PATCH FOR COVERING A DEFECT IN THE ANNULUS FIBROSUS OF AN INTERVERTEBRAL DISC, AND IN PARTICULAR ALSO IN THE POSTERIOR LONGITUDINAL LIGAMENT, OF A SPINE

Abstract

The present invention refers to a patch for covering a defect in the annulus fibrosus of an intervertebral disc, and in particular also in the posterior longitudinal ligament, of a spine. A further aspect of the present invention refers to a surgical kit, including such a patch and at least one fastening element for fastening the patch body to the spine.

Claims

1. A patch for covering a defect in the annulus fibrosus of an intervertebral disc, and in particular also in the posterior longitudinal ligament, of a spine, comprising a patch body that is formed as a sheet, wherein the patch body is formed as a mesh made of non-woven fibres.

2. A patch for covering a defect in the annulus fibrosus of an intervertebral disc, and in particular also in the posterior longitudinal ligament, of a spine, comprising a patch body that is formed as a sheet and has a tensile stiffness between 20?103 N/m and 40?103 N/m, preferably between 25?103 N/m and 35?103 N/m, parallel to a first axis, wherein the first axis lies on a main face of the patch body, preferably wherein the patch body has a tensile stiffness between 20?103 N/m and 40?103 N/m, preferably between 25?103 N/m and 35?103 N/m, parallel to a second axis, wherein the second axis lies on the main face of the patch body and is vertical to the first axis.

3. The patch according to claim 2, wherein the patch body has a total elongation equal to or higher than 160% parallel to the first axis and/or the second axis.

4. The patch according to claim 2, wherein the patch body is configured such that, for achieving a tensile elongation equal to or higher than 50% parallel to the first axis, a tensile load of equal to or less than 150 N, preferably a tensile load of equal to or less than 100 N, is required parallel to the first axis, and/or wherein the patch body is configured such that, for achieving a tensile elongation equal to or higher than 50% parallel to the second axis, a tensile load of equal to or less than 150 N, preferably a tensile load of equal to or less than 100 N, is required parallel to the second axis.

5. The patch according to claim 1, wherein the patch body is made of a material that has a yield strength between 5?10.sup.6 Pa and 8?10.sup.6 Pa.

6. The patch according to claim 1, wherein the patch body is impermeable to the material of the nucleus pulposus of the intervertebral disc.

7. The patch according to any of the preceding claims, claim 1, wherein the patch body comprises at least one through opening for receiving a fastening element for fastening the patch to the spine, preferably at least two through openings that are arranged in the direction of the first axis.

8. The patch according to claim 7, wherein a reinforcing and/or stress distribution element is provided on the patch body around a boundary of the at least one through opening, in particular wherein the reinforcing and/or stress distribution element is made of metal or plastic.

9. The patch according claim to 8, wherein the reinforcing and/or stress distribution element is formed as an insert that is inserted in the at least one through opening, wherein the reinforcing and/or stress distribution element is preferably a grommet.

10. The patch according to claim 8, wherein the reinforcing and/or stress distribution element is fixedly connected to the patch body.

11. The patch according to claim 2, wherein the patch body has a rectangular shape and/or wherein the patch body extends parallel to the first axis more than it extends parallel to the second axis.

12. The patch according to claim 1, wherein the patch body has a circular shape.

13. The patch according to claim 2, wherein a minimum distance between a boundary of the at least one through opening and a boundary of the patch body is at least 5%, preferably at least 10%, of the dimension of the patch body parallel to the first axis and/or the second axis.

14. The patch according to claim 2, wherein the patch body is formed as a mesh made of non-woven fibres.

15. The patch according to claim 1, wherein the mesh comprises/is made of polytetrafluoroethylene fibres and/or expanded polytetrafluoroethylene fibres.

16. A surgical kit, comprising a patch according to any of the claim 1 and at least one fastening element for fastening the patch body to the spine.

Description

[0057] These and further details, advantages and features of the present invention will be described based on embodiments of the invention and by taking reference to the accompanying FIGS. 1 to 9.

[0058] FIG. 1 is a schematic perspective view of a patch according to a first embodiment of the present invention.

[0059] FIG. 2 is a schematic perspective view of a fastening element for fastening the patch to the spine of a person.

