GB2114447A - Artificial leg alignment coupling - Google Patents

Abstract

An artificial leg has a thigh (1), a shin (2) which includes a knee mechanism housing (3), and an alignment coupling member (4). The lower end of the thigh is convex and the upper end of the knee mechanism housing is convex. The adjacent upper and lower sides of the coupling member are correspondingly concave. A bolt (5) passes through holes (9A, 4A and 8A) in the parts to connect them adjustably together. The invention permits considerable variation in alignment adjustment while at the same time keeping to a minimum the space occupied in a vertical direction by the coupling member. <IMAGE>

Description

SPECIFICATION Artificial leg alignment coupling This invention relates to an artificial leg having an upper component, a lower component, an alignment coupling member between the upper and lower components, and a connecting means connecting the components together with the coupling member between them.

Various alignment couplings are used in artificial legs to permit adjustment and setting of the alignment of upper and lower leg components. For example, it is known in one above knee leg to dispose the alignment coupling between the upper side of a knee mechanism and the lower end of a thigh component. Alternatively, in a below knee limb the alignment coupling can be disposed between the lower end of a stump socket component and the remaining limb structure which connects the socket component to the foot. Further, in one known alignment coupling, a coupling component has a concave upper face which mates with a convex lower face of the thigh component; also it has a plane lower face which mates with a plane upper side of the knee mechanism.This known alignment coupling permits various adjustment movements to be made, and also takes up relatively little space between thigh component and knee mechanism and in some cases this is an important factor. But this known alignment coupling permits angular adjustment only between the coupling and the thigh component, by virtue of the mating convex and concave faces; it does not permit angular adjustment between the knee mechanism and the coupling. Another disadvantage of this known alignment coupling is that, to obtain offset of the respective vertical axes of thigh component and knee mechanism (and with the latter, the shin component), it is necessary to move the coupling and knee mechanism relatively sideways, and this can interfere with the continuous external cosmesis which is nowadays used.

In other known constructions, variation of the angle at both the thigh component and knee mechanism interfaces with an alignment coupling is possible, but these other known constructions do not allow for the important minimum spacing between thigh component and knee mechanism, as well as having the further disadvantage of a more complex construction.

It is an object of this invention to provide an artificial leg which avoids as far as possible the above-mentioned disadvantages.

According to this invention there is provided an artificial leg having an upper component, a lower component, an alignment coupling member between the upper and lower components, and a connecting device connecting together the components with the coupling member between them, characterized in that i) the lower end of the upper component and the upper end of the lower component are each convexly curved; ii) the coupling member has upper and lower sides which are each concavely curved so as substantially to match the curvature of the respective convexly curved ends; iii) the said ends and the coupling member have apertures through which the connecting device passes; and iv) the sizes of the said apertures in the said ends are such as to permit adjustment of the relative positions of the upper and lower components. The artificial leg may be an above knee leg or a below knee leg.The connection device may be a bolt or stud which passes through the apertures to clamp the two components and the coupling member together in a required alignment. Thus simply by loosening the bolt or stud and manipulating the two components and the coupling member as required, various adjustments of position can be made. Thus for example by oppositely adjusting the respective angles at the upper and lower sides of the coupling member, the upper and lower components can be offset, with little or no effect on the external cosmesis. The several convex and concave surfaces are preferably part-spherical.

Although the invention is of particular use at the knee-thigh level in an artificial leg, it can also be used at other levels, for example, for through-hip, through-knee, and Symes amputations.

Between the two convexly curved component ends the coupling member can be of small thickness; this is particularly useful for cases in which the available height is small. On the other hand, should greater spacing between the upper and lower components be required, a coupling member which is longer in the vertical direction can be used.

Embodiments of the invention will now be described by way of example, with reference to the drawings, in which: Figure 7 is a section on an anterior-posterior plane of an above knee artificial leg; Figure 2 is a rear elevation of a knee mechanism housing seen in Figure 1; Figure 3 is a section similar to that of Figure 1, but of a below knee artificial leg; and Figure 4 is a side elevation of a modified coupling member.

