U.S. patent application number 11/234159 was filed with the patent office on 2006-02-09 for prosthetic foot with tunable performance.
Invention is credited to Byron Kent Claudino, Barry W. Townsend.
Application Number | 20060030950 11/234159 |
Document ID | / |
Family ID | 56290491 |
Filed Date | 2006-02-09 |
United States Patent
Application |
20060030950 |
Kind Code |
A1 |
Townsend; Barry W. ; et
al. |
February 9, 2006 |
Prosthetic foot with tunable performance
Abstract
A prosthetic foot (190) incorporates a foot keel (192) and a
resilient calf shank (193) with its lower end connected to the foot
keel to form an ankle joint of the prosthetic foot. The calf shank
extends upward from the foot keel by way of an anterior facing
convexly curved portion (195) of the shank, and is secured to the
foot keel by way of a coupling element (194). The lower end of the
shank is reversely curved (196) and housed by a reversely curved
portion of the coupling element. A posterior calf device (191) has
a cable (204) which is untensioned in a normal gait cycle but
tensioned by a force loading on the prosthesis greater than 120% of
body weight of the user to limit, e.g. stop, further anterior
motion of the upper end of the shank.
Inventors: |
Townsend; Barry W.;
(Bakersfield, CA) ; Claudino; Byron Kent;
(Bakersfield, CA) |
Correspondence
Address: |
ANTONELLI, TERRY, STOUT & KRAUS, LLP
1300 NORTH SEVENTEENTH STREET
SUITE 1800
ARLINGTON
VA
22209-3873
US
|
Family ID: |
56290491 |
Appl. No.: |
11/234159 |
Filed: |
September 26, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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PCT/US02/09589 |
Mar 29, 2002 |
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11234159 |
Sep 26, 2005 |
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10473682 |
Sep 30, 2003 |
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11234159 |
Sep 26, 2005 |
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09820895 |
Mar 30, 2001 |
6562075 |
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10473682 |
Sep 30, 2003 |
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PCT/US05/11292 |
Apr 1, 2005 |
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11234159 |
Sep 26, 2005 |
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10814260 |
Apr 1, 2004 |
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11234159 |
Sep 26, 2005 |
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10263795 |
Oct 4, 2002 |
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10814260 |
Apr 1, 2004 |
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09820895 |
Mar 30, 2001 |
6562075 |
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10263795 |
Oct 4, 2002 |
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10814155 |
Apr 1, 2004 |
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11234159 |
Sep 26, 2005 |
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10263795 |
Oct 4, 2002 |
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10814155 |
Apr 1, 2004 |
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09820895 |
Mar 30, 2001 |
6562075 |
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10263795 |
Oct 4, 2002 |
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60558119 |
Apr 1, 2004 |
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Current U.S.
Class: |
623/55 ;
623/50 |
Current CPC
Class: |
A61F 2/76 20130101; A61F
2002/6657 20130101; A61F 2002/5032 20130101; A61F 2/60 20130101;
A61F 2002/5007 20130101; A61F 2002/6664 20130101; A61F 2/66
20130101; A61F 2002/6642 20130101; A61F 2002/5033 20130101; A61F
2220/0041 20130101; A61F 2002/6628 20130101; A61K 9/4816 20130101;
A61F 2002/5083 20130101; A61F 2002/745 20130101; A61F 2002/6614
20130101; A61F 2002/6635 20130101; A61F 2002/5006 20130101; A61F
2002/607 20130101; A61F 2002/30433 20130101; A61F 2002/747
20130101; A61F 2002/5003 20130101; A61F 2002/5079 20130101; A61F
2002/5001 20130101; A61F 2002/6685 20130101; A61F 2002/6621
20130101; A61F 2002/503 20130101; A61F 2002/7615 20130101; A61F
2002/6671 20130101; A61F 2002/6678 20130101; A61F 2002/704
20130101; A61F 2002/5009 20130101; A61F 2220/0075 20130101; A61F
2002/5075 20130101; A61F 2/6607 20130101; A61F 2002/30462 20130101;
A61F 2002/665 20130101 |
Class at
Publication: |
623/055 ;
623/050 |
International
Class: |
A61F 2/66 20060101
A61F002/66 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 1, 2005 |
WO |
PCT/US05/11304 |
Apr 1, 2005 |
WO |
PCT/US05/11291 |
Claims
1. A prosthetic foot comprising: a longitudinally extending foot
keel having forefoot, midfoot and hindfoot portions; a resilient,
upstanding calf shank having a lower end connected to the foot keel
and an upper end to connect with a supporting structure on an
amputee's leg, the upper end being movable longitudinally of the
foot keel in response to force loading and unloading of the calf
shank during use of the prosthetic foot; a device to limit the
anterior, longitudinal motion of the upper end of the calf shank
during use of the prosthetic foot in response to a force loading on
the calf shank greater than that encountered in a normal gait
cycle.
2. The prosthetic foot according to claim 1, wherein said device
limits the anterior, longitudinal motion of the upper end of the
calf shank in response to a force loading greater than 120% of body
weight of the user.
3. The prosthetic foot according to claim 1, wherein said device
includes an elongated member connected with play between the upper
end of the calf shank and a lower portion of the prosthetic foot,
the elongated member being tensioned during use of the prosthetic
foot only when a force loading on the calf shank is greater than
that encountered in a normal gait cycle for limiting said anterior,
longitudinal motion of the upper end of the calf shank.
4. The prosthetic foot according to claim 3, wherein said device
further includes a resilient bumper to absorb shock when the
elongated member is tensioned.
5. The prosthetic foot according to claim 3, wherein said device
further includes an upper block connected to the upper end of the
calf shank, said elongated member being secured to and extending
over a posterior surface of said block.
6. The prosthetic foot according to claim 5, wherein said block has
a guide for said elongated member on said posterior surface.
7. The prosthetic foot according to claim 6, wherein said guide is
a groove in the posterior surface of said block.
8. The prosthetic foot according to claim 3, wherein the upper end
of said elongated member has a connector thereon, said block having
a recess in which said connector is retained to secure said
elongated member to said block.
9. The prosthetic foot according to claim 3, wherein said device
further includes a lower block connected to said prosthetic foot,
the lower end of said elongated member being connected to said
block with play.
10. The prosthetic foot according to claim 9, wherein the lower end
of said elongated member extends longitudinally slidably through an
aperture in the lower block and below the aperture a connector is
provided on said elongated member to prevent withdrawal of the
elongated member from said aperture and said block when said member
is tensioned.
11. The prosthetic foot according to claim 10, wherein the device
further includes a resilient bumper between said connector and said
lower block to absorb shock when the elongated member is
tensioned.
12. The prosthetic foot according to claim 9, wherein said lower
block is pivotably connected to said prosthetic foot.
13. The prosthetic foot according to claim 12, wherein said lower
block is pivotably connected to said prosthetic foot by way of a
backing plate on a coupling element connecting the calf shank to
the foot keel.
14. The prosthetic foot according to claim 3, wherein said
elongated member is a cable.
15. The prosthetic foot according to claim 1, wherein said calf
shank is connected to the foot keel by way of a coupling
element.
16. The prosthetic foot according to claim 1, wherein the lower end
of the calf shank is reversely curved.
17. The prosthetic foot according to claim 16, wherein the
reversely curved lower end is in the form of a spiral.
18. The prosthetic foot according to claim 16, wherein an end of
the reversely curved shank is fastened to a coupling element
connecting the calf shank to the foot keel.
19. The prosthetic foot according to claim 18, wherein the coupling
element has an anterior facing concavity within which the reversely
curved lower end of the calf shank is housed.
20. The prosthetic foot according to claim 18, wherein the coupling
element and at least a portion of the foot keel are monolithically
formed.
21. A system for a lower extremity prosthesis comprising: a
longitudinally extending foot; an ankle; an upstanding shank
extending upward from the ankle; wherein the ankle and shank are
formed by a resilient member having a reversely curved lower end
secured to the foot and extending upward from the foot by way of an
anterior facing convexly curved portion of the member, and wherein
a device is provided to limit the anterior, longitudinal motion of
the upper end of the resilient member during use of the prosthesis
in response to a force loading on the resilient member greater than
that encountered in a normal gait cycle.
22. The system according to claim 22, wherein said device limits
the anterior, longitudinal motion of the upper end of the resilient
member only when a force loading on the prosthesis is greater than
120% of body weight of the user.
Description
RELATED APPLICATIONS
[0001] This application claims priority of International
Applications Nos. PCT/US05/011304 and PCT/US05/11291, each filed
Apr. 1, 2005 and designating the U.S.
[0002] This application is a continuation in part application of
each of the following applications: [0003] (1) International
Application No. PCT/US02/09589 filed Mar. 29, 2002 and designating
the U.S. and the related U.S. national stage application Ser. No.
10/473,682 filed Sep. 30, 2003, which is a continuation in part of
U.S. application Ser. No. 09/820,895 filed Mar. 30, 2001, now U.S.
Pat. No. 6,562,075 issued May 13, 2003. [0004] (2) International
Application No. PCT/US05/011902 filed Apr. 1, 2005 and claiming
priority of U.S. Application No. 60/558,119 filed Apr. 1, 2004.
[0005] (3) U.S. application Ser. No. 10/814,260 filed Apr. 1, 2004
which is a continuation in part of U.S. application Ser. No.
10/263,795 filed Oct. 2, 2002, which is a continuation of U.S.
application Ser. No. 09/820,895 filed Mar. 30, 2001, now U.S. Pat.
No. 6,562,075 issued May 13, 2003. [0006] (4) U.S. application Ser.
No. 10/814,155 filed Apr. 1, 2004 which is a continuation in part
of U.S. application Ser. No. 10/263,795 filed Oct. 4, 2002, which
is a continuation of U.S. application Ser. No. 09/820,895 filed
Mar. 30, 2001, now U.S. Pat. No. 6,562,075 issued May 13, 2003.
TECHNICAL FIELD
[0007] The present invention relates to a high performance
prosthetic foot providing improved dynamic response capabilities as
these capabilities relate to applied force mechanics.
BACKGROUND ART
[0008] A jointless artificial foot for a leg prosthesis is
disclosed by Martin et al. in U.S. Pat. No. 5,897,594. Unlike
earlier solutions wherein the artificial foot has a rigid
construction provided with a joint in order to imitate the function
of the ankle, the jointless artificial foot of Martin et al.
employs a resilient foot insert which is arranged inside a foot
molding. The insert is of approximately C-shaped design in
longitudinal section, with the opening to the rear, and takes up
the prosthesis load with its upper C-limb and via its lower C-limb
transmits that load to a leaf spring connected thereto. The leaf
spring as seen from the underside is of convex design and extends
approximately parallel to the sole region, forward beyond the foot
insert into the foot-tip region. The Martin et al. invention is
based on the object of improving the jointless artificial foot with
regard to damping the impact of the heel, the elasticity, the
heel-to-toe walking and the lateral stability, in order thus to
permit the wearer to walk in a natural manner, the intention being
to allow the wearer both to walk normally and also to carry out
physical exercise and to play sports. However, the dynamic response
characteristics of this known artificial foot are limited and do
not mimic the human biomechanical function of the human foot, ankle
and shank and soft supporting tissue. The artificial foot of Martin
et al. and other prior art prosthetic feet that utilize this ankle
design and a rigid pylon as a shank cannot store enough elastic
energy to create normal ankle joint sagittal plane kinetic power in
gait. Tests have shown that prior art prosthetic feet with such
designs produce only about 25% of normal ankle joint sagittal plane
kinetic power in gait.