[0060] FIG. 3 is a schematic front view of a part of the spine of a person and the patch according to the first embodiment of the present invention fastened to the spine.

[0061] FIG. 4 is a schematic perspective view of a part of the spine of a person and the patch according to the first embodiment of the present invention fastened to the spine.

[0062] FIG. 5 is a schematic front view of an example of a deformed patch according to the first embodiment of the present invention after having been subjected to a tensile load.

[0063] FIG. 6 is a schematic front view of a deformed patch not subject to the present invention after it has been subjected to the same tensile load as the patch of FIG. 5.

[0064] FIG. 7 is a schematic perspective view of a patch according to a second embodiment of the present invention.

[0065] FIG. 8 is a schematic front view of the patch according to the second embodiment of the present invention.

[0066] FIG. 9 is a schematic cross-sectional view of the patch according to the second embodiment of the present invention.

[0067] In the following, embodiments and the technical background of the present invention are presented in detail by taking reference to the accompanying FIGS. 1 to 9. Identical or equivalent elements and elements which act identically or equivalently are denoted with the same reference signs. Not in each case of their occurrence a detailed description of the elements and components is repeated.

[0068] FIG. 1 shows a flexible patch 1 for covering a defect in the annulus fibrosus of an intervertebral disc, an in particular also of the posterior longitudinal ligament, of a spine of a patient according to the first embodiment of the present invention. A part of a spine 500 of a person represented by two vertebrae 504 and an intervertebral disc 501 is shown in FIGS. 3 and 4. For illustrative purposes, the posterior longitudinal ligament is not shown in the figures. When the intervertebral disc 501 has a defect in its annulus fibrosus 502, the patch 1 is intended to be attached to the spine 500 in order to cover said defect and prevent material of the nucleus pulposus 503 of the intervertebral disc 501 from exiting through the defect. This will be further explained with reference to FIGS. 3 and 4.

[0069] Referring back to FIG. 1, the patch 1 comprises a patch body 10 that is formed as a rectangular (flexible) sheet having a length 111, a width 112 and a thickness 113.

[0070] The fact that the patch body 10 is formed as a sheet means that its length 111 and width 112 are each much larger than its thickness 113. In particular, the length 111 and the width 112 of the patch body 10 may each be at least three times larger, preferably at least four times larger, and more preferably at least five times larger than the thickness 113 of the patch body 10. The length 111 of the patch body 10 extends in the direction of a first axis 101 of the patch body 10 and the width 112 in the direction of a second axis 102 of the patch body 10.

[0071] The first axis 101 and the second axis 102 are vertical to each other and lie on a main face 11 of the patch body 10. In particular, the first axis 101 and the second axis 102 lie on a first symmetry plane and a second symmetry plane of the patch body 10, respectively. In other words, the first axis 101 is a first symmetry axis and the second axis 102 a second symmetry axis of the main face 11 of the patch body 10.

[0072] It is noted that the length 111, width 112 and thickness 113 of the patch body 10 as well as the first axis 101 and the second axis 102 refer to the patch body 10 when it lies flat on a surface.

[0073] The patch body 10 has a tensile stiffness parallel to the first axis 101 that lies between 20?10.sup.3 N/m and 40?10.sup.3 N/m, in particular between 25?10.sup.3 N/m and 35?10.sup.3 N/m. Further, the patch body 10 has a tensile stiffness parallel to the second axis 102 that lies between 20?10.sup.3 N/m and 40?10.sup.3 N/m, in particular between 25?10.sup.3 N/m and 35?10.sup.3 N/m. Due to this configuration, the patch 1 is able to deform by the forces being exerted on the vertebrae 504 and consequently also to the body patch 10 being attached to the vertebrae 504 during movement of the spine 500. Thereby, the patch 1 does not limit but rather follows a movement of the vertebrae 504 relative to each other.

[0074] Preferably, the patch body 10 has a total tensile elongation equal to or higher than 160% parallel to the first axis 101 and parallel to the second axis 102. The patch body 10 is further configured such that a tensile load of equal to or less than 150 N, preferably a tensile load of equal to or less than 100 N, is required for achieving a tensile elongation equal to or higher than 50% in the corresponding direction.

