Patent Publication Number: US-9427338-B2

Title: Metatarsal joint shape for prosthetic foot and control mechanism and system for same

Description:
INCORPORATION BY REFERENCE TO ANY PRIORITY APPLICATIONS 
     Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. This application is a continuation of U.S. application Ser. No. 13/032,495 , filed Feb. 22, 2011, which claims priority under 35 U.S.C. §119(e) as a nonprovisional of U.S. Provisional App. No. 61/307,267 , filed Feb. 23, 2010. This application is also related to U.S. patent application Ser. No. 12/509,055 , filed Jul. 24, 2009, which is a continuation of U.S. patent application Ser. No. 10/987,940 , filed Nov. 12, 2004, now issued as U.S. Pat. No. 7,846,213, which is a continuation-in-part of U.S. patent application Ser. No. 10/944,436 , filed Sep. 17, 2004, now issued as U.S. Pat. No. 7,347,877, which claims priority to Provisional App. No. 60/575,142 , filed May 28, 2004. The entire contents of each of these references is hereby incorporated by reference and should be considered a part of this specification. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present application relates in certain embodiments to prosthetic feet. In particular, the present application in certain embodiments relates to prosthetic feet with an articulatable metatarsal joint. 
     2. Description of the Related Art 
     Prosthetic feet are known in the art that are designed to replicate the natural function of human feet. These prosthetic feet may include components designed to mimic the natural function of ankles, heels and toes. 
     There is much difficulty in developing a prosthetic foot that mimics the natural function of human toes. The challenges may be even greater when trying to replicate a human toe that can account for other physical modifications of the prosthetic foot. For example, a user of a prosthetic foot may be able to modify its heel height by providing ankle adjustments. When the heel height is modified without adjusting other sections of the prosthetic foot (e.g., the toe region), this results in an unnatural position of the prosthetic foot that can create discomfort for the user or provide a less than optimal rollover performance during ambulation. 
     Despite advancements in prosthetics, there remains an on-going need to provide a prosthetic foot that properly captures the function of natural human toes by providing metatarsal functionality. The prosthetic foot should be capable of assisting in walking and providing balance, weight-bearing, thrust during gait and proper push-off patterns. The prosthetic foot should also be able to accommodate different types of heel-height adjustment. 
     SUMMARY OF THE CLAIMS 
     An improved prosthetic foot designed for providing metatarsal functionality is described. In one embodiment, the prosthetic foot includes a generally plate-like foot member that extends along a longitudinal axis between an anterior end, which can correspond to a toe portion, and a posterior end, which can correspond to a heel portion. The prosthetic foot can include an elongate groove that can extend across the width of the foot member between medial and lateral edges of the foot member so that the groove intersects the longitudinal axis of the foot member. In one embodiment, the elongate groove extends generally transverse to the longitudinal axis of the foot member from the lateral edge to the medial edge of the foot member. The position of the elongate groove generally corresponds to a metatarsal region of the foot. 
     In another embodiment, a prosthetic foot is provided comprising a plate-like foot member extending along a longitudinal axis between an anterior end generally corresponding to a toe portion of a foot to a posterior end. The foot member includes a top surface and a bottom surface opposite the top surface, wherein the bottom surface is configured to contact a support surface during ambulation of the prosthetic foot. The foot member can comprise at least one elongate groove defined on the top surface, wherein the elongated groove extends between medial and lateral edges of the foot member and intersects the longitudinal axis of the foot member. The elongated groove can be positioned along the length of the foot member at a location generally corresponding to a metatarsal region of a foot and can be configured to allow the anterior portion of the foot to controllably articulate relative to the posterior end of the foot. A filler material can be disposed in the elongate groove. The filler material can be configured to vary the rate and/or degree of articulation of the anterior portion of the foot relative to the posterior end of the foot. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates an upper cross-sectional view of a human foot. 
         FIG. 2  illustrates a perspective view of a schematic of a prosthetic foot having a metatarsal hinge according to embodiments of the present application. 
         FIG. 3A  illustrates a cross-sectional view of a metatarsal hinge comprised of an unfilled groove according to embodiments of the present application. 
         FIG. 3B  illustrates a cross-sectional view of the groove in  FIG. 3A  filled with a filler material according to embodiments of the present application. 
         FIG. 4A  illustrates a cross-sectional view of a metatarsal hinge comprised of an unfilled groove having raised side supports according to embodiments of the present application. 
         FIG. 4B  illustrates a cross-sectional view of the groove of  FIG. 4A  filled with a filler material according to embodiments of the present application. 
         FIG. 5  illustrates a side view of a schematic of a prosthetic foot having a metatarsal hinge according to embodiments of the present application. 
