Abstract:
A prosthetic foot includes a rod having a substantially spherical head and a shank extending from the head. A connector is pivotally coupled to the spherical head of the rod. The connector has a coupling configured to attach to the stump of an amputee. A wear plate is disposed on the shank of the rod adjacent the connector. The wear plate is sized and shaped to contact the connector as the connector pivots on the spherical head of the rod. A spring is removably disposed on the shank of the rod and spaced apart from the wear plate a predetermined distance. The spring is compressible by the rod when the rod is disposed in a prosthetic foot and an axial load is applied to the rod.

Description:
PRIORITY CLAIM 
       [0001]    Priority is claimed to U.S. Provisional Patent Application Ser. No. 60/994,468, filed Sep. 18, 2007, and U.S. Provisional Patent Application Ser. No. 60/994,585, filed Sep. 19, 2007, which are herein incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to a prosthetic foot with multi-axial rotation. 
         [0004]    2. Related Art 
         [0005]    Many individuals have lost a limb for various reasons including war, accident, or disease. In most instances these individuals are not only able to live relatively normal lives, but physically active lives as well. Oftentimes, these individuals are aided in their everyday lives by a prosthetic limb. The objective of prosthesis is to provide an artificial limb that simulates the function and natural feel of the replaced limb. 
         [0006]    With respect to prosthetic feet, the development of a functional and natural artificial foot has been limited by material and imagination. Many designs have attempted to copy the anatomy of the foot or simulate its actions by replacing the bones and muscle with various mechanical simulation by replacing the entire foot with an energy storage element such as a spring. As the user steps onto the foot, the user&#39;s weight compresses the spring. As the user moves forward, the user&#39;s weight comes off the foot and the energy stored in the spring is used to propel the user forward. 
         [0007]    Almost all of the past designs have focused on the major aspect of the prosthetic foot movement of the ankle or foot as it relates to walking or running. Few designs consider the lateral, or side to side rotation of the foot when the foot is used on varied or uneven terrain. It will be appreciated that the forefoot and heel of a natural foot rotates with a medial to lateral roll-over to accommodate variations in terrain. Most artificial feet of previous designs usually incorporate a unitary foot that is incapable of such movement. 
         [0008]    Some designs have attempted to mimic the lateral rotation of the forefoot of a natural foot by splitting the forefoot region of the artificial foot longitudinally from the toe toward the heel, thereby effectively creating one or more “toes” on the prosthetic foot. This design is problematic, however, because the split creates at least two forefoot regions that can bend independent from one another and can result in an unnatural, out of balance feel to the user. 
       SUMMARY OF THE INVENTION 
       [0009]    It has been recognized that it would be advantageous to develop a prosthetic foot with a multi-axial rotatable ankle for providing smooth and steady multi-axial rotation laterally and longitudinally of the foot to allow the wearer to maneuver uneven terrain. Additionally, it has been recognized that it would be advantageous to develop a prosthetic foot with a multi-axial rotatable ankle for providing smooth and steady multi-axial rotation to assist with a natural medial to lateral roll-over of the prosthetic foot in response to uneven terrain. 
         [0010]    In one aspect, the present invention provides for an ankle for a prosthetic foot including a rod having a substantially spherical head and a shank extending from the head. A connector can be pivotally coupled to the spherical head of the rod. The connector can have a coupling configured to attach to the stump of an amputee. A wear plate can be disposed on the shank of the rod adjacent the connector. The wear plate can be sized and shaped to contact the connector as the connector pivots on the spherical head of the rod. A spring can be removably disposed on the shank of the rod and spaced apart from the wear plate a predetermined distance. The spring can be compressed by the rod when the rod is disposed in a prosthetic foot and an axial load is applied to the rod. 
         [0011]    In another aspect, a foot member can be clamped between the spring and the wear plate by a fastener coupled to the shank of the rod. 
