WO2011055396A1

WO2011055396A1 - Modular element for dynamic spinal vertebra stabilization systems

Info

Publication number: WO2011055396A1
Application number: PCT/IT2009/000500
Authority: WO
Inventors: Paolo Guerra; Giuseppe Sala; Franco Ronchi
Original assignee: Sintea Plustek S.R.L.
Priority date: 2009-11-09
Filing date: 2009-11-09
Publication date: 2011-05-12

Abstract

The invention relates to a modular element (1) for systems (10) of dynamic stabilization of vertebra of the spinal column, of the type comprising at least one flexible body having opposite ends (6, 7) which can be connected to respective joining elements (15, 18) to form a rod-shaped structure to be associated with at least two spinal vertebra to be stabilized. This modular element has a tubular sleeve body (2) and comprises in at least one of its central sections (9) a plurality of through notches (12) formed on at least one attitude plane transverse to the axis (X-X) of the sleeve (2). Advantageously, with such a modular element, it is possible to obtain a system (10) of dynamic stabilization of spinal vertebra with a rod-shaped structure obtained from the combination of at least one modular element (1) and of two joining elements (15) each having: a stem (11), a shaped end (19) for quick fit with the corresponding end of said modular element (1) and an annular edge (22) between stem (11) and end (19).

Description

Title: Modular element for dynamic spinal vertebra stabilization systems

DESCRIPTION

Field of application

The present invention relates, in its more general aspect, to a modular system for the dynamic stabilization of spinal vertebra.

The invention likewise relates to a modular element for the production of the abovementioned system.

The invention is intended in particular for the field of orthopaedic surgery and neurosurgery wherein there is the need for providing dynamic support for two or more vertebra of the spinal column following injury, lesions or malformations or in all those cases wherein there is a discontinuity in the biomechanical behaviour of the spinal column. The following description is given with specific reference to this field of application with the purpose of simplifying disclosure thereof. Prior art

It is known that, following disease or injury or due to ageing, it may be necessary to act surgically on some vertebra of the spinal column to give them so-called "stabilization", that is to say connect them by means of a subcutaneous device to each of the spinal vertebra involved in the stabilization.

In the current state of the art the use is known of devices for stabilization of the vertebra of the spinal column which enable connection one to the other of two or more spinal vertebra and the providing for them of a dynamic support so as to control better the transfer of load onto them and also protect the bones adjacent thereto.

A spinal stabilization device is for example known and described in the patent application USA n° 2007/0093814 and wherein a support rod is provided, connected to some spinal vertebra by means of conventional anchorage means with screw attachment, for example of the pedicle screw type. This rod has an elongated cylindrical shape and is made in titanium nickel alloy, in steel or in titanium. In one of the multiple embodiments (Figure 20) peripheral grooves are provided, extending longitudinally, which substantially increase the slimness of the rod to allow it to respond better to flexural stresses.

In a further embodiment (Figure 21) peripheral and alternating notches are instead provided on diametrically opposite sides in relation to the rod axis. The depth of the notches is smaller than the radius of the circular section of the rod. In this case too the solution was provided to improve the flexural response of this type of support rod.

Both embodiments described previously do not however allow axial compression of the rod.

Another known technical solution is instead described in the patent application no. US 2005/0261686 which again relates to a support rod for stabilization of spinal vertebra which allows a light angular flexion of the portion of spinal column being treated. Again this solution does not allow axial compression of the rod.

A different known technical solution, described for example in the patent applications no. 2007/0203446 and no. US 2007/0088359, bases on the assumption that the rod can be configured by connecting one to the other flexible modular elements formed in one piece with or connected to semirigid joining elements, the latter intended for connection with the vertebra of the spinal column.

The flexible modular elements are obtained by means of a cylindrical body wherein a helical continuous notch is formed peripherally, while the joining elements are smooth bars inserted in corresponding end housings of the flexible modular elements and connected thereto by means of pins or attachment screws inserted radially at the ends of the flexible modular elements to block in position the joining elements. Albeit advantageous in various respects, and substantially meeting the purpose, this solution has some disadvantages, the first of which is due to the fact that the system obtained with the composition of the abovementioned modular elements is flexible but axially incompressible. The flexibility provided by the helical notch is even so high for the type of application that only a few expensive semi-rigid materials are suitable for being used to make these modular elements.

