BIDIRECTIONAL LIMB NEURO-PROSTHESIS

Abstract

Integrated closed-loop real-time limb neuro-prosthetic system comprising an artificial limb, a microprocessor, sensors, a signal conditioner, a stimulator, at least one EMG electrode and at least one sensory feedback electrode, characterized by the fact that said sensory feedback electrode is all intraneural electrode which is adapted to be implanted in an intact and healthy portion of a nerve.

Claims

1-12. (canceled)

13. A method performed on a closed-loop real-time limb neuroprosthetic system, the system including an artificial limb or a sensorized glove or sock, a microprocessor, sensors, a signal conditioner, a stimulator, an electromyography (EMG) electrode, and a sensory feedback electrode, the method comprising the steps of: implanting the sensory feedback electrode transversally in an intact and healthy portion of a nerve; and modulating an intensity of a sensory feedback from the sensory feedback electrode by changing an injected charge with respect to a readout of the sensors, the sensors being embedded in the artificial limb or in the sensorized glove or sock.

14. The method according to claim 13, wherein the step of modulating further comprises: modulating the intensity of the sensory feedback by changing a stimulation frequency with respect to the readout of the sensors that are embedded in the artificial limb or in the sensorized glove or sock.

15. The method according to claim 13, wherein the step of modulating further comprises: modulating the intensity of the sensory feedback by changing a time occurrence of a stimulation pattern with respect to the readout of the sensors that are embedded in the artificial limb or in the sensorized glove or sock.

16. The method according to claim 13, wherein the step of modulating further comprises: modulating the intensity of the sensory feedback by a multi-polar stimulation with respect to the readout of the sensors embedded in the artificial limb or in the sensorized glove or sock.

17. The method according to claim 13, wherein the step of modulating further comprises: modulating at least one of a type and location of the sensory feedback by changing the stimulation of an active site of a peripheral nerve interface with respect to the readout of the sensors embedded in the artificial limb or in the sensorized glove or sock.

18. The method according to claim 13, wherein the step of modulating further comprises: modulating at least one of a type and location of the sensory feedback by multi polar stimulation with respect to the readout of the sensors embedded in the artificial limb or in a sensorized glove or sock.

19. The method according to claim 13, wherein implanting the sensory feedback electrode is performed in a way as to differentiate a fiber recruitment of a fascicle.

20. The method according to claim 13, wherein implanting the sensory feedback electrode is performed in a way as to differentiate a fiber recruitment of two fascicles.

21. The method according to claim 13, wherein implanting the sensory feedback electrode is performed through insertion within a nerve fascicle.

22. The method according to claim 13, wherein the step of implanting the sensory feedback electrode includes an implanting of the sensory feedback electrode in a transversal section of a median nerve extracted at the elbow.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0039] FIG. 1: Functional and topographical organization of peripheral nerves and multi- and intra-fascicular electrodes implant. The neural fibers are organized in the peripheral nerves in fascicles that bring specific informations. This is showed (A) in a transversal section of the median nerve extracted at the elbow [31]. To take into account this characteristic the multi- and intra-fascicular electrode is implanted transversally in the nerve (B).

[0040] FIG. 2: Stimulation by intraneural and epineural electrodes. Intraneural stimulation is more selective than the extranueral one. On the left is the result of the stimulation of a targeted fascicle by means of a multi- and intra-fascicular intraneural electrode passing into it. On the right the one when the stimulating electrode is outside the nerve (like in the case of cuffs). The latter is unable to activate the targeted fascicle without eliciting also the other untargeted, that could be conducting undesired type of sensation.

[0041] FIG. 3: General description of two embodiments according to the invention. Parts A and D of FIG. 3 show two preferred embodiments of the invention. In particular, a robotic limb prosthesis (a hand in this case) is attached to the user through a functionalized socket (A) with sEMG electrodes to acquire remnant muscular activity of the amputee. The signals are processed, decoded and the proper motor commands are sent to the robot. Force sensors embedded in the robot are transformed in stimulation signals (modulating the charge in this case) and sent to the nerve (Median and Ulnar Nerves (B and C) in this case) where transversal intrafascicular electrodes are implanted. In (D) the embodiment of the invention for the lower limb case is depicted. The intraneural stimulation of the sciatic nerve is performed, based on the sensors implemented in the artificial foot (or sock).

[0042] FIG. 4: Interaction between the components of the system according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

[0043] The invention will be better understood in the following text, in a detailed description and with non-limiting examples.

[0044] FIG. 3 illustrates the way the system controls the motion of prosthetic robotic limb and restores tactile and proprioceptive sensations in amputees using force/pressure/position/angular sensors from the finger/fingertips/palm/joints/foot of a prosthetic robotic limb.

