WO2001049221A1

WO2001049221A1 - Polycentric axis foot and ankle assembly

Info

Publication number: WO2001049221A1
Application number: PCT/US2000/034521
Authority: WO
Inventors: Jack Mark
Original assignee: UNITED STATES MANUFACTURING Co
Current assignee: UNITED STATES MANUFACTURING Co
Priority date: 2000-01-05
Filing date: 2000-12-19
Publication date: 2001-07-12
Anticipated expiration: 2002-07-05
Also published as: AU2279501A

Abstract

A polycentric axis foot and ankle assembly (10) includes an upper bracket (30), a lower bracket (20), a front link movably attaching the front portion (32) of the upper bracket to the front portion of the lower bracket and a rear link movably attaching the rear portion (34) of the upper bracket (30) to the rear portion (34) of the lower bracket. In a preferred embodiment, the front portion of the upper bracket provides a pair of flanges (58, 60) for supporting an upper front shaft (100) and the rear portion of the upper bracket provides a pair of flanges for supporting an upper rear shaft (102). Each of the upper front shaft and upper rear shaft carries a spherical bearing for movable engagement with the front and rear links, respectively. The front portion of the lower bracket carries a pair of flanges for supporting a lower front shaft (90) and the rear portion of the lower bracket carries a pair of flanges for supporting a lower rear shaft (92).

Description

POLYCENTRIC AXIS FOOT AND ANKLE ASSEMBLY

FIELD OF THE INVENTION

This invention relates generally to prosthetic device, and more particularly to a polycentric axis foot and ankle assembly which provides multiple axes of rotation for the ankle.

BACKGROUND OF THE INVENTION

For smooth walking across uneven ground, it is important for an amputee to have a prosthesis that simulates the operation and motion of an anatomical foot by providing a full range of motion for the foot component with respect to the lower leg component. A full range of motion is accompanied by the use of a multiple axes of rotation ankle joint. Specifically, the anatomical foot and ankle are capable of dorsiflexion, plantarflexion, inversion, eversion. and transverse rotation. Dorsiflexion and plantarflexion comprise the movement up and down ofthe ball ofthe foot with respect to the heel that occurs during a normal forward step. Inversion and eversion are the twisting ofthe foot around its longitudinal axis, resulting in outward and inward tilting ofthe ankles, respectively. Transverse rotation occurs when the foot rotates with respect to the longitudinal axis ofthe leg, such as occurs during left and right turns ofthe body.

Prior prosthetic devices provided a lower leg component having an integral foot component without provision for an ankle joint. This type of prosthesis made it difficult for the amputee to maneuver on relatively even ground, much less on uneven ground. Recognizing this problem, prosthetic foot components were developed which provided a single axis of rotation. These prosthetic feet typically included adjustable anterior and posterior deflection bumpers for transition from plantarflexion to dorsiflexion. The single axis of rotation ankle joint is integral with the foot component. The disadvantage of this design is that, although being an improvement over designs with no axis of rotation, it does not provide stability on uneven ground.

Recognizing the need for a multiple axes of rotation ankle joint, a prosthetic foot and ankle combination manufactured by Blatchford Endolite under the trade name "Multiflex^" was developed to provide a full range of natural action. This design includes a ball and socket ankle joint integrally connected to the foot component through a serrated connection. A disadvantage with this type of design is that it is not universally adaptable for use between any manufacturer's lower leg and foot component. Other disadvantages of this design are that the ankle component is quite large, requires a special serrated adapter for attachment to the foot, and is expensive to manufacture.

Consequently, a need exists for an improved multiple axes prosthetic ankle component which is universally adaptable between any manufacturer's lower leg and foot components, and is compact, lightweight, and inexpensive to manufacture.

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SUBSTITUTE SHEET JLE 26) SUMMARY OF THE INVENTION

A polycentric axis foot and ankle assembly of the present invention includes an upper bracket, a lower bracket, a front link movably attaching a front portion of the upper bracket to a front portion ofthe lower bracket and a rear link movably attaching a rear portion ofthe upper bracket to a rear portion ofthe lower bracket. In a preferred embodiment, the front portion ofthe upper bracket provides a pair of flanges for supporting an upper front shaft and the rear portion of the upper bracket provides a pair of flanges for supporting an upper rear shaft. Each of the upper front shaft and upper rear shaft carries a spherical bearing for movable engagement with the front and rear link, respectively. The front portion of the lower bracket includes a pair of flanges for supporting a lower front shaft and the rear portion ofthe lower bracket includes a pair of flanges for supporting a lower rear shaft. The lower front shaft and lower rear shaft are preferably movably connected to the lower bracket flanges with flanged bearings.

