Patent ID: 12246182

DETAILED DESCRIPTION

In the following detailed description, numerous non-limiting specific details are given to assist in understanding this disclosure.

FIG.1Adepicts an implantable restraint100comprising:

an elongated substrate300, disposed along a longitudinal axis600, the substrate having a first302and second303surface disposed along substantially parallel transverse planes600,700. As depicted, the first surface302is the visible top surface, lying in the plane comprising the longitudinal axis600and a first transverse axis700—the first transverse axis700is substantially perpendicular to the longitudinal axis700. As depicted, this is substantially parallel to the plane of the drawing (the surface of the paper). The substrate300has a thickness or extent along a second transverse axis750—this second transverse axis750is substantially perpendicular to both the longitudinal axis600and the first transverse axis700—it is substantially perpendicular to the plane of the drawing as depicted.

As the substrate300may be relatively thin with a degree of flexibility, the degree to which the transverse planes600,700are parallel may be determined by positioning the substrate300on a substantially flat service.

The substrate300may have any suitable cross-section profile. Having the surfaces302,303/transverse planes600,700substantially parallel is not essential, but it is preferred as it may simplify the predetermination of the thresholds explained below for many embodiments.

To clarify the different views of the implantable restraint, the axes are given nominal directions:the longitudinal axis600extends from the proximal end of the restraint, depicted at the bottom of the page, to the distal end, depicted at the top of the page;the first transverse axis700extends from left to right as depicted on the page, when the first surface302is viewed from above; andthe second transverse axis750extends out of the pages as depicted.

The second surface303is not depicted inFIG.1A, but lies at a lower position along the second transverse axis750, and is also substantially parallel to the plane of the drawing.

As the substrate300may be relatively thin with a degree of flexibility, the degree to which the surfaces302,303are parallel may be determined by positioning the substrate300on a substantially flat service.

The substrate300further comprises:

an opening500, substantially extending through the substrate300, along the second transverse axis750, between the first302and second303surfaces. This opening is configured to receive in-growth of human or animal tissue after implantation such that a tissue anchor may form. More than one such opening500may be used to anchor the restraint100. The opening500may also be an aperture—the form and dimensions of the opening500are predetermined to provide a certain degree of fixation at a tissue location where the implant100is to be restrained. After implantation, the human or animal body will naturally generate tissue at the implantation site—this will enter the opening500, creating a strong attachment to the restraint100at the location of the opening500. This may also be called bio-connecting, tissue locking or tissue in-growth.

In general, indentations may be used instead of holes, or in combination with holes. In addition, the thickness (extent along the second transverse axis750) may also be modified, as depicted inFIG.8(see below). The reduction in thickness may be comprised in the first surface302, in the second surface303, or in both.

The substrate300also comprises:

a pair of protrusions401,404, disposed between the opening500and a distal edge of the substrate300, the protrusions401,404being configured to provide a first resistance against the tissue anchor to a longitudinal force610applied to a proximal section of the substrate300. As depicted, the longitudinal force610is applied in a negative direction along the longitudinal axis600, which is downwards. It is this first resistance which provides a degree of restraint against migration due to a longitudinal force. The transverse edges along the first transverse axis700provide a degree of restraint against migration due to a transverse force.

The pair of protrusions401,404are further configured to separate by a distance approximately equal to a transverse extent700of the tissue anchor when the longitudinal force610exceeds a first predetermined threshold, such that the pair of protrusions401,404moves past the tissue anchor in the direction of the longitudinal force610.

One of the insights on which the invention is based is that the natural growth of tissue which occurs after implantation may be utilized to secure the implantable device at the implantation site. This natural growth is currently considered an annoyance as it makes explantation more difficult—in some cases surgery may even be required to remove implantable electrode leads.

By providing one or more openings500extending through the substrate300, the sites at which tissue growth occurs are at least partially predetermined, and preferably predetermined to a high degree. The extent of the one or more openings500along the transverse axis700and along the longitudinal axis600are factors which influence the degree of tissue growth which may occur, and also influence the degree by which the restraint100is fixed in the section proximate the opening500.

