US20020077706A1 - Energy storing foot prosthesis with improved plantar flexion - Google Patents

Abstract

A prosthetic foot characterized by an easily exchangeable auxiliary ankle member demountably attached to forefoot and sole portions, which are in turn demountably and interchangeably connected. The forefoot, heel and auxiliary ankle portions are fabricated from polymer impregnated and encapsulated laminates, including such laminates as carbon fibers and/or fiberglass or synthetic fibers such as Kevlar. The easily demountable connection of the auxiliary ankle permits interchangeability thereof to match the activity schedule of the wearer utilizing the prosthetic foot without the necessity of frequent visits to the prosthetist. A compressible member between the forefoot member and the sole member, and function blocks located between the various members provide additional adjustability. The orientation of the auxiliary ankle member and compressible member also allows for increased plantar flexion.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims the benefit of U.S. Provisional Application No. 60/229,113, filed Aug. 30, 2000, the entirety of which is hereby incorporated by reference.[0001]
BACKGROUND OF THE INVENTION
• 1. Field of the Invention[0002]
• This invention relates to foot prostheses in general, and specifically to a prosthetic foot characterized by a unitary foot and heel construction, and an auxiliary ankle construction which permits the flexibility of the prosthesis to be selectively determined and easily changed.[0003]
• 2. Background of the Invention[0004]
• Although many prosthetic devices have attempted to simulate the ambulation of a normal foot, very few of them are readily adjustable in terms of their performance characteristics. Adjustability is especially desirable among amputees who frequently participate in a variety of physical activities requiring varying levels of energy-storing and -releasing attributes.[0005]
• Certainly, some prior art devices more nearly achieve the desired ease of adjustability than do others. For example, see my U.S. Pat. No. 4,547,913 for my invention relating to a “Composite Prosthetic Foot and Leg,” U.S. Pat. No. 4,822,363 for my invention relating to a “Modular Composite Prosthetic Foot and Leg,” my U.S. Pat. No. 5,181,932 for my invention relating to a “Foot Prosthesis Having Auxiliary Ankle Construction” and U.S. Pat. No. 5,290,319 for my invention relating to a “Prosthetic Foot Incorporating Adjustable Bladders” Also my U.S. Pat. Nos. 5,037,444 and 6,071,313 discloses a prosthetic foot device with similar preferred materials and methods of manufacture, and with corresponding benefits therefrom. Each of these patents is incorporated by reference herein.[0006]
• Notwithstanding the valuable contribution and characteristics of my aforementioned patented foot prostheses and specifically the modularity thereof, the adjustment of those prostheses is relatively involved. Any adjustment of the performance characteristics of those prostheses basically requires the disassembly of a covering shroud (if present) and of structural members from each other and specifically from the pylon tube (through bolt, nut, and washer combinations, for example). After a new combination of structural members has been selected, it typically must similarly be reassembled. Disassembly of the prosthetic foot from the pylon requires a significant amount of time, effort, and money as it must be done by a prosthetist.[0007]
• Other prosthetic foot devices are even less readily adjusted, and include U.S. Pat. No. 3,335,428 to Gajdos, which attempts to duplicate the skeletal and skin structure of a natural human foot, U.S. Pat. No. 2,075,583 to Lange, which incorporates a rubber form mounted in operative relationship with a rigid metallic core, and U.S. Pat. No. 4,645,509 to Poggi, which teaches a prosthetic foot incorporating a monolithic keel or beam of relatively massive proportions intended to react to the load of an amputee's body during walking, running, jumping, and the like and to release the resultant stored energy to create foot lift and thrust complementing the amputee's natural stride.[0008]
• Moreover, the dynamic performance of many of these other prior art devices is relatively stiff and immediate, and generally cannot produce adequate plantar flexion during heel strike, while retaining sufficient stiffness for toe-off.[0009]
SUMMARY OF THE INVENTION
• It is, therefore, one object of my invention to provide a foot prosthesis which can be easily adjusted without the necessity of removing the foot from the vertical pylon of an amputee's prosthetic leg. This will allow an active amputee to participate in a wide variety of activities without the necessity of frequent visits to the prosthetist.[0010]
