WO2025080929A1 - Dual-stiffness prosthetic coupling member - Google Patents

Abstract

Exemplary embodiments of the present disclosure apparatus and methods for a prosthetic coupling member comprising a plurality of spring members configured to provide different levels of rotational stiffness. Specific embodiments include spring members with a substantially circular perimeter and a plurality of engagement members received within substantially circular openings within a housing. In particular embodiments the plurality of engagement members are configured to engage the protrusions upon rotation of the substantially circular perimeter of the second spring members within the substantially circular openings.

Description

DESCRIPTION

DUAL-STIFFNESS PROSTHETIC COUPLING MEMBER

CROSS-REFERENCE TO RELATED APPLICATIONS

[001] This application claims priority to U.S Provisional Patent Application Serial Number 63/589,677 filed October 12, 2023, the entire contents of which are incorporated by reference herein.

BACKGROUND INFORMATION

[002] Individuals with lower-limb amputations are at a higher risk of falling compared to able-bodied and other clinical populations in all phases of rehabilitation and are more likely to sustain life-altering injuries [1], Over half of those with a lower-limb amputation incur at least one fall per year and 49% report a fear of falling [2], While often a fall may only result in minor injuries or bruises, it can impact the person’s confidence in their balance and mobility. Consequently, the person may limit their physical activity and social participation, leading to a decline in overall physical and emotional health.

[003] Thus, falls pose a significant barrier to successful and continued rehabilitation, whether it be physical or emotional injury. The higher fall risk among individuals with lower- limb amputations is primarily due to the loss of the muscles crossing the ankle joint, which are critical to maintaining balance control during human locomotion [3, 4]. Prosthetic components are designed to provide appropriate ankle stiffness for needed stability and support. However, typical clinically -prescribed prosthetic devices are passive and only provide a singular stiffness level. Singular-stiffness prosthetic ankles replicate human ankle function in limited ways. In particular, they are highly ineffective when an amputee performs a turning task. Turning plays a critical role in activities of daily living as it can account for as much as 45 % of the steps in a given task [5]. Previous research has shown amputees are less stable than nonamputees during turning [6] and the residual limb contributes less to balance control than the intact limb [7].

[004] Accordingly, systems and methods are desired that overcome these and other limitations associated with existing apparatus and methods.

SUMMARY

[005] Certain embodiments include a prosthetic coupling member comprising: a first spring member comprising a substantially circular perimeter and a plurality of engagement members distributed around the substantially circular perimeter; a second spring member comprising a substantially circular perimeter and a plurality of engagement members distributed around the substantially circular perimeter; and a shaft extending between the first spring member and the second spring member; a housing comprising a substantially circular first opening and a substantially circular second opening. In specific embodiments, the first spring member is received within the substantially circular first opening; the second spring member is received within the substantially circular second opening; the shaft comprises a plurality of splines; the substantially circular first opening and the substantially circular second opening each comprise a plurality of protrusions extending inward to engage the spring member; the first spring member and the second spring member each comprise a plurality of flexible members engaged with the plurality of splines; the plurality of engagement members of the first spring member are configured to engage protrusions of the substantially circular first opening upon rotation of the substantially circular perimeter of the first spring member within the substantially circular first opening; and the plurality of engagement members of the second spring member are configured to engage protrusions of the substantially circular second opening upon rotation of the substantially circular perimeter of the second spring member within the substantially circular second opening.

[006] In particular embodiments, an engagement member of the plurality members of the first spring member is configured to engage adjacent protrusions of the substantially circular first opening upon rotation between 5 and 25 degrees of the substantially circular perimeter of the first spring member within the substantially circular first opening. In some embodiments, an engagement member of the plurality members of the second spring member is configured to engage adjacent protrusions of the substantially circular second opening upon rotation between 5 and 25 degrees of the substantially circular perimeter of the second spring member within the substantially circular second opening. In certain embodiments, the plurality of engagement members of the first spring member are configured to engage adjacent protrusions of the substantially circular first opening upon rotation between 10 and 20 degrees of the substantially circular perimeter of the first spring member within the substantially circular first opening.

