System and method for interfascicular insertion of flexible electrodes

Abstract

A flexible electrode can be implanted between fascicles within a nerve with the following Minimally Invasive Interfascicular Nerve Stimulation (MiiNS) systems and methods. A neuroretractor can be positioned in a position that captures at least a portion of the nerve to provide stabilization and brace the nerve, wherein the neuroretractor comprises a plurality of flexible bristles configured to ensnare a deep surface of an epineurium of the portion of the nerve. Then the flexible electrode can be delivered into the portion of the nerve with a spring-loaded inserter wile pressure is simultaneously applied to another portion of the nerve opposite the neuroretractor with a soft pressure applicator to increase friction between the flexible electrode and the nerve. The flexible electrode can be left inserted in the nerve by releasing pressure on a spring of the spring-loaded inserter to pull back a microcannula used to place the flexible electrode.

Description

NONPROVISIONAL APPLICATIONSYSTEM AND METHOD FOR INTERFASCICULAR INSERTION OF FLEXIBLE ELECTRODESCross Reference to Related Applications

[0001] This application claims the benefit of U.S. Provisional Application Serial No. 63 / 702,771 , filed 3 October 2024, entitled “MINIMALLY INVASIVE INTERFASCICULAR NERVE STIMULATION (MIINS) INSERTION SYSTEM”. The entirety of this application is incorporated by reference for all purposes.Technical Field

[0002] This disclosure relates generally to peripheral nerve stimulation (PNS) and more specifically to a minimally invasive interfascicular nerve stimulation (MiiNS) system and method for improved insertion of one or more flexible electrodes into a nerve between the fascicles of the nerve (also referred to as “interfascicular insertion”) for highly selective PNS.Background

[0003] Peripheral nerve stimulation (PNS) is a medical treatment in which a signal (e.g., an electrical signal) is applied to at least a portion of a peripheral nerve via at least one electrode to treat a condition. Today, PNS is used to treat chronic neuropathic pain through easily-implanted electrodes only needing to be positioned near and / or in contact with one or more peripheral nerves generally because strong selectivity of fibers within the peripheral nerves is not required to treat the chronic neuropathic pain. However, applications for PNS are continually expanding with new nerve targets and pathologies for treatment regularly emerging (e.g., sensory restoration following amputation, autonomic therapies, etc.), which require higher selectivity than current uses (e.g., requiring the electrical signal to be delivered to specific axonal populations in a nerve rather than to the nerve generally). Higher selectivity stimulation currently requires more invasive implant procedures that can cause structural or functional disruption of neural tissue.Summary

[0004] Described herein is a minimally invasive interfascicular nerve stimulation (MiiNS) system and method for implanting one or more flexible electrodes into a nerve interfascicularly (e.g., between the fascicles and without piercing the perineurium of the fascicles) for highly selective stimulation with minimal invasiveness. A specialized kit of instruments (including at least a neuroretractor, soft pressure applicator, and spring-loaded inserter) can be utilized for interfascicular insertion of the flexible electrodes into the nerve.

[0005] In an aspect, the present disclosure can include a method for implanting a flexible electrode between fascicles within a nerve. A neuroretractor can be positioned in a position that captures at least a portion of the nerve to provide stabilization, wherein the neuroretractor comprises a plurality of flexible bristles configured to ensnare a deep surface of an epineurium of the portion of the nerve. The flexible electrode can be delivered into the portion of the nerve with a spring- loaded inserter. Pressure can be applied to another portion of the nerve opposite the neuroretractor with a soft pressure applicator to increase friction between the flexible electrode and the nerve, wherein the nerve is braced by the neuroretractor. Then, pressure on a spring of the spring-loaded inserter can be released (e.g., to retract a micro-cannula used to insert the flexible electrode) such that the flexible electrode is configured to remain positioned in the nerve between the fascicles.

[0006] In another aspect, the present disclosure can include a kit for implanting a flexible electrode between fascicles within a nerve. The kit can include at least a neuroretractor, a spring-loaded inserter, and a soft pressure applicator. The neuroretractor can include flexible bristles configured to ensnare a deep surface of an epineurium of a portion of a nerve and provide an oppositional force during insertion. The spring-loaded inserter can be configured to deliver the flexible electrode into the portion of the nerve by removing the flexible electrode from a micro-cannula loaded into an end of the spring-loaded inserter and retracting the micro-cannula while leaving the flexible electrode in the portion of the nerve. The soft pressure applicator can be configured to apply pressure to another portion of the nerve opposite the neuroretractor to increase friction between the flexible electrode and the nerve when the nerve is braced by the neuroretractor.Brief Description of the Drawings

[0007] The foregoing and other features of the present disclosure will become apparent to those skilled in the art to which the present disclosure relates upon reading the following description with reference to the accompanying drawings, in which:

[0008] FIG. 1 is a block diagram of a minimally invasive interfascicular nerve stimulation (MiiNS) insertion system;

[0009] FIG. 2 is an illustration of an example use of the MiiNS system of FIG. 1 ;

[0010] FIGS. 3-6 show generic and specific examples of the components of theMiiNS system of FIG. 1 ;

[0011] FIGS. 7 and 8 are process flow diagrams showing methods for minimally invasively inserting one or more flexible electrodes into the interfascicular space of a nerve;

[0012] FIGS. 9 and 10 are illustrations of experimental methods and results; and

[0013] FIGS. 11 - 16 are graphical and pictorial representations of experimental results.Detailed DescriptionI. Definitions

[0014] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present disclosure pertains.

[0015] As used herein, the singular forms “a,” “an,” and “the” can also include the plural forms, unless the context clearly indicates otherwise.

[0016] As used herein, the terms “comprises” and / or “comprising,” can specify the presence of stated features, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, steps, operations, elements, components, and / or groups.

[0017] As used herein, the term “and / or” can include any and all combinations of one or more of the associated listed items.

[0018] As used herein, the terms “first,” “second,” etc. should not limit the elements being described by these terms. These terms are only used to distinguish one element from another. Thus, a “first” element discussed below could also betermed a “second” element without departing from the teachings of the present disclosure. The sequence of operations (or acts / steps) is not limited to the order presented in the claims or figures unless specifically indicated otherwise.

[0019] It will be understood that when an element is referred to as being "on," "attached" to, "connected" to, "coupled" with, "contacting," etc., another element, it can be directly on, attached to, connected to, coupled with or contacting the other element or intervening elements may also be present. In contrast, when an element is referred to as being, for example, "directly on," "directly attached" to, "directly connected" to, "directly coupled" with or "directly contacting" another element, there are no intervening elements present. It will also be appreciated by those of skill in the art that references to a structure or feature that is disposed “adjacent” another feature may have portions that overlap or underlie the adjacent feature.

[0020] As used herein, the term “electrode” can refer to a conductor through which electricity can flow. An electrode can be positioned in, on, and / or near a neural structure to alter conduction in the neural structure to cause an effect in a patient’s neural system when one or more electrical signals (e.g., having a current or voltage waveform) are delivered through the electrode. As described herein the electrodes are configured for insertion into a nerve between the fascicles of the nerve.Examples of the electrode can include at least a portion of a wire, a microwire, a conductor, and / or a contact.