• In one embodiment, the present invention provides a foot prosthesis characterized by an easily removable auxiliary support member, herein also termed an auxiliary ankle, in conjunction with a primary support member, herein termed the forefoot member, and a lower support member, herein termed the sole member. The primary and lower support members are of such character as to be easily adaptable to provide size adjustment or accommodation of different spring rates to suit the size of foot, or of the stride and weight of the amputee. The auxiliary support member provides further adjustment to accommodate varying activity levels of a given amputee. The ease of removal of the auxiliary support member provides a degree of quick and easy adjustment previously unobtainable with prior prosthetics.[0011]
• These members are preferably fabricated, for example, from polymer impregnated and encapsulated laminates, including such laminates as carbon fibers and/or fiberglass or synthetic fibers such as Kevlar. Such members provide desirable energy-storing and -releasing characteristics.[0012]
• Another object of the invention is the incorporation in a prosthetic foot of the aforementioned character of compressible members in order to achieve a gradual dynamic transition, which can further improve the degree of adjustability of the prosthesis.[0013]
• The particular location of attachment of the auxiliary support member allows for increased performance. Plantar flexion can be increased by not limiting the flexibility of the forefoot portion during heel strike, yet the ankle portion is still stiffened by the auxiliary support member during toe off. The inclusion of compressible members disposed between the auxiliary support member, and the forefoot member allows for further adjustability of performance characteristics.[0014]
• Other objects and advantages of the invention will be apparent from the following specification and the accompanying drawings, which are for the purpose of illustration only.[0015]
• For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.[0016]
• All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments of the present invention will become readily apparent to those skilled in the art from the following detailed description of the preferred embodiments having reference to the attached figures, the invention not being limited to any particular preferred embodiment(s) disclosed.[0017]
BRIEF DESCRIPTION OF THE DRAWINGS
• Having thus summarized the general nature of the invention and its essential features and advantages, certain preferred embodiments and modifications thereof will become apparent to those skilled in the art from the detailed description herein having reference to the figures that follow, of which:[0018]
• FIG. 1 is a side elevation view of one preferred embodiment of a prosthetic foot;[0019]
• FIG. 2 is a side elevation view of an alternative embodiment of a prosthetic foot;[0020]
• FIG. 3 is a top view of the foot of FIG. 1;[0021]
• FIG. 4 is a front elevation view of the foot of FIG. 1;[0022]
• FIG. 5 is a top view of an alternative embodiment of a prosthetic foot;[0023]
• FIG. 6 is a front elevation view of the foot of FIG. 5.[0024]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
• Referring to the drawings, and particularly to FIG. 1, I show one preferred embodiment of a[0025]foot prosthesis10 constructed in accordance with the teachings of the invention. Thefoot10 generally includes aforefoot member80, asole member50, and anauxiliary support member86 operatively and demountably attached to each other at thearch section44. Attachment is preferably accomplished using suitable nut andbolt combinations104 associated with a load-transmittingmetallic plate106. The auxiliary member is preferably attached to the forefoot member such that the auxiliary member may add to the stiffness of the ankle portion of the forefoot member. If desired, aretaining band70 may be provided at theankle section80. Acompressible member116 may be provided between the auxiliary member, and the forefoot member.Function blocks118,120,121, and119, FIG. 2 may also be provided in order to vary the length of the effective lever arms of the various members. If indicated, the forefoot and sole portions can be permanently secured to each other, as by epoxy adhesive, a polyurethane resilient layer, or the like.
• The[0026]forefoot member80 preferably includes a substantially rigidupper attachment section40, a forward and downward curvingankle section42, an arch section,44, and adistal toe section46. Thesections40,42,44, and46 are preferably formed integrally with one another and simultaneously by the incorporation of a plurality of laminae embedded in a hardened, flexible polymer.
• In the particular embodiment shown, the[0027]sole member50 includes anattachment section58 and aheel section54 extending substantially rearward from saidattachment section58. Thesections58 and54 are preferably formed integrally with one another and simultaneously by the incorporation of a plurality of laminae embedded in a hardened, flexible polymer as described herein.
