Patent Description:
Prosthetic feet serve as distal termination for a prosthetic device and can be fixed to a below knee tube, which is fastened to a prosthetic knee joint, directly to a prosthetic shank or to the prosthetic knee joint. To this end, connection features are regularly provided at the proximal end on the prosthetic foot in order to establish a stable and permanent connection with the proximal prosthetic component. Prosthetic feet are usually provided with a cosmetic covering, which consist of plastic and are embodied approximately in the form of a natural foot.

From the structural point of view, the simplest form of a prosthetic foot is a rigid foot. However, a rigid foot has significant disadvantages in view of the elastic properties or the rollover properties. More complex designs include dampening elements or heel springs for damping the momentum upon heel strike. It is likewise possible for a spring to be arranged in the forefoot region in order to enhance the rollover characteristics of the foot during the stance phase and to store and then release deformation energy so as to assist the prosthetic foot user when walking.

Opportunities exist for improvements in prosthetic feet designs to improve energy feedback, dampening, and other properties that increase performance and user comfort and stability.

<CIT> discloses a prosthetic foot, comprising a base spring, a top spring assembly, a connector and a heel cushion. The base spring has a toe end portion and a heel end portion. The top spring assembly comprises a first spring member having a distal end and a proximal end; a second spring member having a distal end and a proximal end; a first connection provided between the distal ends of the first and second spring members, and a second connection provided between the distal end of the second spring member and a top surface of the base spring; and a slot extending rearward from the distal ends of the first and second spring members along at least half of a length of the first portion of the top spring assembly. The connector is connected to the proximal ends of the first and second spring members and configured to connect the prosthetic foot to a lower limb prosthetic. The heel cushion is mounted to the base spring at a location spaced forward of a heel end of the base spring, the heel cushion arranged to contact a bottom surface of the second spring member during use of the prosthetic foot.

<CIT> relates to a prosthetic foot including a foot member and a heel member. A distal end of the heel member is coupled to the foot member. The foot member comprises a tongue portion defined by a slot in the foot element. The prosthetic foot further comprises a mechanism configured to operatively connect or disconnect the tongue protion from the remainder of the foot member. When the tongue portion is connected to the remainder of the foot member, the foot member exhibits greater stiffness.

<CIT> discloses a prosthetic foot including a forefoot member, a heel member and a forefoot reinforcement member. The forefoot reinforcement member has a base section coupled to the top side of the forefoot member. The forefoot reinforcement member distally extends above the forefoot member to a free section. The free section is moveable with respect to the forefoot member and operates within the range of motion of the forefoot member. The prosthetic foot also comprises a flexible strap coupled to the proximal ends of the forefoot member and the forefoot reinforcement member. The flexible strap transfers some of the heel load to the forefoot reinforcement member.

<CIT> is related to a low profile prosthetic with a foot member extending at an incline from an anterior portion to a posterior portion thereof and configured to flex during motion. An adapter is mounted solely at a posterior section thereof to the posterior portion of the foot member so that the adapter's anterior section can move relative to the foot member and "roll-up" onto the foot member during motion.

<CIT> is related to a prosthetic foot with a forefoot spring, a heel spring and a base spring. The base spring is connected to the heel spring and to the forefoot spring. The base spring has receiving means for the forefoot spring and the heel spring, into which receiving means the heel spring and the forefoot spring can be inserted. The heel spring is connected to the forefoot Spring via a coupling element, and the coupling element extends forwards along the forefoot spring at least via one portion thereof.

<CIT> is related to a prosthetic foot and a foot cover for providing a more natural appearance and improved performance. A foot element for a prosthetic foot can extend from a heel end to a toe end and include a heel, arch, forefoot, and toe regions. The forefoot region can be wider than the arch and heel regions. The toe region can include a U-shaped cut out to define a big toe.

<CIT> is related to a resilient forefoot member having a base end coupled proximal an attachment location and extending forward to a toe end at a toe location. The forefoot member defining an arch section between the base end and the toe end, and having a range of motion with multiple stages of advancement including at least a normal range and an extreme range and having a resistance response to an applied force. The forefoot member has a forefoot reinforcement member having a base section coupled to the forefoot member at the arch section and extending to a free end at a location between the arch section and the attachment section and spaced from the forefoot member. The free end being disposed within the extreme range of motion of the forefoot member and having a range of motion within the extreme range of motion of the forefoot member, such that the forefoot reinforcement member influences the range of motion and resistance response of the forefoot member.

One aspect of the present disclosure relates to a prosthetic foot having a base spring, a top spring assembly, a connector assembly, and a heel cushion. The base spring has a toe end portion and a heel end portion. The top spring assembly includes first and second spring members, first and second connections, first and second portions, and a slot. The first spring member has a distal end and a proximal end. The second spring member extends substantially parallel with and spaced apart from the first spring member along substantially an entire length of the first spring member. The second spring member has a distal end and a proximal end. The first connection is provided between the distal ends of the first and second spring members. The second connection is provided between the distal end of the second spring member and a top surface of the base spring. The first portion is arranged at a first angle relative to a horizontal plane. The second portion extends from the first portion. The slot extends rearward from the distal ends of the first and second spring members along at least half of a length of the first portion of the top spring assembly. The connector may be releasably connected to the proximal ends of the first and second spring members, and configured to connect the prosthetic foot to a lower limb prosthesis. The heel cushion is mounted to the base spring at a location spaced forward of a heel end of the base spring. The heel cushion is arranged to contact a bottom surface of the second spring member during use of the prosthetic foot.

The first angle of the top spring assembly may be in the range of about <NUM>° to about <NUM>°. The second portion of the top spring assembly may extend from the first portion in a substantially vertical direction. The prosthetic foot may further include a spacer positioned between the proximal ends of the first and second spring members. The first bond connection may provide a spacing between the distal ends of the first and second spring members. The first bond connection may include an adhesive. The second spring member may be spaced apart from the first spring member by spacers positioned at the distal and proximal ends of the first and second spring members. A thickness of the first spring member may be within <NUM>% of a thickness of the second spring member.

