US20020040249A1 - Prosthesis with resilient ankle block - Google Patents

Abstract

An ankle block prosthesis is provided having a lower foot plate and an upper ankle plate connected by a monolithic ankle block. The foot plate, ankle plate and ankle block are generally sized to fit within a surrounding cosmesis. The foot is configured such that during a walking or running stride the wearer experiences a smooth rollover or transition of compressive forces from a heel-strike position to a toe-off position so as to provide a natural feeling foot during walking or running activities.

Description

RELATED APPLICATIONS
• This application is a continuation of application U.S. Ser. No. 09/078,450 filed May 13, 1998, now U.S. Pat. No. 5,993,488, which was a continuation of U.S. Ser. No. 08/515,557, filed Aug. 15, 1995, now U.S. Pat. No. 5,800,569, which was a continuation-in-part of U.S. Ser. No. 08/692,340 filed Aug. 5, 1996, now U.S. Pat. No. 5,728,177, which was a file-wrapper continuation of U.S. Ser. No. 08/290,339, filed Aug. 15, 1994, abandoned.[0001]
BACKGROUND OF THE INVENTION
• 1. Field of the Invention[0002]
• The present invention relates to prosthetic feet and, more particularly, to a simply constructed, low-profile prosthetic foot having enhanced dynamic performance characteristics.[0003]
• 2. Description of the Related Art[0004]
• In the prosthetics market, the conventional SACH foot has been the most widely prescribed artificial foot over the past 35 years. The SACH foot generally includes a solid ankle and cushioned heel foot mounted to a limb along an approximate hinge axis taken through the ankle. The SACH foot has been popular precisely for its simplicity, and thus economy, but includes certain drawbacks in terms of dynamic response characteristics. Specifically, the low end SACH feet do not provide much energy storage and release, as do more sophisticated prosthetic feet.[0005]
• Some patients undergo what is known in the art as a Symes amputation, where the foot is severed from the leg near the ankle region. Because the Symes patient's calf and shin function as the stump for prosthetic purposes, prosthetic devices utilized by the patient must either be relatively compact, so as to be attachable below the point of amputation, or must be configured to accommodate the patient's shin and calf while attached thereto or higher up on the wearer's leg. Prior art prostheses available to Symes patients typically include an artificial foot bonded or bolted onto the bottom end of a socket worn on a patient's stump. These compact prosthetic feet can also attach below a downwardly depending pylon secured to a socket higher up on the amputee's leg. For such compact prostheses, it is difficult to provide the level of dynamic response approximating the original ankle and foot due to the lack of vertical space available. Some attempts at providing the appropriate response characteristics of the original ankle and foot in Symes foot prosthesis involve the use of rubber cushions, or bumpers, between a lower leg and the foot. Many of these require a pivotable bolt attachment between the leg and the foot. Unfortunately, many of these rubber cushion devices have limited durability due to the difficulty in bonding the rubber portions to the solid leg or foot portions, or are relatively complex, requiring several machined parts, which adds to the cost.[0006]
• Consequently, there is a need for an inexpensive and durable Symes foot prosthesis with improved performance characteristics.[0007]
SUMMARY OF THE INVENTION
• In response to problems with the prior art, the present invention provides a simple, inexpensive prosthetic foot having a curvilinear foot element, an ankle element, and an ankle block of compressible material positioned between and connected to the foot element and ankle element. Preferably, the foot element has a length roughly equal to the length of a human foot, while the ankle element is somewhat shorter. This foot element is constructed of a resilient material capable of flexing along its length. The prosthetic foot further has an attachment member connected to the ankle element opposite the ankle block for coupling the foot to a downwardly depending leg. In one preferred embodiment, the foot element has a tapered thickness. Further, the foot element comprises uplifted heel and toe ends and an arch region therebetween.[0008]
• In the preferred embodiments, the foot element and the ankle element both comprise plates. In addition, the ankle block preferably comprises a monolithic element constructed of foam. Also, desirably, the ankle element is also capable of flexing along its length.[0009]
• In another form, the present invention provides a basic prosthetic foot having enhanced performance characteristics generally comprising a lower foot plate, an upper ankle plate, and a monolithic foam ankle block joining the two plates. Both the foot plate and the ankle plate are constructed of strong, flexible material, preferably a vinyl ester based compound. The foot plate is sized approximately equal to a human foot being replaced, while the ankle plate has a similar width but has a shorter length than the foot plate. The ankle block has a length and width approximately equal to the ankle plate and is aligned therewith. Preferably, an attachment member couples to a stump or lower-limb pylon of the wearer via a bolt. During a walking stride, the combination of the resilient ankle block and flexible plates provides a smooth rollover from a heel-strike to a toe-off position.[0010]
• Desirably, the ankle block is constructed of a high density polyurethane foam. During a walking stride, the majority of the compressive forces imparted by the wearer is absorbed by the ankle block, with a small portion being absorbed by the flexible plates themselves.[0011]
• Further advantages and applications will become apparent to those skilled in the art from the following detailed description and the drawings referenced herein.[0012]
