Patent Application
20140094873
The invention relates to the field of medical devices, specifically the invention provides a footwear product for use in Functional Electrical Stimulation (FES) or Functional Electrical Therapy (FET).
Functional Electric Stimulation FES or Functional Electric Therapy FET is well known to assist patients in walking. For example the Ph.D. thesis “Modulation of the nociceptive withdrawal reflex and its use in rehabilitation of gait of stroke patients”, Aalborg University 2009, by one of the inventors, Jonas Emborg describes reflex-based gait training where a painful electric stimulation on the patient's foot sole helps the patient to move his/her leg and thus initiate a step due to the evoked withdrawal reflex. This provides a helpful tool to enable gait training of patients being partially or completely immobile due to a hemiparetic condition caused by a stroke or traumatic brain injury which has resulted in damage of an area of their brain. Such patients have a significant better chance of rehabilitation if intensive gait training is initiated within 3 months after the stroke. In this early period the brain is especially suited to regenerate/relearn the ability to control the muscles, if the sufficient sensory, learning input is provided, i.e. by completing functionally adequate gait training.
Further references from the inventors are:
“Design and test of a novel closed-loop system that exploits the nociceptive withdrawal reflex for swing phase support of the hemiparetic gait”, J. Emborg, Z. Matja{hacek over (c)}ić, J. D. Bendtsen, E. G. Spaich, I. Cikajlo, N. Goljar, O.K. Andersen. IEEE Transactions on Biomedical Engineering. vol. 58, no. 4, pp. 960-970, April 2011. DOI:10.1109/TBME.2010.2096507
“Withdrawal reflex responses evoked by repetitive painful stimulation delivered on the sole of the foot during late stance: site, phase, and frequency modulation”, E. G. Spaich, J. Emborg, T. Collet, L. Arendt-Nielsen, and O. K. Andersen, Exp. Brain Res., vol. 194, no. 3, pp. 359-368, April 2009
“Withdrawal reflexes examined during human gait by ground reaction forces: site and gait phase dependency”, J. Emborg, E. G. Spaich, and O. K. Andersen, Med. Biol. Eng. Comput. 2009; vol. 4, pp. 29-39, January 2009
“Novel method exploiting the nociceptive withdrawal reflexes in rehabilitation of hemiplegic gait” Emborg, J.; Bendtsen, J. D.; Spaich, E. G.; Andersen, O. K., 2009. s. 84-87 World Congress on Medical Physics and Biomedical Engineering, Munich, Germany, 7-12 Sep. 2009, International Federation for Medical and Biological Engineering Proceedings. 25. IX
Laboratory experiments with the above-mentioned reflex-based gait training can be performed using electric stimulation applied by means of adhesive electrodes manually attached to the patient's foot, e.g. electrodes as used for ECG monitoring can be used. However, for practical application of the method several electrodes are used, and thus in a physiotherapy clinic or at a hospital, time is wasted on mounting and taking off the equipment instead of providing actual gait training for a patient.
Therefore, following the above description, there is a need for a product to facilitate practical and easy application of painful electrical stimulations of the person's foot for reflex-based gait training.
In a first aspect, the invention provides a product shaped to fit onto a person's foot sole, the product comprising
a platform of a flexible and electrically isolating material,
a plurality of separate stimulation electrodes each having an adhesive stimulation area of at least 1 cm2, wherein the stimulation electrodes are spatially distributed on the platform so as to be able to stimulate different zones of the person's foot sole during normal use,
at least one electrically conducting and adhesive ground plane electrode for contacting the person's foot, wherein a total area of the ground plane electrode is at least 10 times an area of one stimulation electrode,
an electric interface comprising a plug or socket with externally accessible electrical connectors so as to allow external individual electrical access to the plurality of stimulation electrode areas and to the ground plane electrode, and
a set of electrical conductors for interconnecting the plurality of stimulation electrodes and the ground plane electrode with the electric connectors of the electric interface, wherein the set of electrical conductors are arranged to withstand a voltage of more than 200 V, e.g. more than 400 V, between the ground plane electrode and the plurality of stimulation electrodes.
