Abstract:
A system for removing perspiration from a residual limb inserted in a prosthesis comprising an nonporous prosthesis socket, a porous thin sheath adjacent the socket, a nonporous liner adjacent the sheath, an osmotic membrane adjacent the liner allowing water vapor to pass from the limb but preventing liquid from passing to the limb, a nonporous seal that prevents air leakage between the residual limb and the socket; and, a vacuum source to reduce the pressure in a space between the limb and socket. A method of removing perspiration from a residual limb in a prosthesis.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This is a continuation of U.S. patent application Ser. No. 09/829,306, filed on Apr. 9, 2001, now abandoned which is a continuation-in-part of U.S. patent application Ser. No. 09/325,297, filed Jun. 3, 1999, now abandoned, and U.S. patent application Ser. No. 09/534,274, filed Mar. 23, 2000, issued as U.S. Pat. No. 6,554,868. 

   BACKGROUND OF THE INVENTION 
   The present invention relates to prosthetic devices and more particularly to a hypobarically-controlled artificial limb for amputees and to a method for removing perspiration from the space between the residual limb and the liner by means of an osmotic membrane and an applied vacuum. 
   An amputee is a person who has lost part of an extremity or limb such as a leg or arm which 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 to  FIGS. 1 and 2 , a below the knee residual limb  10  is shown and described as a leg  12  having been severed below the knee terminating in a stump  14 . In this case, the residual limb  10  includes soft tissue as well as the femur  16 , knee joint  18 , and severed tibia  20  and fibula  22 . Along these bone structures surrounded by soft tissue are nerve bundles and vascular routes which must be protected against external pressure to avoid neuromas, numbness and discomfort as well as other kinds of problems. A below the knee residual limb  10  has its stump  14  generally 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 to  FIG. 2 , amputees who have lost a part of their arm  26 , which terminates in a stump  28  also may be characterized as having vascular routes, nerve bundles as well as soft and bony tissues. The residual limb  10  includes the humerus bone  30  which extends from below the shoulder to the elbow from which the radius  34  and ulna  36  bones may pivotally extend to the point of severance. Along the humerus bone  30  are the biceps muscle  38  and the triceps muscle  40  which still yet may be connected to the radius  34  and the ulna,  36 , respectively. 
   In some respects, the residual limb amputee that has a severed arm  26  does 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. 
   During the day, as the residual limb amputee walks on an artificial limb, perspiration builds up between the residual limb and the liner which cushions the residual limb in the artificial limb socket. As this perspiration buildup continues, the residual limb begins to slip around within the liner, causing a feeling to the wearer of losing contact with the artificial limb. This slippage often also causes irritation to the residual limb, which may be worsened by a growth of bacteria in the warm, moist environment between the residual limb and the liner. 
   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 without causing swelling of the residual limb into the socket; and control the buildup of perspiration on the residual limb. One of the ways of controlling the buildup of perspiration is to use a vacuum system to wick away this perspiration from the residual limb. 
   U.S. Pat. No. 5,888,230 discloses the use of a vacuum pump connected between the limb and a liner. However, this invention is essentially inoperable because the liner will conform to the stump at all times, by an interference fit, so that there is no space between the residual limb and the liner against which to draw a vacuum. In any case, the patent does not disclose application of vacuum to the socket cavity in such a manner as to draw the residual limb firmly and totally against the interior of the socket. Instead, the patent discloses the use of shims between the liner and the socket. Without total contact between the residual limb and the socket, the limb may swell into the space between the limb and the socket. Also, the patent does not disclose the use of vacuum to remove perspiration. 
   U.S. Pat. No. 5,549,709 discloses several embodiments of a hypobarically-controlled artificial limb. However, all of these embodiments required two sockets: an outer socket and an inner socket. Applicant has found that the present invention offers improved performance without the requirement for two sockets. A single socket works equally well or better than two sockets. Also, this patent does not disclose a mechanism for maintaining vacuum in the presence of air leakage into the socket. 
   It has been found that it is essentially impossible to maintain a perfect, airtight seal between the residual limb and the sockets disclosed in U.S. Pat. No. 5,549,709, with the result that slow air leakage into the sockets diminishes the vacuum in the sockets. With the reduction in vacuum, the beneficial effects of the vacuum also slowly diminish. Consequently, there is a need for a means for maintaining the vacuum in the socket cavity in the presence of some air leakage past the seal. 
   SUMMARY OF THE INVENTION 
   A system for removing perspiration from a residual limb inserted in a prosthesis comprising an nonporous prosthesis socket, a porous thin sheath adjacent the socket, a nonporous liner adjacent the sheath, an osmotic membrane adjacent the liner allowing water vapor to pass from the limb but preventing liquid from passing to the limb, a nonporous seal that prevents air leakage between the residual limb and the socket; and a vacuum source to reduce the pressure in a space between the limb and socket. 