Another aspect of the present disclosure relates to a prosthetic foot having a connector, a base spring, a top spring assembly, and a heel cushion. The connector is configured to connect the prosthetic foot to a lower limb prosthesis. The base spring has a toe end portion and a heel end portion. The top spring assembly includes a first spring member having a distal end and a proximal end, a second spring member positioned between the base spring and the first spring member, the second spring member having a distal end and a proximal end, and first and second spacers. The first spacer is positioned between the distal ends of the first and second spring members. The second spacer is positioned between the proximal ends of the first and second spring members. The first and second spacers are configured to space the second spring member away from the first spring member when the prosthetic foot is in a rest state. During use of the prosthetic foot, a portion of the first spring member spaced between the distal and proximal ends of the first spring member moves relative to the second spring member. The top spring assembly further includes a distal end portion connected to the base spring and extending substantially horizontally, and a proximal end portion connected to the connector. The heel cushion is mounted to the base spring at a location spaced forward of a heel end of the base spring. The heel cushion is arranged to contact a bottom surface of the second spring member during use of the prosthetic foot.

The distal end portion of the top spring assembly may be connected to the base spring with a permanent bond connection, and material of the permanent bond connection may include an elastomeric material. The proximal end portion of the top spring assembly may include the proximal ends of the first and second spring members and may be releasably connected to the connector with at least one fastener. The distal ends of the first and second spring members may be connected to each other with a bond connection, and material of the bond connection may define the first spacer. The top spring assembly may have a first portion arranged at an angle in the range of about <NUM>° to about <NUM>° relative to a horizontal plane, and a second portion extending substantially vertically. The top spring assembly may be spaced apart from the base spring. The material of the bond connection may include an elastomeric material. The heel cushion may be releasably attached to the base spring, and the heel cushion may include an elastomeric material. The distal end of the second spring member may extend distally further than the distal end of the first spring member.

A further aspect of the present disclosure relates to a method of manufacturing a prosthetic foot. The method includes providing a base spring, a connector, a heel cushion, first and second spring members, and a spacer, arranging the first and second spring members in parallel with each other with portions of the second spring member positioned below and/or rearward of the first spring member, connecting distal ends of the first and second spring members to each other (e.g., by bonding using an elastomeric material), and arranging the spacer between proximal ends of the first and second spring members. The spacer spaces the first and second spring members apart when the prosthetic foot is in a rest position. The method also includes connecting the proximal ends of the first and second spring members to the connector with at least one fastener, connecting the distal end of the second spring member to a toe end portion of the base spring, the distal ends of the first and second spring members being arranged substantially parallel with a top surface of the base spring, and mounting the heel cushion to the base spring at a location spaced forward of a heel end of the base spring, the heel cushion contacting a bottom surface of the second spring member.

The proximal ends of the first and second spring members may be arranged substantially vertically. The method may also include providing the first and second spring members with a lower portion and an upper portion, arranging the lower portion at an angle of about <NUM>° to about <NUM>° relative to a horizontal plane, and arranging the upper portion substantially vertically. The base spring may include a sandal slot formed in the toe end portion, and bonding the distal end of the second spring member to the base spring may include connecting to the base spring at a location spaced posterior of the sandal slot. A portion of the first spring member may be movable into contact with the second spring member during use of the prosthetic foot. The connections between the first and second spring members, and between the top spring assembly and the base spring may be a bond connection using, for example, an elastomeric material. The material of the bond connections may space the first and second spring members from each other, and may space the top spring assembly from the base spring.

Features which are believed to be characteristic of the concepts disclosed herein, both as to their organization and method of operation, together with associated advantages will be better understood from the following description when considered in connection with the accompanying figures. Each of the figures is provided for the purpose of illustration and description only, and not as a definition of the limits of the claims.

A further understanding of the nature and advantages of the embodiments may be realized by reference to the following drawings.

While the embodiments described herein are susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, the exemplary embodiments described herein are not intended to be limited to the particular forms disclosed. Rather, the instant disclosure covers all modifications, equivalents, and alternatives falling within the scope of the appended claims.

The present disclosure is generally directed to prosthetic devices, and more particularly relates to prosthetic foot devices, which are also referred to as a foot prostheses. The prosthetic foot embodiments disclosed herein may provide certain advantages as compared to other prosthetic foot devices. For example, the prosthetic foot devices of the present application may provide improved rollover characteristics, such as increased smoothness during rollover. The prosthetic foot may include an upper or top spring assembly having a pair of leaf springs attached at opposite ends with a gap provided between the leaf springs. The top spring assembly is combined with a base spring and is attached to the base spring at a toe region of the base spring. A heel cushion is positioned between the top spring assembly and the base spring in a heel region of the base spring. The heel cushion may be mounted directed to the base spring and arranged to contact a bottom surface of the top spring assembly. The heel cushion may be interchangeable to adjust heel stiffness.

The toe end of the prosthetic foot may include a split extending along a length dimension of the prosthetic foot. The split may be arranged along a longitudinal centered line of the prosthetic foot to provide medial/lateral compliance. The split may extend through portions of the base spring and the top spring assembly.

The prosthetic foot design is targeted generally to meet the needs of a typical, active amputee. The prosthetic foot is designed for comfortable walking and many common conditions encountered by an amputee, rather than being narrowly focused towards a particular user group such as runners, skiers, swimmers, etc..

The top spring assembly may have various shapes and designs. In one example, the top spring assembly includes a generally horizontal portion that extends substantially parallel to the base spring, and an upper portion that extends in a substantially vertical direction to provide an L-shaped construction. Other designs have a lower profile that does not include the vertical portion of the L-shaped design. Still further embodiments may include a vertical portion having a greater length that extends further vertically upward relative to a base spring.

The base spring may extend further in an anterior direction than the most anterior point of the top spring assembly. The base spring may include a sandal slot position adjacent to the split formed along the centerline that provides medial/lateral compliance. In at least some embodiments, the first and second leaf springs of the top spring assembly may terminate at different anterior locations (e.g., the upper most leaf spring being spaced further posteriorly as compared to the lower leaf spring). Further, a heel end of the base spring may extend further posteriorly beyond the heel cushion. This arranged at the heel end of the base spring provides a heel lever arm located posterior to the heel cushion.

