Socket liner for artificial limb

A hypobarically-controlled artificial limb for amputees includes a single socket with a volume and shape to receive a substantial portion of the residual limb. A sealed cavity is formed between the socket and the residual limb. The wearer may use a liner over the residual limb for comfort. A vacuum source is connected to a vacuum valve connected to the cavity to suspend the artificial limb from the residual limb and to control and minimize volumetric and fluid changes within the residual limb. A liner for a hypobarically-controlled socket for an artificial limb, with a liner interface bonding the liner to the socket and forming a seal between the liner and the socket. The liner may be permanently attached to the socket or the liner may be removed from the socket for replacement.

BACKGROUND OF THE INVENTION

The present invention relates to prosthetic devices and more particularly to a hypobarically-controlled artificial limb for amputees.

An amputee is a person who has lost part of an extremity or limb such as a leg or arm that commonly may be termed as a residual limb. Residual limbs come in various sizes and shapes with respect to the stump. That is, most new amputations are either slightly bulbous or cylindrical in shape while older amputations that may have had a lot of atrophy are generally more conical in shape. Residual limbs may further be characterized by their various individual problems or configurations including the volume and shape of a stump and possible scar, skin graft, bony prominence, uneven limb volume, neuroma, pain, edema or soft tissue configurations.

Referring toFIGS. 1 and 2, a below the knee residual limb10is shown and described as a leg12having been severed below the knee terminating in a stump14. In this case, the residual limb10includes soft tissue as well as the femur16, knee joint18, and severed tibia20and fibula22. Along these bone structures surrounded by soft tissue are nerve bundles and vascular routes that must be protected against external pressure to avoid neuromas, numbness and discomfort as well as other kinds of problems. A below the knee residual limb10has its stump14generally characterized as being a more bony structure while an above the knee residual limb may be characterized as including more soft tissue as well as the vascular routes and nerve bundles.

Referring toFIG. 2, amputees who have lost a part of their arm26, which terminates in a stump28also may be characterized as having vascular routes, nerve bundles as well as soft and bony tissues. The residual limb10includes the humerus bone30that extends from below the shoulder to the elbow from which the radius34and ulna36bones may pivotally extend to the point of severance. Along the humerus bone30are the biceps muscle38and the triceps muscle40which still yet may be connected to the radius34and the ulna,36, respectively.

In some respects, the residual limb amputee that has a severed arm26does not have the pressure bearing considerations for an artificial limb but rather is concerned with having an artificial limb that is articulable to offer functions typical of a full arm, such as bending at the elbow and grasping capabilities. An individual who has a paralyzed limb would also have similar considerations wherein he or she would desire the paralyzed limb to having some degree of mobility and thus functionality.

Historically, artificial limbs typically used by a leg amputee were for the most part all made out of wood such as an Upland Willow. The limbs were hand carved with sockets for receiving the stump14of the residual limb10. Below the socket would be the shin portion with the foot below the shin. These wooden artificial limbs were covered with rawhide, which often were painted. The sockets of most wood limbs were hollow as the limbs were typically supported in the artificial limb by the circumferential tissue adjacent the stump14rather than at the distal end of the stump14.

Some artificial limbs in Europe were also made from forged pieces of metal that were hollow. Fiber artificial limbs were also used which were stretched around a mold after which they were permitted to dry and cure. Again, these artificial limbs were hollow and pretty much supported the residual limb about the circumferential tissue adjacent the stump14.

All of these various artificial limbs have sockets to put the amputee's stump14thereinto. There are generally two categories of sockets. There are hard sockets wherein the stump goes right into the socket actually touching the socket wall without any type of liner or stump sock. Another category of sockets is a socket that utilizes a liner or insert. Both categories of sockets typically were opened ended sockets where they had a hollow chamber in the bottom and no portion of the socket touched the distal end of the stump14. So, the stump was supported about its circumferential sides as it fits against the inside wall of the sockets.

These types of sockets caused a lot of shear force on the stump14as well as had pressure or restriction problems on the nerve bundles and vascular flow of fluid by way of the circumferential pressure effect of the socket on the limb. This pressure effect could cause a swelling into the ends of the socket where an amputee may develop severe edema and draining nodules at the end of their stump14.