[0009] Other prosthetic feet have been proposed by Van L. Phillips
which allegedly provide an amputee with an agility and mobility to
engage in a wide variety of activities which were precluded in the
past because of the structural limitations and corresponding
performances of prior art prostheses. Running, jumping and other
activities are allegedly sustained by these known feet which,
reportedly, may be utilized in the same manner as the normal foot
of the wearer. See U.S. Pat. Nos. 6,071,313; 5,993,488; 5,899,944;
5,800,569; 5,800,568; 5,728,177; 5,728,176; 5,824,112; 5,593,457
5,514,185; 5,181,932; and 4,822,363, for example. These prostheses
have a foot, ankle and shank made of composite material with the
mechanical form of the ankle being posterior facing,
convexly-curved. Tests have shown that prior art prostheses with
this design produce approximately 40% of normal human ankle joint
sagittal plane kinetic power in gait. There is a need for a higher
performance prosthesis which can improve amputee performance in
activities such as walking, running, jumping, sprinting, starting,
stopping and cutting.
DISCLOSURE OF INVENTION
[0010] In order to allow the amputee to attain a higher level of
performance and function, there is a need for a high performance
prosthetic foot having improved applied mechanics, which foot can
out perform the human foot and also out perform the prior art
prosthetic feet. It is of interest to the amputee to have a high
performance prosthetic foot having improved applied mechanics, high
low dynamic response, and alignment adjustability that can be fine
tuned to improve the horizontal and vertical components of
activities which can be task specific in nature.
[0011] The prosthetic foot of the present invention addresses these
needs. According to an example embodiment disclosed herein, the
prosthetic foot of the invention comprises a longitudinally
extending foot keel having a forefoot portion at one end, a
hindfoot portion at an opposite end and a relatively long midfoot
portion extending between and upwardly arched from the forefoot and
hindfoot portions. A calf shank including a downward convexly
curved lower end is also provided. An adjustable fastening
arrangement attaches the curved lower end of the calf shank to the
upwardly arched midfoot portion of the foot keel to form an ankle
joint area of the prosthetic foot. The calf shank is a resilient
member which forms an ankle and a shank of the prosthesis, the
resilient member extending upward from the foot keel by way of an
anterior facing convexly curved portion of the member.
Advantageously, with this mechanical form orientation, the
mechanical form's angular velocity increases in response to
compressing force in late mid-stance loading. As a consequence,
ankle joint sagittal plane kinetic power of the prosthesis in gait
is improved.
[0012] The adjustable fastening arrangement permits adjustment of
the alignment of the calf shank and the foot keel with respect to
one another in the longitudinal direction of the foot keel for
tuning the performance of the prosthetic foot. By adjusting the
alignment of the opposed upwardly arched midfoot portion of the
foot keel and the downward convexly curved lower end of the calf
shank with respect to one another in the longitudinal direction of
the foot keel, the dynamic response characteristics and motion
outcomes of the foot are changed to be task specific in relation to
the needed/desired horizontal and vertical linear velocities. A
multi-use prosthetic foot is disclosed having high and low dynamic
response capabilities, as well as biplanar motion characteristics,
which improve the functional outcomes of amputees participating in
activities of daily living, sporting and/or recreational
activities. A prosthetic foot especially for sprinting is also
disclosed.
[0013] The calf shank in several embodiments has its lower end
reversely curved in the form of a spiral with the calf shank
extending upward anteriorly from the spiral to an upstanding upper
end thereof. This creates a calf shank with an integrated ankle at
the lower end thereof, when the calf shank is secured to the foot
keel, with a variable radii response outcome similar to a
parabola-shaped calf shank of the invention. The calf shank with
spiral lower end is secured to the foot keel by way of a coupling
element. The coupling element can include a stop to limit
dorsiflexion of the calf shank in gait. In several embodiments the
coupling element is monolithically formed with the forefoot portion
of the foot keel. According to another feature of the invention the
coupling element extends posteriorly as a cantilever over the
midfoot portion and part of the hindfoot portion of the foot keel.
The coupling element can be reversely curved upwardly to form an
anterior facing concavity in which the lower end of the calf shank
is housed, the reversely curved lower end of the calf shank being
supported at its end from the coupling element. The resulting
prosthesis has improved efficiency.
[0014] The prosthesis according to a further feature of the
invention can include a posterior calf device to store additional
energy with anterior motion of the upper end of the calf shank
and/or to limit the anterior motion of the upper end of the calf
shank. In one embodiment, the device includes an elongated member
in the form of a cable which is connected with play between the
upper end of the calf shank and the lower portion of the prosthesis
with the cable being tensioned only when a force loading on the
calf shank is greater than that encountered in a normal gait cycle,
preferably only when the force loading is greater than 120% of body
weight of the user. A resilient bumper in the device absorbs shock
and stores energy when the cable is tensioned as, for example, by
higher level activity, e.g., running, jumping, etc., by the
user.
[0015] These and other features and advantages of the present
invention become more apparent from a consideration of the
following detailed description of disclosed example embodiments of
the invention and the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a schematic illustration representing the two
adjacent radii of curvatures R.sub.1 and R.sub.2, one against the
other, of a foot keel and calf shank of a prosthetic foot of the
invention which creates a dynamic response capability and motion
outcome of the foot in gait in the direction of arrow B which is
perpendicular to the tangential line A connecting the two
radii.
[0017] FIG. 2 is a view similar to FIG. 1 but showing the alignment
of the two radii having been changed in the prosthetic foot
according to the invention to increase the horizontal component and
decrease the vertical component of the dynamic response capability
and motion outcome of the foot in gait so that arrow B.sub.1,
perpendicular to tangential line A.sub.1, is more horizontally
directed than is the case depicted in FIG. 1.
[0018] FIG. 3 is a side view of a prosthetic foot according to an
example embodiment of the invention with pylon adapter and pylon
connected thereto for securing the foot to the lower leg of an
amputee.
[0019] FIG. 4 is a front view of the prosthetic foot with pylon
adapter and pylon of FIG. 3.
[0020] FIG. 5 is a top view of the embodiment of FIGS. 3 and 4.
[0021] FIG. 6 is a side view of another foot keel of the invention,
especially for sprinting, which may be used in the prosthetic foot
of the invention.
[0022] FIG. 7 is a top view of the foot keel of FIG. 6.
[0023] FIG. 8 is a bottom view of the foot keel in the prosthetic
foot in FIG. 3 which. provides high low dynamic response
characteristics as well as biplanar motion capabilities.
[0024] FIG. 9 is a side view of an additional foot keel of the
invention for the prosthetic foot particularly useful for sprinting
by an amputee that has had a Symes amputation of the foot.
[0025] FIG. 10 is a top view of the foot keel of FIG. 9.
[0026] FIG. 11 is a further variation of foot keel for the
prosthetic foot of the invention for a Symes amputee, the foot keel
providing the prosthetic foot with high low dynamic response
characteristics as well as biplanar motion capabilities.
[0027] FIG. 12 is a top view of the foot keel of FIG. 11.
[0028] FIG. 13 is a side view of a foot keel of the invention
wherein the thickness of the keel tapers, e.g., is progressively
reduced, from the midfoot portion to the hindfoot portion of the
keel.
[0029] FIG. 14 is a side view of another form of the foot keel
wherein the thickness tapers from the midfoot toward both the
forefoot and hindfoot of the keel.
[0030] FIG. 15 is a side view from slightly above and to the front
of a parabola shaped calf shank of the prosthetic foot of the
invention, the thickness of the calf shank tapering toward its
upper end.
[0031] FIG. 16 is a side view like FIG. 15 but showing another calf
shank tapered from the middle towards both its upper and lower
ends.
[0032] FIG. 17 is a side view of a C-shaped calf shank for the
prosthetic foot, the calf shank thickness tapering from the middle
towards both its upper and lower ends.
[0033] FIG. 18, is a side view of another example of a C-shaped
calf shank for the prosthetic foot, the thickness of the calf shank
being progressively reduced from its midportion to its upper
end.
[0034] FIG. 19 is a side view of an S-shaped calf shank for the
prosthetic foot, both ends being progressively reduced in thickness
from the middle thereof.
[0035] FIG. 20 is a further example of an S-shaped calf shank which
is tapered in thickness only at its upper end.
[0036] FIG. 21 is a side view of a J-shaped calf shank, tapered at
each end, for the prosthetic foot of the invention.
[0037] FIG. 22 is a view like FIG. 21 but showing a J-shaped calf
shank which is progressively reduced in thickness towards only its
upper end.
[0038] FIG. 23 is a side view, from slightly above, of a metal
alloy or plastic coupling element used in the adjustable fastening
arrangement of the invention for attaching the calf shank to the
foot keel as shown in FIG. 3.
[0039] FIG. 24 is a view from the side and slightly to the front of
a pylon adapter used on the prosthetic foot of FIGS. 3-5, and also
useful with the foot of FIGS. 28 and 29, for connecting the foot to
a pylon to be attached to an amputee's leg.
[0040] FIG. 25 is a side view of another prosthetic foot of the
invention similar to that in FIG. 3, but showing use of a coupling
element with two releasable fasteners spaced longitudinally
connecting the element to the calf shank and foot keel,
respectively.
[0041] FIG. 26 is an enlarged side view of the coupling element in
FIG. 25.
[0042] FIG. 27 is an enlarged side view of the calf shank of the
prosthetic foot of FIG. 25.
[0043] FIG. 28 is a side view of another embodiment of the
prosthetic foot wherein the calf shank is utilized within a
cosmetic covering.
[0044] FIG. 29 is a top view of the prosthetic foot in FIG. 28.
[0045] FIG. 30 is a cross-sectional view of the prosthetic foot of
FIGS. 28 and 29 taken along the line 30-30 in FIG. 29.
[0046] FIGS. 31A and 31B are sectional views of wedges of different
thicknesses which may be used in the dorsiflexion stop of the
coupling element as shown in FIG. 30.
[0047] FIG. 32 is a side view of a further embodiment of the
prosthetic foot wherein the lower end of the calf shank is
reversely curved in the form of a spiral and housed within and
supported by a coupling element monolithically formed with the
forefoot portion of the foot keel.
[0048] FIG. 33 is a front view of the prosthesis of FIG. 32.
