MEDICAL DEVICE, IN PARTICULAR A FLOW DIVERTER, AND KIT

Abstract

The invention concerns a medical device, in particular a flow diverter, having a radially self-expandable lattice structure (10) which is tubular at least in some regions and which is composed of a plurality of interwoven individual wires (11) which form meshes (12) of the lattice structure (10), wherein at least some of the individual wires (11) have an X-ray visible core material (11a) and a superelastic mantle material (11b), wherein a plurality of directly adjacent meshes (12) in the circumferential direction of the lattice structure (10) form a mesh ring (13), wherein in a fully self-expanded state, the lattice structure (10) has an expansion diameter D.sub.exp, the mesh ring (13) has a mesh number n, and the core material (11a) has a core diameter d.sub.core, and wherein for the core diameter d.sub.core, the following holds:

d.sub.core=f.Math.(D.sub.exp/n)

wherein the following holds for a visibility factor f:

0.08≤f≤0.15

Claims

1. A medical device, in particular a flow diverter, having a radially self-expandable lattice structure (10) which is tubular at least in some regions and which is composed of a plurality of interwoven individual wires (11) which form meshes (12) of the lattice structure (10), wherein at least some of the individual wires (11) have an X-ray visible core material (11a) and a superelastic mantle material (11b), characterized in that a plurality of directly adjacent meshes (12) in the circumferential direction of the lattice structure (10) form a mesh ring (13), wherein in a fully self-expanded state, the lattice structure (10) has an expansion diameter D.sub.exp, the mesh ring (13) has a mesh number n, and the core material (11a) has a core diameter d.sub.core, and wherein for the core diameter d.sub.core, the following holds:
d.sub.core=f.Math.(D.sub.exp/n) wherein the following holds for a visibility factor f:
0.08≤f≤0.15.

2. The medical device as claimed in claim 1, characterized in that the expansion diameter D.sub.exp is 2.5 mm to 8 mm.

3. The medical device as claimed in one of the preceding claims, characterized in that a braiding angle α of the lattice structure (10) is between 70° and 80°, in particular 75°.

4. The medical device as claimed in one of the preceding claims, characterized in that the wire (11) has a wire diameter d.sub.wire, which is in the case of an expansion diameter D.sub.exp of 2.5 mm to 4.5 mm: 30 μm≤d.sub.wire≤46 μm, and in the case of an expansion diameter D.sub.exp of more than 4.5 mm to 8 mm: 46 μm≤d.sub.wire≤65 μm.

5. The medical device as claimed in one of the preceding claims, characterized in that the mantle material (11b) of the wire has a thickness which is at least 10 μm, in particular at least 15 μm, in particular 10 μm to 20 μm.

6. The medical device as claimed in one of the preceding claims, characterized in that the volume of the core material (11a) takes up a percentage of the total volume of the wire (11), wherein in the case of a visibility factor f of 0.08 to 0.15, the percentage of the total volume is from 13% to 45%, in particular from 15% to 40%.

7. The medical device as claimed in one of the preceding claims, characterized in that the volume of the core material (11a) takes up a percentage of the total volume of the wire (11), wherein in the case of a visibility factor f of 0.08, the percentage of the total volume is from 15% to 25%, in particular from 18% to 22%.

8. The medical device as claimed in one of the preceding claims, characterized in that the volume of the core material (11a) takes up a percentage of the total volume of the wire (11), wherein in the case of a visibility factor f of 0.1, the percentage of the total volume is from 15% to 30%, in particular from 20% to 25%.

9. The medical device as claimed in one of the preceding claims, characterized in that the volume of the core material (11a) takes up a percentage of the total volume of the wire (11), wherein in the case of a visibility factor f of 0.12, the percentage of the total volume is from 20% to 35%, in particular from 25% to 30%.

10. The medical device as claimed in one of the preceding claims, characterized in that the volume of the core material (11a) takes up a percentage of the total volume of the wire (11), wherein in the case of a visibility factor f of 0.15, the percentage of the total volume is from 25% to 45%, in particular from 30% to 40%.

