Thigh Prosthesis

Abstract

A thigh prosthesis comprises a thigh frame interconnected through a knee-joint mechanism to a crus with a foot. In the thigh frame a stump-receiving sleeve is articulately mounted, having a stump-receiving chamber. The stump-receiving sleeve is kinematically associated with the knee-joint mechanism in such a manner that to each position of the stump-receiving sleeve with respect to the thigh frame corresponds a definite position of the crus.

Description

This invention relates to medical engineering and has particular reference to prosthetics and, specifically, thigh prostheses.

At this time, known in the art are a variety of types of thigh prostheses, each consisting of a thigh frame or carcass which accommodates a stump-receiving chamber. The distal end of the thigh frame is connected to the proximal end of the crus through a single-pivot joint which is essentially a knee-joint mechanism possessing 1.degree. of freedom and which provides for passive coupling between the thigh frame and the crus. The distal end of the crus is connected to the foot so as to form the crural portion of the prosthesis. The mechanism of the knee joint has a retainer to which protects the latter against recurvation. In order to provide rotative motion of the crural portion during walking, the prosthesis is fitted with a knee-folding device formed of, for example, a rubber pull-piece or a spring-actuated knee-folding device of any conventional design.

In the so-called "patient-prosthesis" system, the prosthesis is generally designed as a mechanism possessing 2.degree. of freedom, i.e., a double flat pendulum composed of physical pendulums, for example, the upper leg or thigh portion and the lower leg or crural portion.

Oscillations of the thigh portion (thigh frame) in the sagittal plane about a fixed axis passing through the center of the hip joint head, result from the active forces of the thigh stump which are applied to the thigh frame (i.e., to the walls of the stump-receiving chamber) and due to its own weight, and with the frequency and amplitude of oscillations thereof being under control of the patient's CNS (central nervous system).

Oscillations of the crus in the sagittal plane, with respect to the horizontal axis passing through the fulcrum of the knee-joint mechanism, result from the forces of inertia that arise due to the oscillating motion which is performed by the fulcrum axis of the knee-joint mechanism, as well as from the action of gravitational forces and the elastic forces of the knee-folding device.

However, the period and amplitude of the crus oscillations with respect to the thigh frame cannot be readily controlled by the patient's CNS.

Another disadvantage which is inherent in the known prosthesis resides in the passive coupling between the thigh frame and the crus which prevents the patient for effecting a direct and a back coupling between himself and the crural portion of the prosthesis so as, to ensure that the oscillations of the crus depend upon those of the thigh frame. Additionally, the passive coupling excludes the formation of a preset motional behaviour of the crus in dependence upon the rhythm and character of walking, in effect, makes it impossible to provide, symmetric motion of the prosthesis members with respect to the other (unaffected) lower extremity. A further disadvantage of the known prosthesis lies in the presence of two degrees of freedom in the "prosthesis-patient" system, which prevents the formation of a rather high stability of the knee-joint mechanism against spontaneous swinging at the moment of support, and entails an increased consumption of the patient's intrinsic energy which must be spent for coordination of motions during prosthesis-aided walking, and also necessitates the use of appropriate locking devices or specially designed prostheses.

Moreover, when the crural portion of the prosthesis performs rotative motion along with the foot with respect to the axis of the knee-joint mechanism, an increase in the functional length of the prosthesis occurs at the moment of its transfer over the bearing surface. This fact necessitates the reduction of the overall prosthesis length as compared with the unaffected lower extremity, which results in requiring an increased consumption of the patient's intrinsic energy in order to lift his own weight when walking.

Another presently known prosthetics is a thigh prosthesis, which includes a thigh frame having a stump-receiving chamber formed therein, and a crus with a foot portion which are articulated to each other through two drag links and which, in turn, are through one of their ends articulated to the distal end of the thigh frame, and with their other ends, to the proximal end of the crus so as to form a four-bar polycentered mechanism for the knee-joint unit.

One of the drag links is in contact with the distal portion of the thigh frame so as to form a retainer which prevents the mechanism of the knee-joint unit from recurvation.

