HK1075380A1 - Device for solidly connecting a part to a support - Google Patents

Abstract

The device for fixing a synthetic bone plate (1) on a bone (S) comprises a threaded rod (4) passing through a hole (2) housing a plate collar (3) so as to be screwed into the bone. The constricted collar has a non-circular external profile which engages the non-circular hole to cause, during rotation of the collar, whilst wedging the collar in the hole, a constriction of the collar ensuring the immobilization of the threaded rod.

Description

The present invention relates to a device for the solidification of a part, such as an osteosynthetic plate, on a support, such as a bone mass, by means of at least one fixing organ affecting the shape of a threaded rod through an opening housing a ring of the part to be screwed into the support material.

Screw and plate osteosynthesis systems must allow one or more bone fragments to be immobilized relative to each other. Screws with a spherical base head cooperating with a spherical housing in a plate and bringing the plate into compression on the bone until the friction of the plate on the bone stabilizes the whole are known to be used. These mountings allow the angle of implantation of the screws during the procedure to be chosen and to operate a rappel and compression of an isolated bone fragment.

A second generation of so-called monoaxial and polyaxial locking systems is also known to be used, in which the strength of the mounting is no longer based on a compression of the plate on the bone but on a fixing of the screw in the plate.

An example of a monoaxial locking device is described in patent FR-A-2.739.151. Such a device consists of a plate through which conical tapered holes are cut into which the tapered threaded heads of the screws at the end of the screw come to be stuck. Such a system which obtains a lock by trapping a tapered thread in a tapered threaded hole has the disadvantage that since the screw is engaged in both the plate and the bone, the possible distance between plate and bone can no longer be reduced. The recall of a bone fragment is therefore impossible.

In existing monoaxial devices, bone anchoring is sometimes improved by introducing screws into non-parallel axes, but instead at a divergent rate so that normal traction to the plate does not result in any tearing of the plate. To achieve such a screw orientation, non-orthogonal axis holes may be made in the plate to be fixed to the support so that the orientation of the screw is provided by the orifice in the plate. The surgeon then has no freedom as to the orientation of the screw to be fixed. However, this predetermined orientation may sometimes be incompatible with the anatomical axes.

An example of a polyaxial locking device is described in particular in FR-A-2.790.198 such a device consists of a plate equipped with a ring expanding radially during the screw screw in order to allow the ring and consequently the screw to be immobilized inside the plate hole.

It is also known through patent DE 100 39 767 a system comprising an outer ring of spherical shape which can be oriented inside a plate comprising a spherical housing.

US-A1-2001/037112 describes a system consisting of a ring of spherical outer shape that can be oriented inside a plate with a spherical housing. The ring is traversed by a screw, the head of which is lodged in a cylindrical groove of the ring.

Finally, US-A-5.531.554 describes a system with a deformable collar screw, which is constricted when it is sunk into a conical hole in the plate until it extends beyond the hole, then expands by elasticity to prevent the screw from being disassembled.

It should be noted that other systems achieve locking by forceful introduction of the threaded head of the screw into the plate housing. The force required to deform the material in the housing is significant.

The purpose of the present invention is therefore to propose a device for the solidisation of a part on a support, the design of which allows for optimal coupling of the plate and the support, a per-operation orientation of the screw and easy installation and disassembly of the whole while offering good resistance to tearing and stresses applied parallel to the plane of the plate.

To this end, the invention concerns a device for fastening a part, such as an osteosynthetic plate, to a support, such as a bone mass, by means of at least one fixing organ affecting the shape of a threaded rod through an opening housing a ring of that part to be screwed into the support material, characterised by the fact that the ring is a constricting ring whose non-circular outer profile cooperates with the non-circular inner profile of the part orifice to cause, when the ring is rotated in the orifice, simultaneously with the immobilization by coincidence of the ring in the orifice, a constriction of the constricting rod's immobilization.