Such product, e.g. in the form of a disposable sole for a shoe, is suitable in practical gait training therapy because the stimulation equipment necessary only needs to be plugged onto the electric interface of such product to initiate a gait therapy session. Time consuming individual matching and mounting of stimulation electrodes, often several electrodes, is eliminated, since the product can be manufactured in different sizes thus fitting onto the person's foot without any individual electrode positioning considerations. The product needs to be mounted on the foot sole of the person, and the electric interface needs to be connected to the control system serving to apply the stimulation signal, e.g. in the form of a portable control device carried in the person's belt or the like which may then be wired or wirelessly connected to a stationary or laptop computer system. It is possible to manufacture the product at a low price, thus allowing the product to be used only once, thereby ensuring a high hygienic level without the need for cleaning of the equipment between two persons using the gait training equipment.
The invention can be seen as a product specific to be used primarily, but not exclusively, in connection with the Functional Electric Therapy, FET. The technology has also potential for being used in relation to a diagnostic tool that quantifies central sensitization in relation to chronic pain. This has the application to diagnose chronic pain patients—a large and until now unsolved problem—by assessing expanded reflex receptive fields via distributed electrical stimulations. Stimulations are delivered to different sites on the sole of the foot with the intent to assess spatial variation in withdrawal reflex sensitivity. Also, here a practical method of mounting several electrodes are needed to reduce the time for donning and doffing equipment.
Furthermore, in embodiments with many spatially separated stimulation electrodes, the best possible electrical stimulation of the individual person becomes possible irrespective of individual spatial differences in persons' sensitivities. The computer algorithm can take into account utilization of the best possible stimulation positions based on a feedback loop indicating the resulting swing of the leg and activating the most appropriate stimulation electrodes accordingly. The fact that the product is capable of handling 200 V, preferably also more than 400 V, or more, allows for efficient powerful stimulation, and the defined area difference between ground plane electrode and stimulation electrodes ensures that the intentional withdrawal reflex provoking sensation is obtained when a suitable electric stimulation signal is applied.
In versions with a special electric interface plug, a high safety can be obtained since the risk is minimized that wrong equipment is connected to the product.
The product may be in the form of a more or less simple footwear product, and especially the product may be: 1) a replaceable insole arranged to fit into a shoe, 2) a slipper, or 3) a shoe. The platform may form part of a footwear, such as a shoe, or a slipper.
In one embodiment, the product is a replaceable insole arranged to fit into a person's shoe, and wherein the platform comprises an upper layer and a lower layer with the set of electrical conductors arranged between the upper and lower layers, and wherein the stimulation electrodes extend through holes in the upper layer. As explained, such product can be manufactured at a low cost thus allowing one-time use and thereby easy mounting of a new clean product on the foot of each person. Especially, at least the upper layer may be made of a reusable material, such as a sheet of nonwoven material. Such embodiment will allow only a limited waste of material in case of a one-time use product.
In some embodiments, at least one stimulation electrode is spatially distributed on the platform so as to enable stimulation of each one of the person's foot sole areas: heel, fore foot, and mid foot. This allows a FET control system to activate the most efficient stimulation positions for obtaining the desired withdrawal reflex and thus e.g. reduce adaptation (habituation) effects. More specifically, it may be preferred that the product comprises a plurality of stimulation electrodes spatially distributed so as to enable stimulation of a plurality of different positions of each one of the person's foot sole areas: heel, fore foot, and mid foot. As already explained, this allows an automated FET system to activate the most appropriate positions according to a feedback loop, thus accounting for individual differences.
In some embodiments, the ground plane extends spatially so as to enable contact to at least one of the person's foot regions: heel of foot sole, fore foot of foot sole, mid foot of foot sole, back of heel, and upper part of foot. It may be preferred that the ground plane electrode extends spatially so as to enable contact to a plurality of said regions of the person's foot. In one specific embodiment, the product comprises a plurality of spatially separated ground plane electrodes, while in other embodiments, the ground plane electrode may extend in several ones of said regions by constituting one large conductive area.
It may be preferred that the platform is substantially foot shaped, such that it fits the shape of a normal foot and thus fits inside existing footwear, in case it is an insole product.
In some embodiments, the product comprises an additional platform element structurally linked to the platform, wherein the additional platform element comprises a stimulation electrode or a ground plane electrode in electric connection with said electric interface. Especially, the additional platform element is connected to the platform so as to enable the stimulation electrode or the ground plane electrode to be in contact with an upper part of or a back of the heel of the person's foot when mounted for normal use. Such additional platform element may be in the form of a flap that can be bent to make contact to the back of the heel or the upper part of the person's foot during normal use.
