WO1999044527A1

WO1999044527A1 - Backbone osteosynthesis system with ligament

Info

Publication number: WO1999044527A1
Application number: PCT/FR1999/000469
Authority: WO
Inventors: Pierre Ange Moreno
Original assignee: Dimso (Distribution Medicale Du Sud-Ouest)
Priority date: 1998-03-04
Filing date: 1999-03-03
Publication date: 1999-09-10
Also published as: FR2775583A1; AU2731499A; FR2775583B1

Abstract

The invention concerns a vertebral osteosynthesis system comprising at least a member to be anchored (2) to a vertebra, an element linking (23) the member to another anchoring member (3), and a screw (16) for co-operating with the anchoring member (2) to clamp the linking element (23) on the anchoring member, the linking element (23) having a deformable transverse cross-section, the system comprising a deformable sleeve (24) for receiving the linking element (23). The sleeve receiving the linking element is capable of being clamped by the screw (16) on the anchoring member (2).

Description

^• 'SYSTEM FOR OSTEOSYNTHESIS OF THE SPINAL WITH LIGAMENT ".

The invention relates to osteosynthesis systems ¹ to the spine.

Document FR-2 659 546 discloses a spinal osteosynthesis system, comprising anchoring members each having two internally threaded branches and capable of receiving between them a rigid rod for connecting the anchoring members. A split ring threaded on the stem is housed between the branches. A screw cooperates with the thread of the branches to tighten the ring and the rod on the anchoring member.

A cap prohibits the separation of the branches from one another for this purpose. This system is of simple constitution. It is easy and quick to assemble during an intervention. Once installed, this system constitutes an entirely rigid assembly.

An object of one invention is to provide an osteosynthesis system of a different type, in particular of simple constitution, easy and quick to assemble and having once installed a mechanical behavior different from that of the above-mentioned system.

Also known from document EP-0 669 109 is an osteosynthesis system in which an elastic connecting element is received in the head of the anchoring members and is tightened there by means of a screw. This system partially achieves the above object. However, to effectively immobilize the connecting element on the anchoring member, it is necessary to tighten the screw strongly. However, under these conditions, there is a risk of damaging the elastic connecting element and of facilitating its rupture.

Another object of one present invention is therefore to provide a system ¹ for osteosynthesis a robust fixing of the anchoring members to the connecting member without the risk of breaking it. With a view to achieving these aims, a system of vertebral osteosynthesis is provided according to the invention, comprising at least one member for anchoring to a vertebra, an element for connecting the member to another anchoring member, and a screw adapted to cooperate with the anchoring member to clamp the connecting element on the anchor member, the connecting member being of cross-section ^deformable, the system comprising a deformable sleeve adapted to receive the 'connecting element, wherein the sleeve receiving the connecting element is adapted to be tightened by the screw on the anchoring member.

Thus, the system has a simple constitution. It is easy and quick to assemble during an intervention and allows the attachment to the anchoring members of a flexible connecting element. Such an element, working in tension, but little or no compression, torsion and bending, gives the system a mechanical behavior different from that obtained with a rigid rod. The system may include one or more connecting elements with a deformable section. Alternatively, these can be placed in series with one or more rigid connecting elements on different sections to ensure a transition in the distribution of stresses. In this case, all of the anchoring members may advantageously be of the same standard type for indifferently receiving the deformable connecting element or a rigid connecting element.

In addition, thanks to the sleeve, damage to the connecting element is avoided during tightening of the screw while allowing robust tightening. Indeed, the sleeve ensures a distribution of the load of the screw on the flexible connecting element. In addition, it avoids direct contact of the screw on the flexible connecting element, thereby reducing the risk of breaking initiation. In addition, it facilitates the wedging of the connecting element by the screw, the sleeve providing a large contact surface on the flexible connecting element. In particular, provision may be made for the sleeve to be crushed on the connecting element during tightening.

Advantageously, the connecting element is flexible. Advantageously, the connecting element comprises a ligament or a cable.

Advantageously, the anchoring member comprises two branches adapted to receive between them the connecting element and having a thread for cooperating with the screw.

Advantageously, the sleeve has a closed cross section.

Advantageously, the sleeve is able to receive at most one longitudinal section of the connecting element. Thus, the connecting element connects two anchoring members by a single section.

Advantageously, the sleeve has an internal face having at least one flared end.

This facilitates the introduction of the connecting element into the sleeve.

Advantageously, the sleeve has an external face having a median section of narrowed section.