Referring to the drawings, Figure 1 shows an embodiment of artificial leg for above knee amputation. It has an upper or thigh component 1, a lower or shin component 2 with a knee mechanism housing 3, and an alignment coupling member 4. A connection device in the form of a bolt 5 clamps the parts 1, 3 and 4 together in a desired position of adjustment of thigh and shin components.

In Figure 1 the components 1 and 2 are shown in the position of maximum anterior linear shift, and of maximum flexion of the thigh component relative to the shin component 2. "Maximum anterior linear shift" refers to the maximum amount of forward (i.e.

to the right in Figure 1 ) adjustment movement of the normal vertical thigh axis 1A relative to a vertical plane 3B through the knee axis 3A. "Maximum flexion" refers to the angle between the normal vertical thich axis 1A and the actual thigh axis 1A1 seen in Figure 1. The "linear shift" and the "flexion" adjustments are achieved by virtue of the bolt 5 passing through i) an aperture 8a in the lower, convexly curved end 8 of the thigh component 1, ii) an aperture 9A in the upper, convexly curved end 9 of the knee mechanism housing 3 (which is fixed on the shin component 2), and iii) a clearance hole or aperture 4A in the coupling 4. The apertures 8A and 9A are preferably circular and as will be understood from the Figure are each of considerably greater diameter than that of the bolt 5.It will be further understood that after loosening a nut 5A, the components 1 and 2+3 can be adjusted to a required position of alignment, upon which the nut 5A is again tightened, to fix the components in the required position. By virtue of the circular holes, adjustment may also be made in the medial-lateral plane, as indicated by the angles A & B in Figure 2.

Referring again to Figure 1, which shows the maximum possible anterior linear shift in the anterior-posterior direction, it will be appreciated that with a smaller amount of such linear shift or with no linear shift, a somewhat greater amount of maximum flexion can be achieved. With maximum linear shift, 50 of flexion can be achieved in the embodiment shown, but with no linear shift, 8 of flexion can be achieved.

The housing 3 contains a knee mechanism (not shown) of known construction. A patella member 6 bears against the inside of the artificial leg covering or cosmesis 7, which is of known type. The patella member 6 is pivotally mounted at 6A in the shin component 2 and a spring 6B which engages both the component 2 and the member 6, causes the member 6 to engage a cam surface 6C of the housing 3, so that as the leg is flexed about the axis 3A, the patella member 6 is retracted. This arrangement improves the appearance of the cosmesis.

A known knee control mechanism 10 is mounted between pivots 1 or, 1 or. It can be one of various types, fluid or mechanical, and provides swing phase control of the leg or locking of the leg against flexion about the knee.

In the embodiment of Figure 1 the convexly curved upper end 9 of the lower component is formed by a cap portion of the knee mechanism housing 3. A slot 9B permits insertion of a tool for loosening or tightening the nut 5A, which engages a washer 9C of sufficient diameter always to engage the end 9 around the aperture 9A.

The alignment coupling member 4 is formed by an upper part 4B and a lower part 4C removably connected together by studs 4D. The parts 4B and 4C are circular discs of dished form, as shown, to provide concavely curved upper and lower surfaces of the coupling member 4. It will be seen that the vertical height of the member 4 is very small, so that the coupling member 4 occupies little space between the ends 8,9 of the components 1,2, respectively. Each coupling member part 4B, 4C is recessed at 11 (see also Figure 4) to receive a respective layer 12 of anti-slip material. Each layer 12 is concavely curved, as shown. The bolt 5 has a hexagonal head 13 which engages a circular, dished washer 14 which is also of sufficient size always to engage the end 8 around the aperture 8A. The bolt 5 is preferably fixed to the washer 14 by threading 13A and by adhesive (not shown).

The convexly curved surfaces of the ends 8, 9 and the concavely curved surfaces of the coupling member 4 are preferably, but not necessarily, part spherical. The centre of curvature of the end 8 is indicated at 15 on the thigh axis 1A.

Movement of the curved end surface 8 on the coupling member 4, allowed by movement of the bolt 5 within the aperture 8A when the nut 5A is loosened, permits angular adjustment of the thigh component 1 (flexion, extension, abduction, adduction) and rotation about its axis. Movement of the curved end surface 9 on the coupling member 4, allowed by movement of the bolt 5 within the aperture 9A permits extension stop adjustment to the knee mechanism. Combined movement on both surfaces 8 and 9 provides linear shift of the axis of the thigh component 1 relative to the shin component 2. Varying adjustments between thigh and shin components can provide combinations of angular adjustment and linear shift in both the anteriorposterior and medial-lateral planes and relative rotation of thigh and shin components, as required to suit the patient.