[0049] FIG. 34 is a rear view of the prosthesis of FIG. 32.
[0050] FIG. 35 is a side view of another embodiment of the
prosthesis wherein a posterior component of the foot keel is joined
to the reversely curved upper end of the coupling element which is
monolithically formed with the forefoot portion of the foot
keel.
[0051] FIG. 36 is a side view of another form of the invention
wherein the coupling element is monolithically formed with the foot
keel.
[0052] FIG. 37 is a side view of a still further variation of the
prosthesis of the invention wherein the coupling element is joined
at a posterior end thereof to the foot keel by a fastener.
[0053] FIG. 38 is a side view of another embodiment of the
prosthesis showing the coupling element joined to the foot keel at
the posterior end of the foot keel.
[0054] FIG. 39 is a side view of the calf shank and posterior calf
device of the embodiments of FIGS. 35-38 shown disassembled from
the foot keel and its coupling element.
[0055] FIG. 40 is a perspective from the left side and to the rear
of a prosthetic foot of an additional embodiment of the invention
combining features of several other embodiments.
[0056] FIG. 41 is a side view of another embodiment of the
prosthetic foot of the invention with posterior calf device.
[0057] FIG. 42 is a rear view of the prosthetic foot, taken from
the right side of the prosthesis shown in FIG. 41.
[0058] FIG. 43 is a perspective from the left side and to the rear
of the prosthetic foot in FIG. 41 with several parts thereof shown
disassembled.
[0059] FIG. 44 is a cross sectional view along the longitudinal
center line of a lower cable block of the posterior calf device
depicting the lower end of the cable of the device extending
longitudinally slidably through an aperture of the block and
retained therein by a connector swaged on the lower end of the
cable with a resilient bumper being provide on the cable between
the connector and the block.
BEST MODE FOR CARRYING OUT THE INVENTION
[0060] Referring now to the drawings, a prosthetic foot 1 in the
example embodiment of FIGS. 3-5 is seen to comprise a
longitudinally extending foot keel 2 having a forefoot portion 3 at
one end, a hindfoot portion 4 at an opposite end and an upwardly
arched midfoot portion 5 extending between the forefoot and
hindfoot portions. The midfoot portion 5 is upward convexly curved
over its entire longitudinal extent between the forefoot and
hindfoot portions in the example embodiment.
[0061] An upstanding calf shank 6 of the foot 1 is attached at a
portion of a downward convexly curved lower end 7 thereof to a
proximate, posterior surface of the keel midfoot portion 5 by way
of a releasable fastener 8 and coupling element 11. The fastener 8
is a single bolt with nut and washers in the example embodiment,
but could be a releasable clamp or other fastener for securely
positioning and retaining the calf shank on the foot keel when the
fastener is tightened.
[0062] A longitudinally extending opening 9 is formed in a
proximate, posterior surface of the keel midfoot portion 5, see
FIG. 8. A longitudinally extending opening 10 is also formed in the
curved lower end 7 of the calf shank 6 like that shown in FIG. 15,
for example. The releasable fastener 8 extends through the openings
9 and 10 which permit adjusting the alignment of the calf shank and
the foot keel with respect to one another in the longitudinal
direction, A-A in FIG. 5, when the fastener 8 is loosened or
released for tuning the performance of the prosthetic foot to be
task specific. Thus, the fastener 8, coupling element 11 and
longitudinally extending openings 9 and 10 constitute an adjustable
fastening arrangement for attaching the calf shank to the foot keel
to form an ankle joint area of the prosthetic foot.
[0063] The effects of adjusting the alignment of the calf shank 6
and foot keel 2 are seen from a consideration of FIGS. 1 and 2,
wherein the two radii R.sub.1 and R.sub.2, one next to another,
represent the adjacent, facing, domed or convexly curved surfaces
of the foot keel midportion 5 and the calf shank 6. When two such
radii are considered one next to another, motion capability exists
perpendicular to a tangential line, A in FIG. 1, A.sub.1 in FIG. 2,
drawn between the two radii. The interrelationship between these
two radii determines a direction of motion outcomes. As a
consequence, dynamic response force application of the foot 1 is
dependent on this relationship. The larger the radius of a
concavity, the more dynamic response capability. However, the
tighter a radius, the quicker it responds.
[0064] The alignment capability of the calf shank and foot keel in
the prosthetic foot of the invention allows the radii to be shifted
so that horizontal or vertical linear velocities with the foot in
athletic activities are affected. For example, to improve the
horizontal linear velocity capability of the prosthetic foot 1, an
alignment change can be made to affect the relationship of the calf
shank's radius and the foot keel radius. That is, to improve the
horizontal linear velocity characteristic, the bottom radius
R.sub.2, of the foot keel, is made more distal than its start
position, FIG. 2 as compared with FIG. 1. This changes the dynamic
response characteristics and motion outcomes of the foot 1 to be
more horizontally directed and as a result greater horizontal
linear velocity can be achieved with the same applied forces.
[0065] The amputee can, through practice, find a setting for each
activity that meets his/her needs as these needs relate to
horizontal and vertical linear velocities. A jumper and a
basketball player, for example, need more vertical lift than a
sprint runner. The coupling element 11 is a plastic or metal alloy
alignment coupling (see FIGS. 3, 4 and 23) sandwiched between the
attached foot keel 2 and calf shank 6. The releasable fastener 8
extends through a hole 12 in the coupling element. The coupling
element extends along the attached portion of the calf shank and
the proximate, posterior surface of the keel midfoot portion 5.
[0066] The curved lower end 7 of the calf shank 6 is in the shape
of a parabola with the smallest radius of curvature of the parabola
located at the lower end and extending upwardly, and initially
anteriorly in the parabola shape. A posteriorly facing concavity is
formed by the curvature of the calf shank as depicted in FIG. 3.
The parabola shape is advantageous in that it has increased dynamic
response characteristics in creating both improved horizontal
linear velocity associated with the relatively larger radii
proximal terminal end thereof, while having a smaller radius of
curvature at its lower end for quicker response characteristics.
The larger radii of curvature at the upper end of the parabola
shape enable the tangential line A, explained with reference to
FIGS. 1 and 2, to remain more horizontally oriented with changes in
alignment, which creates improved horizontal linear velocity.
[0067] The parabolic shaped calf shank responds to initial contact
ground forces in human gait by compressing or coiling in on itself.
This makes the radii of the parabola curve smaller, and as a
consequence, the resistance to compression is decreased. In
contrast, as the parabolic shaped calf shank responds to heel off
ground reaction forces (GRFs) in human gait by expanding, this
makes the radii of the parabola curve larger and as a consequence
resistance is much greater than the aforementioned compressive
resistance. These resistances are associated with the human's
anterior and posterior calf muscle function in human gait. At
initial contact to foot flat of human gait, the smaller anterior
calf muscle group responds to GRFs by eccentrically contracting to
lower the foot to the ground and a dorsiflexion moment is created.
From foot flat to toe off the larger posterior calf muscle group
responds to GRFs also by eccentrically contracting and a greater
plantar flexion moment is created. This moment size relates to the
calf anterior and posterior muscle group difference in size. As a
consequence, the prosthetic calf shank's resistance to the
dorsiflexion and plantar flexion moments in human gait are mimicked
and normal gait is achieved. The parabolic curves variable
resistance capability mimics the human calf musculature function in
human gait and running and jumping activities, and as a consequence
prosthetic efficiency is achieved. Tests have shown that a
prosthetic foot according to the invention produced 86% of
non-pathological human ankle joint kinetic power generation, more
than twice that obtained in tests of a conventional prosthetic foot
of the aforementioned type having a posterior facing,
convexly-curved ankle and shank. It is believed that at least one
factor in this dramatic improvement in sagittal plane kinetic power
generated by the prosthesis of the invention is that with the
invention's anterior convexly curved resilient ankle and integral
resilient shank, angular velocity is increased in response to
compressing force in late mid-stance loading whereas in the prior
art prosthesis angular velocity is decreased in response to such
loading. This improvement with the present invention lowers the
energy expenditure by a user for walking, increases walking speed
and allows a more normal gait.
[0068] A human being walks at approximately three miles per hour. A
4:00 minute miler runs at 12 miles per hour and a 10 second, 100
meter sprinter sprints at 21 miles per hour. This is a 1 to 4 to 7
ratio. The horizontal component of each task is greater as the
velocity of the activity increases. As a consequence, the size of
the prosthetic calf shank radii can be predetermined. A walker
needs a smaller radii parabolic curved calf shank than a miler and
a sprinter. A sprint runner needs a parabolic curved calf shank
that is seven times as large. This relationship shows how to
determine the parabolic radii for walkers, runners and sprinters.
It is of significance because sprint runners have increased range
of motion requirements and their calf shanks must be stronger to
accept the increased loads associated with this activity. A wider
or larger parabolic calf shank will be a relatively flatter curve,
which equates to greater structural strength with increased range
of motion.
[0069] A pylon adapter 13 is connected to the upper end of the calf
shank 6 by fasteners 14. The adapter 13 in turn is secured to the
lower end of pylon 15 by fasteners 16. Pylon 15 is secured to the
lower limb of the amputee by a supporting structure (not shown)
attached to the leg stump.
[0070] The forefoot, midfoot and hindfoot portions of the foot keel
2 are formed of a single piece of resilient material in the example
embodiment. For example, a solid piece of material, plastic in
nature, having shape-retaining characteristics when deflected by
the ground reaction forces can be employed. More particularly, the
foot keel and also the calf shank can be formed of laminated
composite material having reinforcing fiber laminated with polymer
matrix material. In particular, a high strength graphite, laminated
with epoxy thermosetting resins, or extruded plastic utilized under
the tradename of Delran, or degassed polyurethane copolymers, may
be used to form the foot keel and also the calf shank. The
functional qualities associated with these materials afford high
strength with low weight and minimal creep. The thermosetting epoxy
resins are laminated under vacuum utilizing prosthetic industry
standards. The polyurethane copolymers can be poured into negative
molds and the extruded plastic can be machined. Each material of
use has its advantages and disadvantages. It has been found that
the laminated composite material for the foot keel and the calf
shank can also advantageously be a thermo-formed (prepreg)
laminated composite material manufactured per industry standards,
with reinforcing fiber and a thermoplastic polymer matrix material
for superior mechanical expansion qualities. A suitable
commercially available composite material of this kind is
CYLON.RTM. made by Cytec Fiberite Inc. of Havre de Grace, Md.
Alternatively, the foot keel and calf shank in this and the other
embodiments disclosed herein can be made of resilient metal alloy,
for example, of grade 5 titanium alloy which has been solution heat
treated and over aged (STOA) and shot peened with specifications
that increase the fatigue life through the addition of compressive
stresses on the surface.
