AU2003282181A1

AU2003282181A1 - Device for solidly connecting a part to a support and method of fitting one such device

Info

Publication number: AU2003282181A1
Application number: AU2003282181A
Authority: AU
Inventors: Robert Porcher
Original assignee: NUMEDIC
Current assignee: Stryker European Holdings I LLC
Priority date: 2002-09-24
Filing date: 2003-09-22
Publication date: 2004-04-19
Anticipated expiration: 2023-09-22
Also published as: EP1571971B1; DE60310263T2; FR2844702B1; JP2006500130A; JP4343841B2; ATE347302T1; ES2278204T3; AU2003282181B2; DE60310263D1; WO2004028334A3; FR2844702A1; WO2004028334A2; EP1571971A2; HK1075380A1

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

Gotthardstrasse 53 ISLER & PEDRAZZINI AG Postfach 0rich ....

....

CH - 8023 Z~rich f' *A\JNT_&, RKENANW.I.TE pAENT& TRADEMARK ATTORNEYS Telefon + 41 - 1 - 283 47 00 PAET-,AR EAN AJ : AM W URA Telefax + 41 - 1 - 283 47 47 mail@islerpedrazzini.ch www.islerpedrazzini. ch DECLARATION I, Michael Liebetanz, Dipl. Phys., European Patent Attorney, work ing with Isler & Pedrazzini AG, do hereby solemnly and sincerely declare: THAT I am conversant with the French and English languages; and THAT to the best of my knowledge and belief the attached docu ment is a true and correct translation from French into English of PCT/FR 2003/002779 in the name of Numedic. Signed this 15th day of April 2005 Michael Liebetanz Michael Liebetanz 1 Translation of PCT/FRO3/02779 Device for solidly connecting a part to a support and Method of fitting of such a device 5 The present invention relates to a device for solidly connect ing 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 10 an aperture housing a ring belonging to said part such that it is screwed into the support material. Screw-and-plate osteosynthesis systems must allow immobi lizing one or more bone fragments in reference to others. 15 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 20 the operation and causing a return movement and a compression of a detached bone fragment. Certain of these systems al low, 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 25 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 sys 30 tems in which the strength of the assembly no longer de pends 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 2 elaborate ones, the possibility of choosing the angle of implantation of screws during the operation while achieving strength sufficient for postoperative stresses. 5 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 tighten ing. One such system that achieves locking by wedging of a 10 tapered thread into a tapped tapered hole has, as a prob lem, 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 15 between the plate and the bone must be set before the in stallation 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 20 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 non orthogonal to the surface of the plate such that the orientation 25 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 orien tation may sometimes prove to be incompatible with anatomical constraints. Moreover, existing devices do not allow the plate 30 and the support to be brought together optimally without im pairing coaxiality between axis of the plate and axis of the in ternal thread.