FIG.1Bshows a transverse cross section of the implantable restraint100depicted inFIG.1A. It is depicted in the plane comprising the longitudinal axis600and the second transverse axis750, with the longitudinal axis600depicted from left to right, and the second transverse axis750is depicted from bottom to top. Both the first302and second303surfaces are depicted as respectively an upper and lower surface. The opening500substantially extends through the substrate300between the first302and second surface303.

In this embodiment100, there is a distal opening410between the protrusions401,404, substantially extending through the substrate—in other words, there is a separation distance between the pair of protrusions401,404across the transverse extent700of the distal opening410. In terms of the invention, the distal opening410provides substantially zero resistance against an increase of the separation distance of the pair of protrusions401,404. Depending on the transverse700and longitudinal600extent of the distal opening410, some tissue in-growth may occur in the distal opening410providing a relatively small resistance against an increase in the protrusion pair401,404separation distance.

As described below, indentations may be used instead of substantially extending through. In addition, the thickness (extent along the second transverse axis750) may also be modified, as depicted inFIG.8(see below). The reduction in thickness may be comprised in the first surface302, in the second surface303, or in both

The restraint100is configured and arranged such that when a longitudinal force610above a predetermined threshold is applied to a proximal end, the pair of protrusions401,404separate by a distance approximately equal to a transverse extent700of the tissue anchor, such that the pair of protrusions40,404moves past the tissue anchor in the direction of the longitudinal force610.

In general, this predetermined threshold may include one or more of the following contributions:a) a resistance of the distal edge of the opening500against any tissue anchor which has in-grown in the opening500after implantation;b) a resistance of the protrusion pair401,404against any tissue anchor in the opening500due to the physical form and properties of the protrusions401,404;c) a resistance against an increase in the separation distance of the pair of protrusions401,404due to any further tissue anchor which has in-grown in the distal opening410after implantation;d) a resistance against an increase in the separation distance of the pair of protrusions401,404due to the physical form and properties of the protrusions401,404; ande) a resistance against an increase in the separation distance of the pair of protrusions401,404due to the physical form and properties of the region between the pair of protrusions401,404. As mentioned above, in this embodiment of the restraint100, this resistance is substantially zero due to the region being a distal opening410. In the other embodiments discussed below, this region contributes a more than zero resistance.

a) and b) are referred to as anchor resistance; and c), d) and e) are referred to as separation resistance. Both types of resistance must be overcome before the implantable restraint can be explanted

The resistance of the protrusion pair401,404against any tissue anchor in the opening500may be determined by using a particular physical form and/or changing/selecting the physical (and material) properties of the protrusions401,404.

One of the basic parameters to determine the anchor resistance are the physical dimensions of the protrusion pair401,404—the thickness (extent along second transverse axis750), the width (extent along the longitudinal axis600), the protrusion “arm” length (extent along the first transverse axis700) and the curvature of the “arms”. In addition, the materials used to form the protrusions401,404also influence the anchor resistance due to parameters such as:

Young's Modulus of the material

the thickness of the individual material layers

the number of layers from which the material stack is composed

any metal tracks that are included into the material stack, which increases the stiffness of the protrusions.

For example, the elongated substrate300may comprise an elastomeric distal end composed of silicone rubber, or another biocompatible, durable polymer such as siloxane polymers, polydimethylsiloxanes, polyurethane, polyether urethane, polyetherurethane urea, polyesterurethane, polyamide, polycarbonate, polyester, polypropylene, polyethylene, polystyrene, polyvinyl chloride, polytetrafluoroethylene, polysulfone, cellulose acetate, polymethylmethacrylate, polyethylene, and polyvinylacetate. The pair of protrusions401,404may comprise one or more compounds and/or substances comprised in the substrate300, or something different. Suitable examples of polymers, including LCP, are described in “Polymers for Neural Implants”, Hassler, Boretius, Stieglitz, Journal of Polymer Science: Part B Polymer Physics, 2011, 49, 18-33 (DOI 10.1002/polb.22169), In particular, Table1is included here as reference, depicting the properties of Polyimide (UBE U-Varnish-S), Parylene C (PCS Parylene C), PDMS (NuSil MED-1000), SU-8 (MicroChem SU-8 2000 & 3000 Series), and LCP (Vectra MT1300).

