STENT FOR PERCUTANEOUS VERTEBROPLASTY

Abstract

A stent for percutaneous vertebroplasty is described having a substantially tubular body that can be transitioned from a compressed state into an expanded state. The wall of the tubular body has a plurality of openings ensuring the expansion both in the longitudinal direction and in the peripheral direction of the stent. The stent has a cross-sectional shape deviating from the circular shape at least in the expanded state.

Claims

1. A stent for percutaneous vertebroplasty having a substantially tubular body that can be transitioned from a compressed state into an expanded state, and having a central region wherein a wall of the tubular body has a plurality of openings ensuring the expansion both in the longitudinal direction and in the peripheral direction of the stent, wherein the stent has a cross-sectional shape deviating from the circular shape at least in the expanded state.

2. The stent in accordance with claim 1, wherein the stent has a circular cross-section in the compressed state.

3. The stent in accordance with claim 1 or claim 2, wherein the stent has at least one flattened longitudinal side, at least in the expanded state.

4. The stent in accordance with claim 3, wherein the stent has two, three, four or more flattened longitudinal sides, at least in the expanded state.

5. The stent in accordance with claim 3, wherein the stent has two flattened longitudinal sides that are arranged disposed opposite one another.

6. The stent in accordance with claim 1, wherein the stent has a substantially polygonal, rectangular, substantially square or oval cross-sectional shape at least in the expanded state.

7. The stent in accordance with claim 1, wherein the stent has a substantially rectangular cross-sectional shape in the expanded state.

8. The stent in accordance with claim 7, wherein the stent having the substantially square cross-sectional shape has four flattened longitudinal sides in the expanded state of which two respective longitudinal sides are arranged extending in parallel with one another and disposed opposite one another.

9. The stent in accordance with claim 1, wherein the stent has the cross-sectional shape deviating from the circular shape at least over a part region of its longitudinal extent.

10. The stent in accordance with claim 9, wherein the stent has the cross-sectional shape deviating from the circular shape at least in the central region of the stent.

11. The stent in accordance with claim 1, wherein the stent has the cross-sectional shape deviating from the circular shape over its total longitudinal extent.

12. The stent in accordance with claim 1, wherein the stent comprises a tapering end tapering in the axial direction at least in the expanded state.

13. The stent in accordance with claim 12, wherein the other end of the stent is likewise formed as tapering.

14. The stent in accordance with claim 12, wherein the tapering end of the stent is substantially conical, frustoconical, pyramid-shaped or frusto-pyramidal shaped.

15. The stent in accordance with claim 12, wherein the other end of the stent substantially has the same cross-sectional shape and/or the same cross-sectional area as the central region of the stent at least in the expanded state.

16. The stent in accordance with claim 1, wherein both ends of the stent substantially have the same-cross-sectional shape and/or the same cross-sectional area as the central region of the stent at least in the expanded state.

17. The stent in accordance with claim 1, wherein the stent is configured as a balloon-expandable stent.

18. The stent in accordance with claim 1, wherein the stent is configured as a self-expanding stent.

19. The stent in accordance with claim 18, wherein a material of the stent comprises a memory material.

20. The stent in accordance with claim 19, wherein the stent substantially or completely consists of a memory material.

Description

[0020] Further advantageous embodiments of the invention are set forth in the dependent claims.

[0021] The invention will be described in more detail in the following with reference to embodiments and to the drawings; there are shown in these:

[0022] FIG. 1 a perspective representation of a stent for percutaneous vertebroplasty in accordance with the prior art;

[0023] FIG. 2 a simplified perspective representation of the stent in accordance with FIG. 1;

[0024] FIG. 3 a cross-section along the line A-A of FIG. 2;

[0025] FIG. 4 a schematic cross-sectional view of a compressed vertebral body with an inserted stent in accordance with FIG. 1 in the compressed state;

[0026] FIG. 5 a vertebral body in accordance with FIG. 4 with an expanded stent;

[0027] FIG. 6 a further compressed vertebral body with two inserted stents in accordance with FIG. 1 in the compressed state;

[0028] FIG. 7 the vertebral body in accordance with claim 6 with expanded stents;

[0029] FIG. 8 a schematic perspective representation of a stent in accordance with the invention with a square cross-section;

[0030] FIG. 9 a cross-section through the stent in accordance with FIG. 8;

[0031] FIG. 10 a slightly modified cross-sectional shape;

[0032] FIG. 11 a schematic cross-sectional view of a compressed vertebral body with an inserted stent in accordance with FIG. 8 in the compressed state;

[0033] FIG. 12 the vertebral body in accordance with FIG. 11 with an expanded stent;

[0034] FIG. 13 a schematic view of a compressed vertebral body with two inserted stents in accordance with FIG. 8 in the compressed state;

[0035] FIG. 14 the vertebral body in accordance with FIG. 13 in the expanded state;

[0036] FIG. 15 a schematic side view of the stent in accordance with FIG. 8;

[0037] FIGS. 16 to 18 further schematic side views of stents in accordance with the invention; and

[0038] FIGS. 19 to 21 schematic representations of different cross-sectional shapes of a stent in accordance with the invention.