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a perspective view of a first preferred prosthetic foot of the present invention within an outer foot cosmesis shown in phantom;[0013]
• FIG. 2 is a perspective exploded view of the prosthetic foot of FIG. 1;[0014]
• FIG. 3[0015]ais an elevational view of the prosthetic foot in a heel-strike position of a walking stride;
• FIG. 3[0016]bis an elevational view of the prosthetic foot in a flat position of a walking stride;
• FIG. 3[0017]cis an elevational view of the prosthetic foot in a heel-off position of a walking stride;
• FIG. 3[0018]dis an elevational view of the prosthetic foot in a toe-off position of a walking stride;
• FIG. 4 is a perspective view of an alternative preferred embodiment of a prosthetic foot having features of the present invention, the outer foot cosmesis being shown in phantom for illustrative purposes only;[0019]
• FIG. 5 is a perspective exploded view of the prosthetic foot of FIG. 4;[0020]
• FIG. 6 is a side elevational view of the prosthetic foot of FIG. 4 more clearly showing a foot plate having a tapered thickness along its length; and[0021]
• FIG. 7 is a graph of load (F) vs. displacement (x) of a prosthetic foot constructed in accordance with FIGS.[0022]4-6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Now with reference to FIGS. 1 and 2, a first embodiment of a[0023]prosthetic foot20 of the present invention is shown in assembled and exploded perspective views, respectively. Theprosthetic foot20 generally comprises alower foot plate22, an upper,smaller ankle plate24, and a layer or block ofresilient material26 connecting the foot plate to the ankle plate. Thefoot plate22 has a length and width roughly equal to the approximate length and width of the particular wearer's amputated foot and is sized to fit within an outerflexible cosmesis28, shown in phantom. Theankle plate24 andresilient block26 have approximately the same horizontal cross-sectional size. Theankle plate24 andresilient block26 are centered transversely with respect to and are generally positioned over the back half of thefoot plate22. Theankle block26 is sandwiched between thefoot plate22 andankle plate24, and is preferably bonded to both plates. Thefoot plate22 may also have a lowersole cushion30 providing protection for the inner surfaces of thecosmesis28 from the corners of the foot plate.
• The[0024]prosthetic foot20 is connected to a stump or lower leg pylon (not shown) of a wearer via anattachment member32. Theattachment member32 is adapted to be fastened to an upper surface of theankle plate24 and includes acoupling knob34 for mating with a coupling member on the pylon. In the illustrated embodiment, theattachment member32 comprises abase plate36, having theupstanding coupling knob34 formed integrally therewith. The attachment member further may include a pair of upstanding location pins48, which help transmit torsional forces between the pylon and thefoot prosthesis20.
• A central threaded bore[0025]38 in theknob34 receives afastening bolt40 extending upwardly through anaperture42 in theankle plate24. Theresilient block26 is preferably formed with acavity44 in its upper surface to receive the downwardly protrudingbolt head46. Of course, other attachment members can be attached via the upwardly directedfastening bolt40, as will be readily apparent to those of skill in the art. The center of thebolt40 defines anattachment axis47 which is generally aligned with the vertical centerline of an imaginary ankle so as to more faithfully simulate the location at which forces are transmitted between leg and foot. This centerline is positioned rearwardly from the longitudinal center of theankle plate24 and block26 and, preferably, approximately two-thirds of the way from the front end of theankle plate24 andankle block26. Thus, there is substantially more resilient material forward of thecenterline47, as well as theattachment member32, than to the rear.
• Both the[0026]foot plate22 and theankle plate24 are preferably constructed of fiberglass, which provides strength and flexibility. Alternatively, theplates22 and24 may be formed by a plurality of lamina embedded in a hardened, flexible polymer. In other arrangements theplates22 and24 may be formed of other materials, such as carbon fibers, as may be apparent to one skilled in the art. The desirable properties of theplates22,24 are that they are relatively resilient so as to withstand cracking upon application of repeated bending stresses, yet have sufficient flexibility to enhance the performance characteristics felt by the wearer, in conjunction with the properties of theresilient ankle block26.
• To more fully explain the improved performance characteristics of the present[0027]prosthetic foot20, FIGS. 3a-3dshow “snapshots” of a prosthetic foot in several positions of a walking stride. More particularly, FIG. 3ashows a heel-strike position, FIG. 3bshows a generally flat position, FIG. 3cshows a heel-off position, and FIG. 3dshows a toe-off position. Throughout the various positions shown for a walking stride, the presentprosthetic foot20 provides a smooth and generally life-like response to the wearer. During a walking stride, theankle block26 transmits the forces imparted thereon by thefoot plate22 andankle plate24, and experiences a gradual rollover, or migration of the compressed region, from rear to front.
• With specific reference to FIG. 3[0028]a, a first position of a walking stride generally entails a heel strike, wherein the wearer transfers all of his or her weight to the heel of the leading foot. In this case, arear portion50 of thefoot plate22 comes in contact with aground surface52, albeit through thesole cushion30 andcosmesis28. The flexible nature of thefoot plate22 allows it to bend slightly in therear portion50, but most of the compressive stresses from the weight of the wearer through theprosthetic foot20 to thefoot plate22 are absorbed by arear region54 of theankle block26. Further, a slight amount of bending may occur in arear region56 of theankle plate24, although this bending is limited by the short lever arm between the axis ofattachment47 and effective center of application of resisting force by the walking surface on thefoot20. Additionally, theankle block26 reinforces all but a small portion of therear portion50 of the foot portion against bending. Afront portion58 of theankle block26 experiences a stretching, or tension, due to the attachment along the entire lower edge of the ankle block with thefoot plate22.
