Abstract:
An artificial ankle joint having a universal joint and shock absorbers is provided. The artificial ankle joint enables distribution of vertically applied weight of a human body to ground, and enables an artificial foot connected to the artificial ankle joint to move in multiple axial directions.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field of the Invention 
     This invention relates to a prosthetic device for a human being. The invention further relates to an artificial ankle joint, referred to herein as an artificial ankle. The invention still further relates to an artificial ankle which operates to enable an artificial foot to move in multiple axial directions. 
     2. Description of the Prior Art and Problems Solved 
     It is known that a person who loses a foot and an ankle can employ a prosthetic device to replace the lost foot and ankle to thereby enable the person to stand in an erect position and to walk without extrinsic assistance, such as by use of a cane or a crutch. 
     It is known that a natural ankle receives the weight of the body transmitted to it by the bones of the lower leg, i.e., the tibia and the fibula, and then distributes the weight to the sole of the foot and ultimately to ground. A problem encountered in the use of an artificial ankle and foot involves the capability of the combination to dampen and/or to absorb shock caused by forces generated by the weight of the body and then to distribute the weight to ground. 
     It is known that a natural ankle enables a foot to move to a toe down-heel up position, and to a toe up-heel down position. In geometric terms, the toe down position increases the angle between the front of the foot and the leg, and the toe up position decreases the angle between the front of the foot and the leg. These movements in a natural ankle are produced by rotation of the foot in a first vertical plane around a first horizontal axis which passes through the ankle and which is perpendicular to the first vertical plane. The first vertical plane, in anatomical terminology, is called a sagittal plane and is sometimes referred to as a para sagittal plane. A specific sagittal plane, called the mid-sagittal plane, or the median plane, divides the body into right and left halves. Accordingly, for purposes of this disclosure, the sagittal plane which passes through the ankle is parallel to the median plane and divides the foot into right and left halves. The toe down-heel up position is referred to as plantar flexion, and the toe up-heel down position is referred to as dorsiflexion. The bottom of the foot, the sole, is referred to as the plantar, and the top of the foot is referred to as the dorsum or dorsal. Accordingly, another problem encountered in the use of the combination of an artificial ankle and an artificial foot is the capability of the artificial foot to produce plantar flexion and dorsifiexion. 
     It is known that a natural ankle enables a foot to move in left and right directions. Such movement in a natural ankle is produced by rotation of the foot in a second vertical plane around a second horizontal axis which passes through the ankle and which is perpendicular to the second vertical plane. The second vertical plane, in anatomical terminology, is called a frontal or a coronal plane. A coronal plane of interest herein divides the foot into a front portion, the toe end, and a rear portion, the heel end. The anatomical terms for the left and right movements depend upon the direction of the movement of the foot with regard to the previously mentioned median plane. Movement of the sole of the foot, the plantar, away from the median plane is called eversion, and movement of the sole of the foot, the plantar, towards the median plane is called inversion. Accordingly, still another problem encountered in the use of the combination of an artificial ankle and an artificial foot is the capability of the artificial foot to produce eversion and inversion. 
     The above mentioned first and second vertical planes are perpendicular each to the other. The intersection of the first and second vertical planes is a vertical line which passes through the ankle, and is, therefor, the line of action through which the weight of the body passes from the tibia and the fibula to the foot and ultimately to ground. 
     In addition to the intersecting first and second vertical planes, a horizontal plane, referred to as a transverse plane or an axial plane, also passes through the ankle and is perpendicular to each of the first and second vertical planes. The line of intersection of the first vertical plane and the horizontal plane is the above mentioned second horizontal axis. The second horizontal axis accordingly lies in the horizontal plane and the first vertical plane. The line of intersection of the second vertical plane and the horizontal plane is the above mentioned first horizontal axis. The first horizontal axis accordingly lies in the horizontal plane an the second vertical plane. The first and second horizontal axes are perpendicular each to the other and intersect at a point in the center of the ankle. 