With time, prosthetists learned that by filling in the socket's hollow chamber and encouraging a more total contact with the stump and the socket, the swelling and edema problems could be eliminated. However, the problematic tissue configurations, such as bony prominences, required special consideration such as the addition of soft or pliable materials to be put into the socket.

Today, most artificial limbs are constructed from thermoset plastics such as polyester resins, acrylic resins, polypropylenes and polyethylenes, which are perhaps laminated over a nylon stockinette that also may be impregnated by the various resins.

In the past, most artificial limbs were suspended from the amputee's body by some form of pulley, belt or strap suspension often used with various harnesses and perhaps leather lacers or lacings. Another method of suspending artificial limbs is known as the wedge suspension wherein an actual wedge is built into the socket that is more closed at its top opening. The wedge in the socket cups the medial femoral condyle or knuckle at the abductor tubical. Yet another form of suspension is referred to as the shuttle system or a mechanical hookup or linkup wherein a thin suction liner is donned over the stump that has a docking device on the distal end which mechanically links up with its cooperative part in the bottom of the socket chamber. Sleeve suspensions were also used wherein the amputee may use a latex rubber tube which forms into a rubber-like sleeve which would be rolled on over both the top of the artificial limb and onto the amputee's thigh. The sleeve suspensions have been used in combination with other forms of suspensions techniques.

Both the use of a positive pressure system and the use of a negative pressure system (or hypobaric closed chamber) have been utilized in the field of prosthetics. At one time, for pressure systems “inflatable inner tubes” were used to fit into sockets. Presently, there are pneumatic “bags” which are strategically placed over what people consider to be good weight-bearing areas to increase pressure to help accommodate for volume changes within the socket.

The problem with this is that it is a very specific pressure and creates atrophy and loss of tissue dramatically over these high pressure areas. None of these systems employs positive pressure distributed over the total contact area between the residual limb and the artificial limb socket to accommodate volume changes within the socket.

The negative pressure aspects have been utilized for a closed chamber in that a socket is donned by pulling in with a sock, pulling the sock out of the socket and then closing the opening with a valve. This creates a seal at the bottom and the stump is held into the socket by the hypobaric seal. However, there are no systems that employ a negative pressure produced by a vacuum pump to lock the residual limb to the artificial limb.

The older systems were initially started in Germany. They were an open-ended socket, meaning there was an air chamber in the bottom of the socket. This did not work particularly well because it would cause swelling of the residual limb into the chamber created by the negative draw of suspending the weight of the leg and being under a confined area. This would lead to significance edema that would be severe enough to cause stump breakdown and drainage.

It was later discovered in America that total contact was essential between the residual limb and the socket and once you had total contact the weight was distributed evenly or the suspension was distributed over the whole surface of the limb rather than just over the open chamber portion of the socket.

The human body as a whole is under approximately one atmosphere of pressure at sea level. It keeps and maintains a normal fluid system throughout the body. When an amputee dons a prosthesis and begins taking the pressures of transmitting the weight of the body through the surface area of the residual limb to the bone, there is increased pressure on the residual limb equal to one atmosphere plus whatever additional pressures are created by weight bearing. This increased pressure causes the eventual loss of fluids within the residual limb to the larger portion of the body that is under less pressure. This loss of fluids causes the volume of the residual limb to decrease during the day. It varies from amputee to amputee, but it is a constant among all amputee and the more “fleshy” and the softer the residual limb, the more volume fluctuation there will be. The greater the weight and the smaller the surface area, the greater the pressures will be and the more “swings” there will be in fluids. In the past, the amputee had to compensate for this volume decrease by removing the artificial limb and donning additional stump socks to make up for the decreased residual limb volume.

While some of these devices addressed some of the problems associated with prosthetics, none of the artificial limbs, liners and socket, individually or in combination, offered a prosthesis that presented a total contact relationship with the residual limb; absorbed and dissipated shear, shock and mechanical forces transmitted to the limb tissues by the artificial limb; controlled residual limb volume; and used negative pressure as a locking device to hold the residual limb into the socket.

There is a need for an improved hypobarically-controlled artificial limb that will offer total contact relationship with the residual limb; absorb and dissipate shock, mechanical and shear forces typically associated with ambulation, twisting and turning and weight bearing with an artificial limb; control residual limb volume by way of even weight distribution; use negative pressure as a locking device to hold the residual limb into the socket; and to totally adjust and adapt the internal socket environment to changes in residual limb volume; and control stump volume changes by a negative pressure system which is also capable of providing positive pressure. Ideally, the vacuum system should be automatically regulated.

