Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Leg – Knee
Patent
1992-10-01
1994-05-24
Green, Randall L.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Leg
Knee
623 44, A61F 264
Patent
active
053144988
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an artificial knee-joint according to the preamble of claim 1.
The gait of a thigh amputee is considerably different to that of the gait of a normal healthy person, due to the absence of important muscle groups. Because of the loss of the knee muscles, the amputee can no longer bend and then again actively stretch the knee-joint under load. In the case of earlier knee-joint prosthesis using various types of braking mechanisms, the prevention of leg collapse in the supporting phase, i.e. that -period in which the foot is in contact with the ground or like surface, has only been achieved with a greater or lesser degree of security. Thus, differing degrees of supporting-phase stability have been achieved. The prosthetic leg is fitted to the amputee with the knee straight, and the knee then remains straight during a major part of the supporting phase. If the knee-joint mechanism is very stable, it is not possible to bend the knee until the supporting phase is terminated. This impossibility of bending the knee at the beginning and the end of the supporting phase means that the amputee must consume more energy when walking. The absence of calf muscles also means that the gait of the person wearing the prosthesis is more energy demanding than the gait of a normal person.
The present artificial knee-joint is constructed imitate the working mode of the human knee-joint, so that the amputee is able to walk with a natural gait. The knee-joint can be said to be a further development of the existing quadruple-point polycentric type of joint. By polycentric joint is meant here that the rotational centre has different positions at different knee-joint angles, i.e. there are several pivot centres. The human knee-joint is also polycentric. By polycentrical quadruple-jointed knee is meant a knee in which the thigh part and the lower-leg part are mutually joined by two linkage mechanisms, each being pivotally connected at its respective ends to the thigh part and the lower-leg part. This results in four pivot points. Quadruple joint mechanisms are now the most common joints available. However, in order to achieve high supporting-phase stability, it is necessary to supplement these mechanisms with some form of mechanical/hydraulic lock or brake device. The earlier known technical solutions generally cause the knee-joint to become highly complex and undesirably heavy.
Described and illustrated in U.S. Pat. No. 2,638,605 is a knee-joint which comprises linkage mechanisms in which locking is effected by means of a catch with the knee straight, this catch being released by means of a linkage mechanism which transmits movement of the toe-part to the knee-joint. In addition to being highly complicated, a serious drawback is that the knee-joint is apparently too heavy for practical use and results in an unnatural termination of a walking step.
The object of the present invention is to provide an improved polycentric knee-joint which has high supporting-phase stability, which is light in weight and with which locking of the knee-joint is effected automatically in a simple fashion as a result of the construction and design of the knee-joint, and also to eliminate the drawbacks encountered with earlier known techniques. These objects are achieved by means of the invention, in that the artificial knee-joint mentioned in the introduction is constructed in the manner defined in the characterizing clause of claim 1. The inventive knee-joint is a polycentric joint and includes a linkage mechanism consisting of a plurality of linkage arms of varying lengths which are mutually arranged to achieve high supporting-phase stability and a simple, automatic locking function. This locking function is effective solely in an extended position and solely when load is exerted on the heel. When the foot rolls over onto the forward part, as the wearer of the prosthesis walks, the locking mechanism is released automatically. This means that the locking mechanism will not prevent natural termination or completion of a walkin
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patent: 5201776 (1993-04-01), Freeman
Green Randall L.
Willse D.
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