• The[0028]auxiliary support member86 includes alower section94 and anupper section88. Saidlower section94 of theauxiliary support member86 is rigidly attached to saidforefoot member80 and saidsole member50 with nut and boltcombinations104, and extends substantially rearward and upward, itsuppermost edge88 preferably terminating below saidattachment section40 of saidforefoot member80.
• In an alternative embodiment, shown in FIG. 2, the[0029]sole member50 extends substantially forward from said attachment section to theforwardmost tip48 of thefoot10, and theforefoot member80 preferably extends slightly forward from theforwardmost tip84 of theauxiliary support member86, curving slightly upwards to adistal tip45. In this alternative embodiment, ablock119 can be interposed between thetip45 of theforefoot portion80, and thetoe section52 of thesole member50.
• Resilient blocks of wedge-shaped configuration and of various size may be included, for example in the positions indicated in the drawings as[0030]118,120,121, and119, FIG. 2, such that they allow for the variability of the lever arms of thestructural members80,86, and50. For example FIG. 1 shows ablock118 interposed between the under surface of theforward portion84 of theauxiliary ankle86 and the upper surface of thearch section44 of theforefoot member80, which has the effect of decreasing the lever arm of thetoe portion46 of theforefoot member80.
• Referring to FIGS. 3 and 4, the[0031]attachment section40 of theforefoot member80 preferably incorporates two centrally-located openings90. Theattachment section40 is substantially rigid and capable of sustaining torsional, impact and other loads impressed thereupon by thetoe portion46 andheel portion54 of the prosthesis. In addition, the inherent rigidity of theattachment section40 causes the effective transmission of the aforesaid loads imposed thereupon to a suitable ancillaryprosthetic pylon30, by bolt andnut combinations98 assembled through openings90 to apylon coupling33. Ascrew92 or other suitable attachment means secures theancillary pylon30 in thecoupling33. Those skilled in the art will recognize that a variety of other attachment means may be utilized, such as glue, rivets, tape, etc.
• In an alternative embodiment shown in FIGS.[0032]5-8, thesole member50 and part of theforefoot portion80 are bifurcated into multiple side-by-side foot portions such that they are capable of movement independent from one another. Preferably, the foot is bifurcated by the provision of a slot in said forefoot and sole portions. Astrap74 or similar expedient may be provided to limit the movement of the side-by-side foot portions relative to each other, if desired. The auxiliary ankle member described herein would also be preferably included in this embodiment. The concept of the split foot is described in detail in my U.S. Pat. No. 6,071,313 which is incorporated herein by reference.
• A[0033]compressible member116 may be disposed between saidforefoot member80 and saidauxiliary support member86. Thecompressible member116 is preferably fabricated such that it provides additional adjustment of the performance characteristics of theprosthesis10 through the variation of its degree of compressibility. For example, an inflatable bladder filled with air, CO₂or other gas could be used. In a particularly preferred embodiment of the present invention thecompressible member116 may comprise a compressible foam member. A foam member provides a low-cost compressible member for energy storage and release, and avoids the inherent potential difficulties of air bladders such as leakage and risk of puncture. The foam member also provides a slight dampening of the prosthetic foot which improves the overall response characteristics and provides a more natural feeling foot.
• The[0034]compressible member116 may be molded or fabricated from a wide variety of resilient materials, as desired, such as natural or synthetic rubber, plastics, polyurethane, honeycomb structures or any one of a variety of other materials well known to those skilled in the art for storing and releasing energy. Cellular foam is preferred to provide a desirable spring characteristic and a more natural stride. For example, expanded polyurethane such as cellular Vulkolka PUR-CELL No. 15-50 with a density of approximately 500 kilograms per cubic meter, available from Pleiger Plastics Company of Washington, Pa., may be used to form thecompressible member116. Foam densities of between about 150 and 1500 kg/m³may also be used to obtain the benefits of the invention taught herein.
• The rear surface of the[0035]auxiliary ankle member86 is preferably allowed to slip relative to thecompressible member116 in order to allow for increased plantar flexion. Thecompressible member116 may be held in place by glue, velcro, snaps, or a variety of other methods as recognized by one skilled in the art such that the preferred slipping between theauxiliary ankle member86 and thecompressible member116 is allowed.
