Patent Application
20060241782
1. Field of the Invention
The present invention relates to a prosthetic foot, and more particularly to a vertical shock absorbing prosthetic foot comprising a foot spring for absorbing energy, that is flexible about many axis, that is efficient at storing and returning energy during use and that is angularly adjustably connectable to a residual limb.
2. Description of the Related Art
People frequently are in need of prosthetic limbs as a result of accidents, disease or birth defects. The need for quality prosthetic feet is high. There have been many attempts to make suitable prosthetic feet, each desiring to reach goals of safety, functionality and comfort, among other qualities. The existing prosthetic feet have achieved varying levels of success at attaining each of these stated goals. Further, many strategies have been utilized in designing prosthetic feet. Some designs are relatively noncomplicated, and seek to use a simple design. Other designs are complex, and seek to simulate or copy the structure of the human foot.
One prosthetic foot in particular is made by Freedom Innovations and sold under the name Renegade LP. This foot has an uninterrupted component spanning from the ankle to the toe. A second component extends from the heel to the front of the foot. While this foot may work well for its intended purpose, it is not without some limitations. For example, there is not a heel spring incorporated into the design. Another limitation of this foot is that there is no way to adjust the location of the heel with respect to the residual limb.
Another existing prosthetic foot is sold by Ossur under the name Modular III. This foot has one uninterrupted component forming the ankle and spanning to the toe area. A heel component depends rearward from the major component to the heel. This heel component connects to the bottom surface of the major component. A primary advantage of this foot resides in its simplicity. However, there are drawbacks also associated therewith. One limitation is the lack of adjustability of the location of the heel with respect to the residual limb. A further limitation of this foot is the lack of a heel spring.
A third prosthetic foot is an assembly that is shown in U.S. Pat. No. 6,129,766 to Johnson et al. This patent discloses an ankle member, a heel member pivotally connected to the ankle member, and an elongate metatarsal-toe member having a rear portion underlying a forward portion of the heel member and projecting forwardly from the heel member. This foot has compressible elements incorporated between the pivotally connected members. This foot, being an assembly, is relatively complicated when compared to the previously described prosthetic feet. A further limitation of this foot is that there may be inherent noise problems incorporated into the design of the compressible elements. This is evidenced by the presence of, and the need for, noise abatement features being described in the disclosure.
A fourth prosthetic foot is sold by Otto Bock under the name LuXon Max. This foot shows a relatively flat and uninterrupted component spanning from the ankle location forward to a location above and rearward of the toe location. Distinct heel and toe components are connected to the bottom of the flat component. One limitation of this foot is that there is no way to adjust the location of the heel with respect to the residual limb. Another limitation of this foot is that there is no heel spring incorporated into the design.
Yet another prosthetic foot is shown in U.S. Pat. No. 6,602,295 to Doddroe et al. The foot shown in this patent has a foot plate, which is an uninterrupted plate spanning from heal to toe. A toe spring and a heel spring are provided. The toe spring is forward of the heel spring. The toe spring and heel spring are independently connected to a top plate. Further, the heel spring is rotatably connectable to the top plate and the foot plate.
Another prosthetic foot is shown in U.S. Pat. No. 6,241,776 to Christensen. The foot shown in this patent has a forefoot reinforcement member extending from an attachment section, through a curvilinear spring and arch section, to a toe end. A heel member extends from the arch section to the heel end. The strength and energy return in this foot is due to the flexing of the members. A limitation of this foot is that it is lacking is adjustability. A further limitation is that it does not have a heel spring.
Another prosthetic foot is shown in U.S. Pat. No. 5,037,444 to Phillips. That patent shows a foot with a forefoot portion and a demountably connected heel portion. At toe-off, the energy return is created from energy stored during the flexing of the forefoot member. One limitation is that the foot of this invention does not have a heel spring. A further limitation is the lack of adjustability of the location of the heel.
Thus there exists a need for a prosthetic foot that solves these and other problems.
The present invention relates to a vertical shock absorbing prosthetic foot that has a forefoot having a toe spring and a toe plate and a heel having a heel spring and a heel strike. Advantageously, the heel spring and toe spring comprise a foot spring. These components can be made of carbon epoxy composite material and can be integral, or can be assembled from multiple components. A connector is used to connect the foot to a residual limb or other prosthetic components. The connector can have a top piece and a bottom piece.
According to one aspect of the present invention, the toe spring can be a forward opening, or forward facing, toe spring, and the heel spring can be a rearward opening heel spring. The toe spring can have a rear that is rearward of the front of the heel spring. The foot spring, being comprised of the toe spring and heel spring, can be generally loop shaped. The connector has a shape that is complementary to the foot spring.
