Patent Publication Number: US-2015073567-A1

Title: Composite pylon for a prosthetic device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims benefit of U.S. provisional patent application Ser. No. 61/876,272 filed Sep. 11, 2013, and entitled “Composite Pylon for a Prosthetic Device,” which is hereby incorporated herein by reference in its entirety. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     BACKGROUND 
     Embodiments disclosed herein relate generally to prosthetic limbs. More particularly, embodiments disclosed herein relate to flexible pylons for coupling prosthetic extremities to amputees. 
     Amputees typically employ the use of prosthetic limbs to replace the function of the particular limb that is missing. For patients who have had one of their legs amputated at or below the knee, the prosthesis typically includes a prosthetic foot, a socket within which the post-operative stump or residual limb is seated, and a rigid pylon extending between the socket and the prosthetic foot. 
     A useful prosthesis at least partially simulates the operation and motion of an anatomical foot. In addition, for Syme amputees (e.g., amputees who have sustained an ankle disarticulation), a useful prosthesis simulates the operation, flexion, and motion of an anatomical ankle An anatomical foot, including the ankle joint, is capable of motion around three perpendicular axes, as well as varying degrees of flexure. Specifically, the anatomical foot and ankle are capable of dorsiflexion, planiflexion, inversion, eversion, and transverse rotation. To achieve such functionality, some prosthetics include a distinct prosthetic ankle that is coupled to or incorporated into the prosthetic foot and that is capable of complicated motion (e.g., motion around two or three axes). However, inclusion of a prosthetic ankle may add bulk and additional weight to the prosthesis. 
     A useful prosthetic limb also provides a spring effect during use (e.g., be capable of absorbing, storing, and releasing energy). At a minimum, the prosthesis should store enough energy to return itself to a relaxed, unflexed position when external forces are removed. Such a spring effect may be accomplished in a conventional prosthetic foot by including various energy storing components such as coil springs. However, similar to prosthetic ankles, inclusion of such energy-storing components may significantly increase the weight of the prosthesis. 
     Although some conventional prosthetics are sufficiently strong and durable to withstand the stresses of repeated stepping motions over long periods of time, some conventional prostheses can become uncomfortable after extended periods of use due to excessive weight, bulkinesss, and inherent inflexibility of many of the components making up the prosthetic. Such discomfort may discourage use of the prosthetic and thus results in a reduced quality of life for the patient. 
     BRIEF SUMMARY OF THE DISCLOSURE 
     Embodiments disclosed herein are directed to pylons for a prosthetic device. In an embodiment, the pylon has a central axis, a first end, and a second end. In addition, the pylon includes a first connecting member disposed at the first end and configured to couple to a socket worn by an amputee. Further, the pylon includes a second connecting member disposed at the second end and configured to couple to a prosthetic foot. Still further, the pylon includes a pylon member extending axially from the first connecting member to the second connecting member, wherein the pylon member extends helically about the central axis. 
     Embodiments disclosed herein are also directed to a prosthetic device. In an embodiment, the prosthetic device includes a socket configured to receive the residuum of an amputated limb. In addition, the prosthetic device includes a prosthetic extremity. Further, the prosthetic device includes a pylon extending between the socket and the prosthetic extremity, wherein the pylon has a central axis, a first end coupled to the socket, and a second end coupled to the prosthetic extremity. The pylon includes a first connecting member disposed at the first end and coupled to the socket, and a second connecting member disposed at the second end and coupled to the prosthetic extremity. In addition, the pylon includes a pylon member extending axially from the first connecting member to the second connecting member, wherein the pylon member extends helically about the central axis. 
     Embodiments disclosed herein are also directed to a pylon adapter for a prosthetic device. In an embodiment, the pylon adapter includes a central axis, a first end, and a second end. In addition, the pylon adapter includes a first coupling extending axially from the first end, the first coupling including a first receptacle that is defined by a frustoconical surface that is oriented at an angle α relative to the central axis, wherein the first receptacle is configured to receive a connecting member of a pylon of the prosthetic device. Further, the pylon adapter includes a second coupling extending axially from the second end, the second coupling including a second receptacle. 
