Abstract:
A gait rehabilitation apparatus ( 12 ) uses a mechanical shadow leg ( 42 ) positioned behind the biological leg ( 18 ) to provide forces and guide the biological leg in use.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is the U.S. national phase of International Application No. PCT/EP2013/053354 filed Feb. 20, 2013, which claims priority of British Application No. 1222322.8 filed Dec. 12, 2012, the entirety of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention is concerned with an apparatus for driving and/or supporting a limb and an associated method. More specifically, the present invention is concerned with a mechanical apparatus for gait rehabilitation by guiding and/or applying forces to a limb of a human or animal subject. 
       BACKGROUND OF THE INVENTION 
       [0003]    Medical conditions such as brain damage (stroke) and nerve damage (spinal cord injury) caused by accident or injury can result in the temporary loss or impairment of use of a subject&#39;s limbs. For example, the legs may be limited in their use such that the subject finds it difficult to walk. Following such injury or illness, a period of rehabilitation is typical during which nerve and/or muscle damage is repaired. 
         [0004]    Such rehabilitation has been traditionally provided by a physiotherapist or physical therapist manually interacting with the subject. For example, the subject may walk on a treadmill or along a set path during which activity the physiotherapist will manually support and manipulate the subject&#39;s legs in order to provide the desired motion and feedback. By this process muscles and nerves can be gradually repaired. 
         [0005]    Methods which involve the direct interaction of a physiotherapist, or require the physiotherapist to support and/or guide the subject are not ideal because they may result in uneven or unpredictable forces on the subject. It may also be uncomfortable for the therapist to undergo such activity for extended periods, potentially with numerous subjects. Fatigue or strength of the physiotherapist often is the limiting factor in therapy 
         [0006]    An alternative to the above mentioned method is to provide a mechanical gait rehabilitation robot. Mechanical gait rehabilitation robots are known in the art. 
         [0007]    WO2012/062283 discloses a device which uses a number of flexible cords in tension to support a subject&#39;s limbs during rehabilitation. Another example of such a device can be seen in U.S. Pat. No. 7,998,040. Although such devices can apply uni-directional forces to the subject (with the cords in tension), they are not able to provide forces in the opposite direction (a flexible cord cannot carry a compressive force), or in other directions (e.g. sideways to retain the subject&#39;s leg in a set path). 
         [0008]    U.S. Pat. No. 6,666,798 discloses an apparatus for rehabilitation in which a therapist is connected to a subject via a set of rigid links. This system is provided to free the physiotherapist&#39;s hands, and still requires the physiotherapist to bear the weight of, and guide, the subject&#39;s legs. Therefore the inherent lack of repeatability and potential for injury to the physiotherapist is still present. The disclosure is also only concerned with lower leg rehabilitation, having the ankle and knee connected to the therapist. Therefore rehabilitation of the upper leg is not considered. 
         [0009]    Prior art document CN101862255B discloses a known type of rehabilitation apparatus which has a mechanical leg at the side of the patient&#39;s leg. A problem with this type of apparatus is that it needs to be provided with extendible leg members in order to account for various different sizes of patient. As such, this apparatus is particularly complicated and time consuming to set up for each individual patient. 
       SUMMARY OF THE INVENTION 
       [0010]    It is an aim of the present invention to overcome or at least alleviate the above mentioned problems with the prior art. 
         [0011]    According to a first aspect of the invention there is provided a gait rehabilitation apparatus comprising an articulated mechanical shadow leg configured to mimic the movement of a biological leg, a first member extending from the shadow leg and having a first biological leg attachment formation defined thereon, wherein the first member extends in a substantially anteroposterior direction relative to the shadow leg in use. 
         [0012]    Advantageously, the provision of an articulated, mechanical shadow leg positioned behind the leg of the subject allows for controlled, repeatable and reliable movement to be introduced. The joints of the shadow leg can be arranged so that only desired motion of the subject is permitted. Furthermore, because the shadow leg is positioned behind the subject&#39;s leg, various different sizes of subject can be accommodated. Evidently, the position of the first member will change depending on the size of the patient, however, this would not be significant enough to serious affect the kinematics of the mechanism. 
         [0013]    Preferably, there is provided a second member extending from the shadow leg and having a second biological leg attachment formation defined thereon; wherein the second member extends in a substantially anteroposterior direction relative to the shadow leg in use. 
         [0014]    Preferably, the articulated shadow leg comprises an upper leg portion articulated about a shadow hip joint at an upper end in use. 
         [0015]    Preferably, the first member extends from proximate the shadow hip joint, and the second member extends proximate a knee region of the shadow leg. 