The prosthetic foot of the present disclosure may include various combinations of features that provide certain advantages as compared to known prosthetic feet. Once such combination of features includes a multi-spring top spring assembly wherein the springs are connected at opposite ends and include a gap or spacing between each other along the lengths of the springs between the connection points at the opposite ends. The top spring assembly is connected to a full-length base spring in a toe region of the base spring, and at a location that is spaced posterior of an anterior end of the base spring. The top spring assembly may be connected to the base spring at only one location. The prosthetic foot includes a replaceable elastomeric heel cushion positioned between the base spring and the top spring assembly in a heel end of the prosthetic foot. Typically, the heel cushion is detached from the top spring assembly, but is arranged to contact a bottom surface of the top spring assembly, particularly during use. The top spring assembly may include leaf springs having different lengths. The different lengths may allow a gradual change in the stiffness of the top spring assembly at various locations along the length of the prosthetic foot (e.g., in the toe region). One advantage of this particular combination of features is that the flexibility of the base plate does not have as much influence on performance. To some degree, the base plate may, at the connection point to the top spring assembly, pivot or otherwise move due to the type of connection that is provided between the top spring assembly and the base spring. In at least one example, the connection is provided by an adhesive bond or other bond structure that provides at least some flexibility and/or elasticity. Heel performance of the prosthetic foot may also be enhanced by this pivoting provided by a flexible adhesive bond between the base spring and the top spring assembly, or may be accomplished by flexibility in the base spring. In this particular embodiment, the prosthetic foot includes bond flexibility at the connection between the base spring and the top spring assembly as well as flexibility in the base spring provided by the structure of the base spring and the split in the toe end portion. A flexible bond between the upper spring assembly and the distal plate may act as a film hingeas described in <CIT>. A flexible distal plate may also contribute to film hinge behavior. It may be possible to tailor the contribution of the distal plate to heel performance by adjusting these and other design parameters. The heel performance is primarily determined by compressibility of the heel cushion, although the shape and position of the heel cushion may also contribute to heel performance. Thus, various features contribute to achieving a desired heel function for the prosthetic foot. By transferring load during heel strike from the posterior portion of the base spring to the posterior portion of the top spring assembly, the heel cushion reduces stress at the connection between the base spring and the upper spring assembly located in the anterior region of the prosthetic foot.

Referring now to <FIG>, an example prosthetic foot assembly <NUM> is shown and described. The prosthetic foot assembly <NUM> includes a cosmesis <NUM> and a prosthetic foot <NUM>. The cosmesis <NUM> is a hollow structure in which portions of the prosthetic foot <NUM> are positioned. The cosmesis <NUM> provides an aesthetic covering for the prosthetic foot <NUM> to give the appearance of an actual foot. <FIG> illustrate the prosthetic foot <NUM> in further detail. The prosthetic foot <NUM> is intended to be used inside a shoe, the heel height being raised to accommodate the heel of a typical shoe.

Referring now to <FIG> and <FIG>, the prosthetic foot <NUM> is shown including a base spring <NUM>, a top spring assembly <NUM>, a connector assembly <NUM>, and a heel cushion <NUM>. The top spring assembly <NUM> is connected to the base spring <NUM> in a toe end area at a toe end connection <NUM>. The toe end connection <NUM> may include a bond connection formed by, for example, an adhesive bond. The toe end connection <NUM> may be formed using an elastic, flexible material that provides at least some relative movement between the base spring <NUM> and top spring assembly <NUM> (e.g., rotational movement about a vertical axis, compression, and translational movement in the anterior/posterior and/or medial/lateral direction). The toe end connection <NUM> may provide the sole connection point between the base spring <NUM> and top spring assembly <NUM>. Typically, the heel cushion <NUM> is mounted directly to a top surface of the base spring <NUM> and arranged to contact a bottom surface of the top spring assembly <NUM> as shown in, for example, <FIG> and <FIG>. The heel cushion <NUM> may be releasably connected to the base spring <NUM>. Alternatively, heel cushion <NUM> may be releasably connected to the top spring assembly. In at least some examples, the heel cushion <NUM> is connected to the base spring <NUM> with an interference fit connection using, for example, a retainer <NUM> that is mounted to the top surface of the base spring <NUM>. The heel cushion <NUM> may be replaceable with other heel cushions having different properties such as increased or reduced stiffness, compressibility, damping capability, etc. Heel cushions of different sizes and shapes may also be used in place of the heel cushion <NUM> shown in the figures. In some examples, the prosthetic foot <NUM> may be operable without any heel cushion <NUM>.

The connector assembly <NUM> may be releasably attached to the top spring assembly <NUM> at its proximal end. In at least one example, the connector assembly <NUM> is releasably connected using one or more fasteners 92a, 92b. Connector assemblies with different connector features such as a pyramid connector <NUM> may be used. In at least some examples, the pyramid connector is a replaceable component of the connector assembly <NUM>. In other embodiments, the pyramid connector is integrally formed with remaining portions of the connector assembly and mounted directly to the top spring assembly. Other connector features besides a pyramid connector may be used as part of the connector assembly for securing the prosthetic foot <NUM> to another prosthetic member such as a lower leg pylon, a socket, or the like.

The base spring <NUM> is shown including a toe end <NUM>, a heel end <NUM>, a sandal slot <NUM>, and a balance slot <NUM>. The base spring <NUM> may also include a top surface <NUM>, a bottom surface <NUM>, and a heel cushion retainer <NUM> positioned at a heel end portion of the base spring <NUM>. The retainer <NUM> may include a cavity <NUM> and a rim <NUM> to help releasably secure the heel cushion <NUM> to the base spring <NUM>. The base spring <NUM> may also include a maximum length L<NUM> (see <FIG>), a maximum width W<NUM> (see <FIG>), a heel lever length L<NUM> (see <FIG>) extending posterior of the heel cushion <NUM>, and a balance slot length L<NUM> (see <FIG>). Typically, the maximum length L<NUM> is in the range of about <NUM> to about <NUM>, depending on foot size. The maximum width W<NUM> is typically in the range of about <NUM> to about <NUM>. The heel lever length L<NUM> is typically in the range of about <NUM> to about <NUM>, and more particularly in the range of about <NUM> to about <NUM> cn. The L<NUM> is typically in the range of about <NUM> to about <NUM>, and more particularly about <NUM> to about <NUM>. The dimensions of the base spring <NUM> may depend largely on the foot size.

The sandal slot <NUM> may also have a length Ls. The length Ls is typically in the range of about <NUM> to about <NUM>. The sandal slot <NUM> is formed in the toe end portion of the base spring <NUM> and extends posterior from an interior most edge of the base spring <NUM>. The balance slot <NUM> is also formed at the toe end portion beginning at the anterior most edge of the base spring <NUM> and extending posteriorly. In at least some embodiments, the balance slot <NUM> is aligned with a longitudinal center line of the base spring <NUM>. The balance slot <NUM> may provide enhanced medial/lateral compliance for the prosthetic foot <NUM>, particularly when walking on uneven surfaces.