This improves the blocking of the sleeve in the anchoring member against sliding. Advantageously, the screw has a lower face intended to extend on the side of one connecting element and of substantially spherical shape.

This prevents damage to the connecting element or the sleeve during tightening. The system may also have one or more of the following characteristics: - it comprises a member for anchoring to a vertebra capable of being fixed to a rigid connecting element connected to a second anchoring member and comprising a single lateral fixing part suitable to connect simultaneously the member with a flexible connecting element connected to a third anchoring member;

the anchoring member comprises a body capable of receiving the rigid connecting element and a ring capable of being mounted on the body and carrying the fixing part, the ring having a stop for its blocking in rotation relative to the body ; the stop is arranged to bear against the rigid connecting element; - The stop includes a cylindrical part;

- The body comprises two branches adapted to receive between them the rigid connecting element and to cooperate with a screw for fixing the rigid connecting element, the ring being able to be mounted on the branches; - The fixing part has an orifice adapted to receive the flexible connecting element;

- the orifice has a flared edge;

- The flared edge extends on one side of the fixing part opposite the stop; and - the orifice is located at the right or at a location provided for the rigid connecting element.

Other characteristics and advantages of the invention will become apparent in the following description of a preferred embodiment given by way of nonlimiting example. In the accompanying drawings:

- Figure 1 is a partial perspective view of an osteosynthesis system according to the invention; Figures 2 and 3 are partial perspective views showing one of the anchoring members of Figure 1 respectively in the exploded state and in the assembled state;

- Figures 4 and 5 are respectively perspective and side views of the sleeve of Figures 2 and 3;

- Figure 6 is a partial perspective view on a larger scale of the other anchor member of Figure 1; and FIG. 7 is a perspective view of the ring of the member in FIG. 6.

Illustrated in the figures is a spinal osteosynthesis system according to the invention. This system comprises anchoring members 23, only two members having been shown, each comprising a pedicle screw 4 adapted to be screwed into a vertebra or part of the respective vertebra of the column to be arthrodesised. Each screw 4 has an elongated rectilinear threaded body to be screwed into the vertebra, and a head 6 having two branches 8 extending opposite and at a distance from each other. In a manner known per se, the branches 8 define between them a housing adapted to receive a connecting element connecting several screws 4 to each other.

The two branches 8 have a cylindrical external face 10 with circular section, the two cylinders having for axis a longitudinal axis of the body of the screw 4. Each anchoring member 2, 3 comprises a cap 12 having a cylindrical internal face with circular section adapted to be engaged externally on the two branches 8 resting on their free upper end, in order to prevent their mutual separation. The branches 8 have a threaded internal face 14 coaxial with the body of the screw. Each anchoring member 2, 3 also comprises a clamping screw 16 having an external thread 18 adapted to engage with the internal thread 14 of the branches 8. An upper face of the clamping screw 16 has a cavity 20 for maneuvering of the clamping screw using a tool. The cap 12 has an orifice for tightening the screw once the cap is in place. For the assembly of each anchoring member, the connecting element between the branches 8 is introduced, then the clamping screw 16 is engaged with the branches 8 and the cap 12 is installed. tightening the screw 16 through the cap, the screw 16 tightens the connecting element against the bottom of the head of the pedicle screw 4 and thus rigidly immobilize the anchoring member 2, 3 relative to the connecting element. The above characteristics are known per se from documents FR-2 659 546 and FR-2 642 643.

Referring to Figures 1 to 5, the connecting element associated with the anchoring member 2 comprises a ligament 23 of a conventional type, with a deformable cross section, and an adaptation element 24 or trumpet in the form of 'a sleeve. The sleeve 24 has a generally cylindrical shape of revolution with a closed circular cross section. It has an internal face 26 flaring at an axial end of the sleeve, and an external face 28 having a longitudinal section of diameter narrowed relative to the axial ends. The smallest diameter of the sleeve 24 is chosen to be slightly greater than the diameter of the ligament 23 so that only one section of ligament can be threaded into the sleeve. The sleeve has dimensions (in particular a thickness) and a material such that its cross section can be easily deformed or even crushed. The middle part of the sleeve 24 threaded onto the ligament 23 is intended to be received between the branches 8 of the head of the pedicle screw 4. The longitudinal ends of the sleeve, of larger external diameter than its middle part, thus form stops at 1 against the sliding of the sleeve 24 out of the screw 4 along the ligament 23.