         FIG. 6A  illustrates a top view of a prosthetic foot having a metatarsal hinge formed of a plurality of apertures according to embodiments of the present application. 
         FIG. 6B  illustrates a cross-sectional view of the prosthetic foot in  FIG. 6A . 
         FIG. 6C  illustrates an exploded view of a portion of the prosthetic foot in  FIG. 6B  having apertures filled with a filler material. 
         FIG. 6D  illustrates a cross-sectional view of an alternate embodiment of a prosthetic foot having a metatarsal hinge formed of a plurality of recessed grooves according to embodiments of the present application. 
         FIG. 6E  illustrates a top view of a contour of a foot including metatarsal point C. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Improved prosthetic feet are described that are capable of providing metatarsal functionality and mimicking the natural function of human feet. In particular, the prosthetic feet described herein include a metatarsal joint shape and control mechanism and system that can include a metatarsal hinge that provides metatarsal functionality. The prosthetic feet described herein advantageously assist in achieving the goals described above, including providing balance, improved push-off patterns and thrust during gait, even following heel-height adjustment. 
       FIG. 1  illustrates an upper cross-sectional view of a human foot. The human foot  1  serves as a mechanical structure having bones, joints, muscles, tendons and ligaments. Bones in the human foot include metatarsal bones  6  and shorter phalanges  8  that form the toes. Metatarsophalangeal joints exist between the metatarsal bones  6  and phalanges  8 . These joints assist in providing joint articulation of the phalanges  8  relative to the metatarsal bones  6 , such as at the natural metatarsal angles  14  identified in  FIG. 1 , which allows the posterior or heel of the foot to be angled relative to the forefoot or toes of the foot. Said articulation allows the use of shoes of varying heel heights while providing support and balance. 
     In view of the challenges described above, the present application discloses an improved prosthetic foot having a metatarsal joint shape and control mechanism or system that advantageously mimics the metatarsal joints of a natural human foot, thereby providing metatarsal functionality and easily accommodating heel-height adjustment of the prosthetic foot. The metatarsal joint shape and control system can include one or more elongate gaps, channels, apertures, or grooves formed in the prosthetic foot (e.g., formed on a surface of a prosthetic foot plate). The position of the grooves generally corresponds to a metatarsal region of the foot. In some embodiments, the metatarsal region of the foot comprises approximately ¼ to ⅓ or more of the foot length from an anterior edge of the foot. In other embodiments, to find the metatarsal region, the length of the foot can be multiplied by 0.618, and this distance can be travelled from a posterior edge. The grooves can be open or filled with a resilient material, and can be used to provide the prosthetic foot with metatarsal functionality, allowing the prosthetic foot to articulate via the metatarsal joint. 
       FIG. 2  illustrates a schematic of a prosthetic foot having a metatarsal hinge according to some embodiments of the present application. The prosthetic foot  100  can comprise a curved plate-like foot member  102  having a top surface  115  and bottom surface  118 , as well as an upper portion  109  and a toe region  112 . In one embodiment, at least a portion of the foot member  102  is generally planar. In one embodiment, a transverse cross-section of the foot member  102  can be generally rectangular. The foot member  102  can further include attachment holes  117  and a split  134  along its longitudinal axis that separates the plate-like member into two sections: a medial blade having medial edge  138  and a lateral blade having lateral edge  139 . In other embodiments, the foot member  102  can have more than one longitudinal split or slot  134  defining two or more blades. In still another embodiment, the foot member  102  can be a single foot plate without a longitudinal split or slot. The foot member  102  can have a metatarsal hinge generally at the location of the metatarsal region in a natural human foot. In one embodiment, the metatarsal hinge can include a channel or groove  148  that intersects the longitudinal axis of the prosthetic foot. In one embodiment, the metatarsal hinge intersects the split or slot  134  of the foot member  102 . 
     The foot member  102  of the prosthetic foot  100  can be a curved plate-like member having a posterior edge formed by the upper portion  109  and an anterior edge formed by the toe region  112 . In shape, the plate-like foot member  102  includes a vertical upper portion  109  that slopes and curves downwardly before flattening out near the toe portion  112 . At the toe portion  112 , the foot member  102  slopes and curves upwardly and provides a slight raise from the ground at the anterior end. While the foot member  102  is shown on its own in  FIG. 2 , in some embodiments, the foot member can be operably connected to a heel member, as shown in  FIGS. 5 and 6B . 
