HK1066458B - Prosthetic foot with tunable performance - Google Patents

Description

Prosthetic foot with adjustable performance

Technical Field

The present invention relates to a high performance prosthetic foot that provides improved dynamic response capabilities, which capabilities are related to the force application mechanism.

Background

Martin et al in U.S. patent 5897594 disclose an jointless prosthetic foot for use on a leg prosthesis. Unlike previous solutions, in which the prosthetic foot has a rigid structure with joints to simulate the function of the ankle, the jointless prosthetic foot of Martin et al employs a resilient foot insertion member that is mounted inside the foot model. The insert part has a substantially C-shaped design in longitudinal section, which opens backwards and supports the prosthesis load with its upper C-limb, which load is transferred via its lower C-limb to the leaf spring connected thereto. The leaf spring has a convex design, seen from below, and extends substantially parallel to its base, forwardly beyond the foot insertion part, into the toe region. The invention of Martin et al is based on the object of improving an articulaless prosthetic foot, taking into account the shock of the heel, the elasticity, the heel-to-toe walking and the lateral stability, in order thus to carry it with it to walk in a natural way, with the aim of allowing the user to both walk normally and to carry out physical exercises and exercises. However, the dynamic response characteristics of this known prosthetic foot are limited. There is a need for a high performance prosthetic foot with an improved applied mechanical design that improves amputee athletic performance, including activities such as running, jumping, sprinting, starting, stopping and spanning, for example.

Another prosthetic foot proposed by Van L-Phillips is said to provide amputees with the flexibility and mobility to perform a variety of activities that have not been possible in the past due to the structural limitations and corresponding performance limitations of existing prostheses. Running, jumping and other activities are said to be undertaken by existing prosthetic feet, which reportedly can be used by the user in the same manner as a normal foot. See, for example, U.S. patent 6071313; 5993488, respectively; 5899944, respectively; 5800569, respectively; 5800568, respectively; 5728177, respectively; 5728176, respectively; 5824112, respectively; 5593457, respectively; 5514185, respectively; 5181932, respectively; and 4822363.

Disclosure of Invention

In order for amputee athletes to achieve a higher level of performance, there is a need for a high performance prosthetic foot having an improved application mechanism that may be superior to the human foot, and possibly superior to existing prosthetic feet. It would be of interest to amputee athletes to have a high performance prosthetic foot with improved mechanics, high low dynamic response, and alignment adjustability, and possibly fine tuning to improve the horizontal and vertical components of motion, which itself may be a special task.

According to the present invention, there is provided a prosthetic foot comprising: a longitudinally extending foot keel having an forefoot portion, a midfoot portion and a hindfoot portion; a resilient, upstanding calf shank connected at a lower end thereof to the foot keel and extending upwardly therefrom by way of a forward facing continuous convexly curved portion having a downwardly and upwardly increasing radius of curvature and being compressible and expandable in a longitudinal direction during gait to simulate plantar flexion and forefoot flexion of a human ankle joint to form an ankle joint region of the prosthetic foot and a lower prosthetic part of the leg for connection at an upper end thereof to a support structure on a human leg stump and movable in the longitudinal direction of the foot keel in response to force loading and unloading of the calf shank during use of the prosthetic foot; and a means for limiting the range of motion of the upper end of the calf shank.

According to the present invention, there is also provided a calf shank for a prosthetic foot, comprising: an elongated, semi-rigid resilient member connected at one end to a longitudinally extending foot keel of the prosthetic foot, said member extending upwardly from the foot keel by way of a forward facing continuous convexly curved portion having a downwardly and upwardly increasing radius of curvature and being compressible and expandable in a longitudinal direction during gait to simulate plantar flexion and forefoot flexion of a human ankle joint to form an ankle joint region of the prosthetic foot and a lower prosthetic portion of a leg for connection at an opposite upper end of the resilient member to a support structure on a human leg stump, said member being configured such that when connected at one end to the foot keel the member can flex in response to forces applied to and removed from the calf shank during use of the prosthetic foot such that the opposite end of the member moves longitudinally relative to the foot keel; and a means connected to the member for limiting the range of motion of the member relative to the upper end in the prosthetic foot during use thereof.

The prosthetic foot of the present invention meets the above-described needs. In accordance with one embodiment disclosed herein, the prosthetic foot of the invention comprises a longitudinally extending foot keel having an forefoot portion at one end and a hindfoot portion at an opposite end, and a longer midfoot portion extending between and upwardly arched from the forefoot and hindfoot portions. A calf shank including a downwardly convexly curved lower end is also provided. The curved lower end of the calf shank is attached to the upwardly arched midfoot portion of the foot keel in an adjustable fastening arrangement to form an ankle joint area of the prosthetic foot.

The adjustable fastening arrangement enables adjustment of the alignment of the calf shank and foot keel with respect to one another in the longitudinal direction of the foot keel for adjusting the performance of the prosthetic foot. By adjusting the alignment of the opposed upwardly arched midfoot portion of the foot keel and the downwardly convexly curved lower end of the calf shank with respect to one another in the longitudinal direction of the foot keel, the dynamic response characteristics and motion outcomes of the foot are altered to meet the particular needs of the desired/desired horizontal and vertical linear motions. A multi-purpose prosthetic foot is disclosed having high and low dynamic response capabilities, as well as biplanar motion characteristics, which improve the functional outcome of amputees engaged in athletic and/or recreational activities. A prosthetic foot particularly suited for sprinting is also disclosed.

The prosthetic foot can also include a means for limiting the range of motion of the upper end of the calf shank in response to the force loading and unloading the calf shank during use of the prosthetic foot. In one embodiment, the device is a piston-cylinder unit connected between the upper and lower ends of the calf shank and containing at least one pressurized fluid to limit the range of motion and also attenuate the energy stored or released during calf shank compression and expansion.

These and other objects, features and advantages of the present invention will be better understood upon consideration of the detailed description of the disclosed embodiments of the invention and the accompanying drawings.

Drawings

Fig. 1 is a schematic representation of two adjacent radii of curvature R1 and R2, one next to the other, of the foot keel and calf shank of the prosthetic foot of the invention, which produce the dynamic response capabilities and motion outcomes of the foot in gait in the direction of arrow B, which is perpendicular to the tangent line A joining the two radii.

Fig. 2 is a schematic view similar to fig. 1, but showing the alignment of the two radii having been altered in the prosthetic foot of the invention to increase the horizontal component of the dynamic response capability and motion output of the foot in gait and to decrease the vertical component so that arrow B1, which is perpendicular to tangent a1, is more horizontal than in the state shown in fig. 1.

Fig. 3 is a side view of a prosthetic foot according to one embodiment of the invention having a pylon adapter and pylon connected thereto for securing the foot to the lower end of an amputee's leg.

Fig. 4 is a front view of a prosthetic foot having the pylon adapter and pylon of fig. 3.

Fig. 5 is a top view of the embodiment shown in fig. 3 and 4.

Fig. 6 is a side view of another foot keel of the invention particularly suited for sprinting and which may be used in the prosthetic foot of the invention.

Figure 7 is a top view of the foot keel of figure 6.

Fig. 8 is a bottom view of the foot keel of the prosthetic foot of fig. 3 providing high low dynamic response characteristics, as well as biplanar motion capabilities.

Fig. 9 is a side view of another foot keel of the invention for a prosthetic foot particularly suited for sprinting by an amputee having a Symes amputation of the foot.

Figure 10 is a top view of the foot keel of figure 9.

Fig. 11 is another variation of the foot keel for the prosthetic foot of the invention for a Symes amputee, the foot keel providing the prosthetic foot with high low dynamic response characteristics, as well as biplanar motion capabilities.

Figure 12 is a top view of the foot keel of figure 11.

