WO1991017791A1 - Annular neural electrode - Google Patents

Annular neural electrode Download PDF

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Publication number
WO1991017791A1
WO1991017791A1 PCT/FR1991/000404 FR9100404W WO9117791A1 WO 1991017791 A1 WO1991017791 A1 WO 1991017791A1 FR 9100404 W FR9100404 W FR 9100404W WO 9117791 A1 WO9117791 A1 WO 9117791A1
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WO
WIPO (PCT)
Prior art keywords
annular
shape memory
neural
electrode
electrode according
Prior art date
Application number
PCT/FR1991/000404
Other languages
French (fr)
Inventor
Michel De Mendez
Sylvie Chincholle-Gamboa
Laurent Contardo
Original Assignee
Souriau & Cie
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Souriau & Cie filed Critical Souriau & Cie
Publication of WO1991017791A1 publication Critical patent/WO1991017791A1/en

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Classifications

    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A61B5/316—Modalities, i.e. specific diagnostic methods
    • A61B5/388—Nerve conduction study, e.g. detecting action potential of peripheral nerves
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/02—Details
    • A61N1/04—Electrodes
    • A61N1/05—Electrodes for implantation or insertion into the body, e.g. heart electrode
    • A61N1/0551—Spinal or peripheral nerve electrodes
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/24—Detecting, measuring or recording bioelectric or biomagnetic signals of the body or parts thereof
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61F—FILTERS IMPLANTABLE INTO BLOOD VESSELS; PROSTHESES; DEVICES PROVIDING PATENCY TO, OR PREVENTING COLLAPSING OF, TUBULAR STRUCTURES OF THE BODY, e.g. STENTS; ORTHOPAEDIC, NURSING OR CONTRACEPTIVE DEVICES; FOMENTATION; TREATMENT OR PROTECTION OF EYES OR EARS; BANDAGES, DRESSINGS OR ABSORBENT PADS; FIRST-AID KITS
    • A61F2210/00—Particular material properties of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof
    • A61F2210/0014—Particular material properties of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof using shape memory or superelastic materials, e.g. nitinol
    • A61F2210/0019—Particular material properties of prostheses classified in groups A61F2/00 - A61F2/26 or A61F2/82 or A61F9/00 or A61F11/00 or subgroups thereof using shape memory or superelastic materials, e.g. nitinol operated at only one temperature whilst inside or touching the human body, e.g. constrained in a non-operative shape during surgery, another temperature only occurring before the operation
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
    • A61N1/00—Electrotherapy; Circuits therefor
    • A61N1/02—Details
    • A61N1/04—Electrodes
    • A61N1/05—Electrodes for implantation or insertion into the body, e.g. heart electrode
    • A61N1/0551—Spinal or peripheral nerve electrodes
    • A61N1/0556—Cuff electrodes

Definitions

  • the present invention relates to an annular neural electrode intended to ensure, in a given operating temperature range, electrical contact at the periphery of a nerve so as to induce electrical excitation there.
  • the invention finds an advantageous application in the general field of electrical stimulation of the nerves allowing the control of muscles or other organs, and in particular when, following a rupture of the spine no nerve impulse is susceptible to reach the muscles of the lower limbs in order to set them in motion.
  • the electrode, object of the invention, associated with complex gait simulation programs must allow paraplegics to recover certain locomotion by replacing the nerve impulse lacking an electric excitation propagated in the nerve. himself.
  • neural electrode is meant an electrode intended to stimulate a muscle by means of the excitation of a nerve, in contrast to the epimysial electrodes which, directly applied to the envelope of the muscle, have a less selective action.
  • the electrode described above cannot react to a possible increase in the section of the nerve, which is then excessively constrained by the electrode and therefore definitively destroyed.
  • the technical problem to be solved by the object of the present invention is to produce an annular neural electrode conforming to the preamble which would make it possible to avoid, whatever the circumstances. excessive stress on the nerve in the electrode, which would also provide good mechanical strength.
  • the solution to the technical problem posed consists, according to the present invention, in that said electrode is made of a shape memory material capable of exhibiting, in said operating temperature range, a superelastic effect accompanying the transformation under stress of the phase austenitic in martensitic phase.
  • the annular neural electrode according to the invention can easily deform over a wide range of deformations, for example under the effect of an increase in the diameter of the nerve, without developing on the nerve strong stresses which would permanently damage it. Consequently, it is possible to provide, during the positioning of the electrode object of the invention around the nerve, a slightly tight contact but nevertheless much more adjusted than in the case of the electrodes known from the state of the art, knowing that in any event the stress will remain below the tolerable limit stress.
  • the annular neural electrode conforms to the invention has the additional advantage of a particularly easy installation by implementing the characteristic properties of shape memory materials.
  • the shape memory material is shaped so as to ensure electrical contact with said nerve in a shape memory state in the austenitic phase.
  • the electrode is brought to a low temperature in the martensitic phase, placed in the open position and engaged on the nerve. Then, by simple heating beyond the transition temperature to the austenitic phase, the electrode returns to the closed position in which it had been previously shaped.