There is also a need for an improved hypobarically-controlled artificial limb with a positive mechanical interlock between an inner socket, which receives the residual limb, and an outer socket that attaches to the shin and foot of the artificial limb. Both the inner socket and the outer socket should have a rigid lower portion for weight-bearing and a substantially flexible upper portion to allow movement of the residual limb.

In the past, artificial limbs had to be custom-built for the amputee. The custom building process generally consisted of placing a singly ply thin cotton casting sock over the residual limb; making a first negative mold of the residual limb for forming an orthopedic plaster wrap about the residual limb and casting sock; making a first positive model of the residual limb by filling the negative mold with plaster; forming a thermoplastic foam about the positive model to create a space for a liner; adding additional thermoplastic foam to form a distal end cap as well as other areas which may require additional thicknesses due to tissue configurations; forming a second enlarged negative plaster mold about the foam; removing the foam; pouring a liquid and moldable liner into the space between the positive model and the second negative mold; allowing the liner to harden; removing the liner from the second negative mold; having the amputee don the liner over the residual limb; placing another single ply thin casting sock over the liner; making a third plaster wrap or negative mold of the artificial limb socket about the residual limb and the liner; removing the liner from the third plaster wrap; making a plaster cast or positive model of the socket from dental plaster; milling or shaving the positive model to create a reduced positive model to create weight bearing areas and compression of the liner against the residual limb and the socket; and making the socket from the reduced positive model.

This custom-building process is expensive, time-consuming, and requires the constant attention of a skilled prosthetist.

There is a need for a generic artificial limb socket that can be fitted to the contours of the residual limb without the need for a lengthy, expensive custom-molding process. The socket should contain a semi-compressible molding material which can be molded to the contours of the residual limb under vacuum and/or positive air pressure.

SUMMARY OF THE INVENTION

A liner for a socket of an artificial limb, the socket configured to receive a portion of an amputee's residual limb and the liner, the liner including a liner interface for bonding the liner and the socket. In one embodiment, the liner interface is configured to substantially seal the liner to the socket to minimize air leakage into space between the liner and the socket.

DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 3shows the hypobarically-controlled artificial limb50of the present invention. The hypobarically-controlled artificial limb50includes an outer socket52, shin54, and foot56. The outer socket52has a volume and shape to receive a substantial portion of the residual limb14with a space58therebetween.

A first embodiment of the hypobarically-controlled artificial limb50is shown inFIG. 4. The hypobarically-controlled artificial limb50further includes a flexible inner socket60with a cavity62with a volume and shape for receiving a substantial portion of the residual limb14and fitting in the space58between the outer socket52and the residual limb14. The inner socket60has an inner surface64opposing the residual limb14and an outer surface66opposing the outer socket52.

A vacuum source70may conveniently be attached to the shin or pylori54. The vacuum source70may preferably be a mechanical or motor-driven pump72. The vacuum source70is connected to a power source83, which may be a battery.

A vacuum valve74is suitably connected to the vacuum source70. The vacuum valve74may preferably be disposed on the outer socket52. A vacuum tube76connects the vacuum valve74to the cavity62. It will be seen that the vacuum source will cause the residual limb14to be drawn into firm contact with the inner surface64of the inner socket60.

The hypobarically-controlled artificial limb50also includes a regulator means80for controlling the vacuum source70. Preferably, the regulator means80may be a digital computer82. Alternately, the regulator means may be a vacuum regulator. The regulator means80is connected to a power source83, which may be a battery.

A seal means84makes an airtight seal between the residual limb14and the outer socket52. Preferably, the seal means84is a nonfoamed, nonporous polyurethane suspension sleeve86which rolls over and covers the outer socket52and a portion of the residual limb14. Alternatively, the seal means84may be any type of seal which is airtight.

The hypobarically-controlled artificial limb50may also include a thin sheath90between the residual limb14and the inner surface64of the inner socket60. As vacuum is applied to the cavity62, the sheath90will allow the vacuum to be evenly applied throughout the cavity62. Without the sheath90, the residual limb14might “tack up” against the inner surface64and form a seal which might prevent even application of the vacuum to the cavity62. The sheath90may also be used to assist the amputee into a smooth and easy fitting into the inner socket60. The sheath90is preferably made of thin knitted nylon.