The product may comprise a sensor arranged to provide a feedback indicative of a person's gait phase upon the person walking when wearing the product, such as a sensor arranged between the platform and an upper layer of the product. Such sensor will allow the product to be used in FET based systems with feedback, where the sensor can be used to provide feedback to the FET algorithm regarding in which gait phase the leg is. This may eliminate the need for further feedback sensors, thus providing easy mounting of the equipment, since no individual fitting is needed, if the sensor is integrated in the product. In specific embodiment, the sensor is electrically connected to one or more electrical connectors within said electric interface, such as within the same plug or socket providing the external connection of the stimulation electrodes and the ground plane. This allows very easy connection to a feedback based FET system. Especially, it may be preferred that at least one sensor is spatially arranged in relation to the platform so as to enable sensing of the person's foot touching the ground, when wearing the product. The sensor may comprise an electric switch arranged to switch between an electrically closed and electrically open state upon a person's foot touching the ground, when wearing the product. Such electric switch may be implemented by one of: a force sensitive sensor, an electric switch with an on state and an off state, capacitive transducers, load cells, strain gauges, piezoelectrical force sensors. Simple sensors can be manufactured in low cost and still allow the product to be in the form of a one-time use insole product. The sensor may include one or more advanced sensor technologies, e.g. a laser-based distance sensor to sense distance to the ground, an accelerometer etc., however in such case the manufacturing costs will increase and thus such embodiments are not suited for one-time use.
To further allow a more detailed information about the gait phase, the sensor may comprise a plurality of spatially distributed sensor elements, such as a plurality of electric switches, in different regions of the platform so as to enable sensing of respective areas of the person's foot touching the ground, when wearing the product. Especially, the plurality of sensor elements are electrically connected to respective electrical connectors of the electric interface so as to allow external individual electrical access to the plurality of sensor elements via one single plug or socket of the electric interface.
The electric interface may be implemented by a connector in the form of a plug or socket having a shape different from standard connectors, so as to avoid non-intended connection to external equipment.
The set of electrical conductors may comprise a flexible PCB spatially extending within the platform so as to electrically connect each of the plurality of stimulation electrodes and the respective electrical connectors of the electric interface.
An end of the set of electrical conductors may extend away from the platform, so as to allow the plug or socket of the electric interface to be placed outside a person's shoe.
In a second aspect, the invention provides a system arranged for gait training, such as for rehabilitation of a person after a stroke, the system comprising
In one embodiment, the system comprises
a sensor arranged to sense a parameter representative of a movement of the person's leg and to generate a feedback signal accordingly, such as a sensor as described in embodiments of the first aspect, and
a processor unit operationally connected to the stimulation unit and to the sensor, the processor unit comprising a processor running a control algorithm so as to generate a control signal to the stimulation unit in response to the feedback signal.
In a third aspect, the invention provides use of a product according to the first aspect for Functional Electric Stimulation, such as reflex based gait training, such as for rehabilitation of a person after a stroke.
In a fourth aspect, the invention provides use of a product according to the first aspect for diagnostics of central sensitization in relation to chronic pain by assessing expanded reflex receptive fields via distributed electrical stimulation.
It is appreciated that the same advantages and equivalent embodiments apply for the second and third aspects as mentioned for the first aspect.
Embodiments of the invention will be described, by way of example only, with reference to the drawings, in which
a and 2b illustrate two views of an insole embodiment with a ground plane electrode and a heel stimulation electrode positioned on flaps on the insole platform,
a and 3b illustrate two views of another insole embodiment with one centrally positioned ground plane electrode,
It appears that the area covered by the ground plane electrode G is significantly larger than the area covered by each of the stimulation electrodes S1, S2, S3, and in the present embodiment the ground plane electrode G covers the majority of the platform area, in fact more than 90% of the platform area, and it is formed as one single area that extends in both forefoot, arch of foot, and heel areas. The large area compared to the stimulation electrode area is required to provide the desired painful sensation provoking a withdrawal effect, which is the basis for a reflex-based gait training FET system. Preferably a ratio between area of ground plane electrode and area of one stimulation electrode is more than 10, such as a ratio of 15-20. For cases where the ground plane electrode extends over a large area of the foot, the ratio may be up to such as 50 or even 100. Further, the area of one stimulation electrode is preferably more than 1 cm2, such as 1-2 cm2, or such as 2-5 cm2.