  • said shape memory material is shaped so as to ensure electrical contact with said nerve in a first shape memory state, and to ensure the release and / or engagement of said electrode in a second state of shape memory.
  • Figure 1a is a side view of an annular neural electrode according to the invention.
  • Figure lb is a sectional view along line II-II of Figure l a.
  • Figure 2 is a stress-strain diagram of a shape memory material in the superelastic state.
  • Figure 3a is a side view of a first alternative embodiment of the electrode according to the invention.
  • Figure 3b is a sectional view along line II-II of Figure 3a.
  • Figure a is a side view of a second alternative embodiment of the electrode according to the invention.
  • Figure b is a side view along line II— II of Figure ⁇ + a.
  • Figure 5 is a front view showing a first mode of association of two electrodes according to Figure 1b.
  • Figure 6 is a front view showing a second mode of association of two electrodes according to Figure 1b.
  • Figure 7 is a front view of a double electrode according to the invention.
  • Figures la and lb show in a side view and in section an annular neural electrode intended to ensure, in a given operating temperature range, electrical contact at the periphery of a nerve 10 so as to induce an electrical excitation therein .
  • the electrode of Figures la and lb is made of a shape memory material capable of having, in the operating temperature range, a superelastic effect accompanying the transformation under stress of the austenitic phase in mantensitic phase.
  • a stress ⁇ / deformation ⁇ diagram representing this effect is given in FIG. 2. It can be seen on the diagram in FIG.
  • the operating temperature range of the electrode is chosen between the temperature A-- at the end of the austenitic transition and the temperature A-.
  • the temperature A p of the shape memory material must be taken at least equal to 42 ° C while the temperature A p at the end of the austenitic transition is chosen at most equal to 35 ° C.
  • the shape memory properties under the effect of temperature can be advantageously implemented in the operations aimed at placing the electrode according to the invention on the nerve and, possibly, at removing it .
  • the memory material forming the electrode is shaped so as to ensure electrical contact with the nerve 10 in a state of memory in austenitic shape. The positioning is then carried out as follows: the electrode is brought into the martensitic phase around 0 ° C. for example, which supposes that the temperature - at the end of the martensitic transition is close to 0 ° C., and conformed in the open position.
  • the electrode resumes under the effect of temperature warming the holding configuration which had been given to it initially in the austenitic phase, provided however that the temperature A-. at the start of the austenitic transition is greater than 0 ° C.
  • the shape memory material must be shaped so as to ensure electrical contact with the nerve in a first state of shape memory, and to ensure the release and / or engagement of the electrode in a second shape memory state.
  • the first and second shape memory states are defined respectively in the austenitic phase and in the martensitic phase. The passage from one to the other of the shape memory states can be effected in a reversible manner by the mere fact of crossing the transition temperature of the shape memory material.
  • the electrode according to the invention is subjected to an education process, examples of which are given in European patent application No. 0 161 952.
  • the electrode has on its outer part a sheath 21, for example made of bio-compatible silicone, making it possible to avoid contact between the tissues and the Ni-Ti alloy, for example, forming the 'electrode.
  • the polarization of said electrode is provided by a conductor 30.
  • the electrical connection with the nerve 10 is obtained by direct contact on the nerve of the shape memory material constituting the electrode. In order to further limit the harmful reactions which could occur between the material of the electrode and the biological medium, it is provided, as illustrated in FIGS.
  • FIGS. 4a and 4b illustrate an alternative embodiment of the electrode of FIGS. 3a and 3b in which the electrical contact zone 23 is composed of a plurality of conductive pads arranged annularly on the interior wall of the electrode.
  • FIGS. 4a and 4b illustrate an alternative embodiment of the electrode of FIGS. 3a and 3b in which the electrical contact zone 23 is composed of a plurality of conductive pads arranged annularly on the interior wall of the electrode.
  • FIG. 5 shows neural excitation devices composed essentially of two annular electrodes 20, 20 'intended to be brought to different electrical potentials so as to produce a longitudinal electrical excitation inside the nerve 10.
  • the embodiments of Figures 5 and 6 consist of two electrodes identical to that shown in Figures la and l b.
  • the conductors 30 and 30 ′ are united in the same insulating envelope 40 exiting at the end of the device, while in the example of FIG. 6, the envelope 50 exits between the two electrodes 20 and 20 '.
  • the insulating envelopes 40 and 50 are produced by epoxy resin as a coating.
  • FIG. 7 shows another neural excitation device which can be described by a double electrode formed in a single piece of two electrodes similar to those of FIGS. 4a and 4b which would be joined together so as not to form only one piece.
  • the conductors 30 and 30 ' are also combined in an insulating envelope 60 made of epoxy resin.

Abstract

Annular neural electrode for producing, in a given working temperature range, an electricl contact on the periphery of a nerve (10) such as to induce electrical excitation. In accordance with the invention, said electrode is made from a shape memory material capable of showing, in said working temperature range, a super elastic effect in conjunction with its transformation under stress from the austenitic phase to the martensitic phase. Application in electrical muscle stimulation.

