Patent Application
20120116540
The present invention relates to a prosthetic foot that is amenable to rapid, low cost production and to a method of making the prosthetic foot.
Applicants previously have discovered that during walking, the physiological foot-ankle complex provides a roll-over shape, or effective “wheel-like” rocker, that can be modeled as an arc of a circle's. The radius of this circle seems invariant to different walking speeds, to added trunk weight, or when walking with shoes of different heel heights. The radius, however, appears to vary with the height of the person. Based on these observations, applicants developed the so-called Shape&Roll foot (see Sam, M., Childress, D., Hansen, A., Meier, M., Lambla, S., Grahn, E., Rolock, J. (2004) The Shape&Roll Prosthetic Foot (Part I): Design and Development of Appropriate Technology for Low-Income Countries. Medicine Conflict and Survival, Vol. 20, No. 4, 294-306.); a prosthetic foot that provides the appropriate stature-matched roll-over shape of the physiological foot-ankle complex, as described by Hansen A H. Roll-over Characteristics of Human Walking With Implications for Artificial Limbs. PhD Dissertation, Northwestern University, Evanston, Ill. U.S.A., 2002.
The present invention provides a prosthetic foot that is easier to fabricate at lower cost while providing a desired roll-over shape during walking, and that can be used with commercially available cosmetic foot shells, making it more amenable to rapid production in low-income countries as well as industrialized countries.
An illustrative embodiment of the invention involves cutting or otherwise machining a three dimensional profile of the prosthetic foot shape from a solid block of material, such as a plastic plate, and then cutting or otherwise machining a plurality of slots in and along the length of the forefoot region of the machined foot shape to permit achievement of the appropriate roll-over shape during walking and slotting the heel region of the machined foot shape to provide shock absorption in the early stance phase of walking. A bore is drilled, cut or otherwise machined in the connector region of the foot shape to receive a connector adapter for the leg prosthesis to be connected to the foot.
The depth of the slots in the forefoot region of the foot shape is controlled to provide a desired compliance (stiffness) of the flexible foot plate of the machined foot shape during walking. The forefoot slots have open tops and sides. One or more forefoot slots can receive a respective stop element to adjust a flat region of the sole plate of the foot for stability in standing.
The present invention provides in another illustrative embodiment a prosthetic foot comprised of a one-piece (monolithic) shaped foot profile having a connector region with a bore to receive a connector adapter for a leg prosthesis, a forefoot region in front of the connector region with the forefoot region having a plurality of machined or molded slots along its length to provide the appropriate roll-over shape of the combined flexible foot plate, foot cosmesis, and shoe during walking, and a heel region below the connector region and having a machined or molded slot for shock absorption. The foot can be made by machining a solid block of suitable material or by molding material, such as injection molding or casting fluid material into a mold having the shape of the foot profile.
Further advantages of the present invention will become more apparent from the following detailed description taken in conjunction with the following drawings.
The present invention involves a Shape&Roll type prosthetic foot that is easy to fabricate at low cost while providing a desired roll-over shape during walking, and that can be used with commercially available cosmetic foot shells, making it more amenable to rapid production in low-income countries as well as industrialized countries.
Pursuant to one embodiment of the present invention, the Shape&Roll prosthetic foot is made from a solid block B of plastic material as shown in
In an illustrative embodiment of the invention, three dimensional foot profiles FP,
The foot profile shown in
Referring to
The heel region 16 of the machined foot profile is slotted as shown to provide shock absorption in the early stance phase of walking. In an illustrative embodiment of the invention, the heel region 16 is slotted by drilling or other machining a traverse hole 16a (perpendicular to the side plane of the foot profile) and removing a slot region 16b of the heel region adjacent and aft of the hole 16a.
A bore 12b,
The final machined prosthetic foot is shown in
The present invention envisions performing other machining operations on the foot profile FP to reduce the weight of the device such as drilling additional holes through the side or carving out sections of plastic that are unnecessary and addition of indents on the side of the foot to indicate where the slots 14s should be machined as well as where the slots 14s should stop in depth for certain individual weight and activity levels.
The slots 14s can be made by the foot manufacturer or by a clinician fitting the foot to an individual pateint, but can also be cut deeper by the clinician if the patient finds the foot to be too stiff. Moreover, the transverse heel hole 16a can be increased in diameter by drilling with a larger drill bit, allowing the clinician to increase the diameter of the hole 16a to impart a softer heel (if the patient finds it is too stiff).
Applicants have found that certain thickest sole plate thickness can be used for different patients of different weights. These thickest sole plates 11 will just barely close the slots 14s in the appropriate sequence to create the desired appropriate rollover shape for that patient.
Moreover, the height of the foot profile can be adjusted by lowering the height of the connector block region for different foot shells and for different amputation levels, perhaps even to accommodate a Symes amputation. These changes require a corresponding change to the dimensions of the holes for the foot bolt.
For example,
The prosthetic foot pursuant to the invention is advantageous in that it can provide a low-cost alternative to many low-cost prosthetic feet that are sold around the world including feet such as the commercially available SACH foot, which have been shown to have inferior walking function compared to the Shape&Roll prosthetic foot. The prosthetic foot of the present invention can provide a more biomimetic walking function, a longer effective foot length, and reduced sound limb loading compared to the SACH feet. It is also expected that this foot will provide superior balance properties to the SACH foot when used together with the one or more stop elements received in one or more slots 14s as described in copending U.S. Ser. No. 12/462,050 filed Jul. 28, 2009, the disclosure of which is incorporated herein by reference.
Although the above description described machining of the three dimensional foot profile and features from a solid block of plastic or other suitable material, the present invention envisions molding material to the desired three dimensional foot profile, such as injection molding or casting fluid foot material into a mold having the shape corresponding to the foot profile. A combination of machining and molding can be used to produce the prosthetic foot. For example, the foot profile can be molded in simple manner and then the forefoot slots, heel hole/slot, and connector bores can be machined into the molded one-piece foot profile.
Although the present invention has been described in connection with certain embodiments of the invention, those skilled in the art will appreciate that modifications and changes can be made therein within the scope of the invention as set forth in the appended claims.
This application is a continuation-in-part of copending U.S. Ser. No. 12/462,050 filed Jul. 28, 2009, which claims benefits and priority of provisional application Ser. No. 61/137,746 filed Jul. 31, 2008. the disclosures of both of which are incorporated herein by reference. This application also claims benefits and priority of U.S. provisional application Ser. No. 61/404,467 filed Oct. 4, 2010, the disclosure of which is incorporated herein by reference.
This invention was made with government support under Grant No. H133EO80009 awarded by the Department of Education (NIDRR). The government has certain rights in the invention.
| Number | Date | Country | |
|---|---|---|---|
| 61137746 | Jul 2008 | US | |
| 61404467 | Oct 2010 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12462050 | Jul 2009 | US |
| Child | 13200703 | US |