The hypobarically-controlled artificial limb50may also include a nonfoamed, nonporous polyurethane liner92receiving the residual limb14and disposed between the sheath90and the residual limb14. The liner92provides a total-contact hypobaric suction, equal weight distribution socket liner. The liner92readily tacks up to the skin of the residual limb14and provides total contact with the limb14. The liner92absorbs and dissipates shock, mechanical and shear forces typically associated with ambulation.

The hypobarically-controlled artificial limb50may also include a stretchable nylon second sleeve94for rolling over and covering the suspension sleeve86to prevent clothing from sticking to and catching the suspension sleeve86.

Referring toFIG. 3, the polyurethane tubular sleeve86may be appreciated alone and in combination with the urethane liner92together with the optional nylon sheath90and second stretchable nylon sleeve94.

More specifically, the amputee takes the stretchable nylon second sleeve94, suitably made of a spandex-like material and rolls it up over the stump14to the upper portions of the residual limb suitably as the thigh of a leg12. Next, the polyurethane sleeve86is also rolled upwardly over the residual limb10. Thereafter, the liner92is optionally donned.

Next, the amputee may optionally utilize the nylon sheath90which is suitably of a non-stretching, thin, friction reducing nylon. As stated, this sheath90optionally may be used to assist the amputee into a smooth and easy fitting into the inner socket60. Alternatively, the sheath90may be avoided and the liner92simply inserted into the inner socket60of the artificial limb50.

Next, the amputee simply grasps the rolled over portion of the polyurethane sleeve86and rolls it over a substantial portion of the outer socket52. The sleeve86makes an airtight seal between the residual limb14and the outer socket52.

As can be appreciated, the polyurethane sleeve86is tacky. Consequently, the stretchable nylon second sleeve94may be utilized and rolled over the polyurethane sleeve86.

The amputee then sets the regulator means80to cause the vacuum source70to apply vacuum through the vacuum valve74and vacuum tube76to the cavity62. Enough vacuum is applied to cause the residual limb (with optional coverings) to be drawn firmly against the inner surface64of the inner socket60, which is flexible. The vacuum source70may preferably maintain a vacuum in the range of 0 to 25 inches of mercury (ideally fifteen to twenty inches).

It will be seen that the vacuum within the inner socket60will cause the hypobarically-controlled artificial limb50to be suspended from the residual limb14. The vacuum will lock the residual limb14into the inner socket60without causing swelling of the residual limb into the socket, because of the total contact of the residual limb14with the inner socket60. That is, there is no open chamber between the residual limb14and the inner socket60which would draw on the residual limb.

As the volume of the residual limb14decreases during the day due to weight-bearing pressures, the regulator means70may appropriately adjust the vacuum source70to draw the residual limb14more firmly against the inner socket60and thus compensate for the loss of residual limb volume. The vacuum may also partially oppose the loss of fluids from the residual limb caused by weight-bearing pressures.

A second embodiment of the hypobarically-controlled artificial limb50is shown inFIGS. 5 and 6. The second embodiment of the hypobarically-controlled artificial limb50is as described above, with the exception that the inner socket60A is compressible as well as being flexible. Instead of a vacuum source, the second embodiment has a positive air pressure source100, which may preferably be a motor-driven pump102. The regulator means80, which may be a digital computer82, controls the positive air pressure source100. The regulator means and positive air pressure source100are connected to a power source (not shown), which may be a battery. A positive pressure valve104connects the space58to the positive air pressure source100, for compressing the inner socket60A as the volume of the residual limb decreases.

It will be seen that as the volume of the residual limb14decreases during the day due to weight-bearing pressures, the regulator means80may control the positive air pressure source100to cause air pressure to compress the inner socket60A to compensate for the decreased volume of the residual limb, as shown inFIG. 6.

A third embodiment of the hypobarically-controlled artificial limb50is shown inFIG. 7. The third embodiment is a combination of the first and second embodiments described above.

The mechanical motor-driven pump72may act as both the vacuum source70and the positive air pressure source100. The regulator means80, vacuum source,70and positive air pressure source100are connected to a power source (not shown), which may be a battery.

