Abstract:
A foot sensor device and method for gait enhancement, the device including: (a) a sensor unit having a casing, the sensor unit for disposing within a shoe of a user, the sensor unit for sensing a parameter associated with a gait event; (b) an electronic communication unit, electrically associated with the sensor unit, for receiving a signal pertaining to the parameter, the electronic unit having,: (i) a microcontroller; (ii) a transmitting unit for transmitting, in a wireless fashion, gait information based on the signal, to a unit of an orthosis external to the foot sensor device, and (iii) a housing for housing at least one of the microcontroller and the transmitting unit, and (c) a fastening unit, attached to the housing, adapted to fasten on to the shoe, so as to secure the communication unit in a fixed position during gait

Description:
This application draws priority from U.S. Provisional Patent Application Ser. Nos. 60/736,858, filed Nov. 16, 2005, 60/746,060, filed May 1, 2006, and 60/805,359, filed Jun. 21, 2006. 
    
    
     FIELD AND BACKGROUND OF THE INVENTION 
     The present invention relates to sensor devices for gait enhancement, and more particularly, to such a sensor device having an attachment mechanism for attaching the device to the rim of a shoe. 
     It is known that various pathologies of the neuromuscular system due to disease or trauma to the central nervous system, such as stroke, spinal cord injury, head injury, cerebral palsy and multiple sclerosis, can impede proper limb functioning of the legs. Gait, the biomechanical description of walking, can suffer static and dynamic parameter variations due to neuromuscular impairments that cause non-symmetrical walking and reduced walking speed and stability, and often require increased energy consumption. 
     Drop foot describes the gait attributable to weak or uncoordinated activation of the ankle dorsi-flexors due to disease or trauma to the central nervous system A patient suffering from drop foot tends to drag the foot during the swing phase of walking and usually try to compensate for this dragging by hiking the hip or swinging the affected leg in a circular motion. These patients tend to have impaired stability, are prone to frequent falls, and have walking movements that are unaesthetic and energy consuming 
     It is known, however, that functional electrical stimulation (FES) can Generally be used to activate the leg muscles of such patients Precisely timed bursts of short electrical pulses are applied to motor nerves to generate muscle contractions, which are synchronized with the gait of the patient, so as to improve the leg function and enhance the gait 
     Commercially available FES devices utilize a sensor, for disposing underneath the foot of the user, to trigger the electrical pulses being applied to the motor nerves. The sensor senses foot rise or foot strike and accordingly triggers the stimulation pulses administered to the motor nerves. The sensor device is physically distinct from the orthosis. 
     U.S. Pat. No. 6,507,757 to Swain, et al., discloses one typical foot sensor device of the prior art, in which a foot pressure switch, or sensor, is permanently disposed in the shoe of the affected leg. An electrical circuit is interrupted during the stance phase, when a significant weight is placed on the heel, and reconnects when the heel is lifted during the swing phase. Wires disposed under the clothing connect the sensor with an external stimulator unit that can be attached to the belt or kept in a pocket of the user. The stimulator unit is connected to the electrodes by additional electrical wires 
     In other FES orthotic devices, the cumbersome wires are obviated by using a radio frequency (RF) system in which the foot sensor device and other components of the FES orthotic device communicate in a wireless fashion. However, the use of such an RF system necessitates integrating an RF transmitting unit, or head, within the foot sensor device The transmitting unit can be bulky and sensitive to humidity and mechanical stress. Consequently, such transmitting units are typically mounted on and attached to the calf of the patient. 
     U.S. Design Pat. No. D494,273 to Haugland, et al., assigned to Neurodan A/S, describes a pressure sensor switch device for placing underneath the foot of the patient. The communication head is held at a predetermined distance from the sensor device by a wide, semi-rigid spine. The device disclosed by Haugland, et al., can be used as a component of the ActiGait® system manufactured by Neurodan A/S. In the ActiGait® system, the pressure sensor device is inserted into a small pouch within a sock, such that upon donning of the sock, the pressure switch is disposed underneath the foot A substantially non-elastic band is tightened around the calf to secure the RF unit in place against the calf of the impaired leg. 