11. The medical device as claimed in one of the preceding claims, characterized in that in a fully compressed state, the lattice structure (10) has a compression diameter D.sub.comp which is at most 0.7 mm, in particular at most 0.6 mm, in particular at most 0.51 mm, in particular at most 0.42 mm.

12. The medical device as claimed in one of the preceding claims, characterized in that the lattice structure (10) has closed loops (15) at one longitudinal axial end (14) and open wire ends at the other longitudinal axial end.

13. The medical device as claimed in one of the preceding claims, characterized in that the core material (11a) consists of platinum or a platinum alloy or of tantalum or a tantalum alloy.

14. The medical device as claimed in one of the preceding claims, characterized in that the mantle material (11b) consists of a nickel-titanium alloy, in particular nitinol.

15. The medical device as claimed in one of the preceding claims, characterized in that the following holds for the visibility factor f: 0.08≤f≤0.14, in particular 0.08≤f≤0.13, in particular 0.08<f≤0.12, in particular 0.08≤f≤0.11, in particular f=approximately 0.1.

16. The medical device as claimed in one of the preceding claims, characterized in that the proportion of the individual wires (11) with the X-ray visible core material (11a) and the superelastic mantle material (11b) with respect to the total number of individual wires (11) is at least 50%, in particular at least 75%, in particular 100%.

17. The medical device as claimed in one of the preceding claims, characterized in that the mesh number n for a mesh ring (13) is: in the case of an expansion diameter D.sub.exp of 2.5 mm to 4.5 mm (2.5 mm≤D.sub.exp≤4.5 mm): 12≤n≤24, in particular 16≤n≤24, and in the case of an expansion diameter D.sub.exp of more than 4.5 mm to 8 mm (4.5 mm<D.sub.exp≤8 mm): 24<n≤36, in particular 24<n<32.

18. A kit with a medical device as claimed in one of the preceding claims and a catheter, wherein in a compressed state, the medical device can be disposed in the catheter by displacing it longitudinally.

19. The kit as claimed in claim 18, characterized in that the medical device can be connected to or is connected to the transport wire, in particular releasably connected.

20. The kit as claimed in claim 18 or claim 19, characterized in that in the case of an expansion diameter D.sub.exp of 2.0 mm≤D.sub.exp≤3.5 mm, in particular 2.5 mm≤D.sub.exp≤3.5 mm, the catheter has an internal diameter of 2 Fr to 2.5 Fr, in particular 2 Fr, in particular 2.5 Fr, in the case of an expansion diameter D.sub.exp of 3.5 mm<D.sub.exp≤5 mm, the catheter has an internal diameter of 2.5 Fr to 3 Fr, in particular 2.5 Fr and in particular 3 Fr, and in the case of an expansion diameter D.sub.exp of 5 mm<D.sub.exp, the catheter has an internal diameter of 3 Fr to 4 Fr, in particular 3 Fr, in particular 4 Fr.

Description

[0048] The invention will now be described in more detail with the aid of an exemplary embodiment and with reference to the accompanying diagrammatic drawings, in which:

[0049] FIG. 1: shows a diagrammatic side view of a medical device, in particular of a flow diverter according to an exemplary embodiment in accordance with the invention;

[0050] FIG. 2: shows a diagrammatic view of a mesh of the lattice structure of the medical device according to FIG. 1; and

[0051] FIG. 3: shows a diagrammatic view of a cross sectional profile of an individual wire of the medical device in accordance with FIG. 1.

[0052] The exemplary embodiment of a medical device in accordance with the invention represented in the figures is a flow diverter which is suitable for treatment in intracranial blood vessels. In general, the medical device may be configured as a medical instrument or as a medical implant. In any event, the medical device can preferably be fed through a catheter in a minimally invasive manner to a treatment site, in particular within a blood vessel.

[0053] Medical implants, in contrast, remain substantially permanently at their treatment site. Implants of this type are flow diverters which are used for the treatment of aneurysms in blood vessels.

[0054] The flow diverter represented in the accompanying drawings is preferably suitable for the treatment of aneurysms in intracranial blood vessels. The flow diverter has a tubular, radially expandable lattice structure 10 produced from a plurality of interwoven individual wires 11 which form the meshes 12 of the lattice structure 10.