Flexible substrates300are also preferred as they follow the contours of the underlying anatomical features very closely. Very thin substrates300have the additional advantage that they have increased flexibility.

Preferably, the flexible substrate300comprises a Liquid Crystal Polymer (LCP), Parylene and/or a Polyimide. Liquid Crystal Polymers (LCP) are chemically and biologically stable thermoplastic polymers which allow for hermetic sensor modules having a small size and low moisture penetration.

Advantageously, LCP may be thermoformed allowing complex shapes to be provided. Very thin and very flat sections of LCP may be provided, allowing a wide range of protrusion pair401,404sizes and shapes to be provided. For fine tuning, a suitable laser may also be used for cutting and the distal end may be flattened to a higher degree than the rest of the substrate. For example, LCP substrates300with thicknesses (extent along the second transverse axis750) in the range 50 microns (μm) to 700 microns (μm) may be used, preferably 100 microns (μm) to 300 microns (μm). For example, values of 150 μm (micron), 100 μm, 50 μm, or 25 μm may be provided. Similarly, protrusion widths (extent along the longitudinal axis600) of 150 μm, 100 μm, 50 μm or 25 μm may be provided using LCP, for example.

At room temperature, thin LCP films have mechanical properties similar to steel. This is important as implantable substrates300must be strong enough to be implanted, strong enough to be removed (explanted) and strong enough to follow any movement of the anatomical feature and/or structure against which it is implanted.

LCP belongs to the polymer materials with the lowest permeability for gases and water. LCP can be bonded to itself, allowing multilayer constructions with a homogenous structure.

In contrast to LCP, Polyimides are thermoset polymers, which require adhesives for the construction of multilayer substrates. Polyimides are thermoset polymer material with high temperature and flexural endurance.

LCP may be used, for example, to provide a substrate having multilayers (not depicted)—in other words, several layers of 25 μm (micron) thickness. Electrical interconnect layers may also be provided by metallization using techniques from the PCB industry, such as metallization with a bio-compatible metal such as gold or platinum. Electro-plating may be used. These electrical interconnect layers may be used to provide electrical energy to any electrodes.

For example, LCP materials are available from Zeus Industrial Products (www.zeosinc.com/lp/technical-papers/lpc-introduction-to-liquid-crystal-polymers), Typical physical properties from Zeus are:

ASTMLCPPHYSICALDensity (g/cc)D7921.40-1.51Water Absorption (%)D5700.003-0.006Refraction IndexN/AMECHANICALTensile/Young's Modulus (MPa)D63810,000-37,900Tensile Stress/Strength (MPa)D63844.8 to 100Elongation at Break (%)D6380.40-5.8Flexural Modulus (MPa)D7907,580-19,300Flexural Strength (MPa)D79068.6 to 159ELECTRICALVolume Resistivity (Ω-cm)D2574 × 1014Relative PermittivityIEC 602504.39Dissipation FactorD1491.0−3to 0.035THERMALLoad (° C.)D648232-293Maximum Service Temp, Air (° C.)150Minimum Service Temp, Air (° C.)−50Melt Temp (° C.)280-330Coefficient of Thermal Expansion,D6960-0.05linear 20° (μm/m-° C.)

As a longitudinal force610is applied, the protrusion pair401,404provide a degree of anchor resistance. When the longitudinal force610exceeds a first predetermined threshold, the arms of the protrusions401,404start to bend and/or twist, such that they open to a sufficient degree that the arms of the protrusions401,404pass around the tissue anchor as the implantable restraint100is explanted.

The force to be applied to remove the restraint100may predetermined to be in the range 0.1 Newton (N) to 10 N. Alternatively, the force may predetermined to be in the range 0.5 N to 2N. Alternatively, the force may predetermined to be in approximately 1 N.

The pair of protrusions401,404may substantially face each other, providing for symmetrical protrusions and/or a symmetrical opening500which may provide a more predictable force threshold for explantation.

Preferably, a low aspect ratio is used for the elongated substrate to reduce the chance of implantation problems—for example a ratio of height (thickness or extent along the second transverse axis750) to width (extent along the first transverse axis700) of less than 10, such as 0.3 mm high and 10 mm wide(=ratio 1:33).

One of the insights on which the invention is based is that such low aspect ratio substrates allow openings500to be provided which substantially extend through the entire thickness, promoting tissue in-growth at these locations.