     This approach is disadvantageous in that the patient, who is often hemiplegic or may suffer from other disorders, is required to add the donning of an additional item—the sock—to his routine This unintuitive action is particularly problematic for patients who need or prefer to don the FES orthotic device in an unassisted fashion. 
     A further disadvantage of this design is that the semi-rigid spine may rub against the foot and heel Also, the electronic head that houses the RF transceiving unit may rub the ankle or lower calf of the user during the course of gait. Moreover, because the pressure switch and RF transceiving unit are mechanically connected by a wide, at least semi-rigid neck, pressures exerted on the electronic head (e.g., when the head gets caught on, or bumped by, an object during the course of gait), are mechanically translated into forces on the foot sensor. These forces may impede the efficacy and sensitivity of the foot sensor. A further disadvantage lies in the limited ability to adjust the electronic head of the pressure switch to different shoe heights: the electronic head protrudes excessively from low-rimmed shoes, and cannot be fitted to shoes or boots in which the rim is at or above the height of the electronic head. 
     There is therefore a recognized need for, and it would be highly advantageous to have, a sensor device for neuroprosthetic gait enhancement that overcomes the various deficiencies of the prior art devices. It would be of particular advantage to have such a sensor device that is essentially effortless to don, avoids the discomfort associated with prior art sensor devices, and is secured so as to operate in a safe and robust fashion, 
     SUMMARY OF THE INVENTION 
     According to the teachings of the present invention there is provided a foot sensor device for gait enhancement, including: (a) a sensor unit having an external casing, the sensor unit for disposing within a shoe of a user, the sensor unit for sensing, a parameter associated with a gait event; (b) an electronic communication unit, electrically associated with the sensor unit, for receiving a signal pertaining to the parameter, the electronic unit having: (i) a microcontroller; (ii) a transmitting unit for transmitting, in a wireless fashion, gait information based on the signal, to a unit of an orthosis external to the foot sensor device, and (iii) a housing for housing at least one of the microcontroller and the transmitting unit, and (c) a fastening unit, attached to the housing, the fastening unit adapted to fasten on to the shoe, so as to secure the electronic communication unit in a substantially fixed position during gait of the user. 
     According to further features in the described preferred embodiments, the fastening unit includes a clamp unit. 
     According to still further features in the described preferred embodiments, the fastening unit is adapted to fasten on to a rim of the shoe. 
     According to still further features in the described preferred embodiments, the clamp unit has at least two arms designed and configured to fasten around a rim of the shoe. 
     According to still further features in the described preferred embodiments, the clamp unit is at least semi-rigidly associated with the housing. 
     According to still further features in the described preferred embodiments, the clamp unit is rigidly associated with the housing. 
     According to still further features in the described preferred embodiments, the housing of the electronic unit and the external casing of the sensor unit are substantially mechanically independent. 
     According to still further features in the described preferred embodiments, the clamp unit further includes a locking lever adapted for locking the arms in position around the rim of the shoe. 
     According to still further features in the described preferred embodiments, a facing of the housing is concave, so as to fit a natural curvature of a leg of the user. 
     According to still further features in the described preferred embodiments, the housing and the clamp unit each have a face for disposing towards a leg of the user when the user wears the shoe, the device being designed and configured such that the housing and the clamp unit are attached to form an angle within a range of about 150° to about 175° between the faces. 
     According to still further features in the described preferred embodiments, the angle is in a range of about 155° to about 175°. 
     According to still further features in the described preferred embodiments, the angle is in a range of about 160° to about 175°. 
     According to still further features in the described preferred embodiments, the angle is in a range of about 160° to about 170°. 
     According to still further features in the described preferred embodiments, the transmitting unit is a transceiving unit. 
     According to still further features in the described preferred embodiments, the device further includes: (d) the shoe. 
     According to still further features in the described preferred embodiments, the sensor unit is disposed under an inner sole of the shoe. 
     According to still further features in the described preferred embodiments, the fastening unit includes a clamp unit adapted to enable a hemiplegic patient to affix the clamp unit to the shoe, using a single hand. 
     According to still further features in the described preferred embodiments, the housing is a casing. 