[0055] The lattice structure 10 is highly compressible and can therefore be guided through small catheters to the treatment site. The lattice structure 10 has a high bending flexibility, so that feeding and anchoring in highly tortuous blood vessels is readily facilitated.

[0056] As can be seen in FIG. 1, the lattice structure 10 has a plurality of meshes 12 which respectively form mesh rings 13 when viewed in the circumferential direction of the lattice structure 10. A mesh ring 13 is formed from a plurality of meshes 12 which are disposed directly adjacent to one another in the circumferential direction of the lattice structure. In this regard, the individual meshes are separated from each other by intersections 18 of the individual wires 11.

[0057] The lattice structure 10 is constructed from a plurality of mesh rings 13 which are directly adjacently disposed in the longitudinal direction of the lattice structure 10. Preferably, each mesh ring 13 has an even number of meshes 12. In particular, the mesh ring 13 may have 12, 14, 16, 32 or more meshes.

[0058] The lattice structure 10 is self-expandable and expands autonomously without the influence of external forces. In this unloaded state, the lattice structure 10 takes up the expansion diameter D.sub.exp. In a fully expanded state, then, the lattice structure 10 has the expansion diameter D.sub.exp .

[0059] In contrast, the action of an external force is necessary in order to transpose the lattice structure 10 into a compressed state. A state in which the lattice structure 10 takes up its smallest possible diameter is the fully compressed state. In this fully compressed state, the lattice structure 10 has a compression diameter D.sub.comp. Upon compression of the lattice structure 10, the width of a mesh 12 reduces in the circumferential direction of the lattice structure 10. This reduction in the width occurs until the sections of wire which border the meshes 12 are in contact with one another. The wire 11 then blocks any further compression of the lattice structure 10. For mechanical or geometrical reasons, then, the lattice structure 10 cannot simply be compressed to any desired extent, but takes up a minimum diameter beyond which any further compression is no longer possible. This state forms the fully compressed state in which the lattice structure 10 has a compression diameter D.sub.comp.

[0060] A compression diameter D.sub.comp which is as small as possible is advantageous in order to be able to feed the lattice structure 10 to the treatment site through a catheter which is as small as possible. In this regard, in particular, the lattice structure is provided so as to be compressible or so that it can take up such a compression diameter D.sub.comp such that the lattice structure can be guided to the treatment site through a catheter with an internal diameter of at most 3 French, in particular 2.5 French, in particular at most 2 French. Specifically, the lattice structure may take up a compression diameter D.sub.comp which is at most 0.7 mm, in particular 0.6 mm, in particular at most 0.51 mm, in particular at most 0.42 mm.

[0061] At least one individual wire 11 of the lattice structure 10 is formed as a composite wire. A plurality of individual wires 11, in particular a portion, for example 50% or 75%, of all individual wires 11 or in fact all individual wires 11, i.e. 100% of the individual wires 11, may each be produced as composite wires.

[0062] In this regard, the individual wires 11 have an X-ray visible core material 11a and a superelastic mantle material 11b. The core material 11a may in particular be composed of platinum, a platinum alloy, tantalum and/or a tantalum alloy. In each case, the core material 11a preferably has an enhanced visibility under X-rays. This means that the entire lattice structure 10 can easily be detected by the operator during implantation.

[0063] In contrast, the mantle material 11b acts to provide the self-expansion properties of the lattice structure 10. To this end, the mantle material 11b has superelastic properties. In particular, the mantle material may be formed by a shape memory material which takes up a previously set shape under the influence of the environmental temperature. A shape memory material of this type may in particular be formed by a nickel-titanium alloy. Preferably, the mantle material 11b is tailored such that upon reaching the body temperature of a human being, it urges the lattice structure 10 into the fully expanded state.

[0064] Depending on the desired size of the lattice structure 10 or of the medical device, in particular the stent, advantageously, the diameter of the core material, the core diameter d.sub.core, is tailored accordingly. In particular, the self-expansion properties, the compressibility and the X-ray visibility of the lattice structure 10 should be matched to the best possible extent. In this regard, it has been shown that an advantageous core diameter d.sub.core for different expansion diameters D.sub.exp is one given by the product of the quotients from the expansion diameter D.sub.exp and the mesh number n of the meshes 12 of the mesh ring 13 as well as a visibility factor f. The visibility factor f is at least 0.08 and at most 0.15, in particular at most 0.12.