[0021] As used herein, the term “neuroretractor” can refer to a surgical instrument designed to hold at least a portion of a nerve (or nerves) during a neurological procedure to provide oppositional pressure to insertion instruments (e.g., a spring-loaded inserter). It is important to note that a neuroretractor is functionality different from a traditional nerve root retractor or a neurosurgery retractor, which merely move and / or hold tissues and / or nerves away from a surgical site.

[0022] As used herein, the term “neural structure” can refer to any portion of a neural system of a patient that can conduct an action potential. A neural structure can be a nerve, an axon, a fiber, a ganglionic chain, or the like.

[0023] As used herein, the term “nerve” can refer to an enclosed, cable-like bundle of fascicles each containing one or more axons, also referred to as fibers, that send messages from parts of the body to the brain and / or vice versa in the formof electrical signals. As an example, a nerve can be a motor nerve, a sensory nerve, or a mixed motor and sensory nerve. As another example, a nerve can be an autonomic nerve (also referred to as one or more ganglia) that can include sympathetic fibers and / or parasympathetic fibers. The sympathetic trunk is a specific example of a ganglia, located on either side of the spinal cord, that can hold sympathetic fibers, while parasympathetic ganglia tend to be located near or within target organs.

[0024] As used herein, the term “fiber” can refer to an axon, which is a long slender projection of a nerve cell or neuron in vertebrate organisms having a diameter that corresponds to conduction velocity. Generally, a fiber conducts electrical impulses transmitting information in one or more directions throughout the body and is classified depending on, for example, the type of fiber (e.g., sympathetic, parasympathetic, sensory, motor, etc.), the diameter of the fiber, and / or if myelin is present.

[0025] As used herein, the term “fascicle” can refer to a bundle of fibers belonging to a nerve that are enclosed by a perineurium. Each enclosed nerve fiber in a fascicle is surrounded by at least one connective tissue layer of endoneurium and each fascicle is surrounded by epineurium.

[0026] As used herein, the term “perineurium” can refer to the protective sheath that surrounds a fascicle and bundles together axons targeting the same anatomical location. Perineurium includes connective tissue and fibroblast cells. The perineurium is a smooth, transparent tubular membrane which may be easily separated from the enclosed fibers.

[0027] As used herein, the term “epineurium” can refer to the outermost layer of dense irregular connective tissue surrounding a peripheral nerve. The epineurium usually surrounds multiple nerve fascicles as well as blood vessels which supply blood to the nerve. The epineurium is a tough and mechanically resistant tissue which is not easily penetrated by a needle

[0028] As used herein, the term “interfascicular” can refer to the space between fascicles and / or objects positioned in the space between fascicles within a nerve.

[0029] As used herein, the terms “patient” or “subject” or the like can be used interchangeably and can refer to any warm-blooded organism, including, but not limited to, a human being, a pig, a rat, a mouse, a dog, a cat, a goat, a sheep, ahorse, a monkey, an ape, a rabbit, a cow, etc. The terms patient and subject can be used interchangeably herein.II. Overview

[0030] As peripheral nerve stimulation (PNS) has evolved with the goal of treating new nerve targets and pathologies, there has been a push to develop higher selectivity peripheral nerve interfaces (also referred to as electrodes) that can activate small populations of axons within a nerve without activating other populations of axons within the same nerve. Current examples of electrodes used for PNS can include electrodes positioned near a nerve (referred to as “proximal electrodes”), around a nerve (also referred to as “circumneural electrodes”), and within fascicles of a nerve (also referred to as “intrafascicular electrodes”). Intrafascicular electrodes (e.g., flat interface nerve electrodes (FINE), longitudinal intrafascicular electrode (LIFE), transverse intrafascicular multichannel electrodes (TIME), and the like) that are implanted through fascicles of nerves currently allow for the best selectivity for PNS. However, intrafascicular electrodes are invasive and difficult to implant without causing nerve damage to a patient. Intrafascicular electrode implantation can rupture the blood-nerve barrier and can cause morphological changes to the nerve (e.g., axon loss). Additionally, certain tyles of intrafascicular electrodes can only be used with superficial fascicles within a nerve because these intrafascicular electrode arrays cannot reach deeper fascicles.

[0031] Interfascicular electrodes are more flexible than intrafascicular electrodes and offer greater selectivity than intrafascicular electrodes. However, this flexibility can cause interfascicular electrodes to buckle under the forces necessary for insertion through the epineurium of a nerve. Various strategies have been explored to address this insertion issue, including: mechanical bracing, transient stiffening materials, ultrasonic-assisted insertion, and the use of mechanically dynamic materials that adapt wire stiffness in response to external stimuli. However, these strategies add unnecessary complexity and / or invasiveness to the insertion process.

[0032] Described herein is a minimally invasive interfascicular nerve stimulation (MiiNS) system and method for inserting a flexible electrode through the epineurium and between fascicles of a nerve. Compared to previous insertion methods, MiiNS system and method is less complex and invasive without adding the potential for failure and damage. With the MiiNS system and method, a neuroretractor withflexible bristles can be positioned around a portion of an exposed nerve to stabilize the nerve. Then, a spring-loaded inserter can deliver the flexible electrode (a part of which may be hooked) into the nerve via a blunt micro-cannula. Upon insertion of the micro-cannula and flexible electrode into the nerve, transient, non-damaging pressure can be applied to a surface of the nerve with a soft pressure applicator. The soft pressure applicator can temporarily increase the friction between the flexible electrode and the tissue inside the nerve to ensure the flexible electrode can be reliably deposited in the nerve. The micro-cannula can then be rapidly retracted by retracting at least a portion of the spring-loaded inserter, leaving behind the flexible electrode in the nerve between the fascicles without breaking the flexible electrode. The rapid retraction of the micro-cannula can reduce the frictional force between the flexible electrode and the micro-cannula, while the applied pressure to the nerve can increase the static friction between the flexible electrode and the surrounding tissue. Using the MiNS system and method flexible electrodes can be positioned less invasively and more effectively position into the interfascicular space of a nerve for higher selectivity PNS.III. Systems

[0033] FIG. 1 shows a block diagram of a Minimally Invasive Interfascicular Nerve Stimulation (MiiNS) system 10 for insertion of a flexible electrode 12 into a nerve. At least a portion of the elements of the system 10 can be embodied as a kit with one or more instructions for use. The system 10 can be used to insert one or more flexible electrodes (flexible electrode(s) 12) (which may be within one or more micro-cannulas 14) into the interfascicular space in a nerve between one or more fascicles without breaching the epineurium of the fascicles. Main elements of the system 10 (which can be embodied in the kit, in some instances) can include at least a neuroretractor 16, a spring-loaded inserter 18, and a soft pressure applicator 20. The system 10 may also include the flexible electrode(s) 12 for insertion, the microcannula^) 14 configured to hold the flexible electrode(s) for insertion, and / or a specialized MiiNS cartridge 22 configured to store the electrode(s) within the microcannula^) prior to and / or during use of the system. In other instances, the flexible electrode(s) 12, the micro-cannula(s) 14, and / or a holder for the flexible electrode(s) / micro-cannula(s) can be used with the system 10, but need not bepurchased with the kit (although in some instances, one or more of the flexible electrode(s) 12, the micro-cannula(s) 14, and / or a MiiNS cartridge 22 for the flexible electrode(s) / micro-cannula(s) can be purchased with the kit).