The clamping screw 16 has a lower face 30 opposite the cavity 20 and of substantially spherical convex shape. This face 30 comes into contact with the sleeve 24 during installation of the clamping screw. When tightening the screw, this face 20 deforms and locally crushes on the ligament 23 the middle part of the sleeve 24. The corresponding section of the ligament 23, also deformed without being damaged, is thus immobilized in the sleeve 24 which is rigidly immobilized on the head of the pedicle screw. The flared end of the internal face 26 of the sleeve facilitates the introduction of the ligament inside the latter. It is thus possible to connect together several pedicle screws 4 by means of the single ligament 23. The sleeve could be split and thus have an open cross section.

With reference to FIGS. 1, 6 and 7, the anchoring member 3 receives a rigid connection element such as a rod 32 intended to connect together several pedicle screws 4 in a manner known per se from the two aforementioned documents. In particular, it may include a split ring with a spherical external face, threaded on the rod 32 and clamped between the clamping screw 16 and the head of the pedicle screw 4 to allow the inclination of the rod 32 relative to the pedicle screw 4, then their relative immobilization.

In this case, the cap 12 of the anchoring member 3 comprises a lug 34 or ear projecting from an external face of the cap. This tab 34 has a through orifice 35 arranged so that once the cap 12 in place, the orifice 35 extends to the right or at the level of the rod 32 along the pedicle screw. In addition, the cap 12 has a cylindrical cheek 36 of circular section extending downward over the entire height of the tab 34 the cylindrical side face of the cap. This cheek 36 has, opposite the tab 34, a straight vertical edge 38 parallel to an axis of the cap. This cheek extends around the axis of the cap over an angular sector of approximately 120 °. The cheek 36 is contiguous to the tab 34 by its other vertical edge. The orifice 35 has a flared end 40 on the side opposite to the cheek 38. The section, substantially rectangular, of the orifice 35 is just greater than that of the ligament 23 and can receive only a single section thereof. A free longitudinal end 42 of the ligament has a knot, shown in simplified form in the figures, which when the ligament 23 passes through the orifice 35, comes to bear against the flared edge 40 thereof to block the ligament.

The ligament being connected to other anchoring members of which only one, 2, has been illustrated, there is a traction on the ligament 23, which places the edge 38 of the cheek in abutment against the rod 32 (if necessary in having previously rotated the cap 12 around its axis), thus preventing rotation of the cap 12 relative to the pedicle screw 4 and to the rod 32. The rod 32 is rigidly connected to other pedicle screws 4 of a type classic, connected together only by the rod.

The osteosynthesis system thus comprises a rigid part, constituted by the screws 3 rigidly connected to each other by the rod 32, and a flexible part constituted by the screws 2 connected to each other by the ligament. The screw 3 which is illustrated constitutes the border between the two parts of the system. In terms of mechanical behavior, a stress transition is thus made between the rigid part of the column and its completely free part.

The connecting element with deformable section may include a cable.

Claims

1. Vertebral osteosynthesis system, comprising at least one anchoring member (2) to a vertebra, a connecting element (23) of the member (2) to another anchoring member (3), and a screw (16) able to cooperate with the anchoring member (2) to tighten the connecting element (23) on the anchoring member, the connecting element (23) being of deformable cross section, the system comprising a deformable sleeve (24) capable of receiving the connecting element (23), characterized in that the sleeve receiving the connecting element is capable of being tightened by the screw (16) on the anchoring member ( 2).

2. System according to claim 1, characterized in that the connecting element (23) is flexible.

3. System according to claim 1 or 2, characterized in that the connecting element (23) comprises a ligament or a cable.

4. System according to any one of claims 1 to 3, characterized in that the anchoring member (2) comprises two branches (8) adapted to receive between them the connecting element and having a net (14) to cooperate with the screw (16).

5. System according to any one of claims 1 to 4, characterized in that the sleeve

(24) has a closed cross section.

6. System according to any one of claims 1 to 5, characterized in that the sleeve (24) is adapted to receive at most a longitudinal section of the connecting element (23).

7. System according to any one of claims 1 to 6, characterized in that the sleeve

(24) has an internal face (26) having at least one flared end.

8. System according to any one of claims 1 to 7, characterized in that the sleeve 10

(24) has an outer face (28) having a median section of narrowed section.

9. System according to any one of claims 1 to 8, characterized in that the screw (16) has a lower face (30) intended to extend on the side of the connecting element (23) and of substantially shape spherical.

FIG.5 2/3