• Next, in FIG. 3[0029]b, the wearer reaches a generally flat-footed position, whereby thefoot plate22 contacts theground52 along substantially its entire length, again through thesole cushion30 andcosmesis28. In this position the weight of the wearer is directed substantially downwardly, so that the compression along the length of theankle block26 is only slightly greater in therear portion54 due to the off-center application of force. Although this view freezes the compressive stress distribution as such, in reality the weight of the wearer is continually shifting from behind thecenterline47 of theattachment member32 to forward thereof. Thus, as the wearer continues through the stride, the compression of theankle block26 travels from therear portion54 toward thefront portion58. This migration of the compressed region can be termed “rollover.”
• In a next snapshot of the walking stride, FIG. 3[0030]cshows theprosthetic foot20 in a “heel-off” position. This is the instant when the wearer is pushing off usingball60 andtoe62 regions of the foot. Thus, a large compressive force is generated in thefront region58 of theankle block26, causing therear region54 to experience a large amount of separation or tension. Thefront tip64 of thefoot plate22 may bend substantially to absorb some of the compressive stresses. Likewise, thefront tip66 of theankle plate24 may bend somewhat at this point. It is important to note that although theankle block26 absorbs a majority of the compression generated by the wearer, thefoot plate64 andankle plate66 are designed to work in conjunction with the resilient ankle block and provide enhanced dynamic performance. Further, the flexing of thefoot plate64 andankle plate66 relieves some of the extreme sheer stresses applied to the interfaces between theankle block26 and plates, thus increasing the life of the bonds formed therebetween.
• In FIG. 3[0031]d, a final position of the walking stride is shown, wherein theprosthetic foot20 remains in contact with theground52, but some of the weight of the wearer is being transferred to the opposite foot, which has now moved forward. In this position, there is less bending of thefront tip64 of thefoot plate22 and less compression of thefront portion58 of theankle block26. Likewise, thefront tip66 of theankle plate24 may flex a slight amount, depending on the material and thickness utilized. The region of highest compression of theankle block26 remains at the farthestforward region58, but it is reduced from the compression level of the heel-off position of FIG. 3c. Thus, therear portion54 of theankle block26 experiences a small amount of tension or spreading.
• Although the[0032]foot plate22 is shown as substantially flat in the illustrations for the first preferred embodiment, it may alternatively be constructed with a slight arch in the center region, with the toe and heel regions being slightly upwardly curved to simulate the natural curve of the sole of a human foot as illustrated in FIGS.4-6. However, even with aflat foot plate22, thefoot20 still performs substantially better than other SACH feet.
• Referring now in detail to FIGS. 4 and 5, an alternative preferred embodiment of a[0033]prosthetic foot100 of the present invention is illustrated. Theprosthetic foot100, as shown in the assembled view of FIG. 4, generally comprises alower foot plate110, an upper,smaller ankle plate112 and aresilient ankle block114. Theresilient ankle block114 is located intermediate theankle plate112 and thefoot plate110. Thefoot plate110 has a length and width roughly equal to the approximate length and width of the particular wearer's amputated foot and is sized to fit within the outerflexible cosmesis28, shown in phantom. Theankle plate112 andankle block114 are centered transversely with respect to and are generally positioned over the back portion of thefoot plate110. Theankle plate112 andankle block114 extend substantially more forwardly of theattachment axis47 than rearwardly.
• The[0034]ankle block114 is sandwiched between thefoot plate110 and theankle plate112, as shown, and is preferably bonded to both plates. Alimit strap116 further secures thefoot plate110,resilient ankle block114 andankle plate112. Anattachment plate118 is positioned over thelimit strap116 and is generally aligned with the rear end of theankle plate112. From FIG. 5, it can be seen that theattachment plate118 preferably includes acutaway portion120 to accommodate the thickness of thelimit strap116.
• The[0035]prosthetic foot100 is attached to a socket or lower leg pylon via a bolt (not shown) which extends through acorresponding hole122 in thefoot plate110 andcoaligned holes124,128,130 formed in theankle block114, theankle plate112 and theattachment plate118, respectively. Astainless steel washer126 is received in arecess132 formed on the top of theankle block114 in order to provide a flush interface between theblock114 and theankle plate112. Other attachment means, as may be apparent to those of skill in the art, may alternately be utilized with the prosthetic foot of the present invention.
• As illustrated in FIG. 6, the[0036]foot plate110 is preferably of curvilinear shape. The thickness t along its length is tapered, and the tapered profile corresponds approximately to the weight of the amputee. That is, for a heavier amputee, the thicknesses along the length would be greater than for a lighter weight amputee. Generally, the weight groups may be classified as light, medium, or heavy.
• Table I below presents preferred groupings, as module sizes C/D/E, of cosmesis sizes corresponding to a male “A” width shoe last. The sizes are presented by length L, width B at the forefoot and width H at the heel of the cosmesis.[0037]