In addition, the implantable restraint100uses fixing protrusions in approximately the same plane as the substrate300. This reduces the likelihood that the restraints will be felt by the patient through the skin, and the possibility that the protrusions would pierce the skin is greatly reduced. In addition, the restraint100uses protrusions rigidly attached and/or integrated into the substrate300, preferably comprising the same material(s) as the substrate300. This reduces the need for additional anchors and/or sutures.

Alternatively a substrate may be used with a substantially circular (which includes a circle, a flattened circle, a stadium, an oval and an ellipse) transverse cross-section—this may also be described as tubular or cylindrical.

Although only one opening500is depicted, the skilled person will realize that the restraint100may comprise a plurality of openings500and a plurality of corresponding protrusions401,404—the implantable restraint100may be fixed at a plurality of points along the length of the substrate300.

In general, each opening500is substantially predetermined to secure the implantable device101(medical lead) at the implantation site. Parameters that determine the degree of positional security include:the position of the one or more openings500. In other words, the environment proximate the opening500after implantation may influence the extent and rate of tissue growth.the number and distribution of the one or more openings500. More openings provide, in general, more locations for tissue to grow. The distribution may determine the degree to which a section of the restraint100is fixed. For example, one or more openings500with a small pitch (close together) may be used proximate any stimulation electrodes because these generally require a higher degree of positional security. In many case, stimulating electrodes are disposed proximate the distal end (a preferred location for an opening500) to keep the extent of the implanted lead as short as possible.the transverse700and/or longitudinal extent600of the one or more openings500. In general, it is expected that a larger opening will provide for a higher extent of in-growth, which is expected to increase positional security.the thickness of the substrate300or distance between the first surface302and the second surface303. In general, a stronger positional security may be achieved if the tissue growth passes all the way through the substrate300. A further insight upon which the invention is based is that the emergence of newer bio-compatible substrate materials with a higher tensile strength means that thinner substrates300may be used, increasing the chance that tissue growth can pass the whole way through.the human or animal tissue against which the implantable restraint100, is implanted. The rate and extent of tissue growth may also depend on the individual patient and the implantation site.

Typically, the openings500will have a minimum extent of 1 mm, with a preferred extent along at least one axis of 5 mm. The selected dimensions depend on the rate of tissue growth to be expected at the implant location in the body.

FIG.1Cdepicts a modified implantable restraint101—it is similar to the implantable restraint100described in relation toFIGS.1A and1B, except for comprising:

a region420, disposed between the pair of protrusions401,404, configured to provide a separation resistance against an increase in the separation distance of the pair of protrusions401,404, wherein the region420is further configured to rupture when the longitudinal force610exceeds a second predetermined threshold, such that a distal opening410is disposed between the pair of protrusions401,404. In other words, the pair of protrusions401,404are connected together, and after the connection has ruptured, the pair of protrusions are no longer connected together and the restraint101then resemble the earlier depicted restraint100.

FIG.1Dshows a transverse cross section of the implantable restraint101depicted inFIG.1C. It is depicted in the plane comprising the longitudinal axis600and the second transverse axis750, with the longitudinal axis600depicted from left to right, and the second transverse axis750is depicted from bottom to top. Both the first302and second303surfaces are depicted as respectively an upper and lower surface. The opening500substantially extends through the substrate300between the first302and second surface303.

In this embodiment101, there is a region420between the protrusions401,404—in other words, there is a separation distance between the pair of protrusions401,404across the transverse extent700of the region420. In terms of the invention, the region420provides a (separation) resistance against an increase of the separation distance of the pair of protrusions401,404.

By providing one or more respective regions of configured separation resistance420, rupture points are provided allowing the restraint to be explanted by applying a suitable and, to a large extent (substantially) predetermined, longitudinal force. A further advantage is that the risk of material from the device, and in particular substrate300material, being left behind at the implantation site, is greatly reduced as the position of the separation is predetermined.

The degree of resistance during explantation is substantially determined by the dimensioning and physical properties of the one or more regions420,430of configured separation resistance, as well as the selection of a suitable material.