     In some embodiments, portions of the prosthetic foot (such as the foot member or heel member) can be constructed of a strong, resilient material that is capable of flexing in multiple directions, particularly during heel-strike through toe-off. The material can comprise multiple layers, or laminate. In some embodiments, the multiple layers or laminates when assembled form a monolithic foot member  102  of the prosthetic foot  100 . Examples of possible materials for the prosthetic foot  100  include carbon, any polymer material, and any composite of polymer and fiber. The polymer can be thermoset or thermoplastic. In a composite, the fiber reinforcement can be any type of fiber or filament, such as carbon, glass or aramid. The fibers can be long and unidirectional, or they can be chopped and randomly oriented. Other filaments, such as Kevlar and nylon, can also be used to ensure lightweight and structurally dynamic characteristics. 
     The upper portion  109  of the foot member  102  can be attached to adapters and/or pylons for prosthetic limbs. While not shown in  FIG. 2 , attachment holes can be provided on the upper portion  109  to assist in attaching these additional components. Other than or in addition to the attachment holes that can be provided on the upper portion  109  of the prosthesis, attachment holes  117  can also be provided on other sections of the prosthetic foot, such as below the upper portion  109  closer to the anterior end of the foot. These attachment holes  117  can be used to affix the plate-like member to other members (e.g., a lower, plate-like heel member) by using mechanical screws, fasteners or bolts. An example of a prosthetic foot having an upper member attached to a lower member by use of attachment holes is shown in  FIG. 5  and discussed further below. However, other suitable mechanisms can be used to attach the plate-like member to other members (e.g., adapter, heel plate, etc.). For example various adhesives may also be used to affix the plate-like member to other members. 
     The split  134  is located along the longitudinal axis of the foot member  102  and can help provide desirable roll-over properties. The split  134  is of a length that is between approximately ⅕ and ⅘ of the longitudinal length of the foot member  102 , can begin at a distance that is between approximately ⅕ and ⅘ of the distance away from the posterior end of the foot member, and can extend to the distal edge of the foot member (i.e., to the edge of the toe region of the foot member). The split  134  separates portions of the foot member  102  into a medial blade having medial edge  138  and a lateral blade having lateral edge  139 . While in  FIG. 2 , the medial blade and the lateral blade have equivalent widths, in other embodiments, the split  134  can form blades of unequal width. In addition, while the split  134  is entirely straight along a longitudinal axis of the foot member  102 , in other embodiments, the split  134  has a straight portion followed by a curved portion that curves either in a lateral or medial direction toward the distal end of the foot member. In yet another embodiment, the split  134  can have a curved shape without any straight portions. 
     As shown in  FIG. 2 , the foot member  102  of the prosthetic foot  100  includes a metatarsal hinge comprising a gap, channel or groove  148  that can extend across the width of the foot member between medial and lateral edges of the foot member. In the illustrated embodiment, the groove  148  is formed as a recessed portion in the top surface  115  of the foot member  102 . However, while the groove  148  is illustrated on a top surface  115  of the foot member  102 , in other embodiments, the groove can be located on a bottom surface  118  of the foot member  102 , or in between a top surface and bottom surface. In some embodiments, the groove  148  extends completely across the prosthetic foot, from one part of the medial edge to one part of the lateral edge, while in other embodiments the groove  148  extends across only a portion of the prosthetic foot. The groove  148  can intersect the longitudinal axis of the foot member  102 . In some embodiments, the groove  148  can be generally transverse to the longitudinal axis of the foot member  102 , and even perpendicular to the longitudinal axis, as shown in  FIG. 2 . In other embodiments, the groove  148  intersects the longitudinal axis of the foot member  102  at an angle other than 90 degrees, such as between 20 and 80 degrees. The prosthetic foot  100  comprising the groove  148  can be formed by special layup sequencing, where the groove  148  is defined by one or more layers, but fewer than all layers, that make up the foot member  102  of the prosthetic foot  100 , or by cutting the groove through material layers of the foot member  102  of the prosthetic foot  100  after said layers have been laid. 
     Such techniques can be used to position the elongate groove  148  generally near or around the metatarsal region of the foot. In some embodiments, the metatarsal region or “toe section” of the foot can extend a length (either planar or curvilinear depending on the shape of the region) between about 0.5 cm and 20 cm, as measured from an anterior end (e.g., anterior edge) of the foot to the groove  148 . One skilled in the art will appreciate that the length of the toe section is not limited to these lengths, and that the length can be determined in proportion to the length of the prosthetic foot. Providing a suitable length of the metatarsal region advantageously provides an effective toe length that helps to accommodate various stride lengths. With the groove  148  positioned generally near or around the metatarsal region, the prosthetic foot  100  is capable of flexing and comfortably accommodating heel height adjustments. 
