GB2166356A - Artificial leg - Google Patents

Abstract

An artificial leg having a covering which is discontinuous in the region of the knee has a thigh component (16) with an end portion comprising a two-part knee ball (14) and an endoskeletal shin component (12) coupled to a knee joint inside the knee ball (14). The internal structural member (12A) of the shin component passes through an anterior-posterior slot between side portions (14A, 14B) of knee ball (14) to allow unobstructed flexion of the limb. The upper part of the shin is surrounded by a rigid shell (22) having an anterior upward extension (22A) which covers the slot when the limb is fully extended or partially flexed. At full flexion, that part of the slot which is no longer covered by the shin extension (22A) is closed by a flap (26) which is connected by an integral hinge to the knee ball (14) at the end of the slot. This flap (26) hinges outwardly behind the shin extension (27A) as the joint is extended to allow the internal member (12A) to reach the end of the slot. Instead of being hinged, the flap may be slidably mounted in either of the components of the limb. <IMAGE>

Description

SPECIFICATION Improvements on artificial limbs This invention relates to an artificial limb and particularly to an artificial limb having a discontinuous cosmetic covering.

One of the advantages of endoskeletal artificial limbs is that they can be provided with a flexible continuous cosmetic covering which covers joints without leaving unsightly gaps. Such a cosmesis is of considerable value for geriatric patients, for female patients, where appearance is important, and for any male patients who require a continuous cosmesis. It is not, however, necessarily the best comesis for very active male patients in particular who require a hard wearing external surface.

An alternative to the flexible and continuous construction is the earlier crustacean construction which at one time was used almost exclusively.

This employs separate parts made of rigid materials, but having a break between the parts at the joint between two relatively movable limb members. Whilst not providing the advantages of the continuous cosmesis, this latter construction does permit the use of hard wearing materials which are more suitable for the active patient. A disadvantage of using a crustacean cosmesis with an internal load bearing structure is the requirement for a recess or slot in one part of the cosmesis at the joint to allow flexion of the limb. For example, in the case of an artificial leg with an internal knee joint, the upper part of the limb may be surrounded by a thigh cosmesis terminating in a knee ball which simulates the shape of the natural knee.

A slot must be provided in the lower part of the knee ball to allow swinging movement of the internal shin member relative to the thigh. With the limb fully extended, this slot is covered by the anterior upper end of the shin cosmesis. However, on flexion of the limb, the slot is revealed at the front of the knee. This is unacceptable both cosmetically and practically, as clothing will tend to catch in any such slot as the knee bends and then subsequently straightens.

The present invention provides an artificial limb comprising first and second limb components coupled together by a joint allowing pivoting of one component with respect to the other, at least the first component having an internal structural member attached to the joint, wherein: the second component has an end portion including two side parts, and an opening or openings between the side parts to allow the structural member or part of the joint to swing between the side parts as the limb is flexed; the first component has a shield portion which overlaps the said end portion of the second component to a varying degree depending on the flexion of the limb; and the limb further comprises a movable cover arranged to close at least a part of the or each opening which would otherwise be exposed beyond an edge of the shield portion during part of the flexion range of the limb.

The side parts may define a single opening there between in the form of a slot, the side parts forming ears on either side of a joint mechanism. The cover preferably comprises a plastics flap attached to the end portion of the second limb component at an end of the slot.

The single slot opening is suited to a uniaxial joint mechanism to allow movement of the internal structural member adjacent the mechanism. However, the joint mechanism may be a multiple bar linkage having links which protrude through, for example two slots arranged side by side in the end portion of the second component.

The invention is primarily applicable to the knee joint of a lower limb prosthesis, in which the shield portion is an upward extension of a rigid shell surrounding the upper part of an internal shin member. The first and second limb components referred to above are the shin and thigh components respectively, and, in the preferred embodiment, the end portion of the thigh component is a rigid polyurethane foam knee ball which encloses an internal joint mechanism such as that disclosed in our British Patent No. 1 534 181. The knee ball is advantageously constructed in two parts, both of which can be removed from the limb to allow access to the joint for making adjustments. Alternative arrangements of cover are possible with the element slidably mounted on the shield portion or the end portion, or mounted for a combination of sliding and pivoting movements.

The invention allows a high strength lightweight internal limb structure to be combined practically with the crustacean construction, and further permits the same range of basic structural components to be used in limbs with discontinuous as well as continuous cosmesis, thus meeting the requirements of most above-knee amputees.

The invention is illustrated by way of example in the attached drawings in which: Figure 1 is a partly sectioned side view of part of an artificial leg for an above-knee amputee with the knee joint fully extended; Figure 2 is a similar view with the knee joint flexed; Figure 3 is an exploded perspective view of a two-part knee ball; Figure 4 is a front view of the leg at full extension; and Figure 5 is a perspective view from the front and to one side with the joint flexed.

Referring to Figures 1 and 2, an endoskeletal artificial leg in accordance with the invention has an internal knee joint defining a transverse axis of rotation 10 about which a shin component 12 having an internal shin member 12A swings from full extension (Figure 1) to a flexed position (Figure 2) and beyond. Covering the joint is a two-part rigid knee ball 14 having a front part 14A and a detachable rear part 14B, which together form a removable end portion of a thigh component 16, the outer surface of the knee ball 14 being flush with the thigh cosmesis. Movement of the shin member 12A relative to the thigh component 16 is controlled in known manner by a swing phase control unit 17 shown by dotted lines in Figures 1 and 2.