• Alternatively, the[0036]compressible member116 may be replaced by a substantially non-compressible friction-reducing element, or eliminated altogether. The absence of thecompressible member116 would cause the wearer to experience more resistance to motion during toe-off, while its presence allows for slower, more gradual resistance during toe-off. Either or both of these cases may be desirable depending on the activity for which the foot is needed.
• [0037]Toe pads130 and/or aheel pad126 may be disposed under thetoe section46 of theforefoot member80 and theheel section54 of thesole member50 respectively, so as to provide minor shock absorption to the prosthetic10.
• In the preferred embodiment, bolt and[0038]nut combinations104, in conjunction with the load-distributingmetallic plates106, serve to secure thesole member50 in operative relationship with theforefoot member80 of the prosthesis. This mode of affixation facilitates the assembly or dismounting of selectedsole members50 in operative relationship with selectedforefoot members80, thus permitting a wide range of different sizes and stress load response characteristics to be related to each other to accomplish the optimum functional correspondence between the primary andsole portions80 and50.
• The[0039]auxiliary ankle member86 provides further adjustability of the performance characteristics of the prosthetic10 by adding to the stiffness of theforefoot member80. Theauxiliary ankle86 is formed from fibrous laminates of the same character as the various portions of theprosthesis10. In a preferred embodiment of the present invention, theauxiliary ankle86 incorporates anattachment section94 which is operatively associated with theankle section42 of theforefoot member80 and theattachment section58 of thesole member50.
• The[0040]auxiliary ankle86 is preferably secured in operative relationship with thecurvilinear ankle section42 of theforefoot member80 through the aforementioned assembly of the bolt andnut combinations104. On its end opposite from theattachment section94,ankle member86 has anupper section92 which is preferably fixed in operative relationship with acompressible member116 and thecurvilinear ankle section42 of theforefoot member80 by the use of a flexible, yet substantiallynon-stretching strap70. Saidcompressible member116 providing a gradual dynamic transition throughout toe-off.
• The[0041]strap70 may be fabricated from a suitably tough, flexible material such as impregnated canvas or the like, and is configured and assembled with theankle section42 of theforefoot member80, theauxiliary support member86, and/or thecompressible member116 to achieve desired stress-storage and -release performance in the prosthesis. For example, thestrap70 may be releasably attached around theauxiliary support member86 through the provision of Velcro-type fasteners or similar expedient.
• A restraining element such as the[0042]strap70 may be incorporated at various locations on theprosthesis10 to restrict the distance that associatedstructural members86,80, and50 may move from one another in order to control the performance characteristics of said foot. For example, one skilled in the art will recognize that increased distance of motion between theauxiliary support member86 andforefoot member80 during heel strike will allow for increased plantar flexion. The retaining element may be utilized to prevent undesirable excessive loading and stressing of aparticular member86,80, or50, and/or to combine the spring-stress response characteristics of the associatedstructural members12 under certain loading conditions. For example, thestrap70 as assembled in FIG. 1 permits theauxiliary member86 to assist in raising thetoe46 of theprosthesis10 and to store and release spring energy when theheel portion54 is struck on the ground in front of the wearer. The retaining element may be either substantially elastic, or substantially static depending on the degree of relative motion desired.
• In the preferred embodiment, the[0043]auxiliary ankle member86 is secured against the relatively concave surface of thecurvilinear ankle section42, so that the anticipated upward deflection of atoe section46 of theforefoot member80, as more thoroughly described below, will eventually cause deformation of theauxiliary ankle86 as well as deformation of theankle section42, effectively combining the deformation resistance and energy storage characteristics of theauxiliary ankle member86 with those of theforefoot member80. Alternative embodiments would include securing theauxiliary ankle86 to the underside of thearch section44 and continuing to use thestrap70 to maintain the functional relationship between theauxiliary ankle86 and theforefoot member80 in order to achieve the aforedescribed desired combination of the deformation resistance and energy storage characteristics of theauxiliary ankle member86 with those of theankle section42.