[0034] FIG. 2 shows an illustration of the components of system 10 in use to insert flexible electrode(s) 12 into an exposed peripheral nerve that includes at least one fascicle (although a poly fascicular peripheral nerve is preferred and will be described). The flexible electrode(s) 12 can be inserted through the epineurium into the interfascicular space between the fascicles of the nerve without disrupting the perineurium of each of the fascicles. It should be understood that these illustrations are only examples of how the components of system 10 can be embodied and that they can take different shapes and / or configurations to have the functions described herein.

[0035] The neuroretractor 16 can include at least a plurality of flexible bristles (not shown in this view, because the bristles are hidden by the body of the nerve) that can ensnare a deep surface of the epineurium of a portion of a nerve. The neuroretractor 16 can be positioned at least partially around the portion of the nerve to provide an oppositional force during insertion of the flexible electrode(s) 12. The spring-loaded inserter 18 (pre-loaded with a flexible electrode 12 within a microcannula 14) can be positioned and configured to deliver the flexible electrode(s) 12 at an angle relative to the surface of the nerve to insert the flexible electrode(s) between the one or more fascicles. The angle of insertion (between the body of the inserter and the surface of the nerve) can be, for example, 35 degrees or less, 30 degrees or less, 25 degrees or less, 20 degrees or less, 18 degrees or less, 15 degrees or less, 12 degrees or less, 10 degrees or less, 7 degrees or less, 5 degrees or less, 3 degrees or less, or the like.

[0036] The spring-loaded inserter 18 can deliver the flexible electrode(s) 12 (e.g., one at a time) into the portion of the nerve by forcing the flexible electrode(s) from a micro-cannula(s) 14 loaded into the end of the spring-loaded inserter. The spring-loaded inserter 18 can, after insertion, retract the micro-cannula(s) 14 while leaving the flexible electrode(s) 12 in the portion of the nerve between the fascicles of the nerve. During the insertion and retraction process the soft pressure applicator 20 can apply pressure (e.g., a transient pressure soft enough to not cause permanent damage) to another portion of the nerve opposite the neuroretractor (andnear the insertion site) to increase friction between the flexible electrode(s) 12 and the nerve when the nerve is braced by the neuroretractor 16. This process can be repeated to safely and effectively insert as many flexible electrode(s) 12 as needed for fascicle and / or axon specific selective stimulation (e.g., PNS).

[0037] FIG. 3, element A shows a generic block diagram representation of a neuroretractor 16 and FIG. 3, element B shows an example form-factor of a neuroretractor 16. The neuroretractor 16 can prevent the nerve from deflecting away from the spring-loaded inserter 18 during delivery of the flexible electrode(s) 12 into the nerve. The neuroretractor 16 can include a plurality of flexible bristles 32 configured to ensnare a portion of the deep epineurium without causing significant and / or long term damage to the epineurium. The plurality of flexible bristles 32 can be attached to and / or extend from at least one surface of the neuroretractor 16. The plurality of flexible bristles 32 can be any shape, size, or material that can ensnare a portion of the deep epineurium without causing significant and / or long term damage. The plurality of flexible bristles 32 can face in a same direction and / or one or more different directions (e.g., may cross over one or more other bristles, or the like). As shown in FIG. 3, the neuroretractor 16 can further include a boot portion (boot 34) the flexible bristles 32 can be attached to and / or arise from (e.g., manufactured from a single material). The neuroretractor 16 can also include a handle 38 for a user (e.g., medical professional, surgical robot, or the like) to hold the neuroretractor in position and a shaft 36 that can connect the boot 34 and the handle.

[0038] More specifically, as shown in element B, the handle 38 can be a rigid handle having a first end, a second end, and an intermediate portion therebetween. The user can grip a portion of the first end and / or the intermediate portion of the handle 38 to hold the neuroretractor 18 in position. The boot 34 can be a flexible boot that can include the flexible bristles 32 and can bend when the rigid handle is pulled up by a user. The shaft 36 can be more rigid than at least the flexible boot 34 and can connect the second end of the rigid handle 38 with a portion (e.g., a heel portion 42) of the flexible boot 34. The flexible boot 34 can include the heel portion 42, a toe portion 40, and a bottom portion 44. The heel portion 42 can connect with the shaft 36 and can extend a distance up a side of the portion of the nerve and the toe portion 40 can extend and / or wrap a distance at least partially around / up another side of the portion of the nerve opposite the heel portion (e.g., to cause a “U” shapedpartial enclosure around the nerve with the rest of the boot 34). The bottom portion 44 can extend between the heel portion 42 and the toe portion 40 (e.g., forming the bottom of the “U” shape) and the bottom portion can be positioned around (e.g., underneath, beside, etc. depending on the angle the neuroretractor 16 is held at) the portion of the nerve. The nerve facing side of the bottom portion 44 can include the flexible bristles 32 (e.g., connected to or extending therefrom towards the nerve to catch at least a portion of the epineurium). The flexible bristles 32 can extend up from the bottom portion 44 at one or more angles to ensnare the at least the portion of the nerve.

[0039] FIG. 4, element A shows a generic block diagram representation of a soft pressure applicator 20 and FIG. 4, element B shows an example form-factor of a soft pressure applicator 20. The soft pressure applicator 20 can apply pressure to another portion of the nerve opposite the neuroretractor 16 to increase friction between the flexible electrode 12 and the nerve for at least a portion of the time while the nerve is braced by the neuroretractor. The soft pressure applicator 20 can include at least a handle 46 and a pressure head 48. The pressure head 48 can be a flexible, dome shaped head attached to an end of the handle 46 and can be configured (e.g., sized, shaped, and composed of one or more materials) to apply transient pressure to the nerve that is atraumatic. In some instances, the soft pressure applicator 20 can be configured so not to permanently damage the nerve (in other words, any damage caused is temporary - resolved in less than a month, week, day, 12 hours, 6 hours, 3 hours, 1 hour, 30 minutes, 15 minutes, 10 minutes, 5 minutes, 1 minute, or the like, after removal). In further instances, the soft pressure applicator 20 can be configured such that the only damage caused is non-functional damage. In other instances, the soft pressure applicator 20 can be configured not to damage the nerve at all.

[0040] FIG. 5, element A shows a generic block diagram representation of a spring-loaded inserter 18 and FIG. 5, element B shows an example form-factor of a spring-loaded inserter 18. Both FIG. 5, element A and element B show the spring- loaded inserter 18 loaded with a micro-cannula 14 holding a flexible electrode 12. The spring-loaded inserter 18 can deliver the flexible electrode(s) 12 into the portion of the nerve by removing a flexible electrode 12 from a micro-cannula 14 loaded intoan end of the spring-loaded inserter and can then retract the micro-cannula with enough force to leave the flexible electrode in the portion of the nerve.