The vacuum source70, under control of the regulator means80, will compensate for reduced residual limb volume up to a certain point. From that point on, the regulator means80will cause the positive air pressure source100to further compensate for reduced residual limb volume as described above. The third embodiment thus uses both vacuum and positive air pressure working together to lock the residual limb14into the inner socket60and reduce socket volume to compensate for fluid loss in the residual limb14. The exact point at which the changeover is made between vacuum compensation and positive air pressure compensation is controlled by the regulator means80, which as described may be a digital computer appropriately programmed for the socket environment.

A fourth embodiment of the hypobarically-controlled artificial limb50is shown inFIG. 8. The fourth embodiment is like the first embodiment, but includes two vacuum valves: a first vacuum valve106and a second vacuum valve110, both connected to the vacuum source70. The first vacuum valve106connects the vacuum source70to the space58. The space58contains a semi-compressible material108, such as polystyrene beads, as disclosed in U.S. Pat. No. 4,828,325, herein incorporated by reference.

To don the artificial limb50, the amputee proceeds as described above. After inserting the residual limb14(with optional coverings) into the inner socket60B, which is both compressible and expandable, and rolling the suspension sleeve86over the outer socket52, the amputee activates the regulator means80, causing the vacuum source70to apply a vacuum to the space58. This causes the material108to lock mechanically together into a rigid mass, conforming to the shape of the residual limb14. The inner socket60B may expand slightly under the weight of the residual limb14and under the influence of vacuum.

It will be seen that the semi-compressible molding material108can be molded to the contours of the residual limb14without using a custom-building process to produce a custom socket. The outer socket52may appropriately occur in standard sizes, such as small, medium, and large. The inner socket60B may also occur in standard sizes such as small, medium, and large. Adaptation of the inner socket60B to the contours of the residual limb14occurs through solidifying the material108under the influence of vacuum.

The second vacuum valve110connects the vacuum source70to the cavity62as previously described, for locking the residual limb14into the inner socket60B.

The fourth embodiment may also include a positive air pressure source100as previously described, to adjust the size of the inner socket60B to compensate for decreased residual limb volume.

The fourth embodiment may also include a thin sheath90, liner92, and second sleeve94, as previously described (seeFIG. 3).

The positive air pressure source100may also be used for shock absorption and a dynamic response in the ankle and foot sections of the artificial limb50, by means of a connection120.

A fifth embodiment of the hypobarically-controlled artificial limb50is shown inFIG. 10. This embodiment is the same as the first embodiment shown inFIG. 4, with some changes. First, vacuum source71may be a hand-operated vacuum pump71which may remove air from the cavity62down to approximately 15-25 inches of mercury. A suitable hand-operated vacuum pump is marketed under the trademark MITY VAC II® by Neward Enterprises, Inc. of Cucamonga, Calif.

The fifth embodiment also includes the seal means84which preferably consists of a nonfoamed, nonporous polyurethane suspension sleeve86for rolling over and covering a portion of the residual limb14. A portion of the seal means86is adapted to be disposed between the outer socket52and the inner socket60. The sleeve may be made of any of a variety of air-impervious elastomers.

The fifth embodiment, shown inFIG. 10also includes a mechanical interlock67,59for interlocking the inner socket62with the outer socket52. Preferably, the mechanical interlock consists of a first detent67in the inner socket62and a second detent59in the outer socket52. The first detent67engages the second detent59to lock the inner socket60into the outer socket52.

A sixth embodiment of the hypobarically-controlled artificial limb of the present invention is shown inFIGS. 11 and 12. The sixth embodiment is like the first embodiment shown inFIG. 4, with some changes.

First, the inner socket is specifically intended to be removably from the outer socket. To provide a positive mechanical connection between the inner socket and outer socket and yet allow the inner socket to be easily removed, the sixth embodiment includes a mechanical interlock103engaging the inner socket60and the outer socket52. Preferably, the mechanical interlock may be an extension104which is attached to the inner socket60and a docking device106attached to the outer socket52and receiving the extension104, and a locking mechanism105engaging the extension104and the docking device106.

The extension may be any sort of protrusion from the inner socket, such as a bulge or tab. Preferably, the extension104comprises a shuttle pin108.

The locking mechanism may be any sort of member which engages both the extension104and the docking device106, such as a screw, wire, or pin. Preferably, the locking mechanism105comprises a second pin110which extends outside the outer socket52as to be accessible.