[0075] Further, the patch body 10 is formed as a mesh made of non-woven fibres. The mesh comprises polytetrafluoroethylene fibres and/or expanded polytetrafluoroethylene fibres. In addition, the patch body 10 is impermeable to the material of the nucleus pulposus 503 of the intervertebral disc 501.

[0076] In addition, the polytetrafluoroethylene and/or expanded polytetrafluoroethylene fibres have a yield strength between 5?10.sup.6 Pa and 8?10.sup.6 Pa. Thus, they can withstand the forces that are exerted on the patch 1 during movement of the spine 500.

[0077] It can further be seen from FIG. 1 that the patch body 10 comprises a plurality of through openings 12, in particular through holes, for receiving a corresponding number of fastening elements. More specifically, four through openings 12 are provided in the patch body 10 of the present embodiment, which are pairwise arranged in the direction of the first axis 101.

[0078] The minimum distance 114 between a boundary 120 of each of the through openings 12 and a boundary 116 of the patch body 10 parallel to the first axis 101 is at least 5%, preferably at least 10%, of the length 111 of the patch body 10.

[0079] Similarly, the minimum distance 115 between the boundary 120 of each of the through openings 12 and the boundary 116 of the patch body 10 parallel to the second axis 102 is at least 5%, preferably at least 10%, of the width 112 of the patch body 10.

[0080] Due to the described arrangement of the through openings 12 relative to the boundary 116 of the patch body 10, the risk of a tear of the patch body 10 around the through openings 12 can be reduced.

[0081] FIG. 2 shows a screw that can be used as each of the fastening elements 2 for fastening the patch body 10 to the spine 500.

[0082] The patch 1 and the plurality of the fastening elements 2 form a surgical kit.

[0083] In FIGS. 3 and 4, the patch 1 is shown in a state that it is affixed to the spine 500 for covering the defect in the annulus fibrosus 502 of the intervertebral disc 501.

[0084] More specifically, the patch 1 is fastened to the vertebrae 504, between which the intervertebral disc 501 having the defect lies. For a better overview, the fastening elements 2, via which the fixation of the patch 1 to the vertebrae 504 is realised, are omitted from FIGS. 3 and 4.

[0085] It can particularly be understood from FIG. 4 that, in its affixed state to the spine 500, the patch 1 has taken the shape of the intervertebral disc 501 and the vertebrae 504 in its overlapping areas with the intervertebral disc 501 and the vertebrae 504, respectively. Thus, due to its flexibility, the patch 1 is able to effectively seal the defect in the annulus fibrosus 502 of the intervertebral disc 501.

[0086] It can be further derived from FIG. 3 that the first axis 101 of the patch body 10 is substantially parallel to the longitudinal axis 505 of the person's body, while the second axis 102 is substantially parallel to the mediolateral axis 506 of the person's body.

[0087] To highlight the advantages of the patch 1 of the present invention, the result of a simulation (finite element analysis) of an exemplary embodiment of a patch 1 of the present invention being subjected to a tensile force of 50 N parallel to the first axis 101, as shown in FIG. 5, is compared to the result of a simulation (finite element analysis) of an example of another patch 1000 (not according to the present invention) being subjected to the same tensile force, as shown in FIG. 6. It is noted that FIGS. 5 and 6 show the deformed patches 1, 1000 after they have each been subjected to the aforementioned tensile load parallel to the first axis 101.

[0088] Both patches 1, 1000 have the same initial dimensions prior to loading. In particular, the patches 1, 1000 have a length of 15 mm, a width of 10 mm and a thickness of 2.5 mm. Further, all through openings 12 of the patch 1 are formed as through holes with a circular cross-section with a diameter of 2 mm, wherein a distance between the centre of the circular cross-section of the through holes parallel to the first axis 101 is 11 mm and a distance between the centre of the circular cross-section of the through holes parallel to the second axis 102 is 6 mm. The patch 1000 comprises through openings 12 that are in terms of their size, shape and positional arrangement on the patch body 1000 identical to the through openings 12 of the patch 1. On the other hand, the patch 1 according to the exemplary embodiment of the present invention has a tensile stiffness of 30?10.sup.3 N/m parallel to the first axis 101 and the second axis 102 and is formed as a mesh comprising polytetrafluoroethylene and/or expanded polytetrafluoroethylene fibres, whereas the patch 1000 has a tensile stiffness of 700?10.sup.3 N/m in the corresponding directions and is made of PTFE (solid material not made of fibres).