The thigh prosthesis of the above described design features rather high stability of the knee-joint mechanism against spontaneous swinging at the moment of resting upon the prosthesis as compared to the previously discussed prothesis, as well as some functional shortening of the overall length of the prosthesis at the moment of its transfer over the bearing surface which permits the prosthesis to be made equal in length to the unaffected extremity.

However, even this thigh prosthesis which has a polycenter mechanism of the knee-joint unit, suffers from the disadvantage in that it has no direct and back coupling between the prosthesis members and the patient, thereby causing uncontrolled motion of the crural portion of the prosthesis during walking, as well as providing for inadequate stability against spontaneous swinging. Such a prosthesis, like one having a single-articulation knee-joint mechanism, features asymmetrical motion of the prosthesis with respect to the unaffected extremity, which may be explained as follows:

Weight characteristics of the prosthesis crural portion entail a constant value for each particular case; consequently, the moment of mass inertia with respect to the axis of the knee-joint mechanism likewise remains a constant value.

Oscillating motion performed about the axis of the knee-joint mechanism gives rise to forces of inertia which provoke rotative motion of the crus in a direction opposite to that of the thigh frame motion. Angular displacement of the crus will increase in a direct proportion with the amplitude and in an inverse proportion with the period of oscillation of the thigh frame. This fact causes some lagging behind in the phase of motion of the crus with respect to the thigh frame, and an increased period of oscillation of the crus forwardly from its rear-most position.

The braking and knee-folding devices which are used in the known prostheses in order to diminish the flexural angle of and the period of oscillation of the crus, are subject to their own inherent disadvantages.

The frictional force in the braking devices, which proves to be rather constant for each particular case, is oppositely directed with respect to the forces of inertia and gravitational forces of the crural portion (i.e., crus-and-foot assembly) of the prosthesis, thus decreasing the angle of deflection of the crural portion with respect to the thigh frame, while at the same time increasing the period of its forward oscillations.

Elastic forces of the knee-folding devices impede the action of the forces of inertia and exert a further influence tending to decrease the angle of the flexural crus, but also in cooperation with the gravitational forces of the crus, these forces diminish the period of oscillation of the latter and concurrently cause an increase in the angular velocity and angular acceleration, whose maximum value occurs when the crus assumes its extreme front position and the prosthesis is completely extended in the knee-joint mechanism. This fact causes the generation of increased dynamic loads which act upon the patient's stump, thus adding to arrhythmia of prosthesis-aided walking.

Thus, forces of friction generated in the braking devices and elastic forces produced by the knee-folding devices, though decreasing the flexural angle of the crus, at the same time add to load forces which are applied to the thigh stump during the transfer of the prosthesis over the bearing surface, so as to cause an increased consumption of the patient's intrinsic energy.

Provision of passive coupling between the thigh frame and the prosthesis crural portion makes it impossible to actively influence the motional behaviour of the crus in conformance with the rhythm and character of walking.

The presence of a second degree of freedom in the "patient-prosthesis" system along with the absence of a direct and back coupling of the patient to the knee-joint mechanism of the prosthesis requires the patient to exercise constant control over the motion of the prosthesis members causing further expenditures of the patient's intrinsic energy for effecting the coordination of all of the motions which are performed by the members of the "patient-prosthesis" during walking.

It is therefore an essential object of the present invention to provide a thigh prosthesis which will enable the patient to actively control the motion of the knee-joint mechanism of the prosthesis and ensure the back coupling of that mechanism with the patient.

The foregoing object is attained due to the fact that in a thigh prosthesis, comprising a thigh frame accommodating a stump-receiving chamber, and a crus with a foot, the crus is interconnected with the thigh frame through a knee-joint mechanism possessing one degree of freedom and which is provided with a retainer for protecting the knee joint from recurvation, according the invention, the stump-receiving chamber is made of a stump-receiving sleeve which is articulated to the thigh frame so as to be free to swing or oscillate in the sagittal plane, and is kinematically associated with the knee-joint mechanism in a manner whereby each position of the stump-receiving sleeve with respect to the thigh frame corresponds to a definite position of the crus.