Second, the sixth embodiment includes two thin sheaths, rather than one. A first inner sheath90may preferably be disposed between the residual limb14and the inner surface64of the inner socket60. As vacuum is applied to the cavity62, the inner sheath90will allow the vacuum to be evenly applied throughout the cavity62. Without the inner sheath90, the residual limb14might “tack up” against the inner surface64and form a seal which might prevent even application of the vacuum to the cavity62. The inner sheath90may also be used to assist the amputee into a smooth and easy fitting into the inner socket60.

An outer sheath93is preferably disposed between the suspension sleeve86and the inner socket60, thereby preventing the suspension sleeve from tacking to the inner socket60. Such tacking would cause friction between the inner socket60and the sleeve86which would cause the sleeve to wear out. Such tacking might also cause restrictions in the movement of the residual limb. The outer sheath93also protects the suspension sleeve86from being damaged by friction with the inner socket60.

The sixth embodiment also preferably includes an adhesive pressure tape95adapted to cover the outer sheath93, suspension sleeve86, and the second sleeve94and sealing the outer sheath93, suspension sleeve86, and the second sleeve94to the inner socket60. The tape95locks all of these layers to the inner socket so that they do not come loose during movement.

In the sixth embodiment, the suspension sleeve86goes between the inner socket60and the outer socket52, so that the sleeve86is protected from damage.

In the sixth embodiment, the inner socket60has a rigid lower portion98and a substantially flexible upper portion96. The rigid lower portion assists in weight-bearing while the substantially flexible upper portion allows for movement of the residual limb14. As the knee is bent from fully straight to fully flexed, the width of the knee changes rather significantly and in a hard, non-flexible socket brim, there can be excessive pressure on the residual limb14. The substantially flexible upper portion96makes the artificial limb50more comfortable and more adaptive to these changes. For the same reason, the outer socket52has a rigid lower portion102and a substantially flexible upper portion100.

Preferably, the top edge of the inner socket60is below the top edge of the outer socket52so that the sleeve86is protected from impact. Preferably, the top edge of the inner socket60may be 3/16 inch below the top edge of the outer socket52.

The sixth embodiment includes extensive modifications to the vacuum system.

First, a vacuum fitting78has been added to the inner socket60to attach the vacuum tube76. The vacuum fitting78allows the attachment of a vacuum sensor79adapted to sense the amount of vacuum in the cavity62and a sensor lead81is attached to the sensor79connecting the sensor79to the regulator means80, thus conveying the sensed vacuum to the regulator means80.

A vacuum valve74is placed between the cavity62and the vacuum source70to maintain vacuum in the cavity62. Typically, the vacuum valve74is a one-way valve or non-return valve.

In the sixth embodiment, the vacuum source70, vacuum tube76, vacuum valve74, regulator means80, and power source83are all attached to the outer socket52in the space58between the outer socket52and inner socket60. In this way, these delicate components are protected against being damaged by impact. Because of the placement of the regulator means80within the outer socket52, a vacuum control77is provided extending outside the outer socket52to allow manual control of the regulator means80.

The amputee dons the sixth embodiment in a manner similar to that earlier described, with some modifications. First, the outer sheath93is put on the residual limb14after rolling the suspension sleeve86upward over the residual limb and before donning the liner92. After donning the inner sheath90over the liner92, the amputee inserts the residual limb14into the inner socket60. Next, the outer sheath93, suspension sleeve86, and second sleeve94are rolled down over the inner socket60, and the adhesive pressure tape95is applied. Next, the wearer sets the regulator means80to an appropriate vacuum level by means of the vacuum control77, and connects the vacuum tube76to the vacuum fitting78. The inner socket60is then placed within the outer socket52so that the shuttle pin108engages the docking device106and the locking pin110is set to engage the shuttle pin108and the docking device106, providing a positive mechanical interlock.

A seventh embodiment of the hypobarically-controlled artificial limb of the present invention is shown inFIG. 13. The seventh embodiment is similar to the sixth embodiment, with some changes.

First, the mechanical interlock103does not engage the inner socket60. Instead, the mechanical interlock engages the outer socket52and the suspension sleeve86. To accomplish this, the suspension sleeve86covers the entire inner socket60, and the suspension sleeve86has the extension104or shuttle pin108embedded in the suspension sleeve at the distal end of the suspension sleeve, as shown inFIG. 14. Preferably, the extension104has a portion104A embedded in the suspension sleeve. This portion104A may be a disk or umbrella104A. The extension104then engages the docking device106as previously described.