     In one embodiment, the groove  148  can include sidewalls  216  that help to form the particular shape of the groove within the foot member  102 . In some embodiments, the groove  148  includes sidewalls  216  that are straight, curved, or tapered. In some embodiments, the sidewalls  216  include “teeth” formed by elevations and depressions that can further help to enclose deposited filler material. From a cross-sectional view, the groove can be curved (e.g., generally circular), u-shaped, v-shaped, square-shaped, or any other suitable shape. For example, as illustrated in  FIGS. 3A-4B , which show cross-sectional views of groove  148 , the groove  148  can be shaped like a valley, having its narrowest point in its center or bottom most point. 
     The groove  148  can further take on various dimensions. In some embodiments, the depth D of the groove can be between 1/20 and 9/10 of the cross-sectional thickness of a section of the foot member or alternatively, the average height of the foot member itself. In other embodiments, the average width W of the groove (e.g., the distance from one sidewall of the groove to another sidewall) can be between 5 mm and 20 mm, more preferably between 5 mm and 10 mm. In one embodiment, the depth of the groove  148  can vary along the length L of the groove (illustrated in  FIG. 2 ). For example, the depth D of the groove  148  can increase toward the medial edge of the foot member. The medial side of the foot member would thus be more flexible than the lateral side of the foot member, and thus, the groove helps to direct rollover of the foot member in the medial direction. Alternatively, the depth of the groove  148  can increase toward the lateral edge of the foot member. The lateral side of the foot member would thus be more flexible than the lateral side of the foot member, and thus, the groove helps to direct rollover of the foot member in the lateral direction. In addition, in some embodiments, the width W of the groove  148  can vary along the length L (e.g., it can increase in either a medial or lateral direction) of the groove to assist in directing rollover toward a medial or lateral edge of the foot member. One skilled in the art will appreciate, however, that the dimensions of the groove are not so limited, and that other dimensions are also possible, as the measurements of the groove can be determined in proportion to the type and/or thickness of a corresponding prosthetic foot. Advantageously, the groove  148  can help accommodate heel-height adjustment, such as would occur if the user wore a high-heel shoe  18  as shown in  FIG. 2 . 
     While the metatarsal hinge in  FIG. 2  is illustrated as a single straight groove  148  that intersects the longitudinal axis of the foot member  102  in a generally transverse manner, in other embodiments, the metatarsal hinge can be formed of more than one groove. The one or more grooves can intersect the longitudinal axis of the foot member  102  of the prosthetic foot  100  at various angles, including along the natural metatarsal angles  14  of the human foot, as shown in  FIG. 1 . In some embodiments, the one or more grooves can include one or more portions that are transverse to the longitudinal axis, as well as one or more other portions that are slanted or placed at an angle from the portions that are transverse from the longitudinal axis. In some embodiments, relative to a segment of the foot member that is perpendicular to the longitudinal axis, the one or more grooves can have one or more portions that are at a slanted angle between about 0 and 85 degrees, more preferably between 0 and 45 degrees, to provide for metatarsal functionality. In one embodiment, the one or more grooves can have one or more portions that are at a slanted angle between about 0 and 20 degrees relative to a line perpendicular to the longitudinal axis (e.g., slanted at an angle of 90 to 110 degrees relative to the longitudinal axis). 
     While the groove  148  shown in  FIG. 2  is formed on a top surface  115  of the curved plate-like foot member  102  of the prosthetic foot  100  (e.g., where the top surface  115  is a surface opposite the bottom surface  118  that can operatively contact a support surface, such as a floor, during ambulation), in some embodiments, the groove  148  can be formed on a bottom-surface  118  near the toe section. In other embodiments, an opening can be formed mid-way between a top-surface  115  and bottom-surface  118  near the toe section, such that the opening is only exposed on the side of the prosthetic foot. In still another embodiment, one or more grooves  148  can be formed on both the top and bottom surfaces of the foot member  102  of the prosthetic foot  100 . Regardless of whether the opening or groove  148  is formed on a top surface, a bottom surface, or mid-way between a top surface and bottom surface of the curved plate-like foot member  102  of the prosthetic foot  100 , the groove  148  can serve as an articulatable metatarsal joint that can remain open or be filled with a filler material, as discussed below. Furthermore, regardless of where the groove  148  is formed, the curved plate-like foot member  102  of the prosthetic foot  100  can still comprise a single piece whose body extends from a proximal edge to a distal edge. 