Description

ELECTRODE NEURALE ANNULAIRE ANNULAR NEURAL ELECTRODE
La présente invention concerne une électrode neurale annulaire destinée à assurer, dans une gamme de température de fonctionnement donnée, un contact électrique à la périphérie d'un nerf de façon à y induire une excitation électrique. L'invention trouve une application avantageuse dans le domaine général de la stimulation électrique des nerfs permettant la commande de muscles ou d'autres organes, et notamment lorsque, à la suite d'une rupture de la colonne vertébrale aucun influx nerveux n'est susceptible de parvenir aux muscles des membres inférieurs afin de les mettre en mouvement. Dans ce cas, l'électrode, objet de l'invention, associée à des programmes complexes de simulation de la marche, doit permettre à des paraplégiques de recouvrer une certaines locomotion en substituant à l'influx nerveux manquant une excitation électrique propagée dans le nerf lui-même. Par électrode neurale, on entend une électrode destinée à stimuler un muscle par l'intermédiaire de l'excitation d'un nerf, par opposition aux électrodes épimysiales qui, directement appliquées sur l'enveloppe du muscle, ont une action moins sélective.The present invention relates to an annular neural electrode intended to ensure, in a given operating temperature range, electrical contact at the periphery of a nerve so as to induce electrical excitation there. The invention finds an advantageous application in the general field of electrical stimulation of the nerves allowing the control of muscles or other organs, and in particular when, following a rupture of the spine no nerve impulse is susceptible to reach the muscles of the lower limbs in order to set them in motion. In this case, the electrode, object of the invention, associated with complex gait simulation programs, must allow paraplegics to recover certain locomotion by replacing the nerve impulse lacking an electric excitation propagated in the nerve. himself. By neural electrode is meant an electrode intended to stimulate a muscle by means of the excitation of a nerve, in contrast to the epimysial electrodes which, directly applied to the envelope of the muscle, have a less selective action.
Une électrode conforme au prémabule est connue de l'article de P.R. Troy and J. Poyezdala intitulé "A bipolar cuff électrode for lower extremity functional electrical stimulation" paru dans IEEE/Ninth Annual Conférence of the Engineering in edicine and Biology Society ( 1987). L'électrode neurale annulaire décrite dans cet article est une pièce en forme de U en Dacron imprégnée de silicone sur laquelle sont disposées des électrodes de stimulation en platine, le nerf étant disposé à l'intérieur de la forme en U. Comme toutes les électrodes neurales, ce type d'électrode connue présente cependant des limitations liées au fait que, sous peine d'altérations irréversibles de la fonction, un nerf ne peut être soumis à une pression supérieure à 16 mmHg. En particulier, l'électrode décrite plus haut ne peut réagir à une éventuelle augmentation de la section du nerf, lequel se trouve alors contraint de manière excessive par l'électrode et donc définitivement détruit. D'autre part, afin précisément d'éviter que le nerf ne soit maintenu trop serré dans l'électrode, on prévoit généralement un ajustement assez lâche de l'électrode autour du nerf, ce qui a pour inconvénient de ne pas assurer un maintien mécanique et un contact électrique très sûrs et reproductibles.An electrode conforming to the preamble is known from the article by PR Troy and J. Poyezdala entitled "A bipolar cuff electrode for lower extremity functional electrical stimulation" published in IEEE / Ninth Annual Conference of the Engineering in edicine and Biology Society (1987). The annular neural electrode described in this article is a U-shaped piece of Dacron impregnated with silicone on which platinum stimulation electrodes are placed, the nerve being placed inside the U-shape. Like all electrodes However, this type of known electrode has limitations linked to the fact that, under pain of irreversible alterations in function, a nerve cannot be subjected to a pressure greater than 16 mmHg. In particular, the electrode described above cannot react to a possible increase in the section of the nerve, which is then excessively constrained by the electrode and therefore definitively destroyed. On the other hand, in order precisely to avoid that the nerve is kept too tight in the electrode, provision is generally made a fairly loose adjustment of the electrode around the nerve, which has the drawback of not ensuring very secure and reproducible mechanical maintenance and electrical contact.
Aussi, le problème technique à résoudre par l'objet de la présente invention est de réaliser une électrode neurale annulaire conforme au préambule qui permettrait d'éviter, quelles que soient les circonstances. une trop forte contrainte du nerf dans l'électrode et qui offrirait également une bonne tenue mécanique.Also, the technical problem to be solved by the object of the present invention is to produce an annular neural electrode conforming to the preamble which would make it possible to avoid, whatever the circumstances. excessive stress on the nerve in the electrode, which would also provide good mechanical strength.
