DE202021106784U1 - Implantable electrodes based on 3D structured flexible circuit boards - Google Patents

Abstract

Implantable electrode line (1), having: - a distal end section (12) having a substrate (30) with a front side (31) on which at least two electrode contacts (10, 11) are arranged and with one facing away from the front side (31). Back (32), which forms an electrical insulator, - a proximal end (14) for connecting the electrode line (1) to an active implant (2), the electrode contacts (10, 11) each having an electrical conductor (3). are electrically connected to the proximal section (11), characterized in that the substrate (30) is flexible and expandable from a collapsed state to an expanded state, the substrate (30) in the expanded state having a corrugated structure with crests (33) and Wave troughs (34), wherein the two electrode contacts (10, 11) are arranged spaced apart from one another on a wave crest (33), and the back (32) of the substrate (30) in the region of the wave tä ler (34) is configured to support the substrate (30) at the implantation site.

Description

The invention relates to an implantable electrode line, in particular for spinal nerve stimulation (spinal cord stimulation, SCS for short).

• - isodiametrische Elektroden mit Durchmessern unterhalb von üblicherweise 2 mm und mehr als 4, üblicherweise 8 Elektrodenpolen zur perkutanen Implantation (Perkutan-Elektroden), oder
• - Paddelelektroden mit einem isodiametrischen Elektrodenkörper ähnlich der Perkutan-Elektrode und einem bis zu 10 mm verbreitertem distalen Ende mit üblicherweise 16 und mehr Elektrodenpolen.

In principle, there are two different designs of electrodes for the SCS, which are placed in the epidural space near the spinal cord (cf. 1 ), in fact:

• - isodiametric electrodes with diameters of usually less than 2 mm and more than 4, usually 8 electrode poles for percutaneous implantation (percutaneous electrodes), or
• - Paddle electrodes with an isodiametric electrode body similar to the percutaneous electrode and a distal end widened by up to 10 mm with usually 16 or more electrode poles.

An advantage of the percutaneous electrode is the minimally invasive method of placement; the advantage of the paddle electrode lies primarily in the better efficiency with the given performance. Such electrodes are, for example, from the US 9,867,978 B1 , WO 2009111142 A2 and US 6,205,361 B1 known.

The epidural space is approximately 2mm thick. In order for the stimulation signals to reach the spinal cord as effectively as possible, a paddle electrode thickness of 2 mm is preferred so that the electrode poles can lie close to the spinal cord membrane. The width of the paddle electrodes is usually up to 10 mm. However, electrodes with these form factors cannot be inserted percutaneously into the epidural space via conventional hollow needles.

Expensive custom-made insertion sets with an oval inner diameter are therefore necessary, which allow the percutaneous insertion of wide paddle electrodes.

Proceeding from this, the present invention is based on the object of providing an electrode lead which is improved with regard to the aforementioned problem.

This object is achieved by an electrode lead having the features of claim 1. Advantageous configurations of the invention are described below.

According to claim 1, an implantable electrode lead is disclosed which has a distal end section which has a substrate, with a front side on which at least two electrode contacts are arranged, and with a rear side facing away from the front side, which is designed entirely as an electrical insulator. Furthermore, the electrode line has a proximal end for connecting the electrode line to an active implant (the proximal section can be embodied as a plug, for example), the electrode contacts being electrically conductively connected to the proximal end via electrical conductors.

According to the invention, it is provided that the substrate is flexible and can be expanded from a collapsed state to an expanded state, with the substrate having a wavy structure with wave crests and wave troughs in the expanded state, with the two electrode contacts being arranged at a distance from one another on a wave crest, and with the backside of the substrate is configured in the region of the troughs to support the substrate at the implantation site (particularly at a vertebral arch of a person).

According to one embodiment of the invention, a minimum width of the substrate is greater than the maximum diameter of an elongate section of the electrode line that connects the proximal end to the distal section of the electrode line or to the substrate. The elongate section is also referred to as the electrode body.

The flexible substrate thus preferably has a front side, on which the at least two electrode surfaces are attached with contact to the tissue, and a back side, which consists entirely of an electrical insulator and z. B. can be supported on a vertebral body.

In other words, the invention represents a flexible design of a paddle electrode which can be brought into an isodiametric state by elastic deformation and thus enables the use of commercially available insertion instruments.