[007] In particular embodiments, the plurality of engagement members of the second spring member are configured to engage adjacent protrusions of the substantially circular second opening upon rotation between 10 and 20 degrees of the substantially circular perimeter of the second spring member within the substantially circular second opening. In some embodiments, the plurality of engagement members of the first spring member are configured to engage adjacent protrusions of the substantially circular first opening upon rotation of approximately 15 degrees of the substantially circular perimeter of the first spring member within the substantially circular first opening.

[008] In specific embodiments, the plurality of engagement members of the second spring member are configured to engage adjacent protrusions of the substantially circular second opening upon rotation of approximately 15 degrees of the substantially circular perimeter of the second spring member within the substantially circular second opening. In certain embodiments, the housing is a modular housing comprising a first ring member coupled to a second ring member. In particular embodiments, the first or second spring member comprises titanium or steel. In some embodiments, the housing comprising a first coupling member and a second coupling member; the first coupling member is configured to couple to a first prosthetic member; and the second coupling member is configured to couple to a second prosthetic member. In certain embodiments, the first prosthetic member is a prosthetic pyramid adaptor and the second prosthetic member is a prosthetic foot.

[009] In particular embodiments, the first spring member has a first rotational stiffness; the second spring member has a second rotational stiffness; and the first rotational stiffness is different than the second rotational stiffness. Some embodiments further comprise: a third spring member received within the substantially circular first opening; and a fourth spring member received within the substantially circular second opening.

[010] In specific embodiments, the third spring member and the fourth spring member each comprise a plurality of flexible members engaged with the plurality of splines; the plurality of engagement members of the third spring member are configured to engage protrusions of the substantially circular first opening upon rotation of the substantially circular perimeter of the first spring member within the substantially circular first opening; and the plurality of engagement members of the fourth spring member are configured to engage protrusions of the substantially circular second opening upon rotation of the substantially circular perimeter of the second spring member within the substantially circular second opening.

[011] In certain embodiments, the prosthetic coupling member does not comprise an electrical, pneumatic or hydraulic power source. In particular embodiments, the first spring member and the second spring member are pre-loaded to exert an initial rotational stiffness between the housing and the shaft. In some embodiments, the plurality of protrusions of the substantially circular first opening are rotationally offset from the substantially circular second opening. In specific embodiments, the plurality of protrusions of the substantially circular first opening are rotationally offset from the substantially circular second opening by between 10- 20 degrees. In certain embodiments, the plurality of protrusions of the substantially circular first opening are rotationally offset from the substantially circular second opening by approximately 15 degrees.

[012] Exemplary embodiments include a method of providing varying levels or rotation stiffness in a prosthetic coupling member, the method comprising: providing a plurality of spring members contained within a housing; providing a shaft extending through the plurality of spring members; rotating the housing with respect to the shaft, where: a first spring member of the plurality of spring members provides a first level of rotational stiffness upon an initial rotation of the housing with respect to the shaft; and a second spring member of the plurality of spring members provides a second level of rotational stiffness upon further rotation of the housing with respect to the shaft.

[013] Exemplary embodiments of the present disclosure include apparatus and methods for a prosthetic coupling member. While a prosthetic ankle device is shown and described in the present disclosure as one exemplary embodiment, it is understood that other embodiments may be used in other applications. Specific embodiments include a prosthetic ankle device featuring dual-stiffness functionality while providing a lightweight, robust, compact and relatively inexpensive solution. Exemplary embodiments are also passive (requiring no external power to operate) and can be easily customized for each individual (e.g., by changing the springs used to be stiffer or more compliant) and can be mass produced.

[014] In an effort to improve balance control in lower-limb amputees, the inventors analyzed the effects of prosthetic foot stiffness on walking mechanics and balance control during turning. The inventors’ work resulted in a particularly intriguing discovery: a less stiff prosthesis decreases the peak-to-peak range of frontal plane whole body angular momentum (a measure of balance control), especially when the residual limb is on the inside of the turn [8], and conversely, balance control is improved with a stiffer ankle when the residual limb is on the outside of the turn. This suggests a prosthetic ankle with dual-stiffness that modulates stiffness based on whether the residual limb is on the inside or the outside of a turn may improve balance control for lower-limb amputees.