         [0012]    Additional features and advantages of the invention will be apparent from the detailed description which follows, taken in conjunction with the accompanying drawings, which together illustrate, by way of example, features of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]      FIG. 1  is a cross section side view of a prosthetic foot with a multi-axial ankle in accordance with an embodiment of the present invention; 
           [0014]      FIG. 2  is a cross section front view of the prosthetic foot of  FIG. 1  taken along line  94 ; and 
           [0015]      FIG. 3  is a cross section top view of the prosthetic foot of  FIG. 1  taken along line  96 ; and 
           [0016]      FIG. 4  is a top view of a prosthetic foot with a multi-axial ankle in accordance with an embodiment of the present invention; and 
           [0017]      FIG. 5  is a cross section side view of a multi-axial ankle in accordance with an embodiment of the present invention; and 
           [0018]      FIG. 6  is an exploded view of the multi-axial ankle of  FIG. 5 . 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Reference will now be made to the exemplary embodiments illustrated in the drawings, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended. Alterations and further modifications of the inventive features illustrated herein, and additional applications of the principles of the inventions as illustrated herein, which would occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the invention. 
         [0020]    The present invention relates generally to an ankle for a prosthetic foot with variable toe-to-heel and medial-to-lateral rotation to provide for multi-axial rotation. The ankle can have a bolt or a rod with a spherical head and a shank that can be disposed through an elongated foot member in a prosthetic foot. A connector can be pivotally disposed on the spherical head of the rod. The connector can have a domed upper surface and an inverted pyramid coupling. The coupling can be attached to the stump of an amputee. The connector can pivot on the spherical head of the rod in a medial-to-lateral direction and in a toe-to heel direction. A wear plate can be disposed adjacent the connector and between the connector and the foot member of the prosthetic foot. The connector can contact the wear plate when the connector pivots about the spherical head. The wear plate can be sized and shaped to reduce contact of the connector with the foot member of the prosthetic foot so as to protect the foot member from wear and tear due to abrasion from the moving connector. A spring can be disposed on the shank of the rod on an opposite side of the foot member from the wear plate. A fastener, such as a nut, lock nut, pin, clip, or other type of fastener, can be disposed on the shank adjacent the spring. The fastener can apply a load on the spring member and clamp the foot member of the prosthetic foot between the spring and the wear plate. In this way, the spring member can apply an axial pre-load on the rod such that when a user walks on the prosthetic foot, opposing axial loads can be transferred to the rod and can compress the spring. Advantageously, when the spring is compressed, space is created between the connector and the wear plate which allows for multi-axial movement of the prosthetic foot with respect to the pyramid coupling and the stump of the amputee. 
         [0021]    As illustrated in  FIGS. 1-4 , a prosthetic foot, indicated generally at  10 , is shown in accordance with an embodiment of the present invention. The prosthetic foot  10  can include an elongated foot member  20 , a connector, indicated generally at  40 , for coupling the prosthetic foot to the stump of an amputee, and an ankle, indicated generally at  50 . 
         [0022]    The elongated foot member  20  can include an ankle section  22  to be coupled to the limb or stump of the amputee. In one aspect, the elongated foot member  20  can extend rearwardly from the ankle section  22  to a heel section  24 , downwardly through the heel section, and forwardly through an arch section  24  to a toe section  26 . The heel section  24  can be positioned at an approximate heel location of a natural foot. Likewise, the toe section  26  can be positioned at an approximate toe location of a natural foot. The toe location can be a region near the forward end of the foot where toes of a natural foot would be located. 
         [0023]    The elongated foot member  20  can be substantially arcuate. The arc formed by the heel section  24  can be smoothly curved, or can be formed of both straight and curved sections. Thus, the elongated foot member  20  can form a curvilinear spring portion that can store and return energy to the user during walking, running, and other gait or bearing motions. 
         [0024]    The elongated foot member  20  can be formed of a composite material. In one aspect, the foot member  20  can include a graphite fiber winding or mesh and a resin material that can be shaped and cured to form the elongated foot member  20 . The foot member  20  may also be formed of other suitable materials as will be apparent to those skilled in the art. 