• The[0044]auxiliary ankle member86 can be provided with different numbers of laminates to make it more or less compliant to loads transmitted through theforefoot member80. Consequently, when confronted with various anomalies in an amputee, such as overweight or excess activity levels, the basic structure of theforefoot member80, and more particularly theankle section42, can be materially modified to provide ankle portion action which is precisely adjusted to the needs of the amputee. Moreover, a variety ofauxiliary ankle members86 can be made available to an active amputee, allowing the flexibility of the prosthesis to be adjusted on the basis of the particular activity which the amputee is undertaking. Furthermore, the location of the point of attachment at thearch section44 allows exchange ofauxiliary ankle sections86 to be made without necessarily removing theprosthesis10 from thepylon30.
• A cosmetic cover (not shown) can be provided to shroud the[0045]prosthesis10 after the optimum assemblage of the primary andsole members80 and50 and anauxiliary ankle member86 has been accomplished. The cosmetic cover, which may be formed of low-density formed polymer, is not required to serve any ancillary shock-absorbing or other stress-isolating function since all of the loads imposed upon the prosthesis can be absorbed, transmitted and reasserted in a manner to be described in greater detail below.
• The materials from which the[0046]forefoot member80,sole member50, and theauxiliary ankle86 are formed preferably possess the ability to provide an energy-storing, resilient, spring-like effect. This is preferred because each engagement of theprosthesis10 with an adjacent surface impresses compression, torsional and other loads upon theprosthesis10 which are stored within the prosthesis and then, dependent upon the stride of the wearer, re-impressed upon said surface to achieve a natural stride conforming, ideally, in all respects to the stride of the unimpaired limb of the wearer of theprosthesis10.
• These members are preferably fabricated, for example, from polymer impregnated and encapsulated laminates. To achieve the relatively thin construction of the forefoot and[0047]sole members80 and50 and theauxiliary support member86 of theprosthesis10, the aforesaid polymers are utilized in conjunction with various laminating materials. Various types of fibrous laminae can be utilized to achieve the continuum required by the design of the forefoot andsole members80 and50 and theauxiliary support member86 to complement the stress-absorbing and storing characteristics of the polymers in which said fibrous laminae are embedded.
• Of course, there is a wide variety of fibrous reinforcements in the form of laminae available at the present time, including such inorganic fibers as glass or carbon fibers. These inorganic fibers are customarily provided in tape or sheet form and can be readily superimposed in the mold to permit them to be encapsulated in the selected polymer.[0048]
• Obviously, the number of superimposed laminae and the lengths thereof, together with the thickness of the encapsulating polymer, determine the stress characteristics of the resultant forefoot and[0049]sole members80 and50 and theauxiliary support member86 and, correspondingly, determine the total weight of theprosthesis10. As will be apparent from the discussion herein, the forefoot andsole members80 and50 and theauxiliary support member86 are designed to specifically accommodate individuals having different foot sizes, different weights and different strides and the individual design of the forefoot andsole members80 and50 and theauxiliary support member86 provides for matching, to an extent previously unknown in the art, the natural characteristics of the wearer's uninjured limb.
• Furthermore, the function blocks[0050]118,120,121 and119, FIG. 2 can be provided in different sizes and in materials having different compression characteristics so that the respective lever arms and the corresponding deflections of theheel section54 and thetoe section46 or52 may be increased or decreased.
• It will be understood by those of skill in the art that the terms such as ankle, heel portion, arch and forefoot portion are used herein as convenient references to describe the general function and/or location of the various portions of the prosthesis and are not intended to indicate that the prosthesis has a structural configuration replicating these anatomical structures of the human foot.[0051]
• Although this invention has been disclosed in the context of certain preferred embodiments and examples, it will be understood by those skilled in the art that the present invention extends beyond the specifically disclosed embodiments to other alternative embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the present invention herein disclosed should not be limited by the particular disclosed embodiments described above, but should be determined only by a fair reading of the claims that follow.[0052]