For example, depressions may be etched, stamped, engraved, cut, punched or melted as depicted inFIG.8. These steps may be performed during manufacturing, or later as an additional step before use. A transverse cross-section is depicted, lying in a plane comprising the first transverse axis700and the second transverse axis750. As depicted, the longitudinal axis extends positively into the plane depicted (the paper) at substantially 90 degrees. The cross-section is through the distal section of the restraint, between the opening500and the distal edge. Three examples of regions420providing a predetermined resistance to the separation of the protrusion pair401,404by substantially reducing the thickness (the extent along the second transverse axis750). The reduction in thickness may be comprised in the first surface302, in the second surface303, or in both.

Additionally or alternatively, perforations and/or serrations may be used to more accurately predetermine a position of the rupture line. These may be applied using a stamp, drill, a hot needle and/or a laser, for example.FIG.9depicts a zoomed view of the first surface302in a plane comprising the longitudinal axis600and the first transverse axis700. The holes (perforations) substantially extend through the substrate, from the first surface302to the second surface303—they are dimensioned too small to allow significant tissue in-growth.

In general, indentations may be used instead of holes, or in combination with holes. In addition, the thickness (extent along the second transverse axis750) may also be modified, as depicted inFIG.8.

Typically, with the thermoplastic polymers such as LCP, the rupture may not occur exactly along the perforations. Separation of the protrusion pair401,404will occur by forces being applied to pull the protrusions apart—each connection (the bridge between the perforations or holes) between the protrusion pair401,404must be separated before the protrusion pair401,404can be completely separated. As the forces increase and the protrusion pair401,404are separated, the cross-sections of the bridges will reduce until they are thin enough to break.

FIG.3depicts a further modified implantable restraint102—it is similar to the implantable restraint101described in relation toFIGS.1C and1D, except for:

a region430, disposed between the pair of protrusions401,404, configured to provide a separation resistance against an increase in the separation distance of the pair of protrusions401,404. However, in this example, the region430comprises substantially different materials compared to the pair of protrusions401,404.

This provides a higher degree of customization, allowing the region430and protrusions401,404to be configured in completely different ways—for example, a large difference in thickness or width—and to use materials with substantially different properties such as LCP for the protrusions401,404and silicon for the region430.

A silicon substrate may be used for the region430or, for example, an overmould may be used. Silicon has a tensile strength of approximately 10 MPa, so an area of 0.3 mm×0.3 mm would be required to rupture at 1N.

Parameters that determine the force required for the region420,430to separate, thus separating the pair of protrusions401,404, include:the transverse700and/or longitudinal extent600of the region420,430.the thickness of the substrate300, or distance between the first surface302and the second surface303.the materials comprised in the substrate300within the region420,430and their physical properties. The separation resistance may be increased by including different materials with different tensile strengths, such as a reinforcement filament, a metal wire and/or LCP strip, or any combination thereof.the presence of interconnecting tracks and/or interconnection layers within the region420,430the presence of one or more reinforcement coatings, such as a sputtered layer of chrome.the shape of an edge immediately proximate the one or more openings500the presence or shape of one or more corners in of an edge immediately proximate the one or more openings500the presence of one or more indentations in the first surface302and/or second surface303as depicted inFIG.8andFIG.9.

As this region420,430is configured to separate, it is usually a region of reduced resistance compared to the pair of protrusions401,404.

Typically, the longitudinal extent600of the region420,430may be in the range 0.5 mm to 1 mm.

It may be advantageous if the force to be applied to remove the restraint100,101,102is in the range 0.5 N to 2N. Additionally, the force to be applied may be approximately 1 N.

The tensile strength of LCP is typically in the range of 100-200 MPa (N/mm2).

The area (in mm2) of the longitudinal cross-section through the region420,430with the configured separation resistance is equal to the Force (N)/Tensile (MPa).

With a tensile strength of 100, the area configured to rupture with a force of 1N is 0.1 mm×0.1 mm. This may be effectively achieved using a high degree of perforation.

For restraints101,102where a region420,430of configured separation resistance is provided, this may be configured and arranged to substantially predetermine the highest force threshold that must be exceeded before explantation is possible. In other words, the anchor resistance due to the form and properties of the pair of protrusions may be configured and arranged to be substantially less—its contribution may be much lower (in some case insignificant) when compared to the embodiment ofFIGS.1A and1B, where this anchor resistance is the major contributor to the force threshold for explantation.

