AU2003282181B2

AU2003282181B2 - Device for solidly connecting a part to a support and method of fitting one such device

Info

Publication number: AU2003282181B2
Application number: AU2003282181A
Authority: AU
Inventors: Robert Porcher
Original assignee: Stryker Trauma SA
Current assignee: Stryker European Holdings I LLC
Priority date: 2002-09-24
Filing date: 2003-09-22
Publication date: 2008-05-22
Anticipated expiration: 2023-09-22
Also published as: ATE347302T1; FR2844702A1; ES2278204T3; AU2003282181A1; FR2844702B1; DE60310263D1; JP4343841B2; HK1075380A1; DE60310263T2; EP1571971A2; WO2004028334A3; WO2004028334A2; JP2006500130A; EP1571971B1

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

Translation of PCT/FR03/02779 Device for solidly connecting a part to a support and Method of fitting of such a device The present invention relates to a device for solidly connecting a part, such as an osteosynthesis plate, to a support, such as a bone mass. The device has at least one fixing component taking the form of a threaded rod passing through an aperture housing a ring belonging to said part such that 9 it is screwed into the support material.

Screw-and-plate osteosynthesis systems must allow immobilizing one or more bone fragments in reference to others.

It is known to use spherical-head screws cooperating with a spherical housing housed in a plate and bringing the plate into compression over the bone until the friction of the plate on the bone stabilizes the assembly. These assemblies allow choice of the angle of implantation of screws during the operation and causing a return movement and a compression of a detached bone fragment. Certain of these systems allow, due to the oblong shape of the aperture, made in the plate, compression of one bone fragment on another. The shortcoming of these systems is their low resistance to compression stresses exerted parallel to the plane of the plate.

Use is also known of a second generation of screw-and-plate systems called monoaxial-locking and polyaxial-locking systems in which the strength of the assembly no longer depends on compression of the plate on the bone but on a fixation of the screw in the plate. These systems allow achieving assembly away from the bone with, for the more elaborate ones, the possibility of choosing the angle of implantation of screws during the operation while achieving strength sufficient for postoperative stresses.

One example of monoaxial-locking device is described in patent FR-A-2,739,1 51 One such device comprises a plate traversed by tapped tapered holes in which are wedged the tapered threaded heads of the screws at the end of tightening. One such system that achieves locking by wedging of a tapered thread into a tapped tapered hole has, as a problem, the fact that as the screw is engaged simultaneously in the plate and in the bone, the possible distance between plate and bone may no longer be reduced. Drawing back a bone fragment is thus impossible. Because of this, the distance between the plate and the bone must be set before the installation of the screw, which is sometimes difficult.

In existing monoaxial mechanisms, bone anchoring is sometimes improved by the introduction of screws with the axes between them not being parallel. However, unlike the divergent course a tension normal to the plate does not cause the latter to pull out. To achieve such orientation of the screws, the plate to be fixed to the support can be provided with holes with axis nonorthogonal to the surface of the plate such that the orientation of the screw is provided by the orientation of the hole in the plate. The surgeon then has therefore no freedom concerning the orientation of the screw to be fixed. This predetermined orientation may sometimes prove to be incompatible with anatomical constraints. Moreover, existing devices do not allow the plate and the support to be brought together optimally without impairing coaxiality between axis of the plate and axis of the internal thread.

One example of a polyaxial locking mechanism is specifically described in patent FR-A-2,790, 198 One such device comprises a plate equipped with a ring expanding radially during the threading of the screw to allow immobilization of the ring and then of the screw inside the hole of the plate. The expansion of the ring is obtained by a tapered threading of the screw and of the internal bore of the ring.

A system is likewise known through patent DE 100 39 767 comprising a ring with spherical external shape being able to be adjusted inside a plate comprising a spherical housing. The ring is traversed by a screw, whose head is housed in a bore of the ring. No blocking system is described for the screw.

U.S. Patent Application US-A-2001/0371 12 relates to a system comprising a ring whose outside shape is spherical, orientable inside a plate comprising a spherical housing. The ring is traversed by a screw, whose head is housed in a cylindrical bore of the ring. Locking is obtained by expansion of the head of the screw using an additional tapered screw.

0 Finally, U.S. Patent 5,531,554 relates to a system comprising a malleable-collar screw. The collar is restricted when it is driven into a tapered hole on the plate until it spreads beyond the said hole, since it expands due to elasticity to prevent the screw from being removed. Return movement of the collar of the screw to its initial shape also inhibits axial displacement of the screw in the sense of an extraction of the screw from the bore in the plate.

It should be noted that other systems achieve locking by introduction under force of the threaded head of the screw in the housing of the plate. The force necessary for the 00 0 deformation of the material in the housing is significant. Moreover, risks from N detachment of metal particles cannot be ruled out.

At least in its preferred form(s), the present invention provides a device for solidly connecting a part on a support, in which the design allows optimally bringing together the plate and the support, pre-operative orientation of the screw, and easy installation and removal of the assembly while offering good resistance to pull out and to 00 the stresses exerted parallel to the plane of the plate.

