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  
       [0001]    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. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    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.  
           [0004]    2. Background of the Invention  
           [0005]    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.  
           [0006]    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.  
           [0007]    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.  
           [0008]    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&#39;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&#39;s natural stride.  
           [0009]    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.  
         SUMMARY OF THE INVENTION  
         [0010]    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&#39;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.  
           [0011]    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.  
           [0012]    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.  
           [0013]    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.  
           [0014]    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.  
           [0015]    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.  
           [0016]    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.  
           [0017]    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. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]    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:  
         [0019]    [0019]FIG. 1 is a side elevation view of one preferred embodiment of a prosthetic foot;  
         [0020]    [0020]FIG. 2 is a side elevation view of an alternative embodiment of a prosthetic foot;  
         [0021]    [0021]FIG. 3 is a top view of the foot of FIG. 1;  
         [0022]    [0022]FIG. 4 is a front elevation view of the foot of FIG. 1;  
         [0023]    [0023]FIG. 5 is a top view of an alternative embodiment of a prosthetic foot;  
         [0024]    [0024]FIG. 6 is a front elevation view of the foot of FIG. 5. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0025]    Referring to the drawings, and particularly to FIG. 1, I show one preferred embodiment of a foot prosthesis  10  constructed in accordance with the teachings of the invention. The foot  10  generally includes a forefoot member  80 , a sole member  50 , and an auxiliary support member  86  operatively and demountably attached to each other at the arch section  44 . Attachment is preferably accomplished using suitable nut and bolt combinations  104  associated with a load-transmitting metallic plate  106 . 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, a retaining band  70  may be provided at the ankle section  80 . A compressible member  116  may be provided between the auxiliary member, and the forefoot member. Function blocks  118 ,  120 ,  121 , and  119 , 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.  
         [0026]    The forefoot member  80  preferably includes a substantially rigid upper attachment section  40 , a forward and downward curving ankle section  42 , an arch section,  44 , and a distal toe section  46 . The sections  40 ,  42 ,  44 , and  46  are preferably formed integrally with one another and simultaneously by the incorporation of a plurality of laminae embedded in a hardened, flexible polymer.  
         [0027]    In the particular embodiment shown, the sole member  50  includes an attachment section  58  and a heel section  54  extending substantially rearward from said attachment section  58 . The sections  58  and  54  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.  
         [0028]    The auxiliary support member  86  includes a lower section  94  and an upper section  88 . Said lower section  94  of the auxiliary support member  86  is rigidly attached to said forefoot member  80  and said sole member  50  with nut and bolt combinations  104 , and extends substantially rearward and upward, its uppermost edge  88  preferably terminating below said attachment section  40  of said forefoot member  80 .  
         [0029]    In an alternative embodiment, shown in FIG. 2, the sole member  50  extends substantially forward from said attachment section to the forwardmost tip  48  of the foot  10 , and the forefoot member  80  preferably extends slightly forward from the forwardmost tip  84  of the auxiliary support member  86 , curving slightly upwards to a distal tip  45 . In this alternative embodiment, a block  119  can be interposed between the tip  45  of the forefoot portion  80 , and the toe section  52  of the sole member  50 .  
         [0030]    Resilient blocks of wedge-shaped configuration and of various size may be included, for example in the positions indicated in the drawings as  118 ,  120 ,  121 , and  119 , FIG. 2, such that they allow for the variability of the lever arms of the structural members  80 ,  86 , and  50 . For example FIG. 1 shows a block  118  interposed between the under surface of the forward portion  84  of the auxiliary ankle  86  and the upper surface of the arch section  44  of the forefoot member  80 , which has the effect of decreasing the lever arm of the toe portion  46  of the forefoot member  80 .  
         [0031]    Referring to FIGS. 3 and 4, the attachment section  40  of the forefoot member  80  preferably incorporates two centrally-located openings  90 . The attachment section  40  is substantially rigid and capable of sustaining torsional, impact and other loads impressed thereupon by the toe portion  46  and heel portion  54  of the prosthesis. In addition, the inherent rigidity of the attachment section  40  causes the effective transmission of the aforesaid loads imposed thereupon to a suitable ancillary prosthetic pylon  30 , by bolt and nut combinations  98  assembled through openings  90  to a pylon coupling  33 . A screw  92  or other suitable attachment means secures the ancillary pylon  30  in the coupling  33 . Those skilled in the art will recognize that a variety of other attachment means may be utilized, such as glue, rivets, tape, etc.  
         [0032]    In an alternative embodiment shown in FIGS.  5 - 8 , the sole member  50  and part of the forefoot portion  80  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. A strap  74  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.  
         [0033]    A compressible member  116  may be disposed between said forefoot member  80  and said auxiliary support member  86 . The compressible member  116  is preferably fabricated such that it provides additional adjustment of the performance characteristics of the prosthesis  10  through the variation of its degree of compressibility. For example, an inflatable bladder filled with air, CO 2  or other gas could be used. In a particularly preferred embodiment of the present invention the compressible member  116  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.  
         [0034]    The compressible member  116  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 the compressible member  116 . Foam densities of between about 150 and 1500 kg/m 3  may also be used to obtain the benefits of the invention taught herein.  
         [0035]    The rear surface of the auxiliary ankle member  86  is preferably allowed to slip relative to the compressible member  116  in order to allow for increased plantar flexion. The compressible member  116  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 the auxiliary ankle member  86  and the compressible member  116  is allowed.  
         [0036]    Alternatively, the compressible member  116  may be replaced by a substantially non-compressible friction-reducing element, or eliminated altogether. The absence of the compressible member  116  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 pads  130  and/or a heel pad  126  may be disposed under the toe section  46  of the forefoot member  80  and the heel section  54  of the sole member  50  respectively, so as to provide minor shock absorption to the prosthetic  10 .  