[015] Exemplary embodiments of the present disclosure incorporate a passive, dual stiffness feature into a prosthetic ankle thereby improving balance control without the need for an external power source. Exemplary embodiments further provide a stiffness preloading mechanism to change initial stiffness value and make the stiffness scalable. Accordingly, the stiffness is modulated based on whether the residual limb is on the inside or the outside of a turn being performed by the user when walking.

[016] As explained further below, particular embodiments of the present disclosure utilize a series of stackable, rotational springs that load when the ankle joint (or other joint as applicable) rotates. When the ankle is on the outside of a turn and inverts, the device provides a higher stiffness, and when the ankle is on the inside of a turn and the ankle everts, the device provides a lower stiffness. By incorporating a dual stiffness feature into a prosthetic ankle, exemplary embodiments allow for more compliance when the residual limb is on the inside of the turn versus the outside of the turn to improve balance control. In addition to the applications for use in the coronal plane disclosed herein, exemplary embodiments of the present disclosure can be used in other applications, including for example, rotated 90 degrees and used in the sagittal plane.

[017] In the following, the term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically.

[018] The use of the word “a” or “an” when used in conjunction with the term “comprising” in the claims and/or the specification may mean “one,” but it is also consistent with the meaning of “one or more” or “at least one.” The term “about” means, in general, the stated value plus or minus 5%. The use of the term “or” in the claims is used to mean “and/or” unless explicitly indicated to refer to alternatives only or the alternative are mutually exclusive, although the disclosure supports a definition that refers to only alternatives and “and/or.”

[019] The terms “comprise” (and any form of comprise, such as “comprises” and “comprising”), “have” (and any form of have, such as “has” and “having”), “include” (and any form of include, such as “includes” and “including”) and “contain” (and any form of contain, such as “contains” and “containing”) are open-ended linking verbs. As a result, a method or device that “comprises,” “has,” “includes” or “contains” one or more steps or elements, possesses those one or more steps or elements, but is not limited to possessing only those one or more elements. Likewise, a step of a method or an element of a device that “comprises,” “has,” “includes” or “contains” one or more features, possesses those one or more features, but is not limited to possessing only those one or more features. Furthermore, a device or structure that is configured in a certain way is configured in at least that way, but may also be configured in ways that are not listed.

[020] The terms “substantially” or “approximately” as used herein may be applied to modify any quantitative comparison, value, measurement, or other representation that could permissibly vary without resulting in a change in the basic function to which it is related. [021] The term “about” means, in general, within a standard deviation of the stated value as determined using a standard analytical technique for measuring the stated value. The terms can also be used by referring to plus or minus 5% of the stated value.

[022] Other objects, features and advantages of the present invention will become apparent from the following detailed description. It should be understood, however, that the detailed description and the specific examples, while indicating specific embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

[023] The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present disclosure. The invention may be better understood by reference to one of these drawings in combination with the detailed description of specific embodiments presented herein.

[024] FIG. 1 illustrates a perspective view of an apparatus according to an exemplary embodiment of the present disclosure.

[025] FIG. 2 illustrates an exploded view of components of the embodiment of FIG. 1.

[026] FIG. 3 illustrates a front view of the embodiment of FIG. 1 with the first spring member in a first position.

[027] FIG. 4 illustrates a illustrates a front view of the embodiment of FIG. 1 with the first spring member in a second position.

[028] FIG. 5 illustrates a side view of the embodiment of FIG. 1 .

[029] FIG. 6 illustrates a top view of the embodiment of FIG. 1.

[030] FIG. 7 illustrates a bottom view of the embodiment of FIG. 1.

[031] FIG. 8 illustrates a perspective view of a sub-assembly of FIG. 1.