According to another aspect of the present invention, the connector can be adjustably connected to the foot spring by rotating the connector around the foot spring. This results in the practitioner being able to adjustably select the location of the heel with respect to the residual limb.
One advantage of the prosthetic foot of the present invention is that the connector is adjustably connectable to the foot, allowing the practitioner to adjust the location of the heel with respect to the connector. The location of the heel with respect to the connector contributes to overall length of the prosthetic limb, and can affect gate. Further, varying the location of the heel will affect the amount of flexing and deflection of the heel strike and compression of the heel spring at heel-strike. This adjustability results in the foot being more properly positioned given the needs and uses of a particular person.
Another advantage of the prosthetic foot of the present invention is that the foot spring is comprised of the toe spring and the heel spring. In this regard, the toe spring and heel spring are coacting springs that are not entirely independent of each other. Further, the toe spring, or at least a portion thereof, is located rearward of at least a portion of the heel spring. This advantageously allows for increased space for spring compression of the toe spring and heel spring in the limited space of the prosthetic foot.
Related, a further advantage of the prosthetic foot of the present invention is that the present invention provides support to the person at mid-stance. This is accomplished by flexing of the heel strike and toe plate, and of compression of the heel spring and toe spring. This flexing and compression relieve problems that may normally be associated with flat foot. Further, the energy in the heel strike and heel spring is useful in propelling the foot towards toe-off, and, alternatively, the energy in the toe plate and toe spring can be useful in assisting the person onto the heel strike if the person chooses to rock backwards.
Also related, a further advantage yet of the prosthetic foot of the present invention is that the present invention is free of sharp angles. Sharp angles in a prosthetic foot can lead to stress concentrations. Avoiding stress concentrations decreases the likelihood of failure of the foot.
A still further advantage yet of the present invention is that it is customizable to suit the specific needs of a given person. This is initially accomplished by selecting an appropriate blank foot from a given number of sizes of blank feet. The prosthetic foot can then be reduced in size from the initial size to a desired size.
A still further advantage yet of the prosthetic foot of the present invention is that it incorporates a split toe design. The toes can deflect and flex independent of each other, such as when an object is under only one of the two toes. This is advantageous for stability on terrain that is not completely flat. The split toe design is also advantageous during inversion and eversion to maximize the amount to forefoot that is in contact with the ground.
A still further advantage yet of the prosthetic foot of the present invention is that the foot can be tapered. The tapered design is advantageous in as much as it allows for the pre-selection of the flexural characteristics of the prosthetic foot.
A still further advantage yet of the prosthetic foot of the present invention is that there are no moving or rotatably connected parts that may fail over time. Further, none of the parts of the present invention are in a rubbing engagement. The present invention is therefore free from undesired noises and is free from the need of noise abatement features.
Other advantages, benefits, and features of the present invention will become apparent to those skilled in the art upon reading the detailed description of the invention and studying the drawings.
While the invention will be described in connection with several preferred embodiments, it will be understood that it is not intended to limit the invention to those embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention as defined by the appended claims.
The prosthetic foot 10 of the present invention is preferably made from a carbon epoxy composite material. It will be understood that the present invention is not limited to being constructed of carbon epoxy composite material, and that other resilient materials can be used without departing from the broad aspects of the present invention.
The foot 10 is preferably made in blanks that can be reduced in length, or shortened, to meet the requirements of a particular person. Several size blanks can be made so that practitioners can select an appropriate blank for a starting point. Also, the blanks can be made to several heights or have features with varying sizes depending on the intended applications.
The prosthetic foot 10 of the present invention can be made to any desired thickness. Given that the thickness of the material is related to the flexural strength and amount of deflection of any given component of the foot, it is understood that blanks can be constructed having various thicknesses, and that each component within any given foot may be made with a different thickness. Further, it is understood that the thickness of material within any given part of the foot 10 can be tapered to achieve a desired flexural characteristic.
Calling attention now to
A foot 10 is provided that is generally comprised of a rear portion 11 and a front portion 12. A foot spring 13 is provided between the front and rear of the foot 10. In the preferred embodiment, the foot spring 13 generally has a loop or circular shape. However, it will be understood that the foot spring 13 could have other shapes without departing from the broad aspects of the present invention. Further, the foot spring 13 preferably has a radius of approximately one inch. However, the foot spring 13 could have a larger or smaller radius without departing from the broad aspects of the present invention. The prosthetic foot 10 of the present invention has a longitudinal axis 15 spanning the length of the foot. The longitudinal axis 15 is generally parallel with the ground 5 when the foot rests on the ground during zero load conditions. When viewed from above, the prosthetic foot has a right side 16 and a left side 17.