  TABLE I
  Cosmesis Sizes for Male “A” Width Shoe Last

  			WIDTH B	WIDTH H
  	MODULE	LENGTH L (cm)	(cm)	(cm)
  	C	22	2.88	2.19
  		23	3.00	2.25
  		24	3.12	2.31
  	D	25	3.25	2.44
  		26	3.38	2.50
  		27	3.50	2.56
  	E	28	3.62	2.69
  		29	3.75	2.75
  		30	3.88	2.81

• Table II below presents preferred module sizes for various weight groups of amputees.[0038]

  TABLE II
  Modules vs. Weight Groups

  WEIGHT GROUP

  	MODULE	LIGHT	MEDIUM	HEAVY
  	C	CL	CM	—
  	D	DL	DM	DH
  	E	—	EM	EH

• Table III below presents preferred taper thicknesses (t) for an average or “DM”[0039]size foot plate110, taken at positions spaced by distance x=1 inch (2.54 cm).

  TABLE III
  Taper Thickness t for DM Foot Plate

  	POSITION (x = 2.54 cm)	THICKNESS t (cm)
  	a	0.16
  	b	0.16
  	c	0.32
  	d	0.52
  	e	0.69
  	f	0.78
  	g	0.71
  	h	0.60
  	i	0.48
  	j	0.28