[0065] Specifically, it has been shown that a core diameter calculated using the foregoing parameters results in good X-ray visibility of the lattice structure 10, wherein the lattice structure 10 can also self-expand properly and can be compressed to a small compression diameter. In this regard, the following formula holds:

d.sub.core=f.Math.(D.sub.exp/n)

for lattice structures 10 with different expansion diameters D.sub.exp.

[0066] In particular, the calculation of the core diameter d.sub.core is made using this formula and leads to good parameters for lattice structures 10 which have an expansion diameter D.sub.exp between 2.5 mm and 8 mm. Such lattice structures 10 are particularly suitable for use in intracranial blood vessels.

[0067] In order to obtain good compressibility for the lattice structure 10, in the exemplary embodiments described here, the wire 11 particularly advantageously has a total wire diameter d.sub.wire of at most 65 μm, in particular at most 60 μm, in particular at most 55 μm, in particular at most 40 μm. In particular, the wire 11 may have a wire diameter d.sub.wire of between 30 μm and 65 μm, preferably between 40 μm and 50 μm. Specifically, the wire diameter d.sub.wire may be 40 μm or 45 μm or 50 μm. Wires of this thickness enable particularly good compression of the lattice structure 10, and therefore give rise to a very small compression diameter D.sub.comp. This ensures that the lattice structure 10 can be guided smoothly through small catheters to the treatment site.

[0068] For lattice structures 10 with an expansion diameter D.sub.exp of between 2.5 mm and 3.5 mm, wire diameters d.sub.wire of between 30 μm and 40 μm have been shown to be advantageous. For lattice structures 10 with an expansion diameter D.sub.exp of between 3.5 mm, in particular 4 mm, and 5.5 mm, wire diameters d.sub.wire of between 30 μm, in particular 38 μm, more particularly more than 40 μm, and 50 μm, have been shown to be advantageous. For lattice structures 10 with an expansion diameter D.sub.exp of between 5.5 mm, in particular 7 mm, and 8 mm, wire diameters d.sub.wire of between 42 μm, in particular 46 μm, and 65 μm have been shown to be advantageous.

[0069] It has also been shown that as regards the self-expansion properties of the lattice structure 10, an advantageous wire 11 is one in which the mantle material has a thickness h of at least 10 μm. In the case of a wire diameter d.sub.wire of 40 μm, this produces a maximum possible core diameter of 20 μm. FIG. 3 clearly shows that by means of a thickness h of 10 μm for the man material 11b with a wire diameter d.sub.wire of 40 μm, a core diameter d.sub.core of at most 20 μm remains for the core material 11a. The lower limit for the thickness h of the mantle material may also be at least 15 μm.

[0070] The percentage volume of the core material 11a with respect to the total volume of an individual wire 11 can be calculated from the preceding geometrical information. This substantially corresponds to the quotient between the square of the ratio between the product of the visibility factor f and the mesh width b to the square of the wire diameter d.sub.wire. The mesh width b is produced from the ratio between the expansion diameter D.sub.exp and the mesh number n. Specifically, the volume fraction φ of the core material 11a can be calculated as follows:

φ=(f.Math.D.sub.exp/n).sup.2/d.sub.wire.sup.2

[0071] Expressed as a percentage, this means that in the case of a visibility factor f of 0.08, the percentage volume φ of the core material 11a with respect to the total volume of the wire 11 is from 15% to 25%, in particular from 18% to 22%. Preferably, in the case of a visibility factor f of 0.01, the percentage fraction of the total volume is from 15% to 30%, in particular from 20% to 25%. Preferably, in the case of a visibility factor f of 0.12, the percentage fraction of the total volume is from 20% to 35%, in particular from 25% to 30%. Preferably, in the case of a visibility factor f of 0.15, the percentage fraction of the total volume is from 25% to 45%, in particular from 30% to 40%.

[0072] FIG. 2 shows a section of the lattice structure 10 of the medical device or stent in accordance with FIG. 1. Specifically, FIG. 1 shows an individual mesh 12 of the lattice structure 10 which is bordered by wire sections of a plurality of individual wires 11. As is usually the case with braided lattice structures 10, the mesh 12 is rhomboidal.

