once the positions where the screws are to be placed have been determined and the openings for the screws have been made in the vertebra or vertebrae. if the distance between the openings in the vertebra or vertebrae do not correspond precisely to the distance between the openings of one of the available pedicle bridges, it can happen that a screw is forced into an incorrect path. Furthermore, this disadvantageous effect is aggravated when pedicle bridges are being fitted on several vertebrae, since in this case even a slight left- right asymmetry in placing the openings in the vertebrae can result in the pedicle bridges no longer being precisely aligned with each other.

In order to get round the above-mentioned advantage to a certain extent, in WO 90/04948 it was proposed to make use of more or less long openings narrowing towards one end. The proposed solution however has the disadvantage that when the largest diameter of the openings is chosen too small, it does not help the above-mentioned problem much, and if said openings are chosen too large, the lateral stability between the screws and the pedicle bridge is insufficient, or in other words, sideways displacements can occur between the screws and the pedicle bridge, which is not at all impossible, since the force used to tighten the screws is relatively small.

The present invention therefore concerns a device for joining vertebrae, by means of which the above-mentioned disadvantages are avoided.

Although in a preferred embodiment, bridges will be used, having two securing elements connected by a bridging element, the present invention is not limited to such embodiment. As the invention is also advantageous in devices not having such bridging element it also relates to devices having separate securing elements or having securing elements connected to each other by other means than a bridging element.

For this purpose, the invention concerns a device for joining vertebrae, comprising firstly a joining element; secondly at least one securing element with an end part having an opening therethrough for a screw or other fastening member; and thirdly attachment means for attaching said at least one securing element to the joining element, characterised in that the opening in the end part is slot-shaped, and in that the securing element is provided with means which lend lateral stability to the screw or other fastening member which is fitted through the opening in the end part.

In the preferred embodiment, the above-mentioned means consist of a washer placed directly underneath the head of said screw, having an opening sufficiently small for the screw to fit into it, together with locking means for opposing any relative displacement between said washer and the underlying surface, or better still preventing it altogether.

In order to better explain the characteristics of the invention, various embodiments are described below by way of example, without being limitative in any way, with reference to the accompanying drawings, where:

fig. 1 is a schematic representation of the problem that can occur in spinal surgery; fig. 2 shows a device according to the invention; fig. 3 is a cross-section along line III-III in fig.

2; fig. 4 is a view in the direction of arrow F4 in fig.

3; fig. 5 shows only the part indicated by arrow F5 in fig. 3; fig. 6 is a view in the direction of arrow F6 in fig.

5; fig. 7 shows only the part indicated by arrow F7 in fig. 3; fig. 8 is a view in the direction of arrow F8 in fig.

7; fig. 9 shows only the part indicated by arrow F9 in fig. 3, more particularly the underneath of same; fig. 10 is a cross-section along line X-X in fig. 9; fig. 11 is a view in the direction of arrow Fll in fig. 10; fig. 12 is a cross-section, to a greatly enlarged scale, of the meshing between parts shown in figs. 8 and 9 respectively; fig. 13 shows a variant of the part shown in fig. 9; fig. 14 shows the use of the element in fig. 13; fig. 15 shows the fitting of a screw in a device according to the invention; fig. 16 shows another embodiment of the invention.

Fig. 1 is a schematic representation of a device l for joining vertebrae 2, consisting of firstly a joining element 3, and secondly three bridges each having two securing elements 4 which are screwed tight to the vertebrae 2. It is clear that attachment of the bridges can easily give rise to a problem of positioning.

For instance, it may happen that, as shown in fig. 1, the positions A to F where the screws are located may be unevenly distributed, as shown by way of example, or in other words the locations A to F are not all located on the two parallel lines 5 and 6. In such a case it is very difficult to make a joint with uniform bridges, and occasionally it will be necessary to use the technique described in WO 90/04948, in which for certain joints, instead of using bridges, wire is used.

