WO1999053855A1

WO1999053855A1 - Backbone osteosynthesis with frame and wires

Info

Publication number: WO1999053855A1
Application number: PCT/FR1999/000887
Authority: WO
Inventors: Eric Lasseur
Original assignee: Dimso (Distribution Medicale Du Sud-Ouest)
Priority date: 1998-04-16
Filing date: 1999-04-15
Publication date: 1999-10-28
Also published as: AU3334799A; FR2777448B1; FR2777448A1

Abstract

The invention concerns a backbone osteosynthesis system comprising at least one rod (20), wires (6) to bind the rod to several vertebrae (14) and locking elements (4) each capable of binding one of the wires (6) to the rod (40). At least one of the locking elements (4) has at least one orifice (62) for receiving wire (6).

Description

"RACHIDIAN DOSTEOSYNTHESIS DEVICE WITH FRAME AND WIRES". The invention relates to systems ^one spinal osteosynthesis comprising at least one element such as a rod or a frame, and son to attach this element to the vertebrae.

The metal frame is used in spinal osteosynthesis in various indications (trauma, spinal degenerative pathology, idiopathic or secondary scoliosis, metastases and vertebral tumors). Its simplicity and quick installation make it a material of choice for fragile patients

(extensive vertebral metastases). Its small size allows an easier realization of the associated posterolateral bone graft. Its relative flexibility, first of all taken for a disadvantage compared to very rigid pedicle arrangements, would in fact allow less stress on non-instrumented transition levels. However, two important points limit the use of this material: its potential neuroaggressiveness and its ferromagnetism.

Indeed, some authors have pointed out the potential aggressiveness of sub-lamar threads, the neurological risk being four times higher than for pedicle instrumentation associated with hooks according to the American Research Scoliosis Society in 1987.

Currently, semi-rigid single-strand wires (folded in double) are used. These wires are curved manually before their passage under the blade of the vertebra, then after their passage recovered by a clamp on the other side of the blade. They must then be maintained in traction on each stage at their caudal end on the field by forceps and at their cranial end by a fold on the front blade positioning of the frame. This shaping of the wires requires additional operating time and a well-trained instrumentalist, subject to having to prepare them yourself. It is true that as simple as it is, the technique of installation can become complex for long assemblies because of the number of threads passed (three vertebral levels above and underlying compared to the traumatic or tumor lesion with two threads per level). Maintaining the traction of each wire becomes more problematic with the increase in the number of wires passed. In addition, the recognition of the right and left side of each wire on the same floor when setting up the frame can be hampered by bleeding (metastasis). It also happens from time to time to cross the wires in sub-lamina, which poses besides especially a problem in the event of ablation of the material with a risk of lesion of the intraductal elements. The setting up of the frame in the middle of a forest of semi-rigid wires often leads to the support of some of these in the canal before tightening and a potential neurological risk. The tightening of the wire is itself more or less random according to the habit of the operator and requires a screwing movement while maintaining a strong clamp and a vertical pull, which is impractical.

In addition, current ferromagnetic equipment does not allow postoperative magnetic resonance imaging (MRI), essential for monitoring spinal pathology, in particular that of metastases.

Furthermore, a known technique for connecting the wires to the frame is to tie them onto the frame or to simply pass them around it. The use of this technique can be long and awkward during an intervention. An object of one invention is to provide an osteosynthesis system making it possible to accelerate and simplify the positioning of the system on the patient during an intervention. In order to achieve this goal, there is provided according to the invention a spinal osteosynthesis system comprising at least one rod, wires for attaching the rod to several vertebrae and blockers each capable of connecting one of the wires to the rod, in which at least one of the ^' blockers has at least one orifice for receiving the wire.

Thus, although blockers are additional elements in the system, they make it possible to speed up the installation of the system. For example, the blocker can be adapted to retain the wires automatically by pinching, or adapted to be deformed by clamping to crimp the blocker on the wires.

Advantageously, the wires are intended to be fixed directly to the vertebrae. Advantageously, each wire has dimensions making it suitable for passing under a blade of the vertebra.

Advantageously, at least one of the blockers is able to retain at least one free end of the wire.