[0071] The resilient material's physical properties as they relate
to stiffness, flexibility and strength are all determined by the
thickness of the material. A thinner material will deflect easier
than a thicker material of the same density. The material utilized,
as well as the physical properties, are associated with the
stiffness to flexibility characteristics in the prosthetic foot
keel and calf shank. The thickness of the foot keel and calf shank
are uniform or symmetrical in the example embodiment of FIGS. 3-5,
but the thickness along the length of these components can be
varied as discussed below, such as by making the hindfoot and
forefoot areas thinner and more responsive to deflection in the
midfoot region.
[0072] To aid in providing the prosthetic foot 1 with a high low
dynamic response capability, the midfoot portion 5 is formed by a
longitudinal arch such that the medial aspect of the longitudinal
arch has a relatively higher dynamic response capability than the
lateral aspect of the longitudinal arch. For this purpose, in the
example embodiment, the medial aspect of the longitudinal arch
concavity is larger in radius than the lateral aspect thereof.
[0073] The interrelationship between the medial to lateral radii
size of the longitudinal arch concavity of the midfoot portion 5 is
further defined as the anterior posterior plantar surface weight
bearing surface areas of the foot keel 2. The line T.sub.1-T.sub.2
on the anterior section of 5 in FIG. 8 represents the anterior
plantar surface weight bearing area. Line P.sub.1--P.sub.2
represents the posterior plantar weight-bearing surface of 5. The
plantar weight bearing surfaces on the lateral side of the foot
would be represented by the distance between T.sub.1-P.sub.1. The
plantar weight bearing surfaces on the medial side of the foot 2
are represented by the distance between P.sub.2-T.sub.2. The
distances represented by T.sub.1-P.sub.1 and P.sub.2-T.sub.2
determine the radii size, and as a result the high low dynamic
response interrelationship is determined and can be influenced by
converging or diverging these two lines T.sub.1-T.sub.2 to
P.sub.1-P.sub.2. As a result, high low dynamic response can be
determined in structural design.
[0074] The posterior end 17 of the hindfoot portion 4 is shaped in
an upwardly curved arch that reacts to ground reaction forces
during heel strike by compressing for shock absorption. The heel
formed by the hindfoot portion 4 is formed with a posterior lateral
corner 18 which is more posterior and lateral than the medial
corner 19 to encourage hindfoot eversion during initial contact
phase of gait. The anterior end 20 of the forefoot portion 3 is
shaped in an upwardly curved arch to simulate the human toes being
dorsiflexed in the heel rise toe off position of the late stance
phase of gait. Rubber or foam pads 53 and 54 are provided on the
lower forefoot and hindfoot as cushions.
[0075] Improved biplanar motion capability of the prosthetic foot
is created by medial and lateral expansion joint holes 21 and 22
extending through the forefoot portion 3 between dorsal and plantar
surfaces thereof. Expansion joints 23 and 24 extend forward from
respect ones of the holes to the anterior edge of the forefoot
portion to form medial, middle and lateral expansion struts 25-27
which create improved biplanar motion capability of the forefoot
portion of the foot keel. The expansion joint holes 21 and 22 are
located along a line, B-B in FIG. 5, in the transverse plane which
extends at an angle .alpha. of 35.degree. to the longitudinal axis
A-A of the foot keel with the medial expansion joint hole 21 more
anterior than the lateral expansion joint hole 22.
[0076] The angle .alpha. of line B-B to longitudinal axis A-A in
FIG. 5 can be as small as 15.degree. and still derive a high low
dynamic response. As this angle .alpha. changes, so should the
angle Z of the line T.sub.1-T.sub.2 in FIG. 8. The expansion joint
holes 21 and 22 as projected on a sagittal plane are inclined at an
angle of 45.degree. to the transverse plane with the dorsal aspect
of the holes being more anterior than the plantar aspect. With this
arrangement, the distance from the releasable fastener 8 to the
lateral expansion joint hole 22 is shorter than the distance from
the releasable fastener to the medial expansion joint hole 21 such
that the lateral portion of the prosthetic foot 1 has a shorter toe
lever than the medial for enabling midfoot high and low dynamic
response. In addition, the distance from the releasable fastener 8
to the lateral plantar weight bearing surface as represented by
T.sub.1, line is shorter than the distance from the releasable
fastener to the medial plantar surface weight bearing surface as
represented by the line T.sub.2--such that the lateral portion of
the prosthetic foot 1 has a shorter toe lever than the medial for
enabling midfoot high low dynamic response.
[0077] The anterior of the hindfoot portion 4 of the foot keel 2
further includes an expansion joint hole 28 extending through the
hindfoot portion 4 between dorsal and plantar surfaces thereof. An
expansion joint 29 extends posteriorly from the hole 28 to the
posterior edge of the hindfoot portion to form expansion struts 30
and 31. These create improved biplanar motion capability of the
hindfoot portion of the foot.
[0078] A dorsal aspect of the midfoot portion 5 and the forefoot
portion 3 of the foot keel 2 form the upwardly facing concavity, 32
in FIG. 3, so that it mimics in function the fifth ray axis of
motion of a human foot. That is, the concavity 32 has a
longitudinal axis C-C which is oriented at an angle .beta. of
15.degree. to 35.degree. to the longitudinal axis A-A of the foot
keel with the medial being more anterior than the lateral to
encourage fifth ray motion in gait as in the oblique low gear axis
of rotation of the second to fifth metatarsals in the human
foot.
[0079] The importance of biplanar motion capability can be
appreciated when an amputee walks on uneven terrain or when the
athlete cuts medially or laterally on the foot. The direction of
the ground force vector changes from being sagittally oriented to
having a frontal plane component. The ground will push medially in
opposite direction to the foot pushing laterally. As a consequence
to this, the calf shank leans medially and weight is applied to the
medial structure of the foot keel. In response to these pressures,
the medial expansion joint struts 25 and 31 of the foot keel 2
dorsiflex (deflect upward) and invert, and the lateral expansion
joint struts 27 and 30 plantar flex (deflect downwards) and evert.
This motion tries to put the plantar surface of the foot flat on
the ground (plantar grade).
[0080] Another foot keel 33 of the invention, especially for
sprinting, may be used in the prosthetic foot of the invention, see
FIGS. 6 and 7. The body's center of gravity in a sprint becomes
almost exclusively sagittal plane oriented. The prosthetic foot
does not need to have a low dynamic response characteristic. As a
consequence, the 15.degree. to 35.degree. external rotation
orientation of the longitudinal axis of the forefoot, midfoot
concavity as in foot keel 2 is not needed. Rather, the concavity's
longitudinal axis D-D orientation should become parallel to the
frontal plane as depicted in FIGS. 6 and 7. This makes the sprint
foot respond in a sagittal direction only. Further, the orientation
of the expansion joint holes 34 and 35 in the forefoot and midfoot
portions, along line E-E, is parallel to the frontal plane, i.e.,
the lateral hole 35 is moved anteriorly and in line with the medial
hole 34 and parallel to the frontal plane. The anterior terminal
end 36 of the foot keel 33 is also made parallel to the frontal
plane. The posterior terminal heel area 37 of the foot keel is also
parallel to the frontal plane. These modifications effect in a
negative way the multi-use capabilities of the prosthetic foot.
However, its performance characteristics become task specific.
Another variation in the sprint foot keel 33 is in the toe, ray
region of the forefoot portion of the foot where 15.degree. of
dorsiflexion in the foot keel 2 are increased to 25-40.degree. of
dorsiflexion in foot keel 33.
[0081] FIGS. 9 and 10 show an additional foot keel 38 of the
invention for the prosthetic foot particularly useful for sprinting
by an amputee that has had a Symes amputation of the foot. For this
purpose, the midfoot portion of the foot keel 38 includes a
posterior, upwardly facing concavity 39 in which the curved lower
end of the calf shank is attached to the foot keel by way of the
releasable fastener. This foot keel can be utilized by all lower
extremity amputees. The foot keel 38 accommodates the longer
residual limb associated with the Symes level amputee. Its
performance characteristics are distinctively quicker in dynamic
response capabilities. Its use is not specific to this level of
amputation. It can be utilized on all transtibial and transfemoral
amputations. The foot keel 40 in the example embodiment of FIGS. 11
and 12 also has a concavity 41 for a Symes amputee, the foot keel
providing the prosthetic foot with high low dynamic response
characteristic as well as biplanar motion capabilities like those
of the example embodiment in FIGS. 3-5 and 8.
[0082] The functional characteristics of the several foot keels for
the prosthetic foot 1 are associated with the shape and design
features as they relate to concavities, convexities, radii size,
expansion, compression, and material physical properties--all of
these properties relating, to reacting to, ground forces in
walking, running and jumping activities.
[0083] The foot keel 42 in FIG. 13 is like that in the example
embodiment of FIGS. 3-5 and 8, except that the thickness of the
foot keel is tapered from the midfoot portion to the posterior of
the hindfoot. The foot keel 43 in FIG. 14 has its thickness
progressively reduced or tapered at both its anterior and posterior
ends. Similar variations in thickness are shown in the calf shank
44 of FIG. 15 and the calf shank 45 of FIG. 16 which may be used in
the prosthetic foot 1. Each design of the foot keel and calf shank
create different functional outcomes, as these function outcomes
relate to the horizontal and vertical linear velocities which are
specific to improving performance in varied athletic related tasks.
The capability of multiple calf shank configurations and
adjustments in settings between the foot keel and the calf shank
create a prosthetic foot calf shank relationship that allows the
amputee and/or the prosthetist the ability to tune the prosthetic
foot for maximum performance in a selected one of a wide variety of
walking and recreational activities.
[0084] Other calf shanks for the prosthetic foot 1 are illustrated
in FIGS. 17-22 and include C-shaped calf shanks 46 and 47, S-shaped
calf shanks 48 and 49 and modified J-shaped calf shanks 50 and 51.
The upper end of the calf shank could also have a straight vertical
end with a pyramid attachment plate attached to this proximal
terminal end. A male pyramid could be bolted to and through this
vertical end of the calf shank. Plastic or aluminum fillers to
accept the proximal male pyramid and the distal foot keel could
also be provided in the elongated openings at the proximal and
distal ends of the calf shank. The prosthetic foot of the invention
is a modular system preferably constructed with standardized units
or dimensions for flexibility and variety in use.
[0085] All track related running activities take place in a
counter-clockwise direction. Another, optional feature of the
invention takes into account the forces acting on the foot advanced
along such a curved path. Centripetal acceleration acts toward the
center of rotation where an object moves along a curved path.
Newton's third law is applied for energy action. There is an equal
and opposite reaction. Thus, for every "center seeking" force,
there is a "center fleeing" force. The centripetal force acts
toward the center of rotation and the centrifugal force, the
reaction force, acts away from the center of rotation. If an
athlete is running around the curve on the track, the centripetal
force pulls the runner toward the center of the curve while the
centrifugal force pulls away from the center of the curve. To
counteract the centrifugal force which tries to lean the runner
outward, the runner leans inward. If the direction of rotation of
the runner on the track is always counter-clockwise, then the left
side is the inside of the track. As a consequence, according to a
feature of the present invention, the left side of the right and
left prosthetic foot calf shanks can be made thinner than the right
side and the amputee runner's curve performance could be
improved.