         [0025]    It will be appreciated that while a single member prosthetic foot  10  is shown in  FIGS. 1-4 , multiple foot member prosthetic feet can also utilize the ankle  50  described herein. For example, the ankle  50  can be used with prosthetic feet that have upper and lower forefoot members. Additionally, a heel plate or sole plate can be disposed under the lower foot member, as known and practiced in the art. 
         [0026]    The connector  40  can be coupled to the foot member  20  at the ankle section  22  and can attach to the stump of an amputee (not shown). The connector  40  can have an upper domed surface  42  and an inverted pyramid coupling  44  as is commonly used in attachment to the prepared stump of an amputee. The dome shaped upper surface  42  can facilitate articulation of the foot member  20  with respect to the stump of an amputee. The pyramid coupling  44  can fit into a corresponding socket in associated with the stump of the amputee. It will be appreciated that other types of couplings, as known in the art, can also be used with the connector of the present invention. 
         [0027]    A wear plate  60  can be disposed between the connector  40  and the foot member  20 . The wear plate  60  can be sized and shaped to protect the foot member  20  from wear due to movement between the connector  40  and the foot member  20 . The wear plate  60  can be a metal material, such as steel. Other suitable materials with sufficient rigidity and resiliency, as known in the art, are also contemplated. In this way, as the connector  40  moves under the dynamic loads induced in the prosthetic foot during motion by the amputee, the connector  40  can rub against or abrade the wear plate  60  and not the composite material of the foot member  20 . Thus, the wear plate  60  assists with wear resistance due to movement between the connector  40  and the foot  10  as the angle of the foot changes. 
         [0028]    The wear plate  60  can be shaped to facilitate rotation of the connector  40 . For example, the wear plate  60  can have a substantially spherical or dome shaped upper surface  62 . The wear plate upper surface  62  can contact a substantially flat lower surface  46  of the connector such that the substantially flat lower surface  46  of the connector  40  can pivot on the dome shaped upper surface  62  of the wear plate  60 . Additionally, the width of the wear plate is smaller than a lateral width of the connector such that the longitudinal sides  64  of the wear plate are recessed under the connector so that the connector can rotate with relative ease in a medial to lateral direction with respect to the foot member, as indicated by arrow  52  in  FIG. 2 . Moreover, the back end  66  of the wear plate can be recessed under the connector so that the connector can rotate in a heel direction, indicated by the arrow at  54  in  FIG. 1 , with relatively greater resistance than in the medial to lateral direction. Furthermore, the front end  68  of the wear plate can be substantially flush with the edge  48  of the connector so that rotation of the connector in the toe direction, indicated by the arrow at  56  in  FIG. 1 , is restricted by relatively greater resistance than rotation in either the medial to lateral direction or the heel direction. In this way, the connector can rotate with relatively little stiffness or resistance in the medial to lateral direction, relatively more stiffness or resistance in the heel direction, and relatively more stiffness and greater resistance in the toe direction. 
         [0029]    Additionally, the wear plate  60  can be shaped to vary a moment arm of the foot member  20  between toe-heel and medial-lateral loads. It will be appreciated that as weight is placed and shifted on the prosthetic foot  10  by the user, the moment arm between the application of the force on the foot member  20  and the pyramid coupling  44  of the connector  40  will change as the weight is shifted along the foot during the gait of the user. Thus, the wear plate  60  can, advantageously, be shaped to at least partially counter the length of the moment arm with respect to toe-heel and medial-lateral movement of the foot member with respect to the connector. In one aspect, the wear plate  60  can have a longer dimension which can be oriented towards the toe location to vary the moment arm of the foot member  20  between toe-heel and medial-lateral loads. 
