FR2724312A1 - Inter-somatic dorsal-lumber spacer - Google Patents

Abstract

The spacer, designed to be inserted between two adjacent vertebrae to re-establish anatomically the correct gap between them, consists of at least one element (2,3) formed from a rigid or slightly resilient vertical wall (4,5) open at the top and bottom to allow it to be filled with bone tissue, and shaped so that it can be inserted between two vertebrae without major mechanical intervention. The upper and lower edges (6,7) of the spacer elements have points (8) or are roughened to ensure that they anchor into the bones of the vertebrae, and their walls are shaped to make the elements broader and deeper at the front than at the back. The spacer elements are made in one piece by machining or moulding e.g. from a titanium alloy with or without a coating, a polymer or other biocompatible radio-transparent material or a polymer with micro-elasticity which promotes bone fusion.

Description

INTERSOMATIOUS SPACER
The present invention relates to an intersomatic spacer intended to be inserted into the disc space defined between two adjacent vertebrae for the purpose of bone fusion and to maintain a constant intervertebral height.

 It is more particularly intended for the reconstruction of the lumbar and dorsal part of the spine when the latter is affected by degenerations which cannot be absorbed by other methods.

 In the past, the restoration of the disc space was achieved without interposition of intervertebral spacers, with random results.

 Subsequently, the need to interpose an integrated spacing device arose. Such compression devices have been produced in various forms (parallelepipedic, cylindrical with external threads, etc.). They are often affected by the disadvantages inherent in their forms such as difficulties in positioning and preparation of the insertion site, the need to add posterior osteosynthesis material to facilitate bone fusion - hence artifacts on the scanner or The MRI.

 In addition, these implants tend to move and sink into the vertebra and the volumes of bone stored are low.

 Patents EP307241, WO8912431, US4732256 relate to exemplary embodiments of these devices.

 It has been proposed to solve this type of drawback by proposing an implant in the form of a shell to facilitate implantation, and comprising around its periphery lights and sharp edges which are embedded in the trays of the vertebrae above and underlying to block any tendency to rotation.

 This type of device due to its cylindrical shape and the presence of sharp edges partially solves the problem of movement of advance and retreat of the implant.

 But there is still a certain instability, the seat, the contact surface and the volume of bone stored remain small and it is always necessary to produce in the corresponding vertebral plates cylindrical housings suitable for receiving said implants using drill or cutter of suitable shape.

 Therefore there is a risk of sinking in the vertebral body because the cancellous bone is not very resistant to compression when the surface layer of cortical bone has been removed.

It will be readily understood that such an intervention to be carried out prior to the placement of the implants, is traumatic and delicate.
The object of the present invention is to remedy these drawbacks by making it possible to avoid any major mechanical intervention on the vertebrae.

 To this end, the invention relates to a dorsolumbar interbody spacer intended to be inserted into the disc space defined between two adjacent vertebrae for the purpose of anatomically restoring the intervertebral space and allowing bone fusion.

 The intersomatic spacer of the invention differs from known devices by a maximum contact surface with the surface of the vertebrae, a larger volume of stored bone and a greater bearing surface relative to the surface of the vertebral plates.

 The spacer is characterized in that it is constituted by at least one element formed by a rigid or weakly resilient vertical side wall of predetermined outline and defining an upper plane and an open lower plane to allow its bone filling.

Said element has a shape preventing the migration of the implant laterally or longitudinally, since any migration is detrimental to bone setting, and allowing the accommodation and centering of said spacer in the disc space, without mechanical intervention on the vertebrae other than '' a distraction of the vertebrae to widen the disc space with metal cams.

 The spacer of the invention has a larger bearing surface than that of the aforementioned implants and improved vertical stability, without the risk of rotation or tilting and without the need for perforation of the bone.

 It can be introduced anterior or posteriorly. Whatever the approach, it is positioned approximately 2 mm from the spinal canal on each side of it.

 In addition, due to its shape, it allows the introduction of a larger volume of bone, which will facilitate fusion.

 The present invention also relates to the characteristics which will emerge during the description which follows and which should be considered in isolation or according to all their possible technical combinations.