[032] FIG. 9 illustrates a perspective view of a component of the sub-assembly of

FIG. 8.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

[033] Exemplary embodiments of the present disclosure include apparatus and methods for a prosthetic coupling member. Referring now to FIGS. 1-9, an exemplary embodiment of a prosthetic coupling member 100 is shown comprising a shaft 130 extending between a first spring member 110 and a second spring member 120 received within a housing 140. For purposes of clarity, each component of prosthetic coupling member 100 is not identified with a reference number in every figure.

[034] In the embodiment shown, housing 140 comprises a pair of ring members 146 as well as a first and second coupling members or pyramid adaptors 147 and 148. In the illustrated embodiment, first pyramid adaptor 147 is coupled to shaft 130 via a transfer member 240 (e.g. as shown particularly in FIG. 8), while second pyramid adaptor 148 is coupled to ring members 146 (e.g. via threaded apertures 158 as shown in FIG. 7). In the embodiment shown, pyramid adaptors 147 and 148 can be configured to engage a prosthetic limb or to engage bone tissue of a patient (e.g. via insertion into and fusion with the bone tissue). Accordingly, pyramid adaptor 147 and 148 can transfer the relative motion of the prosthetic limb or bone tissue to shaft 130 relative to ring members 146. In the illustrated embodiment, as shaft 130 is rotated with respect to ring members 146, transfer member 240 is configured to transfer the movement of pyramid adaptor 147 to rotation of spring members 110 and 120. In the particular embodiment shown, transfer member 240 comprises an aperture 246 through which shaft 130 is inserted. In addition transfer member is configured to be coupled to pyramid adaptor 147 via a threaded aperture 247 and coupled to shaft 130 via a threaded aperture 248. Accordingly, when pyramid adaptor 147 is rotated with respect to pyramid adaptor 148, pyramid adaptor 147 rotates with shaft 130 and pyramid adaptor 148 rotates with ring members 146. As shaft 130 is rotated with respect to ring members 146, spring members 110 and 120 provide increased rotational stiffness as described in further detail below.

[035] In the illustrated embodiment, first spring member 110 comprises a substantially circular perimeter 115 and a plurality of engagement members 117, while second spring member 120 comprises a substantially circular perimeter 125 and a plurality of engagement members 127. In addition, ring members 146 of housing 140 comprise a substantially circular first opening 141 comprising a plurality of protrusions 143 and a substantially circular second opening 142 comprising a plurality of protrusions 145. In the embodiment shown, shaft 130 comprises detachable caps 131 and 132, each comprising a plurality of splines 135. In other embodiments, splines 135 may be formed directly into the surface of shaft 130. Spring members 110 and 120 comprise flexible extensions 116 and 126, respectively, configured to engage splines 135 in the embodiment shown. It is understood that the configuration of spring members 110 and 120 shown in the figures is merely exemplary of one embodiment, and other embodiments according to the present disclosure may have one or more spring members with a configuration different from that shown in the figures.

[036] Engagement members 117 and 127 are configured to engage protrusions 143 and 145 upon rotation of the substantially circular perimeters 115 and 125 within substantially circular openings 141 and 142. In the embodiment shown, engagement members 117 and 127 are equally spaced around substantially circular perimeters 115 and 125, while protrusions 143 and 145 are also equally spaced around substantially circular openings 141 and 142. As shown in FIGS. 5 and 6, engagement members 117 and 127 are configured to respectively engage protrusions 143 and 145 upon clockwise or counter-clockwise rotation of substantially circular perimeters 115 and 124 within substantially circular openings 141 and 142. As engagement members 117 and 127 engage protrusions 143 and 145, flexible extensions 116 and 126 are slightly deformed (e.g. subjected to a bending force) due to the rotational forces exerted by splines 135 and protrusions 143 and 145. As the rotation of ring members 146 (and consequently, substantially circular openings 141 and 142 and protrusions 143 and 145) is increased with respect to shaft 130, the rotational stiffness of first and second spring members 110 and 120 is increased due to the increased bending of flexible extensions 116 and 126.