As shown in at least <FIG> and <FIG>, the base spring <NUM> has a contoured shape along its length. The side profile of the base spring <NUM> undulates between concave and convex shapes. In some examples, the distal surface of the base spring <NUM> is preferably convex in an anterior section, transitions to concave in an arch or mid-section, and may transition back to convex at the posterior end. These contours and the location of the contours, particularly relative to the toe end connection <NUM> and the heel cushion <NUM>, may provide improved rollover smoothness, enhanced energy feedback to the user, stability, and comfort during use of the prosthetic foot. Providing the lever portion extending posterior of the heel cushion <NUM> may also provide improved smoothness in the rollover and energy feedback during use.

The top spring assembly <NUM> is shown including first and second spring members <NUM>, <NUM>, a first spacer <NUM> at the toe end portion of the prosthetic foot, a second spacer <NUM> positioned at a proximal end of the top spring assembly <NUM> and a gap G provided between the first and second spring members <NUM>, <NUM> along their entire length. The first and second spring members <NUM>, <NUM> may be referred to as leaf springs. The first and second spring members <NUM>, <NUM> may extend generally in parallel with each other along their entire lengths. The first spacer <NUM> may be provided as a bond connection between the first and second spring members <NUM>, <NUM>. In at least some examples, the first spacer <NUM> comprises the same bond material as used for the toe end connection <NUM> between the top spring assembly <NUM> and the base spring <NUM>. In at least some embodiments, the first spacer <NUM> is positioned generally in alignment with the toe end connection <NUM> so as to be positioned vertically above the toe end connection <NUM>, or at least partially overlapping the toe end connection <NUM> in a length dimension of the base spring <NUM>. The first spacer <NUM> may provide a permanent connection between the first and second spring members <NUM>, <NUM>. The material of first spacer <NUM> may provide at least some relative movement between the first and second spring members <NUM>, <NUM> (i.e., rotational movement about a vertical axis, translational movement in an anterior, posterior or medial/lateral direction, compression, etc.). The material of first spacer <NUM> may be elastic so as to return to its original shape upon removal of a force that is used to compress or deform the first spacer <NUM>.

The second spacer <NUM> may comprise a rigid material that is non-compressible and/or non-elastic. The second spacer <NUM> may be positioned at a proximal most end of the top spring assembly <NUM>. The second spacer <NUM> may be aligned with the connector assembly <NUM>, or at least portions thereof. In the illustrated embodiment, the second spacer <NUM> includes apertures through which the fasteners 92a, 92b extend for connection of the connector assembly <NUM> to the top spring assembly <NUM>.

The first and second spacers <NUM>, <NUM> may define the size of the gap G when the prosthetic foot <NUM> is in a rest state. Typically, the gap G is provided along an entire length of the first and second spring members <NUM>, <NUM> when the prosthetic foot <NUM> is in a rest state (i.e., prior to application of a force during use of the prosthetic foot <NUM>). Alternatively, the two upper springs <NUM>, <NUM> may abut (e.g., directly contact each other) at the connector location as shown in <FIG>. The gap G may vary in size during operation of the prosthetic foot <NUM>. For example, the gap G may reduce in size at the first spacer <NUM> if the material of the first spacer <NUM> is compressible during use. In another example, the gap G may reduce or change size at locations between the first and second spacers <NUM>, <NUM> during use. For example, applying a force from a user during a gait cycle may change the size of gap G at various phases of the gait cycle (e.g., at heel strike, stance phase, and toe off), as the forces are applied and released during use by a wearer, those forces are absorbed and/or fed back through the base spring <NUM> and heel cushion <NUM>. In at least some embodiments, the first spring member <NUM> may come into contact with the second spring member <NUM> during use of the prosthetic foot (i.e., the gap reduces to zero).

The second spring member <NUM> is shown having an anterior end <NUM>, a proximal end <NUM>, a horizontal portion <NUM>, a vertical portion <NUM>, a slot <NUM>, and fastener apertures 68a, 60b. The second spring member <NUM> has an overall length L<NUM> as shown in <FIG>, a maximum width W<NUM> as shown in <FIG>, and a length L<NUM> for slot <NUM> as shown in <FIG>. The horizontal portion <NUM> may have a radius of curvature R<NUM> as shown in <FIG> and <FIG>. The second spring member <NUM> also has a bend radius R<NUM> at the intersection between the horizontal and vertical portions <NUM>, <NUM>. The radius of curvature R<NUM> may be variable along the length from the anterior end <NUM> in a posterior direction. The radius R<NUM> is typically in the range of about <NUM> to about <NUM>, and more particularly about <NUM> to about <NUM>. The bend radius R<NUM> is typically in the range of about <NUM> to about <NUM>, and more particularly about <NUM> to about <NUM>. Although the horizontal portion <NUM> extends generally in a horizontal direction, it may be arranged at an angle α relative to a horizontal plane as shown in at least <FIG>. The angle α may be measured along that part of the horizontal portion <NUM> that is posterior of the first spacer <NUM>. The angle α is typically in range of about <NUM>° to about <NUM>°, and more particularly about <NUM>° to about <NUM>°.

The first spring member <NUM> may include an anterior end <NUM>, a proximal end <NUM>, a horizontal portion <NUM>, a vertical portion <NUM>, a slot <NUM>, and fastener apertures 72a, 72b. The first spring member <NUM> may have an overall length L<NUM> as shown in <FIG>, a maximum width W<NUM> as shown in <FIG>, and a length L<NUM> for slot <NUM> as shown in <FIG>. The slot <NUM> may be formed at the anterior end <NUM> and extend posteriorly. The slot <NUM> may be aligned with the slot <NUM> of the first spring member <NUM> and the balance slot <NUM> formed in base spring <NUM>. In at least some examples, the slots <NUM>, <NUM>, <NUM> may extend in a posterior direction to a common location. The slots <NUM>, <NUM>, <NUM> may terminate at different locations in the anterior direction as shown in at least <FIG>. The slots <NUM>, <NUM> may be aligned with a center line of the base spring <NUM> and top spring assembly <NUM> so as to provide balanced medial/lateral pronation and compliance during use of the prosthetic foot.

The second spring member <NUM> may include a radius of curvature R<NUM> for the horizontal portion <NUM> along its length. The radius R<NUM> may be variable along its length from the anterior end <NUM> toward the vertical portion <NUM>. The first spring member <NUM> may also include a bend radius R<NUM>. Typically, the radiuses R<NUM>, R<NUM> are similar to the radiuses R<NUM>, R<NUM>. Radius R<NUM> may be in the range of about <NUM> to about <NUM>, and more particularly about <NUM> to about <NUM>. R<NUM> may be in the range of about <NUM> to about <NUM>, and more particularly about <NUM> to about <NUM>. Because the first spring member <NUM> is positioned on an upper side and nested within the concave curvature of the second spring member <NUM>, the radius R<NUM> is typically smaller than the radius R<NUM>.