Another disadvantage is due to the fact that the connection between the modular elements and the bars of the joining elements is relatively complicated and poorly suited to the methods of use in surgery for which these systems are intended.

Finally these known solutions facilitate the penetration of subcutaneous tissue during the phases of implanting of the stabilization systems. There is therefore the need for devising a modular system for the dynamic stabilization of spinal vertebra which has such structural and functional features as to allow an improvement in the performances of the systems currently made available by the prior art and, more particularly, which offers combined features of flexural yielding and also of axial yielding. Summary of the invention

The proposed solution at the basis of the present invention is that of using as flexible modular element a tubular sleeve body wherein a plurality of slots or through notches are formed transverse to the axis of the sleeve.

On the basis of this proposed solution the technical problem is solved by a modular element for systems for dynamic stabilization of vertebra of the spinal column, of the type comprising at least one flexible body having opposite ends which can be connected to respective joining elements to form rod-shaped structure to be associated with at least two spinal vertebra to be stabilized, characterised in that said body is of the tubular sleeve type comprising in at least one of its central sections a plurality of through notches formed on at least one transverse attitude plane to provide axial and flexural yielding for said body.

Advantageously the tubular sleeve body is made with an organic polymer, for example polyaryletherketone or PAEK. The opposite ends of the tubular sleeve body are shaped internally to hold by a quick fit a corresponding end of one of said joining elements. Advantageously, moreover, the notches are angularly distanced one from the other in a regular fashion and the notches of the same attitude plane are angularly staggered in relation to the notches formed in an attitude plane axially adjacent to the previous one. Moreover the modular element 1 can be filled internally with a synthetic material, soft or spongy and biocompatible, which occupies all the free space in the central hole of the sleeve and in the notches.

The modular element 1 can be covered by a sheath or by a membrane in synthetic material, again to avoid permeation in the notches of connective tissue.

With the modular element previously described a system is obtained for the dynamic stabilization of spinal vertebra having a rod- shaped structure obtained from the combination of a modular element of the abovementioned type and of two opposite joining elements each having a stem, a shaped end in order to be connected with quick fit to a corresponding end of the modular element and an annular edge between stem and end.

Further features and advantages of the modular element and of the system according to the present invention will be made clearer by the following description of a preferred embodiment given by way of a non- limiting and indicative example with reference to the accompanying drawings.

Brief description of the drawings

Figure 1 shows a perspective and schematic view of a modular element for producing, according to the invention, dynamic spinal vertebra stabilization systems;

Figure 2 is a front view of the element of Figure 1;

Figure 3 is a view from above of the element of Figure 1 ;

Figure 4 is a perspective and schematic view of a joining element connected to the modular element of Figure 1 to form a system of dynamic stabilization of spinal vertebra according to the present invention; Figure 5 is a perspective and schematic view of another joining element which can be connected to the modular element of Figure 1 to form a system of dynamic stabilization of spinal vertebra according to the present invention; Figure 6 is a perspective and schematic view of a system of dynamic stabilization of spinal vertebra made in accordance with the present invention with the combination of a modular element of Figure 1 and of two joining elements of Figure 4;

Figure 7 is a perspective and schematic view of another system of dynamic stabilization of spinal vertebra made in accordance with the present invention with the combination of two modular elements of Figure 1, of two joining elements of Figure 4 and of a joining element of Figure 5;

Figure 8 shows a perspective and schematic view of a system of dynamic stabilization according to the invention applied to a pair of spinal vertebra. Detailed description

Referring to these drawings, 1 denotes overall a modular element realised in accordance with the present invention for systems 10 of dynamic stabilization of vertebra of the spinal column.

The modular element 1 is intended to be connected to other elements of the same structure by means of joining elements 15 and 18 which are to be described in greater detail herein below.