Referring to Figure 3, the front part 14A of the knee ball 14, and the lower extremity of the rear part 14b, have an anterior-posterior slot 18 defined by two downwardly depending ears 20A and 20B for allowing the top end of the shin member 12A to rotate inside the knee ball 14.

Fixed to the top of the shin member 12A there is a rigid outer shell 22 flared towards its upper edge to form a hard-wearing shield portion 22A which is exposed at the front of the limb and overlaps the knee ball 14, as shown in Figures 1 and 2. The external shape of the lower limb as a whole is deter mined by a flexible foam cosmesis 24 applied to the outer surface of the outer shell 22 and reaching or approaching the upper edge 22B except in the region of the shield portion. The shield portion 22A overlaps the knee ball to a varying degree depend ing on the flexion of the limb, but although the up per edge 22B is relatively high at the front of the knee, it does not cover the end of the slot 18 at full flexion. This is particularly clear in Figure 5.As shown in Figure 5, this part of the slot 18 is cov ered by a flap 26 attached at its upper edge 28 to the knee ball front part 14A by a hinge. When the limb is flexed the flap 26 lies flush on the edges of the slot, but referring to Figure 2 and then to Fig ure lit will be seen that as the limb is extended the flap 26 is allowed to pivot away from the edge of the slot 18 and to enter a space left between the shin member 12A and the anterior wall of the outer shell 22, thereby uncovering the slot 18 to al low passage of the shin member 12A to the end of the slot. Figure 4 shows the flap 26 in front eleva tion.

Referring to Figures 1 and 2, loose pivoting movements of the flap 26 when it is inside the shell 22 are largely prevented by a resilient biasing strip 12B attached at its lower end only to the in ternal shin member 12A. A plastics material such as polypropylene may be used for the strip 12B and its width may be in the region of 15mm, the degree of resilience being such that a very light load is exerted on the flap 26 to control play.

With regard to materials that may be used for the other parts of the limb described above, the knee ball parts 14A and 14B may be rigid polyure thane foam moldings. The flap 26 may be formed ,from polypropylene, and advantageously has an integral hinge of the same material. The shell 22 is preferably a fibre reinforced plastics laminate or the like.

Alternative arrangements include mounting the flap in grooves in the knee ball so that it can slide up inside the knee ball when the limb is extended.

It could be pushed there by the shin member as the limb extends, and pulled down by the shin member on flexion. In a further variation the flap could slide up outside the knee ball from behind the shield portion.

Claims (16)

1. An artificial limb comprising first and second limb components coupled together by a joint al lowing pivoting of one component with respect to the other, at least the first component having an internal structural member attached to the joint, wherein: the second component has an end portion including two side parts, and an opening or openings between the side parts to allow the structural member or part of the joint to swing between the side parts as the limb is flexed; the first component has a shield portion which overlaps the said end portion of the second component to a varying degree depending on the flexion of the limb; and the limb further comprises a movable cover arranged to close at least a part of the or each opening which would otherwise be exposed beyond an edge of the shield portion during part of the flexion range of the limb.

2. An artificial limb according to claim 1, wherein the cover is mounted on the second component.

3. An artificial limb according to claim 2, wherein the cover is a hinged flap and the first component has a space behind the shield portion for receiving the flap in an outwardly hinged condition when the said part of the or each opening is behind the shield portion.

4. An artificial limb according to claim 1, wherein the cover is slidable in the end portion of the second component.

5. An artificial limb according to claim 1, wherein the cover is slidable in the shield portion.

6. An artificial limb according to any preceding claim, wherein the end portion of the second component comprises a rounded cover for a joint mechanism, the side parts being in the form of ears on respective opposite sides of the mechanism defining there between a single opening in the form of a slot for allowing the structural member to swing between the ears.

7. An artificial limb according to claim 6 when appendant to claim 3, wherein the flap is connected to an end of the slot by a hinge.

8. An artificial limb according to claim 7, wherein the flap is a plastics component and includes the hinge as in integral part of the component.

9. An artificial limb according to any preceding claim, wherein the shield portion forms part of a rigid shell around at least that portion of the said internal member which is nearest the joint.

10. An artificial limb according to claim 6, wherein the end portion of the second component is formed in two parts which are removably attached to each other to allow access to the joint.

11. A lower limb prosthesis according to any preceding claim, wherein the first component is a shin component, the second component is a thigh component, and the joint is a knee joint.

12. A prosthesis according to claim 11, wherein the joint is uniaxial.

13. A prosthesis according to claim 11, wherein the joint is a multiple bar linkage.

14. An artificial limb comprising first and second limb components pivotably coupled together by a joint mechanism, at least one of the components including an internal structural member, wherein the structural member or a part of the mechanism coupled thereto is arranged to swing in an opening or openings in an end portion of the other component when the limb is flexed, wherein the arrangement of the components is such that a part of the end portion defining the opening or openings is exposed at full flexion of the limb, and wherein a movable cover device mounted on one of the said components is arranged to cover the opening or openings in the region of the said exposed part at full flexion.

15. An artificial limb comprising first and second limb components pivotably coupled together by a joint mechanism, at least one of the components including an internal structural member, wherein the structural member or a part of the mechanism coupled therto is arranged to swing in an opening in an end portion of the other component when the limb is flexed, and wherein the said end portion comprises a rounded cover for the mechanism and is formed in two parts which are removably attached to each other to allow access to the mechanism.

16. An artificial limb constructed and arranged substantially as herein described and shown in the drawings.