     According to another aspect of the present invention there is provided a method of enhancing gait including the steps of: (a) providing a device including: (i) a sensor unit having an external casing, the sensor unit for disposing within a shoe of a user, the sensor unit for sensing a parameter associated with a gait event; (ii) an electronic communication unit, electrically associated with the sensor unit, for receiving a signal pertaining to the parameter, the electronic unit having: (A) a microcontroller; (B) a transmitting unit for transmitting, in a wireless fashion, gait information based on the signal, to a unit of an orthosis external to the foot sensor device, and (C) a housing for housing at least one of the microcontroller and the transmitting unit, and (iii) a fastening unit, attached to the housing, the fastening, unit adapted to fasten on the shoe, so as to secure the electronic communication unit in a substantially fixed position during gait of the user, and (b) donning the device by affixing the fastening unit to the shoe. 
     According to further features in the described preferred embodiments, the affixing of the fastening unit includes affixing of a clamp unit. 
     According to still further features in the described preferred embodiments, the fastening unit is affixed to a rim of the shoe. 
     According to still further features in the described preferred embodiments, the method further includes, prior to step (b), the step of (c) disposing the sensor unit under an inner sole of the shoe. 
     According to still further features in the described preferred embodiments, the affixing of the fastening unit is effected using a single hand, even by a hemiplegic patient using a single hand. 
     According to still further features in the described preferred embodiments, the method further includes the step of: (c) locking the arms in position against the rim of the shoe. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of the preferred embodiments of the present invention only, and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice. Throughout the drawings, like-referenced characters are used to designate like elements. 
       In the drawings: 
         FIG. 1  is a perspective view of the inventive foot sensor device; 
         FIG. 2  is a schematic, three-dimensional view of the inventive foot sensor device, the sensor unit being disposed underneath the shoe insole, and the communication unit being mounted on the shoe rim; 
         FIG. 2   a  is a partial cross-sectional view of a shoe floor, a sensor casing, and a hook and loop system for affixing the casing to the floor; 
         FIG. 3  is a schematic electronic diagram of the inventive foot sensor device; 
         FIG. 4  is a perspective side view of the communication unit and the clamp associated therewith, the clamp disposed in an open position; 
         FIG. 5  is another perspective side view of the communication unit and the clamp associated therewith, the clamp disposed in a closed position; 
         FIG. 6   a  is a schematic, three-dimensional view of the inventive foot sensor device mounted on the shoe rim, with the communication head hugging the inner calf of the user, and 
         FIG. 6   b  is a schematic, three-dimensional top view of  FIG. 6   a.    
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     One embodiment of the present invention is a sensor device for neuroprosthetic gait enhancement, the device designed for facile yet secure attachment to the rim of the user&#39;s shoe, even by a hemiplegic user. 
     Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of the components set forth in the following description or illustrated in the drawings The invention is capable of other embodiments or of being practiced or carried out in various ways Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. 
     Referring now to the drawings,  FIG. 1  a perspective view of the inventive foot sensor device  100  for a gait-enhancing orthosis. Foot sensor device  100  includes a sensor unit  5  having a sensor casing  10 , in which is disposed a sensor element  16 , a communication unit  30  enclosed by housing  25 , and wiring (wire or cable)  20  for mechanically and electrically connecting sensor element  16  and communication unit  30 . Foot sensor device  100  further includes a fastening unit such as clamp unit  40 , rigidly or at least semi-rigidly attached to communication unit  30 , for attaching communication unit  30  to the user&#39;s shoe, and more typically, to the rim of the user&#39;s shoe (see  FIG. 2  hereinbelow). It should be stressed that sensor element  16  of inventive foot sensor device  100 , in contrast to RF-based foot sensor devices of the prior art, is substantially mechanically independent of communication unit  30 . The advantages of this attribute are elaborated hereinbelow. 
     As used herein in the specification and in the claims section that follows, the term “substantially mechanically independent” refers to two components, electrically and mechanically connected, and physically set apart from one another, the components having substantially no constraint when moved towards one another. A typical example of such substantially mechanically independent components is communication unit  30  and sensor casing  10 , connected by a flexible conductive wire. 
     Generally in the prior art, the foot pressure switch, or the sensor, is either permanently disposed in the shoe, or disposed in a small pouch of a sock, as in the above-described ActiGait® systems As shown in  FIG. 2 , by sharp contrast, sensor unit  5  is preferably placed under an inner sole  45  of a shoe  50 , beneath the heel area. Sensor casing  10  can be removed or repositioned with facility, by lifting up or removing inner sole  45 . 