The modular element 1 essentially comprises a tubular sleeve body 2 with circular section and axis X-X, having diameter "d" of about 1 1 mm.

Other sections can be adopted without thereby entailing any limitation on the rights of the Applicant, for example also a square or hexagonal section with rounded corners could be congruent to the purpose of the present invention. In these alternative embodiments the diameter d can be identified as the maximum overall dimension transverse to the axis X-X of the modular element 1. Other diameters can also be adopted if necessary, preferably for example in the range of values comprised between 9 mm and 12 mm. The sleeve 2 has an axial extension "h" which varies according to the applications.

More particularly, although the sleeve 2 can be made in a plurality of diverse sizes d and h, at least three different tubular sleeves 2 are provided to facilitate the work of the surgeon.

The tubular sleeve 2 has perimeter wall 4 of predetermined thickness "s".

The thickness s of the perimeter wall 4 can have or otherwise a ratio of proportionality with the diameter or transverse overall dimension d.

Advantageously, according to the invention, the tubular sleeve 2, in its various axial extensions, is made with an organic polymeric material or in any case with a biocompatible material.

Preferably the organic polymer can be for example of the type commercially known as polyaryletherketone or PAEK.

This material can be extruded for example with a densit of 1.9 g/cm³, or in any case with a density compatible with the type of application, and has excellent resistance to high temperatures, to attacks by chemical products and to impact.

This material is moreover thermoplastic and biocompatible.

Alternatively the modular element 1 can be made in biocompatible metal material.

The sleeve 2 has opposite ends 6 and 7 intended to be connected to other elements of the system 10, more particularly to the joining elements 15 and/ or 18 to form a composite system 10 and to be associated with at least two spinal vertebra to be stabilized, as shown in Figures 6 and 7. Figure 8 shows an example of application of a system 10 of the present invention to a pair of spinal vertebra.

Advantageously, for this purpose, the ends 6 and 7 of the sleeve 2 have a respective lowered circular housing 16, 17 constituting an inlet for an initial section 21 of the sleeve 2 shaped internally for coupling with one of the joining elements 15 or 18. The initial section 21 can be shaped with teeth or ridges to encourage joining with quick fit to a corresponding end of the joining elements 15 or 18.

In a preferred embodiment, the initial section 21 involves nut threading for a threaded coupling with a corresponding threaded end of the joining elements 15 or 18.

To complete the description it should be noted that at the two ends 6, 7, yet laterally to them, there are two diametrically opposite indentations 13, 14 for the insertion of a manoeuvre key.

The joining elements 15 comprise a stem 1 1, having comparable length to that of the tubular sleeve 2, and a shaped end 19 for quick fit form coupling with one of the ends 6, 7 of the tubular sleeve 2.

The drawings only show an example wherein the end 19 is provided perimetrally with threading for a threaded coupling with the initial section 21 of the sleeve 2. The other embodiments with shaping for quick fit are not shown in the drawings without thereby constituting a limitation for the rights of the Applicant.

Between the stem 1 1 and the end 19 there is an annular edge 22 which defines the shaped or threaded portion of the end 19.

The free end of the element 15 opposite the end 19 is provided with an embedded housing 23 with hexagonal section for the insertion of an Allen key for manoeuvre shown in the drawings.-

In the embodiment with threaded coupling, the structure of the joining element 15 is substantially that of a screw with plain shank 1 1 and threaded head 19, with an annular edge 22 between shank 1 1 and head 19.

The joining element 15 can be made with the same organic polymeric material with which the modular element 1 is made.

Alternatively the joining element 15 can be made with a biocompatible and non-osteoconductive metal alloy or a metal, for example titanium. The joining element 15 is in any case rigid. In one of the embodiments described previously the end 19 of the joining element 15 is intended to couple in threaded engagement with the initial section 21 at the end 6 or 7 of the tubular sleeve 2 up to the point wherein the annular edge 22 is held completely in the lowered housing 16 or 17 of the corresponding end 6 or 7.

This would also occur should the coupling between the end 19 and the corresponding initial section 21 of the sleeve 2 be a quick fit form coupling.

