Sleeve-shaped medical implant

Abstract

The invention relates to a sleeve-shaped medical implant which has a film-like, flexible planar substrate which, by means of material-inherent impressed shaping, automatically adopts, without application of external force, the form of a straight cylinder, in which the planar substrate provides a cylinder interior surface which, in the implanted state, is able to form an extravascular or extraneuronal surface contact along an intracorporeal strand-like structure in the form of an intracorporeal vessel or a nerve fibre bundle. The invention is characterized in that the film-like, flexible planar substrate has two edge regions which, in the implanted state, lie opposite each other along a cylinder axis assigned to the straight cylinder form, and in that the edge regions are each limited by an undulating edge contour line.

Description

[0001] Cuff-shaped medical implant

[0002] Technical area

[0003] The invention relates to a cuff-shaped medical implant comprising a foil-like, flexible surface substrate which, due to a material-inherent shaping, independently and without external force, assumes the shape of a straight cylinder, in which the surface substrate provides an inner surface of the cylinder which, in the implanted state, is capable of forming an extravascular or extraneuronal surface contact along an intracorporeal strand-like structure in the form of an intracorporeal vessel or a nerve fiber bundle.

[0004] State of the art

[0005] The document EP 3204 105 B1 discloses a cuff electrode arrangement, also referred to as a cuff electrode, which consists of a flexible, biocompatible carrier substrate, preferably a polyimide film, and provides a plurality of individual electrodes on at least one of the carrier substrate's upper sides. The known cuff electrode is used for the spatially resolved detection of neuronal electrical signals and for the selective electrical stimulation of individual nerve fibers running within a nerve fiber bundle. To ensure that the cuff electrode remains positioned as gently as possible along the nerve fiber bundle, preferably along the vagus nerve, on the one hand, and as stationary as possible, the film-like carrier substrate is imprinted with a material-inherent mechanical prestress, through which the film-like carrier substrate automatically forms into a straight-cylindrical wound cuff, forming at least one complete wound layer.The straight-cylindrical wound cuff shape embossed into the foil-like carrier substrate is selected in accordance with the extraneuronal shape and size of the nerve fiber bundle in such a way that the contact pressure exerted by the cuff electrode on the epineurium of the nerve fiber bundle ensures, on the one hand, a stationary hold along the nerve fiber bundle, but, on the other hand, neither constricts the nerve fiber bundle nor places excessive mechanical stress on it.

[0006] It cannot be ruled out that anatomically induced relative movements between the organic structure, e.g., the vagus nerve, and the cuff electrode may cause tissue irritation, particularly at the axially opposite side edges of the cylindrically wound carrier substrate. These should be eliminated or significantly reduced to avoid irreversible damage or injury to the epineurium of the nerve fiber bundle.

[0007] Another example of a cuff-shaped implant is disclosed in DE 10 2017 222 362 B4, which relates to a foil-like wrap-around cuff having at least one flat wrapping that overlaps itself at least partially and encompasses the cylindrical cavity. It can be joined exclusively for the purpose of securing it along an intracorporeal vessel or a nerve fiber bundle by means of a form-fitting and / or frictional connection. The wrap-around cuff, which serves purely as a fastening means, serves to absorb tensile forces directed at an intracorporeally located implant. In this case, too, it is important to avoid any negative irritation or even damage to the organic structure caused by the fastening wrap-around cuff.

[0008] Another example of a cuff-shaped implant is explained in the document EP 3 833 425 B1, which represents a protective structure for a cuff electrode described above and consists of two integrally connected straight-cylindrical half-shells that can be converted from an open state, in which the protective structure can be placed around a cuff electrode applied along a nerve fiber bundle, into a closed state in which the cuff-shaped protective structure completely surrounds the internal cuff electrode, preferably axially and in its circumferential direction. Like the cuff electrode, the protective structure is also made of a flexible, biocompatible, film-like carrier substrate into which a prestressing force is inherently introduced, automatically assuming the closed straight-cylindrical shape.

[0009] The publication DE 10 2007 036 862 A1 describes an electrode for intraoperative nerve stimulation. It has a strip-shaped substrate that can be applied around the vagus nerve, forming a single loop, similar to a cable tie. For fastening purposes, the strip-shaped carrier substrate has lateral, undulating locking tracks that lock into an opening when simply wrapped.

[0010] Description of the invention

[0011] The invention is based on the object of developing a cuff-shaped implant which has a film-like, flexible surface substrate which, due to a material-inherent shaping, independently and without the application of external force assumes the shape of a straight cylinder, in which the surface substrate has an inner surface of the cylinder which, in the implanted state, is able to form surface contact with a strand-shaped intracorporeal structure at least in some areas, in such a way that tissue irritations on the intracorporeal structure, in particular due to shear forces which may occur on the axially opposite end edges of the cuff-shaped implant, can be avoided or at least significantly reduced.

