Artificial limb with an expansible foam stump socket

July 14, 1970

C. L. WELLINGTON

3,520,002

ARTIFICIAL LIMB WITH AN EXPANSIBLE FOAM STUMP SOCKET

Filed Nov. 29, 1967

<img file="US3520002A_D0001.tif" />

<img file="US3520002A_D0002.tif" />

INVENTOR

CHARLES L. WELLINGTON

<img file="US3520002A_D0003.tif" />

United States Patent Office _Palenled

3,520,002 ARTIFICIAL LIMB WITH AN EXPANSIBLE FOAM STUMP SOCKET Charles L. Wellington, 1228 Orion St., Metairie, La. 70005 Filed Nov. 29, 1967, Ser. No. 686,502 Int. Cl. A61f 1/02 U.S. Cl. 3—19 2 Claims

ABSTRACT OF THE DISCLOSURE 10

An artificial limb having a rigid outer shell defining a cavity for receiving a limb stump. A stump socket is carried in the cavity and includes flexible pads positioned adjacent the inner wall of the outer shell of the artificial _lglimb. An expansible foam material is inserted in the cavity in a liquid state, and is capable of expanding into a substantially rigid cellular supporting foam structure. An elastomeric member is positioned on the patient’s limb stump in a stretched state for emphasizing scar tissue and ₂₀bony areas of the limb. The limb stump is inserted within the socket prior to the expandible polymer expanding so that when such expands a rigid cellular supporting structure is produced having a cavity with an inner wall complementary in shape to the limb stump. 25

This invention relates to artificial limbs, and more particularly to a supporting stump socket for the artificial limb.

Heretofore, stump sockets for artificial limbs have been constructed of various materials. Canvas and stitched leather sockets were used for many years. However, such were not satisfactory since they often caused chafing and were not always comfortable due to the difficulty in properly fitting the socket for a particular patient’s use. Attempts have been made to produce limb sockets which were complementary in shape to the patient’s limb stump by first making a plaster of Paris stump which corresponded to the limb stump. A flexible socket was usually made using such a plaster mold in order to produce a closely fitting and comfortable socket. One such method similar to this is disclosed in the Ryan Pat. No. 2,578,019 granted on Dec. 11, 1951. One of the problems encountered in first making a plaster of Paris mold is that the limb stump normally changes shape when mounted in an artificial leg due to the pressure exerted thereon, thus resulting in a poorly fitting and uncomfortable artificial limb.

Limb stumps constructed in accordance with the present invention minimizes the above-mentioned problems, since in forming the stump socket an elastomeric member is placed on the limb stump in a stretched state so as to emphasize scar tissue and bony areas on the stump which are normally the most sensitive areas thereon.

Accordingly, it is an important object of this invention to provide an artificial leg having a stump socket which minimizes the above-mentioned problems.

Another important object of the present invention is to provide a stump socket for an artificial leg which is closely fitting and comfortable for the patient.

Still another important object of the present invention is to provide an artificial limb with a stump socket which is easy and quick to construct, while conforming to the exact shape of the limb stump.

Still another important object of the present invention is to provide a stump socket which distributes pressure on the stump of the patient in a manner which minimizes chafing and soreness.

The construction designed to carry out the invention will be hereinafter described, together with other features thereof.

The invention will be more readily understood from a reading of the following specification, and by reference to the accompanying drawing forming a part thereof, wherein an example of the invention is shown and wherein:

FIG. 1 is an elevational view, partially in section, of an artificial leg showing the stump socket.

FIG. 2 is an elevational view, partially in section, of an artificial leg constructed in accordance with the present invention having a modified base portion, and

FIG. 3 is an elevational view illustrating the manner in which the limb stump is prepared prior to making the socket for the artificial leg.

The drawing illustrates an artificial limb having a rigid outer shell A which defines a cavity for receiving a limb stump B. A stump socket is carried in the cavity A and includes flexible pads C positioned adjacent the inner wall of the outer shell of the artificial limb. An expansible polymer is inserted in the cavity in a liquid state, and is capable of expanding into a substantially rigid cellular supporting foam structure D. A form generally having an external shape corresponding to the shape of the limb stump B is positioned in the cavity prior to the polymer expanding. Thus, as the polymer expands a substantially rigid cellular supporting structure is produced having a cavity with an inner wall complementary in shape to the form for providing a closely fitting comfortable stump socket. The rigid cellular supporting structure is reinforced by the flexible pads C.

One of the most difficult problems associated with an artificial leg is acquiring a good comfortable fit between the limb stump and the socket which receives such. Heretofore, as previously mentioned, plaster of Paris casts were used in forming the stump socket and pads were used to make such fit properly. The disadvantage to this method is that it is impossible to judge exactly what size padding, and where such should be applied.