The flanged bearings used to connect the lower shafts, in conjunction with the spherical bearings carried on the upper shafts provide multiple axes of movement for the foot and ankle assembly.

DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be more fully described in the following detailed description and the accompanying drawings. FIG. 1 is a perspective view of the polycentric foot and ankle assembly of the present invention;

FIG. 2 is an exploded view ofthe polycentric foot and ankle assembly of FIG. 1; and

FIG. 3 is a side cross-sectional view of one embodiment ofthe polycentric foot and ankle assembly.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIGS. 1, 2 and 3, foot and ankle assembly 10 of the present invention includes a bottom portion 12 and a top portion 14. Located at one end ofthe bottom portion 12, is a keel 16. Keel 16 is preferably foot-shaped and can provide the structural support for a prosthetic foot component 18 (shown in phantom in FIG. 3). A lower bracket 20 is used in conjunction with an upper bracket 30 to provide multiple axes of rotation and allowing a full range of motion for the foot and ankle assembly. In one embodiment ofthe present invention, the lower bracket 20 is attached to the top surface ofthe keel 16 using known adhesives or fasteners. In an alternative embodiment, the lower bracket 20 can be integrally attached to keel 16. Lower bracket 20 is preferably composed of a metallic or composite material. In the preferred embodiment, lower bracket 20 is formed of composite graphite.

Top portion 14 includes a prosthetic link 22 which includes a male connector 23 having a spherically convex base 24. The male connector includes a central boss 26 of frustopyramidal configuration which projects upwardly away from the spherically convex base 24. The frustopyramidal configuration formed by the main portion ofthe boss is of square cross-section and has four uniform sides facing angularly upwardly and outwardly in four directions spaced apart by 90°. The spherically convex base 24 of the male connector 22 is located the top surface of an upper bracket 30 of top portion 14. Link 22 is used to connect lower leg components (not shown).

The upper bracket 30 includes a front portion 32 and a rear portion 34. A right rear flange 36 and left rear flange 38 extend downward from the bottom surface 40 of the upper bracket 30 at the rear portion 34 of the bracket 30. The right and left rear flanges 36, 38 are preferably arranged in a facing relationship to each other and carry alignment holes 42 and 44, respectively, for passage of a shaft therethrough. Similarly, a right front flange 46 and left front flange 48 extend downward from the bottom surface 40 of the upper bracket 30 at the front portion 32 of the bracket 30. The right and left front flanges 46, 48 are preferably arranged in a facing relationship to each other and carry alignment holes 50 and 52, respectively, for passage of a shaft therethrough.

In the preferred embodiment, lower bracket 20 has a rear portion 54 and a front portion 56. The rear portion 54 of the lower bracket 20 carries a first rear flange 58 and a second rear flange 60. The first and second rear flanges 58, 60 are preferably arranged in a facing relationship to each other and carry alignment holes 62 and 64, respectively, for passage of a shaft therethrough. Similarly, the front portion 56 ofthe lower bracket 20 carries a first front flange 66 and a second front flange 68. The first and second front flanges 66, 68 are preferably arranged in a facing relationship to each other and carry alignment holes 70 and 72, respectively, for passage of a shaft therethrough.