Second, the suspension sleeve86is modified to support the additional weight imposed on the suspension sleeve86due to the outer socket52and artificial limb. In particular, the suspension sleeve86is fabricated from a material which allows circumferential expansion but resists longitudinal stretching under the weight of the artificial limb. Such a material is described in U.S. Pat. No. 5,571,208, herein incorporated by reference.

The sleeve86preferably contains fabric threads which may be oriented circumferentially around the sleeve. The threads preferably are comprised of double-knit polyurethane. The threads may also include nylon. The threads permit the sleeve86to expand circumferentially so that the sleeve may be slipped onto the residual limb14and so that the lower portion may be slipped over the inner socket52. The threads are preferably connected together with cross-links, which also may be preferably comprised of polyurethane. The cross-links and threads form a matrix which allows circumferential expansion but resists longitudinal stretching under the weight of the artificial limb. By example, the sleeve86may have a 4-to-1 ratio of circumferential stretch relative to longitudinal stretch.

The sleeve86may have a portion above the inner socket52which is manufactured of material which allows both vertical and horizontal stretching, to increase flexibility.

An eighth embodiment of the hypobarically-controlled artificial limb of the present invention is shown inFIG. 15.

Unlike earlier embodiments, the artificial limb50of the eighth embodiment has only a single socket60rather than inner and outer sockets and is thus considerably simpler.

The socket60has a volume and shape to receive a substantial portion of the residual limb14with a cavity62therebetween.

A nonfoamed, nonporous polyurethane liner92is preferably adapted to receive the residual limb14and to be disposed between the residual limb14and the socket60.

A vacuum source70is connected to the cavity62by a vacuum valve78, thereby drawing the residual limb14into firm contact with the socket60.

A seal means84makes a seal between the residual limb14and the socket60to minimize air leakage into the cavity62. It has been found that it is impossible to make a perfect seal, with the result that air leakage can occur at rates up to 30 cc per minute. As air leaks into the cavity62, it is necessary to activate the vacuum source70to restore vacuum in the cavity. Furthermore, it has been found that when the vacuum in the cavity is about 5 inches of mercury, the residual limb may lose up to 6 to 15% of its volume during the day, whereas if the vacuum in the cavity is 15-25 inches of mercury, the residual limb loses only about 1% of its volume during the day.

To minimize the time that the vacuum source, such as a vacuum pump72, needs to run to maintain vacuum in the cavity, a ninth embodiment of the artificial limb50is shown inFIG. 16. The ninth embodiment is the same as the eighth embodiment, but a vacuum reservoir110is added between the vacuum source70and the vacuum valve78. The vacuum reservoir110has a volume substantially larger than the cavity62. Suitably, the vacuum reservoir may have a volume of 2 gallons or 9000 cc while the volume of the cavity62may be only about 100 cc or even less.

It will be seen that as air leaks into the cavity62, the air will be pulled into the vacuum reservoir110, thereby maintaining the vacuum in the cavity62.

When the vacuum in the reservoir110reaches a certain minimum threshold, the vacuum source70may be activated to restore vacuum to the vacuum reservoir110. The vacuum source70may be activated either manually or by a regulator means (not shown).

The artificial limb50typically includes a shin or pylori54and a foot56, as shown inFIG. 3. Preferably, the vacuum reservoir110is attached to the shin54between the socket60and the foot56. However, the vacuum reservoir may also be carried separately, as for example in a backpack. Depending on the placement of the vacuum reservoir110, a vacuum tube76maybe necessary to connect the vacuum reservoir110to the vacuum valve78.

If the volume of the vacuum reservoir110is about 9000 cc and air leaks into the cavity62at about 75 cc per minute, it will be seen that the intervals between activation of the vacuum source70can be up to about 120 minutes.

The artificial limb50of the eighth and ninth embodiments may preferably further comprise the following.

An inner sheath90may be adapted to be disposed between the liner92and the socket, to ensure even distribution of vacuum in the cavity62, as earlier described. Preferably, the inner sheath90may be thin knitted nylon. The sheath90may also be affixed to the outside of the liner92.

The seal means84is preferably a nonfoamed, nonporous polyurethane suspension sleeve86for rolling over and covering the socket60and a portion of the artificial limb14, as earlier described. Seal means may also be an external annular abutting flange or ring140shown inFIG. 17. Again, seal means may also be an internal annular abutting flange or ring140shown inFIG. 18.