Advantageously, the orifice is a conduit, in particular of conical shape with a narrowest section of the conduit intended to be located opposite the vertebra.

Thus, the conduit offers over its entire length a large contact surface with the wire for blocking the latter after crimping. When the orifice has a conical shape, its dimensions allow the wire to pass in one direction for its entry, but help to retain it in the opposite direction to one against its exit: it is thus possible to tighten or pre - immediate manual tightening when each wire is placed in the associated blocker. Advantageously, each blocker comprises a base capable of being directly connected to the rod, and a body capable of being directly connected to the wire, the body being capable of being movable in rotation relative to the base. Thus, the traction exerted on the wires orients the body relative to the base during installation. Consequently, the blocker adapts best to the position of arrival of the wires.

Advantageously, the body and the base have conical faces adapted to come to bear on one another.

When these faces are configured in a MORSE type cone, known per se, a relative immobilization of the faces will be obtained when they are brought into mutual contact or when pressure is exerted to accentuate this contact.

Advantageously, the blocker is adapted to be deformed, preferably crushed, by clamping, manually by means of a tool. Thus, the wires are immobilized on the blocker in a particularly simple, rapid and effective manner.

Advantageously, the blocker has an imprint for receiving the rod for setting the blocker relative to the tj-'ge. This facilitates the installation of the blocker and improves its stability and that of the wires on the frame.

Advantageously, the blocker and the rod are made of titanium.

Thus, the system is made compatible with magnetic resonance imaging (MRI).

Advantageously, the rod has on the one hand end sections and on the other hand a median section having a cross section of larger area than the area of the cross section of the end sections. Thus, the stresses of the vertebral transition levels situated above and below the instrumented levels are reduced.

Advantageously, the area of the cross section of the rod decreases regularly from the middle section to the end sections.

Advantageously, the system comprises two rods belonging to the same frame.

A wire is also provided according to the invention for a spinal osteosynthesis system, in particular according to the invention, in which, on at least one median section of the wire, the wire has a width greater than a thickness of the wire.

Thus, the median section is adapted to come into contact over its entire width with an internal element of the human body such as a vertebra blade and the pressure exerted on it is reduced. By distributing the exerted effort over a larger area, the "cheese-wire" or "butter-cutting wire" effect is avoided on the blade.

Advantageously, the width of the middle section is greater than a width of an end section of the wire.

Advantageously, the thickness of the middle section is less than a thickness of an end section of the wire.

Thus, the size of the middle section is reduced in the human body, for example in the canal of the vertebra. Advantageously, the width and the thickness of the wire are constant over its entire length.

Thus, the wire has the form of a strip, and its manufacture is simple and inexpensive.

Advantageously, the wire has two end sections of different colors from one another. Thus, during use for one spinal osteosynthesis, a distinction is made between the end associated with the cranial aspect and that associated with the caudal aspect, which facilitates the subsequent identification of each end of the wire when the frame or the stem. There is also provided according to the invention a tool for the insertion of a wire under a blade of a vertebra and for example for a system according to the invention, the tool comprising a handle and an insertion part having a shape general flat curved to form a cylinder sector and allowing the wire to pass under the internal element, the tool having an elongated housing for the reception of the wire, in which the housing extends into the handle. This facilitates the introduction of the wire into the tool and the subsequent handling of the wire, during the intervention.

Advantageously, the housing extends along the length of the insertion part. Thus, this tool helps to introduce the wire, for example in sub-lamina, while passing from the caudal window to the cranial window. Its shape follows the central part of the rear face of the blade and allows the sliding wire ^' r to pass into the cranial window. Advantageously, the housing opens at a free end of the insertion part.

Advantageously, the housing comprises a gutter.

Advantageously, the housing includes a tunnel. Thus, the thickness of the insertion part can be reduced to a minimum, which promotes its atraumatic character.

Advantageously, the housing extends to a free end of the handle. Advantageously, the housing has, over at least part of its length, a flattened cross section. Thus, the shape of the housing is adapted to a flat wire in the form of a strip or having a flattened median section.

Advantageously, the insertion part has a coating of polytetrafluoroethylene (PTFE) on at least one of its faces.