In the thigh prosthesis, wherein the knee-joint mechanism is made as a single-pivot articulated joint interconnecting the thigh frame and the crus, the kinematic association of the stump-receiving sleeve with the knee-joint mechanism is expediently formed of a link having one end thereof articulated to the movable distal end of the stump-receiving sleeve, while the other end is connected to an additional arm held in position on the crus, whereby forward motion of the distal end in the sagittal plane with respect to the thigh frame corresponds to the flexure of the prosthesis.

In the thigh prosthesis, wherein the knee-joint mechanism comprises two drag links forming along with the thigh frame and the crus a four-bar mechanism, the kinematic association of the stump-receiving sleeve with the knee-joint mechanism is expediently formed of a link having one end thereof articulated to the movable distal end of the stump-receiving sleeve, while the other end is connected to an additional arm held in position on the front drag link of the four-bar knee-joint mechanism and forming a double-arm lever together with said drag link, whereby forward motion of the distal end in the sagittal plane with respect to the thigh frame corresponds to the flexure of the prosthesis.

It is desirable that the link interconnecting the distal end of the stump-receiving sleeve with the double-arm lever be spring-loaded with respect to the stump-receiving sleeve in the direction of the prosthesis extension.

Walking with such prostheses involves minimum consumption of the patient's intrinsic energy, while the biomechanics of walking are close to normal, i.e., the parameters of motion of all the prosthesis members are identical with those of the unaffected extremity, irrespective of the rhythm and character of walking.

The inventive prostheses are also more functional as compared to the prior art prosthesis.

The herein-disclosed thigh prostheses are essentially linkage-type mechanisms enabling a biomechanical train of members possessing one degree of freedom to be obtained in the system so-called "patient-prosthesis," system as well as providing for a direct and back coupling between the patient and the artificial extremity, and concurrently controlled motion of its knee-joint mechanism. Provision of 1.degree. of freedom enables the prosthesis, with any two members thereof dead-fixed to each other, to be, in effect a static support possessing zero degree of mobility.

Movable connection between the stump-receiving sleeve and the thigh frame reduces the amplitude of oscillation of the common center of gravity of the prosthesis in the vertical plane and the amplitude of constrained oscillation of the thigh frame in the sagittal plane, which is conducive to a reduced consumption of the patient's intrinsic energy generally spent for moving the prosthesis forwardly during walking.

In the following description the invention is considered in detail by way of exemplary embodiments thereof, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a diagrammatic representation of a thigh prosthesis incorporating a knee-joint mechanism made as a single-pivot articulated arrangement, according to the invention;

FIG. 2 is the prosthesis of FIG. 1 in one of its dynamic positions;

FIG. 3 is a second embodiment of a thigh prosthesis having a four-bar knee-joint mechanism, according to the invention; and

FIG. 4 is the prosthesis of FIG. 3 in one of its dynamic positions.

Reference is now had to FIGS. 1 and 2, in which the thigh prosthesis of the invention comprises a stump-receiving sleeve 1, having wherein a stump-receiving chamber formed therein, a thigh frame 2, both being interconnected through two articulated joints 3 which are respectively located on the medial and lateral sides of the stump-receiving sleeve 1, and a crus 4 with a foot portion.

An optimum portion of location of the joints 3 on the stump-receiving sleeve 1 is the level of a natural hip joint, whereas the optimum position of installation of the joints 3 in constructing the prosthesis is the level of the proximal edge of the stump-receiving sleeve 1 on the medial side thereof. When using self-aligning bearings or those with floating inner races as the joints 3, the latter may be located on the lateral side somewhat more proximate than the joint 3 on the medial side of the stump-receiving sleeve 1.

THe thigh frame 2 and the crus 4 are interconnected by means of a single-pivot joint 5 which is, in effect, the knee-joint mechanism of the prosthesis. The stump-receiving sleeve 1, the thigh frame 2, the joint 5, and the crus 4 with the foot, collectively form the bearing frame of the prosthesis.

The stump-receiving sleeve 1 in its distal portion has a joint 6, to which a link 7 is connected at one of its ends, and a seat which accommodates a damper 8.

The crus 4 has an arm 9 located on the rear surface of the proximal portion so as to thereof form a double-arm lever therewith. The other end of the link 7 is connected to the arm 9 by means of an articulated joint 10.