[0073] FIG. 2 also clearly shows how the individual wire 11 is constructed as a composite wire. In particular, for the purposes of illustration, it can be seen that the core material 11a runs through the individual wire 11 and is sheathed by the mantle material 11b. Under radiographic monitoring, the core material 11a in particular can be detected, because the radiographic density is particularly high in the region of the intersections 18 of the individual wires 11. Thus, the intersections 18 are particularly easy to detect under radiographic monitoring.

[0074] The braiding angle a of the lattice structure 10 in the embodiment shown is preferably between 70 and 80 degrees, preferably 75 degrees, wherein a tolerance of ±3 degrees is acceptable. The braiding angle a in the context of the present application is that angle which is between a longitudinal axis of the lattice structure 10 and the individual wire 11. In this regard, the individual wire 11 is wound in a helical manner about the longitudinal axis. This is the case for all of the individual wires.

[0075] In general, the invention is based on the following considerations:

[0076] For a product series of medical devices, in particular stents, the lattice structure of which respectively have substantially the same construction, but wherein the individual products differ in their expansion diameter D.sub.exp, it is sensible to raise the mesh number n of the individual rows of meshes 13 with increasing expansion diameter D.sub.exp.

[0077] The width b of the individual mesh can in general be calculated from the expansion diameter D.sub.exp and the mesh number n as follows:

b=πD.sub.exp/n

[0078] In the context of the present application, the ratio D.sub.exp/n between the expansion diameter D.sub.exp and the mesh number n is defined as the width ratio R.sub.GS.

[0079] In the case of a high width ratio R.sub.GS, the individual meshes are comparatively wide. This has the disadvantage that embolic material such as coils in an aneurysm are difficult to retain with the lattice structure 10.

[0080] In the case of a small width ratio R.sub.GS, in contrast, the mesh width b is small. This means that the lattice structure 10 is less flexible in bending, so that navigation of the medical device through a catheter is made more difficult. In addition, a small mesh width b means that microcatheters which are used to introduce coils into an aneurysm can only be guided through the meshes with difficulty.

[0081] Thus, advantageously, a mesh width b is provided which reaches a compromise between the properties of a flow diverter which are important for aneurysm treatment (see above) and good navigability of the lattice structure 10. In this regard, it has been shown that a width ratio R.sub.GS in the range from 0.1 mm to 0.3 mm provides good results. Multiplying by π produces a preferred mesh width b of between 0.3 mm and 0.9 mm.

[0082] The width ratio R.sub.GS between the expansion diameter D.sub.exp and the mesh number n in the case of an expansion diameter D.sub.exp of between 2.5 mm and 3.5 mm is between 0.10 mm and 0.22 mm, in particular between 0.15 mm and 0.20 mm. In the case of an expansion diameter D.sub.exp of between 3.5 mm and 6 mm, the width ratio R.sub.GS between the expansion diameter D.sub.exp and the mesh number n is preferably between 0.15 mm and 0.25 mm, in particular 0.18 mm and 0.22 mm, preferably approximately 0.2 mm. In the case of an expansion diameter D.sub.exp of between 6 mm and 7 mm, the width ratio R.sub.GS is between 0.2 mm and 0.30 mm, in particular between 0.22 mm and 0.25 mm.

[0083] The braiding angle a influences the mechanical expansion behaviour, the flexibility and the feedability of the medical device. A braiding angle a of between 70° and 80°, preferably 75°, has been shown to be suitable for the treatment of intracranial blood vessels by medical devices with a lattice structure 10 which have an expansion diameter D.sub.exp of between 2.5 mm and 8 mm.

[0084] In the case of a pre-specified width ratio R.sub.GS and, as a consequence, of a pre-specified mesh width b as well as a pre-specified braiding angle a, the mesh 12 has a rhomboidal shape and size which, in combination with the wire diameter d.sub.wire, results in a braid density or a porosity. In this regard, the braid density provides the proportion of the total curved surface of the lattice structure which is formed by the wire 11, i.e. minus the area of the openings of the meshes 12. In contrast, the porosity provides the proportion of the total curved surface of the lattice structure which is formed by the sum of the opening areas of the meshes 12. In addition, the width ratio R.sub.GS influences the maximum inscribed circle diameter of the mesh 12, which is also defined as the “pin opening”.