So that the electrode line according to the invention can be implanted percutaneously as well as possible, the distal section of the electrode line is preferably designed so thin and flexible that it can be guided percutaneously by folding or rolling it into a conventional insertion set and, on the other hand, has sufficient bending stiffness to ensure dimensional stability in the implanted state to ensure the necessary distance between the electrode poles. This is advantageously achieved in that the distal section z. B. is designed as a thin flexible conductor track, which is provided with a 3D wave profile. When flattened, the trace or distal portion can be either rolled or folded. Outside of the introducer, the electrode unfolds, has increased rigidity due to the wave profile and presses against the spinal cord membrane (cf. 2 ). Even if the elastic conductor is not a thermoplastic, e.g. B. in conductor tracks based on conventional polyimides (PI), the wave profile can be applied later by the film z. B. is coated with thermoplastic polyurethane by dip coating and then plastically deformed above the melting temperature.

An elastic switch is preferably located at the point at which the conductor tracks on the elastic substrate are brought together in the longitudinally extended section of the electrode body.

Proceeding from the plane of the planar substrate, the flexible substrate has a three-dimensional (3D) shape in which portions of the back surface are partially superimposed on other portions of the front surface. The flexible substrate can have a rounded corrugated structure or a zigzag corrugated structure.

Furthermore, the flexible substrate preferably has a maximum outer diameter in the folded or collapsed state which is less than or equal to the inner diameter of the insertion instrument and in the unfolded or expanded state is greater than the inner diameter of the insertion instrument.

Furthermore, according to one embodiment, it is provided that the flexible substrate consists of a thermoplastic or has a thermoplastic.

According to a further embodiment it is provided that the flexible substrate consists of a mixture of a thermoplastic and a thermoset.

Furthermore, according to one embodiment, it is provided that the flexible substrate consists of a duroplast coated with a thermoplastic.

Furthermore, according to one embodiment of the invention, it is provided that the folding of the substrate to produce the collapsed shape of the substrate takes place in the shape of an accordion. Alternatively, it is provided that the folding takes place by rolling.

Furthermore, according to one embodiment of the invention, it is provided that the substrate is unfolded via elastic elements which are located at least in part outside the plane of the electrode surfaces. The elastic elements consist z. B. made of an elastic plastic (z. B. silicone, polyurethane, etc.) and are preferably designed arcuate.

According to one embodiment, the elastic elements are designed as support beams.

According to a further embodiment, the elastic elements are of tubular design.

According to a further embodiment, provision is made for receptacles for a stylet to be located on the flexible substrate. After threading the stylet, the substrate is in a folded state. Pulling out the stylet leads to an unfolding or expansion of the substrate or paddle by the elastic elements in said expanded state.

• 1 eine Darstellung einer Anwendung einer erfindungsgemäßen Elektrodenleitung für die SCS;
• 2 eine Schnittdarstellung einer implantierten erfindungsgemäßen Elektrodenleitung;
• 3A eine schematische Draufsicht auf die Vorderseite einer Ausführungsform einer erfindungsgemäßen Elektrodenleitung;
• 3B eine geschnittene Ansicht durch ein Substrat einer Elektrodenleitung gemäß 3A im expandierten bzw. implantierten Zustand;
• 3C die Schnittansicht gemäß 3B, wobei schlauchförmige elastische Elemente zum Entfalten des Substrats der Elektrodenleitung am distalen Abschnitt der Elektrodenleitung vorgesehen sind, wobei die rechte Seite der 3C den kollabierten Zustand des Substrats zeigt;
• 3D eine Modifikation der in der 3C gezeigten Elektrodenleitung, wobei das Substrat an seinen Rändern Elemente aufweist, die Verletzungen durch zu scharfe Kanten vermeiden sollen;
• 4A die Ausführungsform der Elektrodenleitung gemäß 3A, wobei zusätzlich Aufnahmen, insbesondere Ösen, zur Aufnahme eines Mandrins vorgesehen sind, um einen kollabierten Zustand des Substrats aufrechtzuerhalten;
• 4B die Ausführungsform der Elektrodenleitung gemäß 3C, wobei schlauchförmige elastische Elemente zum Entfalten des Substrats vorgesehen sind;
• 4C die Ausführungsform der Elektrodenleitung gemäß 3C, wobei ein Mandrin durch die Aufnahmen geführt ist, um das Substrat im kollabierten Zustand zu halten, in dem die Elektrodenleitung perkutan durch eine Hohlnadel implantierbar ist, wobei sich das Substrat außerhalb der Hohlnadel durch Herausziehen des Mandrins aus den Aufnahmen in den expandierten Zustand entfaltet;
• 5A eine Abwandlung der in der 4B gezeigten Ausführungsform einer Elektrodenleitung, wobei anstelle der schlauchförmigen elastischen Elemente bogenförmige elastische Elemente vorgesehen sind; und
• 5B eine weitere Abwandlung der in der 4B gezeigten Ausführungsform einer Elektrodenleitung, wobei anstelle der schlauchförmigen elastischen Elemente elastische Elemente in Form von Stützbalken vorgesehen sind.