In order nevertheless to enable a joint to be made with bridges, even when two, three, four or more bridges are attached to the joining element 3, according to a preferred embodiment of the invention use is made of a device 1, which as shown in figs. 2, 3 and 4 consists of firstly, a joining element 3; secondly two securing elements 4 connected by a bridging element 7 said elements 4 having end parts 8, preferably coplanar and each with an opening 9 for a screw 10 or suchlike; and thirdly attachment means 11 for attaching the securing elements 4 to the joining element 3, where the openings 9 in the end parts 8 are slot shaped, and where the securing elements 4 are provided with means 12 which lend lateral stability to the screws 10 fitted through the openings 9 in the coplanar parts 8.

The joining element 3 can, as in the known technology, consist of a frame formed by a ring-shaped, curved profile with a circular cross-section. The ring-shaped frame may be rectangular.

Each bridging element 7 consists of a bracket 13, such that when said bracket 13 is placed against the underneath of the above-mentioned frame, said frame sits precisely against the sides of the bracket 13.

The above-mentioned means of attachment 11 are preferably formed by clamping means, and better still by clamping means which tighten when the above-mentioned screws 10 are screwed tight, so that the securing means 4 are held tight. In the embodiments shown in figs. 2 to 4, said clamping means consist of clip elements 14 which function as clamping plates, each consisting of a flat part 15 with an opening 16, a curved counter-pressing part 17 which operates on the joining element 3, and a lip-shaped end 18 which hooks into an opening 19 in the bridging element 7.

It is clear that there is a clip element at either end of the bridging element 7. Figs. 5 to 8 show views of two securing means 4 connected by the bridging element 7 and a clip element 14, in order to make clear the structure of these elements. The securing means 4 and the bridging element 7 preferably form one part.

In fig. 6 it can be clearly seen that the openings 9 according to the invention are slot shaped.

The means 12, which lend lateral stability to the screws 10 fitted through the openings 9 in the coplanar parts 8, preferably consist of a washer 20, applied at each of said securing means 4, said washer having an opening 21 right through it, said opening being evenly shaped, in other words not long and narrow, but preferably round or essentially round with a diameter that enables a screw 10 to fit through it. Said washer is shown in detail in figs. 9 to 11.

By using such washers 20 placed between the clip elements 14 and the heads 22 of the respective screws 10, lateral stability is obtained, firstly for the screws 10 in the washers 20, thanks to the shape of the openings 21, and secondly for the washers 20 with respect to the end parts 8 and with respect to the clip elements 14, thanks to the clamping force with which the underneath 23 of the washer 20 is pressed against the surface underneath, in this case the top side 24 of the clip elements 14. It is clear that this also results in lateral stability of the screws 10 with respect to the end parts 8, irrespective of where the screws 10 pass through the slot shaped openings 9.

It is self-evident that the openings 16 in the clip elements 14 are also slot shaped. In order to increase the stability still further, locking means can be supplied which ensure that, when tightened, it is very difficult or impossible for the washers 20 to be displaced relative to the underlying surface. Said locking means can be formed by serrations 25 and 26 respectively in the underneath of the washer 20 and in the surface underneath, as shown in fig. 12, such that great lateral stability is achieved even when the tightening force is very slight, or in other words relative displacement between the washers and the constructive portions underneath the washers 20 is avoided.

In a variant, the locking means can also consist of a roughening of the material of at least one of the surfaces which fit together, e.g. by coarse shot blasting.

Preferably the locking means will at least provide stability in the longitudinal direction of the slot-shaped openings 9.

As shown in figs. 3, 9, 10 and 11, the washers 20 preferably have turned-down edges 27 and 28 which fit precisely over the parts underneath, namely the clip elements 14 and the end parts 8, so preventing any rotation of the washers 20 when the screws 10 are tightened. It is clear that, as shown in fig. 3, the height H of the edges 27 and 28 is preferably smaller than or equal to the distance G formed by the sum of the thicknesses of the end part 8 and the part 15.

The edges 27 and 28 are also in particular important in that they serve to strengthen and hold in the sides of at least the slotted part which is located directly under the washer 20. With such side edges 27 and 28, it is possible to utilise a relatively long slot with a reduced risk of outward distortion or bowing of the sides of the slot. The reinforcing effect of these edges 27 and 28 also permits the slotted parts to be quite narrow in width, thereby increasing the compactness of these parts.

