Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Leg – Ankle
Reexamination Certificate
1998-04-14
2001-07-03
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Leg
Ankle
C623S055000
Reexamination Certificate
active
06254643
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to prosthetic devices, and in particular, prosthetic devices incorporating a rigid shin portion and a small radius or tight ankle section.
BACKGROUND OF THE INVENTION
Many types of prosthetic devices have been developed over the years. In the early years, emphasis was placed on constructing an artificial limb which looked and moved much like a human limb. For example, many prosthetic devices were fabricated with a leg member and a foot member, with some form of pivoting member therebetween near the ankle region to allow the foot member to rotate about the ankle region. Elaborately constructed prosthetic devices were introduced, each attempting to simulate the natural movement of the human leg, ankle and foot. Though each of these attempts were intended to provide some level of normalcy to the artificial limb, they lacked the resilient energetic response needed for non-sedentary activities.
Various improvements have been made to prosthetic devices to enable the amputee to substantially increase his or her activity level. The advent of new materials, such as graphite composite materials, which are lightweight, strong, durable and relatively flexible, have been developed to further improve the performance of prosthetic devices. Also, contrary to earlier thinking, better compliance and energy response has been obtained by simplifying the structure of the prosthetic device rather than making it more complex. Prosthetic devices incorporating simple curved, flat, spring-like members have been developed which now enable amputees to participate in strenuous activities, such as tennis, basketball and jogging.
In particular, a prosthetic foot and leg device allowing a high degree of mobility on the part of an amputee was disclosed in applicant's U.S. Pat. No. 4,457,913 entitled “COMPOSITE PROSTHETIC FOOT AND LEG.” That patent discloses a prosthetic foot and leg device utilizing a resin impregnated high-strength filament structure for the leg portion, foot portion and heel portion, with all three regions being provided with substantial elastic flexibility, of relatively low energy absorption characteristics, so as to give the wearer high mobility with a relatively natural feel. Contrary to earlier prosthetic devices which incorporated a rotatable or articulated ankle mechanism, this prosthetic device has no moving parts other than the inherent flexibility and energy response characteristics of the material itself.
That prosthetic device also has a substantially elastic leg portion, wherein the flexibility of the leg portion is in addition to the flexibility of the heel and foot portions. Though this flexibility provides additional energy storage and release, and gives the prosthesis increased resiliency and energy response, this additional flexibility in the leg makes the prosthesis somewhat springy, unlike the tibia and fibula of the human limb which are not flexible and elastic.
In U.S. Pat. No. 4,822,363, the applicant attempted to provide some rigidity to the shin portion so that the flexure would take place beneath the upper leg portion. However, as with the prosthetic device of the above-referenced patent, the flexibility and resiliency of the prosthetic device was built into the entire lower leg region, including the shin, foot, and heel portions, up to and including the bottom ten inches of the prosthetic device. It was thought that if the flexibility in the lower leg region was eliminated to any greater extent, the prosthesis would lose a valuable portion of its capacity to store and release energy. With at least ten inches of clearance between the lower extremity of the rigid shin portion and the ground, the curvature of the flexible shin and ankle regions was smooth and continuous, and the resiliency and energy response characteristics of this prior device was excellent, without stops or jolts during use. Furthermore, from a structural point of view, the smooth curvature of the shin and ankle regions could be adapted to have a substantial radius, thereby avoiding any stress concentrations in the prosthesis. Due to the gradual curve of a relatively large radius (in some cases the curve was complex and not a simple curve), the space beneath the curve member provided for a relatively long heel capable of demonstrating good resiliency and flexibility.
Nevertheless, the energy response of such previous devices was often too great for some patients, exceeding their particular needs. With certain geriatric or youth patients, the springiness of such prior devices was somewhat difficult to manipulate or control, reducing stability. Thus, there remains a need for a foot prosthesis which demonstrates good performance capabilities under a wide range of physical activities, but which at the same time provides enhanced safety, security, and control for the wearer.
SUMMARY OF THE INVENTION
The present invention represents a substantial improvement over the prior art prosthetic devices in that the high energy response characteristics are utilized in conjunction with a relatively stiff leg or shin portion, a lower bending axis and a tighter ankle section, which together more closely function like the ankle region of a natural human limb. Unlike the previous prosthetic devices, which flex along a relatively long leg distance, the present invention relates to a prosthetic device having an ankle section with a relatively tight radius of curvature, which substantially concentrates the bending in the ankle region to proximate the bending of the human ankle. The smaller radius of curvature also helps lower the flexing point, i.e., the axis of bending, of the prosthetic device, to more closely match the location of the human ankle region.
A lower axis of bending is an important advantage in the present invention due to the trend in recent years regarding the manner in which amputations are conducted. The medical profession is now recognizing the advantage of performing amputations lower to the ground, preserving a substantially longer stump for the amputee than in the previous conditions. This longer stump provides, in turn, a longer lever arm for use in connection with the prosthesis, thereby permitting the exertion of greater strength upon the prosthesis. This means that the prosthesis, if correctly engineered as in the present invention, can return an extremely high percentage of energy to the wearer in order to provide excellent performance; however, at the same time, the performance characteristics of the prosthesis must be accomplished in a structure which is provided with less distance from the ground to the stump. Thus, with lower amputations, higher performance is possible, but a greater risk of breakage due to stress concentrations exists.
However, the prosthesis of the present invention takes advantage of this tendency, while at the same time adequately addressing the issues of strength and performance. Thus, the present prosthesis can be used with excellent results by a much wider diversity of amputees including those with lower amputations. At the same time, stability and control are achieved.
Unlike prior art devices which disclose a flexible leg portion and a substantially large radius of curvature ankle section, which results in a very high rate of energy return, the present invention serves to relocate and confine the bending. In other words, with prior devices, flexibility and energy return were available in the upper leg regions of the prosthesis. In the present invention, however, since the upper leg region is substantially rigid, a portion of that flexibility previously available has been relocated to a newly designed ankle in which the flexibility is isolated or concentrated. While some overall performance is thereby sacrificed, greater prosthetic stability and control are achieved with yet excellent performance characteristics. This performance is also achieved through the design of cooperating heel and toe sections which have optimal flexible lever arms, as explained below in more detail. Thus, the flexibility of the pr
Knobbe Martens Olson & Bear LLP
Willse David H.
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