Figure 13 is a side elevational view of the foot keel of the invention wherein the thickness of the tapered portion of the keel is tapered from the midfoot portion to the hindfoot portion of the keel.

Fig. 14 is a side view of another form of the foot keel wherein the thickness tapers from the midfoot portion to both the forefoot and hindfoot portions of the foot keel.

Fig. 15 is a side view of the anterior surface of a calf shank of the prosthetic foot of the invention from a slightly superior portion to a parabola shape, the thickness of the calf shank decreasing toward its upper end.

Fig. 16 is a side view similar to fig. 15, but showing another calf shank which tapers from the middle to both the upper and lower ends.

Fig. 17 is a side view of a C-shaped calf shank for the prosthetic foot, the calf shank thickness tapering from its middle portion to both the upper and lower ends.

Fig. 18 is a side view of another example of a C-shaped calf shank for the prosthetic foot, the calf shank being progressively reduced in thickness from its midportion to its upper end.

Fig. 19 is a side view of an S-shaped calf shank for the prosthetic foot, the thickness of which is tapered from the midportion to each end.

Fig. 20 is another example of an S-shaped calf shank which is reduced in thickness only at its upper end.

Fig. 21 is a side view of a J-shaped calf shank, tapered at each end, for the prosthetic foot of the invention.

Fig. 22 is a schematic view similar to fig. 21, but showing a J-shaped calf shank which tapers in thickness only in a direction toward its upper end.

Fig. 23 is a side view, slightly above, of an alloy or plastic coupling element used in the adjustable fastening arrangement of the invention to attach the calf shank to the foot keel as shown in fig. 3.

Fig. 24 is a side and slightly forward view of a pylon adapter for connecting a foot to a pylon for connection to an amputee's leg, as used on the prosthetic foot of Figs. 3-5, and also having the foot of Figs. 28 and 29.

Fig. 25 is a side view of another prosthetic foot of the invention similar to that of fig. 3, but showing the use of a coupling element having two releasable fasteners longitudinally spaced to attach the element to the calf shank and foot keel, respectively.

Fig. 26 is an enlarged side view of the connecting member shown in fig. 25.

Fig. 27 is an enlarged side view of the calf shank of the prosthetic foot of fig. 25.

Fig. 28 is a side view of another embodiment of the prosthetic foot similar to those in Figs. 3 and 25 with a motion limiting damping device connected between the respective ends of the calf shank to limit the range of motion of the upper end of the calf shank in response to force loading and unloading of the calf shank during use of the prosthetic foot.

Fig. 29 is a front view of the prosthetic foot as seen from the left side of the prosthetic foot in fig. 28 showing the longitudinal slot in the calf shank of the foot.

Fig. 30 is a posterior view of the prosthetic foot as seen from the right side of the prosthetic foot in fig. 28.

Fig. 31 is a bottom view of the prosthetic foot of fig. 28.

Fig. 32 is a side view of the calf shank and foot keel of the prosthetic foot of fig. 28 illustrating an example of the motion of the upper end of the calf shank resulting from the force loading and unloading the calf shank during use of the prosthetic foot.

Fig. 33 is a side view of a further embodiment of the prosthetic foot similar to those in Figs. 28-32, except that a flexible strap is used to limit only the range of expansion motion of the upper end of the calf shank.

Fig. 34 is a side view of a further embodiment of the prosthetic foot with the alignment coupler device on the adapter attached to the upper end of the calf shank for securing the foot to the prosthetic socket attached to the amputee's leg, the alignment coupler device allowing medial-lateral and anterior-posterior sliding adjustment of the foot relative to the prosthetic socket.

Fig. 35 is a front view of the prosthetic foot of fig. 34, as seen from the left side of the foot shown in fig. 34.

Fig. 36 is a rear view of the prosthetic foot of fig. 34, as seen from the right side of the foot shown in fig. 34.

Fig. 37 is a top view of another foot keel for the prosthetic right foot of the invention wherein the posterior end of the foot is parallel to the anterior face, e.g., perpendicular to the longitudinal axis A-A of the foot, and the longitudinal axis F-F of the concavity of the proximal hindfoot portion is also perpendicular to the longitudinal axis A-A.

Figure 38 is a side view of the foot keel of figure 37 as viewed from the direction of the lateral side of the foot keel.

Figure 39 is a top view of the additional foot keel of the invention similar to those in figures 37 and 38 with the longitudinal axis F ' -F ' of the concavity of the proximal hindfoot portion at an obtuse angle Δ ' to the longitudinal axis A-A which makes the lateral strut of the hindfoot portion substantially longer and more flexible than the medial strut to facilitate rollover of the foot in heel contact in gait.

Figure 40 is a side view of the foot keel of figure 39 as seen from the lateral side of the foot keel.

Detailed Description

Referring to the drawings, the prosthetic foot 1 in the embodiment shown in Figs. 3-5 includes a longitudinally extending foot keel 2 having a forefoot portion 3 at one end thereof, a hindfoot portion 4 at an opposite end thereof, and an upwardly arched midfoot portion 5 extending between the forefoot and hindfoot portions. In the embodiment, midfoot portion 5 is convexly curved upward over its entire longitudinal extent between the forefoot and hindfoot portions.

The upstanding calf shank 6 of the foot 1 is attached at its downwardly convexly curved lower end 7 portion to the proximate posterior surface of the keel midfoot portion 5 by way of a releasable fastener 8 and coupling element 11. In the present embodiment, the fastener 8 is simply a bolt having a nut and washer, but could be a releasable clip or other fastener for securely positioning and retaining the calf shank to the foot keel when the fastener is tightened.

Referring to figure 8, a longitudinally extending aperture 9 is formed in the proximal posterior surface of the keel midfoot portion 5. For example, as shown in FIG. 15, a longitudinally extending aperture 10 is also formed in the curved lower end 7 of the calf shank 6. A releasable fastener 8 extends through the holes 9 and 10 which permit adjustment of the alignment of the calf shank and foot keel with respect to one another in the longitudinal direction A-A shown in fig. 5, at which time the fastener 8 is loosened or released to tailor the performance of the prosthetic foot to a particular task. Thus, the fastener 8, coupling element 11 and longitudinally extending holes 9 and 10 constitute an adjustable fastening arrangement for attaching the calf shank to the foot keel to form an ankle joint area of the prosthetic foot.

The effect of adjusting the alignment of the calf shank 6 and the foot keel 2 can be seen in Figs. 1 and 2, where the two radii R1 and R2, one next to the other, represent adjacent, facing, arched or convexly curved surfaces of the foot keel medial portion 5 and the calf shank 6. When such two radii are considered one next to the other, there is a motion capability perpendicular to the tangent line a in fig. 1 and perpendicular to the tangent line a1 in fig. 2, the tangent line being drawn between the two radii. The correlation between these two radii determines the direction of motion output. As a result, the dynamic response force application of the foot 1 depends on this relationship. The larger the radius of the recess, the higher the dynamic response capability. However, the smaller the radius, the faster it reacts.

The alignment capability of the calf shank and foot keel on the prosthetic foot of the invention enables the radii to be shifted to affect the horizontal or vertical linear velocity of the foot in athletic activities. For example, to improve the horizontal linear velocity capability of the prosthetic foot 1, alignment changes can be made to affect the relationship of the calf shank radius and the foot keel radius. That is, to improve the horizontal linear velocity profile, the bottom radius R2 of the foot keel is made further than its starting position in FIG. 2 as compared to FIG. 1. Thereby changing the dynamic response characteristics and making the motion output of the foot 1 more horizontal, as a result of which a greater horizontal linear velocity can be obtained by applying the same force.