Further, in order to prevent weak points occurring in the device 1, the washers 20 are preferably made such that the openings 9 and 16, whose shapes correspond, are completely closed, such that forces can also be transmitted via the washers 20. According to a particular embodiment, the openings 21 right through the washers 20 are eccentric, as shown in fig. 13. This has the advantage that, as shown in fig. 14, the openings 9 are always closed, even when the axis 29 of the screw 10 is close to one or other of the ends of the slot shaped opening 9, and moreover the washers 20 do not reach farther laterally than the underlying parts. It is then only necessary to place the corresponding washer 20 in the correct direction.

More particularly it can be seen from fig. 14 that even if the screw 10 is fully to the right, the opening is still closed on the left. Furthermore, on the right hand side the washer 20 does not project beyond the edge 30 of the underlying part.

Screws 10 with spherical heads 22 are preferably used in the device.

More particularly, screws with hollow heads are preferably used, as shown in fig. 15.

Although according to the invention it is not excluded that the screws 10 on the one hand and the washers 20 on the other should be made such that the screws 10 can be pushed freely through the openings in the corresponding washers 20, the ratio between the size of the opening in each washer 20 on the one hand, and the dimensions of the core and the thread of the screw on the other hand, are chosen such that said screw 10 can indeed be screwed through the opening in the corresponding washer 20, but cannot be pushed through it, which offers the advantage that, as shown in fig. 15, the corresponding washer 20 can rest on the top of the screw thread 31, which is easier when fitting the device.

In order to enable said screw 10 to be screwed through the opening 21, the walls of the opening 21 are preferably narrowed, for example chamfered by means of the chamfering 32 shown in figs. 10, 11 and 14, which also results in the contact surface between the head of the screw 10 and washer 20 being increased, if a screw with a rounded head is chosen.

It is clear that the invention also concerns a bridge as such, i.e. the combination of two securing elements 4 connected by a bridging element 7 and provided with the above-described means 12.

It is also clear that according to the invention, the distance between the locations A to F are not very critical, and that according to the invention a single bridge is suitable for bridging different distances, without losing the lateral stability of the screws 10.

For example, it is possible to use one bridge of 67 mm with a long and narrow opening of 11 mm, which can replace the existing bridges of 59 mm, 63 mm and 67 mm, while the bridge of 63 mm with a long and narrow opening of 11 mm can replace the bridges of 55 mm, 59 mm and 63 mm.

For the purpose of fitting the device 1 on a patient, 'screws 10 with a hollow or solid core can be used. If a screw with hollow core is used, it can be fitted over a pin 33, as shown in fig. 15, where the diameter of the pin 33 enables the hollow screw 10 to be slid over said pin 33.

When the device is being fitted, the pins 33 or suchlike are first pressed into the openings in the vertebrae 2 into which the screws are to be inserted.

Next, the securing means 4, and joining element 3 and the clip elements 14 are fitted. Subsequently the screws 10, preferably hollow, are slid down over the pins 33, while the washers 20 rest on the threads 31 of said screws. Once the screws 10 have been screwed partly into the bodies of the vertebrae 2, the pins 33 are withdrawn, whereupon the screws 10 can be tightened further. It is clear that this method of working is very simple, since the entire system is self-centering, or in other words each washer 20 is always perfectly underneath the head 22 of the corresponding screw 10.

In a variant, the above-mentioned means 12 can also consist of a series of different clip elements 14 with round openings at different distances, without a washer 20 being required. This embodiment is slightly less advantageous, but still offers the advantage that one bridge can be used for different sizes, while a suitably sized clip element 14 must be provided.

In a further variant, shown in figure 16, the bridged securing elements 4 are replaced by separate securing elements 4, wherein each separate securing element has one end part 8 with opening 9 and is associated with a respective one of the curved counter-pressing parts 17. Thus, each securing element can be attached independently to a respective side of the joining element 3. Of course a combination of bridged elements 4 and separate elements 4, attached to the same joining element 3 is possible.