     Embodiments described herein comprise a combination of features and advantages intended to address various shortcomings associated with certain prior devices, systems, and methods. The foregoing has outlined rather broadly the features and technical advantages of the invention in order that the detailed description of the invention that follows may be better understood. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description, and by referring to the accompanying drawings. It should be appreciated by those skilled in the art that the conception and the specific embodiments disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which: 
         FIG. 1  is a schematic view of a conventional prosthetic for an amputee; 
         FIG. 2  is a schematic side view of an embodiment of a prosthetic including a helical pylon assembly in accordance with the principles disclosed herein; 
         FIG. 3  is a cross-sectional view of the helical pylon assembly of  FIG. 2  taken along section III-III in  FIG. 2 ; 
         FIG. 4  is a perspective side view of the helical pylon assembly of  FIG. 2  illustrating only one of the pylon members; 
         FIG. 5  is an enlarged partial schematic side view of one of the pylon members of the helical pylon assembly of  FIG. 2 ; 
         FIG. 6  is a schematic cross-sectional view of the lower pylon adapter of the helical pylon assembly of  FIG. 2 ; 
         FIG. 7  is a schematic cross-sectional view of an alternative embodiment of a lower pylon adapter; and 
         FIG. 8  is a schematic partial schematic side view of an embodiment of a pylon member that can be used in the helical pylon assembly of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following discussion is directed to various exemplary embodiments. However, one skilled in the art will understand that the examples disclosed herein have broad application, and that the discussion of any embodiment is meant only to be exemplary of that embodiment, and not intended to suggest that the scope of the disclosure, including the claims, is limited to that embodiment. 
     Certain terms are used throughout the following description and claims to refer to particular features or components. As one skilled in the art will appreciate, different persons may refer to the same feature or component by different names. This document does not intend to distinguish between components or features that differ in name but not function. The drawing figures are not necessarily to scale. Certain features and components herein may be shown exaggerated in scale or in somewhat schematic form and some details of conventional elements may not be shown in interest of clarity and conciseness. 
     In the following discussion and in the claims, the terms “including” and “comprising” are used in an open-ended fashion, and thus should be interpreted to mean “including, but not limited to . . . .” Also, the term “couple” or “couples” is intended to mean either an indirect or direct connection. Thus, if a first device couples to a second device, that connection may be through a direct connection, or through an indirect connection via other devices, components, and connections. In addition, as used herein, the terms “axial” and “axially” generally mean along or parallel to a central axis (e.g., central axis of a body or a port), while the terms “radial” and “radially” generally mean perpendicular to the central axis. For instance, an axial distance refers to a distance measured along or parallel to the central axis, and a radial distance means a distance measured perpendicular to the central axis. As used herein, the phrase “omnidirectional flexibility” refers to flexibility in any direction. As used herein, the terms “approximately”, “substantially”, and “about” mean +/−10%. 
     Referring now to  FIG. 1 , a schematic representation of a patient or user  5  utilizing a conventional prosthetic  10  is shown. In this embodiment, the leg  7  of user  5  has been amputated just below the knee such that leg  7  terminates in a stump or residuum  9 . Prosthetic  10  includes a socket  12  at its upper end, a prosthetic foot  16  at its lower end, and a pylon  14  extending generally vertically between the socket  12  and foot  16 . Socket  12  defines a receptacle that receives residuum  9 . Pylon  14  is a rigid, straight column coupled to the socket  12  at one end and the foot  16  at the opposite end. In particular, pylon  14  is coupled to socket  12  with a first or upper socket adapter  17  and is coupled to foot  16  with a second or lower socket adapter  19 . Typically, pylon  14  is a hollow tubular constructed from a rigid material such as, for example, a metal or a composite. Since pylon  14  is rigid and generally inflexible, as user  5  engages in dynamic motion (e.g., walking) with leg  7 , reaction forces from the support surface  3  (e.g., ground or floor) are directed vertically through pylon  14 , socket  12 , and into residuum  9 , thereby resulting in discomfort and a relatively limited movement potential for user  5 . However, as will be described in more detail below, embodiments disclosed herein comprise helically shaped pylons that allow for enhanced omnidirectional flexibility during dynamic motion by a user (e.g., user  5 ), while still providing a strong, stable support column for transferring the weight of the user  5  into the support surface  3  during such use. The omnidirectional flexibility of the helically shaped pylons of the embodiments disclosed herein offers the potential to cushion at least a portion of the repetitive shocks transferred from the surface  3  to the residuum  9  of the user  5 , as well as enhance overall flexibility of the prosthetic, thereby enhancing user comfort and maneuverability. 