La solution au problème technique posé consiste, selon la présente invention, en ce que ladite électrode est réalisée en un matériau à mémoire de forme susceptible de présenter, dans ladite gamme de température de fonctionnement, un effet superélastique accompagnant la transformation sous contrainte de la phase austénitique en phase martensitique.The solution to the technical problem posed consists, according to the present invention, in that said electrode is made of a shape memory material capable of exhibiting, in said operating temperature range, a superelastic effect accompanying the transformation under stress of the phase austenitic in martensitic phase.
On sait, en effet, qu'il est possible, à des températures comprises entre la température A-- de fin de transition austénitique et une température A,- , de faire passer, et inversement, un matériau à mémoire σ de forme de la phase austénitique à la phase martensitique par application ou relâchement d'une contrainte mécanique. Ce passage réversible s'accompagne d'un important effet superélastique caractérisé par un domaine où la contrainte reste relativement faible et constante, c'est-à-dire quasi indépendante de la déformation du matériau.We know, in fact, that it is possible, at temperatures between the temperature A-- at the end of the austenitic transition and a temperature A, -, to pass, and vice versa, a material with memory σ of shape of the austenitic phase to the martensitic phase by application or relaxation of a mechanical stress. This reversible passage is accompanied by a significant superelastic effect characterized by an area where the stress remains relatively low and constant, that is to say almost independent of the deformation of the material.
Aussi, l'électrode neurale annulaire selon l'invention peut se déformer facilement sur une grande plage de déformations, par exemple sous l'effet d'une augmentation du diamètre du nerf, sans développer sur le nerf de fortes contraintes qui le léseraient définitivement. En conséquence, on peut prévoir, lors de la mise en place de l'électrode objet de l'invention autour du nerf, un contact légèrement serré mais néanmoins beaucoup plus ajusté que dans le cas des électrodes connues de l'état de la technique, sachant qu'en tout état de cause la contrainte restera inférieure à la contrainte limite tolérable.Also, the annular neural electrode according to the invention can easily deform over a wide range of deformations, for example under the effect of an increase in the diameter of the nerve, without developing on the nerve strong stresses which would permanently damage it. Consequently, it is possible to provide, during the positioning of the electrode object of the invention around the nerve, a slightly tight contact but nevertheless much more adjusted than in the case of the electrodes known from the state of the art, knowing that in any event the stress will remain below the tolerable limit stress.
D'autre part, l'électrode neurale annulaire conforme à l'invention présente l'avantage supplémentaire d'une mise en place particulièrement aisée en mettant en oeuvre les propriétés caractéristiques des matériaux à mémoire de forme. A cet effet, il est prévu que le matériau à mémoire de forme est conformé de façon à assurer le contact électrique avec ledit nerf dans un état de mémoire de forme en phase austénitique. Dans ce mode de réalisation, l'électrode est amenée à basse température en phase martensitique, mise en position ouverte et engagée sur le nerf. Puis, par simple réchauffement au-delà de la température de transition jusqu'en phase austénitique, l'électrode reprend la position fermée dans laquelle elle avait été préalablement conformée.On the other hand, the annular neural electrode conforms to the invention has the additional advantage of a particularly easy installation by implementing the characteristic properties of shape memory materials. To this end, it is provided that the shape memory material is shaped so as to ensure electrical contact with said nerve in a shape memory state in the austenitic phase. In this embodiment, the electrode is brought to a low temperature in the martensitic phase, placed in the open position and engaged on the nerve. Then, by simple heating beyond the transition temperature to the austenitic phase, the electrode returns to the closed position in which it had been previously shaped.
Bien entendu, au lieu d'utiliser le simple effet de mémoire de forme, on peut, de manière avantageuse, mettre en oeuvre le double effet de mémoire. Dans ce cas, ledit matériau à mémoire de forme est conformé de façon à assurer le contact électrique avec ledit nerf dans un premier état de mémoire de forme, et à assurer le dégagement et/ou l'engagement de ladite électrode dans un deuxième état de mémoire de forme. Après avoir soumis l'électrode selon l'invention à un processus d'éducation du type de ceux décrits dans la demande de brevet européen n° 0 161 952, il est possible d'obtenir que le passage du premier état de mémoire de forme au deuxième état de mémoire de forme est effectué de façon réversible du seul fait du franchissement de la température de transition dudit matériau à mémoire de forme.Of course, instead of using the simple shape memory effect, it is advantageous to use the double memory effect. In this case, said shape memory material is shaped so as to ensure electrical contact with said nerve in a first shape memory state, and to ensure the release and / or engagement of said electrode in a second state of shape memory. After having subjected the electrode according to the invention to a process of education of the type of those described in European patent application No. 0 161 952, it is possible to obtain that the transition from the first state of shape memory to second shape memory state is effected in a reversible manner by the mere fact of crossing the transition temperature of said shape memory material.
La description qui va suivre en regard des dessins annexés, donnés à titre d'exemples non limitatifs, fera bien comprendre en quoi consiste l'invention et comment elle peut être réalisée.The description which follows with reference to the appended drawings, given by way of nonlimiting examples, will make it clear what the invention consists of and how it can be implemented.
La figure l a est une vue de côté d'une électrode neurale annulaire conforme à l'invention.Figure 1a is a side view of an annular neural electrode according to the invention.