     As shown in a cross-sectional view in  FIG. 2   a,  sensor unit  5  may advantageously secured to the floor  55  of the shoe by a hook and loop system  56  such as Velcro®. By way of example, hooks  56   a  of hook and loop system  56  may be attached to sensor casing  10 , and loops  56   b  may be attached to floor  55 . In particular cases, sensor casing  10  may also be positioned under the forefoot area of the shoe. 
     Casino  10  is configured to protect the inner sensor element against mechanical stress and wetness, and is made of two flexible layers, selected such that the upper layer is more flexible than the lower layer. An additional piece of sponge-like material lies between the internal layer and the sensor, providing additional protection to the sensor. The two layers of sensor casing  10  are attached by various means such as ultrasonic welding, RF welding, gluing, heat welding, or pins. Casing  10  is connected to communication unit  30  by means of wiring  20 , which is long enough to enable attachment of communication unit  30  to a rim  48  of shoe  50 , irrespective of the height of the shoe rim. It should be noted that when the shoe is not worn, foot sensor device  100  can be left attached to shoe  50 , such that the user is not challenged with an additional, cumbersome, and unintuitive doffing action, and in subsequent use, a similarly challenging donning action. 
     The positioning of communication unit  30  above the rim of shoe  50  protects communication unit  30  from being banged and rubbed by external objects, and from exposure to dirt and moisture Such positioning may also serve to keep communication unit  30  hidden under the trousers, which is aesthetically desirable and, perhaps more importantly, protects communication unit  30  from being caught or bumped during gait. 
     Moreover, in foot sensor device  100  of the present invention, the height of communication unit  30  on the leg of the user is substantially fixed with the height of the shoe rim. In the above-referenced design patent to Haugland, et al., by sharp contrast, the distance between the communication unit and the sensor unit is determined by the semi-rigid spine connecting therebetween, such that the height of the communication unit is not adjustable. Consequently, the entire communication unit may not extend over the shoe rim in boots and other high-rimmed shoes, and the communication unit may be disposed at a disadvantageously distance from the shoe rim in low shoes. 
     Another advantage of the foot sensor device  100  of the present invention is that wiring  20  is thin and is easily contained within the shoe. The wide spine of the device disclosed by Haugland, et al., is bulky, such that the user is subject to the distraction of sensing the spine within the shoe, even to the point of experiencing discomfort. 
     Perhaps most significantly, foot sensor device  100  may be advantageously fixed to the rim of the shoe in a semi-permanent fashion, i e, even during those periods in which the user is not undergoing neuroprosthetic gait enhancement Thus, prior to activating or reactivating the device, no additional donning procedure is required. 
       FIG. 3  is a schematic electronic diagram of inventive foot sensor device  100 . Sensor element  16  is connected to, and preferably powered by, electronics or communication unit  30  by means of wiring  20  Communication unit  30  includes a microcontroller  80 , a radio frequency (RF) transceiver  82 , and an antenna unit  83  having a matching network for converting the signal from the wired medium to a wireless medium, and from the wireless medium to the wired medium. 
     The resistance of sensor element  16  changes with the force applied thereon. In order to measure the actual resistance of sensor element  16 , foot sensor device  100  is equipped with a voltage divider consisting of sensor element  16  and a bias resistor  81  preferably disposed in unit  30 . When a voltage is applied to the voltage divider, the voltage is divided according to the resistance ratio between sensor element  16  and bias resistor  81 . This voltage is measured in order to assess the resistance of sensor element  16 . 
     Communication unit  30  is also equipped with a small coin battery  84  that provides power to microcontroller  80 , RF transceiver  82 , and sensor element  16 . 
     Microcontroller  80  controls and monitor the operation of foot sensor device  100  and executes the algorithms thereof Preferably, microcontroller  80  communicates with RF transceiver  82  via a Serial Peripheral Interface (SPI). 
     Referring now to  FIGS. 4 and 5 , clamp unit  40  is designed for facile and fully reversible attachment and disattachment of communication unit  30  to the rim of a shoe, such that even a hemiplegic patient can perform these functions using a single hand. 