[0085] The wire diameter d.sub.wire together with the braiding angle a and the width ratio R.sub.GS influence the braid density or the porosity of the lattice structure 10 and in addition has an effect on the radial force and the feedability of the medical device. The following wire diameters d.sub.wire have been shown to be advantageous for different expansion diameters D.sub.exp: [0086] in the case of an expansion diameter D.sub.exp of between 2.5 mm and 4.5 mm i.e. 2.5 mm≤D.sub.exp≤4.5 mm: 30 μm≤d.sub.wire≤46 μm, and [0087] in the case of an expansion diameter D.sub.exp of between more than 4.5 mm and 8 mm, i.e. 4.5 mm<D.sub.exp≤8 mm: 46 μm<d.sub.wire<65 μm.

[0088] The length of the lattice structure 10 is preferably between 10 mm and 50 mm.

[0089] For good X-ray visibility, the wire 11 has an X-ray visible core material 11a with a core diameter d.sub.core. When selecting the core diameter d.sub.core, the size of the individual meshes 12 plays an important role. The wider and longer are the meshes 12, the lower is the braid density of the lattice structure 10. A high core diameter d.sub.core for the wire 11 means that it can be detected easily under radiographic monitoring.

[0090] In particular, the mesh width b influences the spacing between the intersections 18 of a mesh row 13. The crossing sections of the wire 11 overlap at the intersections 18 and therefore form regions with an enhanced radiographic density. The further apart the intersections 18 are, the larger the core diameter d.sub.core should be in order to ensure good visibility of the lattice structure 10. In particular, a high number of intersections not only makes the surface of the lattice structure 10 easy to detect; the shape of the lattice structure 10 which fits itself to the vessel wall can also be detected.

[0091] The width ratio R.sub.GS determines the density of the intersections 18 of a mesh row 13. The smaller the width ratio R.sub.GS, the smaller is the separation of the intersections 18 and the higher is the braid density of the lattice structure 10.

[0092] In the case of a high width ratio R.sub.GS, a relatively larger core diameter d.sub.core is advantageous. For a small width ratio R.sub.GS, a correspondingly smaller core diameter d.sub.core is sufficient.

[0093] It has been shown that a ratio between the core diameter d.sub.core and the width ratio R.sub.GS of between 0.08 and 0.15, in particular 0.10, more particularly 0.12, produces good results. The aforementioned ratio in the context of the present application is defined as the visibility factor f.

[0094] In the case of a visibility factor f of 0.08, for a width ratio R.sub.GS of between 0.17 and 0.20, an advantageous core diameter d.sub.core of between 13.3 μm and 16 μm is produced. For a larger width ratio R.sub.GS, the core diameter d.sub.core can be raised up to 20 μm.

[0095] In the case of a visibility factor f of 0.10, for a width ratio R.sub.GS of between 0.17 mm and 0.20 mm, an advantageous core diameter d.sub.core of between 16.7 μm and 20 μm is obtained.

[0096] In order to ensure a sufficient torsion resistance and thus a suitable restoring force in the case of spring-like deformation of the wire 11, advantageously, the mantle material 11b has a thickness h which is at least 10 μm. In the case of the maximum wire diameter d.sub.wire of approximately 60 μm, this then produces an upper limit for the core diameter d.sub.core of approximately 40 μm.

[0097] In the case of an expansion diameter D.sub.exp of 3.5 mm and a preferred wire diameter d.sub.wire of 38 μm, the core diameter d.sub.core must not be more than 18 μm, because otherwise, the proportion of mantle material 11b would be too low. Thus, in order to obtain this, a visibility factor of 0.08 or 0.10 should be selected. In the case of a larger expansion diameter D.sub.exp, the preferred wire diameter d.sub.wire is approximately 50 μm, for example. For lattice structures 10 of this type, the core diameter d.sub.core can therefore be up to 30 μm. In the case of a lattice structure 10 with an expansion diameter D.sub.exp of 6 mm, therefore, a larger visibility factor f of up to 0.15 would be possible.