[0041] The spring-loaded inserter 18 can include at least an insertion body 56 with at least an end configured to hold a micro-cannula 14. In some instances, the micro-cannula 14 can be loaded with a flexible electrode 12. The spring-loaded inserter 18 can also include a spring 54 and a trigger 52 that can load and unload the spring (e.g., compact the spring so the spring can apply a force to the micro-cannula 14 and / or let the spring extend so the spring can apply little or no force to the microcannula). The insertion body 56 can have the first end configured to hold the microcannula 14 loaded with the flexible electrode 12 for insertion into the portion of the nerve, an intermediate portion, and a second end. The intermediate portion can be configured to be held by a user (e.g., medical professional, surgical robot, etc.) and can at least partially house the spring 54. The second end can optionally have the trigger 52 extending therefrom. The spring 54 can be removably connected to the micro-cannula 14 and can retract the micro-cannula into the insertion body 56 with a force. The trigger 52 can release the spring and retract the micro-cannula, while leaving the flexible electrode 12 inserted.

[0042] As shown in element B, the flexible electrode 12 can have at least one electrode contact 60 (at one or more position(s) along the electrode) and at least one hooked end 58. The hooked end 58 can, for example be pre-loaded into the opening of the micro-cannula 14. It should be understood, however, that the flexible electrode 12 need not have a hooked end 58. The micro-cannula 14 can have a blunt and / or beveled end that can pierce through the epineurium but not through the perineurium when inserted via the spring-loaded inserter 18 at an angle relative the nerve (e.g., 40 degrees or less, 25 degrees or less, or the like from the length of the nerve). As an example, the spring-loaded inserter 18 can be at an angle from 20 degrees to 40 degrees from the length of the nerve. The force of the spring 54 retracting the microcannula 14 (e.g., when the trigger 52 is released) can pull the hooked end 58 out of the micro-cannula such that at least the hooked end 58 remains in the interfascicular space and the micro-cannula is pulled out of the nerve entirely. The opposing forces of the neuroretractor 16 and the soft-pressure applicator 20 can provide pressure, forces, and / or friction to keep at least the hooked end 58 of the flexible electrode 12 within the nerve.

[0043] FIG. 6, element A shows a generic block diagram representation of a MiiNS cartridge 22 and FIG. 6, element B shows a photograph of an example formfactor of a MiiNS cartridge 22. The MiiNS cartridge 22 can include holder(s) 62 that can each hold one micro-cannula 14 with a flexible electrode 12 loaded therein. Optionally the MiiNS cartridge can be used to load the flexible electrode 12 into the micro-cannula(s) 14 held in the holder(s) 62. For example, as shown in element B, the MiiNS cartridge 22 can be configured to hold a plurality of micro-cannulas 14 each preloaded with one of the flexible electrodes 12. The holder(s) 62 can be configured to hold the micro-cannula(s) 14 in a manner that they can be easily attached into the end of the inserter by luer lock connection. The MiiNS cartridge 22 can be configured to removably attach to one or more pieces of equipment near and / or in the surgical field for ease of access to interfascicularly insert a plurality of flexible electrode(s) 12.IV. Methods

[0044] Another aspect of the present disclosure can include methods 70 and 90 (FIGS. 7 and 8) for inserting one or more flexible electrodes into a nerve between the fascicles of the nerve (in the interfascicular space). The methods can use the system (e.g., Minimally Invasive Interfascicular Nerve Stimulation (MiiNS) system 10, shown in FIG. 1 ) to insert the one or more flexible electrodes interfascicularly. The methods 70 and 90 can facilitate the placement of interfascicular electrodes for high selectivity (axon specific selectivity) of peripheral nerve stimulation (PNS). Interfascicular PNS can offer augmented access to areas of the nerve that are traditionally challenging to stimulate effectively with extra-neural approaches. Using the methods 70 and 90, electrodes and / or electrical contacts can be delivered to traditionally difficult to stimulate regions of the nerve while minimizing perineurial disruption.

[0045] For purposes of simplicity, the methods are shown and described as being executed serially; however, it is to be understood and appreciated that the present disclosure is not limited by the illustrated order as some steps could occur in different orders and / or concurrently with other steps shown and described herein. Moreover, not all illustrated aspects may be required to implement the method, nor is the method necessarily limited to the illustrated aspects.

[0046] Referring now to FIG. 7, illustrated is a method 70 for implanting a flexible electrode (e.g., 12, having at least one electrode contact) between fascicles of a nerve (e.g., a peripheral nerve). The method 70 can be repeated to implant a plurality of flexible electrodes into one or more positions on one or more nerves. Optionally at 72, a nerve (e.g., a target nerve) can be surgically exposed. For example, by circumneural exposure. In other instances, the nerve can already be exposed prior to the beginning of method 70. Also, optionally, at 74 the flexible electrode can be loaded into a micro-cannula (e.g., 14) of a spring-loaded inserter (e.g., 18). Alternatively, the flexible electrode can be loaded into a micro-cannula and the combination can be loaded into a spring-loaded inserter. As a further alternative, the spring-loaded inserter can be pre-loaded with the flexible electrode and microcannula combination. As an example, the flexible electrode can have a hook at one end and the hook can be at least partially inserted into an opening of an insertable end of the micro-cannula. The insertable end of the micro-cannula can be blunt and / or beveled so as to be capable of piercing the epineurium but not the perineurium.

[0047] At 76, a neuroretractor (e.g., 16) can be positioned in a position that captures at least a portion of the nerve to provide stabilization for inserting the flexible electrode. The neuroretractor can include a plurality of flexible bristles configured to ensnare a deep surface of an epineurium of the portion of the nerve. For instance, the neuroretractor can be like the example of the neuroretractor 16 described above in detail and can include a rigid handle, a flexible boot, and a shaft therebetween connecting the rigid handle and the flexible boot, wherein the flexible boot comprises the plurality of flexible bristles and the flexible boot is configured to bend when the rigid handle is pulled.

[0048] At 78, the flexible electrode can be delivered into the portion of the nerve with a spring-loaded inserter (e.g., 18). During the delivery of the flexible electrode the neuroretractor can prevent the nerve from deflecting away from the spring- loaded inserter. The flexible electrode can be delivered at an angle relative to the length of the nerve and the body of the spring-loaded inserter (e.g., 40 degrees or less, 30 degrees or less, 25 degrees or less, 20 degrees or less, 18 degrees or less, 15 degrees or less, or the like) to be less likely to puncture a fascicle. The delivery can include inserting the micro-cannula (at the angle) into the nerve in between thefascicles. At 80, pressure and / or force can be applied to another portion of the nerve opposite the neuroretractor with a soft pressure applicator (e.g., 20) to increase friction between the flexible electrode and the nerve. The nerve can be braced by the neuroretractor at least partially in opposition to the pressure and / or force of the soft pressure applicator. The pressure and / or force applied by the soft pressure applicator can be atraumatic and transient pressure. The pressure can be designed (e.g., the force applied and the materials of the soft pressure applicator can be chosen) not to permanently damage the nerve.