The amputee can find the settings for each activity that meet his/her needs through exercise, as these needs are related to horizontal and vertical linear velocities. For example, high jump players and basketball players require a higher vertical jump height than sprinters. The coupling element 11 is a plastic or metal alloy alignment coupling (see figures 3, 4 and 23) sandwiched between the attached foot keel 2 and calf shank 6. The releasable fastening member 8 extends through an aperture 12 in the attachment member. The coupling element extends along the proximal, posterior surface attachment portion of the calf shank and the keel midfoot portion 5.

The curved lower end 7 of the calf shank 6 is parabolic in shape with the smallest radius of curvature of the parabola located at its lower end and extending initially anteriorly and then upwardly on the parabola shape. As shown in fig. 3, a posterior facing concavity is formed by the curvature of the calf shank. The parabolic shape has the advantage of having a higher dynamic response characteristic which produces improved horizontal linear velocity associated with a larger radius proximal end while having a smaller radius of curvature at its lower end for faster response characteristics. As explained in fig. 1 and 2, the larger radius of curvature of the parabolic shape at its upper end causes the tangent line a to remain more vertical as the alignment changes, which can result in improved horizontal linear velocity.

The parabolic shaped calf shank corresponds to the initial ground contact force in human gait by compressing or coiling on itself. This results in a smaller radius of the parabolic curve and, as a result, a reduced resistance to compression. In contrast, when the parabolic shaped calf shank responds to heel off Ground Reaction Force (GRF) in human gait by expanding, this makes the radius of the parabolic curve larger and as a result, its resistance is much greater than the aforementioned compressive resistance. These resistances are associated with the human anterior and posterior calf muscle function in human gait. Upon initial contact with the plane of the person's foot, the smaller anterior calf muscle group responds to the GRF by contracting eccentrically so as to lower the foot onto the ground and produce dorsiflexion motion. From foot flat to heel off, the larger rear calf muscle group responds to GRF by eccentrically contracting and a larger plantar flexion motion is created. The magnitude of this movement is related to the difference in size of the anterior and posterior muscle groups of the lower leg. As a result, the resistance of the posterior calf shank to dorsiflexion and plantar flexion movements in gait is mimicked and normal gait is achieved. The variable resistance capability of the parabolic curve mimics the human calf muscle function in human gait and running and jumping activities, resulting in prosthetic efficiency.

The speed of human walking is approximately 3 miles per hour. An athlete running 4:00 minutes and a mile runs 12 miles per hour, and a 10 second, 100 meter sprint runs 21 miles per hour. This is a ratio of 1:4: 7. The horizontal component of each task is greater as the activity speed increases. As a result, the size of the prosthetic calf shank radius can be predetermined. A walker needs a parabolic curved calf shank of smaller radius than a miler and a sprinter. A sprint runner needs a parabola-shaped curved calf shank 7 times larger. This relationship shows how the parabolic radii are determined for walkers, runners and sprinters. This is important because sprinters have greater range of motion requirements and their calf shanks must be stronger in order to withstand the increased loads associated with such activities. A wider or larger parabolic calf shank will be a flatter curve, which equates to greater structural strength and greater range of motion.

Pylon adapter 13 is attached to the upper end of calf shank 6 by fasteners 14. Adapter 13 is then secured to the lower end of pylon 15 by fasteners 16. Pylon 15 is secured to the lower limb of the amputee by a support structure (not shown) attached to the residual limb of the leg.

In this embodiment, the forefoot, midfoot and hindfoot portions of the foot keel 2 are constructed from a single piece of resilient material. For example, a solid material of a plastic nature may be used which has shape-retaining characteristics when deflected by the ground reaction forces. More specifically, the foot keel and calf shank can be made of laminated composite material having reinforcing fibers laminated together with a polymer matrix material. In particular, thermosetting can be usedEpoxy laminated high strength graphite or extruded plastic used under the trademark Delran or degassed polyurethane copolymers are used to produce the foot keel and to produce the calf shank. The functional qualities associated with the material provide high strength with light weight and minimal creep. The thermosetting epoxy resin is laminated under vacuum conditions using the prosthesis industry standard. The polyurethane copolymer may be injected into a female mold and the extruded plastic article may be machined. Each material used has its advantages and disadvantages. It has been found that a laminated composite material for the foot keel and calf shank, preferably also a thermoformed (prepreg) laminated composite material produced by industry standards with reinforcing fibers and a thermoplastic polymer matrix material having excellent mechanical expansion qualities, can be preferred. A suitable commercially available composite material of this type is manufactured by Cytec Fiberite Inc. of Havre de Grace, Maryland。

The physical characteristics of the elastomeric material associated with stiffness, elasticity and strength are all determined by the thickness of the material. Thinner materials deflect more easily than thicker materials for the same density. The material used, as well as its physical characteristics, is related to the stiffness of the prosthetic foot keel and the flexibility characteristics of the calf shank. In the embodiment of Figs. 3-5, the thickness of the foot keel and calf shank are uniform or symmetrical, however, as discussed below, the thickness along the length of the components may be varied, such as by making the hindfoot and forefoot areas thinner and more sensitive to deflection in the midfoot region.

To provide a prosthetic foot 1 with high and low dynamic response capabilities, the midfoot portion 5 is formed with a longitudinal arch such that the medial aspect of the longitudinal arch has a higher dynamic response capability than the lateral aspect of the longitudinal arch. To this end, in the embodiment, the radius of the inner portion of the longitudinal arc-shaped recess is larger than the radius of the outer side thereof.

Medial and lateral sides of the longitudinal arch concavity of midfoot portion 5The relationship between the radial dimensions is also defined as the anterior and posterior plantar surface weight bearing surface portions of the foot keel 2. Line T on the front of 5 in fig. 8₁-T₂Representing the anterior plantar surface weight bearing area. Line P₁-P₂Representing the posterior plantar weight bearing surface of 5. The plantar weight bearing surface on the lateral side of the foot may be defined by T₁-P₁The distance therebetween. The plantar weight bearing surface on the medial side of the foot 2 may be defined by P₂-T₂The distance therebetween. T is₁-P₁And P₂-T₂The distance represented determines the radius size, and as a result, the correlation of the high and low dynamic responses is determined and the two lines T can be aggregated and separated₁-T₂And P₁-P₂And is affected. As a result, high and low dynamic responses can be determined in the structural design.

The rear end 17 of the hindfoot portion 4 is upwardly curved in the shape of an arc which reacts to the reaction force of the ground during impact with the heel caused by the compressive forces which absorb the impact. The heel formed by the hindfoot portion 4 has a posterior lateral corner 18 which is more posterior and lateral than the medial corner 19 to promote hindfoot eversion during the initial contact phase of gait. The anterior end 20 of the forefoot portion 3 is shaped in an upwardly curved arc to simulate the human toes being dorsiflexed in the heel-lift toe-off position of the post-stance phase of gait. Rubber or foam pads 53 and 54 are provided as cushioning material under the forefoot and hindfoot sections.

The improved biplanar motion capability of the prosthetic foot is created by the medial and lateral expansion joint holes 21 and 22 extending through the forefoot portion 3 between its dorsal and plantar surfaces. Expansion joints 23 and 24 extend forward from a respective one of the holes to the anterior edge of the forefoot portion to form medial, medial and lateral expansion struts 25-27 which create improved biplanar motion capability of the forefoot portion of the foot keel. The expansion joint holes 21 and 22 are located along line B-B in fig. 5 in the transverse plane and extend at an angle a of 35 degrees to the longitudinal axis a-a of the foot keel with the medial expansion joint hole 21 being more anterior than the lateral expansion joint hole 22.