     While in some embodiments, the groove  148  can be left open (as shown in  FIG. 2 ), in other embodiments, the groove  148  can be filled with a filler material  154 . In some embodiments, the filler material can comprise a liquid, gel or solid (e.g., a solid insert insertable in the groove  148 ). In some embodiments, the filler material can comprise one or more polymers alone or in combination, such as polyurethane or silicone, as well as various other thermoplastic and thermosetting materials. Preferably, the filler material comprises a viscoelastic material comprising one or more types of synthetic polymers or elastomers, such as a gummy-material. Suitable elastomers can include, but are not limited to, materials under the trade names of Silly Putty, Sorbothane, Implus or Noene. In some embodiments, one or more grooves  148  can be filled with a combination of various materials as described above. In some embodiments, the filler material can be introduced into the groove  148  in liquid form prior to hardening upon placement in the groove  148 . The various materials that can be inserted into the groove  148  can be resilient, and in some embodiments, can have a stiffness that differs from the other material of the prosthetic foot  100 . 
     By adding the filler material  154  to the groove  148 , a number of advantages can be achieved, including providing an adjustable stiffness or spring constant at or near the metatarsal region of the foot member, as well as enhanced resistance to deflection. For example, in one embodiment in which a high-heel adjustment is made, it may be desirable to provide no filler material, or a filler material  154  that provides great flexibility. If a filler material  154  is provided, upon removal of the high-heel adjustment, the material is resilient such that is can return to an original, unstressed state. In addition, in embodiments in which the foot member is formed of multiple layers, the filler material can help prevent layers from loosening and separating, thereby helping to keep the layers in place. 
     Forming a groove  148  near the toe section of the foot member  102  of the prosthetic foot  100  (with or without filler material) provides the prosthetic foot with an articulatable metatarsal hinge that is capable of flexing and adjusting at the natural metatarsal angles of the foot. By providing the metatarsal hinge, the prosthetic foot  100  is capable of comfortably articulating and flexing in various positions before, during and after heel-height adjustment. In some embodiments, adding an elastic filler material in the groove  148  advantageously helps to further control the extent of articulation by the metatarsal hinge. The elastic filler material, which can vary in stiffness depending on the material used, can help to provide a controlled return of the prosthetic foot to its normal position following heel height adjustment. 
     In some embodiments, a housing member (not shown) is provided that can enclose the deposited filler material. The housing member can include sidewalls that enhance the function of the filler material. For example, in some embodiments, the housing provides a constant volume for the filler material. In addition, the sidewalls of the housing can provide constraints for the movement of the filler material (e.g., floating liquid material) that can be contained in the housing. In some embodiments, the housing member can be formed with the groove  148  (e.g., as a lining member) that receives the filler material. In another embodiment, the housing can have generally the same cross-sectional shape as the groove  148 . An optional cap or lining layer can be provided over the filler material to enclose the filler material once it is deposited in the prosthetic foot. In other embodiments, the housing member can accompany and surround the filler material (e.g., as a membrane) such that both can be inserted into and packed into the groove  148  simultaneously. Alternatively, or in addition to the housing member, the metatarsal hinge can include raised side supports  218 , as shown in  FIGS. 4A and 4B . 
     In some embodiments, the filler material  154  can be removable and replaceable after being deposited in the groove  148 . For example, in some embodiments, the filler material  154  can be kept in one or more membranes as a package or insert that can be readily inserted and subsequently removed from the groove  148 . By providing packages or inserts of filler material that are removable and/or replaceable, this advantageously allows the prosthetic foot to be used with an even greater array of heel-height adjustments. 
       FIG. 3A  illustrates a cross-sectional view of a metatarsal hinge comprised of an unfilled groove according to embodiments of the present application. The unfilled groove  148  has curved sidewalls  216  that form a valley. As shown in  FIG. 3A , the curved sidewalls  216  of the groove  148  are positioned below the top surface  115  of the foot member. The unfilled groove  148  can be formed near a toe section of a prosthetic foot and can help provide articulatable metatarsal function. 
       FIG. 3B  illustrates a cross-sectional view of the groove of  FIG. 3A  filled with a filler material. The filler material  154  can be selected from any of the filler material described above, and preferably comprises a viscoelastic liquid. As shown in  FIG. 3B , the filler material can occupy the entire volume of the groove  148 . However, in other embodiments, the filler material need only occupy a portion of the volume of the groove  148  (e.g., a quarter of the volume or half of the volume). In some embodiments, the filler material  154  advantageously helps to provide greater control over the flexing and articulation of the metatarsal joint mechanism. 