An alternative way of connecting the distal end of the stump-receiving sleeve 1 to the proximal end of the crus 4 may involve, for example, any other kinematic pair, such as a gear train (not shown) instead of the link 7.

The link 7 is spring-loaded with respect to the stump-receiving sleeve 1 by means of an elastic member 10 which comprises, for example, a spring, so as to be biased in the direction of the prosthesis extension.

The tension of the elastic member 10 is adjusted when fitting the prosthesis so as to suit the weight data of the crus 4 and the character of the patient's gait. When in a static position, the tension of the elastic member 10 should be minimal.

The thigh frame 2 is provided with a retainer 11 which is adapted to interact with a damper 12 mounted in the proximal portion of the crus 4 so as to protect the knee joint from recurvation.

In order to provide increased stiffness, the frame 2 is fitted with a semi-ring 13 which, at the same time, performs the functions of a restrictor for the stump-receiving sleeve 1 to thereby limit its backward rotation with respect to the frame 2. From externally thereof the mechanism of the prosthesis is lined with an elastic material to thereby follow the shape and size of the patient's unaffected extremity.

The present thigh prosthesis, as shown in FIGS. 3 and 4, may also have a knee joint incorporating two drag links 14 and 15 (FIGS. 3, 4) which form, along with a thigh frame 16 and a crus 17, a four-bar knee-joint mechanism. A stump-receiving sleeve 18 of that prosthesis which includes a stump-receiving chamber, is connected to the thigh frame 16 via two articulated joints 19 similar to the joints 3 of the thigh prosthesis represented in FIGS. 1 and 2.

The front drag link 14 (FIGS. 3, 4) of the four-bar knee-joint mechanism is provided with an extra arm 20 so as to form, along with the drag link 14 a double-arm lever.

The arm 20 of the double-arm lever is articulated through a link 21 to the movable distal end of the stump-receiving sleeve 18.

The stump-receiving sleeve 18, the thigh frame 16, the drag link 14 with the arm 20, the drag link 15 and the crus 17 with the foot, collectively form the bearing frame of the prosthesis.

A retainer 22 is provided on the drag link 14 of the knee-joint mechanism in order to interact with a damper 23 on the thigh frame 16 to thereby prevent the knee joint from recurvation.

The link 21 is spring-loaded with respect to the stump-receiving sleeve in the direction of the prosthesis extension through an elastic member 24.

The tension of the elastic member 24, as well as the tension of the elastic member 10 (FIG. 1), is adjusted when fitting the prosthesis so as to suit any particular patient.

The thigh frame 16 (FIG. 3) has a semi-ring 25 which adds to the stiffness thereof and also serves tO restrict backward motion of the stump-receiving sleeve 18 with respect to the frame 16.

If the prosthesis is to be used for children or juvenile patients, the crus 4 (FIG. 1) and the crus 17 (FIG. 3) may be made extensible.

The prosthesis may be attached to the patient's stump by any conventional method such as, say, vacuum valves, binder or waist hangers, and the like.

The present thigh prosthesis functions as follows:

The stump-receiving sleeve 1 (FIG. 1) is capable of performing controlled oscillating motion with respect to the frame 2 With the fulcrum at the joints 3, the motion being established as a result of the interaction of the active forces of the stump, the gravitational forces of the prosthesis members, and the forces of inertia.

The active forces of the stump are variable both as to magnitude and direction, and their parameters are under the control of the patient's central nervous system. The gravitational forces of the prosthesis members have a constant magnitude for each particular case so that, consequently, the moment of inertia of the mass center about the axis of the knee-joint mechanism is maintained constant.

When the stump-receiving sleeve 1 turns forward with respect to the thigh frame 2 in the sagittal plane, its distal end imparts motion to the link 7 so as to cause the crus 4 to turn in the opposite direction in correspondence with the flexure of the prosthesis.

Thus, rotation of the stump-receiving sleeve 1 in the sagittal plane results in the turning of the crus 4, and corresponding thereto both in magnitude and direction.

The elastic member 10, as the flexural angle of the knee-joint mechanism becomes larger, brakes the rotary motion of the crus 4 and the stump-receiving sleeve 1, thus acquiring some amount of energy for imparting forward rotation to the crus 4.