[037] In exemplary embodiments, ring members can be configured such that protrusions 143 and 145 are offset when viewed in a direction parallel to shaft 130 (e.g. as shown in FIGS. 3 and 4). In certain embodiments, protrusions 143 and 145 are offset by between 5 and 25 degrees, or more particularly between 10 and 20 degrees. In one specific embodiment, protrusions 145 are offset by approximately 15 degrees (the normal range for ankle rotation in the coronal plane) from protrusions 143 when viewed in the position shown in FIGS. 3 and 4. Protrusions 145 can be offset from protrusions 143 in either a clockwise or counterclockwise position depending on the application for the user. For example, if prosthetic coupling member 100 is used in a left ankle position, protrusions 145 can be offset to protrusions 143 in a clockwise position (when viewed in the position shown in FIGS. 3 and 4) to provide increased stiffness when the user is turning toward the right and the left ankle is in the outside position during the turn. When the ankle is in the outside position of the turn it is subjected to increased bending in the coronal plane as compared to the ankle on the inside position of the turn.

[038] Accordingly, as a user rotates the ankle (or other applicable joint) clockwise, engagement members 117 will engage protrusions 143 before engagement members 127 engage protrusions 145. Spring member 110 will therefore provide a first level of rotational stiffness or resistance to the rotation of pyramid adaptor 148 with respect to pyramid adaptor 147 due to the bending of flexible extensions 116. As further clockwise rotation of pyramid adaptor 148 with respect to pyramid adaptor 147 is provided, engagement members 127 will engage protrusions 145, providing a second level of rotational stiffness or resistance to the rotation of pyramid adaptor 148 with respect to pyramid adaptor 147 due to the bending of flexible extensions 126.

[039] Similarly, if prosthetic coupling member 100 is used in a right ankle position, protrusions 145 can be offset to protrusions 143 in a counter-clockwise position (when viewed in the position shown in FIGS. 3 and 4) to provide increased stiffness when the user is turning toward the left and the right ankle is in the outside position during the turn. Accordingly, prosthetic coupling member 100 can be configured to effectively provide different levels of rotational stiffness from spring members 110 and 120. In addition to the offset of protrusions 143 and 145 discussed above, first spring member 110 may be formed of a different material than second spring member 120 to provide different levels of rotational stiffness. In particular embodiments, first and second spring members 110 and/or 120 may be formed from titanium, stainless steel, aluminum or other suitable materials.

[040] In particular embodiments, first spring member 110 may have a different geometry than second spring member 120 (e.g. first spring member 110 may comprise engagement members 117 that are wider or narrower than engagement members 127 so that engagement members 117 engage protrusions 143 at a different angle of rotation than is required for engagement members 127 to engage protrusions 145). Furthermore, prosthetic coupling member 100 may comprise additional spring members that are stacked with spring members 110 and 120 to provide different levels of rotational stiffness. In specific embodiments, first and second spring members 110 and 120 may also be positioned on splines 135 such that engagement members 117 and 127 are not aligned when viewed in a direction parallel to shaft 130 (e.g. as shown in FIGS. 3 and 4). First spring member 110 and second spring member 120 can also be configured to provide a pre-load (e.g. an initial rotation stiffness) between the housing 140 and shaft 130. In particular embodiments, the pre-load can vary to create different initial stiffness levels.

[041] In the specific embodiment shown, there are 12 engagement members 117 and 127 and protrusions 143 and 145, such that there are 30 degrees between the center of each engagement member and protrusion. The width of each engagement member 117 and 127 and protrusion 143 and 145 provides a reduced angle of rotation of substantially circular perimeters 115 and 125 within substantially circular openings 141 and 142 needed for engagement of engagement members 117 and 127 with protrusions 143 and 145. In specific embodiments, a rotation of between 5 and 25 degrees of substantially circular perimeters 115 and 125 within substantially circular openings 141 and 142 is needed for engagement of engagement members 117 and 127 with protrusions 143 and 145.

[042] Accordingly, specific embodiments of the present disclosure include a prosthetic ankle that is passive and provides dual-stiffness automatically without a power source other than the spring members. Such a configuration is in contrast to existing prosthetic ankles that provide dual-stiffness primarily using a power source. In addition, exemplary embodiments are easily scalable and can be pre-loaded, which provides significant benefits to the user. The pre-loading features allows one to change the initial stiffness value are incorporated in a design that is robust, compact and relatively inexpensive to manufacture. Accordingly exemplary embodiments can provide a lower limb amputee user with an ankle that is more compliant in eversion and stiffer in inversion, allowing the user to experience improved balance control and gait mechanics to better emulate non-amputee gait.