[0045] The system is constituted by a robotic limb with embedded sensors or provided with a sensorized glove (or sock), a superficial/implantable stimulator, EMG electrodes mounted in a socket or inserted in the amputee remnant muscles, a signal conditioner and multichannel intrafascicular electrodes. The robotic limb must be connectable to the socket.

[0046] A microprocessor, cable/wireless connected to the robotic limb and to the stimulator, handles the acquisition of the EMG/ENG signals and uses them for the control of the robotic limb. Furthermore, this device reads the signals from the pressure/force/angular/position sensors and uses them to drive the stimulator for current/voltage injection to the peripheral nervous system of the amputee.

Components of the System

[0047] 1. Robotic limb

[0048] The robotic limb is comprised by several features: [0049] i) The robotic limb should have one or preferably more degrees of freedom, and be equipped with at least one, preferably more, touch-pressure sensors and angular sensors on/within the finger/fingertips/palm/joints/foot. In the case the robotic limb is not provided with sensors, a sensorized glove (or sock) can be put over it. [0050] ii) In the case of more proximal (e.g. above the elbow or the knee) amputations, it should be equipped with controllable wrist/elbow/knee/ankle, provided with sensors. [0051] iii) The functionalized socket to be adapted to the stump should include monopolar or bipolar surface EMG electrodes or multipolar electrode arrays for electromyographic activity. [0052] iv) In the case of the intramuscular EMG step iii) is not required. [0053] v) In the case of targeted-muscle re-innervation (TMR) users, the electrode arrays can be placed over the targeted breast/leg muscles. [0054] 2. Artificial sensors within robotic limb or glove (or sock)

[0055] Any prosthetic hand/foot/arm/leg with force/pressure/angular/position sensors in/on the fingers/finger tips/palm/wrist/elbow/knee/ankle can be used for the method. The sensors must give a continuous measurement with a sampling frequency of minimum 10 Hz, in Pa (for pressure sensors) or N (for force-tension sensors). Position and/or angular sensors of the fingers/joints are to be used for providing proprioceptive sensations. The sensors should have capacity to detect the area of contact and precise timing of its dynamic change. [0056] 3. Implanted Electrodes

[0057] Multi- and intra-fascicular electrodes (provided with bio-compatible cables and connectors) to be implanted in the Median and/or Ulnar and /or Radial nerves, within the residual arm, or in the case of TMR amputees within the transferred nerves. For the lower limb to be implanted within femoral/sciatic/tibial residual nerves, or in the case of lower limb TMR amputees within the transferred nerves. [0058] 4. Current/voltage Stimulator

[0059] The stimulator can be transcutaneously connected to the electrodes or can be implantable. It must have at least 2 independent (in terms of the all stimulation parameters: amplitude, pulsewidth, frequency) channels, being preferable the solution with many channels. [0060] 5. Signal Conditioner

[0061] A signal conditioner picks-up the signals coming from the ENG, EMG electrodes, then amplifies and filters them. This device has to be connected wireless or wired with the ENG, EMG electrodes. Then, it has to send the amplified signals to the processor. The signal amplifier can be implantable or external to the body. [0062] 6. Microprocessor

[0063] A microprocessor unit will manage: [0064] i) a) The acquisition of biological signals (muscular and neural) b) processing and c) decoding the voluntary intention of user, in order to control the motion of the robotic limb. [0065] ii) a) The acquisition of robotic limb sensors readouts, b) Processing and c) Encoding of the information, in order to control the stimulator for the sensory restoration.

Methods

[0066] The system schematically illustrated in FIG. 4 is described below. [0067] 1. Hybrid Control of the artificial limb

[0068] The hybrid control strategy of the artificial limb is composed of two steps that could work as independent or synergistic modules: [0069] i) Electromyographic (EMG) control module: the control is implemented through a classifier, which recognizes the EMG activity at fixed steps (for example 100 ms) and decode the type of grasp/movement that the user wants to perform. The amputee can in every moment change the muscular activity and switch from one to another type of grasp/movement. This control should work with different electrodes for EMG recordings that could be surface electrodes, surface electrodes arrays or intramuscular electrodes. [0070] ii) Electroneurographic (ENG) control module: the ENG signal is used in combination with the EMG module to control the grasping force/velocity of the selected grasp by working in synergy with it. [0071] iii) In the case of the absence or impossibility of recording the ENG signal, the velocity of the motors will be controlled by the EMG control module. [0072] 2. Transfer function to the Nervous System.