The aperture 8A is preferably larger than the aperture 9A, to provide flexion adjustment at the limit of linear shift. The centres of the apertures 8A, 9A can be offset from the longitudinal axes of the components 1 and 2, so that the available range of adjustment can be best used in meeting the normal requirements of the prosthesis. Thus, in Figure 1,the centres of the apertures 8A, 9A lie on the anteriorposterior planes through the longitudinal axes of components 1, 2, but the centre of the aperture 9A lies in front of the vertical plane 3B through the knee axis 3A.

The alignment coupling in the artificial leg of this invention gives the positional adjustments required between a thigh stump socket and the adjacent distal limb structure. In the present embodiment this distal structure is the knee mechanism and shin component of an above knee leg, but the coupling could be used at other levels, for example below knee. For an above knee leg it may also provide extension stop adjustment, which need not therefore be provided in the knee mechanism.

Accommodation of stump length is always a problem, particularly when coupled with finite size of components within the knee mechanism. The present invention can provide for the required adjustments with a minimal height penalty. Linear shift is provided by using combined angular movements instead of a plane sliding movement. This makes the provision of a smooth cosmesis, in cases of maximum adjustment, easier within a continuous cosmesis. The use of a single coupling member between the two curved sliding surfaces, which member is coupled by a single connection bolt or stud, minimises the height used.

An embodiment of the invention applied to a below knee leg is shown in Figure 3. This is generally similar to the embodiment of Figure 1, except that different upper and lower components 21, 22 are used. There is of course no knee mechanism and the convexly curved upper end 9 is formed on the lower component 22. The upper part 4B of the member 4 is smaller than in the embodiment of Figure 1, as is the washer 14.

Figure 4 is an elevation of a coupling member 4 as used in the embodiment of Figure 3, but with a spacer 23 between the coupling parts 4B, 4C, to increase its height in cases where this is necessary.

A like spacer could be used if required in the coupling member 4 of the embodiment of Figure 1.

Spacers of different sizes, and more than one spacer, could be used. When a spacer or spacers is or are used, a longer bolt 5 would be used.

Claims (11)

1. An artificial leg having an upper component, a lower component, an alignment coupling member between the upper and lower components, and a connecting device connecting together the components with the coupling member between them, characterized in that i) the lower end of the upper component and the upper end of the lower component are each convexly curved; ii) the coupling member has upper and lower sides which are each concavely curved so as substantially to match the curvature of the respective convexly curved ends; iii) the said ends and the coupling member have apertures through which the connecting device passes; and iv) the sizes of the said apertures in the said ends are such as to permit adjustment of the relative positions of the upper and lower components.

2. An above knee artificial leg according to claim 1 characterized in that the lower component is a shin, the convexly curved upper end being formed on a knee mechanism housing.

3. A below knee artificial leg according to claim 1 characterized in that the lower component is a structure connecting the upper component to a foot, the said convexly curved upper end being formed on the said structure.

4. A leg according to claim 1 characterized in that the respective curvatures of the said lower end the said upper end, and the upper and lower sides of the coupling member are part spherical.

5. A leg according to claim 1 characterized in that the apertures in the said ends are circular.

6. A leg according to claim 5 characterized in that the aperture in the said lower end is of greater diameter than that in the said upper end.

7. A leg according to claim 1 characterized in that the coupling member comprises upper and lower parts, the upper part having a concavely curved upper side and the lower part having a concavely curved lower side.

8. A leg according to claim 7 characterized by the provision of a spacer between the upper part and the lower part.

9. A leg according to claim 1 characterized in that the respective concavely curved upper and lower sides of the coupling member each has a layer of non-slip material mounted thereon.

10. A leg according to claim 1 characterized in that the connecting device comprises a headed bolt with a nut, one of the components having an aperture for insertion of a tool for loosening or tightening the nut.

11. An artificial leg constructed and arranged substantially as herein described and shown in the drawings.