This facilitates the introduction of the tool into the channel against the dura, reducing friction and therefore trauma. In addition, according to the invention, an osteosynthesis system according to the invention is provided, comprising a wire according to the invention and / or a tool according to the invention.

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 rear elevation view of a system according to the invention installed on the vertebrae of a spine; - Figure 2 is a sectional view of the system of Figure 1 along a plane transverse to the length of the frame and the spine;

- Figure 3 is a detail view of the system of Figure 1 showing the passage of a wire in a channel of a vertebra;

- Figure 4 is an elevational view of a rod of the frame of Figure 1;

- Figures 5 and 6 are two front and side views respectively of one of the wires of Figure 1; - Figure 7 is a partial perspective view illustrating an alternative embodiment of the wire;

- Figures 8 and 9 are two perspective views of a tool for installing the system of Figure 1;

- Figure 10 shows an alternative embodiment of the tool of Figures 8 and 9, in use; - Figure 11 is a partial perspective view of the frame and one of the blockers of Figure 1; Figure 12 is a partial sectional view of the blocker of Figure 11, along the axis of one of its conduits; and Figures 13 and 14 show two variants respectively of the conduit and the general shape of the blocker.

With reference to FIGS. 1 to 3, the system for osteosynthesis of the spine comprises a frame 2, pairs of blockers 4 and pairs of wires 6. We will first describe the wires 6 and their placement.

With reference to FIGS. 5 and 6, each wire 6 is single-stranded, flexible, of elongated shape and here made of titanium. It has a middle section 8 and two free end sections 10, on either side of the latter.

The median section 8, of rectangular cross section with rounded edges, has a constant width L and a constant thickness e _. less than L and a constant thickness E of the end sections

10. The width L is greater than the constant width 1 _. end sections 10, for example two to four times greater than this. On the end sections

10, the width / 1 is equal to the thickness E. The length d of the median section 8 is approximately equal to the width of the blade 12 of the destination vertebra and therefore variable as a function of the vertebra.

In an alternative embodiment shown in Figure 7, the wire 6 is shaped into a strip of constant cross section of rectangular shape. Over its entire length, the wire 6 has a constant width L much greater than its thickness e_, which is also constant.

The establishment of each wire 6 includes the step of passing it under a blade 12 of the vertebra 14 for which it is intended. For this, it is advantageous to use the tool 16 illustrated in the figures 8 and 9. This tool or ancillary comprises a handle 18 with knurled cylindrical external face. An intermediate part 20 with rectangular cross section and rounded edges extends this handle 18 along the axis of the cylinder. Opposite the handle 18, the intermediate part 20 carries an insertion part 22 of curved flat shape to give it a generally cylindrical shape. This part 22 is curved in the direction of the handle 18, the axis 24 of the cylinder being on the side of this part 22 located towards the handle 18. The insertion part 22 has rounded edges and two external cylindrical faces 28 and internal 26 covered with polytetrafluoroethylene (PTFE) or an equivalent material facilitating the sliding of its faces against another element and in particular against the dura mater.

The handle 18 and the intermediate part 20 are crossed along their longitudinal axis by a. elongated tunnel 30 with an elongated cross section, this section having a greater width at its center. This tunnel 30 opens at the free end 30 of the handle 18, and moreover at the end of the insertion part 22 contiguous to the intermediate part 20. It extends into the internal cylindrical face 26 of the part of insertion 22 in the form of a gutter 34 extending to the free end of the insertion part. The gutter 34 extends along the length of the insertion part 22, in a plane perpendicular to the axis 24 of the cylinder. In an alternative embodiment shown in FIG. 10, the insertion part 22 is thicker than in FIGS. 8 and 9 and the tunnel 30 extends into the insertion part 22 with the same cross section as in the rest of the tool.

