GB2098072A

GB2098072A - Improved endo-skeletal artificial limb

Info

Publication number: GB2098072A
Application number: GB8208381A
Authority: GB
Original assignee: Chas A Blatchford and Sons Ltd
Current assignee: Chas A Blatchford and Sons Ltd
Priority date: 1980-09-25
Filing date: 1981-09-10
Publication date: 1982-11-17
Also published as: FR2494987A1; DE3137684A1; US4463459A; GB2098072B; FR2494987B1; FR2502940A1

Description

1

SPECIFICATION

Improved endo-skeletal artificial limb be a compromise governed by the conflicting requirements of providing a sleeve which is sufficiently flexible such that movement of the knee joint is not impeded and at the same time is sufficiently durable. It must also maintain an appearance which approximately matches that of a natural limb in both the flexed and extended positions of the knee joint.

It is an object of this invention to provide an artificial leg in which these requirements are satisfied to a greater extent than previously.

It is a further object of this invention to provide means which reduces the amount of deformation which a plastics foam covering sleeve must undergo in the knee region when the leg is flexed at the knee.

According to this invention there is provided a jointed endo-skeletal artificial limb having a foam covering disposed over the joint and having a structural member in the region of thejoint, wherein a movable member is connected to the structural member in the region of the joint, the movable member being disposed in such manner that it determines the external shape of that part of the foam covering which projects outwardly from the joint when the artificial limb is in its flexed position.

The artificial limb may have a tubular plastics foam covering, which is formed of at least two elon- gate cover portions whose mating surfaces extend in the generally longitudinal direction of the limb, the GB 2 098 072 A 1 shape of at least one of the elongate cover portions, before formation of the covering, being such that the completed tubular covering is subjected predomin antly to compressive rather than tensile forces over This invention relates to an artificial limb and more its normal range of flexion.

particularly although not exclusively to an endo- The plastics foam covering may comprise an skeletal artifical leg. An endo-skeletal leg is one in anterior cover section and a posterior cover section.

which internal structural members, such as a thigh 70 These two sections are individually moulded so that, socket or socket container and a shin tube, member, prior to being bonded together, the anterior section are enclosed in an outer covering, which may for is shaped to correspond approximately to the flexed example be of plastics foam. leg and the posterior section is shaped to corres It is known to provide an endo-skeletal artificial pond approximately to the leg in its extended posi limb with various types of outer, non-structural cov- 75 tion. When the two sections are brought together, ering. For example, it is known to provide such a the anterior section is subject to compression espe covering in the form of a continuous tubular sleeve cially in the region covering the knee. When the cov of flexible foam material fitted overthe thigh por- ering is fitted to the limb, and the limb is in its tion, the knee portion, and the shin of an artificial leg. extended position the anterior section is compres The advantages of such a sleeve are that it is light in 80 sed and the posterior section is in a relaxed state.

weight and can be made to give the leg a relatively When the knee joint is flexed the compression is M acceptable appearance compared for example with transferred to the posterior section and the anterior an artificial leg in which a cosmetic covering has a section moves towards its natural unstressed posi gap at the knee. However the main disadvantage of tion.

the known continuous foam sleeve is its susceptibil- 85 Therefore this covering has the advantage over ity to wear and deterioration in the knee region due known foam coverings that it is not subjected to to repeated flexing of the knee joint, which causes damaging tensile stress over a substantial range of alternate tensioning and compression of the foam movement of the leg, so reducing the rate of deterio material. The plastics foam material which are most ration of the foam material.