[0049] At 82, pressure on the spring of the spring-loaded inserter can be released such that the flexible electrode can remain positioned / deposited in the nerve between the fascicles and the micro-cannula is retracted. Releasing the pressure on the spring within the spring-loaded inserter can force the micro-cannula to pull out of the nerve while leaving the flexible electrode hooked within the nerve. It should be noted that more than one step of method 70 can happen simultaneously and / or at overlapping times. For example, the neuroretractor can brace the nerve during the insertion of the flexible electrode and the retraction of the micro-cannula. As another example, the soft pressure applicator may be used to apply pressure to the nerve during insertion but should be used simultaneously with the retraction of the micro-cannula to provide sufficient friction within the nerve to catch the hook of the flexible electrode as the micro-cannula is pulled out.

[0050] FIG. 8 shows method 90 for loading a spring-loaded inserter prior to inserting an electrode between the fascicles within a nerve. At 92, a micro-cannula preloaded with the flexible electrode can be selected and, at 94, removed from a minimally invasive interfascicular nerve stimulation (MiiNS) cartridge. The MiiNs cartridge can be configured to hold a plurality of micro-cannulas each preloaded with a flexible electrode for repeated performance of method 70. The MiiNS cartridge can be positioned near and / or within the surgical field and may be removably attachable to one or more other pieces of surgical equipment. For instance, the MiiNS cartridge can be sterilizable (and reusable) and can be pinned in the surgical site for access during implant. At 96, the micro-cannula can be attached to an end of the spring- loaded inserter via a luer lock attachment. The MiiNS cartridge can be specially designed for loading the micro-cannulas loaded with the flexible electrodes into the spring-loaded inserter. For instance, the geometry of the MiiNS cartridge can securethe preloaded micro-cannulas and can be compatible with standard luer locking attachments on spring-loaded inserter.V. Experimental

[0051] The following experiment is shown for the purpose of illustration only and is not intended to limit the scope of the appended claims. The experiment described herein shows that the Minimally Invasive Interfascicular Nerve Stimulation (MiiNS) system and method are less invasive means for achieving higher selectivity peripheral nerve stimulation through rapid placement of electrodes within a nerve. Although the MiiNS technique can be used for multi-contact insertions, smaller or more flexible interfaces, more mechanically dynamic interfaces, and the like, the MiiNS technique was used to demonstrate that microwire contacts can be implanted and positioned within poly-fasciculated, clinically relevant porcine nerves. It should be noted that the MiiNS technique is agnostic to the material and configuration of contacts themselves. Additionally, the microwire interface largely serves as a proof of concept for the placement and activation of interfascicular electrodes.

[0052] I. Methods and Materials

[0053] A. Animal Cohort

[0054] Animal cohort consisted of N=7 Female Yorkshire pigs, weight ranging 100-210 lbs. N=10 total nerves (N=7 median and N=3 ulnar, samples 1 -10) were implanted and considered for study of electrode placement. Electrode placement data was only obtained from terminal implants, as micro-CT imaging necessitated nerve excision. The surgical and experimental procedures were done with the approval and oversight of the Case Western Reserve University, Institutional Animal Care and Use Committee to ensure compliance with all federal, state and local animal welfare laws and regulations.

[0055] B. MiiNS Microwire Arrays

[0056] Each interfascicular implant contained 3-8 microwire contacts (Fort Wanye Metals, 50um diameter 316 LVM, insulated to an outer diameter of 70um). Each microwire had an area of exposed wire that was inserted into a blunt microcannula, resulting a “hooked” configuration for delivery into the nerve (See FIG. 10). Care was taken to insert only the distal most 2mm of wire into the microcannula prior to implant. The microwires connected to an insulated stranded stainless steellead wire (Fort Wayne Metals) via conductive epoxy and a mechanical crimp. The lead wires were contained in a silicone tube for routing through the body. FIG 9 demonstrates the MiiNS interface (electrodes positioned in a peripheral nerve) in concept.

[0057] C. Surgical Implantation

[0058] All surgical instruments were sterilized either with ethanol (EtOH) or autoclave sterilization on a standard instrument cycle. Animals were initially sedated with Tiletamine & Zolazepam (2-6 mg / kg, IM), before placement of an endotracheal tube, to deliver 2-3% isoflurane to effect throughout the procedure. The pig was placed in a dorsal decubitus position, with the surgical table elevated on the contralateral side to give increased access to the brachial plexus. Prior to an incision, local lidocaine was administered to reduce isoflurane burden on the medial aspect of the upper forelimb 2-5 cm above the medial epicondyle to access the proximal median and ulnar nerves, distal to the nerves respective divergence from the chords. Following the incision, the pectoralis superficalis muscle was dissected to expose the brachial plexus, allowing separation and identification of the vessels and nerves. Bipolar cautery throughout the procedure reduced bleeding, while avoiding application of direct current to nerves of interest. The bicep muscle was useful as an anatomical landmark to identify the median nerve, which is located near the caudal surface of the muscle body. The ulnar nerve was subsequently identified in the caudal direction relative to the median nerve, diverging from the medial chord.

[0059] D. Surgical Tooling Development for Interfascicular Microwire Implantation

[0060] To enable MiiNS implantation, a reliable surgical implantation strategy needed to be developed. Several techniques were iteratively explored to achieve consistent placement.

[0061] A previous biomechanical characterization study of needle geometry recommended 18-degree tip angles for successful penetration of the perineurium. Further, previous biomechanical characterization of nerve tissues found that the perineurium had a significantly higher penetration force than the epineurium, and this difference was maximized with a blunt probe. Blunt microcannulas have also been used to deflect micro vessels upon injection, to reduce bruising. Accordingly, a bluntmicro-cannula (34g, Cellink) was chosen for implantation of MiiNS to aid in penetration of the epineurium while keeping the perineurium intact.

[0062] In the early trials (S1 -4), the microwire-loaded blunt microcannulas were affixed to an acrylic shuttle, via cyanoacrylate glue and inserted into the nerve via forceps. Once the microcannula was positioned within the nerve, the acrylic shuttle was retracted and removed by hand to leave behind the hooked microwire. However, in later trials (S5-10), a novel tool set (Fig. 10) enabled implantation.

[0063] Following circumneural exposure, a novel Neuroretractor (Fig. 10, box C) was placed beneath the nerve to provide stabilization. The device featured flexible bristles that gripped the deep surface of the epineurium, preventing deflection during oppositional needle insertion on the superficial surface. Then, a spring-loaded inserter delivered a hooked microwire contact to the nerve via a blunt micro-cannula (Fig. 10, box A). Upon insertion of the micro-cannula into the nerve, transient, nondamaging pressure was applied to the surface of the nerve with a soft pressure applicator (Fig. 10, box B). The soft pressure applicator had a gel tip mechanically locked into a rigid handle, and the applicator temporarily increased the friction between the microwire and the surrounding nerve tissue to ensure the microwire was reliably left in the nerve. The microcannula was then rapidly retracted via a spring, leaving behind the hooked microwire in the nerve. The rapid retraction of the microcannula reduced the frictional force between the microwire and the microcannula, while the applied pressure to the nerve increased the static friction between the microwire and the surrounding tissue. Combined, this design encouraged the microwire to remain in the nerve tissue during microcannula removal. All three devices were 3D printed (Formlabs 3B), with the rigid components printed using biomedical resin, and the flexible components printed with Elastic 50A.