This description given by way of nonlimiting example will make it easier to understand how the invention can be produced with reference to the attached drawings in which:
- Figure 1 shows a perspective view of an intersomatic spacer according to the invention arranged on a vertebra, the adjacent vertebra not being shown for better understanding;
- Figures 2, 3 and 4 show respectively in top view, side and end, one of the parts constituting a spacer according to Figure 1.

 - Figure 5 shows a perspective view of an alternative intersomatic spacer according to the invention.

 According to a first embodiment, the spacer generally designated 1 in FIG. 1 is constituted for example by two complementary enantiomorphic elements, that is to say inverted symmetrics, 2 and 3, in the form of bananas or beans, intended to be accommodated. on either side of the disc space, without major mechanical intervention on the vertebrae 9, each of them being delimited by a lateral wall 4, 5 vertical and rigid or weakly resilient, of asymmetrical outline opposing any displacement relative and defining an upper and lower plane open to allow their bone filling.

 According to a characteristic of the invention, the rims 6 and 7, upper and lower of the side walls 4 and 5 of the two elements 2 and 3 constituting the spacer 1 are preferably bristling with notches 8 or made rough to ensure its retention by anchoring in the bone, respectively of each adjacent vertebra 9. In fact, according to the example chosen, said upper and lower edges 6 and 7 of the side walls 4 and 5 of each of the elements 2 and 3 constituting said spacer are in two planes non-parallel with greater front spacing than posterior, so as to define a wedge-shaped spacer, allowing two spacers to be arranged around the center of the vertebral plate and to provide a more balanced support base than that offered by rectangular studs arranged in parallel.

 Preferably, the aforementioned upper and lower planes 6, 7 of the elements 2 and 3 form between them an angle of the order of 1 to 60, so as to cause lordosis.

 The embodiment shown in FIG. 5 differs essentially from that of FIGS. 1 to 4 in that the spacer (26) consists of a single element formed by a rigid or weakly resilient vertical side wall 27 in the shape of a suitable bean. to ensure a balanced central seat.

 In the two embodiments of FIGS. 1 to 4 or 5 the rigid or weakly resilient side walls 4 and 5 or 27 of each of the elements 2 and 3 or 26 comprise a posterior flat zone, respectively 10 and 11 or 29 on which has been formed a possibly threaded hole, respectively 12 and 13 or 30, intended for a tool for gripping and positioning said spacer between the vertebrae 9, then for promoting bone fusion.

 The axis of the hole 12 and 13 or 30 of the elements 2, 3, or 26 is inclined in order to facilitate the entry of the gripping tool.

 But it is also possible to set up the spacer by directly handling the part with pliers.

 In addition, the front end of the elements 2,3, or 26 includes a threaded hole (A) intended for the introduction of a hook for the positioning of said spacer.

 The rigid or weakly resilient side walls 4 and 5 or 27 of each of the elements 2 and 3 or 26 are of generally elongated shape and consist of a posterior zone defined by two parallel flanks 14 and 15 or 31 and 32) connected to faces 10 and 11 or 29 which are perpendicular to them and of an anterior zone defined respectively by prominences 16 and 17 or 33 turned inwards to face each other.

 This increases the contact surface with the vertebrae 9. In this way, the spacer does not penetrate into the cancellous bone, which eliminates the risks of "sinking". It is retained by the cortical bone which is simply curetted.

 The rigid lateral walls 4 and 5 or 27 of each of the elements 2 and 3 or 26, comprise, in zones directed respectively towards the outside and / or the inside, at least one opening of a nature to promote bone fusion. In fact, four holes 18 to 21 are made on the element 2 and four opposite holes 22 to 25 on the element 3. Two holes 34, 35 and two holes 36, 37 are made opposite on item 26.

 According to another characteristic of the invention, the lower part of the side walls 4, 5 or 27 of the elements 2 and 3 or 26 may also include a plurality of small holes 38 (shown in FIG. 5), located opposite and intended to allow the passage of metallic wires 39 or of other biocompatible material arranged so as to retain the bone mass in said cage.

 According to a variant, the wires are replaced by internal undercuts.