Exemplary embodiments of the solution according to the invention and further features and advantages of the invention are to be explained below with reference to the figures. Show it:

• 1 a representation of an application of an electrode line according to the invention for the SCS;
• 2 a sectional view of an implanted electrode line according to the invention;
• 3A a schematic plan view of the front of an embodiment of an electrode line according to the invention;
• 3B a sectional view through a substrate of an electrode line according to FIG 3A in the expanded or implanted state;
• 3C the sectional view according to 3B , wherein tubular elastic members for unfolding the substrate of the electrode line are provided at the distal portion of the electrode line, the right side of the 3C shows the collapsed state of the substrate;
• 3D a modification of that in the 3C shown electrode line, the substrate having elements at its edges that are intended to prevent injuries caused by sharp edges;
• 4A the embodiment of the electrode line according to FIG 3A , wherein additional recordings, in particular eyelets, are provided for receiving a stylet in order to maintain a collapsed state of the substrate;
• 4B the embodiment of the electrode line according to FIG 3C , being tubular elastic elements are provided for unfolding the substrate;
• 4C the embodiment of the electrode line according to FIG 3C wherein a stylet is passed through the receptacles to hold the substrate in the collapsed state in which the electrode lead can be implanted percutaneously through a hollow needle, the substrate unfolding outside of the hollow needle by withdrawing the stylet from the receptacles into the expanded state;
• 5A a modification of that in the 4B shown embodiment of an electrode line, wherein instead of the tubular elastic elements arcuate elastic elements are provided; and
• 5B another modification of the 4B shown embodiment of an electrode line, wherein instead of the tubular elastic elements elastic elements are provided in the form of support beams.

3A shows related to 3B an embodiment of an implantable electrode line 1 according to the invention, with a distal end section 12, having a substrate 30 with a front side 31, on which at least two electrode contacts 10, 11 are arranged, and with a rear side 32 facing away from the front side 31, which forms an electrical insulator. The electrode line 1 has according to 1 furthermore has a proximal end 14 for connecting the electrode line 1 to an active implant 2 , the electrode contacts 10 , 11 being electrically connected to the proximal section 14 via electrical conductors 3 .

According to the invention, it is provided that the substrate 30 is flexible and can be expanded from a collapsed state into an expanded state, with the substrate 30 having a corrugated structure with wave crests 33 and wave troughs 34 in the expanded state, with the two electrode contacts 10, 11 being spaced apart from one another on a Wave crests 33 are arranged, and wherein the rear side 32 of the substrate 30 is configured in the region of the wave troughs 34 for supporting the substrate 30 at the implantation site. This is in the 2 shown as an example. 2 shows a cross-section of a spine with spinal cord RM, epidural space E, liquor L, spinal nerve S and vertebral body W. The position of the back R and the abdomen B are also shown.

The use of a substrate 30 of an electrode line 1 in the form of a flexible printed circuit board is particularly attractive for flat electrode structures with a large number of different conductor tracks and/or electrode poles, as are used, for. B. is used in the paddle electrode for spinal nerve stimulation. The plastic substrates 30 to which the corresponding electrical conductors are applied (eg PI, LCP) generally have lower elasticity than insulation materials that are otherwise used for implantable lines (silicone, polyurethane PU). In order to nevertheless enable a flexible electrode 1, the substrates 30 are preferably manufactured in the form of very thin foils (<<1 mm). In order to avoid damage to the tissue from the film edges, these are usually subsequently covered with softer plastics, e.g. B. silicone or PU, surrounded or equipped with appropriate edge elements 35.

The most common starting material for flexible circuit boards 30 is PI. Since printed circuit boards 30 are usually manufactured in one plane and PI is a duroplast, later shaping of the PI film into a 3D profile is problematic. One possibility is to apply a thermoplastic to the PI film. Due to the thermoplastic elements on the PI film, a simplified plastic deformation is subsequently possible and also a reversible welding of different layers of the PI film.