         [0016]    Preferably, the articulated shadow leg comprises a lower leg portion articulated about a shadow knee joint at an upper end in use. 
         [0017]    Preferably, the first member extends from proximate the shadow knee joint, and the second member extends proximate an ankle region of the shadow leg. 
         [0018]    Preferably, the articulated shadow leg comprises a foot portion articulated about a shadow ankle joint at an upper end in use. 
         [0019]    Preferably, the first member extends from proximate the shadow ankle joint, and the second member extends proximate a foot region of the shadow leg. 
         [0020]    Preferably, there is provided a third member extending from the shadow leg and having a third biological leg attachment formation defined thereon; wherein the third member extends in a substantially anteroposterior direction relative to the shadow leg in use. 
         [0021]    Preferably, the articulated shadow leg comprises an upper leg portion articulated about a shadow hip joint at an upper end in use; and, a lower leg portion connected to the upper leg portion and articulated about a shadow knee joint at an upper end in use. 
         [0022]    Preferably, the first member extends from proximate the shadow hip joint, the second member extends proximate the shadow knee joint and the third member extends proximate an ankle region of the shadow leg. 
         [0023]    Preferably, a fourth member is provided extending from the shadow leg and having a fourth biological leg attachment formation defined thereon; wherein the fourth member extends in a substantially anteroposterior direction relative to the shadow leg in use. 
         [0024]    Preferably, the articulated shadow leg comprises a foot portion connected to the lower leg portion and articulated about a shadow ankle joint at an upper end in use. 
         [0025]    Preferably, the fourth member extends proximate a foot region of the shadow leg. 
         [0026]    According to a second aspect of the present invention, there is provided a method of gait rehabilitation comprising the steps of providing an articulated mechanical shadow leg configured to mimic the movement of a biological leg, providing a first member connected to the shadow leg, providing a second member connected to the shadow leg, attaching the first and second members to the biological leg of a subject such that the first and second members extend in a substantially anteroposterior direction and, using the shadow leg to guide and/or provide force input to the biological leg. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING VIEWS 
         [0027]    An example gait rehabilitation apparatus and method in accordance with the present invention will now be described with reference to the accompanying figures in which:— 
           [0028]      FIG. 1  is a side schematic view of an embodiment of a gait rehabilitation apparatus in accordance with the present invention; and 
           [0029]      FIG. 2  is a further schematic side view of the apparatus of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0030]    With reference to  FIG. 1 , a subject  10  is attached to an apparatus  12  in accordance with the present invention. The subject  10  is supported by, and walking on a treadmill  14 . Such treadmills are well known in the art. The subject  10  has a torso  16 , a right leg  18  and a left leg  20 . 
         [0031]    The apparatus  12  of the present invention comprises a torso harness  22 , which wraps around the subject&#39;s torso  16 . The harness  22 , and therefore at least some of the weight of the subject  10  is supported from a mounting point  24  directly above the subject  10 . In the event that the subject cannot support their own weight, the harness  22  provides some assistance. 
         [0032]    A waistband  26  is positioned around the mid-section of the subject&#39;s torso  16 . The waistband is an adjustable belt of material which can be securely fastened to the patient. A leg strap  28  is wrapped around the subject&#39;s leg just below the knee. The leg strap also comprises an adjustable strip of material. Finally, a foot harness  30  is positioned around the subject&#39;s foot. The foot harness  30  is a cradle in which the foot rests, and comprises a stiff inflexible member extending from the ankle to the base of the foot. The foot harness  30  is attached to the foot such that it moves therewith rotationally and translationally. 
         [0033]    A substantially inflexible lower leg member  32  is attached to, and positioned between, the leg strap  28  and the ankle region of the side member of the foot harness  30 . The member  32  is adjustable in length as will be discussed below. The lower leg member  32  reacts excessive side-to-side forces cause by misalignment of the knee and ankle which would put the knee under significant stress. It also reacts any tangential forces on the knee which may move the leg strap  28 . 
         [0034]    An attachment point  34  is provided at the lower part of the subject&#39;s back on the waistband  26 . A second attachment point  36  is provided at an upper end of the member  32  and is coincident with the flexion/extension axis of the subject&#39;s knee. A third attachment point  38  is provided proximate a lower end of the member  32 , at the top of the foot harness  30  and is oriented to be substantially coincident with the flexion/extension axis of the subject&#39;s ankle. The member  32  is adjusted during fitting to ensure that the attachment points  36  and  38  align with the knee and ankle respectively. Finally, a fourth attachment point  40  is provided at the base of the subject&#39;s foot proximate the heel. 