The angle alpha of the line B-B in fig. 5 to the longitudinal axis a-a may be as small as 15 degrees and still result in a high low dynamic response. When this angle alpha changes, line T of FIG. 8₁-T₂As does the angle Z of (a). The expansion joint holes 21 and 22 as projected onto the sagittal plane are inclined at an angle of 45 degrees to the transverse plane so that the dorsal aspect of the holes is more anterior than the plantar aspect. With this construction, the distance from the releasable fastener 8 to the lateral expansion joint hole 22 is shorter than the distance from the releasable fastener to the medial expansion joint hole 21, so that the lateral portion of the prosthetic foot 1 has a shorter toe lever than the medial portion to provide high and low dynamic response capabilities to the midfoot portion. In addition, the distance from releasable fastener 8 to the lateral plantar weight bearing surface is indicated as T₁Line shorter than line T₂The distance from the releasable fastener to the medial plantar surface weight bearing surface of the prosthetic foot 1 is such that the lateral portion of the prosthetic foot 1 has a shorter toe lever than the medial portion to enable high low dynamic response of the midfoot portion.

The anterior aspect of the hindfoot portion 4 of the foot keel 2 also includes an expansion joint hole 28 extending through the hindfoot portion 4 between its dorsal and plantar surfaces. An expansion joint 29 extends posteriorly from the hole 28 to the posterior edge of the hindfoot portion to form expansion struts 30 and 31. This results in improved biplanar motion capability of the hindfoot portion of the prosthetic foot.

As shown in figure 3, the dorsal aspect of the midfoot portion 5 and forefoot portion 3 of the foot keel 2 form an upwardly directed concavity 32 which mimics in function the fifth axis of motion (ray axis displacement) of the human foot. That is, the concavity 32 has a longitudinal axis C-C which is at an angle β of 15-35 degrees to the longitudinal axis A-A of the foot keel with the medial being more anterior than the lateral to encourage fifth axis motion in gait, as in the oblique low-speed axis of rotation of the second to fifth metatarsals of the human foot.

The importance of biplanar motion capability can be appreciated when the amputee walks on uneven terrain or when the athlete steps on the inside or outside of the foot. The direction of the ground force vector changes from a sagittal direction to have a forward planar component. The ground pushes the foot medially in the opposite direction to pushing the foot laterally. As a result, the calf shank is inclined medially and its weight is placed on the medial structure of the foot keel. In response to such pressure, the medial expansion joint struts 25 and 31 of the foot keel 2 dorsiflex (deflect upward) and invert, while the lateral expansion joint struts 27 and 30 plantar flex (deflect downward) and invert. This motion attempts to place the plantar surface of the plantar plate on the ground (plantar grade).

Referring to fig. 6 and 7, another foot keel 33 of the invention, particularly for sprinting, may be used on the prosthetic foot of the invention. The center of gravity of the human body becomes oriented only in the sagittal plane at sprinting. The prosthetic foot need not have a low dynamic response characteristic. As a result, a 15-35 degree outward rotational orientation of the longitudinal axis of the forefoot, midfoot concavity as in foot keel 2 is not required. Instead, the longitudinal axis D-D of the depression would become parallel to the frontal plane, as shown in FIGS. 6 and 7. This allows the sprint foot to react only in the sagittal direction. In addition, the expansion joint holes 34 and 35 are parallel to the frontal plane in the forefoot and midfoot portions along line E-E, i.e., the lateral hole 35 is moved forward and in line with and parallel to the frontal plane of the medial hole 34. The forward end 36 of the foot keel 33 is also parallel to the frontal plane. The rear heel portion 37 of the foot keel is also parallel to the frontal plane. This change negatively impacts the multi-use capabilities of the prosthetic foot. However, their performance characteristics become more suitable for the particular task. Another modification of the sprint foot keel 33 is in the toe axis area of the forefoot portion of the foot where 15 degrees of dorsiflexion on the foot keel 2 is increased to 25-40 degrees of dorsiflexion of the foot keel 33.

Fig. 9 and 10 illustrate another foot keel 38 of the invention for a prosthetic foot particularly suited for sprinting by an amputee who has had a Symes amputation through the foot. To this end, the midfoot portion of the foot keel 38 includes a posterior, upward facing concavity 39 in which the curved lower end of the calf shank is attached to the foot keel by way of a releasable fastener. Such foot keels may be used by all lower extremity amputees. The foot keel 38 accommodates the longer residual limb associated with the Symes level amputee. Its performance characteristics are significantly faster in terms of dynamic response capability. Its use is not specific to this level of amputation. It can be used on all tibial and femoral amputations. The foot keel 40 in the embodiment of figures 11 and 12 also has a concavity 41 for a Symes amputee, the foot keel providing the prosthetic foot with high low dynamic response characteristics, as well as biplanar motion capabilities, similar to the embodiment of figures 3-5 and 8.

The functional characteristics of the several foot keels of the prosthetic foot 1 are related to their shape and design characteristics in that they are related to the concavity, convexity, radius size, expansion, compression and physical characteristics of the material, all of which are related to the reaction to ground forces during walking, running and jumping activities.

The foot keel 42 in fig. 13 is similar to the embodiment of fig. 3-5 and 8, except that the thickness of the foot keel decreases from the midfoot portion to the posterior of the hindfoot. The thickness of the foot keel 43 in fig. 14 is tapered or tapered at its anterior and posterior ends. Similar thickness variations are shown in the calf shank 44 in FIG. 15 and the calf shank 45 in FIG. 16, which can be used on the prosthetic foot 1. Each design of the foot keel and calf shank produce different functional outcomes because these functional outcomes are related to horizontal and vertical linear velocities that are characteristic of improving performance in tasks associated with various sports. The ability to accommodate a variety of calf shank designs and adjustments in the settings between the foot keel and the calf shank create a prosthetic foot calf shank relationship that gives the amputee and/or prosthetist the ability to tune the prosthetic foot for optimum performance in a particular one of a variety of athletic and recreational activities.

Other calf shanks for the prosthetic foot 1 are illustrated in Figs. 17-22 and include C-shaped calf shanks 46 and 47, S-shaped calf shanks 48 and 49 and J-shaped calf shanks 50 and 51. The upper end of the calf shank may also have a vertical end with a tapered web attached at the proximal end. A male pyramid can be bolted to and through the vertical end of the calf shank. Plastic or aluminum padding may also be provided in the elongated openings at the proximal and distal ends of the calf shank for receiving the proximal male pyramid and the distal foot keel. The prosthetic foot of the invention is a modular system, preferably made of standardized units or sizes for flexibility and versatility.

All running activities associated with the runway are performed in a counter-clockwise direction. Another optional feature of the invention takes into account forces acting on the foot moving along such a curved path. When the object moves along a curved path, centripetal acceleration acts towards the center of rotation. Newton's third law applies to this energy effect. This is an equal and opposite effect. Thus, for each "centripetal" force, there is one "centrifugal" force. The action of the centripetal force is directed towards the centre of rotation, while its reaction, the action of the centrifugal force, is directed away from the centre of rotation. If the athlete is running around a curve on a runway, centripetal force pulls the athlete towards the center of the curve while centrifugal force pulls it away from the center of the curve. To counteract the centrifugal forces that tend to lean the runner outward, the runner's body leans inward. If the runner is turning on the track in a counterclockwise direction all the time, the left side is the inside of the track. As a result, according to a feature of the present invention, the left side of the left and right prosthetic foot calf shanks can be made thinner than the right side and the amputee athlete's curve performance can be improved.

In several embodiments, the foot keels 2, 33, 38, 42, 43 are all 29 centimeters long, and are proportioned to the shoe 1 in figures 3, 4 and 5, as well as in the schematic views of several different calf shanks and foot keels. However, the skilled artisan will appreciate that the specific dimensions of the prosthetic foot may vary depending on the size, weight and other characteristics of the amputee fitted with the foot.