The horizontal portion <NUM> may be arranged at an angle θ relative to a horizontal plane as shown in <FIG>. The angle θ may be in the range of about <NUM>° to about <NUM>°, and more particularly about <NUM>° to about <NUM>°. The angle θ typically is the same or similar to the angle α for horizontal portion <NUM>.

The top spring assembly <NUM> is mounted to the base spring <NUM> as shown in at least <FIG>. The heel cushion <NUM> is arranged to contact a bottom or downward facing side or surface of the top spring assembly <NUM> (e.g., a bottom surface of second spring member <NUM> as shown in <FIG>). Although the heel cushion <NUM> is shown connected to the base spring <NUM> and not the top spring assembly <NUM>, other embodiments may provide the heel cushion <NUM> connected to both the base spring <NUM> and top spring assembly <NUM>, or connected only to the top spring assembly <NUM> (e.g., the retainer <NUM> is mounted to the bottom surface of second spring member <NUM> for releasable attachment of the heel cushion <NUM>).

The heel cushion <NUM> may be releasably mounted to the base spring <NUM> (or top spring assembly <NUM>). Alternatively, the heel cushion <NUM> may be permanently connected to the base spring <NUM>. The replaceability of heel cushion <NUM> may provide customization of the amount of cushioning, energy dampening, and the like provided by heel cushion <NUM>. Heel cushion <NUM> may be connected with an interference fit connection. Other embodiments may provide for the heel cushion <NUM> to be secured with a positive connection such as, for example, a fastener, clip, bracket or the like.

The heel cushion <NUM> may include a top surface <NUM> (see <FIG> and <FIG>), a tapered shape having a variable thickness along its length, a bottom surface <NUM>, and top and bottom perimeter rims <NUM>, <NUM>. The tapered shape may provide for a smaller thickness T<NUM> at an anterior end as compared to a greater thickness T<NUM> at a posterior end of the heel cushion <NUM>, as shown in <FIG>. The tapered shape of the heel cushion <NUM> may match the angle α and/or curvature R<NUM> of the second spring member <NUM>. As such, the top surface <NUM> may have a contoured shape rather than a planar shape. Similarly, the bottom surface <NUM> may have a shape that matches the contour or curvature of the top surface of the base spring <NUM>, as shown in at least <FIG>.

The heel cushion <NUM> may comprise a shock absorbing, dampening material such as, for example, silicone or urethane elastomers including, for example, silicone or urethane foams. In some embodiments, the heel cushion <NUM> may include a plurality of different materials, layers of materials, or separate components that are secured together as an assembly to provide the desired cushioning properties. In one example, the heel cushion <NUM> includes a foam material encapsulated within a protective polymer shell. In another example, the heel cushion <NUM> includes a gel material or capsule that is encapsulated within a foam material.

The connector assembly <NUM> includes a base <NUM>, fastener bores 96a, 96b, a spring assembly seat <NUM>, a bore <NUM>, a pyramid connector <NUM>, and a fastener <NUM>. The fastener bores 96a, 96b are receptive of the fasteners 92a, 92b. In at least some examples, the fastener bores 96a, 96b include threads that threadably engage with threads of the fasteners 92a, 92b. In other examples, the fastener bores 96a, 96b are pass-through bores and the fasteners 92a, 92b extend through the bores and threadably engage with nuts positioned on an opposite side of the base <NUM>. The spring assembly seat <NUM> may be shaped and sized to interface with one or both of the first and second spring members <NUM>, <NUM>. The spring assembly seat <NUM> may include a lip or edge that engages a proximal most surface of, for example, the first spring member <NUM> at the proximal end <NUM>. This lip or edge may provide a more secure connection and interface between the connector assembly <NUM> and the top spring assembly <NUM>.

The bore <NUM> may be sized to receive a portion of the pyramid connector <NUM>. The bore <NUM> may include a first portion sized to receive the pyramid connector <NUM> and a second portion (e.g., a threaded bore) that threadably engages with threads of the fastener <NUM>. The bore <NUM> may be sized to receive pyramid connectors <NUM> of different sizes and shapes, or different types of connectors that may be used to secure the prosthetic foot <NUM> to a separate lower leg prosthetic member.

The base spring <NUM> and first and second spring members <NUM>, <NUM> may comprise a fiber reinforced composite material such as, for example, carbon fiber reinforced composite. The first spacer <NUM> may include an adhesive bond comprising a flexible adhesive such as, for example, a urethane adhesive having a Shore A hardness in the range of about <NUM> to about <NUM>. During manufacture of the top spring assembly <NUM>, the first and second spring members <NUM>, <NUM> may be bonded together using a removable gasket between the springs to create a sealed space for the adhesive, and the adhesive is then injected into the space.

The first spring member <NUM> may be shorter in length Ls than the length L<NUM> for the second spring member <NUM>. This difference in length may allow for a somewhat gradual change in stiffness in the top spring assembly <NUM>. Although two spring members <NUM>, <NUM> are shown as part of the top spring assembly <NUM>, other embodiments may utilize more than two leaf spring elements, and the leaf spring elements may have the same or different lengths.

The second spacer <NUM> may comprise a lightweight material such as, for example, aluminum, nylon or fiberglass sheet material (e.g., fiberglass G-<NUM>). The top spring assembly <NUM> may provide a connection between the first and second spring members <NUM>, <NUM> at opposite ends with a gap G provided there between, thereby providing a number of unexpected structural advantages. These advantages in connection with the type of spacers <NUM>, <NUM>, the toe end connection <NUM>, the heel cushion <NUM>, and/or other features may provide a number of performance advantages as compared to known prosthetic feet. For example, a dual, narrow cantilever beam, one located above the other and with a space in between the upper and lower beams, and with frictionless spacer at the free end to transmit an applied vertical force from the upper beam to the lower beam at the free end, may result in about <NUM>-<NUM>% reduction in bending stress and about <NUM>-<NUM>% reduction in shear stress as compared to an equivalent stiffness single cantilever beam. While the top spring assembly <NUM> does not duplicate the boundary conditions of this idealized model exactly, these boundary conditions are predominately accurate. Because stresses are reduced by using the dual upper spring design, a prosthetic foot utilizing this dual spring design exhibits at least one of improved durability and improved flexibility as compared to single spring designs and dual spring designs without at least one spacer included. Many of the advantages of the dual cantilever beam designs disclosed herein may be maximized when the two beams (e.g., first and second spring members <NUM>, <NUM>) have substantially equal bending stiffness. If the beams are constructed of unidirectional fiber reinforced composite lamina, the maximum strength/stiffness ratio may be best achieved when both beams have substantially the same lamina orientation and thickness. As the difference between the bending stiffness of the upper and lower beams increases, the advantages of a dual cantilever spring design typically diminish.