         [0038]    In the preferred embodiment, bolt and nut combinations  104 , in conjunction with the load-distributing metallic plates  106 , serve to secure the sole member  50  in operative relationship with the forefoot member  80  of the prosthesis. This mode of affixation facilitates the assembly or dismounting of selected sole members  50  in operative relationship with selected forefoot members  80 , 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 and sole portions  80  and  50 .  
         [0039]    The auxiliary ankle member  86  provides further adjustability of the performance characteristics of the prosthetic  10  by adding to the stiffness of the forefoot member  80 . The auxiliary ankle  86  is formed from fibrous laminates of the same character as the various portions of the prosthesis  10 . In a preferred embodiment of the present invention, the auxiliary ankle  86  incorporates an attachment section  94  which is operatively associated with the ankle section  42  of the forefoot member  80  and the attachment section  58  of the sole member  50 .  
         [0040]    The auxiliary ankle  86  is preferably secured in operative relationship with the curvilinear ankle section  42  of the forefoot member  80  through the aforementioned assembly of the bolt and nut combinations  104 . On its end opposite from the attachment section  94 , ankle member  86  has an upper section  92  which is preferably fixed in operative relationship with a compressible member  116  and the curvilinear ankle section  42  of the forefoot member  80  by the use of a flexible, yet substantially non-stretching strap  70 . Said compressible member  116  providing a gradual dynamic transition throughout toe-off.  
         [0041]    The strap  70  may be fabricated from a suitably tough, flexible material such as impregnated canvas or the like, and is configured and assembled with the ankle section  42  of the forefoot member  80 , the auxiliary support member  86 , and/or the compressible member  116  to achieve desired stress-storage and -release performance in the prosthesis. For example, the strap  70  may be releasably attached around the auxiliary support member  86  through the provision of Velcro-type fasteners or similar expedient.  
         [0042]    A restraining element such as the strap  70  may be incorporated at various locations on the prosthesis  10  to restrict the distance that associated structural members  86 ,  80 , and  50  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 the auxiliary support member  86  and forefoot member  80  during heel strike will allow for increased plantar flexion. The retaining element may be utilized to prevent undesirable excessive loading and stressing of a particular member  86 ,  80 , or  50 , and/or to combine the spring-stress response characteristics of the associated structural members  12  under certain loading conditions. For example, the strap  70  as assembled in FIG. 1 permits the auxiliary member  86  to assist in raising the toe  46  of the prosthesis  10  and to store and release spring energy when the heel portion  54  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.  
         [0043]    In the preferred embodiment, the auxiliary ankle member  86  is secured against the relatively concave surface of the curvilinear ankle section  42 , so that the anticipated upward deflection of a toe section  46  of the forefoot member  80 , as more thoroughly described below, will eventually cause deformation of the auxiliary ankle  86  as well as deformation of the ankle section  42 , effectively combining the deformation resistance and energy storage characteristics of the auxiliary ankle member  86  with those of the forefoot member  80 . Alternative embodiments would include securing the auxiliary ankle  86  to the underside of the arch section  44  and continuing to use the strap  70  to maintain the functional relationship between the auxiliary ankle  86  and the forefoot member  80  in order to achieve the aforedescribed desired combination of the deformation resistance and energy storage characteristics of the auxiliary ankle member  86  with those of the ankle section  42 .  
         [0044]    The auxiliary ankle member  86  can be provided with different numbers of laminates to make it more or less compliant to loads transmitted through the forefoot member  80 . Consequently, when confronted with various anomalies in an amputee, such as overweight or excess activity levels, the basic structure of the forefoot member  80 , and more particularly the ankle section  42 , can be materially modified to provide ankle portion action which is precisely adjusted to the needs of the amputee. Moreover, a variety of auxiliary ankle members  86  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 the arch section  44  allows exchange of auxiliary ankle sections  86  to be made without necessarily removing the prosthesis  10  from the pylon  30 .  
         [0045]    A cosmetic cover (not shown) can be provided to shroud the prosthesis  10  after the optimum assemblage of the primary and sole members  80  and  50  and an auxiliary ankle member  86  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.  
         [0046]    The materials from which the forefoot member  80 , sole member  50 , and the auxiliary ankle  86  are formed preferably possess the ability to provide an energy-storing, resilient, spring-like effect. This is preferred because each engagement of the prosthesis  10  with an adjacent surface impresses compression, torsional and other loads upon the prosthesis  10  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 the prosthesis  10 .  
         [0047]    These members are preferably fabricated, for example, from polymer impregnated and encapsulated laminates. To achieve the relatively thin construction of the forefoot and sole members  80  and  50  and the auxiliary support member  86  of the prosthesis  10 , 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 and sole members  80  and  50  and the auxiliary support member  86  to complement the stress-absorbing and storing characteristics of the polymers in which said fibrous laminae are embedded.  
         [0048]    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.  
         [0049]    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 sole members  80  and  50  and the auxiliary support member  86  and, correspondingly, determine the total weight of the prosthesis  10 . As will be apparent from the discussion herein, the forefoot and sole members  80  and  50  and the auxiliary support member  86  are designed to specifically accommodate individuals having different foot sizes, different weights and different strides and the individual design of the forefoot and sole members  80  and  50  and the auxiliary support member  86  provides for matching, to an extent previously unknown in the art, the natural characteristics of the wearer&#39;s uninjured limb.  
         [0050]    Furthermore, the function blocks  118 ,  120 ,  121  and  119 , 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 the heel section  54  and the toe section  46  or  52  may be increased or decreased.  
         [0051]    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.  
         [0052]    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.