       FIG. 4A  illustrates a schematic of a metatarsal hinge in the form of a groove  148  having raised side supports  218  according to some embodiments of the present application. In contrast to the sidewalls  216  that are positioned below the top surface  115  of the plate-like foot member, the raised side supports  218  extend from and above the top surface  115  of the plate-like foot member. While the raised side supports  218  can be triangularly-shaped wings, as shown in  FIG. 4A , in other embodiments, the raised side supports  218  can take on other shapes and forms (e.g., they can be square or rectangular). In some embodiments, the raised side supports  218  comprise raised flanges that extend from the top surface of the grooves. In some embodiments, the raised side supports  218  extend at a height of between about 1 mm and 50 mm above the upper surface of the plate-like member. The raised side supports  218  advantageously provide an increased volume for receiving filler material in the groove  148 , thereby allowing for even greater metatarsal functionality. In some embodiments, the raised side supports  218  extend along an entire length L of the groove (shown in  FIG. 2 ), while in other embodiments, the raised side supports  218  extend only along a portion of the entire length L of the groove. For example, the raised side supports  218  can be positioned along a portion of the groove that is less than the width of the foot. In some embodiments, the raised side supports  218  can be formed continuously along at least a portion of the length of the groove, while in other embodiments, the raised side supports  218  can be staggered along at least a portion of the length of the groove. 
     In some embodiments, the raised side supports  218  are formed with the plate-like foot member  102  of the prosthetic foot  100  (e.g., by a metal injection molding). In other embodiments, the raised side supports  218  are formed separately from the foot member  102  of the prosthetic foot  100  and subsequently attached (e.g., by an adhesive or by a screw). One skilled in the art will appreciate that the housing and raised side supports  218  are optional, and it is possible to provide a filler material that is flush against the sidewalls of the groove  148 . 
     Preferably the raised side supports are composed of a resilient and compressible material capable of some flexing which does not interfere with the user when wearing various shoes (e.g., high heels). In some embodiments, the raised side supports are composed of various polymers, such as EVA or polyurethane. Various elastomers such as those described with respect to the filler material can also be used. In some embodiments, the raised side supports are composed of low compressible or non-compressible materials, including polymers of epoxides, polyamides, polycarbonates, polyimides, polyetherimides, and silicone polymers. 
       FIG. 4B  illustrates a cross-sectional view of the groove of  FIG. 4A  filled with a filler material according to embodiments of the present application. With the addition of the raised side supports  218 , filler material  154  can optionally be deposited in the groove  148  to a height above the top surface of the groove  148  (e.g., above the top surface  115  of the foot member), as shown in  FIG. 4B . In some embodiments, the additional filler material  154  deposited in the groove  148  above the top surfaces of the grooves  148  provides additional resilience and control over the flexibility and articulation of the metatarsal hinge. 
     The metatarsal hinge described above can be used with a variety of other prosthetic feet in addition to those described above.  FIG. 5  shows one such example of an alternative prosthetic foot  200  for which the metatarsal hinge can be used with. The prosthetic foot  200  includes an upper element  212  having a forefoot portion  217  and a posterior portion  219 , a lower element  214 , an adapter element  208  and groove  148  formed in a top surface  118  of the upper element  212 . In some embodiments, the upper element  212  comprises a foot plate, while the lower element  214  comprises a heel plate that is operably attached to the foot plate. 
     The upper element  212  includes the forefoot portion  217 , the posterior portion  219 , and a curved portion therebetween. In another embodiment, the upper element  212  can be generally planar. In some embodiments, a cross-sectional area of the upper element  212  can be generally rectangular. The forefoot portion  217  comprises a metatarsal region or toe section. In one embodiment, at least a portion of the forefoot portion  217  can be generally horizontal and extend from an anterior end  202 , or forward edge, of the prosthetic foot  200  toward a posterior end  204 , or rearward edge, of prosthetic foot  200 . The forefoot portion  217  can curve upward via a curvilinear portion and transition to the posterior portion  219  of the upper element  212 . A top surface  115  of the posterior portion  219  of the upper element  212  can be operably connected to an adapter element  208  (e.g., via fasteners). 
     An unfilled groove  148  is located within or proximate to a forefoot portion  217  of the upper element  212  of the prosthetic foot  200 . The unfilled groove  148  serves as an articulatable metatarsal hinge. While not shown, in another embodiment, a filler material can be provided in the groove  148  of the upper element  212  of the prosthetic foot  200 , as discussed above. 