     Referring now to  FIG. 2 , an embodiment of a prosthetic  100  in accordance with the principles disclosed herein is shown. Prosthetic  100  includes a socket  120 , a pylon assembly  130 , and a prosthetic foot  180 . Socket  120  is substantially the same as socket  12  previously described, and in general, can comprise any suitable socket known in the art for use with a prosthetic limb. In this embodiment, socket  120  includes a first or upper end  120   a,  a second or lower end  120   b  opposite the upper end  120   a,  and a receptacle  122  extending axially from the upper end  120   a.  Receptacle  122  is configured to receive the post-operative stump or residual limb (e.g., residuum  9 ) of an amputated limb (e.g., leg  7 ) of a patient (e.g., user  5 ). As is known in the art, socket  120  can include various attachment members (e.g., buckles, snaps, hook and loop connectors) to ensure a secure connection to the user. 
     Prosthetic foot  180  is similar to prosthetic foot  16  previously described, and in general, can comprise any suitable prosthetic foot known in the art, such as, for example, any of the prosthetic feet disclosed in U.S. Pat. Nos. 8,118,879 and 7,871,443, each of which is incorporated herein by reference in its entirety for all purposes. As shown in  FIG. 2 , prosthetic foot  180  comprises a first or upper side  180   a,  a second or lower side  180   b  opposite the upper side  180   a,  a first or front end  180   c,  and a second or back end  180   d  opposite the front end  180   c . An engagement surface  182  extends between the front end  180   c  and the back end  180   d  along the bottom side  180   b.  During use, at least a portion of surface  182  engages with a support surface (e.g., support surface  3 ) to provide support for a user using prosthetic  100 . In addition, foot  180  includes a connector spindle  184  proximate the upper side  180   a  (note: spindle  184  is shown in  FIG. 2  with a hidden line). Spindle  184  can comprise any suitable connector for a prosthetic foot, such as, for example, connectors manufactured by OTTO BOCH™ located in Minneapolis, Minn., or the like. 
     Referring still to  FIG. 2 , in this embodiment, pylon assembly  130  includes a pylon  140  and a pair of pylon adapters  132  coupled to opposite ends of pylon  140 . One pylon adapter  132 , also referred to herein as the “upper pylon adapter,” couples pylon  140  to socket  120 , and the other pylon adapter  132 , also referred to herein as the “lower pylon adapter,” couples pylon  140  to prosthetic foot  180 . 
     Pylon  140  has a linear central axis  145 , a first or upper end  140   a,  and a second or lower end  140   b  opposite end  140   a.  In addition, pylon  140  includes a pair of connecting members  141  and a plurality of circumferentially-spaced parallel pylon members  144 . One connecting member  141  is disposed at upper end  140   a,  the other connecting member  141  is disposed at lower end  140   b,  and each pylon member  144  extends axially between connecting members  141 . As will be described in more detail below, each pylon member  144  spirals helically around axis  145  as it extends between connecting members  141 . 