suitable for a cosmetic sleeve are generally much 90 As referred to above, a jointed endo-skeletal artifi weaker when subjected to tensile stress than when ciai limb with a foam covering disposed over the compressed. It is therefore the stretching of the foam joint has a movable member which is attached to a material over the internal structural members which structural member of the limb in the region of the tends to cause deterioration of the sleeve. joint. In an artificial leg this movable member may The design of such a limb covering sleeve tends to 95 be a patella member which moves towards the knee joint axis as that joint is flexed. This has the effect of reducing the extent to which the foam covering on the anterior side of the joint has to be deformed as the joint is moved to and fro between the fully extended and fully flexed positions. In the preferred embodiment the patella member is generally semicircular when viewed in the medialllateral direction and is pivotally attached to the shin. The rounded surface of the member is in contact with the inner surface of the foam covering and creates a projecting area which simulates the front of the natural knee. As the knee joint is flexed the patella member slides over a cam surface of reducing radius relative to the joint axis so that the patella member effec- tively retracts, so reducing the deformation of the covering. The patella member also acts as a kneeling member. Alternatively, the patella member may be linked to a point in the thigh above the knee axis. A further feature of the preferred embodiment is the provision of a recess or cut-out in that part of the covering which lies in the angle of the limb when the joint is flexed. Such a reduction in the amount of foam material in this region minimises the possibility of "bunching" of the foam covering which, apart from being unsightly, may prevent full flexion of the knee joint or may cause premature failure of the covering. The invention will now be described by way of The date of filing shown above is that provisionally accorded to the application in accordance with the provisions of Section 15(4) of the Patents Act 1977 and is subject to ratification or amendment at a later stage of the application proceedings.

2 GB 2 098 072 A 2 example, with reference to the drawings, in which:Figure 1 is a vertical central section of an artificial leg in accordance with the invention, with the thigh portion cut away at its upper end; 5 Figure 2 is an enlarged detail section of part of the 70 anklejoint; Figure 3 is an enlarged section of a front or anterior covering portion; Figure 4 is an enlarged section of a rear or post- erior covering portion; Figure 5 is an enlarged section of the whole covering, with the two portions of Figures 3 and 4 bonded together; Figure 6 is a top plan view as seen in the direction of the arrow 'W' in Figure 5; Figure 7 is an enlarged side elevation of a knee chassis; and Figure 8 is a front elevation of the knee chassis of Figure 7.

Referring to Fig. 1 an endo-skeletal artificial leg 85 has a plurality of main internal structural compo nents comprising:

a polypropylene thigh socket container 1, the top part of which is cut away and not shown; a convex alignment plate 3 bolted to the base of 90 the socket container 1; a knee chassis 4 with a concave spherical cup 5 which interfaces with the alignment plate 3; the knee chassis 4 is attached to the alignment plate 3 by a central clamp bolt 5A; the chassis 4 has a curved cam surface 6 of decreasing radius relative to the knee joint axis 7, and a rear pivotal attachment 8 for a knee lock device, which is indicated diagrammati cally at 9; a carbon fibre shin member 10 which is movable angularly about the knee joint axis 7 from the extended position shown in Figure 1; the shin member 10 has a pivotal attachment point 10A for a movable patella member 11 which slides overthe cam surface 6 as the shin member 10 moves 105 about the knee axis 7; an ankle assembly comprising a ball and socket joint which connects the shin member 10 to a foot, the socket having upper and lower socket portions 15,16 which fit around a ball 18, the upper socket portion 15 being connected to the shin member 10 and the two socket portions 15,16 being connected together by, and clamped around the ball 18 by, a rotatable sleeve-like turnbuckle ring member 17, which, on rotation in one direction, causes the two socket portions 15,16 to move towards each other to clamp the ball 18. Between the ball 18 and socket portions 15,16 is a rubber lining 18A. (The relatively large size of the ball and socket joint in the ankle region will be noted). The ball 18 is mounted on a peg 19 having a serrated lower surface 20; and a foot keel 21 in the form of a carbon fibre box section which is adjustably mounted on the peg 19; the keel 21 has a forward extension 22.

The several structural members of the leg are surrounded by a continuous flexible foam covering or sleeve 23, described below with reference to Figures 3 to 6. The covering 23 extends from the socket container 1, over the knee joint and the shin, and is bonded to the upper surface 24 of the foot. The foot is also of endo-skeletal construction and has a body 25 of relatively stiff foam enclosing the keel 21. A part 26 of relatively soft foam is provided in the heel. The whole leg has an outer flexible cover 27 of a silicone sheet material.