The operation of the prosthetic foot 1 during the walking and running stance phases of the gait cycle will be discussed below. Newton's three laws of motion, related to the laws of inertia, acceleration and reaction force, are the basis of the dynamics of motion of the foot 2. According to Newton's third law, the law of force-reaction force, the thrust of the ground pushing the foot is equal to and opposite to the thrust of the foot pushing the ground. This force is referred to as ground reaction force. Various scientific studies have been conducted on human walking, running and jumping activities. Force plate studies tell us that newton's third law appears in gait. Through the above studies, we know the direction of the ground pushing feet.

The stance phase of the walking/running activity may be further divided into deceleration and acceleration phases. When the prosthetic foot touches the ground, the foot pushes forward on the ground, while the ground pushes back the foot equally in the opposite direction, that is, the ground pushes back on the prosthetic foot. This force causes the prosthetic foot to move. The stance phase analysis of walking and running activities begins at the contact point of the posterior lateral corner 18 in fig. 5 and 18, which is more posterior and lateral than the medial part of the foot. This offset at initial contact causes the foot to evert and the calf shank to plantar flex. The calf shank is always looking for a position to transfer body weight through its shank, for example, it tends to have its long vertical component in a position opposite to ground forces. This is why the plantar flexion is moved backwards so as to oppose the ground reaction force which pushes the foot backwards.

The ground forces cause the calf shanks 44, 45, 46, 47, 50 and 51 to compress with the proximal end of the mobile posterior portion. For the calf shanks 48, 49, the distal 1/2 portion of the calf shank will compress according to the distal concavity orientation. If the distal concavity compresses in response to the GRF, the proximal concavity will expand and the entire calf shank unit will move posteriorly. The ground forces cause the calf shank to compress, moving its proximal end posteriorly. The tight radius of the lower portion of the calf shank compresses, simulating the plantar flexion of the human ankle joint, and lowers the forefoot to the ground through compression. At the same time, the posterior portion of the keel, represented by hindfoot portion 4, is pressed upwardly by compression, indicated at 17. Both of these compressive forces act as shock absorbers. This shock absorption is further enhanced by the offset posterior lateral heel 18 which can cause the foot to roll over once the calf shank has stopped moving to plantar flexion and is pushing the foot posteriorly by the ground, which also acts as a shock absorber.

The compression members of the foot keel and calf shank then begin to unload, that is, seek their original shape, and release the stored energy which causes the proximal end of the calf shank to move anteriorly in an accelerated manner. As the calf shank approaches its vertical starting condition, the ground forces change from pushing posteriorly to pushing vertically upward against the foot. Since the prosthetic foot has posterior and anterior plantar surface weight bearing areas, and these areas are connected by a long, non-weight bearing arch shaped midportion, vertically directed forces from the prosthesis will cause the long arch shaped midportion to be loaded by expansion. The rear and front load bearing surfaces are spaced apart. The vertical force is maintained in the long, arched midsection of the foot, while the temporal force is transferred from the vertical to the forward direction. The calf shank expands, resembling ankle dorsiflexion. This can result in the prosthetic foot rotating off the anterior plantar weight bearing surface. When weight unloading occurs, the long arch of the midfoot changes from expanding and looking for its original shape, which produces a simulated sudden motion of the plantar flexor muscle group. This releases the stored vertical compressive force energy into an improved expansion capacity.

The long arc of the foot keel and calf shank resist expansion of their respective structures. As a result, the calf shank is restrained from advancing and the foot begins to rotate off the anterior plantar surface weight bearing area. The expansion of the midfoot portion of the foot keel has the same high low response capabilities as the foot keels of the embodiments shown in figures 3-5 and 8, figures 11 and 12, and figures 13 and 14. Because the midfoot forefoot transition portion of the foot keel is offset 15-35 degrees outward from the long axis of the foot, the medial long arch is longer than the lateral long arch. This is important because on a normal foot, during acceleration or deceleration, the medial portion of the foot is used.

The longer medial arch of the prosthetic foot has a higher dynamic response characteristic than the lateral arch. When walking or running at slower speeds, the lateral shorter toe rod is used. The center of gravity of the body moves through a sinusoidal space. It moves medial, lateral, proximal and distal. When walking or running at a slower speed, the center of gravity of the body moves more to the medial and lateral sides than when walking or running at a higher speed. In addition, momentum or inertia is lower and the ability to overcome higher dynamic response capabilities is lower. The prosthetic foot of the invention is adapted to employ the principles described herein in a manner that applies machinery.

In addition, in the midstance phase of a person's gait cycle, the body's center of gravity is as far outboard as possible. From mid-stance to toe-off, the Body's Center of Gravity (BCG) shifts from the outside to the inside. As a result, the body's center of gravity advances over the lateral side of the foot keel 2. First (low speed), as the BCG advances forward, it moves medially (high speed) on the foot keel 2. As a result, the prosthetic foot keel 2 has an automatic transmission effect. That is, it is initially at a low speed and moves to a high speed each step the amputee takes.

The foot pushes posteriorly on the ground as the force of the ground pushes anteriorly on the foot, and the long, arch-shaped anterior profile of the midfoot portion applies this posteriorly directed force vertically on its plantar surface as the heel begins to lift. This is the most efficient and useful way to apply such force. The same occurs in the posterior aspect of the hindfoot portion of the prosthetic foot. It is also shaped so that the posterior ground forces at initial contact are opposite the plantar surface of the foot keel, perpendicular to the direction of the applied force.

Late in the heel lift, the toes leave the walking and running motion, with the axial region of the forefoot portion dorsiflexed 15-35 degrees. This upwardly extending curvature causes forward ground forces to press against this part of the foot. The resistance to such compressive forces is less than the resistance to the expansion and smooth transition that occurs during the swing phase of prosthetic foot gait and running. In the late stance phase of gait, the expanded calf shank and the expanded midfoot long arch release their stored energy, enhancing the thrust on the amputee's body center of gravity.

One of the main propulsion mechanisms in human gait is called the active propulsion phase. When the heel is raised, the body weight is in front of the supporting limb and the center of gravity is lowered. When body weight is reduced over the forefoot arch (rocker), fig. 5, line C-C, there is a downward acceleration, which results in the highest vertical force received by the body. Acceleration of the leg in front of the ankle joint associated with heel lift results in a posterior shear action against the ground. The effect is an increasing dorsiflexion torque as the center of pressure moves forward to the metatarsal head axis of rotation. This creates a fully forward landing condition that creates the primary forward force for walking. The signs of effective ankle function during active propulsion are heel lift, minimal connected motion, and an almost neutral ankle position. A stable midfoot portion is necessary for the normal sequence of heel lift.

In several of the embodiments previously mentioned, the posterior aspect of the hindfoot and forefoot portions of the foot keel incorporate expansion joint holes and expansion joint struts. The orientation of the expansion joint holes acts as a mitered hinge and improves biplanar motion capability to improve the overall contact characteristics of the plantar surface of the foot when walking in uneven terrain.

The dynamic response capabilities of the Symes foot keel as shown in FIGS. 9-12 are significantly different because such capabilities are associated with walking, running and jumping activities. The foot keels differ in 4 different ways. Including the presence of a concavity in the proximal posterior of the midfoot portion to better accommodate the Symes distal residual limb shape than flat. The concavity also lowers the height of the foot keel which accommodates the longer residual limb associated with the Symes level amputee. The alignment recess requires that the respective anterior and posterior radii of the medial portion of the curved foot keel be deeper and smaller in size. As a result, all of the midfoot long arc radii and the hindfoot radii are more compact and smaller. This significantly affects the dynamic response characteristics. Smaller radii result in lower dynamic response potential. However, the prosthetic foot responds more quickly to all of the walking, running and jumping ground forces described above. The result is a faster foot with a lower dynamic response.