0 In a first aspect, the present invention provides a device for solidly connecting a 00 Spart, such as an osteosynthesis plate, on a support, such as a bone mass, comprising at 1o least one fixing element in the form of a threaded rod passing through a hole housing a Sring in the said part, said threaded rod to be screwed into the material of the support, the ring being ait constrictive ring in which a non-circular external profile of the ring cooperates with a non-circular internal profile of the hole of the part to cause, during rotational movement of the ring in the hole, a constriction of the ring ensuring the immobilization of the threaded rod and at the same time an immobilization by wedging of the ring in the hole.

One embodiment of such device allows easy installation of the screw that is not, before constriction of the ring, in contact with the ring. Moreover, bringing together the part and the support is done simply by screwing, the distance between part and support being able to be adjusted as needed. Finally, locking is done using a simple tool that ensures rotational driving of the ring.

In a second aspect, the present invention provides a method of installation of a device for solidly connecting a part, such as an osteosynthesis plate, to a support, such as a bone; using at least one fixing element in the form of a threaded rod passing through a hole housing a ring in the said part, said threaded rod to be screwed into the material of the support, as defined in the first aspect above, wherein the threaded rod is introduced into the ring disposed in the hole in the part, the rod is driven to its final position, then rotationally driving the ring to cause, through constriction of the ring, the immobilization of the rod driven in said hole.

Preferred embodiments of the invention will be described hereinafter, by way of examples only, with reference to the accompanying drawings, in which: FIG. 1 is a front view partially in section of the connection device of the present invention in the assembled state; FIG. 2 is a top view of the ring in its hole in the absence of any constriction of the ring; 1201747 I:TCW 00 0FIG. 3 is a top view of the ring in its hole in position of constriction of the ring; N FIG. 4 is a front view partially in section of the device of FIG. 1 with the constituent elements unassembled; and FIG. 5 is a front view partially in section of a second embodiment of a device according to the invention in unassembled state of the constituent elements.

There is shown an embodiment of the connection device of the present invention, 00 comprising a part 1 able to be solidly connected on a support S using at least one fixing 00 element 4. As mentioned above, this device is more specifically intended for the medical field. In 0c 1201747 I:TCW this case, the part 1 is an implant generally taking the form of a plate and the support S is at least one bone. Fixing the element 4 for its part comprises a rod threaded over at least part of its length. Rod 4, which ensures the solid connection of the part 1 on the support S, passes through a hole 2 of the part 1 and is anchored on the support S. The hole 2 of this part 1 is provided with a ring 3 traversed by the fixing element 4. According to the present invention, ring 3 can be constricted at the time of its rotational drive into the hole 2, this constriction of the ring 3 ensuring, generally by cooperation with the 9 head or end part of the thread of the rod 4, immobilization of the threaded rod 4 at the same time as immobilization by wedging ring 3 in the hole 2. This immobilization by wedging is achieved by friction of the external surface of the ring 3 against the internal surface of the hole 2. In effect, the non-circular external profile of the ring 3 cooperates with the non-circular internal profile of the hole 2 in the part 1 to cause, at the same time as the constriction of the ring, the wedging of the ring 3 in the hole 2. It should be noted that the term circular must be understood in its strictest sense, that is to say where all points are equidistant from a fixed point. An example of possible embodiment of one such profile is specifically given in FIGS. 2 and 3. Different profiles more similar to a circular profile may be envisaged. Also, a profile comprising two successive spiral parts may be envisaged for the external profile of the ring and internal profile of the hole 2. These profiles may or may not be identical in shape. To facilitate constriction or circular narrowing of the ring 3 around the rod 4, this ring 3 is slotted. The slot is more specifically shown as 5 in FIGS. 2 and 3. Constriction may also be achieved by deformation of deformable zones inside the body of the said ring. Placing a slot however constitutes the simplest solution to achieve constriction, that is to say circular narrowing of the ring around the threaded rod 4. Constriction takes place preferably by narrowing of the ring around the head or the end portion of threaded rod 4 that is generally unthreaded. This smooth head may have any shape.

Two methods for using the embodiments of the invention may be envisaged.

In a first embodiment of the invention according to FIG. 1, the 9 ring 3 is orientably mounted inside the hole 2 in the part 1.

Furthermore, the ring 3 takes the shape of a ring having a generally spherical outer surface divided by a slot being housed inside a bore 2 generally spherical in cross-section in a shape complementary to the hole 2 of the part 1. The sphericity allows any axial orientation of the screw inside the hole to be achieved. Thus, the ring constitutes the equivalent of a pivot.