The tunnel 30, with the gutter 34, forms a housing for the reception of the wire 6. The wire being thus received in the tool over the entire length of the tunnel, 10

introduces the insertion part 22 under the blade 12, between the latter and the dura mater as illustrated in FIG. 10. When the insertion part 22 appears on the other side of the blade, the wire 6 is grasped at the free end of the insertion part 22 to retain it and the tool 16 is removed by making it follow back the reverse path from its insertion path. This allows the establishment of the wire 6 without contact with the dura. After removing the tool, the middle section 8 of the wire 6 is positioned with its width L pressing against the blade 12, by gripping the two free end sections 10 of the wire. The two free end sections 10 of the wire have different colors from one another, which makes it possible to distinguish the end sections according to whether they come out of the cranial window or the caudal window as soon as we always associate the same color μ either window. The same is done to install each of the wires 6. With reference to FIGS. 1 to 4, the frame 2 is then placed along the spine in the patient's body. This frame is rigid and comprises two tubular rods 40 generally parallel to each other, connected at their ends by two connecting elements 42. The frame has a rectangular shape. Each rod 40 has a cross section of regularly decreasing area from a median section 44 of the rod to its ends. The area of the cross section is therefore maximum in the middle of the rod 40. The instrumented part of the spine will be opposite this section with maximum area. The cross section of the rods is circular. Prior to the installation of the frame, the rods 40 can be curved so that they best match the curvature of the part of the column receiving the osteosynthesis system. 11

Referring to Figures 1, 11 and 12, each blocker 4 comprises a base 50 here in the form of a skirt with external faces 52 and internal frustoconical 54. A lower circular edge of the skirt corresponding to its narrowest section has two notches 56 in diametrically opposite semicircle on either side of the axis of the skirt, defining an imprint for receiving the rod 40, for the wedging of the blocker 4 on the rod. The blocker comprises a solid internal body 58 with a frustoconical external face 60 shaped to make surface contact with the internal face 54 of the skirt when it is received therein. These will, for example, be cones of the MORSE type, known per se for hip prostheses. A clamping of two frustoconical faces of this type one against the other along the axis of the skirt ensures their relative immobilization. Before tightening, the body 58 is movable in rotation relative to the skirt 50 around the axis of the skirt. The body has two conduits 62 with axis 64 parallel to the axis of the skirt, passing right through the body and emerging at its upper and lower faces. The two conduits 62 are diametrically opposite one another on either side of the axis of the skirt. The conduits 62 have a frustoconical shape, inverted relative to that of the skirt. The diameter of the upper section, the narrower of the duct and intended to be the longest away from the vertebra 14, is chosen to allow the free passage of an end section of the wire 6 from the lower face to the face upper body 8, but to limit or even prohibit the withdrawal of the wire in the other direction. Thus, when the wires 6 are placed in the blockers 4, it is possible to immediately pre-tighten or tighten the wires.

In the variants of FIGS. 13 and 14, the duct 62 is cylindrical and the external face 52 of the skirt is cylindrical, respectively. 12

To set up the system, the wires 6 are introduced under the blades 12, as mentioned above. There are thus two wires 6 per vertebra, on either side of the axis of the spine. The frame 2 is then installed with the rods 40 parallel to the longitudinal direction of the spine, and symmetrical to each other on either side of its axis. For each wire 6, the blocker 4 is installed bearing on the rod 40, by wedging the blocker by means of the notches 56, the blocker extending on the side of the rod furthest from the vertebra. The two ends of the wire 6 are introduced into the body 58, into the respective conduits 62 through the lower face of the body 58, in order to make them emerge from the upper face of the blocker. Then we pull them to put them in tension. The body 58 then rotates relative to the skirt 50 as a function of the positioning of the wires 6. The skirt 50 is then tightened on the body 58 to immobilize it relative to the latter manually by means of a clamping tool. When all the blockers 4 have been thus installed, for each blocker, it is ensured that the wire 6 is indeed in tension and the blocker 4 is crushed manually by means of a tightening tool to crimp the blocker on the two sections of 'end of the' wire 6 and thus immobilize on the frame 2 the blocker 4 and the wire 6. One thus rigidly immobilizes the entire system.

For each of the elements constituted by the wires 6, the blockers 4, the frame 2 and the tool 16, it is possible to use at least one of its characteristics independently of those of the other elements. In particular, at least one of the characteristics of the frame 2, of the wires 6 or of the tool 16 can be implemented independently of the existence of the blockers 4.

In the housing 30 of the tool or in a second specific housing of the tool, it is possible to pass an optical fiber connected to an optical system for 13

monitor the insertion of the tool 16 and the wire 6 into the vertebra 14 behind the blade 12.