The heel cushion <NUM> may comprise a silicone or urethane elastomer (e.g., an elastomer with the Shore hardness range of about 50A to about 90A). The heel cushion <NUM> may be retained with retainer <NUM> in a way that extends around an entire perimeter of the heel cushion <NUM>. Other embodiments may provide for a retainer that extends around only a portion of perimeter of the heel cushion <NUM>. The retainer <NUM> may be bonded to the top surface <NUM> of the base spring <NUM> using, for example, an adhesive. In some embodiments, both the adhesive and the retainer <NUM> are somewhat flexible to avoid detachment of the retainer <NUM> from the base spring <NUM> when the base spring <NUM> flexes during use. The retainer <NUM> and adhesive may comprise a plastic material having a Shore hardness in the range of, for example, about 90A to about 50D. Alternatively, the retainer <NUM> may be cast into the structure of base spring <NUM> along the top surface <NUM> thereof, which may eliminate the need for use of an adhesive or other bonding agent.

The retainer <NUM> may help keep the heel cushion <NUM> in place by utilizing geometric interlocking features. These interlocking features may include angled (e.g., wedge-shaped) features in the retainer and along an exterior of the heel cushion <NUM>, wherein corresponding surfaces interface to provide a connection The heel cushion <NUM> may be deformed or compressed in order to fit into the interior of the retainer <NUM>, and then expanded automatically to its original shape thereby creating an interference fit connection between the features of the retainer <NUM> and the heel cushion <NUM>. Alternatively, the retainer <NUM> and the heel cushion utilize a rib that fits into a recess, wherein the rib and recess may be formed on either the retainer <NUM> or heel cushion <NUM>.

Generally, the base spring <NUM> extends from the toe region to a heel region of the prosthetic foot. The base spring <NUM> may extend from an interior most point of the prosthetic foot to a posterior most point of the prosthetic foot. The top spring assembly <NUM> may be connected to the base spring 12A at a location spaced anterior of an anterior most edge of the base spring <NUM>. In at least one example, the top spring assembly <NUM> is positioned posterior of the sandal slot <NUM> formed at the distal end of the base spring <NUM>. The base spring <NUM> may extend in an anterior direction at least as far as an anterior most point along a length of the top spring assembly <NUM>.

As discussed above, the slot or split <NUM> formed in the base spring <NUM> from the anterior edge in a posterior direction may be aligned with the slots or slits <NUM>, <NUM> formed in the top spring assembly <NUM> from the anterior end of the top spring assembly <NUM> extending in a posterior direction. These slots or splits may provide for the entire prosthetic foot <NUM> to be divided into medial and lateral sides at least in the toe and midfoot regions of the prosthetic foot.

The top spring assembly <NUM> includes first and second spring members <NUM>, <NUM> that extend to different anterior positions along the length of the prosthetic foot. At least <FIG> illustrates the second spring member <NUM> extending further in an anterior direction than the first spring member <NUM>. The first spacer <NUM> is positioned at the anterior most edge of the second spring member and spaced posterior of the anterior most edge of the second spring member <NUM>.

The top spring assembly <NUM> extends generally parallel with the base spring <NUM> in the toe and midfoot regions of the base spring <NUM>. The top spring assembly <NUM> may extend in a generally vertical direction relative to the base spring <NUM> in the heel end portion of the prosthetic foot. As described above, other embodiments may provide for the top spring assembly <NUM> to continue extending in a generally horizontal or slightly angled direction relative to the base spring <NUM> and/or a horizontal plane through the heel end portion.

Referring now to <FIG>, another example prosthetic foot <NUM>-a is shown. The prosthetic foot <NUM>-a includes the same or similar components as the prosthetic foot <NUM> described above with reference to <FIG> with exception of the top spring assembly <NUM>-a. The top spring assembly <NUM>-a does not include second spacer <NUM> at its proximal end. The first and second spring members <NUM>-a, <NUM>-a of the top spring assembly <NUM>-a are arranged in direct contact with each other at the proximal end. The elimination of spacer <NUM> may result in several changes in the top spring assembly <NUM>-a. For example, the radius of curvature R<NUM> of the second spring member <NUM>-a may be smaller than the radius of curvature R<NUM> of second spring member <NUM> shown in <FIG>. The radius of curvature R<NUM> of the first spring member <NUM>-a may be greater than the radius of curvature R<NUM> of first spring member <NUM> shown in <FIG>. Removal of the spacer <NUM> may also alter the size of radius of curvatures R<NUM> and R<NUM> as compared to those values for first and second spring members <NUM>, <NUM> shown in <FIG> (e.g., reduce R<NUM> and increase R<NUM>).

Additionally, the gap G provided between the first and second spring members <NUM>-a, <NUM>-a may vary along the length of the first and second spring members <NUM>-a, <NUM>-a from the first spacer <NUM> toward the proximal end of top spring assembly <NUM>-a where the first and second spring members <NUM>-a, <NUM>-a are in direct contact with each other. The first and second spring members <NUM>-a, <NUM>-a may extend generally in parallel with each other along the portions <NUM>, <NUM> to provide a substantially constant gap G in that portion of the top spring assembly <NUM>-a, have a greater or smaller gap G in the area of radius of curvatures R<NUM>, R<NUM>, and then have a tapered gap G to the point of contact between the end portions <NUM>, <NUM>.

The gap G may extending along only a portion of the length of the first and/or second spring members <NUM>-a, <NUM>-a. For example, the gap G may be provided along a percentage of the length L<NUM> of the second spring member <NUM>-a, such as in the range of about <NUM>% to about <NUM>% of the length L<NUM>. During use of the prosthetic foot <NUM>-a, portions of the first and second spring members <NUM>-a, <NUM>-a may move toward and/or away from each other to alter the size of gap G at various locations along the length of the top spring assembly <NUM>-a. In at least some embodiments, portions of the first and second spring members <NUM>-a, <NUM>-a may contact each other at locations spaced distal of where the first and second spring members <NUM>-a, <NUM>-a are shown contacting each other in <FIG>.