La figure l b est une vue en coupe selon la ligne II-II de la figure l a. La figure 2 est un diagramme contrainte-déformation d'un matériau à mémoire de forme à l'état superélastique. La figure 3a est une vue de côté d'une première variante de réalisation de l'électrode selon l'invention.Figure lb is a sectional view along line II-II of Figure l a. Figure 2 is a stress-strain diagram of a shape memory material in the superelastic state. Figure 3a is a side view of a first alternative embodiment of the electrode according to the invention.
La figure 3b est une vue en coupe selon la ligne II-II de la figure 3a. La figure a est une vue de côté d'une deuxième variante de réalisation de l'électrode selon l'invention.Figure 3b is a sectional view along line II-II of Figure 3a. Figure a is a side view of a second alternative embodiment of the electrode according to the invention.
La figure b est une vue de côté selon la ligne II— II de la figure <+a.Figure b is a side view along line II— II of Figure <+ a.
La figure 5 est une vue de face montrant un premier mode d'association de deux électrodes conformes à la figure 1b.Figure 5 is a front view showing a first mode of association of two electrodes according to Figure 1b.
La figure 6 est une vue de face montrant un deuxième mode d'association de deux électrodes conformes à la figure 1b.Figure 6 is a front view showing a second mode of association of two electrodes according to Figure 1b.
La figure 7 est une vue de face d'une électrode double conforme à l'invention. Les figures la et lb montrent sur une vue de côté et en coupe une électrode neurale annulaire destinée à assurer, dans une gamme de température de fonctionnement donnée, un contact électrique à la périphérie d'un nerf 10 de façon à y induire une excitation électrique. Selon une caractéristique avantageuse de l'invention, l'électrode des figures la et l b est réalisée en un matériau à mémoire de forme susceptible de présenter, dans la gamme de température de fonctionnement, un effet superélastique accompagnant la transformation sous contrainte de la phase austénitique en phase mantensitique. Un diagramme contrainte σ / déformation ε représentant cet effet est donné à la figure 2. On peut voir sur le diagramme de la figure 2 qu', au-dessous d'une température Ap au-delà de laquelle la transformation sous contrainte austénite-martensite n'est plus possible, une contrainte appliquée à un matériau à mémoire de forme à l'état austénitique provoque, à partir d'une contrainte limite σ , la formation d'une phase martensitique dont l'apparition s'accompagne de profondes modifications des propriétés élastiques de l'alliage à mémoire de forme. La figure 2 montre en effet que le matériau présente alors un module d'élasticité nettement réduit caractérisé par le fait qu'une variation relativement faible de la contrainte appliquée produit une déformation qui peut être notable. Inversement, le matériau à mémoire de forme à l'état superéiastique ne développe pratiquement pas de contrainte en réaction à une déformation imposée, même importante. C'est cette dernière propriété qui est mise à profit par l'électrode neurale annulaire de l'invention. Dans ce but, la gamme de température de fonctionnement de l'électrode est choisie entre la température A-- de fin de transition austénitique et la température A- . Dans ces conditions, on peut observer que si la section du nerf 10 est amenée à augmenter, l'électrode montrée aux figures l a et l b pourra se déformer en conséquence sans exercer sur le nerf 10 de contrainte supplémentaire excessive qui risquerait de l'endommager de façon irréversible. Les risques de destruction du nerf provoquée par une force de pression trop grande étant considérablement limités, il est permis de prévoir qu'au repos le nerf puisse être soumis à une légère contrainte assurant le maintien mécanique nécessaire à un bon contact électrique.Figure 7 is a front view of a double electrode according to the invention. Figures la and lb show in a side view and in section an annular neural electrode intended to ensure, in a given operating temperature range, electrical contact at the periphery of a nerve 10 so as to induce an electrical excitation therein . According to an advantageous characteristic of the invention, the electrode of Figures la and lb is made of a shape memory material capable of having, in the operating temperature range, a superelastic effect accompanying the transformation under stress of the austenitic phase in mantensitic phase. A stress σ / deformation ε diagram representing this effect is given in FIG. 2. It can be seen on the diagram in FIG. 2 that, below a temperature Ap beyond which the transformation under austenite-martensite stress is no longer possible, a stress applied to a material with shape memory in the austenitic state causes, from a limiting stress σ, the formation of a martensitic phase whose appearance is accompanied by profound modifications of the elastic properties of the shape memory alloy. Figure 2 shows that the material then has a markedly reduced modulus of elasticity characterized by the fact that a relatively small variation in the applied stress produces a deformation which can be significant. Conversely, the shape memory material in the superiastic state develops practically no stress in reaction to an imposed deformation, even significant. It is this latter property which is taken advantage of by the annular neural electrode of the invention. For this purpose, the operating temperature range of the electrode is chosen between the temperature A-- at the end of the austenitic transition and the temperature A-. Under these conditions, it can be observed that if the section of the nerve 10 is caused to increase, the electrode shown in FIGS. 1 a and 1 b may be deformed as a result without exerting on the nerve 10 excessive excessive stress which would risk damaging it. irreversible. The risks of destruction of the nerve caused by too great a pressing force being considerably limited, it is allowed to provide that at rest the nerve can be subjected to a slight stress ensuring the mechanical maintenance necessary for good electrical contact.