[0064] While insertion angle was not controlled for intraoperatively, the surgeon intuitively placed the microcannula at an oblique angle along the nerve’s longitudinal axis rather than perpendicular to the nerve’s longitudinal axis. The effect of insertion angle on electrode placement was analyzed post hoc. Following successful implant of a microwire contact the surgeon discarded the used blunt microcannula and reloaded the inserter with the next microwire-loaded microcannula. Electrode implantation time was recorded in two phases: an initial set of four nerve implant trials using manual hand insertion (N = 24 total contacts), and a subsequent set offive nerve implants using the novel tool set, during which insertion time was recorded for 25 total contact placements.

[0065] E. Tissue Handling

[0066] At the termination of the acute procedure, the implanted nerves were collected and placed directly in 10% neutral buffered formalin with a volume at least 50x the total tissue volume for at least 2 days and up to 4 weeks before staining and scanning. The time between the euthanasia and tissue collection was minimized to prevent tissue drying and distortion of neural tissue.

[0067] F. Micro-Computed Tomography Staining, Parameters, and Analysis

[0068] To visualize fascicular anatomy within the nerve, Phosphotungstic acid (3% v / v) (PTA) was prepared with deionized water to increase soft-tissue contrast. Each sample was submerged in 50 mL of PTA and placed on an orbital shaker for 48 hours. The samples were then washed with 50 mL of 1 X PBS for five minutes, twice, before scanning. In cases where stain did not sufficiently diffuse in the sample to visualize fascicles, the staining was repeated for an additional 48 hours. If the sample failed to stain past the additional 48 hrs, the sample was stained in 1 % Lugol’s Iodine to allow for fascicular visualization (this occurred only in one sample (S8)).

[0069] Scanning was done using a Scanco pCT 100. The sample was glued to a 3D printed PLA board using a polyurethane adhesive (Gorilla Glue) and placed in a tube provided by Scanco. The board had 5mm spaced indentations, which allowed for co-registration of repeated scans. Scans were first performed with a 90 kV tube voltage, 4 pA tube current, a 0.5 mm aluminum filter, 3000 projections across 360°, and reconstructed with an isotropic voxel size of 4.9 pm. A lower resolution scan initially confirmed that the stain had diffused throughout the entire cross section of the nerve. In some trials (N=3), once the initial scan was completed, the microwires were carefully removed from the sample using forceps and re-scanned using the same settings, but 55kV. A small amount of phosphate buffered saline (PBS) was placed in the bottom of the scan tube to prevent excessive sample drying during scanning.

[0070] Electrode Placement: Imaged was used to analyze the placement of the MiiNS contacts relative to the fascicles and their distribution throughout the nerve cross-section. Each nerve scan was opened every 5 slices, resulting in a Z axisresolution of 25um. The image intensity range was adjusted so the dimmest voxel was 0. For placement analysis, each scan was transformed via rotation or reversal if necessary to align the superficial, implanted surface of the nerve as “up” and to make the proximal to distal directions consistent between samples, with slice 1 being most proximal.

[0071] The 3D coordinates that defined the location of each MiiNS contact were determined by first tracing the microwire’s trajectory through the slices of the microCT. The slice which contained the proximal appearance of the microwire, corresponding to the apex of the hook was saved for further analysis. In each of these slices, the entire nerve cross-section was traced, and the centroid of the traced area was calculated and defined as the origin. The position of the MiiNS contact was then characterized using a normalized vector r, defined from the centroid pCentroid’to the electrode peiectrodewascomputed as:

[0073] where_rcircieis the radius of a circle of equivalent area as traced, r vector has a magnitude value R and a polar angle 9 (see FIG. 11 ). FIG. 11 shows a representative micro-CT nerve slice containing the most proximal appearance of the apex of a hooked microwire contact (translucent copper circle). Nerve perimeter is manually traced in green, and calculated centroid is denoted in pink. Vector r (blue) with normalized magnitude R and angle theta is defined between the centroid and the electrode, considering the centroid as the origin. The magnitude value R is displayed

[0074] To consider the cumulative placement of all of the contacts across the nerve samples in the longitudinal z direction, the midplane between the most distal and most proximal contact was centered at zero. In some cases, the normalization of the vector r resulted in an R magnitude slightly greater than 1 , an artifact of approximating the nerve as a perfect circle despite its oblong cross-sectional appearance in some areas. While these contacts appeared to reside outside of the nerve volume after normalization, visual inspection confirmed that these instances were within the nerve’s bounds. No contacts that were completely outside of the nerve were considered.

[0075] Intraneural Placement Classification: Each microwire electrode was also classified as inter or intra- fascicular, relative to the fascicular anatomy. Classification was based on visual inspection of each microwire’s position relative to fascicular boundaries across all visible slices and fascicles, with intrafascicular placement defined as any instance of wire traversal through or within a fascicle. Fascicles frequently demonstrated significant deflection and deformation around a microwire. A microwire placement was considered intrafascicular when the fascicle boundary could be distinctly resolved, encircling the microwire. An example of this is shown in FIG. 15. This ensured that the electrode was within the fascicular tissue, rather than merely alongside it.

[0076] Angle of Insertion: Analysis was performed on the microCT scans to understand the relationship between angle of micro cannula insertion into the nerve intraoperatively and the placement of the microwire. The angle of wire trajectory was assessed by first finding the centroid of the nerve area in all sections using FIJI image processing (FIJI, Analyze Particles). The wire position was manually tracked and segmented from its most proximal appearance to the point at which it exited the nerve. Care was taken to only consider points that were inside of the nerve, stopping segmentation upon the microwire’s exit from the nerve. The first and last points of this segmentation were used to define a wire trajectory vector, while the centroid points were linearly fit to find a nerve centroid vector, which represents the nerve’s longitudinal axis. The use of the first and last point of the wire as opposed to fitting the entirety of the wire was chosen to account for the bowing that occurred in the wire, likely upon microcannula removal during implantation and would otherwise distort the wire’s true trajectory. The wire trajectory angle of each microwire was defined by the angle between the wire trajectory vector and the nerve centroid vector.

[0077] Histology. In N=4 of the microCT nerve samples (S5,S6,S7,S8), histology was performed post Micro-CT, to validate the positional information content and fascicle boundaries of the microCT analysis. In these cases, the wires had not been previously removed for rescanning. For each sample, a 15 mm segment of the nerve containing the majority of the microwires was excised, and the microwires were gently removed with forceps. The position of the excised tissue was measured relative to the most proximal aspect for later co-registration with prior microCT scans.The proximal and distal and superior / inferior orientations of the tissue were marked with tissue dye. Nerves segments were further sectioned into 3-4 tissue samples before dehydration, embedding and staining. Nerves were processed using a Pegasus Automated Tissue Processor (Leica Biosystems), which first dehydrated nerve samples with increasing concentrations of ethanol, then washed with xylene. Nerves were then embedded in paraffin (Sakura TEC 6 Embedding and Cryo Console) and cut with a microtome (Leica Histocore Autocut). Every 100um, three slides from each section were produced. Hematoxylin and Eosin staining was performed using an automated slide Stainer (Leica Spectra ST) and Statlab stains. Each histological slice was co-registered with its corresponding micro-CT slice using manual inspection. The microCT images were rotated to reflect the orientation of the histological slice. Examples of anatomical landmarks which enabled co-registration included relative positions of dynamically merging / diverging fascicles, positions of microvasculature, positions of microwires or microwire voids and fascicular shape.