     There is a need for an artificial foot having an artificial ankle with sufficient flexibility to permit distribution of vertically applied weight of the body, and to enable the artificial foot to produce plantar flexion, dorsiflexion, eversion and inversion. 
     SUMMARY OF THE INVENTION 
     This invention provides an artificial ankle which enables an artificial foot to move in multiple axial directions. Accordingly, the combination of an artificial foot and the artificial ankle of this invention enables distribution of vertically applied weight of the body to ground, and also enables rotational motions of the foot to produce plantar flexion, dorsiflexion, eversion and inversion. 
     The invention is an article of manufacture broadly comprised of an artificial ankle, further comprised of an artificial ankle and an artificial foot and still further comprised of an artificial ankle, an artificial foot and a pylon, wherein the artificial ankle is situated intermediate the artificial foot and the pylon. 
     The artificial ankle has a top side, a bottom side, a front end and a rear end. The top side of the ankle is adapted for connection to the pylon, and the bottom side of the ankle is adapted for connection to the top side of the artificial foot. 
     The artificial ankle is comprised of a universal joint and further comprised of a bridge, a universal joint, a clevis and shock absorbers. For purposes of this disclosure, a universal joint is a coupling which connects rotatable shafts which are in line with each other, wherein the universal joint permits rotation in at least two, and up to three planes. A universal joint can be defined as a joint or coupling in a rigid rod that allows the rod to “bend” in any direction, and is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together, oriented at 90 degrees to each other and connected by a cross shaft. 
     The bridge includes a boss and a shackle, wherein the boss is rigidly positioned on the top side of the bridge and the shackle is rigidly positioned on the bottom side of the bridge. The shackle is representative of a rod which is connected to one of the pair of hinges in the universal joint. The clevis is representative of a rod which is connected to the second of the pair of hinges in the universal joint. The universal joint useful herein thus features rotatable connections to a shackle and rotatable connections to a clevis, wherein the connections are separated at 90 degree intervals. The mode of coupling the shackle and the clevis by means of the universal joint, as disclosed in this invention, enables the clevis to rotate in the sagittal plane around the first horizontal axis (to thereby produce plantar flexion and dorsiflexion), and enables the clevis to rotate in the frontal plane around the second horizontal axis (to thereby produce eversion and inversion). The universal joint further enables rotation of the clevis in a third plane which such rotation is a combination of rotation in the sagittal plane and the frontal plane. 
     In one embodiment, the universal joint can be a pair of perpendicularly opposed connected axles, wherein one of the pair of axles is rotatably attached to the shackle and the second of the pair of axles is rotatably attached to the clevis. 
     In another embodiment, the universal joint is a ball wherein the shackle is rotatably attached to a first axle extending from opposite sides of the ball and the clevis is rotatably attached to a second axle extending from opposite sides of the ball. The first axle and the second axle each lie in the same plane and are perpendicular each to the other. For purposes of this disclosure, the universal joint in the form of the described ball is referred to as a ball joint. 
     In one embodiment, the artificial ankle includes two shock absorbers positioned on the bottom of the bridge. In this regard, the bottom of the bridge includes pockets for retaining the shock absorbers, which can be coil springs, in operating contact with the bridge. The coil springs are identical wherein the first spring is positioned in a first sleeve inserted in a first pocket on the bottom-front of the bridge, and the second spring is positioned in a second sleeve inserted in a second pocket on the bottom-rear of the bridge. The shackle is intermediate the first pocket and the second pocket. 
     The clevis, in addition to being rotatably attached to the universal joint, is adapted for connecting the ankle to the foot. 
     In the neutral position, as defined below, the boss, the shackle, the universal joint and the clevis are in substantial vertical alignment, and the shackle, the clevis, the universal joint and shock absorbers are in substantial horizontal alignment. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a cross sectional side view of the artificial foot of this invention in operating connection with the artificial ankle of this invention. The section is illustrated in a sagittal plane which passes through the ball joint, wherein the front of the foot, the toe end, is situated to the right of the ball joint and the rear of the foot, the heel end, is situated to the left of the ball joint. 