Pour un domaine de température de fonctionnement compris entre 35°C et 2°C, la température Ap du matériau à mémoire de forme doit être prise au moins égale à 42°C tandis que la température Ap de fin de transition austénitique est choisie au plus égale à 35°C.For an operating temperature range between 35 ° C and 2 ° C, the temperature A p of the shape memory material must be taken at least equal to 42 ° C while the temperature A p at the end of the austenitic transition is chosen at most equal to 35 ° C.
De façon plus particulière, les propriétés de mémoire de forme sous l'effet de la température peuvent être avantageusement mises en oeuvre dans les opérations visant à placer l'électrode selon l'invention sur le nerf et, éventuel lement, à l'en retirer. Dans le cadre d'une utilisation de l'effet de mémoire simple, le matériau à mémoire rie forme constituant l'électrode est conformé de façon à assurer le contact électrique avec le nerf 10 dans un état de mémoire de forme en hase austénitique. La mise en place s'effectue alors de la manière suivante : l 'électrode est amenée en phase martensitique autour de 0°C par exemple, ce qui suppose que la température - de fin de transition martensitique soit voisine de 0°C, et conformée en position ouverte. Puis, après mise en position autour du nerf, l'électrode reprend sous l'effet du réchauffement de température la configuration de maintien qui lui avait été donnée initialement en phase austénitique, à condition toutefois que la température A-. de début de transition austénitique soit supérieure à 0°C. Si le double effet de mémoire est utilisé, le matériau à mémoire de forme doit être conformé de façon à assurer le contact électrique avec le nerf dans un premier état de mémoire de forme, et à assurer le dégagement et/ou l'engagement de l'électrode dans un deuxième état de mémoire de forme. De façon pratique, les premier et deuxième états de mémoire de forme sont respectivement définis en phase austénitique et en phase martensitique. Le passage de l'un à l'autre des états de mémoire de forme peut être effectué de façon réversible du seul fait du franchissement de la température de transition du matériau à mémoire de forme. A cet effet, l'électrode selon l'invention est soumise à un processus d'éducation dont des exemples sont donnés dans la demande de brevet européen n° 0 161 952.More particularly, the shape memory properties under the effect of temperature can be advantageously implemented in the operations aimed at placing the electrode according to the invention on the nerve and, possibly, at removing it . In the context of using the simple memory effect, the memory material forming the electrode is shaped so as to ensure electrical contact with the nerve 10 in a state of memory in austenitic shape. The positioning is then carried out as follows: the electrode is brought into the martensitic phase around 0 ° C. for example, which supposes that the temperature - at the end of the martensitic transition is close to 0 ° C., and conformed in the open position. Then, after positioning around the nerve, the electrode resumes under the effect of temperature warming the holding configuration which had been given to it initially in the austenitic phase, provided however that the temperature A-. at the start of the austenitic transition is greater than 0 ° C. If the double memory effect is used, the shape memory material must be shaped so as to ensure electrical contact with the nerve in a first state of shape memory, and to ensure the release and / or engagement of the electrode in a second shape memory state. In practice, the first and second shape memory states are defined respectively in the austenitic phase and in the martensitic phase. The passage from one to the other of the shape memory states can be effected in a reversible manner by the mere fact of crossing the transition temperature of the shape memory material. To this end, the electrode according to the invention is subjected to an education process, examples of which are given in European patent application No. 0 161 952.