The first spacer <NUM> may be provided as a bond connection between the first and second spring members <NUM>-a, <NUM>-a. In at least some examples, the first spacer <NUM> may comprise a relatively incompressible material such as those described above related to spacer <NUM>. The first spacer <NUM> may be provided as a separate piece that is secured in place between the first and second spring members <NUM>-a, <NUM>-a using an adhesive or other bonding agent. The material of first spacer <NUM> may provide at least some relative movement between the first and second spring members <NUM>-a, <NUM>-a (i.e., rotational movement about a vertical axis, shear displacement or translational movement in an anterior, posterior or medial/lateral direction, compression, etc.). The material of first spacer <NUM> may be elastic so as to return to its original shape upon removal of a force that is used to compress or deform the first spacer <NUM>.

Referring now to <FIG>, another example prosthetic foot <NUM>-b is shown. The prosthetic foot <NUM>-b includes many of the same or similar components as the prosthetic foot <NUM> and the prosthetic foot <NUM>-a described above with reference to <FIG> with exception of the top spring assembly <NUM>-b. The top spring assembly <NUM>-b does not include vertical portions <NUM>, <NUM> as do the top spring assemblies <NUM> and <NUM>-a. The first and second spring members <NUM>-b, <NUM>-b of the top spring assembly <NUM>-b are arranged substantially horizontally along their length from their anterior ends <NUM>, <NUM> to their proximal ends <NUM>, <NUM>. The elimination of vertical portions <NUM>, <NUM> from the first and second spring members <NUM>-b, <NUM>-b may result in several changes in the top spring assembly <NUM>-b as compared to the embodiments shown in <FIG>. For example, the horizontal portion <NUM>-a, <NUM>-a of the first and second spring members <NUM>-b, <NUM>-b may be longer than the horizontal portions <NUM>, 66a of the first and second spring members <NUM>, <NUM> shown in <FIG>. The horizontal portions <NUM>-a, <NUM>-a may extend from the anterior ends <NUM>, <NUM> to the proximal ends <NUM>, <NUM>.

Additionally, the gap G provided between the first and second spring members <NUM>-b, <NUM>-b may have a reduced length from the first spacer <NUM> to the second spacer <NUM>. The gap G may be substantially constant when the prosthetic foot <NUM>-b is in a rest or unloaded state. During use of the prosthetic foot <NUM>-b, portions of the first and second spring members <NUM>-b, <NUM>-b may move toward and/or away from each other to alter the size of gap G at various locations along the length of the top spring assembly <NUM>-b. In at least some embodiments, portions of the first and second spring members <NUM>-b, <NUM>-b may contact each other.

The first spacer <NUM> may be provided as a bond connection between the first and second spring members <NUM>-b, <NUM>-b. In at least some examples, the first spacer <NUM> may comprise a relatively incompressible material such as those described above related to spacer <NUM>. The first spacer <NUM> may be provided as a separate piece that is secured in place between the first and second spring members <NUM>-b, <NUM>-b using an adhesive or other bonding agent. In other examples, material of first spacer <NUM> may provide at least some relative movement between the first and second spring members <NUM>-b, <NUM>-b (i.e., rotational movement about a vertical axis, shear displacement or translational movement in an anterior, posterior or medial/lateral direction, compression, etc.). The material of first spacer <NUM> may be deformable and/or elastic so as to return to its original shape upon removal of a force that is used to compress or deform the first spacer <NUM>.

The second spacer <NUM>-a may have many of the same or similar features and properties of second spacer <NUM> described above. The second spacer <NUM>-a may have a different arrangement of holes to receive one or more fasteners 92a-a. In some example, the prosthetic foot <NUM>-b may include a plurality of fasteners 92a-a to secure connector assembly <NUM>-a to the top spring assembly <NUM>. A base <NUM>-a of the connector assembly <NUM>-a may include one or more fastener holes to receive the one or more fasteners 92a-a. The base <NUM>-a may be sized and arranged to orient the pyramid connector <NUM> in a vertical orientation when the prosthetic foot is unloaded, as shown in <FIG>.

The fasteners 92a-a may be arranged side-by-side in a medial/lateral direction. In other arrangements, the fasteners 92a-a may be arranged in alignment with a length dimension of the prosthetic foot <NUM>-b. Although only one fastener 92a-a is shown in <FIG>, a plurality of fasteners 92a-a may be used. The fasteners 92a-a may provide a positive connection between the first and second spring members 40b, <NUM>-b, a positive connection between the top spring assembly <NUM>-b and the connector assembly <NUM>-a, and/or a positive connection between one or both of the first and second spring members <NUM>-b, <NUM>-b and the spacer <NUM>-a. In some examples, the fasteners 92a-a are connected directly to one or both of the first and second spring members <NUM>-b, <NUM>-b (e.g., to a threaded seat formed in one or both of the first and second spring members <NUM>-b, <NUM>-b), or may be connected to a nut <NUM> positioned on an opposite side of the top spring assembly <NUM>-b, as shown in <FIG>.

As is possible with the prosthetic feet <NUM>, <NUM>-a, the heel cushion <NUM> may be positioned between the base spring <NUM> and the top spring assembly <NUM>-b. In at least some embodiments, the heel cushion <NUM> is mounted to the base spring <NUM>, and may be releasably mounted to the base spring <NUM>. The heel cushion <NUM> is arranged to contact a bottom surface of the top spring assembly <NUM>-b, such as a long a bottom surface of the second spring member <NUM>-b.

An overall height H<NUM> of the prosthetic foot <NUM>-b may be substantially smaller than the heights H<NUM> and H<NUM> of the prosthetic feet <NUM>, <NUM>-a, respectively. The smaller height H<NUM> may provide a relatively low profile for the prosthetic foot <NUM>-b and the prosthetic foot <NUM>-b may be referred to as a low profile prosthetic foot. The prosthetic feet <NUM>, <NUM>-a may be referred to as high profile or medium profile prosthetic feet.

The prosthetic foot <NUM>-b may provide many of the same or similar functions and benefits related to performance and user comfort as described herein related to prosthetic feet <NUM>, <NUM>-a. For example, the prosthetic foot <NUM>-b may provide energy feedback, stability, force dampening and the like associated with the use of spaced apart spring members in the top spring assembly <NUM>-b, the use of a heel cushion <NUM> arranged in the specific location and having the size and shape shown in <FIG>, the shape and size of the top spring assembly <NUM>-b and base spring <NUM>, and the size, shape and orientation of the connector assembly <NUM>-a. Furthermore, the base spring <NUM> and top spring assembly <NUM>-b may include slots (e.g., slot <NUM> for base spring <NUM> and slots <NUM>, <NUM> for first and second spring members <NUM>-b, <NUM>-b) that provide medial/lateral pronation and ambulation for the prosthetic foot <NUM>-b, which may provide improved stability for the user, particularly on uneven ground surfaces.