The outer shell A of the artificial leg may be constructed from any suitable material, such as metal, extruded plastic, etc., and has a foot portion 10 hinged to the bottom thereof in any suitable conventional manner. The outer shell A defines a cavity, the lower end of which is closed by any suitable means. In FIG. 1 the lower end of the cavity is shown as being closed with a wooden base 11, while in FIG. 2 the lower end of the cavity is filled with a hard solid material 12, such as polyester resin, or any suitable light plastic substance. Another layer of light hard plastic material 13 is positioned on top of the solid material 12 and extends upwardly in the cavity to a point approximately 2” to 3 below where the bottom portion of the limb stump would normally extend within the cavity. After the lower end of the cavity is closed the artifiical leg is ready to be equipped with the stump socket.

First, flexible pads C which may be constructed of any suitable material, such as flexible polyurethane, are positioned on the inner wall of the outer shell A. These pads may be of any suitable shape, however, they are shown in FIGS. 1 and 2 as being ring-shape pads adhered by any suitable means to the outer shell A. The patient for whom the artificial limb is being prepared then places a very light stump sock (½ ply) on his limb stump B. An elastomeric sleeve member 15 is pulled over the stump sock 14 in a stretched state so as to emphasize the contour of the limb stump. Such an elastomeric member may be a latex rubber sleeve with one end closed. By stretching the elastomeric member over the limb stump such causes the limb stump to assume a contour which corresponds to the contour of the limb stump when such is positioned under pressure in the artificial leg.

Thus, the rubber or elastomeric sleeve 15 must be quite tight so as to serve the purpose of forming the stump

3,520,002 ³ into the shape that it assumes in the prothesis under pressure.

The next step in the process of making the limb socket is the preparation and application of the rigid cellular foam structure D. One suitable cellular foam used is manufactured by Cooke Paint &amp; Varnish Company of Kansas City, Mo., and is referred to as “C” Foam System #460. This polyurethane foam can be mixed in small quantities in a fluid state. After the polyurethane foam has been mixed such is placed on top of the base enclosures 11 or 13. The patient then inserts the stump within the socket and remains erect for approximately fifteen to twenty minutes in order to get the proper angle between the stump and the casing A to assure proper positioning for walking. For the convenience of the patient not having experience with this process, it is sometimes necessary to form a jig which will allow the patient to remain seated and still give the proper angle. When a new limb is being made, the stump B can be positioned centrally within the cavity, and any variations needed can be achieved with alignment screws.

The stump is left in the artificial leg until the foam has risen to encompass the limb stump and set enough so that the elastomeric member 15 begins to free itself from the form, usually fifteen to twenty minutes. The stump is then removed from the elastomeric member 15 leaving such inside the stump socket temporarily. The prothesis is allowed to set overnight at a temperature of approximately 80° Fahrenheit. After the prothesis has set, the elastomeric member is then removed and the cavity formed in the stump stocket is the complement of the patient’s limb stump B and provides a closely fitting and comfortable stump socket. During forming of the cellular socket a polyethylene sheet is wrapped around the outer shell A for preventing the foam from overflowing onto the outer shell A.

The flexible foam pads C strengthens the rigid foam and provides a sturdy and durable stump socket. Sometimes, in order to protect the scar and bony areas it is necessary to hollow out the foam adjacent these areas a small amount during the fitting stage. One particular advantage of using the foam is that if the limb stump changes shape a new stump socket can be made without discarding the entire artificial limb. The stump socket constructed in accordance with the present invention requires no liners or inserts in order to properly fit the limb stump therein. It is noted that the rear portion 16 adjacent the top of the outer shell A is flared outwardly so as to permit the patient to bend his leg at the knee joint freely. After the artificial limb has been fitted to the patient and any modifications completed, a light coat or two of polyester resin or other suitable wearable plastic coating is placed over the upper three or four inches of the foam in order to give such a hard smooth surface for better wear. Some of the advantages of using polyurethane cellular foam is that it is non-toxic, odorless, has sufficient strength and hardness for support, can be easily removed and new foam put in the same place if necessary due to changes in the stump’s shape, allows passage of air, absorbs small amounts of moisture from perspiration, is resistant to normal acids, is selfextinguishing in regard to fire, and is lightweight.

In one particular artificial leg the flexible polyurethane foam pads are approximately Vs'' in thickness. During the foaming operation of the cellular structure D heat will be generated, however, if the polyurethane is prepared properly, such is not uncomfortable during the fitting operation.

The stump socket constructed in accordance with the present invention eliminates the time-consuming step of first producing a plaster of Paris mold which frequently is not the same shape of the limb stump when such is under pressure. The artificial limb may be attached to the patient’s thigh by any suitable attachment.