Under the action of the active forces of the stump, of the elastic member 10 and of gravitational forces of the prosthesis members, the crus 4 performs forward rotary motion, thereby expecting its extension.

The damper 8, during the prosthesis extension, interacts with the crus 4 to provide smooth contact between the retainer 11 with the damper 12, both fixing the position of the crus 4 with respect to the frame 2, and thereby preventing recurvation of the knee-joint mechanism. When the damper 8 is compressed, there occurs further backward motion of the distal end of the stump-receiving sleeve 1, so as to cause further forward rotation of the crus 4, thus precluding the prosthesis from being flexed during the supporting phase of the pace and rendering the prosthesis a stable static support capable of taking up compressive and bending stresses.

As a result of elastic strain, the damper 8 acquires some quantity of energy so as to release the stationary position of the prosthesis at the moment it is raised over the bearing surface in the following phase of the pace. Moving the prosthesis out of its stationary state results from the interaction of the active stump forces and the elastic forces of the damper 8, with a minimal consumption of the patient's intrinsic energy.

Thus, the patient is in an active interaction with the stump-receiving sleeve 1 and further, via the thigh frame 2, the link 7 and the elastic member 10 he exercises direct coupling with the knee-joint mechanism of the prosthesis, thus ensuring controlled motion of the crural portion of the prosthesis, viz., the crus 4 with the foot, while walking so as to render it possible for the patient to approximate the parameters of motion of the prosthesis with those of the unaffacted extremity at any rythm and charater of gait.

Back coupling of the prosthesis with the patient is effected by virtue of the action of the stump-receiving sleeve whose position corresponds to a definite position of the knee-joint mechanism with respect to, the patient's stump.

The knee-joint mechanism of such a prosthesis increases the functional length of the prosthesis when the latter is transferred over the bearing surface, which necessitates an increase in the overall length of the prosthesis within 1 cm.

This fact requires some of the patient's intrinsic energy to be consumed for raising his own weight and to some extent disturbs the patient's gait from the viewpoint of cosmesis, causing a somewhat increased rocking ot the patient's body in the vertical plane during walking. Nevertheless, high stability margin is ensured by the prosthesis for its knee-joint mechanism so as to involve but a minimum consumption of the patient's intrinsic energy during walking, through which account the prosthesis may be recommended for children or elderly patients, as well as for patients in a weak physical state of health.

When the stump-receiving sleeve 18 of the prosthesis shown in FIGS. 3 and 4, rotates in the forward direction with respect to the high frame 16 its distal end imparts rotary motion via the connection link 21 to the double-arm lever constituted by the drag link 14 and the the arm 20 which, in turn, causes the crus 17 to turn in a direction opposite to that of motion of the stump-receiving sleeve 18 with the result that the drag link 15 moves and the prosthesis flexes in its knee-joint mechanism.

Thus, rotation of the stump-receiving sleeve 18 causes displacement of the drag links 14 and 15 together with the crus 17, to an extent which is equal in magnitude and opposite in direction.

The elastic member 24, as the flexural angle of the prosthesis increases in the knee-joint mechanism, brakes the rotary motion of the drag link 14 and the crus 17, thus acquiring an amount of energy so as to impart reverse rotary motion (i.e., forward) to the crus 17 and the drag link 14. The elastic member 24 renders smooth the rotary motion of the crus 17 smooth at the final stage of the flexure of the prosthesis as well as ensuring timely delivery of a force impulse for the crus to enable the latter to perform rotary return motion with respect to the thigh frame 16 in a forward direction.

The dampaer 23, during the final stage of the prosthesis extension, interacts with the retainer 22 so as to ensure smooth contact between the crus 17 and the thigh frame 16 and to fix the position of the former relative to the latter, thus preventing the knee-joint mechanism from recurvation.

Backward motion of the distal portion of the stump-receiving sleeve 1 depends upon the degree of compression of the damper 23. Optimum angular parameters between the stump-receiving sleeve 18, the link 21 and the drag line 14 ensure the stable position of the knee-joint mechanism during the supporting phase of the pace, thus rendering the prosthesis to be held in a stable support which is capable of bearing compressive and bending loads.