[0086] The foot keels 2, 33, 38, 42 and 43 in the several
embodiments, are each 29 cm long with the proportions of the shoe 1
shown to scale in FIGS. 3, 4 and 5, and in the several views of the
different calf shanks and foot keels. However, as will be readily
understood by the skilled artisan, the specific dimensions of the
prosthetic foot can be varied depending on the size, weight and
other characteristics of the amputee being fitted with the foot.
The human foot, ankle, shank and soft supporting tissues are loaded
with kinetic energy during the stance phase of the gait and running
cycle. A prosthetic calf shank that is longer in length has more
elastic energy storage capacity. As a consequence, more ankle joint
kinetic power is utilized to do the work of walking, running and
jumping. Therefore, the prosthetic calf shank can be attached to
the most proximal regions of the amputee's residual limb socket;
for example, to the tibia tubercle height.
[0087] The operation of the prosthetic foot 1 in walking and
running stance phase gait cycles will now be considered. Newton's
three laws of motion, that relate to law of inertia, acceleration
and action-reaction, are the basis for movement kinematics in the
foot 2. From Newton's third law, the law of action-reaction, it is
known that the ground pushes on the foot in a direction equal and
opposite to the direction the foot pushes on the ground. These are
known as ground reaction forces. Many scientific studies have been
done on human gait, running and jumping activities. Force plate
studies show us that Newton's third law occurs in gait. From these
studies, we know the direction the ground pushes on the foot.
[0088] The stance phase of walking/running activities can be
further broken down into deceleration and acceleration phases. When
the prosthetic foot touches the ground, the foot pushes anteriorly
on the ground and the ground pushes back in an equal and opposite
direction--that is to say the ground pushes posteriorly on the
prosthetic foot. This force makes the prosthetic foot move. The
stance phase analysis of walking and running activities begins with
the contact point being the posterior lateral corner 18, FIGS. 5
and 8, which is offset more posteriorly and laterally than the
medial side of the foot. This offset at initial contact causes the
foot to evert and the calf shank to plantar flex. The calf shank
always seeks a position that transfers the body weight through its
shank, e.g., it tends to have its long vertical member in a
position to oppose the ground forces. This is why it moves
posteriorly-plantar flexes to oppose the ground reaction force
which is pushing posteriorly on the foot.
[0089] The ground forces cause calf shanks 6, 44, 45, 46, 47, 50
and 51 and those in the other embodiments to compress with the
proximal end moving posterior. In calf shanks 48 and 49, if the
distal concavity is compressed in response to the ground reaction
forces the proximal concavity would expand and the entire calf
shank unit would move posteriorly. The initial loading ground
forces cause the lower end of the calf shank to compress with the
proximal end moving posteriorly. The calf shank lower tight radius
compresses simulating human ankle joint plantar flexion and the
forefoot is lowered by compression to the ground. At the same time
to the posterior aspect of keel, as represented by hindfoot 4,
depicted by 17 compresses upward through compression. Both of these
compressive forces act as shock absorbers. This shock absorption is
further enhanced by the offset posterior lateral heel 18 which
causes the foot to evert, which also acts as a shock absorber, once
the calf shank has stopped moving into plantar flexion and with the
ground pushing posteriorly on the foot.
[0090] The compressed members of the foot keel and calf shank then
start to unload--that is they seek their original shape and the
stored energy is released--which causes the calf shank proximal end
to move anteriorly in an accelerated manner. As the calf shank
approaches its vertical starting position, the ground forces change
from pushing posteriorly to pushing vertically upward against the
foot. Since the prosthetic foot has posterior and anterior plantar
surface weight bearing areas and these areas are connected by a
non-weight bearing long arch shaped midportion, the vertically
directed forces from the prosthesis cause the long arch shaped
midportion to load by expansion. The posterior and anterior
weight-bearing surfaces diverge. These vertically directed forces
are being stored in the long arch midportion of the foot--as the
ground forces move from being vertical in nature to anteriorly
directed. The lower end of the calf shank expands--simulating ankle
dorsiflexion. This causes the prosthetic foot to pivot off of the
anterior plantar weight-bearing surface. As weight unloading
occurs, the long arch of the midfoot portion 5 changes from being
expanded and it seeks its original shape which creates a simulated
plantar flexor muscle group burst. This releases the stored
vertical compressed force energy into improved expansion
capabilities.
[0091] The long arch of the foot keel and the calf shank resist
expansion of their respective structures. As a consequence, the
calf shank anterior progression is arrested and the foot starts to
pivot off the anterior plantar surface weight-bearing area. The
expansion of the midfoot portion of the foot keel has as high and
low response capability in the case of the foot keels in the
example embodiments of FIGS. 3-5 and 8, FIGS. 11 and 12, FIG. 13
and FIG. 14. Since the midfoot forefoot transitional area of these
foot keels is deviated 15.degree. to 35.degree. externally from the
long axis of the foot, the medial long arch is longer than the
lateral long arch. This is important because in the normal foot,
during acceleration or deceleration, the medial aspect of the foot
is used.
[0092] The prosthetic foot longer medial arch has greater dynamic
response characteristic than the lateral. The lateral shorter toe
lever is utilized when walking or running at slower speeds. The
body's center of gravity moves through space in a sinusoidal curve.
It moves medial, lateral, proximal and distal. When walking or
running at slower speeds, the body's center of gravity moves more
medial and lateral than when walking or running fast. In addition,
momentum or inertia is less and the ability to overcome a higher
dynamic response capability is less. The prosthetic foot of the
invention is adapted to accommodate these principles in applied
mechanics.
[0093] In addition, in the human gait cycle at midstance the body's
center of gravity is as far lateral as it will go. From midstance
through toe off the body's center of gravity (BCG) moves from
lateral to medial. As a consequence, the body's center of gravity
progresses over the lateral side of the foot keel 2. First (low
gear) and as the BCG progresses forward, it moves medially on foot
keel 2 (high gear). As a consequence, the prosthetic foot keel 2
has an automatic transmission effect. That is to say, it starts in
low gear and moves into high gear every step the amputee takes.
[0094] As the ground forces push anteriorly on the prosthetic foot
which is pushing posteriorly on the ground, as the heel begins to
rise the anterior portion of the long arch of the midfoot portion
is contoured to apply these posteriorly directed forces
perpendicular to its plantar surface. This is the most effective
and efficient way to apply these forces. The same can be said about
the posterior hindfoot portion of the prosthetic foot. It is also
shaped so that the posteriorly directed ground forces at initial
contact are opposed with the foot keel's plantar surface being
perpendicular to their applied force direction.
[0095] In the later stages of heel rise, toe off walking and
running activities, the ray region of the forefoot portion is
dorsiflexed I5.degree.-35.degree.. This upwardly extending arc
allows the anteriorly directed ground forces to compress this
region of the foot. This compression is less resisted than
expansion and a smooth transition occurs to the swing phase of gait
and running with the prosthetic foot. In later stages of stance
phase of gait, the expanded calf shank and the expanded midfoot
long arch release their stored energy adding to the propulsion of
the amputee's soon to be swinging lower extremity.
[0096] One of the main propulsion mechanisms in human gait is
called the active propulsion phase. As the heel lifts, the body
weight is now forward of the support limb and the center of gravity
is falling. As the body weight drops over the forefoot rocker FIG.
5, line C-C there is a downward acceleration, which results in the
highest vertical force received by the body. Acceleration of the
leg forward of the ankle, associated with lifting of the heel,
results in a posterior shear against the ground. As the center of
pressure moves anterior to the metatarsal heads axis of rotation
the effect is an ever-increasing dorsiflexion torque. This creates
a full forward fall situation that generates the major progression
force used in walking. The signs of effective ankle function during
the active propulsion are heel lift, minimal ankle joint motion,
and a nearly neutral ankle position. A stable midfoot is essential
for normal sequencing in heel lift.
[0097] The posterior aspect of the hindfoot and the forefoot region
of the foot keel incorporate expansion joint holes and expansion
joint struts in several of the embodiments as noted previously. The
orientation of the expansion joint holes act as a mitered hinge and
biplanar motion capabilities are improved for improving the total
contact characteristics of the plantar surface of the foot when
walking on uneven terrain.
[0098] The Symes foot keels in FIGS. 9-12 are distinctively
different in dynamic response capabilities--as these capabilities
are associated with walking, running and jumping activities. These
foot keels differ in four distinct features. These include the
presence of a concavity in the proximate, posterior of the midfoot
portion for accommodating the Symes distal residual limb shape
better than a flat surface. This concavity also lowers the height
of the foot keel which accommodates the longer residual limb that
is associated with the Symes level amputee. The alignment concavity
requires that the corresponding anterior and posterior radii of the
arched foot keel midportion be more aggressive and smaller in size.
As a consequence, all of the midfoot long arch radii and the
hindfoot radii are tighter and smaller. This significantly affects
the dynamic response characteristics. The smaller radii create less
potential for a dynamic response. However, the prosthetic foot
responds quicker to all of the aforementioned walking, running and
jumping ground forces. The result is a quicker foot with less
dynamic response.
[0099] Improved task specific athletic performance can be achieved
with alignment changes using the prosthetic foot of the invention,
as these alignment changes affect the vertical and horizontal
components of each task. The human foot is a multi-functional
unit--it walks, runs and jumps. The human tibia fibula calf shank
structure on the other hand is not a multi-functional unit. It is a
simple lever which applies its forces in walking, running and
jumping activities parallel to its long proximal-distal
orientation. It is a non-compressible structure and it has no
potential to store energy. On the other hand, the prosthetic foot
of the invention has dynamic response capabilities, as these
dynamic response capabilities are associated with the horizontal
and vertical linear velocity components of athletic walking,
running and jumping activities and out-performing the human tibia
and fibula. As a consequence, the possibility exists to improve
amputee athletic performance. For this purpose, according to the
present invention, the fastener 8 is loosened and the alignment of
the calf shank and the foot keel with respect to one another is
adjusted in the longitudinal direction of the foot keel. Such a
change is shown in connection with FIGS. 1 and 2. The calf shank is
then secured to the foot keel in the adjusted position with the
fastener 8. During this adjustment, the bolt of the fastener 8
slides relative to one or both of the opposed, relatively longer,
longitudinally extending openings 9 and 10 in the foot keel and
calf shank, respectively.
[0100] An alignment change that improves the performance
characteristic of a runner who makes initial contact with the
ground with the foot flat as in a midfoot strike runner, for
example, is one wherein the foot keel is slid anterior relative to
the calf shank and the foot plantar flexed on the calf shank. This
new relationship improves the horizontal component of running. That
is, with the calf shank plantar flexed to the foot, and the foot
making contact with the ground in a foot flat position as opposed
to initially heel contact, the ground immediately pushes
posteriorly on the foot that is pushing anteriorly on the ground.