The rods 40 may have a cross section of constant area over their entire length.

Claims

14 CLAIMS

1. System of ¹ spinal osteosynthesis comprising at least one rod (40), wires (6) for attaching the rod to several vertebrae (14) and blockers (4) each capable of connecting one of the wires (6) to the rod (40), characterized in that at least one of the blockers (4) has at least one orifice (62) for receiving the wire (6).

2. System according to claim 1, characterized in that each wire (6) has dimensions making it suitable for passing under a blade (12) of the vertebra (14).

3. System according to any one of claims 1 or 2, characterized in that at least one of the blockers (4) is capable of retaining at least one free end of the wire (6).

4. System according to any one of claims 1 to 3, characterized in that the orifice (62) is a duct, in particular of conical shape with a narrowest section of the duct intended to be located opposite the vertebra (14).

5. System according to any one of claims 1 to 4, characterized in that each blocker (4) 'comprises a base (50) capable of being directly connected to the rod, and a body (58) capable of being directly connected wire (6), the body (58) being adapted to be movable in rotation relative to the base (50).

6. System according to claim 5, characterized in that the body (58) and the base (50) have conical faces (54, 60) adapted to bear on one another.

7. System according to any one of claims 1 to 6, characterized in that the blocker (4) is adapted to be deformed, preferably crushed, by clamping, manually by means of a tool (16). 15

8. System according to any one of claims 1 to 7, characterized in that the blocker (4) has an imprint (56) for receiving the rod (40) for setting the blocker relative to the rod.

9. System according to any one of claims 1 to 8, characterized in that the blocker (4) and the rod (40) are made of titanium.

10. System according to any one of claims 1 to 9, characterized in that the rod (40) has end sections and a median section (44) having a cross section of larger area than the area of the section transverse end sections.

11. System according to claim 10, characterized in that the area of the cross section of the rod (40) decreases regularly from the middle section (44) to the end sections.

12. System according to any one of claims 1 to 11, characterized in that it comprises two rods (40) belonging to the same frame (4).

13. Wire for a spinal osteosynthesis system in particular according to any one of claims 1 to 12, characterized in that, on at least one median section (8) of the wire (6), the wire has a width (L) greater than a thickness (e) of the wire.

14. Wire according to claim 13, characterized in that the width (L) of the median section (8) is greater than a width (1) of an end section (10) of the wire (6).

15. Wire according to claim 13 or 14, characterized in that the thickness (e) of the middle section (8) is less than a thickness (E) of an end section (10) of the wire (6).

16. Wire according to claim 13, characterized in that the width (L) and the thickness (e) of the wire (6) are constant over its entire length. 16

17. Wire according to any one of claims 13 to 16, characterized in that the wire (6) has two end sections (10) of different colors from one another.

18. Tool (16) for inserting a wire (6) under a blade (12) of a vertebra, for example for a system according to claim 1, the tool comprising a handle (18) and a part insert (22) having a generally flat shape curved to form a cylinder sector and allowing the wire (6) to pass under the internal element (12), the tool having an elongated housing (30) for receiving wire, characterized in that the housing (30) extends into the handle (18).

19. Tool according to claim 18, characterized in that the housing extends along the length of the insertion part.

20. Tool according to claim 18 or 19, characterized in that the housing (30) opens at a free end of the insertion part (22).

21. Tool according to any one of claims 18 to 20, characterized in that the housing (30) comprises a gutter.

22. Tool according to any one of claims 18 to 21, characterized in that the housing (30) comprises a tunnel.

23. Tool according to any one of claims 18 to 22, characterized in that the housing (30) extends to a free end of the handle.

24. Tool according to any one of claims 18 to 23, characterized in that the housing (30) has, over at least part of its length, a flattened cross section.

25. Tool according to any one of claims 18 to 24, characterized in that the insertion part (22) has a coating of polytetrafluoroethylene (PTFE) on at least one of its faces (26, 28). 17

26. System according to any one of claims 1 to 12, characterized in that it comprises a wire according to one of claims 13 to 17 and / or a tool according to one of claims 18 to 25.