         [0035]    The apparatus  12  comprises a shadow leg  42  comprising an upper leg member  44 , a lower leg member  46  and a foot member  48 . 
         [0036]    The upper leg member  44  is a stiff, elongate member of approximately the same length of an average human thigh. The upper leg member  44  is connected at its top end to a support (not shown) by a shadow hip joint  50  which allows articulation about an axis perpendicular to the page (and therefore equivalent to the extension/flexion movement of the subject&#39;s hip when walking). 
         [0037]    At the opposite, lower end of the upper leg member  44 , there is provided a shadow knee joint  52  which connects the upper leg member  44  and the lower leg member  46 . The shadow knee joint  52  is a rotational joint which also has an axis of rotation perpendicular to the page (and therefore equivalent to the extension/flexion movement of the subject&#39;s knee when walking). 
         [0038]    At the lower end of the lower leg member  46 , there is provided a shadow ankle joint  54  which again has an axis of rotation perpendicular to the page, per the subject&#39;s ankle in flexion/extension. The shadow ankle joint  54  connects the lower leg member  46  to the foot member  48 . 
         [0039]    Members  44 ,  46  and  48  each define together a shadow leg  42  which can be articulated by a suitable actuation system which is shown schematically at  56 . The actuation system  56  is capable of applying forces and/or motion constraints to the members  44 ,  46  and  48 . The actuation system  56  may take the form of an automated control system employing various electric motors or hydraulic or pneumatic cylinders. It is within the skill of the notional skilled person to provide a suitable actuation system for movement of the shadow leg  42 . 
         [0040]    Because the dimensions of the subject&#39;s legs are known, a geometric transformation can be provided as part of the automated control system which can relate movement of the shadow leg to movement of the subject&#39;s leg. In other words, for a required movement of the subject&#39;s leg, the system can calculate through which angles to actuate the shadow leg to produce the desired result. 
         [0041]    The shadow leg  42  and the right leg  18  of the subject  10  are connected by a plurality of members extending in an anteroposterior direction. A first member  58  extends from the shadow hip joint  50  to the attachment point  34  at the lower back of the subject  10 . A second member  60  extends from the shadow knee joint  52  to the attachment point  36  at the knee of the subject  10 . A third member  62  extends from the shadow ankle joint  54  to the attachment point  38  at the ankle of the subject  10 . A fourth member  64  extends from the bottom of the shadow foot  48  to the fourth attachment point  40  at the base of the foot of the subject  10 . Each member  58 ,  60 ,  62 ,  64  is rotatably mounted to the shadow leg  42  for rotation about axes parallel to the joints therein. 
         [0042]    Each of the members  58 ,  60 ,  62  and  64  are elongate, stiff members constructed from e.g., metal or a composite. Each member is the generally the same length, and as such the motion of the shadow leg  42  and biological leg  18  are constrained together. The member  60  is provided with some minor adjustability to ensure that when the shadow leg is fully extended, so is the subject&#39;s knee. This provides a mechanical stop on knee over-extension (which can be very harmful if permitted). 
         [0043]    The members are of a length longer than the members of the shadow leg  44 ,  46 ,  48  and are about 1 m long. 
         [0044]    The motion of the shadow leg  42  and biological leg  18  is demonstrated with respect to  FIG. 2 , in which the shadow leg  42  and the biological leg  18  have both advanced to a further position shown in hidden line. 
         [0045]    It will be noted that advantageously, the size of the subject  10  is not important. Should a larger or smaller subject be installed within the apparatus then the members  58 ,  60 ,  62  and  64  may spread apart slightly depending on the relative size of the subject&#39;s leg, however, because the members  58 ,  60 ,  62  are relatively long, the kinematics of the device will remain substantially the same. The fact that each of the members  58 ,  60 ,  62  and  64  are of a length that is longer than either the upper or lower leg members  44 ,  46  means that this change in size of the subject  10  has little effect on the relative movement of the patient&#39;s leg as compared to the shadow leg. 
         [0046]    Variations fall within the scope of the present invention. For example, instead of the subject  10  being placed on the treadmill  14 , the apparatus  12  may be mobile, i.e., mounted on a trolley or other mobile device such that the patient can walk around freely whilst being rehabilitated. 
         [0047]    The shadow leg  42  has mechanical restraints imparted thereon in order to avoid any excessive articulation of the subject&#39;s joints. For example, the knee joint  52  is limited by mechanical end stop to 180 degrees or thereabouts such that the patient  10  cannot hyperextend their knee. 
         [0048]    The functionality of the torso harness may be integrated into the waistband, to support the subject at the waist instead of the torso.