         [0030]    A bolt or rod  70  can extend through the foot member  20  at the ankle section  22 . The rod  70  can have a spherical head  72  that can be disposed under the connector  40 . The connector  40  can be pivotally coupled to the rod  70 . In embodiments where the rod  70  includes a spherical head  72 , the connector  40  can pivot on the spherical head  72 . The rod  70  can also have a shank  74  that can extend from the spherical head  72  through an aperture  28  in the foot member  20  to an opposite side of the foot member from the spherical head. A fastener  76 , such as nut, lock nut, double nut, pin, clip, or other type of fastener, can be disposed on the shank  74  at the opposite end from the spherical head. The shank  74  can include a threaded portion, hole, indentations, or other such features which facilitate fastening the fastener  76  to the shank  74 . The fastener  76  can secure the rod  70  to the foot member  20 . Additionally, it may be desirable to utilize a washer  79  on the rod  70 , between the fastener  76  and the spring  90 . 
         [0031]    A bushing  80  can be disposed in the aperture  28  of the foot member  20  to protect the composite material of the foot member from abrasion from the shank  74  of the rod  70 . The bushing  80  can be sized and shaped to receive the shank  74  of the rod through the bushing. In one aspect, the bushing  80  can be formed of a polymeric material, such as urethane. 
         [0032]    A spring  90  can be coupled to the shank  74  of the rod  70 . The spring  90  can be removable to facilitate repair, replacement, or other maintenance. The spring  90  can be positioned on the shank  74  on the opposite side of the foot member  20  from the spherical head  72 . The fastener  76  can retain the spring  90  on the shank  74  and can compress the spring against the foot member  20 . In this way, the spring  90  can be preloaded to counteract applied loads from the foot during use by the amputee. The spring  90  can be further compressed between the fastener  76  and the foot member  20  when an axial load is applied to the rod  70  during use of the prosthetic foot  10 . 
         [0033]    In one aspect, the spring  90  can be a Belleville or cupped spring washer. In another aspect, the spring  90  can be a helical die spring  92 . The helical die spring  92  can be positioned between the fastener  76  and a washer  78 . The washer  78  can rest against the foot member  20  and can protect the composite material of the foot member from abrasive movements by the helical die spring  92 . It will be appreciated that any of a variety of suitable spring types, such as coil springs, compression springs, torsion springs, cupped spring washers, pneumatic spring cylinders, and the like can also be used. 
         [0034]    A pin  100  can be coupled to the connector  40  and disposed adjacent the wear plate  60  behind the rod  70 . The pin  100  can extend from the connector  40  into the foot member  20 . The pin  100  can be sized and shaped to restrict or reduce rotation of the foot member  20  with respect to the connector  40  about a longitudinal axis, indicated by a dashed line at  58  in  FIG. 2 , of the pyramid connector  44 . In this way, the ankle  50  of the present invention can provide medial-to-lateral rotation and heel rotation when the user is traversing uneven terrain with the prosthetic foot  10 , or when the user puts an indirect lateral or medial load on the foot as when side-stepping or turning mid-gait, while restricting spinning or rotation of the foot  10  about the longitudinal axis  58  of the pyramid coupling  44  or stump of the amputee. 
         [0035]    In use, as the user places an applied load on the foot member  20  during a gaited movement, the load produces a moment in the foot member  20 . The moment in the foot member, in turn, produces an axial tension force in the spherical head  72  of the rod  70 . The axial tension force in the rod  70  compresses the spring  90  such that the rod is pushed upward creating a space between the connector  40  and the wear plate  60 . The space between the connector  40  and the wear plate  60  allows for multi-axial rotation or pivoting movement of the foot member  20  with respect to the pyramid coupling  44  disposed on the connector  40 . Thus, as the foot  10  is dynamically loaded during the gait of the user, the foot can pivot or rotate in a toe-to-heel or medial-to-lateral direction according to the terrain or gait angle of the user. 
         [0036]    It is to be understood that the above-referenced arrangements are only illustrative of the application for the principles of the present invention. Numerous modifications and alternative arrangements can be devised without departing from the spirit and scope of the present invention. While the present invention has been shown in the drawings and fully described above with particularity and detail in connection with what is presently deemed to be the most practical and preferred embodiment(s) of the invention, it will be apparent to those of ordinary skill in the art that numerous modifications can be made without departing from the principles and concepts of the invention as set forth herein.