     In this embodiment, each connecting member  141  is a cylindrical member sized and shaped to mate and engage with one of the adapters  132  of prosthetic  100 . As will be described in more detail below, the member  141  disposed at upper end  140   a  is received within a mating receptacle in the upper adapter  132  and the member  141  disposed at lower end  140   a  is received within a mating receptacle in the lower adapter  132 . As best shown in  FIG. 3 , in at least some embodiments, each connecting member  141  has a uniform outer diameter D 141  that is substantially the same as the diameter of the mating receptacles provided in the upper and lower adapters  132 . Although each connecting member  141  has a cylindrical geometry in this embodiment, it should be appreciated that the specific geometry of each connecting member (e.g., each connecting member  141 ) can be varied, but is preferably sized and shaped to mate with the mating receptacles of the corresponding adapter (e.g., upper and lower adapters  132 ). 
     Each connecting member  141  is a rigid, solid structure designed to maintain the positions of pylon members  144  relative to each other while transferring loads between pylon members  144  and adapters  132 . In this embodiment, each connecting member  141  is made from a composite material, and in particular, a carbon fiber and epoxy composite. However, in general, connecting members  141  can be made of any suitable material for supporting pylon members  144  and engaging with adapters  132  including, without limitation, metals and metal alloys (e.g., aluminum, steel, etc.), non-metals (e.g., resin, polymer, etc.), composite (e.g., carbon fiber composites), or combinations thereof. 
     Referring again to  FIG. 2 , each pylon member  144  has a central or longitudinal axis  143 , a first or upper end  144   a  rigidly secured to connecting member  141  disposed at upper end  140   a,  and a second lower end  144   b  opposite the upper end  144   a  rigidly secured to connecting member  141  disposed at lower end  140   b.  In addition, each pylon member  144  has a length L 144  measured axially relative to axis  145  between the ends  144   a,    144   b.  In this embodiment, each pylon member  144  has the same axial length L 144 . In general, the axial lengths L 144  of the pylon members  144  will depend on a variety of factors including, without limitation, the height, weight, and walking style (e.g., gate) of the user (e.g., user  5 ), the location of the amputation, and the desired level of activity of the user. As best shown in  FIG. 3 , each pylon member  144  has an outer diameter D 144 . In this embodiment, each pylon member  144  has the same outer diameter D 144  that is preferably between 0.25 in. and 0.625 in, and is more preferably between 0.37 in. and 0.625 in. In addition, in some embodiments, the axial length L 144  of each pylon member  144  is at least twelve (12) times the diameter D 144 . 
     Referring again to  FIG. 2 , in this embodiment, pylon  140  includes three uniformly circumferentially-spaced pylon members  144 . However, in other embodiments, more or less than three pylon members (e.g., pylon members  144 ) can be provided. For example, in one embodiment, the pylon (e.g., pylon  140 ) includes a total of four pylon members (e.g., four pylon members  144 ). In general, the number of pylon members is inversely related to the flexibility of the pylon. Thus, as the number of pylon members increases, the flexibility of the pylon decreases, and as the number of pylon members decreases, the flexibility of the pylon increases. However, it should be appreciated that the incremental decrease in flexibility also generally decreases with each additional pylon member  144  added to pylon  140  above a total of three pylon members  144 . Thus, a determination as to the appropriate number of pylons members to include within the pylon is at least partially dictated by the desired flexibility of the pylon. It should also be appreciated that the resulting flexibility of pylon  140  is also greatly influenced by the rate of twist of the pylon members  144  (described in more detail below). 