Two polyurethane dampeners are positioned between the upper portion and the lower portion of the foot and ankle assembly 10 and comprise a front bumper 74 and a rear bumper 76. In one embodiment of the invention, an elastomer 78 is positioned between the front and rear bumpers 74, 76 and the upper bracket 30. The front bumper 74 preferably has a higher durometer hardness than the rear bumper 76 such that the front bumper 74 can act as a stop in the mid-stance position. The exact durometer hardness for both the front and rear bumpers can be varied depending upon the weight and activity level ofthe amputee. It is contemplated that the front and rear bumpers would be removable to allow the prosthesis to change the resistance of the bumpers to correspond to the amputee's anticipated activity level. In a preferred embodiment ofthe present invention, the front bumper 74 has a shore A 80 hardness, the rear bumper 76 has a shore A 70 hardness, and the elastomer 78 has a shore A 50 hardness. The ankle and foot assembly 10 is constructed by positioning the front and rear bumpers

74, 76 on the top surface of the lower bracket 20. In one embodiment of the invention, the lower bracket 20 comprises a dividing barrier 80 positioned between the front and rear bumpers 74, 76. The elastomer 78, if used, is preferably positioned on top of the bumpers 74, 76,

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SUBSTITUTE SHEET (RUE 26) between the bumpers and the upper bracket 30. In the preferred embodiment, the elastomer 78 is dimensioned such that the lower surface 82 of the elastomer 78 corresponds to the shape of the bumpers 74, 76 after the bumpers are positioned on the lower bracket 20. The upper surface

84 ofthe elastomer 78 is preferably dimensioned to correspond to the shape ofthe lower surface 40 of the upper bracket 30.

At the lower portion 12 of the foot and ankle assembly 10, a lower front shaft 90 is bridged between the first and second front flanges 66 and 68. Each end of the lower front shaft 90 is associated with a flanged bearing 94, such that the shaft is allowed a degree of freedom to rotate in two different planes. In the preferred embodiment, each flanged bearing 94 has a first end 96 that is positioned in an alignment hole 62, 64, 70 or 72 and a second end

98 that carries a shaft 90 or 92. As shown in FIG. 2, the first end 96 ofthe flanged bearing 94 is positioned in alignment hole 70 and the second end 98 ofthe flanged bearing 94 carries the lower front shaft 90. The first end 96 of the second flanged bearing 94 is positioned in alignment hole 72, the second end 98 of which carries the opposite end ofthe lower front shaft 90. The two flanged bearings allow lower front shaft 90 to bridge between alignment holes

70 and 72. While the ends of lower front shaft 90 are securely held in place and prevented from slipping out, the flanged bearings 94 enable the lower front shaft to have a certain degree of freedom to rotate and move axially.

In the preferred embodiment, a lower rear shaft 92 is bridged between the first rear flange 58 and second rear flange 60 in the same manner as the lower front shaft 90.

Specifically, the first end 96 of a flanged bearing 94 is positioned in alignment hole 62 and the second end 98 ofthe flanged bearing 94 carries the lower rear shaft 92. The first end 96 of a second flanged bearing 94 is positioned in alignment hole 64, the second end 98 of which carries the opposite end ofthe lower rear shaft 92. The two flanged bearings allow lower rear shaft 92 to bridge between alignment holes 62 and 64. While the ends of lower rear shaft 92 are securely held in place and prevented from slipping out, the flanged bearings 94 enable the lower rear shaft to have a certain degree of freedom to rotate and move axially.

At the upper portion 14 ofthe foot and ankle assembly 10, an upper front shaft 100 is provided between flanges 46 and 48. The ends of upper front shaft 100 are fixedly attached in alignment holes 50 and 52. In the preferred embodiment, a spherical bearing 104 is carried on the upper front shaft 100. In an alternative embodiment ofthe invention, spherical bearing

104 is integrally attached to the upper front shaft 100.

In a similar manner, an upper rear shaft 102 is provided between flanges 36 and 38.

The ends of upper rear shaft 102 are fixedly attached in alignment holes 42 and 44. A spherical bearing 104 is carried on the upper rear shaft 102 in a manner similar to that carried on the upper front shaft 100. In one embodiment ofthe invention, the spherical bearing 194 can be integrally attached to the upper rear shaft 102.

The lower and upper portions 12, 14 ofthe foot and ankle assembly 10 are connected to each other via a front link 106 and a rear link 108. In the preferred embodiment, each link

106, 108 has an upper aperture 110 dimensioned to receive the spherical bearing 104 on the upper shafts 100 and 102. Additionally, each link preferably has a lower aperture 1 12 dimensioned to receive one ofthe lower shafts 90, 92. In the assembled state ofthe preferred embodiment of the present invention, the upper front shaft 100 is directed through aperture

1 10 ofthe front link 106 such that the spherical bearing 104 is positioned within the aperture 110 and the lower front shaft 90 is directed through the lower aperture 112 of link 106. Similarly, the upper rear shaft 102 is directed through aperture 110 ofthe rear link 108 such that the spherical bearing 1-4 is positioned within aperture 1 10. The lower rear shaft 92 is directed through the lower aperture 1 12 of link 108.