     As shown in  FIG. 5 , a bottom surface  118  of the upper element  212  can be disposed above the lower element  214 . In one embodiment, at least a portion of the lower element  214  can be disposed adjacent and in contact with at least a portion of the bottom surface  118  of the upper element  212 . In one embodiment, the upper element  212  can be operably coupled (e.g., via fasteners  220 ) to the lower element  214 . The lower element  214  can serve as a heel member. In another embodiment, instead of the upper element  212  and lower element  214  being two separate pieces attached to one another, the upper element  212  and the lower element  214  can be one piece. The prosthetic foot  200  can interact with the ambulation, or walking, surface, via contact with lower element  214  which serves as a heel member. In still another embodiment (not shown), the upper and lower elements can be generally parallel along at least a portion of their lengths and separated at least in part by a compressible material. In one embodiment, the lower element can be disposed below and spaced apart from the upper element along its entire length. 
       FIG. 6A  illustrates a top view of a prosthetic foot having a metatarsal hinge formed of a plurality of apertures according to embodiments of the present application.  FIG. 6B  illustrates a cross-sectional view of the prosthetic foot in  FIG. 6A  with the plurality of apertures unfilled with a filler material, while  FIG. 6C  illustrates an exploded view of a portion of the prosthetic foot in  FIG. 6B  having apertures filled with a filler material.  FIG. 6D  illustrates a cross-sectional view of an alternate embodiment of a prosthetic foot having a metatarsal hinge formed of a plurality of recessed grooves according to embodiments of the present application. 
       FIG. 6A  illustrates a top view of a prosthetic foot having a metatarsal hinge formed of a plurality of elongate apertures that extend completely through the prosthetic foot. The prosthetic foot  300  can comprise a curved plate-like foot member  102  having a top surface  115 , a bottom surface  118 , a medial edge  138 , a lateral edge  139  and a toe region  112 . As shown in  FIG. 6B , the curved plate-like foot member  102  can be operably attached to a heel member  105 , such that at least a portion of the bottom surface  118  of the foot member  102  is in contact with a top surface of the heel member  105 . A plurality of apertures  348  can extend through the top surface  115  of the foot member  102 . In the illustrated embodiment in  FIG. 6A , the plurality of apertures  348  extend completely through the foot member  102  of the prosthetic foot  300 , from a top surface  115  to a bottom surface  118  (identified in  FIG. 6B ). However, in other embodiments, the apertures or grooves can extend only partly through the foot member  102  of the prosthetic foot  300 , such that the plurality of apertures resemble recessed channels or grooves, as shown in  FIG. 6D . As shown in  FIG. 6A , the apertures  348  can have sides represented by a width W′ and a length L′. At least some of sides of the apertures  348  can be in parallel with one another. Providing apertures  348  advantageously help the prosthetic foot to be more flexible, and allows the foot to mimic more accurately the biomechanical function of the anatomical foot. 
     In some embodiments, the plurality of elongate apertures  348  can be formed generally along a line that intersects a longitudinal axis of the foot. In some embodiments, the plurality of elongate apertures  348  can be formed generally along a line that is perpendicular to a longitudinal axis of the foot, while in other embodiments, the elongate apertures  348  can be formed generally along a line that while not perpendicular, is askew, to a longitudinal axis of the foot. For example, as shown in  FIG. 6E , the plurality of elongate apertures  348  can be formed along the line  312  from point D across metatarsal point C to point E, which is at an angle of approximately 110° relative to the longitudinal axis defined by points A and B. 
     As shown in  FIG. 6A , the plurality of apertures  348  can be formed across a width of the prosthetic foot. In some embodiments, the plurality of apertures  348  can each be of similar dimensions (e.g., same width W′ and length L′), while in other embodiments, some apertures may be of a different dimension than others (e.g., have a different width W′ and/or length L′). For example, as shown in  FIG. 6A , apertures  348   a  and  348   c  have a smaller length L′ than apertures  348   b  and  348   d . In addition, while the apertures  348  are illustrated as rectangular in shape, apertures of other shapes, such as circular, oval, square or triangular, can also be formed. For example, the prosthetic foot can comprise a metatarsal hinge formed of a series of circular apertures formed through the prosthetic foot to provide metatarsal functionality. In addition, a combination of apertures of various shapes and sizes can also be provided. In some embodiments, the apertures can be formed by performing a watercut on the carbon layers (e.g., using a water jet cutter), either before molding or after a layer-up process. 