The front face of the ring 3 is provided with raised or projecting elements, such as the flutes 6, fitted to cooperate with a rotational drive tool for the ring 3. This ring 3 may be premounted in the hole 2 of the part 1, such premounting being done at the factory. This ring 3 may still be movably mounted in the hole 2 of the part 1. The threaded rod 4 comprises, on its free end for screwing, at least one cavity 7, recessed or raised, intended to cooperate with a screwdriving tool. In the example shown, this rod or screw 4 is provided, at its drive end, with a prismatic axial cavity suitable to receive the head of a rotational drive tool for the rod or screw 4. The head of this threaded rod is provided, at its drive end or in the vicinity of this latter, with a shoulder 8 which may rest after the screw is fully inserted on the front face of the ring 3 to allow mating of the part 1 with its support S. This shoulder is more specifically shown in FIG. 1. One of the advantages of this device is to be able to vary as needed the distance between part and support S even though the locking of the threaded rod 4 is guaranteed regardless of the nature or of the quality of the interface between part and support

S.

In another embodiment of the invention shown in FIG. 5, the part 1 is provided with a pre-oriented hole provided with an internal shoulder 9 for retaining of the ring 3 inside the hole. This shoulder, housed in the bottom of the bore of the part 1, as a plate, retains the ring 3 during the compression phase of the plate on the bone during a return movement of the bone fragment.

The method of installation of one such device is the following.

It consists of introducing the threaded rod 4 into the ring 3, the latter already disposed in the hole 2 of the part 1. After screw threaded rod 4 is driven to its final position then ring 3 is rotationally driven to ensure, by constriction of the ring 3, immobilization of the screw in the hole 2.

In a more detailed fashion, the phases of the installation of rod 4 are generally the following. The surgeon at first carries out a forming of the plate with special forceps maintaining the integrity of the bores in the plate. The plate is then positioned on the bone. A drill guide is introduced into the ring housed inside the plate to allow orientation of the ring based on the orientation that surgeon wishes the screw to have. The surgeon then proceeds with drill using the drilling guide that allows positioning the axis of the threaded rod in the axis of the ring in such a way that the axis of the rod and axis of the ring are absolutely coincident. The drilled length is measured using a gauge. A threaded rod of matching length is then chosen based on the length measured by the gauge. The screw is installed by rotational driving using a screwdriver. This screwing takes place until possible mating of the plate on the bone or drawing back of a bone segment by continuing to screw so the shoulder of screw head is in contact with the front face of ring. The plate 1 comprising generally a plurality of holes and the group of screws is installed. Once the group of screws is positioned, all the screws can then be locked by tightening through rotational driving of each ring using a fitted tool.

In the use of one connecting device for solidly connecting the plate to the screw, no unscrewing, backward movement, or swiveling of the screw in its hole is noted. The screw is thus immobilized along three axis or directions of movement, namely the direction of backward movement, the rotation of the screw around its axis, and the axis of rotational immobilization around the center of the sphere. The radial force that is applied at the time of rotational driving of the ring between external wall of the ring and the inside wall of the hole 2, is preferably exerted at at least three points. Constriction is generally achieved by narrowing of the slot.

Claims

2. The device according to claim 1, wherein the ring is slotted. S3. The device according to any of claims 1 or 2, wherein the ring is mounted insidle the hole of the part in a orientable manner.
4. The device according to any one of claims 1 to 3, wherein the ring takes the form of a slotted ring having a generally spherical outer surface, said ring being housed inside a generally spherical complementary surface of said hole of said part. The device according to any one of claims 1 to 4, wherein the front face of the ring is fitted with embossed or hollowed coupling elements such as flutes, shaped to cooperate 'with a rotational drive tool for the ring.
6. The device according to any one of claims 1 to 5, wherein the ring is premounted in the hole of the part.
7. The device according to any one of claims 1 to 5, wherein said ring is removably mounted in the hole of the part.
8. The device according to any one of claims 1 to 7, wherein the threaded rod has on its free end for screwing at least one embossed or hollowed coupling element intended to cooperate with a driving tool.
9. The device according to any one of claims 1 to 8, wherein the threaded rod is provided, on its drive end, with a shoulder, engagable with the front face of the ring, to allow a mating of the part with its support. The device according to claim 1 or 2, wherein the part is provided with a pre-oriented hole provided with an internal shoulder for retaining of the ring inside the hole of the part.
11. A method of installation of a device for solidly connecting a part, such as an osteosynthesis plate, to a support, such as a bone; using at least one fixing element in the form of a threaded rod passing through a hole housing a ring in the said part, said threaded rod to be screwed into the material of the support, according to any one of 1201747 I:TCW 00 claims 1 to 10, wherein the threaded rod is introduced into the ring disposed in the hole in the part, the rod is driven to its final position, then rotationally driving the ring to cause, Sthrough constriction of the ring, the immobilization of the rod driven in said hole. _12. A device for solidly connecting a part, said device substantially as s hereinbefore described with reference to Figs. 1-4 or Fig. 5 of the accompanying drawings. 00 13. A method of installation of a device for solidly connecting a part, said C 0 method substantially as hereinbefore described with reference to Figs. 1-4 or Fig. 5 of the Saccompanying drawings. 0 Dated 18 April, 2008 Numedic Patent Attorneys for the Applicant/Nominated Person SPRUSON FERGUSON 1201747 I:TCW