     Referring now to  FIG. 4 , a single pylon member  144  is shown, it being understood that each pylon member  144  is the same. Pylon members  144  are uniformly circumferentially-spaced about axis  145  and oriented parallel to each other as shown in  FIG. 3 . In addition, each pylon member  144  spirals helically about axis  145  as it extends between connecting members  141 . Accordingly, pylon members  144  may be described as “helical.” In this embodiment, although pylon members  144  are helical, the central axis  143  of each pylon member  144  is disposed at the same radius relative to axis  145 . In other words, pylon members  144  of this embodiment do not incline to taper radially inward or radially outward moving towards either end  144   a,    144   b . Further, in some embodiments, the pylon members  144  are separated from the central axis  145  by a distance or radius that is equal to approximately 12.5% of the radius of each member  144  (i.e., 12.5% of one half of the diameter D 144 ), although other distances are possible. The helical geometry of each pylon member  144  can be described in terms of a helical angle β equal to the total angle, measured about axis  145 , through which each member  144  extends between its ends  144   a,    144   b.  As previously described, in this embodiment, pylon members  144  are parallel, and thus, the helical angle β for each pylon member  144  is the same. For embodiments described herein, the helical angle β for each pylon member  144  is preferably between 120° and 360° regardless of the axial length L 144  of each member  144 . In the embodiment shown in  FIG. 2 , the helical angle β of each helical pylon member  144  is 360°, and thus, each helical pylon member  144  completes one full twist or turn about axis  145  between ends  144   a,    144   b.  In general, the helical shape of each of the pylon members  144  provides omnidirectional flexibility for pylon  140  during use thereof. In other words, pylon  140  may flex such that the upper end  140   a  may flex or move in any direction relative to the lower end  140   b  and therefore foot  180 . More particularly, without being limited to this or any other theory, in some embodiments, the helical shape of each member  144  allows each member  144  to wind or un-wind in response to an applied bending moment (e.g., such as would be applied during dynamic motion by a user), which thereby decreases the amount of compression and tension experienced by each member  144  during such deformation and thus increases the overall flexibility of pylon  140  along any direction relative to the axis  145 . In addition, by maintaining a consistent helical angle β and number of pylon members  144 , the flexibility of pylon  140  may be substantially held constant regardless of the axial length L 144 . 
     Referring again to  FIG. 2 , in some embodiments the angular orientation of the ends  144   a,    144   b  of members  144  within pylon  140 , relative to the foot  180  and socket  120  is irrelevant. However, in other embodiments, such as, for example, those embodiments wherein a total of three pylon members  144  are included within pylon  140 , it is preferable to angularly place the ends  144   a,    144   b  of members  144  such that the lower end  144   b  of two of the members  144  faces (or is proximate) the front end  180   c  of foot  180  while the lower end  144   b  of one of the members  144  faces (or is proximate) the back end  180   d  of foot  180 . Without being limited to this or any other theory, the above described angular arrangement of the pylon members  144  allows for increased level of vertical support for a user (e.g., user  5 ) toward the front end  180   c  of foot  180 , which is desirable in at least some circumstances. 
     Referring now to  FIG. 3 , in this embodiment, each pylon member  144  includes several concentric annular layers. In particular, moving radially outward from the central axis  143 , each member  144  includes a central core  146 , an inner double layer of bi-directional carbon fiber  147 ′, a layer of infusion glass  148 , a layer of bi-directional carbon glass  149 , and an outer double layer of bi-directional carbon fiber  147 ″. Within each pylon member  144 , the layers  146 ,  147 ′,  148 ,  149 ,  147 ″ are adhered or bonded together with a binding agent such as, for example, a resin (e.g., epoxy resin, a spray adhesive, etc.). Thus, within each pylon member  144 , the layers  146 ,  147 ′,  148 ,  149 ,  147 ″ are joined together to form a single composite material capable of flexing as a single unit without the layers  146 ,  147 ′,  148 ,  149 ,  147 ″ delaminating or moving relative to each other. 
     In this embodiment, central core  146  is a solid rod made of urethane having a Durometer hardness of 70-90 Shore Scale A. In addition, in this embodiment, core  146  has a cylindrical geometry with an outer diameter D 146  preferably between 0.125 and 0.1875 in. 