With the prosthetic foot of the invention, improved task-specific motion performance can be achieved through alignment changes that can affect the vertical and horizontal components of each motion. The human foot is a multi-functional unit that can walk, run, and jump. On the other hand, the human tibial fibular calf shank structure is not a multifunctional unit. It is a simple lever that exerts its force parallel to its longitudinal proximal-distal direction during walking, running and jumping activities. It is an incompressible structure and has no potential to store energy. On the other hand, the prosthetic foot of the invention has dynamic response capabilities because such dynamic response capabilities are associated with the horizontal and vertical linear velocity components of athletic walking, running and jumping activities, and are superior to the human tibia and fibula. As a result, there is a possibility of improving the amputee's athletic performance. To this end, in accordance with the invention, the fastener 8 is loosened and the alignment of the calf shank and the foot keel with respect to one another is adjusted in the longitudinal direction of the foot keel. This variation is illustrated in figures 1 and 2. The calf shank is then secured in the adjusted position on the foot keel by the fastener 8. During this adjustment, the bolts of the fastening member 8 slide relative to one or both of the opposed, longer, longitudinally extending holes 9 and 10 in the foot keel and calf shank, respectively.

An alignment change that improves the performance characteristics of a runner in initiating contact of the foot flat with the ground during midfoot strike, for example, is one in which the foot keel is slid anteriorly relative to the calf shank and the foot plantar flexed on the calf shank. This new relationship improves the horizontal component of running. That is, the calf shank plantar flexes to the foot and the foot contacts the ground in a foot flat condition, the ground immediately pushing the foot backwards as opposed to the initial heel contact, while the foot pushes forward on the ground. Thereby causing the calf shank to move rapidly anteriorly (through expansion) and downwardly. The expansion creates a dynamic response force that resists the direction of the calf shank's initial motion. As a result, the foot rolls over the plantar surface weight-bearing area of the metatarsals. This causes the midfoot portion of the foot keel to expand, which resists more than compression. The net effect of calf shank expansion and midfoot expansion is that further anterior advancement of the calf shank is resisted, which causes the knee expander and hip expander of the user's body to move the body's center of gravity anteriorly and proximally in a more efficient manner (i.e., increased horizontal velocity). In this case, further forward and upward than in the case of a heel toe runner whose calf shank forward propulsion is less resisted by the calf shank which initially has more dorsiflexion (vertical) than a foot flat runner.

To study the function of the sprint foot, the alignment of the calf shank and foot keel was changed. The foot keel has the advantage that the longitudinal axes of all of its depressions are oriented parallel to the frontal plane. The calf shank is plantar flexed and slid posteriorly on the foot keel. This further reduces the distal arc compared to a flat foot runner, for example, with a multi-purpose foot keel similar to that shown in figures 3-5 and 8. As a result, there is greater horizontal motion potential and dynamic response in its improved horizontal capabilities.

Sprinters have a large range of motion, force and momentum (inertia), momentum being the prime mover. Since the deceleration time of the standing period is shorter than the acceleration time, a higher horizontal linear velocity is obtained. This means that at initial contact, when the toes make contact with the ground, the ground pushes the foot backward and the foot pushes the ground forward. The calf shank, with greater force and momentum, is forced to make greater flexion and downward movement than the initial contact foot flat runner. The result of the force is that the long, arch-shaped concavity of the foot is loaded by expansion and the calf shank is loaded by expansion. The expansion force is resisted to a greater extent than all other previously mentioned forces associated with running. As a result, the dynamic response capability of the foot is proportional to the force applied. The human tibia fibula calf shank response is only related to energy force potential, is a straight structure, and is not capable of storing energy. In sprinting, the expansion forces on the prosthetic foot of the invention are greater than all other previously mentioned forces associated with walking and running. As a result, the dynamic response capabilities of the foot are proportional to the applied force, and the amputee athlete's athletic performance may be enhanced compared to human body function.

The prosthetic foot 53 illustrated in fig. 25 is similar to that illustrated in fig. 3, except for the adjustable fastening arrangement between the calf shank and the foot keel and the arrangement for the upper end of the calf shank for attachment to the lower end of a pylon. In this embodiment, the foot keel 54 is adjustably connected to the calf shank 55 by way of a plastic or alloy coupling element 56. The coupling element is connected to the foot keel and calf shank by respective releasable fasteners 57 and 58 which are spaced from one another in the coupling element in a direction along the longitudinal direction of the foot keel. The fastener 58 connecting the coupling element to the calf shank is posterior to the fastener 57 connecting the foot keel and the coupling element. By increasing the effective length of the calf shank in this manner, the dynamic response capability of the calf shank can be improved. As with the other embodiments, alignment changes are made in cooperation with the longitudinally extending holes in the calf shank and foot keel.

An elongated hole 59 is provided in the upper end of the calf shank 55 for receiving the pylon 15. Once received in the hole, the pylon can be securely clamped to the calf shank by tightening bolts 60 and 61, drawing the free side edges 62 and 63 of the calf shank together along the hole. The pylon connection can be easily adjusted by loosening the bolts, telescoping the pylon to a desired position relative to the calf shank, and re-clamping the pylon in the adjusted state by tightening the bolts.

The prosthetic foot 70 illustrated in Figs. 28-32 is similar to those illustrated in Figs. 3-5, 8, 23 and 24 and Figs. 25-27, but it further includes a calf shank range of motion limiter and damping device 71 on the foot for limiting the range of motion of the upper end of the calf shank with the force applied and removed from the calf shank during use of the foot by an amputee. This feature is particularly useful in prosthetic feet having a relatively long calf shank, where the wearer is engaged in activities such as running and jumping that generate forces in the calf shank many times the wearer's weight, e.g., 5-7 times the weight for running and 11-13 times the weight for jumping. In contrast, the forces generated during walking are only 1-11/2 times the body weight.

The device 71 in this embodiment is a double acting piston cylinder unit in which a pressurised fluid, gas such as air or hydraulic liquid is provided through respective fittings 73 and 74. The device has two variable controls, one for compression and one for expansion, which adjust the allowable range of motion of the upper end of the calf shank in compression and expansion of the calf shank in both loading and unloading forces. The device 71 also attenuates the energy stored or released during calf shank compression and expansion. The opposite ends of the piston-cylinder arrangement 71 are connected to the upper end of the calf shank and the lower part of the foot, and preferably in this embodiment to the respective ends of the calf shank at pivotal connections 75 and 76, which pivotal connections 75 and 76 are preferably ball joints.

The motion of the upper end of the calf shank 72 of the foot 70 as the calf shank compresses and expands is depicted in FIG. 32. The generally parabolic shape of the calf shank is such that the upper end of the calf shank can move longitudinally relative to the foot keel 77 and the lower end of the calf shank attached thereto, such as in the direction A-A in Figs. 5 and 32, by compression and expansion of the calf shank as forces are applied and removed. Thus, in the embodiment of Figs. 28-32, improved dynamic response capabilities of the prosthetic foot are achieved.

The device 71 is not limited to the described piston-cylinder unit but may be another speed control and/or movement limiting device. For example, it is contemplated that the posterior extent of the motion limiting damping device 71 employed on the calf shank of the prosthetic foot could be a microprocessor controlled hydraulic unit with compression and expansion phase control, such as those now used to control the motion of an artificial knee joint. In this case, self-contained sensors are provided to read and adapt to the movements of the individual. By using special software and a PC, fine adjustments can be made to adapt the microprocessor controlled hydraulic unit to the amputee. Up to 50 movements per second can be measured, ensuring that the dynamic gait is as similar as possible to natural walking. Due to the responsiveness of the hydraulic unit, it is suitable for a broad spectrum of lower extremity amputees. The lithium ion battery loaded into the cell provides enough energy to operate the hydraulic cell for a full day. The compression resistance is adjusted independently of the expansion adjustment. Various integrated sensors flow gait analysis data to a self-contained microprocessor that automatically adjusts the unit's stance and swing phase characteristics 50 times per second.