3 One example of a polyaxial locking mechanism is specifically de scribed in patent FR-A-2,790, 198 . One such device comprises a plate equipped with a ring expanding radially during the thread ing of the screw to allow immobilization of the ring and then of 5 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 compris 10 ing a ring with spherical external shape being able to be ad justed 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. 15 U.S. Patent Application US-Al-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 trav ersed by a screw, whose head is housed in a cylindrical bore of the ring. Locking is obtained by expansion of the head of the 20 screw using an additional tapered screw. 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 be 25 yond the said hole, since it expands due to elasticity to pre vent the screw from being removed. Return movement of the collar of the screw to its initial shape also inhibits axial displace ment of the screw in the sense of an extraction of the screw from the bore in the plate. 30 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 4 deformation of the material in the housing is significant. Moreover, risks from detachment of metal particles cannot be ruled out. 5 One aspect of the present invention is thus to propose 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 in stallation and removal of the assembly while offering good re 10 sistance to pull out and to the stresses exerted parallel to the plane of the plate. For this purpose, the invention has as object a device for solidly connecting a part, such as an osteosynthesis plate, 15 to a support, such as a bone mass, using at least one fix ing element in the form of a threaded rod passing through a hole housing a ring of said part for screwing into the sup port material characterized in that the ring is a constric tion ring whose non-circular external profile cooperates 20 with the non-circular internal profile of the hole of the part by causing, at the time of rotational driving of the ring in the hole, at the same time as immobilization by wedging of the ring in the hole, constriction of the ring ensuring the immobilization of the threaded rod. 25 One 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 30 able to be adjusted as needed. Finally, locking is done using a simple tool that ensures rotational driving of the ring. The invention has as a further aspect a method of installa- 5 tion of a device for solidly connecting a part, such as an osteosynthesis plate, on a support, such as a bone mass, using at least one fixing element in the form of a threaded rod passing through a hole housing a ring of said part to 5 be screwed into the support material, characterized in that the method comprises introducing the threaded rod into the ring itself disposed in the hole in the part, then to drive the threaded rod to its final screwed in position and then to rota tionally drive or turn the ring to ensure by constriction 10 of the ring around the threaded rod to immobilize the threaded rod in the hole. The invention will be well understood by reading the follow ing description of embodiments, in reference to the included 15 drawings in which: FIG. 1 is a front view partially in section of the con nection device of the present invention in the assembled state; FIG. 2 is a top view of the ring in its hole in the ab 20 sence of any constriction of the ring; FIG. 3 is a top view of the ring in its hole in position of constriction of the ring; FIG. 4 is a front view partially in section of the device of FIG. 1 with the constituent elements 25 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. 30 There is shown the connection device of the present invention, comprising a part 1 able to be solidly connected on a support S using at least one fixing element 4. As mentioned above, this device is more specifically intended for the medical field. In 6 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 ele ment 4 for its part comprises a rod threaded over at least part of its length. Rod 4, which ensures the solid connection of the 5 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. Ac cording to the present invention, ring 3 can be constricted at the time of its rotational drive into the hole 2, this constric 10 tion of the ring 3 ensuring, generally by cooperation with the 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 15 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 20 noted that the term circular must be understood in its strictest sense, that is to say where all points are equi distant from a fixed point. An example of possible embodi ment of one such profile is specifically given in FIGS. 2 and 3. Different profiles more similar to a circular pro 25 file may be envisaged. Also, a profile comprising two succes sive 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 30 is slotted. The slot is more specifically shown as 5 in FIGS. 2 and 3. Constriction may also be achieved by deformation of de formable zones inside the body of the said ring. Placing a slot however constitutes the simplest solution to achieve constric- 7 tion, 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 5 shape. Two methods for using the embodiments of the invention may be envisaged. 10 In a first embodiment of the invention according to FIG. 1, the 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 gen erally spherical outer surface divided by a slot being housed inside a bore 2 generally spherical in cross-section in a shape 15 complementary to the hole 2 of the part 1. The sphericity al lows any axial orientation of the screw inside the hole to be achieved. Thus, the ring constitutes the equivalent of a pivot. 20 The front face of the ring 3 is provided with raised or project ing elements, such as the flutes 6, fitted to cooperate with a rotational drive tool for the ring 3. This ring 3 may be pre mounted 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 25 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, in tended 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 rota 30 tional 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 8 of the part 1 with its support S. This shoulder is more specifi cally shown in FIG. 1. One of the advantages of this device is to be able to vary as needed the distance between part and sup port S even though the locking of the threaded rod 4 is guaran 5 teed 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 10 an internal shoulder 9 for retaining of the ring 3 inside S 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. 15 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 20 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 25 out a forming of the plate with special forceps maintaining the integrity of the bores in the plate. The plate is then posi tioned 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 30 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 9 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 possi 5 ble 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 posi 10 tioned, 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 swivel 15 ing of the screw in its hole is noted. The screw is thus immobi lized along three axis or directions of movement, namely the di rection 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 20 time of rotational driving of the ring between external wall of the ring and the inside wall of the hole 2, is preferably ex erted at at least three points. Constriction is generally achieved by narrowing of the slot.

Claims

1. A device for solidly connecting a part (1), such as an osteosynthesis plate, on a support (5), such as a bone 5 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), said threaded rod to be screwed into the material of the support (S), characterized in that the ring (3) is a constrictive ring in which a non 10 circular external profile of the ring cooperates 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), a constriction of the ring (3) ensuring the immobi lization of the threaded rod (4) and at the same time an 15 immobilization by wedging of the ring (3) in the hole (2).

2. The device according to claim 1, wherein the ring (3) is slotted. 20

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 25 the ring takes the form of a slotted ring (3) having a generally spherical outer surface, said ring being housed inside a generally spherical complementary surface of said hole (2) of part (1). 30

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). 11

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). 5

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 10 the threaded rod (4) has on its free end for screwing at least one embossed or hollowed coupling element (7) in tended to cooperate with a driving tool.

9. The device according to any of claims 1 to 8, wherein 15 the threaded rod (4) is provided, on its drive end, with a shoulder (8), engagable with the front face of the ring (3), to allow a mating of the part (1) with its support (5). 20

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) in side the hole (2) of the part (1). 25

11. A method of installation of a device for solidly con necting a part (1), such as an osteosynthesis plate, to a support (S), such as a bone; using at least one fixing ele ment (4) in the form of a threaded rod passing through a hole (2) housing a ring (3) in the said part (1), said 30 threaded rod to be screwed into the material of the sup port, according to one of claims 1 to 10, characterized in that the threaded rod (4) is introduced into the ring (3) disposed in the hole (2) in the part (1), in that the rod 12 (4) is driven to its final position then rotationally driving the ring (3) to cause through constriction of the ring (3) the immobilization of the rod (4) drien in said hole (2).