[0039] In all the embodiments, the same, similar or mutually corresponding elements are marked by the same reference numerals.

[0040] FIG. 1 shows a stent 1 having a tubular body 2 that has a mesh structure such that a plurality of openings 3 are formed in the wall of the body 2 that repeat both in the longitudinal direction and in the peripheral direction of the stent 1. FIG. 2 shows the same stent 1 in a simplified perspective representation from which it can in particular clearly be recognized that the stent 1 has a circular cross-section. The circular cross-section of the stent 1 is in this respect identical over the total length of the stent 1 such that the body 2 forms a cylinder jacket having openings 3. The openings 3 are in this respect of diamond shape and are created in that the stent 1 is transitioned from a compressed state, not shown, having a clearly reduced diameter, into the expanded state shown in FIG. 1 and FIG. 2, with the openings 3 being widened to enable the expansion. In the compressed state of the stent 1, the openings 3 can, for example, be formed as slit-like openings that extend in parallel next to one another in the axial direction, with slit-shaped openings respectively disposed next to one another in the peripheral direction being arranged alternately offset with one another.

[0041] The circular cross-section of the stent 1 is shown again in a simplified form in FIG. 3.

[0042] The stent in accordance with FIGS. 1 to 3 is a stent for percutaneous vertebroplasty known from the prior art. In accordance with FIG. 4, such a stent is inserted in the shown compressed state, i.e. with a reduced diameter, into the vertebral body cavity 4 of a collapsed vertebral body 5. The insertion in this respect takes place in a known manner by means of a delivery catheter.

[0043] The stent 1 is widened, for example via a balloon catheter, into its expanded position shown in FIG. 5 after a successful placement. Due to the circular cross-section of the stent 1, it only comes into contact with the inner sides 6, 7 of the vertebral body 5 via linear support points 8, 9 via which the total erection force is introduced into the vertebral body 5 on a further expansion of the stent. An additional fracture point can therefore arise in the region of the linear support points 8, 9 during the expansion, such as are indicated by dashed lines 10, 11.

[0044] This problem also occurs when, as shown in FIGS. 6 and 7, two stents 1 are inserted into the vertebral body cavity 4 and are subsequently expanded in the usual manner for widening the vertebral body 5. Both stents 1 are here also only in contact with the inner sides 6, 7 of the vertebral body 5 via linear support points 8, 9 such that the material of the vertebral body 5 is extremely strained in these regions.

[0045] FIG. 8 shows a stent 12 in accordance with the invention in a likewise simplified perspective representation that, unlike the previously described stent 1, has a square cross-section such as is shown schematically in FIG. 9. Unlike the stent 1, the stent 12 in accordance with the invention has a cross-sectional shape deviating from the circular shape and in particular has two oppositely disposed flattened longitudinal sides 13, 14 that form enlarged support surfaces such as will be explained in more detail in the following. The two other oppositely disposed longitudinal sides 25 of the stent 12 are likewise correspondingly flattened. As can be recognized from FIG. 10, the cross-section of the stent 12 does not have to be exactly mathematically square in this respect, but the side surfaces can rather be slightly arcuate and the corners can be rounded as long as the flattened longitudinal sides 13, 14 form support surfaces that are not only in linear contact with the inner sides 6, 7 of the vertebral body 5, but rather form areal contact regions therewith.

[0046] This can be recognized from FIGS. 11 and 12. The stent 12 in accordance with the invention is inserted into the vertebral body cavity 4 of the collapsed vertebral body 5 in its compressed state in FIG. 11. If the stent 12 is transitioned from its compressed state into the expanded state shown in FIG. 12, the two flattened longitudinal sides 13, 14 are pressed areally toward the inner sides 6, 7 of the vertebral body 5 such that the force transferred from the stent 12 to the vertebral body on the expansion is distributed over a larger surface and the vertebral body 5 is thus not strained in a linear manner as with conventional stents. The risk that an additional fracture of the vertebral body 5 occurs on the expansion of the stent 12 and on the widening of the vertebral body 5 is thereby minimized. Furthermore, it is achieved by the likewise flattened longitudinal sides 25 that simultaneously extend perpendicular to the support surfaces (and thus in the direction of the erection movement of the vertebral body 5) that the erection force that can be generated by the stent 12 is considerably increased with respect to the erection force of the stent 1.

[0047] If a stent is used that has a circular cross-section in the compressed state, it is advantageous if the cross-sectional shape changes at a relatively early point during the expansion from the circular shape into a cross-sectional shape differing from the circular shape, in particular having oppositely disposed flattened longitudinal sides. It is thereby ensured that the force transmitted to the vertebral body during the expansion is distributed over a larger surface during the total expansion process or at least during a large part of the expansion process. It is, however, generally also conceivable that the cross-sectional shape of the stent only changes into a shape deviating from the circular shape briefly before or on the reaching of the expanded state such that substantially only the final support of the widened vertebral body takes place over increased surfaces. These possible embodiments are also applicable to the further embodiments described in the following. Such a stent in accordance with the invention can thus be configured in accordance with FIG. 4 in the compressed state and in accordance with FIGS. 8 to 10 and 12 in the expanded state.