[0012] The solution to the problem underlying the invention is specified in claim 1. Features that advantageously further develop the inventive concept can be found in the subclaims and the further description, in particular with reference to concrete illustrated embodiments.

[0013] The cuff-shaped implant according to the solution with the features of the preamble of claim 1 is characterized in that the film-like, flexible surface substrate has two edge regions which, in the implanted state, lie opposite one another along a cylinder axis associated with the straight cylinder shape, and in that the edge regions are each delimited by a wavy edge contour line.

[0014] The idea underlying the invention avoids straight, axial boundary edges on the cuff-shaped implant, which directly abut the tissue surface of the respective cord-like intracorporeal structure, in particular the epineurium of a nerve fiber bundle. The edge regions, which are monolithically connected to the foil-like, flexible surface substrate, are each laterally delimited by an edge contour line that is continuously differentiable in the mathematical sense, i.e., does not provide any angular line points or areas. The edge contour line is preferably sinusoidal or formed as a sinusoidal curve and characterized by a recurring sequence of wave-crest-shaped area flaps projecting laterally from the respective edge region.Due to the wave-contour-like design of the edge regions, shear forces occurring at the edges during relative movements between the cuff-shaped implant and the strand-shaped intracorporeal structure are evenly distributed over all curves along the edge contour line, thus preventing local tearing of the film-like, flexible surface substrate along the edge regions.

[0015] In addition, with larger movement amplitudes of the cuff-shaped implant relative to the cord-shaped intracorporeal structure, the axially projecting flap-like "wave crests" of the wave-contour-like edge regions fold axially toward the surface substrate and radially outwardly rest against the straight-cylinder cuff shape. In this way, funnel-shaped, rounded contours form at the edges between the epineurium or the tissue surface and the folded wave crest-shaped area flaps, preventing any harmful tissue irritation from occurring during relative movement between the cuff-shaped implant and the cord-shaped intracorporeal structure.

[0016] In a preferred embodiment, the two edge regions delimited by the wavy edge contour lines are thinner than the rest of the surface substrate in order to achieve increased flexibility in the edge regions and to enable the respective wave-climb-shaped region flaps to be folded over more easily and quickly. The film-like, flexible surface substrate preferably has a first film thickness D, which typically measures 15 pm < D < 20 pm. The edge regions each delimited by a wave-shaped edge contour line are at least a quarter to a half of the thickness D thinner. In this way, the surface flexibility in the edge regions is increased and supports the folding process of the respective wave-climb-shaped region flaps.The reduced film thickness within the edge regions also means that the restoring force imprinted in the film-like, flexible surface substrate, which allows for self-forming into a straight cylindrical shape, has no or only a negligible restoring effect in these areas near the edges. The size of the edge regions is determined, on the one hand, by the length, which preferably corresponds to the circumference of the cuff-shaped implant, and, on the other hand, by a width that is at least twice the amplitude attributable to the wave-like edge contour line.

[0017] The two axially opposite edge areas along the straight cylindrical shape also serve as mechanical damping between the inherent stiffness of the cuff-shaped implant and the tissue surface of the strand-like intracorporeal structure, e.g. the epineurium of a nerve fiber bundle, and thus creates a soft and rounded “impedance transition” between the foil-like flexible surface substrate on the one hand and the organic tissue structure on the other.

[0018] In a preferred embodiment, the number and a periodic or aperiodic sequence of individual waveforms along the edge contour line are adapted to the length of the peripheral edge of the straight cylindrical shape of the cuff-shaped implant in such a way that both wave-shaped edge contour lines each completely encompass the peripheral edge of the straight cylindrical shape once, i.e., a single time. This means that the wave-peak-shaped area flaps projecting axially from the surface substrate do not radially overlap with a second one. This ensures that the wave-peak-shaped area flaps can be folded over due to relative movement unhindered and without collision with other wave-peak-shaped area flaps connected to the film-like, flexible surface substrate.

[0019] The measure according to the solution, concerning the provision of edge regions each laterally delimited by a wavy edge contour line on the axially opposite circumferential edges of a cuff-shaped implant which independently forms a straight cylinder, is particularly suitable for the formation of wound cuffs in general and in combination with a cuff electrode in particular, for example in combination with the cuff electrode of the document EP 3 204 105 B1 explained at the outset, on whose cylinder jacket inner surface of the film-like, flexible surface substrate electrode structures are provided.

[0020] In the same way, it is possible to provide the edge regions according to the solution on a protective structure that can be assembled from two cylinder half-shapes to form a straight cylinder, which is described in the document EP 3 833 425 B1 explained at the beginning.