         FIG. 2  is a cross sectional end view of the artificial foot of this invention taken in the direction of cut line  2 - 2  of  FIG. 1 . The section is illustrated in a frontal plane which passes through the ball joint and shows the artificial foot in operating connection with the artificial ankle of this invention. 
         FIG. 3  is an exploded view of the artificial ankle shown in  FIG. 1  and illustrates the components of the artificial ankle. 
         FIG. 4  is taken in the direction of lines B-B of  FIG. 3 .  FIG. 4  is the end view of the clevis of the artificial ankle and illustrates the connection of the clevis to the ball joint. 
         FIG. 5  is a side view of the assembled components of  FIG. 3 . 
         FIG. 6  is the front view of  FIG. 5 . 
         FIG. 7  is the rear view of  FIG. 5 . 
         FIG. 8  is a sectional view of the connection of the artificial ankle of this invention to the pylon. 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  illustrate the article of manufacture of this invention comprised of artificial ankle  1  in operating connection with artificial foot  2 . The combination of ankle  1  and foot  2  is shown to be in the neutral position, that is, the combination is not in plantar flexion nor in dorsiflexion and is not in eversion position nor in inversion position. 
     As shown in  FIGS. 1 ,  2  and  3 , artificial ankle  1  is comprised of bridge  3 , clevis  4 , ball joint  5 , coil spring  6 , coil spring  7 , sleeve  8 , sleeve  9  and flange-nut  10 . 
     Bridge  3  is a plate having dome  11  extending upwardly from the top side of the plate, and shackle  12  extending downwardly from the bottom side of the plate. Boss  13  projects upwardly from the top of dome  11 . 
     Bridge  3  further includes pocket  8   a , formed in the bottom front of bridge  3 , and pocket  9   a  formed in the bottom rear of bridge  3 . Pockets  8   a  and  9   a  are centered on the longitudinal axis of bridge  3 . Each of pockets  8   a  and  9   a  is a hole, wherein the diameter and depth of each of pockets  8   a  and  9   a  are identical. 
     The outside diameters of each of sleeves  8  and  9  are sized to permit each sleeve to be slidably inserted into each pocket  8   a  and  9   a , respectively, and preferably to produce a friction fit between the wall of each pocket and the outside wall of each sleeve. 
     As seen in  FIGS. 1 ,  2 ,  5 ,  6  and  7 , boss  13 , shackle  12 , ball joint  5  and clevis  4  are in vertical alignment in both the sagittal and frontal planes, which are referred to herein as the first vertical plane and the second vertical plane, respectively. Boss  13  is in the shape of a truncated pyramid and has been referred to in the art as a pyramid. 
     The mentioned horizontal plane passes through the center of ball joint  5 , and intersects each of the first and second vertical planes which also pass through the center of ball joint  5 . The intersection of the first vertical plane and the second vertical plane is a vertical line which passes through the center of ball joint  5 . The intersection of the horizontal plane and the second vertical plane is the first horizontal axis. The intersection of the horizontal plane and the first vertical plane is the second horizontal axis. The mentioned first and second horizontal axes are perpendicular each to the other and intersect at the center of ball joint  5 . Each horizontal axis serves as an axis of rotation around which clevis  4  rotates to produce plantar flexion, dorsiflexion, eversion and inversion. 
     Axial holes are drilled into ball  5  along each of the first and second horizontal axes. Each such hole can pass completely through ball  5  or only partly through ball  5 .  FIG. 2  shows axial holes  14  and  15  drilled into ball joint  5  along the first horizontal axis, and  FIG. 3  shows axial hole  14  drilled into ball joint  5  along the first horizontal axis. Axial holes  14  and  15 , as shown in  FIG. 2 , do not pass completely through ball joint  5 .  FIGS. 1 ,  2  and  4  show axial hole  16  drilled into ball joint  5  along the second horizontal axis. Axial hole  16  does pass completely through ball  5 . 