     Referring now to  FIG. 5 , in some embodiments, each of the inner and outer layers of bi-directional carbon fiber  147 ′,  147 ″, respectively, comprises individual carbon fibers that are arranged along member  144  in an alternating fashion such that each fiber is oriented at an angle θ with respect to the central axis  145  of pylon  140 . Each angle θ is preferably between 0° and 90°, more preferably between 30° and 60°, and even more preferably 45°. In this embodiment, each layer of bi-directional carbon fiber  147 ′,  147 ″ is oriented such that each angle θ is 45°. In particular, in the embodiment shown, each of the layers  147 ′,  147 ″ comprises a first plurality fibers  147   a  interwoven with a second plurality of fibers  147   b.  Each of the first plurality of fibers  147   a  is disposed at a 45° angle to the central axis  145  of the pylon  140 . In addition, each of the second plurality of fibers  147   b  extends substantially perpendicular to each of the first plurality of fibers  147   a  such that each is also disposed at a 45° angle to the central axis  145  of the pylon  140 . Similarly, in this embodiment, the layer of bi-directional carbon glass  149  comprises a plurality of individual fibers that are arranged in an alternating fashion such that each fiber is oriented at the same angle θ with respect to the central axis  145  of pylon  140 . In other embodiments, the fibers of carbon glass within layer  149  may be oriented at a different angle θ than the fibers within the inner and outer layers of carbon fiber  147 ′,  147 ″, respectively, while still complying with the principles disclosed herein. 
     Referring again to  FIG. 3 , each layer of fusion glass  148  comprises a plurality of glass fibers oriented parallel to axis  143  of the corresponding pylon member  144 . Additionally, glass  148  includes a plurality of slots or spaces between each of the glass fibers. The above described orientation and spaces allow for the ingress or flow of the binding agent (e.g., epoxy resin) axially between ends  144   a,    144   b  of each member  144  as well as radially through the layer of fusion glass  148  during manufacturing. Further, it should be appreciated that pylon members  144  may be fabricated through any suitable method known in the art, such as, for example, resin transfer molding (“RTM”) or infusion molding, Prepreg autoclave molding, saturation molding, or some combination thereof. 
     Referring now to  FIG. 6 , each pylon adapter  132  has a central axis  135 , a first end  132   a,  a second end  132   b  opposite the end  132   a,  a first coupling  133  extending axially from the first end  132   a,  and a second coupling  134  extending axially from the second end  132   b  to coupling  133 . First coupling  133  includes a receptacle  137  extending axially from the upper end  132   a  and second coupling  134  includes a receptacle  138  extending axially from the lower end  132   b.  As shown in  FIG. 6 , member  141  of pylon  140  is received and secured within receptacle  137 , and spindle  184  is received and secured within receptacle  138  to connect foot  180  to pylon  140 . Upper pylon adapter  132  is the same as lower pylon adapter  132  except that upper pylon adapter  132  is flipped or rotated approximately 180° such that connecting member  141  at upper end  140   a  of pylon  140  is received within receptacle  137 , and a spindle  184  mounted to socket  120  is received and secured within receptacle  138  to connect socket  120  to pylon  140 . 
     In general, each connecting member  141  can be secured within the corresponding receptacle  137  through any suitable means known in the art. For example, the connecting member  141  can be secured within receptacle  137  via an interference fit, an adjustable collar secured to adapter  132 , a set screw extending radially into the receptacle  137  and engaging the radially outer surface of connecting member  141 , a bonding agent, or combinations thereof. In this embodiment, receptacle  137  is defined by a cylindrical surface, however, in general, the receptacle  137  can have any suitable shape, but preferably has a shape that corresponds with the shape of the connecting member  141  disposed therein. 
     In this embodiment, each spindle  184  is secured within the corresponding receptacle  138  with a plurality of circumferentially-spaced set screws  131 . Each set screw  131  is threadably disposed in one port  139  extending radially outward from receptacle  138  through coupling  134 . Thus, screws  131  can be advanced radially into receptacle  138  and into engagement with spindle  184  by threadably advancing them through ports  139 . In this embodiment, a total of four uniformly circumferentially-spaced ports  139  are provided. However, it should be appreciated that the number and arrangement of the ports  139  and set screws  131  may be varied while still complying with the principles disclosed herein. 
