Patent Application
20080188948
The present invention relates generally to liner systems for use in a prosthetic limb and method for using and making the same.
Prosthetic limbs for amputees and limb deficient individuals require an interface between the residual limb and attachment point, or socket, of the prosthetic device in order to provide proper function. A user may place considerable force against a prosthetic limb such as during walking. Pressure and friction from the wall of the socket on the residual limb can severely damage soft tissue and skin. A cushioned liner between the residual limb and the rigid socket of the prosthetic limb into which it is fitted is needed to protect the residual limb from damage. There exists a need for a liner for a prosthetic limb that provides cushioning and support for a residual limb.
A first aspect of the present invention provides a prosthetic limb socket liner system comprising:
a compressible foam insert, said insert comprising an opening and a substantially cylindrical hollow interior defined by an interior insert surface, said opening and said hollow interior configured to accept a substantial portion of a residual limb; and
a laminar pocket substantially covering said foam insert, said pocket comprising an open proximal end and a closed distal end, said open proximal end and said concave interior being configured to accept a substantial portion of said compressible foam insert, said exterior being configured to substantially fit into a socket of a prosthetic limb.
A second aspect of the present invention provides a method for cushioning a residual limb in a prosthetic socket comprising:
providing a compressible foam insert, said insert comprising a substantially cylindrical hollow interior defined by an interior insert surface and an opening, said opening and said hollow interior configured to accept a substantial portion of a residual limb;
inserting a distal end of said residual limb through said opening and into said hollow interior such that said limb substantially fills said hollow interior;
providing a socket of a prosthetic limb, said socket comprising a substantially concave interior and opening wherein said opening and said concave interior are configured to accept a substantial portion of said compressible foam insert, wherein said concave interior is defined by a concave laminar pocket; and
inserting said distal end of said residual limb with said foam insert into said concave interior of said socket of said prosthetic limb, such that said foam insert with said residual limb substantially fills said concave interior.
A third aspect of the present invention provides a method for forming a prosthetic socket liner comprising:
forming a first negative casting of a residual limb;
forming a first model of said residual limb from said first negative casting of said residual limb, said first model having an exterior surface, wherein said exterior surface substantially conforms to an exterior surface of said residual limb;
forming a first liner from said first model of said residual limb, said first liner having an opening and a first hollow interior substantially conforming to an exterior surface of said first model of said residual limb, wherein said first liner comprises a first material;
donning said first liner over said residual limb, wherein said residual limb substantially fills said first hollow interior;
forming a second negative casting, wherein said second negative casting is a casting of said first liner while said first liner is donned over said residual limb;
forming a second model of said second negative casting, said second model having an exterior surface substantially conforming to an exterior surface of said second negative casting;
forming a second liner from said second model, said second liner having an opening, an exterior defined by an exterior surface, and a second hollow interior defined by a second interior surface, said second interior surface substantially conforming to an exterior surface of said second model, wherein said second liner comprises a second material; and
adhering cover layers to said second interior surface and said second exterior outside surface of said second liner.
Various embodiments of the present invention will be described in detail, with reference to the following figures, wherein like designation denote like members wherein:
The features of the invention are set forth in the appended claims. The invention itself, however, may be generally understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings.
Although certain specific embodiments of the present invention will be shown and described in detail, it should be understood that generalizations and various changes and modifications may be made without departing from the scope of the appended claims. The scope of the present invention will in no way be limited to the number of constituting components, the materials thereof, the shapes thereof, the relative arrangement thereof, etc. Some features of the present invention are illustrated in detail in the accompanying drawings, wherein like reference numerals refer to like elements throughout the drawings. Although the drawings are intended to illustrate an embodiment of the present invention, the drawings are not necessarily drawn to scale.
A need for the present invention may relate to the loss of soft tissue of an amputee's residual limb with liner systems for prosthetic limbs which may employ an individual foam or silicone gel elastomer liner, for example. The loss of soft tissue may be a major contributor to the breakdown of the skin of the residual limb due to the tremendous pressures exerted against the surface of the residual limb, which may lead to fluids being forced out of the tissues, and may lead to cyst growth and infection. The use of a multi-layered system as described within the scope of the present invention may prevent or limit loss or damage to tissues and related injuries.
The compressible foam insert 201 may have a substantially cylindrical hollow interior 308 defined by an interior insert surface 309 and opening 310, where the opening 310 and the substantially cylindrical hollow interior 308 may be configured to accept a substantial portion of a residual limb. Such a configuration may be achieved, for example, by forming a casting or model of a user's residual limb and molding the foam insert from the casting to provide a substantially precise fit for the user. A precise socket liner fit may assist with eliminating gaps between the liner and the user's residual limb, wherein such gaps may be exacerbated by residual limbs which are invaginated or bony and have protruding areas. Gaps between the residual limb and the liner can cause tissue damage to the residual limb due to shear stresses and shock during use of a prosthetic. The compressible foam insert 201 may provide cushioning to absorb shock to the residual limb while using a prosthetic limb, and may have a sufficiently low percent compression set such that extended use does not eliminate the cushioning benefits. Processes such as thermoforming and compression molding, for example, may be used to mold the insert 201 if it is comprised of thermoplastics. Thermoset materials may be cast from a reaction of their precursor materials to form the insert 201.