     As seen in  FIGS. 1 and 3 , shackle  12  comprises base  17 , which abuts the bottom of bridge  3 , and ears  18  and  19  which extend downwardly from base  17 . Horizontal hole  20  extends completely through ear  18  and horizontal hole  21  extends completely through ear  19 . Holes  20  and  21  are in alignment with hole  16  in ball joint  5 . Each of holes  20  and  21  contain internal threads. Hole  16  is not threaded. First axle  22  extends through holes  20 ,  16  and  21 . First axle  22  is threadedly attached to holes  20  and  21 , but is not attached to hole  16 . Accordingly, bridge  3  is permitted to rotate around first axle  22  in the mentioned frontal plane to enable eversion and inversion motion. 
     As seen in  FIGS. 2 and 4 , clevis  4  comprises base  23 , arm  24 , arm  25  and tang  26 . Horizontal hole  27  extends completely through arm  24  and horizontal hole  28  extends completely through arm  25 . Holes  27  and  28  are in alignment with holes  14  and  15  in ball joint  5 . Each of holes  27  and  28  contain internal threads. Holes  14  and  15  are not threaded. Second axle  29   a  extends through holes  27  and  14  and second axle  29   b  extends through holes  28  and  15 . Second axle  29   a  is threadedly attached to hole  27 , but is not attached to hole  14 . Second axle  29   b  is threadedly attached to hole  28 , but is not attached to hole  15 . Accordingly, clevis  4  is permitted to rotate around second axle  29   a - 29   b  in the mentioned sagittal plane to enable plantar flexion and dorsiflexion. 
     As can be seen in  FIG. 2 , arms  24  and  25  of clevis  4  extend above the lowest part of base  17  of shackle  12 . Accordingly, the extent of rotation of bridge  3  around first axle  22  (or expressed differently, the rotation of shackle  12  around first axle  22 ) is controlled by the distance between the inside of arm  24  and the near side of base  17  of shackle  12 , and the distance between the inside of arm  25  and the near side of base  17  of shackle  12 . Base  17  of shackle  12  thus limits rotation of shackle  12  around first axle  22  because it contacts arms  24  and  25  of clevis  4 . Similarly, as see in  FIG. 5 , the extent of rotation of clevis  4  around second axle  29   a - 29   b  is controlled by the length of ears  18  and  19  of shackle  12 . In this regard, ears  18  and  19  of shackle  12  upon rotation of clevis  4  contacts base  23  of clevis  4 . Ears  18  and  19  of shackle  12  thus limits rotation of clevis  4  around second axle  29   a - 29   b.    
       FIGS. 1 and 2  include side and end vertical section views, respectively, of an artificial jointless foot  2  comprised of upper portion  30 , lower portion  31 , and flexible covering  32 . Upper portion  30  is an incompressible wooden core, lower portion  31  is a solid, compressible cast resin and flexible covering  32  is a water proof elastomeric material. An example of an artificial jointless foot useful herein is available from Otto Bock, a German Company, under the trademark Pedilan® light foot. The example foot is modified for connection to the artificial ankle of this invention. 
     Surface  33  of upper portion  30  is parallel, in the neutral position as shown in  FIG. 1 , to the ground surface and to bridge  3  of ankle  1 . Projections  34  and  35  are solid cylinders which are rigidly attached to the bottoms of holes  36  and  37  which are drilled in upper portion  30  from surface  33 . Projections  34  and  35  extend above surface  33 . The distance from the bottom of hole  36  to the bottom of sleeve  9  is equal to the distance from the bottom of hole  37  to the bottom of sleeve  8 . 
     The materials of construction and the design features of springs  6  and  7  are identical and springs  6  and  7  are equal in length and diameter. The diameters of holes  36  and  37  are sized to permit slidable insertion therein of springs  7  and  6 , respectively. The diameters of projections  34  and  35  are sized to permit longitudinal insertion of the projections into the respective interiors of springs  6  and  7 . The longitudinal axis of hole  36  and the longitudinal axis of sleeve  9  coincide, and the longitudinal axis of hole  37  and the longitudinal axis of sleeve  8  coincide. Sleeve  8 , hole  37  and projection  34  cooperate to maintain spring  6  in operating position, and sleeve  9 , hole  36  and projection  35  cooperate to maintain spring  7  in operating position. 