[0078] II. Results

[0079] A. Surgical Tooling Assessment for Interfascicular Microwire Implantation

[0080] The combined use of the neuro-retractor, spring-loaded inserter, and geltipped pressure applicator consistently enabled successful and rapid implantation of microwire contacts into the nerve (S5-10). In contrast to S1 -4, which used hand insertion, the vast majority of insertions were successful on the first attempt using the neuro-retractor, spring-loaded inserter, and gel-tipped pressure applicator. In a subset of cases, the microwire failed to be retained in the nerve following microcannula retraction and remained instead in the microcannula. This subset of cases required reinsertion. Less frequent failure modes included through and through penetration of the nerve and microcannula buckling during insertion. Timing data was recorded during five nerve implantations (N=3 median, N=2 ulnar), in which five MiiNS contacts were placed per nerve (N=25 insertions total) with the novel toolset. The average insertion time per contact was 1 .8 ± 0.18 minutes. In earlier trials (S1 -4), the insertion of MiiNS by hand took 3.07+ / -1 .2 minutes per contact (N=24 insertions total).

[0081] B. MicroCT Visualization of Intraneural Microwire Array

[0082] Nerve Structure and Microwire Visualization: The staining and scanning protocol outlined allowed for the successful co-visualization of the microwires andfascicular anatomy in every nerve. FIG. 1 1 shows a representative microCT slice, demonstrating high contrast between the fascicles and surrounding interfascicular tissue. Each fascicle is low intensity, enclosed in higher intensity perineurial tissue, allowing for delineation of fascicular boundary throughout the length of the nerve. In every scan, each fascicle of each nerve and the wires were able to be visualized using phosphotungstic acid (PTA) staining protocol, apart from sample 8 (which due to sample drying had poor stain diffusion and required Lugol’s 1 % iodine solution for 72hrs, which enabled visualization). Initial metal artifacts from the stainless steel microwires were observed during scanning; however, the artifacts were substantially reduced by using a 90 kV tube voltage. In cases where the sample was rescanned after microwire removal, the voids left behind by the microwires were clearly visible and spatially consistent with the original scans, confirming the accuracy of wire localization despite the presence of metal (FIG. 15).

[0083] C. Analysis of MUNS Contact Placement

[0084] Spatial Distribution of Microwires: Each microwire slice containing the apex of each hooked microwire was considered for placement analysis. When all contacts were considered cumulatively across samples (FIG. 12), the average normalized vector distance from centroid to electrode (R) was 0.4811 ± 0.28, indicating that placements span both central and peripheral regions of the nerve cross-section. However, there was a preference for central positioning- 79% of contacts were placed in the central half of the nerve volume (R<0.707). The mean angle of the vector R was 199.5+ / - 72.2 degrees (circular mean and StDev), which corresponds to a tendency for placement in the lower left quadrant of the nerve, but a wide standard deviation suggests very little clustering. To further understand the distribution of implant angles (6), Rayleigh’s test of uniformity was performed on the cumulative data set, which tests if the angles of the r "* vector depart from a uniform distribution about a circle in a unimodal, von Mises distribution. The cumulative dataset of placements failed to reject the null hypothesis (p=0.094) suggesting that the data does not show statistically significant departure from a uniform distribution. Each nerve sample showed spatially distinct contact positions (FIG. 13), with average pairwise Euclidean and transverse distances across all contacts of 5352.80 ± 4049.70 pm and 1415.84 ± 753.98 pm, respectively. To further understand how close the contacts were placed to each other, the Euclidian and transversedistance between each contact and its nearest neighbor was determined. The average nearest neighbor distance per sample is summarized in FIG. 13. On average, the Euclidian distance from any contact to its nearest neighbor was 2256.26+ / -1760.28 pm across all samples. In only the transverse (XY plane) direction, the average nearest neighbor was 730.71 + / -564.83 pm.

[0085] In the longitudinal direction, the average total span between the most proximal and distal contacts within a nerve was 10.3+ / - 4.3 mm. This value can be readily manipulated with surgical intent to be more clustered or more spread.

[0086] Classification of Inter or Intrafascicular Placement: Each microwire’s entire trajectory within the neural tissue was classified as interfascicular or intrafascicular based on the wire’s position relative to the boundaries of fascicles. FIG. 14 demonstrates a representative intra-fascicular placement, both with and without the wire present. In this case, perineurial and endoneurial disruption is apparent. Over 56 total placements, N=9 showed definitive intrafascicular behavior on any part along the wire trajectory, while the remaining 47 (84%) appeared between and alongside the fascicles. The perineurial rupture did not necessarily occur at the site of the hooked contact. In 2 / 9 cases, fascicle penetration occurred at a fascicle branch point. All intrafascicular placements were observed in the median nerve.

[0087] Role of Novel Tool Development on Electrode Placement: Without the novel tool set, the by hand insertions of S1 -4 resulted in 74% interfascicular placement across 23 placements. The later samples with the novel tools were 88% interfascicular across 33 placements

[0088] D. Effect of Angle of Insertion on Contact Placement

[0089] To understand how insertion trajectory of the microwire into the nerve influences the electrode's placement within the nerve, we quantified the angle between each microwire’s trajectory and the longitudinal axis of the nerve (see FIG. 15). All the wires exhibited some degree of bowing within the nerve, likely because of the retraction of the microcannula during insertion. This segmentation approach allowed for comparison of microwire trajectory angles across nerves and across intrafascicular and interfascicular placements. Due to relatively small and uneven sample sizes, a non-parametric Wilcoxon Rank Sum Test was used to compare the angles of wire trajectories between groups. A Holm-Bonferroni correction wasapplied to adjust for repeated comparisons. The angle between each microwire trajectory vector and the nerve centroid vector differed significantly between median nerves and the ulnar nerves, between all intrafascicular and interfascicular placements, as well as between intrafascicular and interfascicular placements in the median nerves alone. Median nerves had a steeper average insertion angle, while ulnar nerve insertions were more parallel (19.0+ / - 13.0 and 6.3+ / - 2.3 respectively). Further, across all nerves, all intrafascicular insertions had a steeper angle of insertion compared to all interfascicular insertions (29.5+ / - 20.9 and 12.9+ / - 8.2 respectively). Finally, in the median nerve alone, where all intrafascicular placements occurred, there was a significantly steeper angle of insertion for intrafascicular placements compared to interfascicular placements (29.5+ / - 20.9 and 16.0+ / - 8.1 respectively).