La figure la montre par ailleurs que l'électrode présente sur sa partie extérieure une gaine 21, par exemple en silicone bio-compatible, permettant d'éviter le contact entre les tissus et l'alliage de Ni-Ti, par exemple, formant l'électrode. La polarisation de ladite électrode est assurée par un conducteur 30. Dans ce mode de réalisation, la liaison électrique avec le nerf 10 est obtenu par contact direct sur le nerf du matériau à mémoire de forme constituant l'électrode. De façon à limiter davantage les réactions néfastes qui pourraient se reproduire entre le matériau de l'électrode et le milieu biologique, il est prévu, comme l'illustrent les figures 3a et 3b, que la partie intérieure de l'électrode soit également revêtue d'une gaine isolante 22 sur laquelle est rapportée une zone de contact formée, dans l'exemple des figures 3c et 3b, par un fil conducteur annulaire 23 relié au conducteur 30. Avantageusement, le fil conducteur 23 est en platine dont la compatibilité biologique est bien plus grande que celle de l'alliage Ni-Ti. Les figures 4a et 4b illustrent une variante de réalisation de l'électrode des figures 3a et 3b dans laquelle la zone de contact 23 électrique est composée d'une pluralité de pastilles conductrices disposées de façon annulaire sur la paroi intérieure de l'électrode. Les figures 5, 6 et 7 montrent des dispositifs d'excitation neurale composés en substance de deux électrodes annulaires 20, 20' destinées à être portées à des potentiels électriques différents de façon à produire une excitation électrique longitudinale à l'intérieur du nerf 10. Les modes de réalisation des figures 5 et 6 sont constitués de deux électrodes identiques à celle représentée sur les figures l a et l b. Dans le cas de la figure 5, les conducteurs 30 et 30' sont réunis dans une même enveloppe isolante 40 sortant en bout du dispositif, tandis que dans l'exemple de la figure 6, l'enveloppe 50 sort entre les deux électrodes 20 et 20'. Les enveloppes isolantes 40 et 50 sont réalisées par de la résine époxy en enrobage.The figure also shows that the electrode has on its outer part a sheath 21, for example made of bio-compatible silicone, making it possible to avoid contact between the tissues and the Ni-Ti alloy, for example, forming the 'electrode. The polarization of said electrode is provided by a conductor 30. In this embodiment, the electrical connection with the nerve 10 is obtained by direct contact on the nerve of the shape memory material constituting the electrode. In order to further limit the harmful reactions which could occur between the material of the electrode and the biological medium, it is provided, as illustrated in FIGS. 3a and 3b, that the interior part of the electrode is also coated with 'an insulating sheath 22 to which is attached a contact zone formed, in the example of Figures 3c and 3b, by an annular conductive wire 23 connected to the conductor 30. Advantageously, the conductive wire 23 is made of platinum whose biological compatibility is much larger than that of the Ni-Ti alloy. FIGS. 4a and 4b illustrate an alternative embodiment of the electrode of FIGS. 3a and 3b in which the electrical contact zone 23 is composed of a plurality of conductive pads arranged annularly on the interior wall of the electrode. FIGS. 5, 6 and 7 show neural excitation devices composed essentially of two annular electrodes 20, 20 'intended to be brought to different electrical potentials so as to produce a longitudinal electrical excitation inside the nerve 10. The embodiments of Figures 5 and 6 consist of two electrodes identical to that shown in Figures la and l b. In the case of FIG. 5, the conductors 30 and 30 ′ are united in the same insulating envelope 40 exiting at the end of the device, while in the example of FIG. 6, the envelope 50 exits between the two electrodes 20 and 20 '. The insulating envelopes 40 and 50 are produced by epoxy resin as a coating.
La figure 7 montre un autre dispositif d'excitation neurale qui peut être décrit par une électrode double formée en un seul tenant de deux électrodes similaires à celles des figures 4a et 4b qui seraient accolées l'une à l'autre de manière à ne former qu'une seule pièce. Les conducteurs 30 et 30' sont également réunis dans une enveloppe isolante 60 en résine époxy. FIG. 7 shows another neural excitation device which can be described by a double electrode formed in a single piece of two electrodes similar to those of FIGS. 4a and 4b which would be joined together so as not to form only one piece. The conductors 30 and 30 'are also combined in an insulating envelope 60 made of epoxy resin.

Claims

REVENDICATIONS l. Electrode neurale annulaire destinée à assurer, dans une gamme de température de fonctionnement donnée, un contact électrique à la périphérie d'un nerf ( 10) de façon à y induire une excitation électrique, caractérisée en ce que ladite électrode est réalisée en un matériau à mémoire de forme susceptible de présenter, dans ladite gamme de température de fonctionnement, un effet superélastique accompagnant la transformation sous contrainte de la phase austénitique en phase martensitique. CLAIMS l. Annular neural electrode intended to ensure, in a given operating temperature range, an electrical contact at the periphery of a nerve (10) so as to induce an electrical excitation therein, characterized in that said electrode is made of a material with shape memory capable of exhibiting, in said operating temperature range, a superelastic effect accompanying the transformation under stress of the austenitic phase into the martensitic phase.
2. Electrode neurale annulaire selon la revendication 1, caractérisée en ce que la température A_ dudit matériau à mémoire de forme, au-delà de laquelle la transition sous contrainte austénite- martensite est impossible, est au moins égale à 42°C.2. annular neural electrode according to claim 1, characterized in that the temperature A_ of said shape memory material, beyond which the transition under austenite-martensite stress is impossible, is at least equal to 42 ° C.
3. Electrode neurale annulaire selon l'une des revendications 1 ou 2, caractérisée en ce que la température Ap de fin de transition austénitique dudit matériau à mémoire de forme est au plus égale à 35°C.3. annular neural electrode according to one of claims 1 or 2, characterized in that the temperature A p of end of austenitic transition of said shape memory material is at most equal to 35 ° C.
4. Electrode neurale annulaire selon l'une quelconque des revendications 1 à 3, caractérisée en ce que ledit matériau à mémoire de forme est conformé de façon à assurer le contact électrique avec ledit nerf (10) dans un état de mémoire de forme en phase austénitique.4. Annular neural electrode according to any one of claims 1 to 3, characterized in that said shape memory material is shaped so as to ensure electrical contact with said nerve (10) in a phase shape memory state austenitic.