The polycentric axis foot and ankle assembly ofthe present invention provides dynamic foot motion allowing the foot to articulate in multiple axes providing dorsiflexion, plantarflexion, inversion, eversion, and transverse rotation.

Although the present invention has been described and is illustrated with respect to a preferred embodiment thereof, it is to be understood that it is not to be so limited since changes and modifications may be made therein which are within the full and intended scope of this invention as hereinafter claimed.

Claims

1. A polycentric axis foot and ankle assembly, comprising: an upper portion and a lower portion; an upper bracket located on the upper portion having a front portion and a rear portion; a lower bracket located on the lower portion having a front portion and a rear portion; a front link pivotally attaching the front portion ofthe upper bracket to the front portion of the lower bracket; and a rear link pivotally attaching the rear portion ofthe upper bracket to the rear portion ofthe lower bracket.

2. A foot and ankle assembly according to claim 1 , further comprising: a first pair of flanges located at the front portion of the upper bracket and a second pair of flanges located at the rear portion of the upper bracket; a third pair of flanges located at the front portion of the lower bracket and a fourth pair of flanges located at the rear portion ofthe rear bracket; an upper front shaft bridged between the first pair of flanges ofthe upper bracket and an upper rear shaft bridged between the second pair of flanges of the upper bracket; a lower front shaft bridged between the third pair of flanges ofthe lower bracket and a lower rear shaft bridged between the fourth pair of flanges ofthe lower bracket; wherein the front link pivotally attaches the upper front shaft to the lower front shaft to provide multiple axis of movement ofthe foot and ankle assembly; and wherein the rear link pivotally attaches the upper rear shaft to the lower rear shaft to provide multiple axis of movement of the foot and ankle assembly.

3. A foot and ankle assembly according to claim 2 wherein the first and second pair of flanges ofthe upper bracket extend downward from a bottom surface ofthe upper bracket, wherein each flange ofthe first pair of flanges ofthe upper bracket defines an alignment hole therein, wherein the alignment holes are arranged in a facing relationship to each other for passage of the upper front shaft therethrough, wherein each flange of the second pair of flanges of the upper bracket defines an alignment hole therein, and wherein the alignment holes are arranged in a facing relationship to each other for passage of the upper rear shaft therethrough.

4. A foot and ankle assembly according to claim 2 wherein each ofthe upper front shaft and upper rear shaft carries a spherical bearing for rotational engagement with the front link and rear link, respectively.

5. A foot and ankle assembly according to claim 4 wherein the front link has an upper aperture and a lower aperture, wherein the upper aperture ofthe front link is positioned about the spherical bearing on the upper front shaft and wherein the lower front shaft is guided through the lower aperture ofthe front link providing multiple axis of movement ofthe foot and ankle assembly.

6. A foot and ankle assembly according to claim 5 wherein the rear link has an upper aperture and a lower aperture, wherein the upper aperture ofthe rear link is positioned about the spherical bearing on the upper rear shaft and wherein the lower rear shaft is guided through the lower aperture ofthe rear link providing multiple axis of movement ofthe foot and ankle assembly.

7. A foot and ankle assembly according to claim 2 wherein each flange ofthe third pair of flanges ofthe lower bracket defines an alignment hole therein, wherein the alignment holes are arranged in a facing relationship to each other for passage of the lower front shaft therethrough, wherein each flange ofthe fourth pair of flanges ofthe lower bracket defines an alignment hole therein, and wherein the alignment holes are arranged in a facing relationship to each other for passage ofthe lower rear shaft therethrough.

8. A foot and ankle assembly according to claim 7, further comprising: a first pair of flanged bearings, each flanged bearing positioned in one of the alignment holes of the third pair of flanges of the lower bracket, the first pair of flanged bearings supporting the lower front shaft therebetween; and a second pair of flanged bearings, each flanged bearing positioned in one ofthe alignment holes ofthe fourth pair of flanges ofthe lower bracket, the second pair of flanged bearings supporting the lower rear shaft therebetween.