Claims (21)

What is claimed is:

1. A prosthetic foot comprising:

a primary support member capable of supporting the amputee, and of providing energy storage and release, said primary support member having a substantially vertical attachment section, an intermediate curvilinear ankle section curving downward and forward from said upper section, an arch section extending forward and downward from said ankle section, and a toe section extending substantially forward from said arch section, said toe section providing a lever arm for said foot, said upper section being non-rotatably securable to a pylon member, socket or other prosthetic leg member intermediate said foot and the stump of an amputee;

an auxiliary support member having an upper section and a lower section, said auxiliary support member being secured at said lower section thereof to said arch section of said primary support member, said auxiliary support member extending substantially rearward and upward generally along said primary support member, said upper section terminating substantially near said attachment section of said primary support member;

whereby said auxiliary support member can be removed and exchanged without removing said foot prosthesis from said prosthetic leg member.

2. The prosthetic foot ofclaim 1 additionally comprising a lower support member having an attachment section and a heel section, said attachment section of said lower support member being secured with one or both of said auxiliary support member or said primary support member at a point along said arch section of said primary support member, said lower support member extending substantially rearward such that bending stress is distributed substantially evenly throughout said lower support member during heel strike, said heel section providing a lever arm for said foot.

3. The prosthetic foot ofclaim 1 wherein a restraining element is used to limit the movement of one member of said prosthesis relative to another member.

4. The prosthetic foot ofclaim 3 wherein said restraining element is a strap of substantially flexible and non-stretchable material.

5. The prosthetic foot ofclaim 3 wherein said restraining element is a strap of substantially flexible and stretchable material.

6. The prosthetic foot ofclaim 1 additionally comprising a substantially non-compressible element of friction-reducing material disposed between said lower section of said auxiliary support member, and said toe section of said primary support member.

7. The prosthetic foot ofclaim 1 additionally comprising a resilient compressible member disposed between said upper section of said auxiliary ankle member and said ankle section of said primary support member, said compressible member being fabricated from a compressible foam.

8. The prosthetic foot ofclaim 5 wherein said compressible member comprises an inflatable bladder.

9. The prosthetic foot ofclaim 1 additionally comprising one or more compressible pads disposed on the lower surface of said prosthesis such that they provide cushioning to said prosthesis during use by the wearer.

10. The prosthetic foot ofclaim 1 additionally comprising a resilient, compressible block disposed between said lower section of said auxiliary support member, and said toe section of said primary support member such that said block will be compressed during toe-off.

11. A prosthetic foot comprising:

a primary support member capable of supporting the amputee, and of providing energy storage and release, said primary support member having a substantially vertical attachment section, an intermediate curvilinear ankle section curving downward and forward from said attachment section, and an arch section extending forward and downward from said ankle section, said upper section being non-rotatably securable to a pylon member, socket or other prosthetic leg member intermediate said foot and the stump of an amputee;

an auxiliary support member having an upper section and a lower section, said auxiliary support member being secured with said arch section of said primary support member at a point on the lower section of said auxiliary support member, said auxiliary support member extending rearward and upward substantially along said primary support member, said upper section terminating near said attachment section of said primary support member;

a lower support member having a central attachment section, a heel section extending substantially rearward from said attachment section, and a toe section extending substantially forward from said attachment section, said toe and heel sections providing lever arms for said foot, said attachment section of said lower support member being secured with said auxiliary support member and said primary support member at a point along said arch section of said primary support member;

whereby said auxiliary support member can be easily removed and exchanged without removing said foot prosthesis from said prosthetic leg member.

12. The prosthetic foot ofclaim 9 wherein a restraining element is used to limit the movement of one member of said prosthesis relative to another member.

13. The prosthetic foot ofclaim 10 wherein said restraining element is a strap of substantially flexible and non-stretchable material.

14. The prosthetic foot ofclaim 10 wherein said restraining element is a strap of substantially flexible and stretchable material.

15. The prosthetic foot ofclaim 9 additionally comprising a resilient compressible member disposed between said upper section of said auxiliary ankle member and said ankle section of said primary support member, said compressible member comprising compressible foam.

16. The prosthetic foot ofclaim 13 wherein said compressible member comprises an inflatable bladder.

17. The prosthetic foot ofclaim 9 comprising a substantially non-compressible friction-reducing element disposed between said upper section of said auxiliary ankle member and said ankle section of said primary support member.

18. The prosthetic foot ofclaim 9 additionally comprising one or more compressible pads disposed on the lower surface of said prosthesis, such that they provide cushioning to said prosthesis during use by the wearer.

19. The prosthetic foot ofclaim 9 additionally comprising a resilient, compressible block disposed between said lower section of said auxiliary support member, and said toe section of said primary support member such that said block will be compressed during toe-off.

20. The prosthetic foot ofclaim 9 wherein said arch portion of said forefoot member terminates in an upward-curving tip above said toe portion of said sole member, wherebetween a substantially resilient, compressible control block is disposed, and additionally comprising a substantially resilient, compressible control block disposed between said lower section of said auxiliary support member, and said primary support member such that said blocks would be compressed during toe-off.

21. A prosthetic foot, comprising:

a resilient forefoot member for attachment to an artificial leg;

a sole member attached to said forefoot member; and

a stiffening member removably attached to a point substantially near the lower end of said forefoot member such that it alters the resilience of said forefoot member.

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