FR2730156A1 - Inter-spinal wedge implant useful esp. for vertebral prosthesis - Google Patents

Abstract

The implant comprises: (a) a central core (3) of a visco-elastic material with channels for the passage of ligaments, and (b) upper and lower thin metal plates (2,4) which are identical in shape to the upper and lower surfaces of the core, to which they are fitted. The implant is surrounded by a woven or knitted strip (5) of a textile material.

Description

INTER-SPINOUS HOLDER
The present invention relates to an improvement made to the interspinous wedges used in the formation of vertebral prostheses.

 The technical field of the invention is that of the manufacture of vertebral prostheses.

 Patent application FR-A-2 693 364 (VOYDEVILLE) describes an intervertebral prosthesis allowing stabilization of the rotational and flexion-extension stresses.

 The prosthesis described in this document comprises a flexible ligament comprising a first thin part and a second wide part to allow lacing in "8" around the thorny of two contiguous vertebrae and to perform peri-spinous strapping; the prosthesis comprises a semi-flexible interspinous wedge pierced with two pairs of through channels, adapted for the passage of the two respective parts of the ligament, and further comprises means for closing the ligament on itself.

 Patent application FR-A-2 700 941 (FELMAN) describes a semi-rigid interspinous wedge, composite. comprising a core of synthetic fabric braided and wound on itself and comprising a titanium shell enveloping on all sides the core of synthetic fabric, which is trapezoidal in shape having six faces; the prosthesis also has four metal attachment appendages and four textile attachment appendages.

 The object of the present invention is to provide an improved vertebral interspinous wedge for entering into the constitution of a high performance vertebral prosthesis.

 The problem posed, in particular by the prosthesis described in the VOYDEVILLE document which includes a polyester ligament and a semi-flexible polyester wedge also, is that the pressure forces between the wedge and the thorny ones, or else between the wedge and the ligament , can cause wear of the components of the prosthesis resulting in abrasion of the contacting surfaces which results in the production of free polyester particles which can lead to very serious inflammations.

 The present invention aims in particular to remedy this drawback of wedges for vertebral prostheses.

 The solution to the problem posed consists in providing, in accordance with the invention, an interspinous wedge, essentially constituted by an elastic or substantially viscoelastic cylindrical core, which wedge is provided with interfaces or faces of contact with the thorny plants, which are metallic, and said wedge comprises means for controlling the deformation of the elastic core, which means for controlling the deformation are preferably constituted by a textile strip encircling the elastic body.

In other words, the invention consists in providing an interspinous wedge provided with at least two channels for the passage of a ligament, essentially constituted by
- a central body in visco-elastic material in the form of a cylinder provided with two parallel faces,
an upper, thin, flat, metallic plate, the contour of which is substantially identical to the director of said cylinder, which is placed or pressed against the upper face of said body,
- a lower plate substantially identical to said upper plate, which is placed or pressed against the lower face of said body,
- a textile band, woven or knitted, surrounding or encircling said body.

According to preferred embodiments of the invention
the director of said cylinder is substantially symmetrical with respect to its longitudinal axis,
the director of said cylinder is substantially constituted by two half-directors arranged symmetrically with respect to a longitudinal axis, each of the half-directors consisting of three successive curvilinear sections arranged end to end, a first convex curvilinear section, a second concave curvilinear section, a third convex curvilinear section,
- said body is substantially symmetrical with respect to a plane
P1, each half-body comprising three adjacent curvilinear lateral faces, a first convex curvilinear front face, a second concave central curvilinear face, a third convex rear curvilinear face,
said lower and upper plates are symmetrical with respect to a plane P1, each half-plate comprising three adjacent lateral faces, a first convex curvilinear face, a second concave curvilinear face, a third convex curvilinear face,
said body is essentially constituted by a block of silicone, said plates are essentially constituted by titanium, and said strip is made of polyester textile, that is to say of a material different from the material used for the production of said body,
the wedge comprises preferably textile links making it possible to attach or fix the strip or belt to the edge of said lower and upper plates,
each of said lower and upper plates has orifices for the passage of links, for example 4 in number, preferably arranged symmetrically with respect to respective longitudinal axes of said plates,
- Said textile strip is wound around said body in several turns or windings, and comprises a first turn or winding conforming to the concave wall forming part of the side walls of said cylinder, which strip comprises a second turn not marrying said concave wall or lateral face of said cylinder, as well as the towers of higher rows,
- Said ligament passage channels are delimited by successive windings of said strip, and have a cross section whose surface is very large (for example at least 5 to 10 times greater) relative to the surface of a cross section of the ligament.