     In other embodiments, rather than providing a plurality of apertures  348  that extend completely through the foot member  102  from a top surface  115  to a bottom surface  118  visible in  FIG. 6B , the prosthetic foot  300  can comprise a plurality of recessed grooves or channels  348 ′ that do not extend completely through the foot member  102  (as illustrated in  FIG. 6D ). The recessed grooves  348 ′ can be formed either on a top surface  115  of a prosthetic foot, a bottom surface  118  of a prosthetic foot, or in between a top surface and bottom surface. In one embodiment, the recessed grooves  348 ′ can assume the same shape (e.g., rectangular) and pattern across a width of the foot as the apertures  348  shown in  FIG. 6A . The difference is that the recessed grooves  348 ′ only extend through a portion of the height of the foot from the top surface  115  to a bottom surface  118  of the foot. In some embodiments, the recessed grooves  348 ′ have a depth D′ that is between about 1/10 to ¾ of the height of the foot from a top surface to a bottom surface of the foot member  102 . The depth of the recessed grooves  348 ′ can be between about 0.05 mm and 6 mm, or between about 2 mm and 4 mm. In some embodiments, the foot member of the prosthetic foot  300  can include a combination of both apertures  348  that extend completely from a top surface  115  to a bottom surface  118  of the foot and recessed grooves  348 ′ that extend only partially from the top surface  115  or bottom surface  118  of the foot. 
     In some embodiments, the plurality of recessed grooves can be formed by removing layers of material from sections of the prosthetic foot. For example, in some embodiments in which the foot member of the prosthetic foot is formed of multiple layers of carbon (e.g., about 40 layers), it is possible to remove a number of the layers (e.g., between 5 and 30 layers) to form recessed grooves in the foot member. Alternatively, the foot member of the prosthetic foot can be formed by performing a special layup sequencing, in which the recessed grooves are defined by one or more layers, but fewer than all layers, that make up the prosthetic foot  300 . 
     In some embodiments, the apertures  348  or recessed grooves  348 ′ can be filled with one or more filler materials. For example, as shown in the exploded view in  FIG. 6C , the apertures  348  can be filled with a filler material  154 . The filler material  154  can comprise any of the materials described above, including various liquids, gels or solids, or combinations thereof. In some embodiments, the filler material  154  comprises a gummy material or polyurethane. One or more filler materials (e.g., two, three or more) can be used to occupy at least a portion (if not all) of one or more apertures  348  or recessed grooves  348 ′. By providing a filler material  154 , this advantageously helps to further control the extent of articulation by the metatarsal hinge formed by the plurality of apertures  348  and/or recessed grooves  348 ′. In addition, using the filler material  154  can help provide better rollover properties for the foot. And in embodiments in which the prosthetic foot is formed of layers of carbon fiber, which are subject to loosening or springing, the filler material  154  helps to hold the layers together and in place. 
     The filler material  154  can be provided in a housing member as discussed above that enhances the function of the filler material. In addition, the filler material  154  can be packaged or inserted in a membrane, such that in some embodiments, the filler material can be insertable and/or removable from the apertures  348  or recessed grooves  348 ′. In some embodiments, only a portion of the apertures  348  or recessed grooves  348 ′ are filled with a filler material, while in other embodiments, all of the apertures  348  or recessed grooves  348 ′ are filled with a filler material. 
     In addition to the prosthetic feet  100 ,  200  and  300  described above, the inventive articulatable metatarsal joint formed of a channel or groove, as described herein, can be used with various other feet having different or additional features as described above. For example, the metatarsal hinge can be used with the prosthetic feet described in U.S. patent application Ser. No. 07/029,947, filed on Mar. 26, 1987, now issued as U.S. Pat. No. 4,822,363 , U.S. patent application Ser. No. 07/293,824, filed on Jan. 5, 1989, now issued as U.S. Pat. No. 5,037,444 , U.S. patent application Ser. No. 07/337,374, filed on Apr. 13, 1989, now issued as U.S. Pat. No. 5,181,932 U.S. patent application Ser. No. 10/642,125, filed on Aug. 15, 2003 , and U.S. patent application Ser. No. 10/674,736, filed on Sep. 30, 2009 , all of which are incorporated by reference in their entireties. 
     Of course, the foregoing description is that of certain features, aspects and advantages of the present invention, to which various changes and modifications can be made without departing from the spirit and scope of the present invention. Moreover, the prosthetic foot need not feature all of the objects, advantages, features and aspects discussed above. Thus, for example, those skill in the art will recognize that the invention can be embodied or carried out in a manner that achieves or optimizes one advantage or a group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. In addition, while a number of variations of the invention have been shown and described in detail, other modifications and methods of use, which are within the scope of this invention, will be readily apparent to those of skill in the art based upon this disclosure. It is contemplated that various combinations or subcombinations of these specific features and aspects of embodiments may be made and still fall within the scope of the invention. Accordingly, it should be understood that various features and aspects of the disclosed embodiments can be combined with or substituted for one another in order to form varying modes of the discussed prosthetic foot. Thus, it is intended that the present invention cover the modifications and variations of this invention provided that they come within the scope of the appended claims or their equivalents.