Referring to Figs. 3 and 4, the cosmetic covering 23 is formed from two cover sections 28,29 which are individually moulded in the shapes shown. The anterior section 28 (Figure 3) is moulded such that in its unstressed condition it corresponds approximately to the shape of the leg in a partly flexed portion. Conversely the posterior section 29 (Figure 4) is moulded without the angle of the section 28, i.e. its shape corresponds to the leg in its extended posi- tion.

To produce the complete covering 23 shown in Fig. 5, the two sections 28 and 29 are bonded together along the longitudinally extending surfaces 30 and 31 (see also Fig. 6), with the result that the section 28 is compressed in the region of the knee.

The inner moulded surface 32 of the covering 23 corresponds to the shape of the structural components of the limb. The outer surface 32A is a temporary surface and is trimmed down by for example linishing to produce the required final exterior surface 33 indicated by dotted lines in Fig. 5. The ends of the covering 23 are then trimmed to length as also indicated by dotted lines and some foam material is removed from the region behind the knee by form- i rig a cut-out 34 as shown.

The covering 23 is then ready to befitted over the structural components as shown in Fig. 1.

Referring now to Figures 1, 7 and 8, the knee chassis 4 and movable patella member 11 will now be described. The knee chassis 4 has an upwardly extending rim 40 which fits within the cup 5 of the alingment coupling. The chassis has two depending portions 41,42 each formed with the lower curved cam surface 6 referred to above. These portions 41, 42 also have aligned bores 43 for pivotal connection at the knee joint axis 7 of the shin member 10 (see Figure 1). The depending portions 41,42 also have aligned bores 44forthe pivotal attachment 8 of the knee lock device 9. As is seen in Figure 1, a generally semicircular patella member 11 is pivotally mounted at 10A at the upper end of the shin member 10. It has a convex curved front surface 11 B and a concave curved rear surface 11 C, the latter being in sliding engagement with the camming surfaces 6. The front surface 11 B is in contact (as seen in Figure 1) with the inner surface of the plastics foam covering 23 and creates a projecting area 45 which simulates the appearance of a natural knee. As the leg is f lexed about the knee joint axis 7, the patella member 11 slides over the cam surfaces 6 which are of reducing radius relative to the axis 7 so that the patella member 11 becomes retracted, moving rearwardly about its pivotal attachment point 1 OA, and so reducing the deformation of the covering 23. Thus as the

Claims

leg is flexed about the knee joint axis, the motion of the patella member causes the extent of the resultant deformation of the plastics foam covering 23 in the anterior kee region to be reduced. CLAIMS

1. Ajointed endo-skeletal artificial limb having a 1 1 p - i 3 GB 2 098 072 A 3 foam covering disposed over the joint and having a structural member in the region of thejoint, wherein a movable member is connected to the structural member in the region of the joint, the movable member being disposed in such a manner that it determines the external shape of that part of the foam covering which projects outwardly from the joint when the artificial limb is in its flexed position.

2. An artificial leg according to claim 1 wherein the joint is a knee joint and the movable member is a patella member which is movable relatively towards the axis of the knee joint as the joint is f lexed.

3. An artificial leg according to claim 2 wherein the structural member is the shin of the leg and the patella member is of generally semi- circular shape when viewed in the medialllateral direction, the patella member being pivotally attached to the shin.

4. An artificial leg according to claim 3 wherein the rounded surface of the patella member is in con- tact with the inner surface of the foa mcovering so as to create, in the extended position of the leg, a protuberance which simulates the appearance of the front of a natural knee.

5. An artificial limb according to claim 1, having a tubular plastics foam covering which is formed of at least two elongate cover portions whose mating surfaces extend in the generally longitudinal direction of the limb, the shape of at least one of the elongate cover portions, before formation of the covering, being such that the completed tubular covering is subjected predominantly to compressive rather than tensile forces over its normal range of flexion.

6. An artificial leg according to claim 5 wherein the completed covering comprises an anterior cover portion and a posterior cover portion, the anterior portion being moulded to a shape which matches approximately the shape of the flexed leg and the posterior portion being moulded to a shape which matches approximately the shape of the extended leg.

Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd., Berwick-upon-Tweed, 1982. Published atthe Patent Office, 25 Southampton Buildings, London, WC2A lAY, from which copies may be obtained.