The device allows the screw to be easily attached without being in contact with the ring before the ring is constricted, and the part is simply screwed to its support, the distance between plate and support being adjustable at will, and the locking is done by means of a simple tool which ensures the rotational drive of the ring.

The device according to the invention allows the use of a method of attaching a piece-solidarising device, such as an osteosynthetic plate, to a support, such as a bone mass, by means of at least one fixing organ affecting the shape of a threaded rod through an opening housing a ring of the said piece to be screwed into the support material, where the process consists of inserting the threaded rod into the ring itself arranged in the hole of the piece, then screwing the threaded rod to its final screwing position and then rotating the ring in such a way as to ensure that the ring is perricated to ensure the immobilization of the threaded rod in the said hole.

The invention will be clearly understood by reading the following description of examples of realization, referring to the attached drawings in which: Figure 1 shows a partially cut face view of a device covered by the invention in the assembled state of its constituent parts;Figure 2 shows a top view of the ring in its orifice without any constriction of the ring on the screw;Figure 3 shows a top view of the ring in its orifice in the constriction position of the ring;Figure 4 shows a partially cut face view of the device covered by the invention in the unassembled state of its constituent parts andFigure 5 shows a partially cut face view of another way of making a device conforming to the invention in the assembled state of its constituent parts.

The device is a part 1 which can be fastened to a support S by means of at least one fixing organ 4. As mentioned above, this device is more specifically intended for the medical field. In this case, part 1 is an implant which generally affects the shape of a plate and the support S at least one bone. The fixing organ 4 is a rod threaded along at least part of its length which can still be aimed.The ring 2 of this part 1 is fitted with a ring 3 through which the fixing organ 4 passes. Characteristically for the invention, this ring is a constrictive ring 3 when driven in rotation in the opening 2, this constriction of the ring 3 ensuring, usually by cooperation with the head or portion of the end of the rod screwing, an immobilization of the rod 4 threaded in parallel with an immobilization of the ring 3 through the opening 2. This coincidence by immobilization is achieved by friction of the outer surface of the ring 3 against the inner surface of the rod 2.The non-circular outer profile of ring 3 cooperates with the non-circular inner profile of hole 2 in part 1 to cause, in parallel with the ring constriction, a trapping of ring 3 in hole 2. It should be noted that the term circular must be taken in its strictest sense, i.e. all points of which are equidistant from a fixed point.Thus, a profile consisting of two successive spiral outlets can be considered for the outer profile of the ring and the inner profile of the orifice 2. These profiles may be of identical shape or not. To facilitate the constriction or circular tightening of ring 3 around rod 4, this ring 3 is split. The slot is more specifically represented as 5 in Figures 2 and 3.This is a circular tightening of the ring around the threaded rod 4. The tightening is preferably done by tightening the ring around the head or the end portion of the threaded rod 4 which is usually unthreaded. This smooth head can be of any shape.

Two ways of implementing the scheme can be considered.

In a first embodiment of the invention as shown in Figure 1, the ring 3 is mounted vertically inside the opening 2 of part 1. Thus, the ring 3 affects the shape of a split spherical general-looking ring lodged inside a spherical general-looking bolt of complementary shape of the opening 2 of part 1. The sphericity allows some orientation of the screw inside the opening, the ring being the equivalent of a ball.

The front of ring 3 is fitted with raised or protruding elements, such as grooves 6, suitable for cooperation with a rotating drive tool of ring 3. This ring 3 can be pre-mounted in hole 2 of part 1 and this pre-mounting is carried out in the factory. This ring 3 can also be mounted removably in hole 2 of part 1. The threaded rod 4 has at its end free of screws at least one hollow or raised footprint 7 for cooperation with a screwing tool.In the example shown, this rod 4 has a prismatic axial cavity at its screw end suitable for the head of a drive tool when the rod is rotating. The head of this threaded rod is equipped, at its screw-free end or in the vicinity of the screw-free end, with a shoulder 8 which may be supported in the screw-end position on the front face of the ring 3 to allow the piece 1 to be brought closer to its support S. This winding is more particularly shown in Figure 1.