This causes the calf shank to move rapidly forward (by expanding)
and downwardly. Dynamic response forces are created by expansion
which resists the calf shank's direction of initial movement. As a
consequence, the foot pivots over the metatarsal plantar surface
weight-bearing area. This causes the midfoot region of the keel to
expand which is resisted more than compression. The net effect of
the calf shank expansion and the midfoot expansion is that further
anterior progression of the calf shank is resisted which allows the
knee extenders and hip extenders in the user's body to move the
body's center of gravity forward and proximal in a more efficient
manner (i.e., improved horizontal velocity). In this case, more
forward than up than in the case of a heel toe runner whose calf
shank's forward progression is less resisted by the calf shank
starting more dorsiflexed (vertical) than a foot flat runner.
[0101] To analyze the sprint foot in function, an alignment change
of the calf shank and foot keel is made. Advantage is taken of the
foot keel having all of its concavities with their longitudinal
axis orientation parallel to the frontal plane. The calf shank is
plantar flexed and slid posterior on the foot keel. This lowers the
distal circles even further than on the flat foot runner with the
multi-use foot keel like that in FIGS. 3-5 and 8, for example. As a
consequence, there is even greater horizontal motion potential and
the dynamic response is directed into this improved horizontal
capability.
[0102] The sprinters have increased range of motion, forces and
momentum (inertia)--momentum being a prime mover. Since their
stance phase deceleration phase is shorter than their acceleration
phase, increased horizontal linear velocities are achieved. This
means that at initial contact, when the toe touches the ground, the
ground pushes posteriorly on the foot and the foot pushes
anteriorly on the ground. The calf shank which has increased forces
and momentum is forced into even greater flexion and downward
movement than the initial contact foot flat runner. As a
consequence to these forces, the foot's long arch concavity is
loaded by expansion and the calf shank is loaded by expansion.
These expansion forces are resisted to a greater extent than all
the other previously mentioned forces associated with running. As a
consequence, the dynamic response capability of the foot is
proportional to the force applied. The human tibia fibula calf
shank response is only associated with the energy force
potential--it is a straight structure and it cannot store energy.
These expansion forces in the prosthetic foot of the invention in
sprinting are greater in magnitude than all the other previously
mentioned forces associated with walking and running. As a
consequence, the dynamic response capability of the foot is
proportional to the applied forces and increased amputee athletic
performance, as compared with human body function, is possible.
[0103] The prosthetic foot 53 depicted in FIG. 25 is like that in
FIG. 3 except for the adjustable fastening arrangement between the
calf shank and the foot keel and the construction of the upper end
of the calf shank for connection to the lower end of a pylon. In
this example embodiment, the foot keel 54 is adjustably connected
to the calf shank 55 by way of plastic or metal alloy coupling
element 56. The coupling element is attached to the foot keel and
calf shank by respective releasable fasteners 57 and 58 which are
spaced from one another in the coupling element in a direction
along the longitudinal direction of the foot keel. The fastener 58
joining the coupling element to the calf shank is more posterior
than the fastener 57 joining the foot keel and the coupling
element. By increasing the active length of the calf shank in this
way, the dynamic response capabilities of the calf shank itself are
increased. Changes in alignment are made in cooperation with
longitudinally extending openings in the calf shank and foot keel
as in other example embodiments.
[0104] The upper end of the calf shank 55 is formed with an
elongated opening 59 for receiving a pylon 15. Once received in the
opening, the pylon can be securely clamped to the calf shank by
tightening bolts 60 and 61 to draw the free side edges 62 and 63 of
the calf shank along the opening together. This pylon connection
can be readily adjusted by loosening the bolts, telescoping the
pylon relative to the calf shank to the desired position and
reclamping the pylon in the adjusted position by tightening the
bolts.
[0105] The prosthetic foot 70 according to a further embodiment of
the invention is depicted in FIGS. 28-31B. The prosthetic foot 70
comprises a foot keel 71, a calf shank 72 and a coupling element
73. The prosthetic foot 70 is similar to the prosthetic foot 53 in
the embodiment of FIGS. 25-27, except that the calf shank 72 is
formed with a downward, anteriorly facing convexly curved lower end
74 which is in the form of a spiral 75. The calf shank extends
upward anteriorly from the spiral to an upstanding upper end
thereof as seen in FIG. 28. The calf shank can be advantageously
formed of metal, such as titanium, as noted above but other
resilient materials could be used to form the semi-rigid, resilient
calf shank.
[0106] The spiral shape at the lower end of the calf shank has a
radius of curvature which progressively increases as the calf shank
spirals outwardly from a radially inner end 76 thereof and as the
calf shank extends upwardly from its lower, spiral end to its upper
end, which may be curved in the longitudinal direction or straight.
It has been found that this construction creates a prosthetic foot
with an integrated ankle and calf shank with a variable radii
response outcome similar to the parabola shaped calf shank of the
invention, while at the same time allowing the coupling element 73
and the calf shank 72 to be more posterior on the foot keel 71. As
a result, the calf shank and coupling element are more centrally
concealed in the ankle and leg of a cosmetic covering 77, see FIG.
28.
[0107] The coupling element 73 is formed of plastic or metal alloy,
and is adjustably fastened at its anterior end to the posterior of
foot keel 71 by a threaded fasterner 78 as shown in FIG. 30. The
foot keel has a longitudinally extending opening 79 in an upwardly
arched portion thereof which receives the fastener 78 to permit
adjusting the alignment of the calf shank and foot keel with
respect to one another in the longitudinal direction, e.g. along
the line 30-30 in FIG. 29, in the manner explained above in
connection with the other embodiments.
[0108] The posterior end of the coupling element includes a cross
member 80 which is secured between two longitudinally extending
plates 81 and 82 of the coupling element by metal screws 83 and 84
at each end of the cross member. The radially inner end 76 of the
spiral 75 is secured to the cross member 80 of the coupling element
by a threaded fastener 85 as depicted in FIG. 30. From its point of
connection to the cross member, the calf shank spirals around the
radially inner end 76 above the heel portion of the foot keel and
extends upward anteriorly from the spiral through an opening 85
through the coupling element between plates 81 and 82 anterior of
the cross member 80. A cross member 86 in the anterior end of
coupling element 73 is secured between plates 81 and 82 by
fasteners 87 and 88 at each end as seen in FIGS. 28 and 30. The
fastener 78 is received in a threaded opening in cross member
86.
[0109] The posterior surface of the cross member 86 supports a
wedge 89 formed of plastic or rubber, for example, which is
adhesively bonded at 90 to the cross member. The wedge serves as a
stop to limit dorsiflexion of the upwardly extending calf shank in
gait. The size of the wedge can be selected, wider at 89' in FIG.
31A, or narrower at 89'' in FIG. 31B, to permit adjustment of the
desired amount of dorsiflexion. A plurality of the wedges could be
used at once, one atop another and adhesively bonded to the
coupling element for reducing the permitted dorsiflexion.
[0110] A prosthetic socket, not shown, attached to the amputee's
lower leg stump can be connected to the upper end of the calf shank
72 via an adapter 92 secured to the upper end of the calf shank by
fasteners 93 and 94 as shown in FIG. 28. The adapter has an
inverted pyramid-shaped attachment fitting 91 connected to an
attachment plate attached to an upper surface of the adapter. The
pyramid fitting is received by a complementarily shaped socket-type
fitting on the depending prosthetic socket for joining the
prosthetic foot and prosthetic socket.
[0111] The prosthetic foot 100 of the embodiment of the invention
of FIGS. 32-34 comprises a longitudinally extending foot keel 101
having a forefoot portion 102 at one end, a hindfoot portion 103 at
an opposite end and a midfoot portion 104 extending between the
forefoot and hindfoot portions. An upstanding calf shank 105 is
secured to the foot keel at a lower end of the calf shank to form
an ankle joint of the prosthetic foot and extends upward from the
foot keel by way of an anterior facing convexly curved portion 106
of the calf shank. The calf shank is secured to the foot keel by
way of a coupling element 107 which is monolithically formed with
the forefoot portion 102 of the foot keel. The coupling element
extends posteriorly from the forefoot portion as a cantilever over
the midfoot portion 104 and part of the hindfoot portion 103. The
hindfoot portion and the midfoot portion of the foot keel are
monolithically formed and connected to the monolithically formed
forefoot portion and coupling element by fasteners 108 and 109.
[0112] The lower end of the calf shank 105 is reversely curved in
the form of a spiral 110. A radially inner end of the spiral 110 is
fastened to the coupling element by a connector 111 in the form of
a threaded bolt and nut extending through facing openings in the
calf shank and the coupling element. The coupling element posterior
portion 112 is reversely curved to house the spiral lower end of
the calf shank, which is supported at the upper end of the curved
portion 112 by the connector 111.
[0113] A stop 113 connected to the coupling element of the foot
keel by fasteners 114 and 115, limits dorsiflexion of the calf
shank. A cosmetic covering anterior of the calf shank in the shape
of a human foot and lower leg is optionally located over the foot
keel 101 and at least he lower end of the calf shank 105 with the
calf shank extending upwardly from the foot keel within the lower
leg covering in the manner illustrated and described in connection
with the embodiment of FIG. 28.
[0114] The prosthetic foot 100 of the embodiment of FIGS. 32-34 has
increased spring efficiency of the foot keel. Increasing the length
of the resilient foot keel from the toe region to the connection to
the lower end of the calf shank by the use of the monolithically
formed forefoot portion and coupling element results in a
significant spring rate gain. When the toe region of the foot keel
is loaded in the late midstance phase of gait, the downward facing
concavity of the cantilevered coupling element expands and the
reversely curved, anterior facing concavity at the posterior end of
the coupling element is compressed, each of these resilient
flexures of the coupling element of the foot keel stores energy for
subsequent release, during unloading, in a direction which aids the
forward propulsion of the limb in gait. The ankle formed by the
lower end of the calf shank in the prosthesis replicates human
ankle joint function, the prosthesis helping to conserve forward
momentum and inertia. The configuration of the foot keel in the
embodiment is not limited to that shown but could be any of the
foot keel configurations shown previously including those having a
high-low gear or a high gear only, having one or more expansion
joints, or being formed with plural longitudinal sections, for
example. Similarly, the calf shank of the embodiment could have its
upper end, e.g. above the ankle and the anterior facing convexly
curved portion extending upward from the foot keel, configured
differently as for example with a configuration in any of the other
embodiments disclosed herein. The upper end of the calf shank can
be connected to a socket on the lower limb of a person for use by
means of an adapter, for example that in FIG. 3, FIG. 27 or FIG.
28, or other known adapter.