As a result of elastic strain, the damper 23 acquires some amount of energy to release the stable position of the knee-joint mechanism at the moment when the prosthesis is raised above the bearing surface (at the final supporting phase of the pace), for enabling performance of the next phase of the pace.

Moving the knee-joint mechanism out of a stable position is effected due to the interaction of the active stump forces and the elastic forces of the damper 23 at a minimum consumption of the patient's intrinsic energy.

The construction of the polycenter knee-joint mechanism of the herein-disclosed prosthesis provides for functional shortening of the overall prosthesis length which is effective within the phase of transferring the prosthesis over the bearing surface. This fact makes it possible to obtain an artificial extremity equal in its overall length to an unaffected leg.

The identity of the overall data decreases the oscillation amplitude of the patient's common center of gravity in the vertical plane which excludes any expenditures of the patient's intrinsic energy for raising his own weight during walking.

The patient is in an active interaction with the stump-receiving sleeve 18 and further, via the link 21 and the drag link 14 he exercises direct coupling with the knee-joint mechanism and ensures controlled motion of the prosthesis crural portion (viz., the crus 17 along with the foot) during walking so as to suit the rhythm and character of his gait, thus approximating the parameters of the prosthesis motion to those of the unaffected extremity.

Through mechanical exertion upon the patient's stump, the patient receives signals informing him of the operation of the knee-joint mechanism, so as to provide for a back coupling of the artificial extremity with the living organism.

The proposed prosthesis may be recommended for use by the patients of all age groups, both male and female, irrespective of their health state, but with due allowance for medical indications.

Both the prosthesis shown in FIG. 1 and illustrated in FIG. 3 may be used in pairs with prosthesis of any other type (in case of bilateral amputation of extremities).

Claims

What is claimed is:

1. A thigh prosthesis, comprising: a thigh frame; a crus having a foot portion; a knee-joint mechanism possessing one degree of freedom of movement connecting said crus to said thigh frame; a retainer protecting said knee-joint mechanism from recurvation; a stump-receiving sleeve having a stump-receiving chamber, said sleeve being kinematically fastened to said knee-joint mechanism and articulated to said thigh frame to permit oscillation of the former in the sagittal plane, said sleeve being fastened to said knee-joint mechanism so that each position of said stump-receiving sleeve with respect to said thigh frame corresponds with a particular position of said crus, said knee-joint mechanism comprising a single-pivot joint interconnecting said crus and said thigh frame; arm means retained in position on said crus so as to form a double arm therewith; and a link articulately interconnecting said arm means and a distal end of said stump-receiving sleeve, said link imparting kinematic movement between the stump-receiving sleeve and the knee-joint mechanism whereby forward motion of said distal end of the stump-receiving sleeve in the sagittal plane with respect to said thigh frame corresponds to a flexure of the prosthesis.

2. A thigh prosthesis as claimed in claim 1, comprising spring means connected to said link for biasing the latter with respect to said stump-receiving sleeve in the direction of extension of the prosthesis.

3. A thigh prosthesis; comprising: a thigh frame; a crus having a foot portion; a knee-joint mechanism possessing one degree of freedom of movement connecting said crus to said thigh frame; a retainer protecting said knee-joint mechanism from recurvation; a stump-receiving sleeve having a stump-receiving chamber, said sleeve being kinematically fastened to said knee-joint mechanism and articulated to said thigh frame to permit oscillation of the former in the sagittal plane, said sleeve being fastened to said knee-joint mechanism so that each position of said stump-receiving sleeve with respect to said thigh frame corresponds with a particular position of said crus, said knee-joint mechanism comprising two drag links forming a four-bar knee-joint mechanism with said thigh frame and said crus, arm means mounted in a position on the front of one of said drag links and forming a double-arm lever with said one drag link; a connecting link articulately interconnecting a movable distable end of said stump-receiving sleeve and said arm means so as to impart kinematic movement between said stump-receiving sleeve and said knee-joint mechanism whereby forward motion of said distal end of the stump-receiving sleeve in the sagittal plane with respect to said thigh frame corresponds to a flexure of the prosthesis.

4. A thigh prosthesis as claimed in claim 3, comprising spring means connected to said connecting link for biasing the latter with respect to said stump-receiving sleeve in the direction of extension of the prosthesis.