     Referring briefly to  FIGS. 3 and 6 , in some embodiments, it can be difficult to determine the appropriate size (e.g., diameter D 141 ) of the connecting member  141  in order to ensure a proper fit of member  141  within connector  132 . In particular, the final or resulting diameter D 141  of the members  141  may fluctuate during the fabrication process due to properties of the material making up members  141  (e.g., epoxy or other resins, carbon fiber, etc.). For example, in some embodiments, the final value for the diameter D 141  may be reduced as much as 0.01 in from the initial diameter during the fabrication process. Thus, embodiments disclosed herein include alternative embodiments of pylon adapter  132  that include alternative geometries that both account for this fluctuation in the final sizing of the members  141  and ensure a more secure connection during use thereof. 
     Referring now to  FIG. 7 , an alternative embodiment of pylon adapter  232  that can be used in place of either or both adapters  132  previously described is shown. Adapter  232  is substantially the same as adapter  132  previously described. In particular, lower pylon member  232  includes a first end  232   a,  a second end  232   b  opposite the first end  232   a,  a first coupling  233  extending axially from the first end  232   a,  and a second coupling  134 , as previously described, extending from the second end  232   b  to coupling  233 . First coupling  233  includes a receptacle  237  extending from first end  232   a.  Unlike receptacle  137  previously described, which is defined by a cylindrical surface, in this embodiment, receptacle  237  is defined by a frustoconical surface  238  that tapers slightly radially inward moving axially from first end  232   a.  In some embodiments, the frustoconical surface  238  of the receptacle  237  is disposed at an angle α relative to the central axis  135  that is preferably between 1-3°. In at least one particular embodiment, the frustoconical surface  238  defining the receptacle  237  is oriented such that there is approximately 1/32 inches of radial deflection (or radial run) for every 1⅛ inches of axial distance with respect to the axis  135 . When a cylindrical connecting member  141  is axially advanced into the receptacle  237 , an interference fit is formed between connecting member  141  and coupling  233 . In some embodiments, connecting member  141  may also be frustoconical in shape in order to correspond with the shape of receptacle  237  during use. In at least some of these embodiments, the radially outermost surface of the connecting member  141  is formed to correspond to the radially inner surface  238  of the receptacle (i.e., the radially outermost surface of the member  141  slopes at the same angle α). Thus, regardless of whether the member  141  is cylindrical, frustoconical, or some other shape, a reduction in the nominal diameter of the members  141  is accounted for by simply seating the member  141  axially lower within the receptacle  237  (or axially closer to the coupling  134 ). 
     In addition, in this embodiment, a bore  231  extends axially between receptacles  138 ,  237 . When connecting member  141  is seated in the receptacle  237 , an internally threaded bore  232  in the lower end of connecting member  141  is coaxially aligned with the bore  231 . Thereafter, a bolt  234  is axially advanced through bore  231  and threaded into bore  232 , thereby pulling lower connecting member  141  axially downward within receptacle  237  and thus further ensuring a secure connection between the member  141  and receptacle  237 . 
     Referring back to  FIG. 2 , during use a user (e.g., user  5 ) inserts the residuum (e.g., residuum  9 ) of an amputated leg (e.g., leg  7 ) into the socket  120  and secures it therein through any suitable method or device known in the art. Thereafter, the user may engage in some sort of dynamic motion such as, for example, walking During such activity reaction forces from a support surface (e.g., surface  3 , or the ground) are transferred through the foot  180  and into the pylon  140  of pylon assembly  130 . Because of the helical orientation of each of the pylon members  144  of pylon  140 , pylon  140  bends and deforms omnidirectionally with respect to the axis  145  to at least partially dissipate such forces, thereby effectively increasing comfort for the user. 
     In the manner described, a user (e.g., user  5 ) may use a prosthetic (e.g., prosthetic  100 ) incorporating a helical pylon assembly (e.g., assembly  130 ) that allows for enhanced omnidirectional flexibility. Such enhanced flexibility may allow for increased comfort for users of such prosthetics and may thereby increase the overall quality of life for such amputee users. 