5. Electrode neurale annulaire selon l'une quelconque des revendications 1 à 3, caractérisé en ce que ledit matériau à mémoire de forme est conformé de façon à assurer le contact électrique avec ledit nerf ( 10) dans un premier état de mémoire de forme, et à assurer le dégagement et/ou l'engagement de ladite électrode par déformation à l'état marten¬ sitique.5. annular neural electrode according to any one of claims 1 to 3, characterized in that said shape memory material is shaped so as to ensure electrical contact with said nerve (10) in a first shape memory state, and to ensure the release and / or engagement of said electrode by deformation in the marten¬ sitic state.
6. Electrode neurale annulaire selon la revendication 5, caractérisée en ce que l'électrode a subit un traitement d'éducation lui conférant un second état de mémoire de forme et que le passage du premier état de mémoire de forme au deuxième état de mémoire de forme est effectué de façon réversible du seul fait du franchissement de la température de transition dudit matériau à mémoire de forme. 6. Annular neural electrode according to claim 5, characterized in that the electrode has undergone an education treatment conferring on it a second state of shape memory and that the passage from the first state of shape memory to the second state of memory shape is carried out in a reversible manner by the mere fact of crossing the transition temperature of said shape memory material.
7. Electrode neurale annulaire selon l'une quelconque des revendications 4 à 6, caractérisée en ce que la température p de fin de transition martensitique dudit matériau à mémoire de forme est voisine de7. annular neural electrode according to any one of claims 4 to 6, characterized in that the temperature p at the end of the martensitic transition of said shape memory material is close to
Q°C, et en ce que la température A-, de début de transition austénitique correspondante est supérieure à 0°C.Q ° C, and in that the temperature A-, at the start of the corresponding austenitic transition is greater than 0 ° C.
8. Electrode neurale annulaire selon l'une quelconque des revendications 1 à 7, caractérisée en ce qu'elle présente une partie extérieure revêtue d'une gaine isolante (21 ).8. Annular neural electrode according to any one of claims 1 to 7, characterized in that it has an outer part coated with an insulating sheath (21).
9. Electrode neurale annulaire selon la revendication 8, caractérisée en ce qu'elle présente une partie intérieure de contact munie d'une gaine isolante (22) et d'au moins une zone de contact (23) rapportée sur ladite gaine isolante.9. annular neural electrode according to claim 8, characterized in that it has an inner contact part provided with an insulating sheath (22) and at least one contact zone (23) attached to said insulating sheath.
10. Electrode neurale annulaire selon la revendication 9, caractérisé en ce que ladite zone de contact (23) est un fil conducteur annulaire.10. Annular neural electrode according to claim 9, characterized in that said contact zone (23) is an annular conducting wire.
1 1. Electrode neurale annulaire selon la revendication 9, caractérisée en ce que ladite zone de contact (23) est constituée par une pluralité de pastilles conductrices disposées de façon annulaire.1 1. annular neural electrode according to claim 9, characterized in that said contact zone (23) consists of a plurality of conductive pads arranged in an annular manner.
12. Dispositif d'excitation neurale, caractérisé en ce qu'il est constitué par deux électrodes neurales annulaires (20, 20') selon l'une quelconque des revendications 1 à 1 1, présentant chacune un conducteur (30, 30') de polarisation, lesdits conducteurs de polarisation étant réunis dans une même enveloppe isolante (40) en bout dudit dispositif d'excita¬ tion. 12. Neural excitation device, characterized in that it consists of two annular neural electrodes (20, 20 ') according to any one of claims 1 to 1 1, each having a conductor (30, 30') of polarization, said polarization conductors being united in the same insulating envelope (40) at the end of said excitation device.
13. Dispositif d'excitation neurale, caractérisé en ce qu'il est constitué par deux électrodes neurales annulaires (20, 20') selon l'une quelconques des revendications 1 à U, présentant chacune un conducteur (30, 30') de polarisation, lesdits conducteurs de polarisation étant réunis dans une même enveloppe isolante (50) située entre les deux électrodes (20, 20').13. Neural excitation device, characterized in that it is constituted by two annular neural electrodes (20, 20 ') according to any one of claims 1 to U, each having a polarization conductor (30, 30') , said polarization conductors being joined in the same insulating envelope (50) located between the two electrodes (20, 20 ').
14. Dispositif d'excitation neurale, caractérisé en ce qu'il est constitué par une électrode double formée, en un seul tenant, de deux électrodes selon l'une quelconque des revendications 9 à 1 1 , accolées. 14. Neural excitation device, characterized in that it consists of a double electrode formed, in one piece, of two electrodes according to any one of claims 9 to 1 1, joined.
PCT/FR1991/000404 1990-05-21 1991-05-21 Annular neural electrode WO1991017791A1 (en)

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FR2662084B1 (en) 1995-04-21
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CN1060219A (en) 1992-04-15
CN1025285C (en) 1994-07-06

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