A stretchable nylon second sleeve94(seeFIG. 3) for rolling over and covering the suspension sleeve86may be added to prevent clothing from sticking to and catching on the suspension sleeve86, as earlier described.

The vacuum source70is preferably a motor or mechanical driven vacuum pump72, as earlier described. A vacuum tube76may be necessary to connect the vacuum pump72to the vacuum valve78, depending on the placement of the vacuum pump72.

Applicant has found that many of the embodiments discussed earlier share a common problem. The vacuum which holds the residual limb (and liner) in firm contact with the socket tends to cause edema and blistering at the point on the residual limb where the suspension sleeve contacts the residual limb. This problem occurs because the vacuum (perhaps 7½ pounds of negative pressure) in cavity62draws against the suspension sleeve86at the point where the suspension sleeve86contacts the skin of the residual limb. However, because the liner92often has an outer fabric cover130to prevent the liner from adhering to the socket60or clothing, the suspension sleeve cannot make a good seal at the point where it contacts the outer fabric cover120. This has left the residual limb as the only point at which to make the seal.

FIG. 17shows one solution to this problem. The liner92is improved by adding an annular seal140extending outwardly from the fabric cover130. The annular seal, which may be made from the same material as the inner layer92of the liner, is adapted to sealingly engage the suspension sleeve86, producing a seal against the vacuum in cavity62at the point of contact with the suspension sleeve86. Therefore, the vacuum in cavity62now draws against the annular seal130rather than against the skin of the residual limb14.

An alternative solution to the above problem is shown inFIG. 18. Here, the annular seal140does not make contact with the suspension sleeve86, but rather makes contact with the inner wall63of the socket60, and makes a seal at that point. No suspension sleeve is used in this variation, it being found that sufficient holding force is provided by the vacuum in cavity62.FIG. 18also shows that the annular seal140may simply be an extension of the liner92, passing through the fabric cover130.

A second alternative is shown inFIG. 19. This alternative is like that ofFIG. 18, with the exception that a mechanical interlock103is provided which is adapted to interlock with the socket60. Preferably, as shown, the mechanical interlock103comprises a shuttle pin108adapted to connect the liner92with the socket60, and a locking mechanism105such as a second pin110extending through the socket60to the exterior of the socket60for access by the amputee as earlier described. More particularly, the liner92may have an extension104or shuttle pin108embedded in the liner at the distal end of the liner. Preferably, the extension104has a portion104A which may be a disk or umbrella which engages a docking device106as earlier described.

To keep air from entering the cavity62, the invention ofFIG. 19also preferably includes a locking mechanism seal150adapted to engage the inner wall63of the socket60about the locking mechanism105. The seal150could alternatively be on the outer surface of the socket60.

Another alternative is shown inFIG. 20. Here, the fabric cover130stops below the annular seal140. The annular seal140may also be made of the same material as the liner92.

Applicant has found that, by bonding the liner92directly to the inside surface63of the socket60, a seal may be produced that maintains the vacuum in the cavity62without the need for a separate annular seal or vacuum seal.FIG. 21shows this embodiment.

InFIG. 21, the liner92is bonded directly to the inside surface63of the socket60by an adhering interface64.

The adhering interface64may be such as to provide a permanent attachment of the liner92to the socket60, or a semi-permanent attachment that allows the liner92to be removed and replaced.

The adhering interface64may be any interface that has two adhering surfaces. One adhering surface64apreferably adheres to the liner92while the other adhering surface64bpreferably adheres to the inside surface63of the socket60.

Possible embodiments of a permanent attachment for the adhering interface64are: a laminating adhesive, i.e., a thin film placed on the surface of the liner and the liner92then being inserted into the socket60; contact cement; or any type of paint-on glue.

Possible embodiments of a semi-permanent attachment for the adhering interface64are: a hook and loop fastener fabric such as Velcro®; or cooperating magnets in both the liner92and the socket60.

To don the artificial limb, the wearer inserts the residual limb into the liner, which is already attached to the socket by the adhering interface.

Additional connections may be employed between the residual limb and the socket, such as the nonfoamed, nonporous polyurethane suspension sleeve earlier described and the mechanical interlock also previously described.

The present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof, and it is therefore desired that the present embodiment be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.