The structure of the joining element 18 is substantially similar to that of the joining element 15 with the difference that there is a stem 25 defined by two opposite annular edges 31, 32 which separate the stem 25 from respective shaped or perimetrally threaded ends 28, 29.

Embedded housings 26 with hexagonal section are also provided in the joining element 18, in both the ends 28 and 29, for the use of an Allen key which can facilitate tightening in the form or threaded coupling between a joining element 18 and a modular element 1.

This particular joining element 18 is used to connect one to the other two modular elements 1 , as clearly shown in Figure 7.

This joining element 18 is also made with the same material used to make the joining element 15.

Figure 6 shows an example of a system 10 of dynamic stabilization of spinal vertebra made in accordance with the present invention with rod- shaped structure obtained from the combination of a modular element 1 and of two joining elements 15. Figure 7 shows an example of a system 10 of dynamic stabilization of spinal vertebra made in accordance with the present invention and with a rod-shaped structure wherein at least two modular elements 1 with tubular sleeve 2 are connected and joined one to the other by a joining element 18, inserted between two sleeves 2, and have at the ends of the system two joining elements 15. Obviously, according to the number of spinal vertebra to be treated, it is possible to assemble multiple modular elements interconnected by unions 18 and with end unions 15. Advantageously, again in accordance with the present invention, the tubular sleeve 2 is involved, in at least one of its central sections 9, by a plurality of through notches 12 or cuts formed on at least one attitude plane transverse to the axis X-X of the sleeve 2. The notches 12 are substantially slots which traverse completely the perimeter wall 4 of the tubular sleeve 2.

The notches 12 are formed on attitude planes transverse to the axis X-X and, preferably, are orthogonal to the axis.

Moreover, again in a preferred embodiment, the notches 12 are formed on multiple attitude planes parallel one to the other in a predetermined distanced relation. It should also be noted that in the plurality of attitude planes of the notches 12 there may also be some that are not parallel one to the other. Herein below more specific reference will be made to the attitude planes parallel one to the other only so as to simplify the disclosure of the invention.

The notches are preferably distanced axially by a few millimetres, that is to say that there is a distance of a few millimetres between one attitude plane and that immediately adjacent in an axial direction, for example these attitude planes are distant in a range from 1 to 4 millimetres. Advantageously the notches 12 can be angularly distanced one from the other in a regular fashion. Moreover these notches 12 can extend angularly on the same attitude plane by circumference arcs regular one in relation to the other.

The notches 12 on the same plane can be in an equal or odd number but in any case extend for a predetermined angular section slightly less than 360° /number of notches, in such a way that there is at least one section 27 of perimeter wall 4 of the sleeve 2 which maintains the continuity of the wall 4 between one notch 12 and that immediately and radially adjacent. The notches 12 of the same plane are preferably angularly staggered in relation to the notches formed in an attitude plane of the notches parallel to the previous one and axially adjacent. This particular feature effectively confers the required axial yielding to the modular element 1 in that the sections of wall 27 of the perimeter wall 4 of the tubular sleeve 2, which on a given attitude plane angularly separate two adjacent notches, are longitudinally alternated with a lower and upper notch.

In the event therefore of axial compression of the modular element 1 it is as if the support of each of said sections 27 was yielding in that below or above each of these sections 27 there is always a notch 12.

In fact all the notches 12 on the central section 9 of the sleeve 2 confer on the latter an essentially perforated configuration with notches 12 formed on attitude planes of odd position aligned one with the other in a longitudinal direction yet staggered in relation to the notches formed on attitude planes of even position.

In other words, notches 12 formed on attitude planes alternating one with the other correspond in number and arrangement.

Moreover, the section 27 of perimeter wall 4 which separates a notch 12 from a notch 12 angularly adjacent on the same attitude plane is situated substantially at the centre of the circumference arc subtended by a notch 12 formed on an attitude plane immediately above and below. It should be noted that the modular element 1 can be internally filled with a synthetic material, soft or spongy and biocompatible, which occupies all the free space in the central hole of the sleeve 2 and in the notches 12. This avoids the possible penetration or proliferation of connective or subcutaneous tissue in the curves of the system 10 during the entire period of implanting.