 According to a preferred embodiment, the thickness of said plates is less than half the thickness of said body, for example of the order of 1 / 5th to 1 / 10th of the thickness of said body.

 All the components of the block according to the invention and their particular arrangement give this block an elastic behavior both in compression and in extension.

 The shims according to the invention avoid or at least greatly limit the production of particles originating from wear by contact or friction of the abrasive parts of said shim thanks in particular to the presence of means for controlling the elasticity and / or the deformation (crushing) of the central body, which are preferably constituted by a textile band surrounding this body; it is also possible to avoid cracking or wear phenomena of the central body, which can be caused after a certain time after the implantation of these wedges.

 Thanks to the presence of metal plates, preferably made of titanium, forming interfaces or faces of contact with the thorns, wear of the central elastic block (preferably silicone) is avoided and thanks to the textile belt surrounding the silicone block, also prevents shearing of the central block and its wear.

 The particular shape of the silicone block and the particular arrangement of the textile band encircling the silicone block, make it possible to define wells or housings for passage of a ligament (for fixing the wedge between two prickles) which make it possible to avoid or very strongly limit any friction and consequently any production of free particles, likely to cause inflammations.

 The numerous advantages provided by the invention will be better understood through the following description which refers to the appended drawings which illustrate without any limiting character a preferred embodiment of the invention.

 Figure 1 illustrates in exploded schematic perspective view the four essential components of a wedge used in the composition of a vertebral prosthesis according to the invention.

 Figure 2 which is substantially a view along II of Figure 1, illustrates in plan view an interspinous wedge according to the invention.

 The interspinous wedge 1 is essentially constituted by an upper plate 2 intended to be placed and pressed against the upper face 6 of a central cylindrical body 3, a lower plate 4 identical to the upper plate 2, being arranged or pressed against the underside 7 of the central body 3.

As shown schematically in Figure 1 and more particularly
Figure 2, the central body 3 and possibly the upper and lower plates (2, 4) are surrounded or surrounded by a textile band 5 which is wound around the wedge in several turns, as shown schematically in Figure 2, in which the references 13 and 14 designate the longitudinal ends of said strip 5; the references 30 and 31 of FIG. 1 refer to the longitudinal edges of said strip 5, which longitudinal edges are mutually parallel and separated by a distance 23 constituting the width of the strip 5.

 The width or height 23 of the strip 5 is thus close to the height 18 of the central body 3, possibly equal to the sum of the respective heights 17, 18, 19, of said lower plate of said central body 3 and of said upper plate.

 As illustrated in FIG. 1, said body 3, as well as said lower and upper plates 2, 4 are of cylindrical shape, said plates 2, 4 being thin or very flat, their respective thickness 17, 19 being for example of the order of 0 , 5 to 1 millimeter, for a thickness of the central body 3 for example of the order of 10 millimeters.

 Said body 3 and said plates 2, 4 have an identical or very similar profile which is respectively symmetrical with respect to respective longitudinal axes of these three elements which are marked 10, 11 and 12, which axes are parallel and contained in a plane P1 of general symmetry.

 It can be seen in particular in FIG. 1 that, concerning the upper plate 2, said plate extends along the longitudinal axis 10, is symmetrical with respect to this axis, has four holes or orifices 16 passing through the thin plate 2, which serve to the attachment by sewing with textile ties 15 for example, as illustrated in FIG. 2, of the various windings of the strip 5 with said end plates 2 and 4.

 With reference to FIG. 1, said upper plate 2 comprises a convex curvilinear face 36, which is adjacent to a concave curvilinear face 37, itself adjacent to a rear convex curvilinear face 38.