[0090] E. Comparative Histological Analysis of Contact Placement

[0091] Each histological slice of each studied nerve sample (S5,S6,S7,S8) was successfully co-registered to its corresponding microCT slice using anatomical landmarks. Histological analysis was performed on the most recently available samples, which had not undergone repeated scanning and still contained microwires. Sample 5 had exhibited intrafascicular placement on the microCT, however the exact position of perineurial rupture was not captured histologically. Throughout the histological samples, perineurial membrane was clearly visualized around each fascicle. Across these histological samples, there was no evidence of perineurial penetration. The location of the removed wires was identified by the presence of a void and surrounding tissue disruption (FIG. 16). The site of implantation showed local recruitment of neutrophils. The micro-CT analysis often showed deflection of a fascicle around a microwire. Such deflection was observed both in the histology and micro-CT. In these cases, histology showed the perineurial membrane was visually intact. In all cases where histology was available, micro-CT and histological

[0092] During initial placement trials of MUNS, the need for tool development was realized. A system was engineered that enables the rapid placement of microwire electrodes within the nerve. The neuro retractor, spring-loaded inserter, and gel tipped applicator facilitate successful placement of 50 urn microwires which would readily buckle upon contact with soft tissue if placed without the system. Smalland flexible peripheral nerve interfaces such as these wires and tools are essential to minimize neural damage from mechanical factors. It is noted that the novel tools described herein are agnostic to the material and configuration of the contacts themselves and can be used with other types / materials of microwire contacts. By this method microwire contacts were delivered in a hooked configuration, and did not require passing through the entire nerve, which is conducive to less invasive surgical technique. In this study, the microwire interface largely served as a proof of concept for the placement and activation of interfascicular electrodes. The tools and method described herein can be used for multi-contact insertions, smaller or more flexible interfaces, and / or more mechanically dynamic interfaces.

[0093] From the above description, those skilled in the art will perceive improvements, changes, and modifications. Such improvements, changes and modifications are within the skill of one in the art and are intended to be covered by the appended claims.

Claims

The following is claimed:1 . A method for implanting a flexible electrode between fascicles within a nerve comprising: positioning a neuroretractor in a position that captures at least a portion of the nerve to provide stabilization, wherein the neuroretractor comprises a plurality of flexible bristles configured to ensnare a deep surface of an epineurium of the portion of the nerve; delivering the flexible electrode into the portion of the nerve with a spring- loaded inserter; applying pressure to another portion of the nerve opposite the neuroretractor with a soft pressure applicator to increase friction between the flexible electrode and the nerve, wherein the nerve is braced by the neuro retractor; and releasing pressure on a spring of the spring-loaded inserter, wherein the flexible electrode is configured to remain positioned in the nerve between the fascicles.

2. The method of claim 1 , further comprising loading the flexible electrode into a micro-cannula of the spring-loaded inserter, wherein during the delivering the microcannula is retracted from the nerve and the flexible electrode remains in the nerve.

3. The method of claim 1 , further comprising surgically exposing the nerve.

4. The method of claim 1 , wherein the delivering further comprises delivering the flexible electrode at an angle less than 25 degrees relative to the length of the nerve.

5. The method of claim 1 , further comprising: selecting a micro-cannula preloaded with the flexible electrode and removing the micro-cannula from a minimally invasive interfascicular nerve stimulation (MiiNS) cartridge, wherein the MiiNs cartridge is configured to hold a plurality of microcannulas preloaded with the flexible electrodes; and attaching the micro-cannula to an end of the spring-loaded inserter via a luer lock.

6. The method of claim 1 , wherein the flexible electrode has at least one electrode contact and at least one hooked end.

7. The method of claim 1 , wherein the neuroretractor comprises a rigid handle, a flexible boot, and a shaft therebetween connecting the rigid handle and the flexible boot, wherein the flexible boot comprises the plurality of flexible bristles and the flexible boot is configured to bend when the rigid handle is pulled.

8. The method of claim 1 , wherein the neuroretractor prevents the nerve from deflecting away from the spring-loaded inserter during delivery of the flexible electrode.

9. The method of claim 1 , wherein the releasing the pressure on the spring within the spring-loaded inserter comprises allowing a micro-cannula to pull out of the nerve while leaving the flexible electrode within the nerve.

10. The method of claim 1 , wherein the pressure is an atraumatic and transient pressure, wherein the pressure is designed not to permanently damage the nerve.

11. A kit for implanting a flexible electrode between fascicles within a nerve, the kit comprising: a neuroretractor comprising flexible bristles configured to ensnare a deep surface of an epineurium of a portion of a nerve and provide an oppositional force during insertion; a spring-loaded inserter configured to deliver the flexible electrode into the portion of the nerve by removing the flexible electrode from a micro-cannula loaded into an end of the spring-loaded inserter and to retract the micro-cannula while leaving the flexible electrode in the portion of the nerve; and a soft pressure applicator configured to apply pressure to another portion of the nerve opposite the neuroretractor to increase friction between the flexible electrode and the nerve when the nerve is braced by the neuroretractor.

12. The kit of claim 11 , wherein the flexible electrode has at least one electrode contact and at least one hooked end.

13. The kit of claim 11 , further comprising: a minimally invasive interfascicular nerve stimulation (MiiNS) cartridge configured to hold a plurality of micro-cannulas preloaded with flexible electrodes.

14. The kit of claim 11 , wherein the neuroretractor comprises: a rigid handle having a first end, a second end, and an intermediate portion therebetween; a flexible boot comprising the flexible bristles and configured to bend when the rigid handle is pulled up, and a shaft connecting the second end of the rigid handle with a portion of the flexible boot.

15. The kit of claim 14, wherein the boot of the neuroretractor further comprises: a heel portion configured to connect with the shaft and to extend up a side of the portion of the nerve; a toe portion configured to wrap at least partially around another side of the portion of the nerve opposite the heel portion; and a bottom portion extending between the heel portion and the toe portion and configured to be positioned underneath the portion of the nerve and comprising the flexible bristles.

16. The kit of claim 15, wherein the flexible bristles extend up from the bottom portion of the boot at at least one angle to ensnare the at least the portion of the nerve.

17. The kit of claim 11 , wherein the neuroretractor is configured to prevent the nerve from deflecting away from the spring-loaded inserter during delivery of the flexible electrode.

18. The kit of claim 11 , wherein the soft pressure applicator comprises: a handle; and a flexible, dome shaped head attached to an end of the handle and configured to apply transient pressure to the nerve that is atraumatic and configured to not permanently damage the nerve.

19. The kit of claim 11 , wherein the spring-loaded applicator comprises: an insertion body having a first end configured to hold the micro-cannula loaded with the flexible electrode for insertion into the portion of the nerve; and a spring removably connected to the micro-cannula and configured retract the micro-cannula into the insertion body with a force; a trigger configured to release the spring and retract the micro-cannula, while leaving the flexible electrode inserted.

20. The kit of claim 11 , wherein the spring-loaded applicator is configured to deliver the flexible electrode at less than a 25 degree angle relative to a surface of the nerve to insert the flexible electrode in between one or more fascicles.

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