In another embodiment of the invention shown in Figure 5, part 1 is fitted with a pre-oriented orifice with an internal shoulder 9 to hold the ring 3 inside the orifice, which, in the back of the plate-shaped part 1's groove, holds the ring 3 during the compression phase of the plate on the bone or during a recall of the bone fragment.

The method of installation of such a device is as follows: threaded rod 4 is inserted into ring 3 which is itself placed in hole 2 of part 1, threaded rod 4 is screwed to its final screwing position and then the ring 3 is rotated so as to ensure, by constriction of the ring 3, that the screw is fixed in hole 2.

In more detail, the stages of placement of the rod 4 are usually as follows: The surgeon first forms the plate with special forceps that maintain the integrity of the grooves in the plate; the plate is then placed on the bone; a drill guide is inserted into the ring housed inside the plate so that the ring can be oriented according to the orientation the surgeon wishes to give the screw; the surgeon then drills through the drill guide, which positions the hole of the threaded rod in the ring axis so that the drill isThe length of the threaded rod is measured by means of a gauge. A threaded rod of suitable length is then chosen according to the length measured by the gauge. The screw is set up by rotating drive by means of a screwdriver. This screwing is carried out until the plate eventually approaches the bone or a bone segment is recalled by continuing to screw while the screw head is in contact with the front face of the ring. The plate usually has several orifices, all the screws are set up.Once all the screws are in place, all the screws can then be locked by rotating each ring with a suitable tool.

In the case of such a solidarisation device, no unscrewing, retraction or pivoting of the screw is observed in its orifice. The screw is thus immobilized along at least three axes, namely the axis of retraction, the axis of rotation of the screw on its axis and the axis of immobilization rotating around the centre of the sphere. The radial force applied when the ring is rotated between the outer wall of the ring and the inner wall of orifice 2 is preferably exerted at at least three points.

Claims (10)

1. A device for solidly connecting a part (1), such as an osteosynthesis plate, on a support (S), such as a bone mass, comprising at least one fixing element (4) in the form of a threaded rod passing through a hole (2) housing a ring (3) in the said part (1), to be screwed into the material of the support (S), characterized in that the ring (3) is a constrictive ring having a non-circular external profile cooperating with a non-circular internal profile of the hole (2) of the part (1) to cause, during rotational movement of the ring (3) in the hole (2), at the same time an immobilization by wedging of the ring (3) in the hole (2) as well as a constriction of the ring (3) ensuring the immobilization of the threaded rod (4).
2. The device according to claim 1, wherein the ring (3) is slotted.
3. The device according to any of claims 1 or 2, wherein the ring (3) is mounted inside the hole (2) of the part (1) in a orientable manner.
4. The device according to any of claims 1 to 3, wherein the ring takes the form of a slotted ring (3) having a generally spherical outer surface being housed inside a generally spherical bore having a complementary form to said hole (2) of part (1).
5. The device according to any of claims 1 to 4, wherein the front face of the ring (3) is fitted with embossed or hollowed coupling elements such as flutes (6), shaped to cooperate with a rotational drive tool for the ring (3).
6. The device according to any of claims 1 to 5, wherein the ring (3) is premounted in the hole (2) of the part (1).
7. The device according to any of claims 1 to 5, wherein said ring (3) is removably mounted in the hole (2) of the part (1).
8. The device according to any of claims 1 to 7, wherein the threaded rod (4) has on its free end for screwing at least one embossed or hollowed recess (7) intended to cooperate with a driving tool.
9. The device according to any of claims 1 to 8, wherein the threaded rod (4) is provided, on its free end for screwing, with a shoulder (8), being engagable with the front face of the ring (3) at the position at the end of screwing, to allow a mating of the part (1) with its support (5).
10. The device according to claim 1 or 2, wherein the part (1) is provided with a pre-oriented hole (2) provided with an internal shoulder (9) for retaining of the ring (3) inside the hole (2) of the part (1).