 As illustrated in FIGS. 1 and 2, an angular point or a sharp edge can be provided at the junction of the two convex curvilinear "front" faces 36 of said plate 2, as illustrated as regards the central body 3, which comprises also convex curvilinear faces 20 located in the front part of said central body which are arranged symmetrically with respect to a plane P1 of general symmetry of the wedge, the two symmetrical faces 20 being joined by an edge 27 carrying an angular point 9, as also illustrated Figure 2.

 It can therefore be seen in this FIG. 1 that said central body 3 comprises, in addition to said convex curvilinear front face 20, a concave curvilinear central face 21, followed by a convex curvilinear rear face 22, whose respective upper edges 33, 34, 35 constitute curvilinear sections which are respectively convex, concave and convex, and which define the semi-director of the cylinder delimiting the central body 3; said cylinder has a vertical axis (relative to Figure 1) which is marked 32 in this Figure.

 It can also be seen in FIG. 1 that protruding edges 28, 29 constitute the border between said respective faces 20, 21 on the one hand and 21, 22 on the other hand, of said central body 3.

 As illustrated in FIG. 2, said strip 5 is wound around said wedge, that is to say around said body and said upper and lower plates which are pressed against the upper and lower faces of the body 3, to constitute a first turn s extending from one end 13 of said strip, which first turn or winding 25 is in contact with or conforms to the external shape of said central block 3 and possibly of said plates and in particular intimately follows the concave central face 21 formed in the central body 3 on either side of it, while the second turn or winding 26 of said strip 5 and possibly the following successive windings (ending with the second end 14 of strip 5) are not all pressed intimately against said concave wall 21, so that they extend substantially in a fictitious oval shape 8 shown in dotted lines in FIG. 2, and thus delimit with said first winding, that is to say with the concave face of said body 3, two cylindrical channels 24 extending parallel to the axis identified 32 Figure 1, and allowing the passage of a wedge fixing ligament to two consecutive spiny spines.

Claims (10)

 1. Interspinous wedge provided with at least two channels (24) for passage of a ligament, characterized in that it is essentially constituted by  a central body (3) of visco-elastic material in the form of a cylinder (3) provided with two parallel faces (6, 7),  - an upper, thin, flat, metallic plate (2), the contour of which is substantially identical to the director of said cylinder, which is placed or pressed against the upper face (6) of said body (3),  - a lower plate (4) substantially identical to said upper plate (2), which is placed or pressed against the lower face (7) of said body (3),  - a textile band (5), woven or knitted, surrounding or encircling said body (3).  2. Wedge according to claim 1, wherein the director of said cylinder is substantially symmetrical with respect to its longitudinal axis (11).  3. Wedge according to any one of claims 1 to 2, wherein the director of said cylinder is substantially constituted by two half-directors arranged symmetrically with respect to a longitudinal axis (11), each of the half-directors consisting of three curvilinear sections successive arranged end to end, a first curvilinear section (33) convex, a second curvilinear section (34) concave, a third curvilinear section (35) convex.  4. Wedge according to any one of claims 1 to 3, in which said body (3) is substantially symmetrical with respect to a plane P1, each half-body comprising three adjacent curvilinear side faces, a first curved front convex face (20 ), a second concave central curvilinear face (21), a third convex rear curvilinear face (22).  5. Wedge according to any one of claims 1 to 4, in which said lower and upper plates (2, 4) are symmetrical with respect to a plane P1, each half-plate comprising three adjacent lateral faces, a first convex curvilinear face. (36), a second concave curvilinear face (37), a third convex curvilinear face (38).  6. Wedge according to any one of claims 1 to 5, wherein said body is essentially constituted by a silicone block, said plates are essentially constituted by titanium, and said strip is made of polyester textile.  7. Wedge according to any one of claims 1 to 6, comprising ties (15) preferably textiles for attaching or fixing the band (5) or belt at the edge of said lower and upper plates (2, 4).  8. Wedge according to claim 7, wherein each of said lower and upper plates has orifices (16) for passage of the links (15).  9. Wedge according to any one of claims 1 to 8, wherein said strip is wound around said body (3) in several turns (25, 26), and comprises a first turn (25) matching the concave wall (21) forming part of the side walls of said cylinder, which strip has a second turn which does not conform to said concave wall (21).  10. Wedge according to any one of claims 1 to 9, wherein said channels (24) for passage of the ligament are delimited by successive windings of said strip (5).