The first elastomeric fabric layer 306 and second elastomeric fabric layer 302 may be made from nylon, cotton, polyester, and/or the like, or combinations of these. For instance, the first elastomeric fabric layer 306 and second elastomeric fabric layer 302 may be a woven blend of nylon, cotton, or polyester, with a fiber-forming substance which may be a long chain synthetic polymer comprised of at least 85 percent of a segmented polyurethane, such as spandex. Examples of spandex may include LYCRA and ELASPAN. Other synthetic and natural fibers may be suitable for blending with the long chain synthetic polymer comprised of at least 85 percent of a segmented polyurethane, to provide an acceptable elastomeric fabric for the elastomeric fabric layer. The first elastomeric fabric layer 306 may further comprise a moisture-wicking synthetic fabric design of nylon or polyester, such as COOLMAX. The flexible polymer layer 303 may add axial rigidity to the socket liner 202 to aid in donning, and may allow radial flexibility for fitting the liner 202 over contours of a residual limb which may protrude.
The flexible polymer layer 303 may comprise a material such as polyurethane, silicone, silicone gel elastomer, thermoplastic elastomer, combinations of these, and the like, to provide suitable flexibility for a socket liner system 202 using this material. The flexible polymer layer 303 may have a thickness in a range from about 3 mm to about 6 mm. An acceptable Durometer hardness range for the flexible polymer layer 303 may be in the range from about 20 to about 70 on the Shore A hardness scale, or may be in the range from about 5 to about 70 on the Shore 00 hardness scale.
The compressible foam insert 201 may comprise a material such as polyurethane, polyethylene, poly(vinyl chloride) (PVC) closed cell foam, a viscoelestic polyurethane foam such as ISOFORM, a closed-cell crosslinked polyethylene foam such as PELITE, ALIPLAST or PLASTAZOTE, PVC-nitrile rubber foam such as ENSOLITE, a combination of these materials, and the like. The foam insert may be sufficiently compressible to absorb shock during use and sufficiently resilient to substantially return to its original thickness (releasing any compression set) when weight or pressure from an artificial limb and/or socket is removed.
The first elastomeric fabric layer 306 may provide a comfortable interior surface for a user where a portion of the laminar pocket 200 may be exposed to the skin of the residual limb, such as when the foam insert 201 has a cut-away section (203 in
The materials used within the scope of the present invention may contain mineral oil, vitamins, or a combination of these. Such additives may be absorbed by the skin of the user and may sooth and protect the tissue of the residual limb of the user.
The socket liner system 202 may further comprise a woven fabric sock 409 as in
The woven fabric sock 409 may be impregnated or infused with an elastomer by infusing the material with the elastomer while it is in a molten state, while it is being formed from its reactant materials, while it is dissolved in a suitable solvent, a combination of these, or any other means for infusing the elastomer into the woven fabric of the sock 409. When the liner system 202 is in use, the infused elastomer within the woven fabric of the sock 409 may provide a flexible cushion as it may be compressed into and fill small gaps remaining between the compressible foam insert 201 and prosthetic socket 406. Gaps between the insert 201 and socket 406 may be a source of jarring or shock to a user, such as during walking with a prosthetic limb on a lower extremity such as a foot or leg, or when pushing or lifting with an upper extremity prosthetic limb. Filling such gaps with a shock absorbing elastomer may alleviate the jarring and prevent damage to the residual limb and associated tissue.
The woven fabric sock 409 may comprise cotton, nylon, linen, polypropylene, neoprene, rayon, silk, wool, cellulose acetate, acrylic, polylactide, aromatic polyamide, polyester, a combination of these, and the like. Moreover, the woven fabric sock 409 may be impregnated or infused with an elastomer such as a thermoplastic elastomer, an elastomeric gel, natural rubber, latex, silicone, neoprene, butyl rubber, polyurethane, a block copolymer, a combination of these, or any other polymer having elastomeric properties. The infused elastomer may be of a sufficient durometer, molecular weight, and crosslink density such that it is permanently infused within the woven fabric sock 104 and allows elastic flexibility and cushioned support. An acceptable Durometer hardness range for the elastomer infused in the woven fabric layer 104 may be in the range from about 5 to about 75 on the Shore 00 hardness scale.
Step 503 provides forming a first liner from the first model of the residual limb. The first liner may be formed from a material such as polyurethane, polyethylene, poly(vinyl chloride) (PVC) closed cell foam, a viscoelestic polyurethane foam such as ISOFORM, a closed-cell crosslinked polyethylene foam such as PELITE, ALIPLAST or PLASTAZOTE, PVC-nitrile rubber foam such as ENSOLITE, a combination of these materials, and the like. The first liner material may be sufficiently compressible to absorb shock during use, and sufficiently resilient to substantially return to its original thickness (releasing any compression set) when weight or pressure from an artificial limb and/or socket is removed. Processes such as thermoforming and compression molding, for example, may be used to form the first liner if it is comprised of a thermoplastic. Thermoset materials may be formed from a reaction of their precursor materials to form the first liner.