If a conductive wire is used, the device may also be configured and arranged to pass sufficient current through it to melt it, similar to the way that an electrical fuse works.

FIGS.2A and2Bdepict a first example of an implantable stimulation device201(or lead) comprising one or more implantable restraints100,101,102depicted above.

FIG.2Adepicts the implantable stimulation device201comprising:

an elongated substrate310, disposed along a longitudinal axis600, the substrate having a first312and second313surface disposed along substantially parallel transverse planes600,700. As depicted, the first surface312is the visible top surface, lying in the plane comprising the longitudinal axis600and a first transverse axis700—the first transverse axis700is substantially perpendicular to the longitudinal axis700. As depicted, this is substantially parallel to the plane of the drawing (the surface of the paper). The substrate310has a thickness or extent along a second transverse axis750—this second transverse axis750is substantially perpendicular to both the longitudinal axis600and the first transverse axis700—it is substantially perpendicular to the plane of the drawing as depicted.

As the substrate310may be relatively thin with a degree of flexibility, the degree to which the transverse planes600,700and surfaces312,313are parallel may be determined by positioning the substrate310on a substantially flat service.

FIG.2Bshows a transverse cross section of the implantable stimulation device depicted inFIG.2A. It is depicted in the plane comprising the longitudinal axis600and the second transverse axis750, with the longitudinal axis600depicted from left to right, and the second transverse axis750is depicted from bottom to top. Both the first312and second313surfaces are depicted as respectively an upper and lower surface. The opening500substantially extends through the substrate310between the first312and second surface313.

In this embodiment201, there is a region420between the protrusions401,404—in other words, there is a separation distance between the pair of protrusions401,404across the transverse extent700of the region420. In terms of the invention, the region420provides a (separation) resistance against an increase of the separation distance of the pair of protrusions401,404.

This implantable stimulation device201is depicted comprising an implantable restraint101at its distal end. Alternatively or additionally, any of the restraint variants mentioned in the description may be used, including restraints100and102.

The implantable stimulation device201further comprises:one or more stimulating electrodes200, configured to transmit energy to human or animal tissue during use (after implantation)—this may be electrical energy or another type of energy using an appropriate transducer, such as ultrasound. These may be any suitable electrode known in the art for this purpose. They are depicted in a 1-dimensional array. However, 2-d and 3-d arrays may also be used, depending on factors such as the type of tissue to be stimulated, the dimensions of the substrate310and the amount of room available at the implantation site. In general, the number, dimensions and/or spacings of the stimulating electrodes200may be selected and optimized depending on the treatment—for example, each electrode200may provide a separate stimulation effect, a similar stimulation effect or a selection may be made of one or two electrodes200proximate the tissues where the effect is to be created. The electrodes200may comprise a conductive material such as platinum, iridium, and/or platinum/iridium alloys and/or oxides.one or more electrical interconnections250, configured to provide the one or more electrodes200with electrical energy. Additionally or alternatively, the substrate310may be a multilayer, comprising one or more electrical interconnection layers to provide the one or more electrodes200with electrical energy. In use, the electrical interconnections are connected to a source of electrical power (not depicted). If an LCP multilayer is used, the thickness (extent of the substrate310along the second transverse axis750or the perpendicular distance between the first surface312and the second surface) may be typically approximately 150 μm (micron) in the sections with no electrodes200or interconnections, 250 μm in the sections with an electrode200, and 180 μm in the sections with an electrical interconnection250. If multilayers are used, electrical interconnection layers of 25 μm (micron) may be used, for example.

The distal end of the implantable stimulation device101may be configured for implantation to be implanted at a different distance below the skin (different depths) or in a bodily cavity.

Although depicted as a substrate300with a substantially rectangular cross-section, substrates (and leads) having other cross-sections, such as square, trapezoidal may be used. The cross-section shape and/or dimensions may also vary along the longitudinal axis600.

The device201may be implanted by first creating a tunnel and/or using an implantation tool.