This microprocessor controlled hydraulic unit of the device 71 is more responsive than a mechanical hydraulic unit. The electronically controlled compression (plantar flexion) valve was adjusted 50 times per second. The compression valve in the unit is automatically fully opened during pre-swing. As a result, the unit is extremely susceptible to buckling at low speeds in a defined area, and under similar conditions. The speed of the servo motor of the unit makes it possible to close the compression (plantar flexion) and expansion dorsiflexion valves very quickly, in response to microprocessor commands sent 50 times per second. When the valve is almost closed, the damping force of the unit becomes very high, allowing fast walking, even running. The unique prosthetist-adjustable dynamic factor allows the hydraulic unit to be optimized for all gait patterns from slow to fast, fast gait speeds and movements. This ability to "tune" the microprocessor controlled hydraulic unit to the individual's unique gait pattern allows a wide range of cadences to be achieved in the prosthetic foot with high gait efficiency and comfort. That is, the use of a microprocessor hydraulic unit as the device 71 enhances the variable cadence required by active amputees when using the prosthetic foot.

The longitudinally extending foot keel 77 of the prosthetic foot 70 in Figs. 28-32 has forefoot, midfoot and hindfoot portions like in Figs. 3 and 25. The calf shank 72 of the foot is connected to the foot keel by way of a coupling element 78 with two releasable fasteners 79 and 80 longitudinally spaced apart to connect the coupling element to the calf shank and foot keel, respectively, as in the embodiment of Figs. 25-27. The calf shank 72 includes a longitudinally extending expansion slot 81 intermediate the ends of the calf shank. The expansion joint holes 82 and 83 are located at the ends of the expansion slots. The forefoot and hindfoot portions of the foot keel are also formed with corresponding expansion channels as seen in figures 29, 30 and 31.

The prosthetic socket, which is attached to the amputee's calf stump, is attached to the upper end of the calf shank 72 by an adapter 85, which adapter 85 is secured to the upper end of the calf shank by fasteners 86 and 87 as shown. The adapter has an inverted conical connection fitting 88 connected to a web that is connected to the upper surface of the adapter. The tapered fitting is received by a complementary shaped socket fitting on the associated prosthetic socket to connect the prosthetic foot and prosthetic socket. This form of connection is shown in the embodiment of fig. 34-36.

Although the motion limiting damping device 71 in the embodiment of fig. 28-32 limits the range of motion of the upper end of the calf shank in compression and expansion of the calf shank, a similar device could be used which limits the range of motion of the upper end of the calf shank in only one of compression and expansion. The embodiment of fig. 33 shows a motion limiting damping device 84 that limits the expansion of the upper end of the calf shank using only forced loading and unloading. The device 84 here is a flexible strap that allows limited elastic extension of the strap and expansion of the calf shank without limiting the motion of the upper end of the calf shank under compression load of the calf shank.

Figs. 34-36 illustrate another calf shank 90 of the invention which can be used with the foot keel 77 of the prosthetic foot of Figs. 28-32 or with one of the other foot keels described herein. The calf shank 90 has a generally parabolic shape with a minimum radius of curvature at the lower end and extending upwardly and initially anteriorly to a relatively larger radius at its proximal end. The posterior-facing concavity is formed by the curvature of the calf shank as shown in fig. 34. The distal end of the calf shank has a longitudinally extending opening 91 which, together with the coupling element 78, the releasable fasteners 79 and 80 and the longitudinally extending opening in the foot keel, permit adjustment of the longitudinal alignment of the calf shank and foot keel with respect to one another upon loosening or releasing of the fasteners 79 or 80, thereby adjusting the performance of the prosthetic foot for a particular task.

The distal end of the calf shank 90 is more sharply curved, e.g., has a smaller radius of curvature than the calf shank 72 in Figs. 28-32, and extends upward and anteriorly over a shorter longitudinal distance. This calf shank shape is more ornamental. That is, its distal end is located more in the ankle joint area where the medial and lateral balance bars of the human foot shaped shell of the prosthetic foot can be normally positioned. The calf shank is better hidden in the prosthetic foot shell. Its functional characteristic is that it responds more quickly to initial contact ground reaction forces, although it has a lower dynamic response capability than a calf shank with a wider parabola, e.g., the longer radius of curvature described above. Thus, those active people who run and jump with the prosthetic foot will benefit by using a wider parabola or radius of curvature that provides a greater horizontal velocity.

The calf shank 90 of Figs. 34-36 also includes an aligned attachment 92 intermediate a plastic or metal adapter 93 and the lower end of a prosthetic socket 96 secured to the leg stump of the user, the adapter 93 being attached to the upper end of the calf shank by fasteners 94 and 95. For example, the user may be an above-knee or below-knee amputee. The alignment connection means comprise a pair of slides 97 and 98 arranged at right angles to each other and in a plane parallel to the ground. The relative position of the components of each slider can be adjusted by loosening the threaded fasteners 99 to adjust the respective slider 97 and 98 to change the relative orientation of the prosthetic socket to the calf shank and foot keel of the prosthetic foot. In the stance phase of gait with the prosthetic foot, the top of the adapter 93 supporting the device 92 is preferably parallel to the ground.

The top of the upper slide 98 of the device 92 has an inverted conical fitting 101 secured thereto, the fitting 101 being adjustably clamped by threaded fasteners 103 in corresponding fittings 102 on the socket 96. This connection between the fittings 101 and 102 allows for flexion/extension and abduction/adduction of the angular change between the socket and the foot. The slides of the device 92 allow medial-lateral and anterior-posterior linear sliding adjustment. Thus, the device 92 is an alignment fixture that allows the prosthetic socket to move in all directions, which affects how the ground reaction forces respond to the calf shank and foot keel mechanical structure.

The foot keel 110 of figures 37 and 38 and the foot keel 120 of figures 39 and 40 are other embodiments of foot keels that may be used in the prosthetic foot of the invention. These foot keels are for the right foot and have a similar structure except for the hindfoot portion. The medial and lateral sides of the two foot keels are the same shape. The foot keel 110 is sagittal-sectioned in the hindfoot portion, with identical lateral and medial expansion struts 111 and 112 separated by a longitudinally extending expansion joint or slot 113. The rear heel region 114 of the foot keel 110 is parallel to the front face, e.g., perpendicular to the longitudinal axis A-A of the foot keel. Similarly, the longitudinal axis F-F of the dorsal concavity 115 of the hindfoot portion of the foot keel is parallel to the frontal plane, e.g., at a right angle to the longitudinal axis A-A, i.e., the angle Δ is 90.

In contrast to the foot keel 110, the foot keel 120 is not sagittal-cut in the hindfoot portion, but rather the dorsal concavity of its hindfoot portion is cut such that the longitudinal axis F ' -F ' of the concavity is obliquely transverse to the frontal plane, e.g., such that the obtuse angle Δ ' to the longitudinal axis A-A is preferably 110 and 125, with the lateral side more anterior than the medial side. This orientation of the dorsal concavity makes the lateral expansion strut 122 thinner over a greater length than the medial expansion strut 123, and thus in fact longer and more flexible than the strut 123. This increase in flexibility makes the hindfoot portion prone to respond to initial ground contact reaction forces by rolling over, a mechanism that absorbs shock. In gait, this helps to effectively transfer forces from the body's center of gravity through the hindfoot portion of the foot keel to achieve a more normal gait pattern.

