Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Leg – Foot
Reexamination Certificate
1998-04-03
2001-03-06
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Leg
Foot
C623S027000
Reexamination Certificate
active
06197067
ABSTRACT:
This invention relates to an artificial limb and particularly to a lower limb prosthesis which is inexpensive to manufacture.
Much of the development of artificial limbs has been to produce a prosthesis which is as light as possible yet is strong and functionally sophisticated. As a result, such prostheses tend to use expensive materials and manufacturing techniques. There is a need for a prosthesis which can be manufactured inexpensively and in large quantities, but which is still lightweight, robust, and comfortable to wear and use.
According to a first aspect of this invention, there is provided an endoskeletal artificial limb comprising a load-bearing elongate structural member which is injection-moulded from a thermoplastics material, and has a longitudinal web and at least one integral longitudinal flange arranged transversely of the web. Preferably, at least a portion of the member is straight and of constant cross-section, with at least two integral longitudinal flanges located along opposite edges of the web, the cross-section being of H- or I-shape.
Such a limb can be dimensioned so as to be lightweight, yet strong in terms of resistance to transverse bending moments. It has the additional advantage of having some torsional resilience which, in the case of a lower limb prosthesis, reduces shear forces acting between the amputee's stump and the stump socket.
In a particular embodiment of the invention the artificial limb is a lower limb prosthesis in which the structural member comprises at least a shin portion of substantially constant cross-section. In this particular embodiment, the structural member includes a foot keel with anteriorly and posteriorly extending portions, integrally formed in one piece with the shin portion in a single injection-moulding operation. The keel may have a web extending in the anterior-posterior direction, co-planar and contiguous with the web of the shin portion. The keel may also have a flange extending lengthwise in the sole of the foot, integrally formed at the distal edge of the keel web. The flange extends transversely on both sides of the keel web. Preferably this sole flange is curved in the longitudinal direction of the foot so as to have a convex lower surface.
The keel may extend both anteriorly and posteriorly relative to the shin portion, and may also have upper flanges which, in the case of the shin portion having two longitudinal flanges, are contiguous with those flanges, the upper flanges curving proximally from the foot to merge directly into the flanges of the shin portion.
The portion of constant cross-section preferably extends to the proximal end of the elongate structural member, the limb further comprising a clamp fitted to the said end to enclose the longitudinal web and flange end and for mounting to an upper limb component. The clamp is a thermoplastics component having a recess of a cross-section which corresponds to that of the structural member, the component thereby enclosing the proximal end of the member. The clamp may have cut-outs extending in the longitudinal direction of the structural member on opposite sides thereof, the cut-outs being spanned by respective clamping bolts extending between oppositely directed outer faces of the clamp whereby clamping forces can be exerted by tightening the bolts to pinch the or each flange of the structural member. The or each clamping bolt has the effect of distorting or deforming the material of the clamp to grip the structural member.
Different upper limb components may be attached to the structural member by the clamp. In the case of a lower limb prosthesis, the clamp may be attached to or form a distal part of a knee assembly. Alternatively, it may connect the structural member to a stump socket, with or without an intervening alignment device. If the clamp is required to be detachable from an upper or proximal limb component, it may comprise a clamp housing for the structural member and a proximal plate which forms a bridge on the proximal side of the clamp housing, the bridge being integrally formed with the housing as a single injection-moulded component. Another possibility, in the case of a prosthesis for an above-knee amputee, is to form the upper part of the shin as a knee housing which has an integral clamp housing for receiving the proximal end of the structural member.
In another embodiment, the clamp is replaced by a housing having a recess with a cross-section corresponding to the cross-section of the structural member, the recess being so dimensioned that the structural member is an intimate fit within the recess. The member may be held in place simply by friction, or a latch feature or by an adhesive.
In keeping with the concept of a prosthesis with the minimum number of components and with minimum cost, in the case of a lower limb prosthesis the foot is preferably a unitary foam structure moulded in situ over the foot keel referred to above. The central longitudinal axis of a straight shin portion may pass through the foot at a distance from the extreme posterior end of the foot which is equal to between 0.29 and 0.33 as a proportion of the total length of the foot. More particularly, the proportion is between 0.30 and 0.32.
A toe-break strip made of, for instance, a resilient polyurethane material may be bonded to the distal face of the keel to extend anteriorly of the keel.
With regard to the material of the structural member, this is preferably a fibre-loaded thermoplastics material such as nylon loaded with glass fibres (typically less than 10 mm in length). The proportion of fibres by weight is preferably between 35% and 60%, as a percentage of the total weight of the material.
The above-described limb can be cheaply produced by injection-moulding a limited range of structural members with different keel sizes, and moulding a foam foot in situ over the keel of each member with the member held in a predetermined position relative to the mould for the foot, to form a unitary shin and foot assembly. At the fitting stage, a shin and foot assembly of the required size is selected, the shin portion is cut to a required length and joined at the proximal end to a stump socket or, in the case of a prosthesis for an above-knee amputee, to a knee joint which is, in turn, connected to a socket. An alignment device may be included between the socket and the shin portion. If required, a cosmetic flexible foam covering may be slid over the shin portion.
The invention also includes, according to a second aspect thereof, a method of making an artificial limb comprising selecting a unitary shin and foot assembly having a shin portion comprising a structural member which is injection-moulded from a thermoplastics material and which, over at least a proximal end portion is of constant cross-section having a web and at least one transverse flange, cutting the shin portion to a required length, securing the cut end of the shin portion in a receptacle, and securing the receptacle to a stump socket.
According to a third aspect of the invention, there is provided a shin component for an artificial limb comprising an injection-moulded thermoplastics structural member having a longitudinal web and at least one integral longitudinal flange extending transversely of the web.
According to a fourth aspect of the invention, a component for an artificial limb comprises a shin portion having a longitudinal web and at least one integral longitudinal flange extending transversely of the web, and a foot keel, the shin portion and the keel being integrally formed as a single-piece injection-moulded structural member.
REFERENCES:
patent: 4547913 (1985-10-01), Philips
patent: 4911724 (1990-03-01), Fikes
patent: 4959073 (1990-09-01), Merlette
patent: 5116381 (1992-05-01), Palfray
patent: 5156631 (1992-10-01), Merlette
patent: 5219364 (1993-06-01), Lloyd
patent: 0 454 524 A1 (1991-10-01), None
patent: 690657 (1930-09-01), None
patent: 2 114 447 (1983-08-01), None
patent: 91/15169 (1991-10-01), None
Harris Graham James
Shorter John Jeffrey
Woolnough Victor James
Barnes & Thornburg
Chas. A. Blatchford & Sons Limited
Willse David H.
LandOfFree
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