[0021] Brief description of the invention

[0022] The invention is described below, without limiting the general inventive concept, using exemplary embodiments with reference to the drawings. They show:

[0023] Fig. 1 ad schematic, tabular comparison of a known cuff-shaped implant - left table column - with a cuff-shaped implant designed according to the solution - right table column and

[0024] Fig. 2 a, b composed of two cylinder half shells

[0025] protective structure.

[0026] Ways of implementing the invention, industrial applicability

[0027] The left column of Figure 1a shows a biocompatible, flexible carrier substrate 1 known per se, for example in the form of a polyimide film, which has a rectangular basic shape and, due to a shape inherently embossed in the material, independently and without the application of external force takes on the shape of a straight-cylindrical winding sleeve 2, as shown in the left column of Figure 1b. The flat substrate 1 is wound around a flat substrate side edge 4 to form at least one complete winding layer, wherein the two opposite side edges 7 adjoining orthogonally to the flat substrate side edge 4 form the circumferential edge edges 7 axially opposite one another along the cylinder axis 3 when the straight-cylindrical winding sleeve 2 is formed. As an alternative to a rectangular basic shape of the flat substrate 1, a square basic shape or similar is also conceivable.

[0028] For the application of the implantable wrap cuff 2, which can be removed from the left column of Figure 1, along a strand-like intracorporeal structure 5, for example along a nerve fiber bundle, in particular along the vagus nerve, the surface substrate 1 in the stretched form, see Figure 1a, is positioned laterally on the strand-like intracorporeal structure 5 and then applied in a self-fixing manner by independently wrapping around the strand-like intracorporeal structure 5, as can be seen in the left column of Figure 1c.

[0029] In the case of permanent longitudinal movements 6 of the wrapped cuff 2 along the cord-like intracorporeal structure 5, the circumferential side edges 7 of the wrapped cuff 2 axially opposite to the cylinder axis 3 can act as friction and cutting edges and lead to damage to the cord-like intracorporeal structure 5, for example in the form of local tissue peeling 8.

[0030] To prevent such damage, the biocompatible, flexible surface substrate of the cuff-shaped implant 2* according to the invention is modified such that the film-like, flexible surface substrate 1* has two opposing edge regions 10, each of which is laterally delimited by a wave-shaped edge contour line 11, see Figure 1a, right column. The wave-shaped edge contour lines 11 have no corners and are mathematically continuously differentiable. A sinusoidal curved line or a sinusoidal curve is particularly suitable as the edge contour line 11, which has a periodic sequence of wave-peak-shaped region flaps 12 projecting from the edge.

[0031] The length 9 of the edge regions 10, each delimited by a wave-shaped edge contour line 11, approximately corresponds to the circumference of the cord-shaped intracorporeal structure 5. This ensures that when the wrap-around cuff 2* is applied around the cord-shaped intracorporeal structure 5, the two edge regions 10 axially opposite each other along the cylinder axis 3* of the wrap-around cuff 2* only encompass the cord-shaped intracorporeal structure 5 in a single layer, see Figure 1 b, right column. The width 19 of the edge regions 10 should correspond to at least twice the amplitude A of a wave-crested region flap 12, preferably three to ten times the amplitude.

[0032] If longitudinal relative movements 7 occur between the wrap cuff 2* and the cord-like intracorporeal structure 5 in the implanted state (see Figure 1c, right column), the wave-shaped region flaps 12 of the wave-like structured edge regions 10 fold radially outward and nestle against the outer side of the wrap cuff 2*, forming a funnel-shaped contour 13 between the wrap cuff 2* and the surface of the cord-like intracorporeal structure 5 (see Figure 1d, right column). Due to the funnel-shaped contour 13, the shear forces that would otherwise occur as a result of the described longitudinal relative movement 6 between the wrap cuff 2* and the intracorporeal structure 5 can be completely avoided or at least significantly reduced, so that they cannot cause irreversible damage to the tissue surface of the intracorporeal structure 5.

[0033] In order to facilitate or support the folding process of the wave-mountain-shaped area tabs 12, the edge areas 10 preferably have a smaller surface substrate thickness than in the remaining area of ​​the surface substrate 1.

[0034] Typically, a polyimide film with a thickness between 15 pm and 20 pm is used to form a flat substrate 1. The edge regions 10, in contrast, have a thickness of only up to this size, which significantly increases or improves their surface elasticity and the associated deformability.

[0035] In the case of the implantable wound cuff being designed as a cuff electrode, the surface substrate 1* shown in Figure 1a, b right column is provided with electrode structures 18 in that surface substrate area which is located between the two edge areas 10 and faces the plane of the drawing, which come into direct contact with the tissue surface of a strand-like intracorporeal structure 5, in particular with the epineurium of the vagus nerve.

[0036] For manufacturing reasons and to improve the attachment of the wrap-around cuff 2* around a strand-like, intracorporeal structure 5, the surface substrate 1* has a surface extension 16 that increases the degree of wrapping of the wrap-around cuff 2*, but does not impair the function of the edge regions 10. For this reason, the surface extension 16 is narrower than the overall length 17 of the wrap-around cuff 2*.