It is obvious that all features of the securing elements 4 of the embodiments of figures 2-15 are also applicable to the embodiments in which separate securing elements 4 are used.

Of course, the end part 8 of each securing element 4 can be connected with its respective clip element 14 by means other than the lip-shaped end 18 and opening 19.

According to still another variant, which is not shown in the drawings, the attachment means 11 may be such that they do not co-operate with the aforesaid means 12. Indeed, the attachment between the securing element 4 and the joining element 3 can also be realized by means of separate screws or other separate attachment elements.

If no part 15 is provided, the washer 20 can be supported directly by the corresponding lip-shaped end 18, which in that case may be provided with the serrations 26 or other locking means.

The present invention is not limited to the examples described and the embodiments shown in the drawings; on the contrary, such a device for joining vertebrae can be made in various forms and dimensions while remaining within the scope of the invention, as defined in the accompanying claims.

Claims

1. Device for joining vertebrae, comprising firstly a joining element (3) ; secondly at least one securing element (4) with an end part (8) having an opening (9) therethrough for a screw (10) or other fastening member; and thirdly attachment means (11) for attaching said at least one securing element (4) to the joining element (3), characterised in that the opening (9) in the end part (8) is slot-shaped, and in that the securing element (4) is provided with means (12) which lend lateral stability to the screw (10) or other fastening member which is fitted through the opening (9) in the end part (8) .

2. Device according to claim 1, characterised in that the above-mentioned means (12) which provide the lateral stability consist of a washer (20) fitted directly underneath the head (22) of the above-mentioned screw

(10) , where the opening (21) in said washer (20) is so small that the screw (10) fits more or less exactly in it.

3. Device according to claim 2, characterised in that it is provided with locking means which prevent displacement of the washer (20) with respect to the underlying surface.

4. Device according to claim 3, characterised in that the locking means consist of serrations (25, 26) which mesh with each other, respectively on the underneath (23) of the washers (20) and on the underlying surface with which the washers (20) come in contact.

5. Device according to claim 3, characterised in that the locking means are formed by a roughening of the material, of at least one of the surfaces which fit together.

6. Device according to any of claims 2 to 5, characterised in that each washer (20) provides full closure of the opening (9, 16) in the part lying underneath it.

7. Device according to any of claims 2 to 6, characterised in that the opening (21) in the washers (20) are eccentric, i.e. being displaced sideways.

8. Device according to any of claims 2 to 7, characterised in that the washer (20) has turned-down edges (27, 28) which fit over the parts lying underneath.

9. Device according to any of claims 2 to 8, characterised in that use is made of screws (10) with a screw thread such that the washers (20) are each supported by the screw thread (31) of the corresponding screw (10) while the device is being fitted.

10. Device according to any of the above claims, characterised in that said attachment means (11) consist of clamping means.

11. Device according to claim 10, characterised in that the clamping means consist of one or more clip elements

(14) that can be tightened against the above-mentioned joining element (3) by means of the above-mentioned screws (10) .

12. Device according to claim 11, characterised in that each of the clip elements (14) consists of a flat part

(15) with an opening (16) , a counter-pressing part (17) and a lip shaped end (18) that engages in an opening (19) in the securing element (4) .

13. Device according to claim 12, characterised in that the openings (16) in the clip elements (14) are also long and narrow.

14. Device according to claim 12, characterised in that the shape of the openings (16) in the clip elements (14) corresponds to the shape of the openings (9) in the securing elements (4) .

15. Device according to any of the above claims, characterised in that it comprises one or more separate securing elements (4) which can be attached independently to the joining element (3) .

16. Device according to any of the above claims, characterised in that it comprises at least two securing elements (4) connected by a bridging element (7) .

17. Device according to claim 16, characterized in that said two securing elements (4) have coplanar end parts (8) .

18. Device according to claim 17, characterised in that the joining element (3) consists of a ring-shaped frame and that each of said two securing elements (4) is provided with attachment means (11) for attaching said securing element (4) at opposite sides of said frame.

19. Bridge, more particularly a bridge as applied and described in the above claims 16 to 18.