 According to an advantageous characteristic of the invention, the elements 2 and 3 or 26 constituting the spacer are obtained in a single piece by machining or molding.

In the case of a spacer made up of two complementary enantiomorphic elements, the two elements can be joined together by a fixing system B, for example in the form of U. (Example of non-limiting connection)
Preferably, the material used for the production of elements 2 and 3 or 26 is a titanium alloy with or without coating
Of course, it is also possible to use other biocompatible materials which may or may not be absorbable or else plastic materials, provided that they allow good visibility to X-rays.

 The use as a material of a thermoplastic material can give the structure a microelasticity promoting bone fusion.

 A range of spacers of different sizes is provided depending on requirements.

 The shape can be slightly modified but it is necessary to maintain two walls that are not entirely parallel (neither cylinder nor parallelepiped).

Claims (13)

 1 - Intersomatic dorso-lumbar spacer intended to be inserted into the disc space defined between two adjacent vertebrae for the purpose of anatomical restoration of the intervertebral space characterized in that it consists of at least one element (2, 3, 26 ) formed of a rigid or weakly resilient vertical side wall (4,5, 27) of predetermined contour and defining an upper plane and an open lower plane to allow its bone filling, said element having a shape capable of allowing the accommodation and the centering of said spacer in the disc space, without major mechanical intervention on the vertebrae.  2 - Spacer according to claim 1, characterized in that it consists of two complementary elements (2, 3).  3 - Spacer according to claim 2 characterized in that the two complementary elements (2, 3) are enantiomorphic.  4 - Spacer according to any one of claims 1 to 3 characterized in that the flanges (6 7 and 28), upper and lower, side walls (4, 5 and 27) of the elements (2, 3 and 26) the constituting, are preferably bristling with notches (8) or made rough intended to ensure its retention by anchoring in the bone respectively of each adjacent vertebra (9).  5 - Spacer according to any one of claims 1 to 4, characterized in that the upper and lower flanges (6, 7 and 28) of the side walls (4, 5 and 27) of the element (s) (2, 3 and 26 ) the component, are part of two non-parallel planes whose front spacing is greater than that posterior so as to define a wedge-shaped spacer, to ensure better seating.  6 - Spacer according to claim 5, characterized in that the upper and lower planes (6, 7 and 28) of the element (s) (2,3 and 26) constituting it preferably form an angle between them of the order of 1 to 60.  7 - Spacer according to any one of the preceding claims, characterized in that the rigid or weakly resilient side walls (4, 5 and 27) of the element (s) (2, 3 and 26) of which it is composed comprise a posterior flat zone (10 , 11 and 29) on which a hole (12, 13 and 30) has been provided for a tool for gripping and positioning said spacer between the vertebrae (9)  8 - Spacer according to any one of the preceding claims, characterized in that the rigid or weakly resilient side walls (4, 5 and 27) of the element or elements (2, 3 and 26) constituting it, are of generally elongated shape and consisting of a posterior zone defined by two generally parallel flanks  (14, 15 and 31, 32) connected to a face (10, 11 and 29) which is perpendicular to them and of an anterior zone defined respectively by prominences (16, 17 and 33) turned inwards.  9 - Spacer according to any one of the preceding claims, characterized in that the rigid or weakly resilient side wall (4, 5 and 27) of the element or elements (2, 3 and 26) constituting it, comprises in directed zones respectively outwards and / or inwards, at least one hole (18 to 25 and 34 to 37) such as to promote bone fusion.  10 - Spacer according to any one of the preceding claims, characterized in that the lower part of the side wall (4, 5 and 27) of the element (s) (2,3 and 26) also includes a plurality of holes (38) of small size, intended to allow the passage of wires (39) or comprising internal under-skids arranged so as to retain the bone mass in the said spacer.  11 - Spacer according to any one of the preceding claims, characterized in that the elements (2, 3 and 26) are obtained in a single piece by machining or molding.  12 - Spacer according to any one of the preceding claims, characterized in that the material used is a titanium alloy, with or without coating, a polymer or other biocompatible radiotransparent material.  13 - Spacer according to any one of the preceding claims, characterized in that the material is a thermoplastic polymer whose microelasticity promotes bone fusion.