As seen in the layout sketch of
a and 2b illustrate an alternative insole embodiment. Here the platform SM is also foot shaped, but in the illustrated layout only one stimulation electrode is present in each of the foot sole regions, namely a fore foot electrode S_f, an arch of the foot electrode S_a, and a heel electrode S_h on the main part of the platform PF1. In addition, a flap PF3 is attached to the heel part of the main platform part PF1, e.g. integrally manufactured, e.g. monolithically integrated, with the platform SM material, and carries a stimulation electrode S_ph which fits to the posterior part of the person's heel when flapped into place for normal use as is seen in
Further,
a and 3b illustrate yet another insole embodiment, referring to details in the foregoing embodiments already described. Again a foot shaped platform forms the basis onto which groups of stimulation electrodes, namely one group S_f of three stimulation electrodes S_f1, S_f2, S_f3 in the forefoot region, one group S_a in the arch of foot region, one group in the heel region S_h, and one group S_ph on a heel flap arranged for contact with a posterior part of the person's heel. In addition, two pressure sensitive sensors are positioned in each part of the foot sole, namely one in the forefoot region PS1, and one in the heel region PS2. One large ground plane electrode G extends primarily in the arch of the foot region, and only partly in the forefoot and heel regions. As already mentioned, the groups of a plurality of stimulation electrodes each individually accessible via the electric interface allows for individual adjustment and refining of stimulation, e.g. based on an automated algorithm using feedback from the sensors PS1, PS2.
The stimulation voltage SV required, e.g. typically up to voltages within the range 50-400 V though typically around 200 V, in order to generate the required stimulation current to trigger the withdrawal reflex, is applied by the stimulator unit STM which is controlled in response to a control signal CS generated by a processor unit PU which runs a control algorithm CA. This control algorithm CA calculated the control signal CS in response to a feedback signal FB which the processor unit PU receives from a sensor SN which is arranged to sense a parameter, e.g. acceleration of the leg, here illustrated as a goniometer SN sensing the knee angle, and generates the feedback signal FB according to this parameter. The control algorithm CA is preferably designed to adjust the control signal CS so as to obtain a target trajectory for the leg. In the illustrated example, the control algorithm CA may be designed to determine a control signal CS resulting in a stimulation S that would most probably provide a target knee angle of the leg LG as a function of time during one walking step.
The sensor providing the feedback signal FB may in addition to or as an alternative to the shown goniometer SN be a sensor placed in the product SP, such as the illustrated pressure sensors on
It is to be understood that in all the illustrated embodiments, goniometers may be entirely replaced by sensor(s) in the form of accelerometer(s) and/or gyroscope(s). Especially, it may be preferred to build in such accelerometer(s) into a part of an insole.
To sum up, the invention provides a product, e.g. an insole for a shoe, fitting onto a person's foot sole based on a platform (SM) of a flexible and electrically isolating material. Multiple stimulation electrodes (S1, S2, S3) with adhesive stimulation areas of at least 1 cm2 are spatially distributed on the platform (SM). A conducting and adhesive ground plane electrode (G) with at least an area of 10 times a stimulation electrode area is arranged for contacting the person's foot. An electric interface (I) comprising a plug or socket with externally accessible electrical connectors to allow external individual electrical access to the plurality of stimulation electrode areas (S1, S2, S3) and to the ground plane electrode (G). The electric interface is capable of handling at least a voltage of 200 V, preferably 400 V. Such product is suited for reflex-based gait therapy, where the person's withdrawal reflex is triggered by a painful stimulation of the person's foot sole. Many distributed stimulation electrodes allow individual fitting for optimal stimulation, and low cost sensors built into the product may be used to provide feedback regarding the gait phase, i.e. the product is a one-time use insole suited for easy and hygienic gait therapy in a clinic.
Although the present invention has been described in connection with preferred embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the scope of the present invention is limited only by the accompanying claims.
In this section, certain specific details of the disclosed embodiments are set forth for purposes of explanation rather than limitation, so as to provide a clear and thorough understanding of the present invention. However, it should be understood readily by those skilled in this art, that the present invention may be practiced in other embodiments which do not conform exactly to the details set forth herein, without departing significantly from the spirit and scope of this disclosure. Further, in this context, and for the purposes of brevity and clarity, detailed descriptions of well-known device, circuits and methodology have been omitted so as to avoid unnecessary detail and possible confusion.
In the claims, the term “comprising” does not exclude the presence of other elements or steps. Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. Thus, references to “a”, “an”, “first”, “second” etc. do not preclude a plurality. Reference signs are included in the claims however the inclusion of the reference signs is only for clarity reasons and should not be construed as limiting the scope of the claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| PA 2011 70244 | May 2011 | DK | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DK2012/050171 | 5/15/2012 | WO | 00 | 11/8/2013 |