The stimulation device201(comprising a restraint101) is configured and arranged such that when a longitudinal force610above a predetermined threshold is applied to a proximal end, the pair of protrusions401,404separate by a distance approximately equal to a transverse extent700of the tissue anchor, such that the pair of protrusions401,404moves past the tissue anchor in the direction of the longitudinal force610.

Additionally, one or more additional openings590may also be provided—these are not each associated with a respective region of configured separation resistance. They are additional openings590which allow a small (minimum) amount of tissue growth, such that the device is secured. However, they should not be dimensioned too large as this may complicate explantation. These additional openings590may be used with any of the embodiments described herein. Preferably, the additional openings590should be have at least one extent along an axis in the range 1 to 3 mm, preferably 2 mm.

FIGS.4A and4Bdepict a second example of an improved implantable stimulation device202—this example comprises a plurality of implantable restraints according to the invention.

FIG.4Ashows a view of the outer surface312, which lies in a plane comprising the first transverse axis700and the first longitudinal axis600. This is part of the main elongated substrate310, which comprises an implantable restraint101at its distal end.

Additional restraints101are provided at the distal ends of additional substrates, disposed along: a second longitudinal axis640, a third longitudinal axis660, a fourth longitudinal axis670, and a fifth longitudinal axis680.

The first transverse axis700is substantially perpendicular to the longitudinal axes600,640,660,670,680.

FIG.4Bshows a longitudinal cross section in the plane comprising the longitudinal axis600and the second transverse axis750, wherein the second transverse axis750is substantially perpendicular to the longitudinal axis600, and the second transverse axis750is substantially perpendicular to the first transverse axis700.

The device202comprises a plurality of implantable restraints101at a plurality of distal ends. Alternatively or additionally, any of the restraint variants mentioned in the description may be used, including restraints100and102, in any orientation.

They may comprise the same (or similar) materials or be differently configured and arranged to different degrees. They may be integrated with the (main) substrate310and/or attached using adhesive, heat-welding and similar.

The implantable device202further comprises:

electrodes and interconnections as depicted inFIG.2AandFIG.2B—for clarity, they have not been depicted. One or more of the restraints101depicted may comprise one or more electrodes, or be solely configured for fixation.

The stimulation device202(comprising a plurality of restraints101) may be configured and arranged such that when a longitudinal force610above a predetermined threshold is applied to a proximal end, each of the pair of protrusions separate by a distance approximately equal to a transverse extent700of the corresponding tissue anchor, such that the pair of protrusions401,404moves past the tissue anchor in the direction of the longitudinal force610.

For each of these restraints101, it may be predetermined that the regions of configured separation resistance rupture at the same, similar or even different force thresholds610. When more than one restraint101is provided, it may also be advantageous to configure and arrange them such that they rupture by different forces—in this way, explantation may be greatly simplified, and just require a gradually increasing force to be applied for removal.

FIG.5andFIG.6depict examples of nerves that may be stimulated using a suitably configured improved implantable device201,202to provide neurostimulation to treat, for example, headaches or primary headaches. The ability to secure the lead without large protrusions and/or barbs means that the comfort to the user of the implantable device201,202is increased.

FIG.5depicts the left supraorbital nerve910and right supraorbital nerve920which may be electrically stimulated using a suitably configured device.FIG.6depicts the left greater occipital nerve930and right greater occipital nerve940which may also be electrically stimulated using a suitably configured device.

Depending on the size of the region to be stimulated and the dimensions of the part of the device to be implanted, a suitable location is determined to provide the electrical stimulation required for the treatment. Approximate implant locations for the distal part of the stimulation device comprising stimulation electrodes220are depicted as regions:location810for left supraorbital stimulation and location820for right supraorbital stimulation for treating chronic headache such as migraine and cluster.location830for left occipital stimulation and location840for right occipital stimulation for treating chronic headache such as migraine, cluster, and occipital neuralgia.

In many cases, these will be the approximate locations810,820,830,840for the implantable electrode unit201,202.

For each implant location,810,820,830,840a separate stimulation device201,202may be used. Where implant locations810,820,830,840are close together, or even overlapping a single stimulation device201,202may be configured to stimulate at more than one implant location810,820,830,840.

A plurality of stimulation devices201,202may be operated separately, simultaneously, sequentially or any combination thereof to provide the required treatment.