The prosthetic feet <NUM>, <NUM>-a, <NUM>-b may be referred as dual or multiple toe spring prosthetic feet. The prosthetic feet <NUM>, <NUM>-a, <NUM>-b may be referred to as a single toe spring prosthetic feet. The heel assemblies, attachment assemblies, connection assemblies, and other features disclosed with reference to any single embodiment disclosed herein may be interchangeable with features of other prosthetic foot embodiments disclosed herein.

In alternative embodiments, the connection between the base spring and the top spring assembly and between the first and second spring members in the anterior region of the foot and may be provided with bolts or other fasteners. A rigid spacer may be provided between the spring members and/or between the top spring assembly and the base spring. The use of bolts or other fasteners in combination with an altered geometry of the first and second spring members may eliminate gaps that may otherwise exist at connection points at the anterior end of the prosthetic foot. In another embodiment, a connection between the first and second spring members may be made by wrapping carbon fiber or glass fiber around the first and second spring members at the connection point between the first and second spring members, and securing the spring members and the fiber by impregnating the fiber with epoxy or similar thermosetting resin. A similar connection may be made between the top spring assembly and the base spring.

In another example, the connection at the proximal end of the top spring assembly may be created by altering a geometry of the first and second spring members such that no gap exists at the connection points between the first and second springs (e.g., as shown in <FIG>). In this arrangement, a gap may still be provided between the first and second spring members at other locations along their lengths (e.g., as shown in <FIG>). In some embodiments, one or more of the first and second spring members may be inserted into a slot formed in the prosthetic connector (e.g., base <NUM> of connector assembly <NUM>), and the first and second spring members are secured together and to the prosthetic connector with an adhesive or a fastener.

Referring now to <FIG>, an example method <NUM> of manufacturing a prosthetic foot in accordance with the present disclosure is shown as a flow diagram. The method <NUM> includes, at block <NUM>, providing a base spring, a connector, a heel cushion, first and second spring members, and at least one spacer. Block <NUM> includes arranging the first and second spring members in parallel with each other with portions of the second spring member positioned below the first spring member. The second spring member may also be positioned rearward of the first spring member. The method <NUM> includes, at block <NUM>, connecting distal ends of the first and second spring members to each other, such as bonding together with an elastomeric material. The first and second spring members may be spaced apart from each other at their distal or anterior ends. Block <NUM> includes arranging the spacer between proximal ends of the first and second spring members. The spacer spaces the first and second members apart when the prosthetic foot is in a rest position. The method <NUM> includes, at block <NUM>, connecting the proximal ends of the first and second spring members to each other and to the connector with at least one fastener. In some arrangements, the proximal ends of the first and second spring members are arranged substantially vertically. Block <NUM> includes connecting the distal ends of the second spring member to a toe end portion of the base spring, such as a bond connection using an adhesive. The distal ends of the first and second spring members may be arranged substantially parallel with a top surface of the base spring. Block <NUM> includes mounting the heel cushion to the base spring at a location spaced forward of a posterior end of the base spring, the heel cushion arranged to contact a bottom surface of the second spring member.

The method <NUM> may also include providing the first and second spring members with a lower portion and an upper portion, arranging the lower portion at an angle of about <NUM>° to about <NUM>° relative to a horizontal plane, and arranging the upper portion substantially vertically. The method <NUM> may include providing the base spring with a sandal slot formed in the toe end portion, and connecting the distal end of the second spring member to the base spring at a location spaced posterior of the sandal slot. The method <NUM> may include moving a portion of the first spring member into contact with the second spring member during use of the prosthetic foot.

The method <NUM> may be modified or altered in accordance with the present disclosure to include more or fewer steps than those illustrated in the figures. Accordingly, the flow diagram shown in <FIG> could include any step or variation of methods, features and/or functionality described herein. Other types of methods are possible in accordance with the present disclosure including, for example, methods of using a prosthetic foot, methods of storing and releasing energy in a prosthetic foot during use, and methods related to adapting or customizing performance of a prosthetic foot (e.g., by interchanging a heel cushion, a top spring assembly, or connection materials, such as the first spacer <NUM> or toe end connection <NUM>).

The foregoing description, for purpose of explanation, has been described with reference to specific embodiments. However, the illustrative discussions above are not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many modifications and variations are possible in view of the above teachings. The embodiments were chosen and described in order to best explain the principles of the present systems and methods and their practical applications, to thereby enable others skilled in the art to best utilize the present systems and methods and various embodiments with various modifications as may be suited to the particular use contemplated.

Claim 1:
A prosthetic foot, comprising:
a base spring (<NUM>) having a toe end portion and a heel end portion;
a top spring assembly (<NUM>), comprising:
a first spring member (<NUM>) having a distal end and a proximal end;
a second spring member (<NUM>) having a distal end and a proximal end;
a first connection provided between the distal ends of the first and second spring members (<NUM>, <NUM>), and a second connection provided between the distal end of the second spring member (<NUM>) and a top surface of the base spring (<NUM>);
a slot extending rearward from the distal ends of the first and second spring members (<NUM>, <NUM>) along at least half of a length of the first portion (<NUM>, <NUM>) of the top spring assembly (<NUM>);
a connector (<NUM>) connected to the proximal ends of the first and second spring members (<NUM>, <NUM>), and configured to connect the prosthetic foot to a lower limb prosthesis;
a heel cushion (<NUM>) mounted to the base spring (<NUM>) at a location spaced forward of a heel end of the base spring (<NUM>), the heel cushion (<NUM>) arranged to contact a bottom surface of the second spring member (<NUM>) during use of the prosthetic foot, characterized in that
the second spring member (<NUM>) extends substantially parallel with and spaced apart from the first spring member (<NUM>) along substantially an entire length of the first spring member (<NUM>);
a first portion (<NUM>, <NUM>) of the first and second spring members (<NUM>, <NUM>) is arranged at a first angle relative to a horizontal plane; and
a second portion (<NUM>, <NUM>) of the first and second spring members (<NUM>, <NUM>) extends from the first portion (<NUM>, <NUM>).