   A method of removing perspiration from a residual limb in a prosthesis comprising the steps of inserting the residual limb into a sleeve comprising an osmotic membrane that allows water vapor to pass from the limb but prevents liquid from passing to the limb. The residual limb and osmotic membrane sleeve are inserted into a flexible, nonporous liner. The residual limb, osmotic membrane sleeve, and liner are inserted into a porous sheath. The residual limb, osmotic membrane sleeve, liner, and sheath are inserted into a prosthetic socket cavity having a volume and shape to receive the residual limb. The socket cavity is sealed with a nonporous seal, and vacuum applied to the socket cavity in the space between the membrane and the socket to draw the residual limb and liner into firm contact with the socket and provide a reduced pressure in the socket cavity. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side elevational view of the tissue and skeletal structure of an amputee&#39;s residual limb; 
       FIG. 2  is a side elevational view of a residual limb in the form of an amputated arm showing the skeletal and muscular structure of the residual limb; 
       FIG. 3  is an exploded elevational view of the residual limb donning the polyurethane sleeve, stretchable nylon sleeve, liner, osmotic membrane, nylon sheath and socket of an artificial limb; 
       FIG. 4  is a cross-section along the lines  4  of  FIG. 3 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIGS. 3 and 4  show one embodiment of the apparatus  50  of the present invention. The hypobarically-controlled artificial limb  50  includes a single socket  60 , shin  54 , and foot  56 . The socket  60  has a volume and shape to receive a substantial portion of the residual limb  14  with a space  58  therebetween. 
   The apparatus  50  further includes a cavity  62  in the socket  60  with a volume and shape for receiving a substantial portion of the residual limb  14 . 
   A vacuum source  70  may conveniently be attached to the shin or pylon  54 . The vacuum source  70  may preferably be a mechanical or motor-driven pump  72 . The vacuum source  70  may be connected to a power source  83 , which may be a battery. 
   A vacuum valve  74  is suitably connected to the vacuum source  70 . The vacuum valve  74  may preferably be disposed on the socket  60 . A vacuum tube  76  connects the vacuum valve  74  to the cavity  62 . It will be seen that the vacuum source will cause the residual limb  14  to be drawn into firm contact with the inner surface  64  of the socket  60 . 
   The hypobarically-controlled artificial limb  50  also includes a regulator means  80  for controlling the vacuum source  70 . Preferably, the regulator means  80  may be a digital computer  82 . Alternately, the regulator means may be a vacuum regulator. The regulator means  80  is connected to a power source  83 , which may be a battery. 
   A seal means  84  makes an airtight seal between the residual limb  14  and the socket  60 . Preferably, the seal means  84  is a nonfoamed, nonporous polyurethane suspension sleeve  86  which rolls over and covers the socket  60  and a portion of the residual limb  14 . Alternatively, the seal means  84  may be any type of seal which is airtight. 
   The apparatus  50  may also include a nonfoamed, nonporous polyurethane liner  92  receiving the residual limb  14  and disposed between the socket  60  and the residual limb  14 . The liner  92  provides a total-contact hypobaric suction, equal weight distribution socket liner. The liner  92  readily tacks up to the skin of the residual limb  14  and provides total contact with the limb  14 . The liner  92  absorbs and dissipates shock, mechanical and shear forces typically associated with ambulation. 
   The hypobarically-controlled artificial limb  50  may also include a thin sheath  90  between the liner  92  and the inner surface  64  of the socket  60 . As vacuum is applied to the cavity  62 , the sheath  90  will allow the vacuum to be evenly applied throughout the cavity  62 . Without the sheath  90 , the liner  92  might “tack up” against the inner surface  64  and form a seal which might prevent even application of the vacuum to the cavity  62 . The sheath  90  may also be used to assist the amputee into a smooth and easy fitting into the inner socket  60 . The sheath  90  is preferably made of thin knitted nylon. 
   The hypobarically-controlled artificial limb  50  may also include a stretchable nylon second sleeve  94  for rolling over and covering the suspension sleeve  86  to prevent clothing from sticking to and catching the suspension sleeve  86 . 
   The hypobarically-controlled artificial limb  50  may also include an osmotic membrane  100  encompassing the residual limb  14  and creating a space  102  between the residual limb  14  and the liner  92 . The osmotic membrane  100  allows perspiration to pass in one direction only from the residual limb outward toward the liner  92 . 