[0089] The length of the deformed patch 1 of the present invention is denoted by the reference sign 111 in FIG. 5, while the length of the example of the deformed patch 1000 is denoted by the reference sign 1111 in FIG. 6.

[0090] When comparing FIGS. 5 and 6, it becomes apparent that the length 111 of the deformed patch 1 according to the exemplary embodiment of the present invention is greater than the length 1111 of the patch 1000. In other words, the patch 1 according to the exemplary embodiment of the present invention has experienced a greater tensile deformation parallel to the first axis 101 than the tensile deformation that the patch 1000 according to the example not being subject to the present invention has experienced in the corresponding direction.

[0091] In particular, the tensile deformation of the patch 1 at the middle of the patch body 10 in a direction parallel to the first axis 101 according to the exemplary embodiment of the present invention is 1.7 mm, whereas the corresponding tensile deformation of the patch 1000 is 0.068 mm.

[0092] Thus, the patch 1 according to the exemplary embodiment of the present invention is able to sufficiently deform in an elastic manner during the movement of the spine 500, thereby matching the displacement of the vertebrae 504 relative to each other, e.g. during a bending movement of the person as denoted by arrow 507 in FIG. 4. Further, the force needed for achieving said deformation lies within the range of the forces exerted on the vertebrae 504 during the movement of the spine 500. On the contrary, the patch 1000 is so stiff that it would negatively affect the mobility of the spine 500 and more specifically of the vertebrae 504.

[0093] FIGS. 7 to 9 refer to a patch 1 according to a second embodiment of the present invention.

[0094] The patch 1 according to the second embodiment differs from the patch 1 according to the first embodiment in that the patch 1 according to the second embodiment comprises a plurality, in particular four, reinforcing and stress distribution elements 13.

[0095] Each reinforcing and stress distribution element 13 is provided on the patch body 10 around the boundary 120 of a corresponding through opening 12.

[0096] Further, each of the reinforcing and stress distribution elements 13 is formed as an insert that is inserted in a corresponding through opening 12. In particular, all reinforcing and stress distribution elements 13 are formed as grommets that are made of plastic or metal and each have a main grommet body 130 and two collars 131 integrally formed with the main grommet body 130. Each collar 131 is arranged on a main face 11 of the patch body 10, while the main grommet body 130 is inserted in the through opening 12.

[0097] The reinforcing and/or stress distribution elements 13 can in particular be fixedly connected to the patch body 10.

[0098] The reinforcing and stress distribution elements 13 provide protection to the patch body 10 around the through openings 12 and are configured to prevent or minimize stress concentrations around the through openings 12 by distributing stresses over a larger area of the patch body 10.

[0099] The depicted and described features and further properties of the invention's embodiments can arbitrarily be isolated and recombined without leaving the gist of the present invention.

[0100] Though the patch 1 according to the first and second embodiments has been described and is primarily intended as a solution for covering a defect in the annulus fibrosus of an intervertebral disc of a spine of a human, it is possible that the patch 1 can be used in animals, in particular primates, as well.

[0101] In addition to the foregoing description of the present invention, for an additional disclosure explicit reference is taken to graphic representation of FIGS. 1 to 9.

LIST OF REFERENCE SIGNS

[0102] 1 patch [0103] 2 fastening element [0104] 10 patch body [0105] 11 main face [0106] 12 through opening [0107] 13 reinforcing and/or stress distribution element [0108] 101 first axis [0109] 102 second axis [0110] 111 length [0111] 111 length [0112] 112 width [0113] 113 thickness [0114] 114 distance [0115] 115 distance [0116] 116 boundary [0117] 120 boundary [0118] 130 main grommet body [0119] 131 collar [0120] 500 spine [0121] 501 intervertebral disc [0122] 502 annulus fibrosus [0123] 503 nucleus pulposus [0124] 504 vertebra [0125] 505 longitudinal axis [0126] 506 mediolateral axis [0127] 507 arrow [0128] 1000 patch [0129] 1111 length [0130] 1120 through opening