The description of the embodiments ends here. While the invention has been described in connection with various illustrative embodiments, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention. For example, the lower end of the calf shank in the prosthetic foot of the invention is not limited to being parabolic or generally parabolic, but rather can be otherwise convexly, curvilinearly shaped to produce the desired motion outcomes of the foot when connected to the foot keel to form the ankle joint area of the foot. Various features of respective ones of the several embodiments may be used in other embodiments. More particularly, reasonable variations and modifications are possible in the component parts and/or arrangements of the subject composite structure within the scope of the foregoing description, the drawings, and the appended claims without departing from the inventive concepts. In addition to variations and modifications in the component parts and/or arrangements, other uses will also be apparent to those skilled in the art.

Claims (40)

1. A prosthetic foot, comprising:

a longitudinally extending foot keel having an forefoot portion, a midfoot portion and a hindfoot portion;

a resilient, upstanding calf shank connected at a lower end thereof to the foot keel and extending upwardly therefrom by way of a forward facing continuous convexly curved portion having a downwardly and upwardly increasing radius of curvature and being compressible and expandable in a longitudinal direction during gait to simulate plantar flexion and forefoot flexion of a human ankle joint to form an ankle joint region of the prosthetic foot and a lower prosthetic part of the leg for connection at an upper end thereof to a support structure on a human leg stump and movable in the longitudinal direction of the foot keel in response to force loading and unloading of the calf shank during use of the prosthetic foot; and

a device for limiting the range of motion of the upper end of the calf shank.

2. The prosthetic foot according to claim 1, wherein the device limits anterior movement of the upper end of the calf shank.

3. The prosthetic foot according to claim 2, wherein the device also limits the posterior motion of the upper end of the calf shank.

4. The prosthetic foot according to claim 1, wherein the device comprises a piston cylinder containing at least one pressurized fluid.

5. The prosthetic foot according to claim 1, wherein the device comprises a microprocessor controlled hydraulic unit.

6. The prosthetic foot according to claim 1, wherein the means includes a flexible strap permitting limited elastic extension, the strap extending between and attached to the respective ends of the calf shank.

7. The prosthetic foot according to claim 1, wherein the calf shank includes a longitudinally extending expansion slot intermediate each end of the calf shank.

8. The prosthetic foot according to claim 7, wherein the calf shank further includes an expansion joint hole at each end of the expansion slot.

9. The prosthetic foot according to claim 1, wherein at least one of the foot keel and calf shank are formed of a laminated composite material including reinforcing fibers laminated with a polymer matrix material.

10. The prosthetic foot according to claim 9, wherein the polymer matrix material is a thermoplastic material.

11. The prosthetic foot according to claim 9, wherein the laminated composite material is thermoformed.

12. The prosthetic foot according to claim 1, wherein the lower end of the calf shank is downward convexly curved.

13. The prosthetic foot according to claim 1, further comprising an alignment coupler device attached to the upper end of the calf shank, the device having a fitting for attachment to a support structure on a person's leg stump and an adjustable slide mechanism for adjusting the medial/lateral and anterior/posterior position of the foot relative to the fitting and its attached support structure.

14. The prosthetic foot according to claim 13, further comprising an adapter for connecting the alignment coupler device to the upper end of the calf shank.

15. The prosthetic foot according to claim 1, wherein the hindfoot portion of the foot keel has a dorsal concavity with a longitudinal axis skewed relative to the frontal plane such that the lateral side of the concavity is more anterior than the medial side.

16. The prosthetic foot according to claim 1, wherein the plantar surface of the midfoot portion of the foot keel has a longitudinal arch concavity with the medial aspect of the concavity having a greater radius than the lateral aspect.

17. The prosthetic foot according to claim 1, further comprising an adjustable fastening arrangement connecting the lower end of said calf shank to the foot keel to form an ankle joint area, the fastening arrangement permitting adjustment of the alignment of said calf shank and foot keel with respect to one another in the longitudinal direction of the foot for adjusting the performance of the prosthetic foot.

18. The prosthetic foot according to claim 17, wherein the adjustable fastening arrangement includes at least one releasable fastener and a coupling element between the calf shank and the foot keel.

19. The prosthetic foot according to claim 1, wherein the lower end of the calf shank is connected to the foot keel by way of a coupling element.

20. The prosthetic foot according to claim 12, wherein the downward convexly curved lower end of the calf shank is generally parabolic in shape, with a minimum radius of curvature of said parabola lying at the lower end and extending therefrom to form said forwardly facing continuous convexly curved portion.

21. The prosthetic foot according to claim 20, wherein the lower end of the calf shank includes means for adjustably positioning the lower end relative to the longitudinal direction of the foot keel.

22. The prosthetic foot according to claim 15, wherein the distal heel portion of the foot keel is parallel to the front face.

23. The prosthetic foot according to claim 9, wherein the polymer matrix material is a thermoset material.

24. The prosthetic foot according to claim 1, further comprising a coupling element through which said resilient calf shank is connected to the foot keel.

25. A calf shank for a prosthetic foot, comprising:

an elongated, semi-rigid resilient member connected at one end to a longitudinally extending foot keel of the prosthetic foot, said member extending upwardly from the foot keel by way of a forward facing continuous convexly curved portion having a downwardly and upwardly increasing radius of curvature and being compressible and expandable in a longitudinal direction during gait to simulate plantar flexion and forefoot flexion of a human ankle joint to form an ankle joint region of the prosthetic foot and a lower prosthetic portion of a leg for connection at an opposite upper end of the resilient member to a support structure on a human leg stump, said member being configured such that when connected at one end to the foot keel the member can flex in response to forces applied to and removed from the calf shank during use of the prosthetic foot such that the opposite end of the member moves longitudinally relative to the foot keel; and

a means is attached to the member for limiting the range of motion of the member relative to the upper end in the prosthetic foot during use thereof.

26. The calf shank according to claim 25, wherein the device limits anterior movement of the opposite end of the member.

27. The calf shank according to claim 26, wherein the device also limits posterior movement of the opposite end of the calf shank.

28. The calf shank according to claim 25, wherein the device includes a piston cylinder containing at least one pressurized fluid.

29. The calf shank according to claim 25, further comprising an alignment coupler attached to the upper end of the calf shank, the coupler having a fitting for coupling with a support structure on a person's leg stump and an adjustable slide mechanism for adjusting the medial/lateral and anterior/posterior position of the foot with respect to the fitting and the support structure to which it is coupled.

30. The calf shank according to claim 29, further comprising an adapter connecting the alignment coupler device with the upper end of the calf shank.

31. The calf shank according to claim 25, wherein the device includes a flexible strap allowing limited elastic extension, the strap extending between and being connected to respective ends of the member.

32. The calf shank according to claim 25, wherein the member includes a longitudinally extending expansion slot intermediate each end thereof.

33. The calf shank according to claim 32, wherein the member further includes an expansion joint hole at each end of the expansion slot.

34. The calf shank according to claim 25, wherein the resilient member is formed of a laminated composite material including reinforcing fibers laminated with a polymer matrix material.

35. The calf shank according to claim 34, wherein the polymer matrix material is a thermoplastic material.

36. The calf shank according to claim 34, wherein the polymer matrix material is a thermoset material.

37. The calf shank according to claim 34, wherein the laminated composite material is thermoformed.

38. The calf shank according to claim 25, wherein one end of the member is convexly curved outwardly.

39. The calf shank according to claim 38, wherein the outwardly convexly curved end of the resilient member is generally parabola shaped with the smallest radius of curvature of the parabola at the end and extending therefrom to form the forwardly facing continuous convexly curved portion.

40. The calf shank according to claim 25, wherein one end of the member includes means for adjustably positioning the one end with respect to a longitudinal direction of a foot keel to which the calf shank is to be attached.