• The[0040]foot plate110 has aheel end134, toward the left in FIG. 6, is concave-upward or slightly uplifted from a horizontal plane P₁tangential to theheel end134 of thefoot plate110. Similarly, atoe end136, to the right of FIG. 6, is concave upward or somewhat uplifted from a horizontal plane P₂tangential to the front portion of thefoot plate110. Anarch section138 is formed between the heel and toe ends and is preferably concave-downward, as shown.
• It is understood that within the cosmesis[0041]28 (FIG. 4), the tangent plane P₁of theheel end134 is slightly raised a distance y relative to the tangent plane P₂of thetoe end136, as shown. The DM-sized foot plate of Table III, for example, has y=0.5 inches (1.27 cm). Thefoot plate110 is preferably 0.25 inches (0.63 cm) from the bottom or sole of thecosmesis28. Thecosmesis28 may be insert molded using an anatomically sculpted foot shape, with details and sizing based on a master pattern and/or digitized data representing typical foot sizes.
• An[0042]intermediate region138 comprising the arch portion of thefoot plate110 has the greatest thickness of thefoot plate110. The curvature of thearch region138 is defined by the cosmesis or shoe sole profile, and generally corresponds to selected ranges of human foot lengths.
• The[0043]ankle plate112 is preferably shorter in length than thefoot plate110 and has a thickness also defined by the weight group of the wearer. Theankle plate112 is also preferably formed of a flexible material so that flexing of thefoot plate110 andankle plate112 tends to relieve extreme sheer stresses applied to the interfaces between theankle block114 and theplates110,112. The preferred material for theankle plate24,112 and thefoot plate22,110 is a vinyl ester based sheet molding compound, such as Quantum #QC-8800, available from Quantum Composites of Midland, Mich.
• The[0044]ankle block114 is generally sized such that itsupper surface140 is planar and corresponds to the length and width of theankle plate112. Alower surface142 of theankle block114 is longer than itsupper surface140 and generally corresponds to the contour and size of thearch region138 of thefoot plate110. A downwardly slopingfront section144 of theankle block114 forms aface146 connecting the upper andlower surfaces140,142 of theankle block114. Theface146 forms an angle θ of approximately 15° to the vertical or to theattachment axis47, extending downwardly from theankle plate112 to thefoot plate110. Alternatively, other angles θ ranging from about 5° to about 45° may be used to achieve the benefits taught herein. The particular shape of theankle block114 causes it to distribute and transfer compression stress uniformly. The shorter length of theankle plate112 and thesloping front section144 of theankle block114 tend to reduce shear stresses occurring near the front tip of theankle plate112, which could otherwise cause undesirable delamination of thefoot100.
• For the example given in Table III for a DM-[0045]sized foot plate110, the length of theplate110 is approximately 9.05 inches (22.81 cm) and its width is about 2.0 inches (5.04 cm). Thehole122 is centered about 2.31 inches (5.82 cm) from the rear edge (position a), and the diameter is preferably 0.75 inches (1.89 cm). Thecorresponding ankle block114 for this example has a width of about 1.85 inches (4.66 cm), and the length of atop surface140 is about 4.75 inches (11.97 cm). Therecess132 is preferably 1 inch (2.54 cm) in diameter, and thehole124 is 0.63 inches (1.59 cm) in diameter. Thehole124 andrecess132 are desirably centered 1.31 inches (3.30 cm) from the rear edge of theankle block114.
• In the present example, the[0046]block114 has a preferred maximum thickness, at its front, of about 1.30 inches (3.28 cm), and its thickness tapers to a minimum of about 0.83 inches (2.09 cm). The rear of theblock114 is preferably about 1.06 inches (2.67 cm), which is less than the front of theblock114 due to the raisedheel end134 of thefoot plate110. Thecorresponding ankle plate112 in the present example is preferably about 0.22 inches (0.55 cm) thick, and approximately 4.75×1.85 inches (11.97×4.66 cm). Thehole128 is preferably about 0.41 inches (1.03 cm) in diameter.
• The[0047]attachment plate118 is sized to about 2.62×1.85 inches (6.60×4.66 cm), and has a thickness of about 0.12 inches (0.30 cm) at the front and about 0.06 inches (0.15 cm) at the rear to accommodate thestrap116. Thecutaway portion120 extends about 0.80 inches (2.02 cm) from the rear end of theplate118. Theplate hole130 is also about 0.41 inches (1.03 cm) in diameter.
• The[0048]washer126 is preferably about 0.125 inches (0.32 cm) thick and has an outer diameter of about 0.938 inches (2.36 cm) and an inner diameter of 0.406 inches (1.02 cm). Thelimit strap116 is preferably about 0.75 inches (1.89 cm) wide and forms an inner circumference of about 6.40 inches (16.13 cm) in the present example for a DM-sized foot plate110. Thestrap116 is desirably about 0.06 inches (0.15 cm) thick.
• A preferred material for the[0049]ankle block26,114 is expanded polyurethane such as Cellular Vulkolka® Pur-Cell #15-50, with a density approximately 500 kg/m³, as available from Pleiger Plastics Company of Washington, Pa. Alternatively, the ankle block may be molded or fabricated from a wide variety of other resilient materials, as desired, such as natural or synthetic rubber, plastics, honeycomb structures or other materials. Cellular foam, however, provides a desirable viscoelastic springiness for a more natural feeling stride without the drawback of limited compression associated with solid elastomeric materials. Furthermore, the cellular nature of theblock26,114 makes it lighter than solid elastomers. Foam densities between about 150 and 1500 kg/m³may be used to obtain the benefits of the invention taught herein.
• The[0050]ankle block26,114 may be provided in varying heights or thicknesses, as desired, but is most effective with a thickness of between about 1 and 3 inches (2.54 and 7.56 cm). The ankle block thus provides a relatively stiff, yet flexible ankle region which can be customized for various wearers. Heavier wearers may require a denser resilient material for the ankle block, while lighter wearers may require a less dense material or less thickness.
• The[0051]limit strap116 serves to contain or control the separation or delamination of the rear portions of thefoot plate110,ankle block114 andankle plate112 during the heel-off portion of the amputee's stride, when the rear of thefoot100 undergoes maximum tension. Thestrap116 preferably forms a snug fit around this sandwiched assembly. Thestrap116 desirably has anoverlap148 of approximately 1 inch (2.54 cm) which is sewn using a cross-stitch of heavy nylon thread. Thestrap116 may be formed of any durable material; although, woven nylon is preferred. Although thestrap116 is shown with the overlappedportion148 beneath theattachment plate118, it is understood that theoverlap148 may be positioned otherwise, such as on the outside of the foot contacting neither theattachment plate118 or thefoot plate110.
• The[0052]attachment plate118 is preferably shorter in length than theankle plate112, as shown, and is connected to the top surface of theankle plate112 at its rearward portion. The top surface of theattachment plate118 forms a mating surface for receiving a socket or the pylon of a prosthetic lower limb. A preferred material for theattachment plate118 is a urethane elastomer; although, any similar durable material may be utilized, as desired.
• The thicknesses of the[0053]foot plate110 andankle plate112 may be customized for the wearer according to his/her foot size as well as the approximate weight group of the wearer. Likewise, the material choice and size for theankle block114,limit strap116 andattachment plate118 may be varied according to the wearer's foot size and weight.
• The preferred embodiment of FIGS.[0054]4-6 provides a particularly smooth and life-like response during normal walking or running activities. The uniquely curved and slopedankle block114 transmits the forces imparted thereon by thefoot plate110 andankle plate112 such that the rollover or migration of the compressed region is even more gradual and natural as felt by the amputee. During heel strike the weight of the amputee is initially transmitted to the heel of the leading foot, and the compressive stresses are absorbed by a rear region of theankle block114. As the amputee continues through his stride, the compression of theankle block114 travels smoothly and continuously toward the front portion, giving the foot a natural feel.
• FIG. 7 is a graph of load (F) vs. displacement (x) of a prosthetic foot constructed in accordance with FIGS.[0055]4-6. The test specimen was subjected to various toe-loads applied with the foot prosthesis mounted at an angle φ of 20 degrees from vertical, as illustrated in the accompanying schematic drawing.
• Although not illustrated, the prosthetic foot of the present invention also provides enhanced performance for the wearer in inversion or eversion. Prior SACH feet were often relegated to pivoting about a horizontal axis through the ankle and had relatively little flexibility from side to side. The present invention allows the wearer to walk transversely upon sloped surfaces, for example, with the foot plate generally conforming to the terrain while the ankle plate remains relatively horizontal due to the sideways compression of the ankle block. Again, as the wearer lifts his or her foot, the ankle block resumes its original shape, thus helping the wearer as energy is stored and then released.[0056]
• It can now be appreciated that the “feel” of the present prosthetic foot is greatly enhanced by the cooperation between the foot plate, ankle plate, and ankle block. As the wearer continues through the walking stride, the dynamic response from the prosthetic foot is smooth as the ankle block compresses in different regions. Further, the flexing of the ankle and foot plates assists in smoothly transmitting the various bumps and jars found in uneven walking surfaces.[0057]
• The embodiments illustrated and described above are provided merely as examples of certain preferred embodiments of the present invention. Other changes and modifications can be made from the embodiments presented herein by those skilled in the art without departure from the spirit and scope of the invention, as defined by the appended claims.[0058]