[0048] On a use of two stents 12 in accordance with the invention, such as is shown schematically in FIGS. 13 and 14, the total support surface, and thus the total surface for the force transmission from the stents 12 to the vertebral body 5, is further increased such that the risk of an additional fracture of the vertebral body 5 can be further reduced. The stents 12 can here, deviating from the representation in accordance with FIG. 13, also have a circular cross-section in the compressed state. The stents 12 can thus be configured in accordance with FIG. 6 in the compressed state and in accordance with FIGS. 8 to 10 and 14 in the expanded state.

[0049] The expansion of the stent 12 can in this respect take place via balloon dilatation. It is, however, also possible that the stent 12 is a self-expanding stent that is automatically transitioned after placement by the body temperature from its compressed state into its expanded state due to its formation from a memory material such as Nitinol. A cross-section circular in the compressed state and a cross-section at least regionally rectangular or square in the expanded state can in particular be imparted to the self-expanding stent on its manufacture.

[0050] FIGS. 15 to 18 show side views of differently configured stents in accordance with the invention in a schematic representation. FIG. 15 in this respect shows a side view of the stent 12 of FIG. 8, with, as also in the following Figures, only the outline of the side view being shown. Since the stent 12 in accordance with FIG. 8 has a parallelepiped-shaped body, the outline of the side view only forms the rectangle shown in FIG. 15. Both the cross-sectional shape and the cross-sectional size are thus identical over the total length of the stent in this stent.

[0051] The outline of a side view of a modified stent 15 is shown in FIG. 16. In this stent 15, a main part 16 is configured in accordance with the stent 12, i.e. with a square cross-section. A conically tapering end 17 adjoins this main part 15 and opens in an end-face opening 18 of the stent 15. The oppositely disposed end-face opening 19 of the stent 15 in contrast has a clearance that corresponds to the inner lumen of the stent 15 in its main part 16.

[0052] With the stent 15, for example, the delivery instruments for introducing and placing the stent 15 can be guided through the large end-face opening 19 such that the delivery catheter can be withdrawn from the stent 15 without problems after the placement of the stent. Bone cement can furthermore be injected into the interior of the stent 15 in a simple manner via the larger end-face opening 19 to improve the stability of the stent 15 and thus of the expanded vertebral body 5. It is prevented by the tapering end 17 of the stent having the reduced end-face opening 18 that the bone cement introduced into the interior of the stent 15 can exit the distal side of the stent 15 again. The tapering end 17 can in this respect, for example, be of frusto-pyramidal shape or of frustoconical shape, i.e. can be formed with a square or rectangular cross-section, with a polygonal cross-section or with a circular cross-section. This also applies to the tapering sections of the following stents described in the following.

[0053] The stent 20 shown in a side view in FIG. 17 only differs from the stent 15 in accordance with FIG. 16 in that the tapering end 17 does not form an open end of the stent 20, but rather a closed end. An outflow of the bone cement injected into the stent 20 is thereby completely or at least largely prevented.

[0054] It can be recognized from FIG. 18 that a stent 21 in accordance with the invention can have two tapering ends 17, 22. As is shown in FIG. 18, the two tapering ends 17, 22 can form different end-face openings 18, 19 of the stent and can also have different cone angles. The two tapering ends 17, 22 can generally also be identical.

[0055] If the proximal end of the stent is formed as tapering, the stent can, when necessary, for example on an incorrect positioning, be withdrawn into the delivery catheter again and can subsequently be repositioned.

[0056] It is common to all the stents shown that they have a cross-section deviating from the circular shape at least in the expanded state and, for example, as shown in FIGS. 9 and 10, have a square cross-section. Deviating from the square cross-section, stents in accordance with the invention can, for example, also have cross-sectional shapes such as are shown in FIGS. 19 to 21. A hexagonal cross-section is shown in FIG. 19, for example, whereby in turn two oppositely disposed flattened longitudinal sides 13, 14 are implemented. The same also applies to the cross-section shape in FIG. 20 in which the oppositely disposed flattened longitudinal sides 13, 14 are connected to one another by curved side surfaces 23, 24.

[0057] It is shown in FIG. 21 that the cross-section of a stent in accordance with the invention can also be configured as an elongated rectangle so that, for example, as shown in FIG. 14, two stents 12 arranged next to one another can be replaced with a simple stent in accordance with the invention having a larger width.

REFERENCE NUMERAL LIST

[0058] 1 stent [0059] 2 body [0060] 3 openings [0061] 4 vertebral body cavity [0062] 5 vertebral body [0063] 6 inner side [0064] 7 inner side [0065] 8 linear support point [0066] 9 linear support point [0067] 10 fracture point [0068] 11 fracture point [0069] 12 stent [0070] 13 flattened longitudinal side [0071] 14 flattened longitudinal side [0072] 15 stent [0073] 16 main part [0074] 17 tapering end [0075] 18 end-face opening [0076] 19 end-face opening [0077] 20 stent [0078] 21 stent [0079] 22 tapering end [0080] 23 curved side surface [0081] 24 curved side surface [0082] 25 flattened longitudinal sides