The particular configuration of the sleeve element 2 confers dual axial and flexural yielding to the modular element 1 of the present invention.

The modular element 1 thus has axial yielding. At the same time the configuration of the modular element 1 allows a predetermined elasticity to be guaranteed in relation to flexural stresses.

The configuration of the end of the modular element 1 and of the joining elements 15 and 18 confers extreme ease in the composition of the systems of stabilization 10.

This enables easy assembly of the systems of dynamic stabilization 10 which, are able to compensate also phenomena of axial compression which occur in the phase of stabilization of the spinal vertebra.

The use of the organic polymeric material in the structure of the modular element 1 gives it special usefulness for the field of application for which it is intended, this material being totally biocompatible and non- osteoconductive.

Finally the uncommon structural simplicity of the modular element and of the system according to the invention should be noted, something which guarantees its possible production on a large scale, with relatively low costs as well as durability and reliability in time.

Claims

1. Modular element (1) for systems (10) of dynamic stabilization of vertebra of the spinal column, of the type comprising at least one flexible bod having opposite ends (6, 7) which can be connected to respective joining elements (15, 18) to form a rod-shaped structure to be associated with at least two spinal vertebra to be stabilized, characterised in that said body is a tubular sleeve (2) comprising in at least one of its central sections (9) a plurality of through notches (12) formed on at least one attitude plane transverse to the axis (X-X) of the sleeve (2) to confer axial and flexural yielding to said body.

2. Modular element according to claim 1, characterised in that said tubular sleeve (2) is made with an organic polymeric material, for example polyaryletherketone or PAEK.

3. Modular element according to claim 1 , characterised in that said opposite ends (6, 7) are shaped internally to hold and restrain with quick fit a corresponding end (19) of one of said joining elements (15, 18).

4. Modular element according to claim 1 , characterised in that said notches (12) are angularly distanced one in relation to the other in a regular fashion on the same attitude plane.

5. Modular element according to claim 1 , characterised in that the notches (12) of the same attitude plane are angularly staggered in relation to the notches (12) formed in an attitude plane axially adjacent to the previous one.

6. Modular element according to claim 1 , characterised in that said central section (9) has an essentially perforated configuration with notches formed (12) on attitude planes alternating one with the other which correspond in number and arrangement.

7. Modular element according to claim 1 , characterised in that the internal space of the tubular sleeve (2) is filled with a soft and elastic material which permeates through the notches (12).

8. Modular element according to claim 1 , characterised in that said central section (9) comprises a plurality of attitude planes of the notches (12) parallel one to the other.

9. Modular element according to claim 1, characterised in that said modular element (1) can be covered by a sheath or by a membrane in synthetic material.

10. System (10) for the dynamic stabilization of vertebra of the spinal column characterised in that it comprises in a rod-shaped structure at least one modular element (1) according to any one of claims 1 to 8 and at least one pair of opposite joining elements (15) comprising a stem (1 1), a shaped end (19) for quick fit connection with a corresponding end (6, 7) of the modular element (1) and an annular edge (22) between stem (1 1) and end (19).

1 1. System according to claim 10, characterised in that it further comprises at least one second modular element (1) and a further joining element (18) comprising a stem (25) and two opposite shaped ends (28, 29) with respective annular edges bordering off the stem (25) from the ends (28, 29), said further joining element (18) being inserted between two modular elements (1).

12. System according to claim 10, characterised in that said tubular sleeve (2) is made with an organic polymeric material, for example polyaryletherketone or PAEK.

13. System according to claim 10, characterised in that said joining element (15) is made with a biocompatible metal alloy or metal material.

14. System according to claim 10, characterised in that said modular element (1) has at the opposite ends (6, 9) a lowered annular housing for holding the annular edge (22) of said joining element (15).

15. System according to claim 10, characterised in that said end (19) of the joining element (15, 18) has a form coupling or a threaded coupling with a corresponding end (6, 7) of the modular element (1).