     As previously described, in at least some embodiments, the individual carbon fibers that make up layers  147 ′,  147 ″ of bi-directional carbon fiber are oriented at the angle θ with respect to the central axis  145  of pylon  140 . However, it should be appreciated that the individual carbon fibers of layers  147 ′,  147 ″ may have different orientations while still complying with the principles disclosed herein. For example, referring now to  FIG. 8 , a schematic representation of an alternative embodiment of a pylon member  244  is shown. Pylon members  244  can be employed in pylon assembly  130  in place of pylon members  144  previously described. 
     Referring still to  FIG. 8 , pylon member  244  is the same as pylon member  144  previously described except that the inner and outer layers of bi-directional carbon fiber  147 ′,  147 ″ are oriented in a different manner. More specifically, each of the inner and outer layers of bi-directional carbon fiber  147 ′,  147 ″, respectively, comprises individual carbon fibers that are arranged along member  244  in an alternating fashion such that each fiber is oriented at an angle φ with respect to the central axis  143  of pylon member  244  rather than being oriented at the angle θ with respect to the central axis  145  of pylon  140 . Each angle φ is preferably between 0° and 90°, more preferably between 30° and 60°, and even more preferably 45°. In this embodiment, each layer of bi-directional carbon fiber  147 ′,  147 ″ is oriented such that each angle φ is 45°. Like pylon member  144 , previously described, each of the layers  147 ′,  147 ″ of pylon  244  comprises a first plurality of fibers  147   a  interwoven with a second plurality of fibers  147   b . Each of the first plurality of fibers  147   a  is disposed at a 45° angle to the central axis  143  of the pylon member  244 . In addition, each of the second plurality of fibers  147   b  extends substantially perpendicular to each of the first plurality of fibers  147   a  such that each is also disposed at a 45° angle to the central axis  143  of the pylon member  244 . Similarly, in this embodiment, the layer of bi-directional carbon glass  149  of pylon member  244  (see e.g.,  FIG. 3 ) comprises a plurality of individual fibers that are arranged in an alternating fashion such that each fiber is oriented at the same angle φ with respect to the central axis  143  along each member  144 . In other embodiments, the fibers of carbon glass within layer  149  may be oriented at a different angle φ than the fibers within the inner and outer layers of carbon fiber  147 ′,  147 ″, respectively, while still complying with the principles disclosed herein. 
     While pylon assembly  130  has been described as including both an upper and lower pylon adapter  132 , it should be appreciated that in other embodiments only one or neither of the pylon adapters  132  may be utilized while still complying with the principles disclosed herein. For example, the upper connecting member (e.g., upper connecting member  141 ) can be directly connected to a socket worn by the amputee (e.g., socket  120 ) and/or the lower connecting member (e.g., the lower connecting member  141 ) can be directly connected to a prosthetic foot (e.g., foot  180 ) through other suitable means. In addition, while the prosthetic  100  has been shown and described as a prosthesis for the lower leg, it should be appreciated that in other embodiments, prosthetic  100  may be configured to serve as any sort or type of lower limb prosthetic while still complying with the principles disclosed herein. Further, while the prosthetic  100  has been described as replacing an amputated limb, it should be appreciated that embodiments of the prosthetic  100  may also be utilized to replace limbs that were missing at birth. Still further, it should be appreciated that in some embodiments, one or both of the connecting members  141  of pylon  140  are formed in a mold that matches the shape of the matting receptacle of a corresponding pylon adapter (e.g., the receptacles  137 ,  237  of adapters  132 ,  232 , respectively) to ensure a correct and secure fit between the member  141  and the corresponding adapter  132 ,  232  during use. 
     While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems, apparatus, and processes described herein are possible and are within the scope of the invention. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims. Unless expressly stated otherwise, the steps in a method claim may be performed in any order. The recitation of identifiers such as (a), (b), (c) or (1), (2), (3) before steps in a method claim are not intended to and do not specify a particular order to the steps, but rather are used to simplify subsequent reference to such steps.