[0098] A visibility factor f of 0.08 may be used when the width ratio R.sub.GS is low or the wire diameter d.sub.wire is high.

[0099] By selecting a suitable visibility factor f, a percentage of the volume of the core material 11a with respect to the total volume of the wire 11 is produced. Preferably, in the case of a visibility factor f of 0.08, the percentage volume of the core material with respect to the total volume is 15% to 25%, in particular 18% to 22%. Preferably, in the case of a visibility factor f of 0.1, the percentage of the total volume is 15% to 30%, in particular 20% to 25%. Preferably, in the case of a visibility factor f of 0.12, the percentage of the total volume is 20% to 35%, in particular 25% to 30%. Preferably, in the case of a visibility factor f of 0.15, the percentage of the total volume is 25% to 45%, in particular 30% to 40%.

[0100] In this regard, it has been shown that for the following wire diameters d.sub.wire, the following core diameters d.sub.core are preferred:

[0101] For d.sub.wire=45 μm: d.sub.core=from 22 μm to 28 μm, in particular approximately 25 μm.

[0102] For d.sub.wire=50 μm: d.sub.core=from 24 μm to 35 μm, in particular from 26 μm to 32 μm, in particular approximately 27 μm or approximately 32 μm.

[0103] For d.sub.wire=55 μm: d.sub.core=from 27 μm to 38 μm, in particular from 29 μm to 36 μm, in particular approximately 30 μm or approximately 35 μm.

[0104] For the following expansion diameters D.sub.exp for the lattice structure, the following wire diameters d.sub.wire are advantageous:

[0105] Expansion diameter D.sub.exp of 2.5 mm to 4.5 mm: wire diameter (d.sub.wire of 30 μm to 46 μm, in particular 34 μm to 42 μm;

[0106] Expansion diameter D.sub.exp>4.5 mm to 6 mm: wire diameter d.sub.wire of 42 μm to 55 μm, in particular 46 μm to 50 μm;

[0107] Expansion diameter D.sub.exp>6 mm to 8 mm: wire diameter d.sub.wire of 42 μm to 65 μm, in particular from 50 μm to 60 μm.

[0108] The preferred thickness h of the mantle material is calculated as follows:

h=(d.sub.wire−d.sub.core)/2

[0109] Thus, the mantle material 11b has a thickness h which for the aforementioned preferred wire diameter d.sub.wire is at least 9 μm (in the case of d.sub.wire=50 μm and d.sub.core=31.6 μm) and at most 12.4 μm (in the case of d.sub.wire=55 μm and d.sub.core=30.1 μm).

[0110] In respect of the mesh number n, preferably, lattice structures 10 with an expansion diameter D.sub.exp of between 2.5 mm and 8.0 mm preferably have approximately 12 to 36 meshes 12, in particular 16 to 32 meshes 12, per mesh ring 13.

[0111] Lattice structures 10 with an expansion diameter D.sub.exp of between 2.5 mm and 3.5 mm preferably have 16 to 20 meshes 12 per mesh ring 13. In the case of lattice structures 10 with an expansion diameter D.sub.exp of between 3.5 mm and 5.0 mm, mesh rings 13 with respectively 20 to 26 meshes may be provided. Lattice structures 10 with an expansion diameter D.sub.exp of between 5.0 mm and 8 mm preferably have a mesh number n of 26 to 32.

REFERENCE NUMERALS

[0112] 10 lattice structure

[0113] 11 wire

[0114] 11a core material

[0115] 11b mantle material

[0116] 12 meshes

[0117] 13 mesh ring

[0118] 14 longitudinal end

[0119] 15 free

[0120] 16 free

[0121] 17 free

[0122] 18 intersection

[0123] D.sub.exp expansion diameter

[0124] D.sub.comp compression diameter

[0125] d.sub.core core diameter

[0126] d.sub.wire wire diameter

[0127] b mesh width

[0128] f visibility factor

[0129] h thickness of mantle material 11b

[0130] R.sub.GS width ratio

[0131] a braiding angle

[0132] β mesh angle

[0133] n mesh number

[0134] φpercentage by volume