Step 504 provides donning the first liner over the residual limb such that the residual limb substantially fills the interior of the first liner. In step 505, a second negative casting may be formed from the first liner while it is worn over the residual limb. Forming the casting may be accomplished in a similar fashion to step 501.
Step 506 provides forming a second model of the second negative casting. The second model may have an exterior surface that conforms to the exterior surface of the second negative casting.
Step 507 provides forming a second liner from the second model, such that the second liner may have an opening, an exterior surface, and a hollow interior. The hollow interior of the second liner may have an interior surface that conforms to the exterior surface of the second model. Since the second model may conform to the exterior surface of the first liner while being worn on the residual limb, the interior of the second liner may be configured to accept the first liner. The second liner may comprise a flexible polymer layer which may be comprised of a material such as polyurethane, silicone, a thermoplastic elastomer, silicone rubber, latex, a combination of these, and the like. An acceptable Durometer hardness range for the second liner 303 may be in the range from about 20 to about 70 on the Shore A hardness scale, or may be in the range from about 5 to about 70 on the Shore 00 hardness scale.
In Step 508, flexible cover layers may be adhered to the interior and exterior surfaces of the second liner, where the cover layers may substantially cover the interior and exterior surfaces of the second liner. The cover layers may be elastomeric fabric, an elastomer, copolymer, or combinations thereof. The cover layers may be adhered using an adhesive such as a solvent-based adhesive, water-based adhesive, hot-melt, epoxy, and the like which may bond to both surfaces. The adhesion may utilize a thermal process, or any other means for adhering the cover layers to the liner surfaces. The cover layers and second liner material may be bonded together during their formation from their reactant materials, such as in an example where the second liner is a urethane layer which is bonded directly onto either of the cover layers during the polymerization reaction to form the urethane layer. The layers may be bonded by melting or during a thermoforming process, such as with a thermoplastic elastomer (TPE) as the second liner material. In such a case, the TPE may melt, flow, and physically attach to the cover layer. The cover layers may be placed over the surface of the second model prior to forming the second liner, which may provide a means for adhering the cover layers to the interior of the second liner if the material comprising the second liner is sufficiently melted to adhere to the cover layers. Adhesive may be applied to the cover layers after they are placed on the second model surface, and then the second liner may be formed onto the adhesive layer. Prior to adhering, the surfaces to be adhered may be pretreated to promote adhesion, such as with a plasma, corona, flame, ozone, chemical adhesion promoter, or similar surface activation technique.
In another embodiment within the scope of the present invention, the second liner may be adhered to the interior surface of a prosthetic socket of a prosthetic limb, using the adhesive and adhering methods above. In such a case, the cover layer on the exterior surface of the second liner may be omitted from the second liner and the flexible polymer layer may be adhered directly to the interior surface of the socket. The socket may comprise polymer laminates with materials such as fiberglass, nylon, polyester fiber such as the polyethylene terephthalate fiber DACRON, carbon fiber, polyaramid fiber such as KEVLAR, ultra high molecular weight polyethylene fiber such as SPECTRA, polypropylene, epoxy resin, epoxy adhesive, combinations thereof, or any other material which may provide sufficient strength to the prosthetic limb socket so that the limb may withstand the forces associated with use.
In step 701, a third negative casting may be made of the residual limb donned with the first and second liners using methods such as those described in step 501. In step 702, a third model may be made from the third negative casting using methods describe above in step 503, where the third model has an exterior surface that substantially conforms to the exterior surface of the residual limb donned with the first and second liners. In step 703, the test socket is formed from the third model by thermoforming a socket from materials such as polyacrylics, polyolefins, thermoplastics, combinations thereof, and the like. In step 704 the residual limb donned with the first and second liners and then inserted into the test socket. The fit of the test socket may be determined in step 705 by noting the user's comfort and control of the prosthetic limb during use. In step 706 the fit may be adjusted by the removal or addition of material to the outer surface of the liner, or the inner surface of the test socket. The final socket may formed in step 707 by making a socket model from the interior of the test socket, and forming the final socket from the socket model.
The socket model may be made using the methods above for the first, second, and third models, such as with plaster of Paris for example. The final socket may comprise polymer laminates with materials such as fiberglass, nylon, carbon fiber, polyaramid fiber such as KEVLAR, ultra high molecular weight polyethylene fiber such as SPECTRA, polypropylene, epoxy resin, epoxy adhesive, combinations thereof, or any other material which may provide sufficient strength to the prosthetic limb socket so that the limb may withstand the forces associated with use.
The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teaching. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of this invention as defined by the accompanying claims.