9. A foot and ankle assembly according to claim 2, further comprising a front bumper and a bottom bumper positioned between the upper portion and lower portion ofthe foot and ankle assembly.

10. A foot and ankle assembly according to claim 9 wherein the bumpers are polyurethane and the front bumper has a shore hardness higher than the rear bumper.

11. A foot and ankle assembly according to claim 9 further comprising an elastomer positioned between the upper and lower portions ofthe foot and ankle assembly.

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SUBSTITUTE SHEET (RULE2S>

12. A foot and ankle assembly according to claim 9 wherein the lower bracket comprises a dividing barrier positioned between the front and rear bumpers.

13. A polycentric axis foot and ankle assembly, comprising: a first bracket having a first portion and a second portion; a second bracket having a first portion and a second portion; a first link pivotally attaching the first portion of the first bracket to the first portion ofthe second bracket; and a second link pivotally attaching the second portion of the first bracket to the second portion ofthe second bracket.

14. A foot and ankle assembly according to claim 13, further comprising: a first pair of flanges located at the first portion ofthe first bracket and a second pair of flanges located at the second portion ofthe first bracket; a third pair of flanges located at the first portion of the second bracket and a fourth pair of flanges located at the second portion of the second bracket; a first shaft bridged between the first pair of flanges of the first bracket and a second shaft bridged between the second pair of flanges ofthe first bracket; a third shaft bridged between the third pair of flanges ofthe second bracket and a fourth shaft bridged between the fourth pair of flanges of the second bracket; wherein the first link pivotally attaches the first shaft to the third shaft to provide multiple axis of movement ofthe foot and ankle assembly; and wherein the second link pivotally attaches the second shaft to the fourth shaft to provide multiple axis of movement ofthe foot and ankle assembly.

15. A foot and ankle assembly according to claim 14 wherein the first and second pair of flanges ofthe first bracket extend downward from a bottom surface ofthe first bracket, wherein each flange ofthe first pair of flanges ofthe first bracket defines an alignment hole therein, wherein the alignment holes are arranged in a facing relationship to each other for passage ofthe first shaft therethrough, wherein each flange ofthe second pair of flanges ofthe first bracket defines an alignment hole therein, and wherein the alignment holes are arranged in a facing relationship to each other for passage ofthe second shaft therethrough.

16. A foot and ankle assembly according to claim 14 wherein each ofthe first shaft and second shaft carries a spherical bearing for rotational engagement with the first link and second link, respectively.

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SUBSTITUTE SHEET (RUE 26)

17. A foot and ankle assembly according to claim 16 wherein the first link has a first aperture and a second aperture, wherein the first aperture ofthe first link is positioned about the spherical bearing on the first shaft and wherein the third shaft is guided through the second aperture ofthe first link providing multiple axis of movement ofthe foot and ankle assembly.

18. A foot and ankle assembly according to claim 17 wherein the second link has a first aperture and a second aperture, wherein the first aperture of the second link is positioned about the spherical bearing on the second shaft and wherein the fourth shaft is guided through the second aperture of the second link providing multiple axis of movement ofthe foot and ankle assembly.

19. A foot and ankle assembly according to claim 14 wherein each flange of the third pair of flanges of the second bracket defines an alignment hole therein, wherein the alignment holes are arranged in a facing relationship to each other for passage of the third shaft therethrough, wherein each flange of the fourth pair of flanges of the second bracket defines an alignment hole therein, and wherein the alignment holes are arranged in a facing relationship to each other for passage ofthe fourth shaft therethrough.

20. A foot and ankle assembly according to claim 19, further comprising: a first pair of flanged bearings, each flanged bearing positioned in one of the alignment holes of the third pair of flanges of the second bracket, the first pair of flanged bearings supporting the third shaft therebetween; and a second pair of flanged bearings, each flanged bearing positioned in one ofthe alignment holes ofthe fourth pair of flanges ofthe second bracket, the second pair of flanged bearings supporting the fourth shaft therebetween.

SUBSTTTUTE SHEET (RULE 26)