Referring now to
A toe spring 30 is at the second end 22 of the forefoot 20. The toe spring 30 has a top 31, a bottom 32, a front 33 and a rear 34. The toe spring 30 generally has an undeflected shape of a semicircle. Toe spring 30 is a forward opening toe spring, or forward facing toe spring. The toe spring 30 could have a different shape without departing from the broad aspects of the present invention. During a downward load condition, the toe spring compresses and deforms from its nondeflected semicircular shape in response to the applied force. Conversely, during an upward load condition, the toe spring 30 expands and deforms in response to the applied force. The toe spring 30 can twist during inversion and eversion.
A toe plate 40 is at the first end 21 of the forefoot. The toe plate 40 has a front end 41 and a rear end 42. The front end 41 of the toe plate is the foremost portion of the prosthetic foot 10. The toe plate 40 has a top surface 43 and a bottom surface 44. The top surface 43 of the toe plate 40 coincides with the first surface 23 of the forefoot 20, and the bottom surface 44 of the toe plate coincides with the second surface 24 of the forefoot. The rear end 42 is preferably integral with the bottom front end of the toe spring 30. The body of the toe plate 40 flexibly depends forward and downwardly from the toe spring 30. The toe plate slightly curves upwardly along its length. During a downward load condition, the toe plate 40 flexes and deflects upwards in response to the applied force.
Looking now at
Returning now to
The mating surface 56 of the plate 55 of the heel can be adhesively connected to the mating surface 26 of the plate 25 of the forefoot 20. Such a connection is preferably permanent.
A heel spring 60 is at the first end 51 of the heel 50. The heel spring 60 has a top 61, a bottom 62, a front 63 and a rear 64. The heel spring 60 generally has an undeflected shape of a semicircle. Heel spring 60 is a rearward opening heel spring, or rearward facing heel spring. The heel spring 60 could have a different shape without departing from the broad aspects of the present invention. During a downward load condition, the heel spring 60 compresses and deforms from its nondeflected semicircular shape in response to the applied force. Conversely, during an upward load condition, the heel spring 60 expands and deforms in response to the applied force. The heel spring can twist during inversion and eversion.
A heel strike is at the second end 52 of the heel. The heel strike 70 has a front end 71 and a rear end 72. The rear 72 of the heel strike comprises a lip 75. The rear end 72 of the heel strike is the rearmost portion of the prosthetic foot 10. The heel strike 70 has a top surface 74 and a bottom surface 75. The top surface 74 of the heel strike 70 coincides with the first surface 53 of the heel 50, and the bottom surface 75 of the heel strike 70 coincides with the second surface 54 of the heel 50. The front 71 of the heel strike 70 is preferably integral with the bottom rear end of the heel spring 60. The body of the heel strike 70 flexibly depends rearward and downwardly from the heel spring 60. The heel strike is generally flat except for the lip during a zero load condition. The lip 73 is generally bent upwards in relation to the remainder of the heel strike 70. During a downward load condition, the heel strike 70 flexes and deflects upwards in response to the applied force.
In the preferred embodiment, the toe spring is located rearward of the heel spring. Further, looking again as
Turning now to
A bottom piece 100 is also provided. The bottom piece 100 has a bottom surface 101 and a top surface 102. The bottom surface 101 is preferably flat. The top surface is preferably convex and complementary to the generally loop shaped toe spring 13. Holes 103 are provided for receiving bolts 105. The holes 103 are spaced apart a distance equal to the distance between holes 96 and 98 of the top piece 90. In this regard, the top and bottom pieces 90 and 100 can be aligned and bolted together using bolts 105. The connector 80 has an alignment axis 106. The bolts 105 are inserted into holes 103 generally parallel to the alignment axis 106.
Looking now to
Looking now to
Turning now to
The connector can be selectively positioned on the foot spring 13 to selectively adjust the location of the heel strike 70 with respect to the connector 80. One result is that the overall length of the prosthetic limb can be adjusted by adjusting the orientation of the alignment axis 106 of the connector on the foot spring 13. Two examples are provided, and are shown in
Operation of the present invention is illustrated in
As the person moves toward mid-stance, the heel strike 70 releases some of its stored energy to assist in propelling the foot 10 to the mid-stance position. Also, the heel spring 60 releases some of its stored energy to assist in raising the person upwards.
An operational view at mid-stance is provided in
It is noteworthy, that if the person happens to land in a flat foot orientation, the toe plate 40 and the heel strike 70 may deflect severely, and the foot spring 13 may compress severely, while absorbing the shock, and then release some energy to return the foot to mid-stance equilibrium.
Thus it is apparent that there has been provided, in accordance with the invention, a prosthetic foot that fully satisfies the objects, aims and advantages as set forth above. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description. Accordingly, it is intended to embrace all such alternatives, modifications, and variations as fall within the spirit and broad scope of the appended claims.