[043] All of the devices, systems and/or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the devices, systems and methods of this invention have been described in terms of particular embodiments, it will be apparent to those of skill in the art that variations may be applied to the devices, systems and/or methods in the steps or in the sequence of steps of the method described herein without departing from the concept, spirit and scope of the invention. For example, embodiments can also be used in other applications, including for example, rotated 90 degrees and used in the sagittal plane. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the invention as defined by the appended claims.

REFERENCES:

The contents of the following references are incorporated by reference herein:

[1] Daines, et al. (2021), PloS One.

[2] Miller, W.C. et al. (2001), Arch. Phys. Med. Rehabil.

[3] Neptune, R.R. and McGowan, C.P. (2011), J. Biomech.

[4] Neptune, R.R. and McGowan, C.P. (2011), J. Biomech.

[5] Glaister et al., 2007, Gait Posture.

[6] Segal A.D. et al. (2010), J. Biomech.

[7] Curtze, C. (2012), Gait Posture.

[8] Shell, C.E. (2017), Clinical Biomech.

Azocar, A. F., Mooney, L. M., Duval, J. F., Simon, A. M., Hargrove, L. J., & Rouse, E. J. (2020). Design and clinical implementation of an open-source bionic leg. Nature Biomedical Engineering 4, 1 -13. doi.org/10.1038/s41551 -020-00619-3.

Shell, C.E.; Segal, A.D., Klute, G.K.; Neptune, R.R. (2017). The effects of prosthetic foot stiffness on transtibial amputee walking mechanics and balance control during turning.

Clinical Biomechanics 49: 56-63

U.S. Pat. Pub. 2009/082,878

U.S. Pat. Pub. 2016/151,175

U.S. Pat. Pub. 2018/092,761

U.S. Pat. Pub. 2019/350,729

U.S. Pat. Pub. 2022/062,009

U.S. Patent 6,482,236

U.S. Patent 7,618,464

U.S. Patent 7,794,506

U.S. Patent 10,433,970

U.S. Patent 10,806,602

U.S. Patent 11,324,611

PCT Pat. Pub. WO 2015/027013

PCT Pat. Pub. WO 2018/208714

EP3300699 Al

EP3300699 B1

Claims

1. A prosthetic coupling member comprising: a first spring member comprising a substantially circular perimeter and a plurality of engagement members distributed around the substantially circular perimeter; a second spring member comprising a substantially circular perimeter and a plurality of engagement members distributed around the substantially circular perimeter; and a shaft extending between the first spring member and the second spring member; a housing comprising a substantially circular first opening and a substantially circular second opening, wherein: the first spring member is received within the substantially circular first opening; the second spring member is received within the substantially circular second opening; the shaft comprises a plurality of splines; the substantially circular first opening and the substantially circular second opening each comprise a plurality of protrusions extending inward to engage the spring member; the first spring member and the second spring member each comprise a plurality of flexible members engaged with the plurality of splines; the plurality of engagement members of the first spring member are configured to engage protrusions of the substantially circular first opening upon rotation of the substantially circular perimeter of the first spring member within the substantially circular first opening; and the plurality of engagement members of the second spring member are configured to engage protrusions of the substantially circular second opening upon rotation of the substantially circular perimeter of the second spring member within the substantially circular second opening.

2. The prosthetic coupling member of claim 1 wherein an engagement member of the plurality members of the first spring member is configured to engage adjacent protrusions of the substantially circular first opening upon rotation between 5 and 25 degrees of the substantially circular perimeter of the first spring member within the substantially circular first opening.

3. The prosthetic coupling member of claim 1 or claim 2 wherein an engagement member of the plurality members of the second spring member is configured to engage adjacent protrusions of the substantially circular second opening upon rotation between 5 and 25 degrees of the substantially circular perimeter of the second spring member within the substantially circular second opening.