     Clamp unit  40  includes an external (i.e., distal to the shoe) arm or jaw  55 , an internal arm or jaw  60  and a locking lever  65  having a fulcrum  70  for closing and locking together jaws  55  and  60 . Preferably, when clamp unit  40  is in an open position, jaws  55  and  60  are positioned in a pre-defined angle. The magnitude of this angle is important, since it determines the opening range of the clamp, to fit shoe rims of varying width. 
     Preferably, arm  55  includes a spring adapted such that clamp unit  40  is in a normally open condition. 
     Preferably, clamp unit  40  is further adapted such that when clamp unit  40  is in the closed position, with no article clamped between jaws  55  and  60 , a small gap (typically less than or equal to one millimeter) exists between jaws  55  and  60 . This eliminates the need to apply a strong force in opening clamp unit  40 . 
     Teeth  75 , disposed on at least one of jaws  55  and  60 , ensure a firm grip of clamp unit  40  on the shoe rim, such that clamp unit  40  is inherently adaptable to a wide range of rim thicknesses, contours, and textures. Locking lever  65  serves to fix jaws  55  and  60  to the rim of the shoe. 
     Internal jaw  60  has a thin profile, such that when disposed inside shoe  50  of the user, internal jaw  60  does not to protrude into the skin of the foot and cause discomfort to the user. 
     Typically, clamp unit  40  is permanently and rigidly associated with communication unit  30 . The connection of clamp unit  40  to communication unit  30  is achieved by an element (not shown) that, from clamp unit  40 , extends into communication unit  30  and is secured therein. 
     It must be emphasized that other embodiments of clamps and fastening units will be apparent to those skilled in the art. For example, the clamp could have fixed arms that grip the shoe rim by a constant spring force, without an opening and closing mechanism. 
     As used herein in the specification and in the claims section that follows, the tern “casing”, with respect to the electronic communication unit, refers to the at least semi-rigid casing enveloping at least a portion of the electronic communication unit. 
     As used herein in the specification and in the claims section that follows, the term “housing” and the like, with respect to the electronic communication unit, is meant to include any rigid or semi-rigid projections of the housing, and is meant to include any elements that are at least semi-rigidly attached to the casing. The tern “housing” is specifically meant to include rigid and semi-rigid spines attached to the electronic communication unit, such as the element disclosed in U.S. Design Pat. No. D494,273 to Haugland, et al. 
     As used herein in the specification and in the claims section that follows, the term “shoe” is meant to include boots, slippers, sandals having an at least semi-rigid position for fastening the fastening unit. Typically, this at least semi-rigid position is the rim of the shoe. Preferably, the shoe has rigid or at least semi-rigid sole and a covering for firmly containing a foot therein 
       FIG. 6   a  is a schematic, three-dimensional view of the inventive foot sensor device  100  mounted on shoe  50 .  FIG. 6   b  is a schematic, three-dimensional top view of  FIG. 6   a  These figures collectively show an inner face  58  of housing  25  (of communication unit  30 ) hugging an inner calf  62  of the user. The surface of the casing has a small, predetermined curvature that is designed to match and hug the natural curvature of the leg, thereby improving comfort and preventing chafing of communication unit  30  against the skin. 
     Flexibility, or a degree of freedom, with respect to the leg, is imparted to communication unit  30  by the flexibility of the shoe rim. 
     Alternatively, communication unit  30  may be corrected to clamp  40  by means of an elastomeric hinge to allow extra flexibility of the casing of communication unit  30  against the foot. The electronic casing may also include a hinge that allows calibrating the angle of the electronic casing against the foot for personal adjustment with respect to specific users and specific shoe dimensions. 
     Referring back to  FIG. 5 , the inner facing  58  of housing  25  and clamp unit  40  (internal arm  60 ) form an angle of about 165°. After extensive tests were performed on users having widely varying physical characteristics, the inventors discovered that within a narrow range of angles, chafing and pressure of housing  25  against the leg of the user is substantially insignificant. In addition, within this narrow range of angles, housing  25  does not protrude away from the leg in an unreasonable fashion, such that housing  25  is protected from bumping into, or being caught by objects during gait. We have found this narrow range of angles to be between 150° and 175°. More preferably the range of angles is between 155° to 160° and 175°, and most preferably, the range is between 160° and 170°. 
     Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.