     Given the existence of the conditions recited in the two preceding paragraphs, it is believed that, in the neutral position, pylon  42 , as shown in  FIG. 8 , will be perpendicular to the ground surface after it has been attached to pyramid  13  and after artificial ankle  1  has been attached to artificial foot  2 . Attachment of artificial ankle  1  to artificial foot  2  and attachment of pylon  42  to pyramid  13  is disclosed below. 
     Plate  38  is rigidly imbedded within upper portion  30  of artificial foot  2 . Hole  39  is drilled in upper portion  30  from surface  33  to plate  38 . Hole  39  is rectangular in shape and is sized to slidably receive base  23  of clevis  4 . As shown in  FIGS. 1 and 3 , the width of hole  39  is equal to or slightly greater than the distance from the inside of ear  18  of shackle  12  to the inside of ear  19  of shackle  12 , and is less than the distance from the outside of ear  18  to the outside of ear  19 . Accordingly, the depth of any slidable penetration of base  23  of clevis  4  into hole  39  is limited by contact between surface  33  and the bottoms of ears  18  and  19  of shackle  12 . 
     Circular hole  40  is drilled through plate  38 . The diameter of hole  40  is sized to enable tang  26  of clevis  4  to pass there through. Each of the length and width dimensions of hole  39  is greater than the diameter of hole  40 . 
     Circular hole  41  is drilled from the bottom of artificial foot  2  through flexible covering  32 , lower portion  31  and partially through upper portion  30  to plate  38 . The diameter of hole  41  is greater than the diameter of flange-nut  10  by an amount sufficient to enable flange-nut  10  to be placed in hole  41  against the bottom side of plate  38  and to enable flange-nut  10  to be threaded to tang  26  of clevis  4 . The vertical axes of holes  39 ,  40  and  41  are coincident. 
     Artificial ankle  1  and artificial foot  2  are assembled by first assembling the elements shown in  FIG. 3  to form the component shown in  FIG. 5 . Thereafter, tang  26  of clevis  4  is positioned for insertion into hole  40  and projections  34  and  35  are inserted into the respective interiors of springs  6  and  7 . Thereafter, force is exerted against bridge  3  to compress springs  6  and  7  by an amount sufficient to enable tang  26  to pass through hole  40 , and the applied force is maintained for a time sufficient to permit threaded attachment of flange-nut  10  to tang  26 . 
     Finally, pylon  42  is positioned over pyramid  13  as shown in  FIG. 8 . Pylon  42  is preferably a cylindrical metal tube such as model 2R49 CE available from Otto Bock. Upon being positioned as shown, pins  43 , which are threaded in pylon  42 , are tightened against each of the four sides of pyramid  13 . 
     The entire assembly is then connected to the user as is known in the art. 
     In operation, the ability of artificial foot  2  to produce plantar flexion, dorsiflexion, inversion, eversion and body weight dispersion is a function of the flexibility of artificial ankle  1 . In this regard the flexibility of artificial ankle  1  is believed to be controlled by the degree of compression of springs  6  and  7 , wherein the greater the compression the less the flexibility. Accordingly, spring compression and artificial ankle flexibility are inversely related. The extent of compression loaded in springs  6  and  7  is controlled by tension in tang  26  which is adjusted by tightening and loosening flange-nut  10 . A user can accordingly control ankle flexibility by adjusting flange-nut  10 . 
     In addition to artificial ankle flexibility discussed above, which enables movement of the artificial foot in the mentioned sagittal and coronal planes, movement of the artificial foot in the horizontal plane can be controlled by the relative sizes of the base  23  of clevis  4  and rectangular hole  39  in upper portion  30  of artificial foot  2 . If the dimensions of base  23  and hole  39  are substantially the same, then horizontal rotation of ankle  1  is very limited if not prevented. However, increasing the dimensions of hole  39  relative to the dimensions of base  23 , will permit horizontal rotation ankle  1 . A user can accordingly adjust such movement as desired.