[0037] Figure 2a shows an alternative cuff-shaped implant designed according to the invention with a film-like, flexible surface substrate 1** in the form of two straight-cylinder half-shapes 15 monolithically connected along a linear connecting region 14, on whose axially opposite circumferential side edges the edge regions 10 are formed, each delimited by a wavy edge contour line 11. Figure 2b shows the molding state in which both straight-cylinder half-shapes 15 assume the shape of a straight cylinder with a slight mutual overlap 16. Similar to the previously explained exemplary embodiment according to the invention (see the images in the right-hand column of Figure 1), in this case too the edge regions 10 are formed with a smaller surface substrate thickness compared to the remaining surface substrate region 1**.

[0038] List of reference symbols

[0039] 1 ,1*, 1** Surface substrate

[0040] 2, 2* implantable wrap cuff

[0041] 3, 3* cylinder axis

[0042] 4 Surface substrate side edge

[0043] 5 strand-like intracorporeal structure

[0044] 6 longitudinal movement

[0045] 7 peripheral edge

[0046] 8 irreversible damage, tissue peeling

[0047] 9 Length

[0048] 10 Marginal area

[0049] 11 Edge contour line

[0050] 12 Wave-mountain-shaped area flap

[0051] 13 funnel-shaped contour

[0052] 14 linear connection area

[0053] 15 straight cylinder half-mold

[0054] 16 Surface substrate process

[0055] 17 Total length of the wrap cuff

[0056] 18 electrode structures

[0057] 19 Width of the edge areas

[0058] A Amplitude of a wave-mountain-shaped area lobe

Claims

Patent claims 1. A cuff-shaped medical implant comprising a foil-like, flexible surface substrate (1*, 1**) which, due to a material-inherent shaping, independently and without the application of external force assumes the shape of a straight cylinder, in which the surface substrate (1*, 1**) provides an inner surface of the cylinder jacket which, in the implanted state, is capable of forming an extravascular or extraneuronal surface contact along an intracorporeal strand-like structure (5) in the form of an intracorporeal vessel or a nerve fiber bundle, characterized in that the foil-like, flexible surface substrate (1*, 1**) has two edge regions (10) which, in the implanted state, lie opposite one another along a cylinder axis (3*) associated with the straight cylinder shape, and in that the edge regions (10) are each delimited by a wavy edge contour line (11).

2. Cuff-shaped medical implant according to claim 1, characterized in that the film-like, flexible surface substrate (1*, 1**) can be assigned a rectangular or square basic shape.

3. Cuff-shaped medical implant according to claim 2, characterized in that the two edge regions (10) are arranged along two opposite sides of the rectangular or square basic shape.

4. Cuff-shaped medical implant according to one of claims 1 to 3, characterized in that the two edge regions (10) are each in Circumferential direction around the straight cylindrical shape of the winding sleeve (2*) once completely.

5. Cuff-shaped medical implant according to one of claims 1 to 4, characterized in that the edge contour line (11) delimiting the edge regions (10) is continuously differentiable.

6. Cuff-shaped medical implant according to claim 5, characterized in that the edge contour line (11) corresponds to a sinusoidal curved line or a sinus curve.

7. Cuff-shaped medical implant according to one of claims 1 to 6, characterized in that the film-like, flexible surface substrate (1*, 1**), with the exception of the edge regions (10), has a first film thickness D and, in the edge regions (10), a second film thickness which is smaller than the first film thickness D.

8. Cuff-shaped medical implant according to claim 7, characterized in that the second film thickness is smaller by a factor F compared to the first thickness D and that the following applies to the factor F: > F> , and that 15 pm < D < 20 pm applies to the first film thickness D.

9. Cuff-shaped medical implant according to one of claims 1 to 8, characterized in that the film-like, flexible surface substrate (1*) is designed in the manner of a wound cuff (2*), in which the film-like, flexible Surface substrate (1*) can be formed by automatically rolling up around a side edge (4) that can be assigned to the film-like, flexible surface substrate (1*).

10. Cuff-shaped medical implant according to claim 9, characterized in that the wound cuff (2*) is designed in the manner of a cuff-electrode arrangement which is designed to be attached along and around the strand-shaped intracorporeal structure (5), and in that electrode structures (18) are attached at least to the inner surface of the cylinder jacket of the wound cuff.

11. Cuff-shaped medical implant according to one of claims 1 to 8, characterized in that the film-like, flexible surface substrate (1**) has the shape of two straight cylinder half-shapes (15) monolithically connected along a linear connecting region (14), each of which is delimited by a film substrate edge oriented parallel to the cylinder axis (3*), which can both be brought into contact with each other in abutting or mutually overlapping manner to form the straight cylinder shape.

Images