Claims (36)

What is claimed is:

1. A prosthetic foot for providing resilient kinematic support to an amputee, said prosthetic foot comprising:

a lower foot plate element having a length from toe to heel roughly equal to that of a natural human foot being replaced, said foot plate element being formed of a monolithic composite material having an area moment of inertia about a first axis that is substantially smaller than the area moment of inertia about a second axis perpendicular to said first axis such that said foot plate element is capable of flexing along its length in a fore-and-aft direction, but not substantially in a side-to-side direction, said foot plate element defining toe and heel portions of said prosthetic foot;

an upper ankle plate element having a length shorter than said foot plate element and being separately formed of a monolithic composite material having an area moment of inertia about a first axis that is substantially smaller than the area moment of inertia about a second axis perpendicular to said first axis such that said ankle plate element is capable of flexing along its length in a fore-and-aft direction, but not substantially in a side-to-side direction, said ankle plate element and said foot plate element being spaced apart from one another along their entire length;

an ankle block comprising a compressible material having a thickness of between about 0.83 inches and about 1.30 inches, said ankle block being positioned between said ankle plate element and said foot plate element; and

an attachment member secured to said ankle plate element adapted to attach said prosthetic foot to a pylon or socket, said attachment member defining an attachment axis located posteriorly along a longitudinal center line at a point approximately two-thirds of the distance rearward along the length of said ankle plate element;

said foot plate element, said ankle plate element and said ankle block cooperating such that as said amputee walks on said foot, compression stress migrates substantially uniformly through said ankle block such that substantially smooth rollover of said foot prosthesis is achieved.

2. The prosthetic foot ofclaim 1, wherein said ankle block extends roughly said length of said ankle plate element.

3. The prosthetic foot ofclaim 1, wherein said foot plate element comprises a resilient plate formed from a plurality of laminae embedded in a hardened flexible polymer material.