[0073] The readout of the sensors embedded in the prosthetic limb or the glove (or sock) is used as an input for the delivery of afferent neural stimulation. The system can select and modulate 4 (or more) different characteristics of sensations: [0074] i) type of sensation [0075] ii) strength (intensity) [0076] iii) location over phantom limb [0077] iv) spatial extension

Type of Sensation

[0078] The type of sensation is selected by the stimulation of particular active sites of the peripheral nerve interface. In the case of multi- and intra-fascicular electrodes each usable active site will in fact elicit a specific type of sensation. These sensations could be touch/pressure and proprioception among others.

Strength of Sensation

[0079] The strength of sensation can be modulated through the use of charge (amplitude/pulse width), frequency and pattern of stimulus time occurrence modulation. In the case of the charge modulation an intrafascicular device ensure a quasi-linear dynamic relationship strength-amplitude.

[0080] The relationship between the tension-touch hand sensors readout and the charge of the stimulation current pulses could be implemented (nut not limited to) as follows:

c=(c.sub.maxc.sub.min)*(ss.sub.15)/(s.sub.75s.sub.15)+c.sub.min, when s.sub.15ss.sub.75;

c=0, when s.sub.15<s;

c=c.sub.max, when s>s.sub.75;

where:

[0081] c is the amplitude of stimulation current,

[0082] s is the sensor readout,

[0083] s.sub.15 and s.sub.75 represent 15% and 75% respectively of the maximum range of the sensor readout, which characterize, respectively, the contact point of the robotic hand with an object and a value tuned to exploit the full range of sensations for all objects, c.sub.min and c.sub.max are the stimulation current amplitudes that elicited, respectively, the minimum and the maximum (i.e., below pain threshold) touch sensations, as reported by the subject. The frequency of the stimulation in this example is fixed.

[0084] An analogous relation can be implemented in the case of frequency modulation:

f=(fmaxfmin)*(ss15)/(s75s15)+fmin, when s15ss75;

f=0, when s15<s;

f=cmax, when s>s75;

[0085] In this case f is the frequency of the stimulation. The current amplitude is fixed and set to a value that elicits a sensation in the middle between minimum and below pain threshold perceived sensations.

[0086] In the case of the modulation of the time occurrence (TO) of the stimulation pattern, several relations (sensors readouts-TO) can be implemented. The TO is defined as the time delay between a pattern of stimulation and the successive one.

[0087] A linear (sensors readouts-TO) relation is defined as follows:

TO=(TOmaxTOmin)*(ss15)/(s75s15)+TOmax, s15ss75;

No stimulation, s15<s;

TO=TOmax, s>s75;

[0088] In this case, the current amplitude is fixed and set to a value that elicits a sensation in the middle between minimum and below pain threshold perceived sensation.

[0089] In all the presented cases, other possible relations can be implemented between the sensors readouts and the stimulation (e.g. sigmoid or Poisson relations). Moreover, similar relations can be implemented in the case a voltage stimulator and other types of sensors are used in the bidirectional prosthesis.

[0090] Charge, frequency and pattern time occurrence modulation can be implemented and exploited together or separately in the bidirectional prosthesis.

Location Over Phantom Limb

[0091] This characteristic is controlled by the spatial location of the electrodes: different active sites of the electrode, debt to transversal somato-topography of peripheral nerves, will elicit the sensations over different areas of the missing limb. Intra-fascicular electrodes ensure a localized sensation per active site, being able to stimulate single nerve fascicles, thus each active site could control a specific and delimited sensory area. For example in the case of hand/arm amputation an electrode implanted in the residual median nerve will elicit the sensations over first three fingers and underlying palm area. Electrode implanted in residual ulnar nerve will elicit the sensations over last two fingers and underlying palm area. Finally, electrode implanted in radial nerve will elicit sensations over wrist and dorsal hand. In the lower limb the sciatic nerve stimulation will enable for the coverage of the main part of the phantom foot sensations.

Spatial Extension

[0092] This characteristic is controlled by a combination of the spatial location and amplitude modulation of the active sites. Several active sites of electrode, that elicit different sensations, will be used together in multipolar stimulation strategies to move the sensation over different hand areas (e.g. the sensations elicited in thumb and index finger could be combined so to obtain the feeling of the palm that is under these two fingers). [0093] 3. Real-time integration microprocessor unit

[0094] The recording of biological signals, features extraction, and final decoding of the user intended grasp/movement will be done in parallel with sensors readout, and transformation for encoding of the sensation. All the computation should be performed in timing within 100 msec that is essential to be imperceptible to the user.

[0095] Of course the invention is not limited to the examples presented previously.

[0096] Any suitable highly selective neural fiber stimulation tool can be used, for instance the use of optogenetic technologies [26] or a combination of electrical and optical stimulation [27].

[0097] The number of EMG and/or sensory feedback electrodes is also not limited, the main objective being to provide a highly selective stimulation between two adjacent fascicules or between the axons located within the same fascicule.

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