[0115] The prosthetic foot 100 in FIGS. 32-34 further includes a
posterior calf device 114 to store additional energy with anterior
motion of the upper end of the calf shank in gait. That is, in the
active propulsion phase of gait force loading of the resilient
prosthesis expands the sagittal plane concavity of the shank 105
formed by the anterior facing convexly curved portion 106 of the
calf shank which results in anterior movement of the upper end of
the calf shank relative to the lower end of the calf shank and the
foot keel. A flexible elongated member 116, preferably in the form
of a strap, of the device 114 is connected to an upper portion of
the calf shank by fasteners 119 and to a lower portion of the
prosthetic foot, namely to coupling element 107 and lower end 110
of the shank by connector 111 as discussed above. The length of the
flexible strap, which can be elastic and/or non-elastic, is
tensioned in gait and can be fixed in length or adjusted by use of
a slide adjustment 117 between overlapping lengths of the
strap.
[0116] A curvilinear spring 118 is adjustably supported at its base
on the upper end of the calf shank, for example between the calf
shank and an adapter, not shown, secured to the calf shank, with
fasteners 119. The lower, free end of the spring is positioned to
interact with the flexible strap. When the strap is tensioned the
spring changes the direction of the longitudinal extent of the
strap. Anterior movement of the upper end of the calf shank in gait
tensions/further tensions (if the strap is initially preloaded in
tension) the strap and loads/further loads the spring to store
energy in force loading of the prosthetic foot in gait. This stored
energy is returned by the spring in force unloading of the
prosthetic foot to increase the kinetic power generated for
propulsive force by the prosthetic foot in gait.
[0117] When the strap 116 is shortened using the slide adjustment
117 to initially preload the strap in tension prior to use of the
prosthetic foot, the strap tension serves to assist posterior
movement of the upper end of the resilient shank as well as control
anterior movement of the calf shank during use of the prosthesis.
Assisting the posterior movement can be helpful in attaining a
rapid foot flat response of the prosthetic foot at heel strike in
the initial stance phase of gait akin to that which occurs in a
human foot and ankle in gait at heel strike where plantarflexion of
the foot occurs.
[0118] The assisting posterior movement and the controlling
anterior movement of the upper end of the resilient calf shank
during use of the prosthesis using the posterior calf device 114
are each effective to change the ankle torque ratio of the
prosthetic foot in gait by affecting a change in the sagittal plane
flexure characteristic for longitudinal movement of the upper end
of the calf shank in response to force loading and unloading during
a person's use of the prosthetic foot. The natural physiologic
ankle torque ratio in the human foot in gait, defined as the
quotient of the peak dorsiflexion ankle torque that occurs in the
late terminal stance of gait divided by the plantar flexion ankle
torque created in the initial foot flat loading response after heel
strike in gait has been reported as 11.33 to 1. An aim of changing
the sagittal plane flexure characteristic for longitudinal movement
of the upper end of the calf shank using the posterior calf device
114 is to increase the ankle torque ratio of the prosthesis to
mimic that which occurs in the human foot in gait. This is
important for achieving proper gait with the prosthesis and, for a
person with one natural foot and one prosthetic foot, for achieving
symmetry in gait. Preferably, through controlling anterior movement
and possibly assisting posterior movement using the posterior calf
device 114, the ankle torque ratio of the prosthesis is increased
so that the peak dorsiflexion ankle torque which occurs in the
prosthesis is an order of magnitude greater than the plantar
flexion ankle torque therein. More preferably, the ankle torque
ratio is increased to a value of about 11 to 1, to compare with the
reported natural ankle torque ratio of 11.33 to 1.
[0119] A further purpose of the posterior calf device is to improve
the efficiency of the prosthetic foot in gait by storing additional
elastic energy in the spring 118 of the device during force loading
of the prosthesis and to return the stored elastic energy during
force unloading to increase the kinetic power generated for
propulsive force by the prosthetic foot in gait. The device 114 may
be considered to serve the purpose in the prosthetic foot that the
human calf musculature serves in the human foot, ankle and calf in
gait, namely efficiently generating propulsive force on the
person's body in gait utilizing the development of potential energy
in the body during force loading of the foot and the conversion of
that potential energy into kinetic energy for propulsive force
during force unloading of the foot. Approaching or even exceeding
the efficiencies of the human foot in the prosthetic foot of the
invention with the posterior calf device is important for restoring
"normal function" to an amputee for example. The control of
anterior movement of the upper end of the calf shank 105 by the
posterior calf device 114 is effective to limit the range of
anterior movement of the upper end of the calf shank. The foot keel
in the prosthetic foot 100 by the expansion of its resilient
longitudinal arch in the coupling element 107 and the compression
of reversely curved portion 112 of the coupling element also
contributes to storing energy during force loading in gait as
discussed above. This potential energy is returned as kinetic power
for generating propulsive during force unloading in gait.
[0120] The prosthesis 120 in FIG. 35 comprises a foot keel 121, a
calf shank 122 and a posterior calf device 123. An adapter 124 is
connected by suitable fasteners, not shown, to the upper end of the
calf shank for securing the prosthesis to a socket on the lower
limb of a person for use. Like the embodiment of FIGS. 32-34, a
coupling element 125 of the prosthesis is monolithically formed
with a forefoot portion 126 of the foot keel. A hindfoot portion
127 of the foot keel is joined to the upper end of the reversely
curved portion of the coupling element by a fastener arrangement
128, shown disassembled in FIG. 39 prior to connection to the
coupling element and calf shank. The fastener arrangement includes
a radially inner component 129 against the radially inner end of
the reversely curved spiral of the lower end of the calf shank, and
a radially outer component 130 against the upper end of the
hindfoot portion 127. A mechanical fastener, not shown, such as a
through bolt and nut, extends through aligned openings in the
components 129 and 130 and the complementarily curved portions of
the hindfoot portion, coupling element and calf shank lower end
which are sandwiched between and joined to one another by the
fastening arrangement.
[0121] The posterior calf device 123 on the prosthetic foot 120
includes a coiled spring 131 supported at its one end at the upper
end of the calf shank for movement therewith. A second, free end of
the coiled spring has one end of a flexible elongated member, strap
132, secured thereto by a metal clip 133. The clip is connected at
its one end to a first end of the strap and at its other end is
hooked over in clamping engagement with the free end of the coiled
spring as depicted in FIG. 35. An intermediate portion of the
flexible strap 132 extends down to the foot keel and lower end of
the calf shank where it extends about a return 134 in the form of a
cylindrical pin 135 mounted on the component 130 of the fastener
arrangement 128. To minimize sliding resistance of the strap
against the pin, the pin 134 may be rotatably mounted in the
component 130. The second end of the strap is clampingly retained
at the upper end of the calf shank between the posterior surface of
the shank and a complementarily shaped spring retainer member 135
which extends part way down the length of the shank. The upper end
of the member 135 is secured between the upper end of the coiled
spring and the upper end of the shank by suitable fasteners, not
shown. The length of the flexible strap, which can be elastic
and/or non-elastic, is tensioned in gait. This length is fixed, or
it can be adjusted by use of a slide adjustment, not shown, between
overlapping lengths of the strap adjacent the connection to the
metal clip 133, for example.
[0122] Anterior movement of the upper end of the shank relative to
the foot keel and lower end of the shank in gait is yieldably
resisted by expansion of the coiled spring 131 and posterior
flexing of the lower end of the retainer member 135 to store energy
during force loading of the prosthesis in the late mid-stance phase
of gait, which stored energy is released during force unloading
thereby contributing to ankle power generation in the prosthesis
and improving efficiency. The coiled spring 131 is formed of spring
steel in the embodiment but other metal alloys or non-metals such
as plastic could be employed. The spring retainer member 135 is
formed of carbon fiber encapsulated in epoxy resin in the
embodiment but other materials, including a metal alloy, and
plastic could be used. The flexible strap 132, like the strap 116
in FIGS. 32-34, is made of a woven Kevlar (DuPont) material having
a width of 5/8 inch and a thickness of 1/16 inch but other
materials and dimensions could be employed as will be apparent to
the skilled artisan. The first end of the strap 132 extends through
an opening in the end of the metal clip 133 and is doubled back on
the strap where it is adjustably retained by a slide adjustment or
other fastener.
[0123] The prosthesis 140 in the embodiment of FIG. 36 employs the
calf shank 122 and posterior calf device 123 used with the
prosthesis 120 of FIG. 35. The foot keel 141 of the prosthetic foot
140 includes a reversely curved coupling element 142 connected to
the lower end of the calf shank by fastener arrangement 128 for
housing and supporting the spiral lower end of the calf shank. In
this form of the invention the coupling element is monolithically
formed with both the forefoot portion 143 and the hindfoot portion
144 of the foot keel.
[0124] The prosthetic foot 150 of the embodiment of FIG. 37 is like
that in FIGS. 35 and 36 except that the coupling element 151 is
formed as a separate element which is secured at its posterior end
by a fastener 153 to the foot keel 152 forming the forefoot,
midfoot and hindfoot portions 155, 156 and 157 of the foot keel.
The area of the connection at fastener 153 is posterior the
connection of the calf shank and the coupling element for
increasing the active length of the foot keel and its spring rate
in the late mid-stance phase of gait. This effect is still greater
in the embodiment of FIG. 38 where the coupling element 160 of the
prosthesis 161 extends to the posterior end of the foot keel 163
where it is connected to the foot keel by fastener 164. The
fastener can be a mechanical fastener such as a bolt and nut or
other fastener including a composite of wrapped carbon fiber and
epoxy resin or a composite of a wrapped aromatic polyamide fiber
such as Kevlar by DuPont and epoxy resin. The lower anterior end
165 of the coupling element is extended to serve as a stop for the
anterior movement of the calf shank in dorsiflexion. Alternatively,
a separate stop as provided at 113 in the embodiment of FIGS. 32-34
could be provided. Either type of stop could also be used in the
embodiments of FIGS. 35 and 36.
[0125] The prosthetic foot 170 in FIG. 40 is similar to the
prosthetic foot in the embodiment of FIGS. 28-31B. The prosthesis
170 includes a foot keel 171, a calf shank 172 and a coupling
element 173. The shank 172 is formed with a downward, anterior
facing convexly curved lower end 174 which is reversely curved in
the form of a spiral 175. The calf shank extends upward from the
spiral to an upstanding upper end thereof, which may be curved in
the longitudinal direction or straight.
[0126] The spiral shape at the lower end of the calf shank has a
radius of curvature which progressively increases as the calf shank
spirals outwardly from a radially inner, upper end 176 where it is
fastened to the coupling element by a connector, not shown, in the
form of a threaded bolt and nut extending through facing openings
in the calf shank and coupling element as in the embodiments of
FIGS. 32-38.
[0127] The coupling element 173 serves as a housing for the spiral
175 and is adjustably fastened to the foot keel 171 by a threaded
fastener as in FIG. 30. The foot keel has a longitudinally
extending opening in an upwardly arched portion thereof which
receives the fastener to permit adjusting the alignment of the calf
shank and foot keel with respect to one another in the longitudinal
direction as explained in connection with the other embodiments.