4. The prosthetic coupling member of any one of claims 1 - 3 wherein the plurality of engagement members of the first spring member are configured to engage adjacent protrusions of the substantially circular first opening upon rotation between 10 and 20 degrees of the substantially circular perimeter of the first spring member within the substantially circular first opening.

5. The prosthetic coupling member of any one of claims 1 - 4 wherein the plurality of engagement members of the second spring member are configured to engage adjacent protrusions of the substantially circular second opening upon rotation between 10 and 20 degrees of the substantially circular perimeter of the second spring member within the substantially circular second opening.

6. The prosthetic coupling member of any one of claims 1 - 5 wherein the plurality of engagement members of the first spring member are configured to engage adjacent protrusions of the substantially circular first opening upon rotation of approximately 15 degrees of the substantially circular perimeter of the first spring member within the substantially circular first opening.

7. The prosthetic coupling member of any one of claims 1 - 6 wherein the plurality of engagement members of the second spring member are configured to engage adjacent protrusions of the substantially circular second opening upon rotation of approximately 15 degrees of the substantially circular perimeter of the second spring member within the substantially circular second opening.

8. The prosthetic coupling member of any one of claims 1 - 7 wherein the housing is a modular housing comprising a first ring member coupled to a second ring member.

9. The prosthetic coupling member of any one of claims 1 - 8 wherein the first or second spring member comprises titanium or steel.

10. The prosthetic coupling member of any one of claims 1 - 9 wherein: the housing comprising a first coupling member and a second coupling member; the first coupling member is configured to couple to a first prosthetic member; and the second coupling member is configured to couple to a second prosthetic member.

11. The prosthetic coupling member of any one of claims 1 - 10 wherein the first prosthetic member is a prosthetic pyramid adaptor and the second prosthetic member is a prosthetic foot.

12. The prosthetic coupling member of any one of claims 1 - 11 wherein: the first spring member has a first rotational stiffness; the second spring member has a second rotational stiffness; and the first rotational stiffness is different than the second rotational stiffness.

13. The prosthetic coupling member of any one of claims 1 - 12 further comprising: a third spring member received within the substantially circular first opening; and a fourth spring member received within the substantially circular second opening.

14. The prosthetic coupling member of claim 13 wherein: the third spring member and the fourth spring member each comprise a plurality of flexible members engaged with the plurality of splines; the plurality of engagement members of the third spring member are configured to engage protrusions of the substantially circular first opening upon rotation of the substantially circular perimeter of the first spring member within the substantially circular first opening; and the plurality of engagement members of the fourth spring member are configured to engage protrusions of the substantially circular second opening upon rotation of the substantially circular perimeter of the second spring member within the substantially circular second opening.

15. The prosthetic coupling member of any one of claims 1 - 14 wherein the prosthetic coupling member does not comprise an electrical, pneumatic or hydraulic power source.

16. The prosthetic coupling member of any one of claims 1 - 15 wherein the first spring member and the second spring member are pre-loaded to exert an initial rotational stiffness between the housing and the shaft.

17. The prosthetic coupling member of any one of claims 1 - 15 wherein the plurality of protrusions of the substantially circular first opening are rotationally offset from the substantially circular second opening.

18. The prosthetic coupling member of claim 17 wherein the plurality of protrusions of the substantially circular first opening are rotationally offset from the substantially circular second opening by between 10-20 degrees.

19. The prosthetic coupling member of claim 17 wherein the plurality of protrusions of the substantially circular first opening are rotationally offset from the substantially circular second opening by approximately 15 degrees.

20. A method of providing varying levels or rotation stiffness in a prosthetic coupling member, the method comprising: providing a plurality of spring members contained within a housing; providing a shaft extending through the plurality of spring members; rotating the housing with respect to the shaft, wherein: a first spring member of the plurality of spring members provides a first level of rotational stiffness upon an initial rotation of the housing with respect to the shaft; and a second spring member of the plurality of spring members provides a second level of rotational stiffness upon further rotation of the housing with respect to the shaft.