FIG.7depict further examples of nerves that may be stimulated using a suitably configured improved implantable device201,202to provide neurostimulation to treat other conditions. As inFIGS.5and6, the ability to be secured without large protrusions and/or barbs in these locations means that the comfort to the user of the implantable device201,202is increased. The locations depicted inFIG.5andFIG.6(810,820,830,840) are also depicted inFIG.7.

Depending on the size of the region to be stimulated and the dimensions of the part of the device to be implanted, a suitable location is determined to provide the electrical stimulation required for the treatment. Approximate implant locations for the part of the stimulation device comprising stimulation electrodes are depicted as regions:

location810for cortical stimulation for treating epilepsy;

location850for deep brain stimulation for tremor control treatment in Parkinson's disease patients; treating dystonia, obesity, essential tremor, depression, epilepsy, obsessive compulsive disorder, Alzheimer's, anxiety, bulimia, tinnitus, traumatic brain injury, Tourette's, sleep disorders, autism, bipolar; and stroke recovery

location860for vagus nerve stimulation for treating epilepsy, depression, anxiety, bulimia, obesity, tinnitus, obsessive compulsive disorder and heart failure;

location860for carotid artery or carotid sinus stimulation for treating hypertension;

location860for hypoglossal & phrenic nerve stimulation for treating sleep apnea;

location865for cerebral spinal cord stimulation for treating chronic neck pain;

location870for peripheral nerve stimulation for treating limb pain, migraines, extremity pain;

location875for spinal cord stimulation for treating chronic lower back pain, angina, asthma, pain in general;

location880for gastric stimulation for treatment of obesity, bulimia, interstitial cystitis;

location885for sacral & pudendal nerve stimulation for treatment of interstitial cystitis;

location885for sacral nerve stimulation for treatment of urinary incontinence, fecal incontinence;

location890for sacral neuromodulation for bladder control treatment; and

location895for fibular nerve stimulation for treating gait or footdrop.

Other condition that may be treated include gastro-esophageal reflux disease and inflammatory diseases.

Although the examples above describe the use of the embodiments of the invention in the lead for a stimulation advice, the embodiments may be used for any implantable structure that needs to be temporarily fixed well, such as an anti-conception implant.

The descriptions thereof herein should not be understood to prescribe a fixed order of performing the method steps described therein. Rather the method steps may be performed in any order that is practicable. Similarly, the examples are used to explain the algorithm, and are not intended to represent the only implementations of these algorithms—the person skilled in the art will be able to conceive many different ways to achieve the same functionality as provided by the embodiments described herein.

Although the present invention has been described in connection with specific exemplary embodiments, it should be understood that various changes, substitutions, and alterations apparent to those skilled in the art can be made to the disclosed embodiments without departing from the spirit and scope of the invention as set forth in the appended claims.

REFERENCE NUMBERS USED IN DRAWINGS

100a first implantable restraint101a second implantable restraint102a third implantable restraint200one or more stimulating electrodes201a first implantable stimulation device (lead)202a second implantable stimulation device (lead)250one or more electrical interconnections300an elongated substrate (for restraint)302a first substantially planar surface (for restraint)303a second substantially planar surface (for restraint)310an elongated substrate (for stimulation device)312a first substantially planar surface (for stimulation device)313a second substantially planar surface (for stimulation device)401a first protrusion404a second protrusion410a distal opening420a region configured to provide a separation resistance430a region configured to provide a separation resistance500an opening590an additional opening600a (first) longitudinal axis610a substantially predetermined longitudinal force640a second longitudinal axis660a third longitudinal axis670a fourth longitudinal axis680a fifth longitudinal axis700a first transverse axis750a second transverse axis810location for left supraorbital nerve or cortical stimulation820location for right supraorbital stimulation830location for left occipital nerve stimulation840location for right occipital nerve stimulation850location for deep brain stimulation860location for vagus nerve, carotid artery, carotid sinus, phrenic nerve orhypoglossal stimulation865location for cerebral spinal cord stimulation870location for peripheral nerve stimulation875location for spinal cord stimulation880location for gastric stimulation885location for sacral & pudendal nerve stimulation890location for sacral neuromodulation895location for fibular nerve stimulation930left greater occipital nerve940right greater occipital nerve