4. The prosthetic foot ofclaim 3, wherein said ankle plate element comprises a resilient plate formed from a plurality of laminae embedded in a hardened flexible polymer material.

5. The prosthetic foot ofclaim 1, wherein said ankle block comprises a monolithic block formed of a relatively compliant compressible material.

6. The prosthetic foot ofclaim 5, wherein said ankle block is formed of a polyurethane material.

7. The prosthetic foot ofclaim 6, wherein said ankle block is formed of a cellular polyurethane foam having a density of between about 25-35 lbs/ft³.

8. The prosthetic foot ofclaim 1, wherein said ankle block comprises a monolithic block formed of a natural or synthetic rubber.

9. A prosthetic foot, comprising:

a monolithic foot plate having toe and heel portions and a length from toe to heel roughly equal to that of a natural human foot being replaced, said foot plate comprising a resilient multi-laminate material capable of flexing substantially along its length;

an ankle plate having a length substantially shorter than said foot plate, said ankle plate being disposed substantially above and roughly parallel to said foot plate so as to define a space therebetween;

a resilient ankle block comprising a compressible material positioned between said ankle plate and said foot plate in said space formed between said foot plate and said ankle plate; and

an attachment member secured to said ankle plate adapted to attach said prosthetic foot to a pylon or other intermediate prosthetic device, said attachment member defining an attachment axis located posteriorly along a longitudinal center line at a point such that more of said resilient ankle block is disposed forward of the attachment axis than is disposed to the rear of the attachment axis;

said foot plate, said ankle plate and said ankle block cooperating such that as said amputee walks on said foot, compression stress migrates substantially uniformly through said ankle block so as to provide substantially smooth rollover of said prosthetic foot.

10. The prosthetic foot ofclaim 9, wherein said attachment member defines an attachment axis located posteriorly along a longitudinal center line at a point approximately two-thirds of the distance rearward along the length of said ankle plate element.

11. The prosthetic foot ofclaim 9, wherein said ankle block comprises a monolithic block formed of a relatively compliant compressible material.

12. The prosthetic foot ofclaim 11, wherein said ankle block is formed of a polyurethane material.

13. The prosthetic foot ofclaim 12, wherein said ankle block has a thickness of between about 0.83 inches and about 1.30 inches.

14. The prosthetic foot ofclaim 12, wherein said ankle block is formed of a cellular polyurethane foam having a density of between about 25-35 lbs/ft³.

15. The prosthetic foot ofclaim 1, wherein said ankle block comprises a monolithic block formed of a natural or synthetic rubber.

16. A prosthetic foot, comprising:

a lower foot plate having a length and width approximately equal to that of a natural human foot being replaced, said foot plate having anterior and posterior ends and being constructed of a material capable of flexing along its length;

an upper ankle plate having a length shorter than said length of said foot plate, said ankle plate having anterior and posterior ends and being constructed of a material capable of flexing along its length, said foot plate and said ankle plate being disposed relative to one another so as to define a space therebetween;

an ankle block of compressible foam material bonded to an upper surface of said foot plate and to a lower surface of said ankle plate, said ankle plate being aligned with said ankle block and both being positioned rearward from a center of said foot plate; and

an attachment member secured to said ankle plate adapted to attach said prosthetic foot to a pylon or other intermediate prosthetic member, said attachment member defining an attachment axis located posteriorly along a longitudinal center line of said ankle plate and wherein said attachment member further comprises means for aligning said prosthetic foot relative to said pylon or socket and for transmitting torsional forces from said prosthetic foot to said pylon or socket.

17. The prosthetic foot ofclaim 16, wherein said attachment member defines an attachment axis located posteriorly along a longitudinal center line at a point approximately two-thirds of the distance rearward along the length of said ankle plate element.

18. The prosthetic foot ofclaim 16, wherein said ankle block comprises a monolithic block formed of a relatively compliant compressible material.

19. The prosthetic foot ofclaim 18, wherein said ankle block is formed of a polyurethane material.

20. The prosthetic foot ofclaim 19, wherein said ankle block has a thickness of between about 0.83 inches and about 1.30 inches.