   This beneficial effect of the osmotic membrane is achieved as follows. The osmotic membrane allows water vapor to pass through the membrane from the side of the membrane with a higher partial water vapor pressure (the residual limb side) to the side of the membrane with a lower partial water vapor pressure (the liner side), but not in the opposite direction. Eventually, the partial water vapor pressure on the two sides of the osmotic membrane would become equal, and transmission of vapor through the membrane would cease. However, application of vacuum to the space  102  will continually lower the partial water vapor pressure on the liner side of the membrane  100 , so that water vapor will continue to pass through the membrane. In turn, this lowers the partial water vapor pressure on the residual limb side of the membrane  100 , allowing perspiration on the residual limb to change from the liquid state to the vapor state. 
   Appropriate materials for the osmotic membrane  100  are the Sympatex hydrophylic polyester block copolymer from Sympatex Technologies, One Merrill Industrial Drive, Suite 201, Hampton, N.H. 03842; the Goretex® material from A.W. Gore &amp; Associates, www.gore.com; the Gill 02 Fabric from Gill North America, 1025 Parkway Industrial Park, Buford, Ga. 30581; and the SealSkinz product from Porvair, Estuary Road, King&#39;s Lynn, Norfolk, PE30 2HS, United Kingdom. 
   The osmotic membrane may be laminated onto a supporting fabric, such as a cloth stump sock. 
   An important aspect of the osmotic membrane  100  is that it should have no pores into which the skin of the residual limb  14  may be drawn under the influence of vacuum. 
   Optionally, vacuum from the vacuum source may be applied to the space  102  between the osmotic membrane  100  and the liner  92 . Application of vacuum lowers the boiling point of water, allowing perspiration passing through the osmotic membrane  100  to evaporate and be removed from the space  102 . 
   Referring to  FIG. 3 , the polyurethane tubular sleeve  86  may be appreciated alone and in combination with the urethane liner  92  together with the optional nylon sheath  90  and second stretchable nylon sleeve  94 . 
   More specifically, the amputee takes the stretchable nylon second sleeve  94 , suitably made of a spandex-like material and rolls it up over the stump  14  to the upper portions of the residual limb suitably as the thigh of a leg  12 . Next, the polyurethane sleeve  86  is also rolled upwardly over the residual limb  10 . The amputee than places the osmotic membrane  100  over the residual limb  14 . Thereafter, the liner  92  is donned. 
   Next, the amputee may optionally utilize the nylon sheath  90  which is suitably of a non-stretching, thin, friction reducing nylon. As stated, this sheath  90  optionally may be used to assist the amputee into a smooth and easy fitting into the socket  60 . Alternatively, the sheath  90  may be avoided and the liner  92  simply inserted into the socket  60  of the artificial limb  50 . 
   Next, the amputee simply grasps the rolled over portion of the polyurethane sleeve  86  and rolls it over a substantial portion of the socket  60 . The sleeve  86  makes an airtight seal between the residual limb  14  and the socket  60 . 
   As can be appreciated, the polyurethane sleeve  86  is tacky. Consequently, the stretchable nylon second sleeve  94  may be utilized and rolled over the polyurethane sleeve  86 . 
   The amputee then sets the regulator means  80  to cause the vacuum source  70  to apply vacuum through the vacuum valve  74  and vacuum tube  76  to the cavity  62 . Enough vacuum is applied to cause the residual limb (with optional coverings) to be drawn firmly against the inner surface  64  of the socket  60 , which is flexible. The vacuum source  70  may preferably maintain a vacuum in the range of 0 to 25 inches of mercury (ideally ten to twenty five inches). 
   It will be seen that the vacuum within the socket  60  will cause the hypobarically-controlled artificial limb  50  to be suspended from the residual limb  14 . The vacuum will lock the residual limb  14  into the socket  60  without causing swelling of the residual limb into the socket, because of the total contact of the residual limb  14  with the socket  60 . That is, there is no open chamber between the residual limb  14  and the socket  60  which would draw on the residual limb. 
   As the volume of the residual limb  14  decreases during the day due to weight-bearing pressures, the regulator means  80  may appropriately adjust the vacuum source  70  to draw the residual limb  14  more firmly against the socket  60  and thus compensate for the loss of residual limb volume. The vacuum may also partially or completely oppose the loss of fluids from the residual limb caused by weight-bearing pressures. 
   The vacuum within the socket  60  is also applied to the space  102  between the osmotic membrane  100  and the liner  92 . Application of vacuum to the space  102  lowers the boiling point of water, causing perspiration wicking through the osmotic membrane to evaporate and be drawn out of the space  102 . 
   The vacuum source  70  may be a weight-actuated vacuum pump and shock absorber as disclosed in U.S. patent application Ser. No. 09/534,274, filed Mar. 23, 2000 and herein incorporated by reference. 
   To maintain the vacuum in the cavity, either a regulator means  80 , or a weight-actuated vacuum pump and shock absorber as disclosed in U.S. patent application Ser. No. 09/534,274, may be employed. 
   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.