Instead of longitudinally extending plates 81 and 82 as in FIGS.
28-30, the coupling element 173 is formed with open sides and an
anterior facing opening bounded laterally by laterally spaced,
anterior side edges 177 of the coupling element. The calf shank
extends upwardly through the anterior facing opening as in the
embodiment of FIGS. 28-30. A stop, not shown, can be provided as in
FIGS. 28-30 to limit dorsiflexion of the calf shank in gait.
[0128] An adapter 124, like that in the embodiments of FIGS. 35-39
is connected by suitable fasteners, not shown, to the upper end of
the calf shank for securing the prosthesis to a socket on the lower
limb of a person for use. A posterior calf device 178 on the
prosthetic foot 170 is like device 123 in FIG. 35 and includes a
coiled spring 179 supported at its one end at the upper end of the
calf shank for movement therewith. A second, free end of the coiled
spring has one end of a flexible elongated member, strap 180,
secured thereto by a metal clip 181. The clip is connected at its
one end to a first end of the strap and at its other end is hooked
over in clamping engagement with the free end of the coiled spring
as in the posterior calf device in FIG. 35. An intermediate portion
of the flexible strap 180 extends down to the foot keel and lower
end of the calf shank where it extends about a return 182 in the
form of a cylindrical pin mounted on component 183 of the fastener
arrangement 184 joining the coupling element and lower end of the
calf shank. The pin 182 may be rotatably mounted in the component
183 to minimize sliding resistance. The second end of the strap is
clampingly retained at the upper end of the calf shank between the
shank and the coiled spring. The flexible strap can be fixed in
length or adjustable in length by use of a slide adjustment, not
shown, as in the embodiment of FIG. 35. The device 178 serves to
store energy during force of the prosthesis in the late mid-stance
phase of gait, which stored energy is released during force
unloading thereby contributing to sagittal plane ankle power
generation as discussed with respect to the embodiment of FIG.
35.
[0129] One difference between the prosthesis 170 in FIG. 40 and
prosthesis 70 in FIG. 28-30 is that the ankle of the prosthesis 170
is higher above the ground than the ankle in prosthesis 70. Note
the lower end of the reversely curved, spiral ankle joint 174 in
FIG. 40 is above the upwardly arched midportion of the foot keel
171 in FIG. 40 because of the upwardly and posteriorly extending
configuration of the coupling element 173 whereas the lower end 75
of the spiral 74 in prosthesis 70 of FIGS. 28-30 is lower than the
height of the upwardly arched midportion of the foot keel. It has
been recognized that the height of this ankle area above the ground
affects the ankle's sagittal plane angular change which occurs in
the stance phase of gait. A higher placement of the ankle area will
increase the angular change while a lower placement of the ankle
will decrease the angular change. Therefore, the higher placement
of the ankle as in FIG. 40 has greater angular velocity potential
for the same amount of angular change that occurs at the proximal
end of the shank. This increase in angular velocity is quite
significant; for example, an ankle height of two inches has 35%
less angular change than an ankle height of three and one-half
inches. The ankle height in the prosthesis of the invention is
determined by a number of factors including the size and
configuration of the coupling element, the longitudinal arch
height, the length of the forefoot, midfoot and hindfoot portions
of the foot keel, etc. as will be apparent to the skilled
artisan.
[0130] The prosthetic foot 190 of the embodiment of FIGS. 41-44 is
similar to the prosthetic foot in FIG. 40 except for its posterior
calf device 191. The prosthesis 190 includes a foot keel 192, a
calf shank 193 and a coupling element 194. The shank is formed with
a downward, anterior facing convexly curved lower end 195 which is
reversely curved in the form of a spiral 196. The calf shank
extends upward from the spiral to an upstanding upper end thereof,
which may be curved in the longitudinal direction or straight.
[0131] The spiral shape at the lower end of the calf shank has a
radius of curvature which progressively increases as the calf shank
spirals outwardly from a radially inner, upper end 197 where it is
fastened to the coupling element by a connector 198, FIG. 43, in
the form of a threaded bolt and nut with washer extending through
facing openings in the calf shank and coupling element. In
particular, the bolt of the connector passes through an aperture of
a backing plate 199, an elongated aperture 200 in the coupling
element and an aperture in the radially inner, upper end 197 of the
shank where it is received in a threaded opening of a nut plate
201, FIG. 41. Longitudinal adjustment of the calf shank relative to
the coupling element and foot keel is made possible by the
elongation of aperture 200.
[0132] As in the embodiment of FIG. 40, the coupling element 194
serves as a housing for the spiral 196 and is adjustably fastened
to the foot keel by a threaded fastener 220 as described
previously, except that an elongated aperture at the connection is
provided in the coupling element instead of the foot keel to permit
adjusting the alignment of the calf shank and foot keel with
respect to one another in the longitudinal direction as explained
in connection with the other embodiments. The coupling element 194
is formed with open sides and an anterior facing opening bounded
laterally by laterally spaced, anterior side edges 202 of the
coupling element. The calf shank extends upwardly through the
anterior facing opening as in the embodiment of FIGS. 28-30. A
stop, not shown, can be provided as in FIGS. 28-30 to limit
dorsiflexion of the calf shank in gait. However, to avoid increased
stresses on the shank with high level activity by the user, as
discussed below the posterior calf device 191 acts as a stop to
preclude further anterior, longitudinal motion of the upper end of
the shank when a force loading on the shank is greater than that in
a normal gait cycle.
[0133] An adapter 203, like that in the embodiments of FIGS. 35-40
is connected to the upper end of the calf shank for securing the
prosthesis to a socket on the lower limb of a person for use. This
connection is described further below with reference to FIG. 43 of
the drawings. The posterior calf device 191 on the prosthetic foot
190 includes an elongated member in the form of a metal cable 204
of stainless steel or other alloy having a diameter of, for example
1/8'' to 3/16'', connected with play and extending between the
upper end of the calf shank and a lower portion of the prosthetic
foot. The length of the cable is such that force loading on the
calf shank encountered in a normal gait cycle does not tension the
cable with the longitudinal movement of the upper end of the calf
shank anteriorly in dorsiflexion or posteriorly in plantarflexion.
However, where a force loading on the calf shank during use, e.g.
from a loading or push off force, is greater than that encountered
in a normal gait cycle, preferably where a force loading is greater
than 120% of body weight of the user, the cable length is such in
relation to the anterior, longitudinal movement of the upper end of
the shank relative to the foot keel that the cable is tensioned to
limit, e.g. stop, further anterior, longitudinal motion of the
upper end of the calf shank to avoid increased stressing of the
calf shank.
[0134] The upper and lower ends of the cable 204 are each provided
with a connector 205, in the form of a swaged metal sleeve on the
cable, for example. The connector at the lower end is schematically
depicted in FIG. 44. These connectors function to retain the cable
ends in their respective blocks when the cable is tensioned. An
upper metal block 206, formed of a metal such as aluminum, titanium
or stainless steel, is fastened to the upper end of the calf shank
by socket head counter screws 207 which extend through apertures in
the calf shank and block 206 into threaded holes in a metal tongue
208 as shown in FIG. 44. The upper end of the block 206 has a
recess 209 for the connector 205 at the upper end of the cable and
a groove 210 extending downwardly from the recess along the
posterior surface of the block for receiving and guiding the metal
cable 204. The tongue 208 overlays the cable and block when secured
by the screws 207 against the block. The diameter of the connector
205 is larger than the diameter of the groove 210 in order to
retain the upper end of the cable in the recess 209 when the cable
is tensioned. The d-shaped block 206 is shown hollowed at 211 to
reduce weight.
[0135] The lower end of the cable 204 extends through an aperture
212 in a lower metal block 213, formed of a metal such as aluminum,
titanium or stainless steel, where it is secured by connector 205
thereon. A resilient bumper 221 formed of rubber or synthetic
rubber such as polyurethane, for example, in the form of a washer
1/4'' to 3/16'' thick, for example, is located about the cable
between the connector 205 and the adjacent end of the block 213.
The resilient bumper absorbs shock when the cable is tensioned
during use and it also serves to store energy and return the same
for improving efficiency of the prosthesis as discussed above. The
block 213 is pivotably connected to the end of the backing plate
199 by a stainless steel dowel pin 214, which may have a diameter
of 1/8'' to 3/16'', for example, extending through aligned
apertures in the block and the backing plate. The openings in the
lower block for the pin are preferably provided with bushings to
allow pivoting of the lower block about the dowel pin relative to
the coupling element and foot keel in use. By pivotably connecting
the lower end of the cable on the anterior side of the backing
plate 199 and redirecting the upper end of the cable posteriorly
over the posterior surface of the longitudinally wider lower end of
d-shaped upper block 206, when the upper end of the calf shank
moves anteriorly in the longitudinal direction a sufficient
distance to tension the cable, the pull on the cable is in a
preferred direction, e.g. is essentially vertical.
[0136] The connection of the posterior calf device 191 to the
prosthesis is followed by enclosure of the upper end of the
assembly in an aluminum, titanium or stainless steel socket head
215. The socket head has internal grooves that accept the tongue
208, block 206 and shank 193. The socket head is secured to the
assembly with three set screws 216, two on the anterior side and
one on the posterior side as depicted in FIG. 43. A further socket
head 217 of the adapter 204 is then telescoped over the socket head
215 and retained thereon by tightening socket head cap screw 218 in
the apertures of a band clamp about the lower end of the socket
head 217. The upper end of the socket head 217 is provided with two
pairs of set screws 219 which respectively allow longitudinal
angular change and medial-lateral angular change of a structure
received by the socket head. This allows transverse plane motion
and tow in-tow out adjustment of the prosthesis with respect to the
structure on the leg stump of the user.
[0137] This concludes the description of the example embodiments.
Although the present invention has been described with reference to
a number of illustrative embodiments, it should be understood that
numerous other modifications and embodiments can be devised by
those skilled in the art that will fall within the spirit and scope
of the principles of this invention. For example, the lower end of
the calf shank in the prosthetic foot of the invention is not
limited to a parabola shape or a spiral shape but can be hyperbolic
or otherwise downward convexly, curvilinearly configured to produce
the desired motion outcomes of the foot when connected to the foot
keel to form the ankle joint area of the foot. Likewise, the
configuration of a spring in the device could be different than
those shown. For example, a resilient tube of metal or plastic
extending transversely to the longitudinal extent of the prosthesis
could be interposed between the elongated member and the upper
portion of the shank for storing and releasing energy. The features
of the various embodiments including the materials for construction
could also be used with one another. More particularly, reasonable
variations and modifications are possible in the component parts
and/or arrangements of the subject combination arrangement within
the scope of the foregoing disclosure, the drawings, and the
appended claims without departing from the spirit of the invention.
In addition to variations and modifications in the component parts
and/or arrangements, alternative uses will also be apparent to
those skilled in the art.
* * * * *