21. A prosthetic foot for replacing a natural human foot, said prosthetic foot comprising:

an elongated lower foot plate element having a length and width roughly equal to that of said natural human foot being replaced, said foot plate element having top and bottom surfaces and being formed of a resilient material having an area moment of inertia about a first axis that is substantially smaller than the area moment of inertia about a second axis perpendicular to said first axis such that said foot plate element is capable of flexing along its length in a first direction but not substantially in a second direction;

an elongated upper ankle plate element having a length shorter than said foot plate element, said upper ankle plate element having top and bottom surfaces and being formed of a resilient material having an area moment of inertia about a first axis that is substantially smaller than the area moment of inertia about a second axis perpendicular to said first axis such that said ankle plate element is capable of flexing along its length in a first direction, but not substantially in a second direction;

an elongated monolithic block of compressible material having a top surface and a bottom surface, the bottom surface of said monolithic block being bonded to the top surface of said foot plate element such that they are substantially aligned along their respective axes of elongation, the top surface of said monolithic block being bonded to the bottom surface of said ankle plate element such that they are substantially aligned along their respective axes of elongation; and

an attachment member secured to said ankle plate element adapted to attach said prosthetic foot to a pylon or other intermediate prosthetic member, said attachment member defining an attachment axis located posteriorly along a longitudinal center line at a point approximately two-thirds of the distance rearward along the length of said ankle plate element.

22. The prosthetic foot ofclaim 21 further comprising a sole cushion secured to said bottom surface of said foot plate element.

23. The prosthetic foot ofclaim 21, wherein said ankle block comprises a single monolithic block of material having sufficient strength and resiliency such that it is capable of supporting substantially the entire weight of an amputee wearing said prosthetic foot while allowing substantially uniform migration of stress through said ankle block in response to flexing of said flexible plate members.

24. The prosthetic foot ofclaim 23, wherein said ankle block comprises a monolithic block formed of a polyurethane material.

25. The prosthetic foot ofclaim 23, wherein said ankle block has a thickness of between about 0.83 inches and about 1.30 inches.

26. The prosthetic foot ofclaim 23, wherein said ankle block is formed of a cellular polyurethane foam having a density of between about 25-35 lbs/ft³.

27. The prosthetic foot ofclaim 23, wherein said ankle block comprises a monolithic block formed of a natural or synthetic rubber.

28. A prosthetic foot for replacing a natural human foot, said prosthetic foot comprising:

a lower plate element having a length and width roughly equal to that of said natural human foot being replaced and having top and bottom surfaces, said lower plate element being formed of a monolithic composite material capable of flexing substantially along its length and having an area moment of inertia about a first axis that is substantially smaller than the area moment of inertia about a second axis perpendicular to said first axis such that said lower plate element is capable of flexing along its length in a first direction but not substantially in a second direction;

an upper plate element having a length shorter than said lower plate element and having top and bottom surfaces, said upper plate element being formed of a monolithic composite material and having an area moment of inertia about a first axis that is substantially smaller than the area moment of inertia about a second axis perpendicular to said first axis such that said upper plate element is capable of flexing along its length in a first direction, but not substantially in a second direction;

a resilient ankle member composed of a compressible material sandwiched between said lower plate element and said upper plate element, said ankle member comprising a top surface and a bottom surface, the bottom surface of said ankle member being matingly bonded to the top surface of said lower plate element, the top surface of said ankle member being matingly bonded to the bottom surface of said upper plate element, such that said lower and upper plate elements and said ankle member are thereby maintained in intimate cooperative contact with one another along their respective mating surfaces; and

an attachment member secured to said upper plate element adapted to attach said prosthetic foot to a pylon or other intermediate prosthetic member, said attachment member defining an attachment axis located along a longitudinal center line of said prosthetic foot at a point such that more of said ankle member is disposed forward of the attachment axis than is disposed rearward of the attachment axis.

29. The prosthetic foot ofclaim 28, wherein said lower plate element comprises a toe end and an uplifted heel end and an intermediate region therebetween.

30. The prosthetic foot ofclaim 29, wherein said lower plate element is tapered along at least a portion of its length so as to provide desired bending and energy storage characteristics.

31. The prosthetic foot ofclaim 30, wherein said lower plate element is tapered from a relatively thick portion proximal said intermediate region to relatively thin portions proximal said heel and toe ends.

32. The prosthetic foot ofclaim 28, wherein said attachment member comprises a base plate adapted to be fastened to an upper surface of the upper plate element and an upstanding coupling knob formed integrally therewith for securing said prosthetic foot to a pylon or other prosthetic member intermediate said prosthetic foot and the stump of an amputee.

33. The prosthetic foot ofclaim 28, wherein said ankle member comprises a single monolithic block of material having sufficient strength and resiliency such that it is capable of supporting substantially the entire weight of an amputee wearing said prosthetic foot while allowing substantially uniform migration of stress through said ankle member in response to flexing of said upper and lower plate elements.

34. The prosthetic foot ofclaim 28, wherein said ankle member comprises a monolithic block formed of a polyurethane material.

35. The prosthetic foot ofclaim 28, wherein said ankle member has a thickness of between about 0.83 inches and about 1.30 inches.

36. The prosthetic foot ofclaim 28, wherein said ankle member comprises a monolithic block formed of a natural or synthetic rubber.

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