In one embodiment, flexible circuit boards 30 with the dimensions 6×60 mm and a layer thickness of 50 μm based on polyimide (PI) are provided with a 10 μm thick polyurethane (PU) layer by dip coating.

The electrically conductive components or electrode contacts 10, 11 on the flexible substrate 30 consist z. B. from about 5 microns thick and 50 microns wide conductor tracks made of gold. According to one embodiment, a total of 2×16 electrodes 10, 11 in a total of four rows are located on the front side 31 of the substrate 30. FIG. Each of the 32 electrodes 10, 11 is connected to a conductor track 3, conductor tracks forming pairs and the pairs being short-circuited at the proximal end 36 of the paddle 30 (cf. 3A) .

At the proximal end 36 of the paddle or substrate 30 is preferably a flat-shaped extension 37 with a total of 16 metallic contact surfaces 38, to the z. B. cable-like leads z. B. be welded. After contacting the leads, the boom 37 can either be folded or rolled up and z. B. be inserted into a catheter that holds the boom in a folded or rolled condition. Said wave profile of the substrate 30 can, for. B. be implemented in the following manner: In a heated to 190 ° C metallic fit with z. B. a wave profile that corresponds to a sine wave with 1 mm amplitude and 4 mm period length, the PU-coated PI circuit boards are inserted. Depending on The amplitude of the waves and the distance between the wave crests 33 can increase the flexural rigidity by several orders of magnitude compared to a non-corrugated film. An increase by a factor of 50 was measured for a sample with a thickness of 0.25 µm, an amplitude of 1 mm and a period length of 4 mm. In simulations, factors of up to 150 are expected for similar geometries. The amplitude of the wave profile should preferably be at least 0.25 mm up to a maximum of 5 mm, preferably up to a maximum of 1 mm. The period length should preferably be between 0.2 mm and a maximum of 5 mm, preferably a maximum of 2 mm.

The electrodes 10, 11 are located near the crest or crest 33 of the wave profile, with the gap between the electrode pairs 10, 11 preferably being located exactly on the crest 33 (cf. 3B) .

This arrangement of the electrically conductive surfaces 10, 11 allows the film 30 to be folded along the crests 33 without subjecting the metallization to additional mechanical loads. In the folded state, the paddle 30 thus fits into standard epidural cannulas (e.g. with an inner diameter of ~2 mm).

Additional elastic elements 40, e.g. B. in the form of elastic plastic hoses, z. B. made of silicone, which are arranged on the back 32 of the substrate 30 between the troughs 34. The elements 40 can e.g. B. have an outer diameter in the range of 1 mm to 1.5 mm (cf. 3C ).

Attached to the substrate edges z. B. curved hose sections 35 can be used to avoid possible injuries caused by sharp edges (cf. 3D ).

Furthermore, according to 4A until 4C on the flexible substrate 30 receptacles 50 for a stylet 60 are provided. After threading in the stylet 60, the substrate 30 is in the collapsed or folded state (cf. 4C ). Pulling out the stylet 60 leads to the substrate 30 or paddle being unfolded by the elastic elements 40 ( 4A and 4B) .

Furthermore, as an alternative, the elastic elements 40 can be used as arc-shaped elastic elements 41 (cf. 5A) or as a support beam 42 (cf. 5B) be trained.

The invention advantageously allows the implantation and explantation of paddle-like electrode lines 1 using conventional instruments. This lowers the manufacturing costs and makes it easier to automate.

QUOTES INCLUDED IN DESCRIPTION

This list of the documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US9867978B1 [0003]
• WO 2009111142 A2 [0003]
• US6205361B1 [0003]

Claims (1)

Implantable electrode line (1), having: - a distal end section (12) having a substrate (30) with a front side (31) on which at least two electrode contacts (10, 11) are arranged and with one facing away from the front side (31). Back (32), which forms an electrical insulator, - a proximal end (14) for connecting the electrode line (1) to an active implant (2), the electrode contacts (10, 11) each having an electrical conductor (3). are electrically connected to the proximal portion (11), characterized in that the substrate (30) is flexible and expandable from a collapsed state to an expanded state, the substrate (30) in the expanded state having a corrugated structure with crests (33) and Wave troughs (34), wherein the two electrode contacts (10, 11) are arranged spaced apart from each other on a wave crest (33), and wherein the back (32) of the substrate (30) in the region of the wave valleys (34) is configured to support the substrate (30) at the implantation site.

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