Patent Publication Number: US-2007112439-A1

Title: Power evacuation valve for prosthetic limb socket

Description:
BACKGROUND OF THE INVENTION  
      1. Field Of The Invention  
      The present invention generally relates to artificial or prosthetic limbs for amputees, and more particularly to a power evacuation valve to assist in removing air from the socket of a prosthetic limb to improve suspension.  
      2. Discussion of the Prior Art  
      In the field of fitting amputees with artificial limbs, there are a variety of systems that have evolved over time to enhance retention or suspension of an artificial limb from a residual limb. However, currently there are two types of systems that are most often used. The first, and most widely used, is an artificial limb that has a relatively rigid molded socket that is fitted so as to receive the patient&#39;s stump of the residual limb, with direct contact between the socket and the skin of the residual limb. The second, is a more expensive and sophisticated system that requires the patient to use a liner or other insert to cover the stump of the residual limb and incorporates an interface with a relatively rigid molded socket that is configured to develop sub-atmospheric pressures to enhance the integrity of the fit of the artificial limb to the patient&#39;s covered stump or specialized insert.  
      The first type of system is fairly simplistic and cost effective. It does not include a liner or insert, or any other supplemental means of developing sub-atmospheric pressures between the stump and the socket. However, it does have drawbacks. With the first type of prosthetic system, for instance with a lower leg prosthesis, there are several steps required for the patient to achieve insertion into the socket and then attempt to maintain an absence of air between the limb and socket during use.  
      With the first type of system, the socket typically will have an aperture near the bottom which is configured to receive a plug such as by threaded engagement. To prevent the friction that would otherwise occur when attempting to place the patient&#39;s stump into the socket, the patient may use a donning sock. Thus, when using a donning sock to install the artificial limb for use, the patient will start by pulling the donning sock over the stump. Before or after pulling the donning sock over the stump, the patient also will remove the plug from the aperture in the lower portion of the socket. The patient will thread the end of the donning sock through the aperture. Then, the sock covered stump will be inserted into the socket. Next, the patient will grab hold of the donning sock, and pull the donning sock through the aperture while advancing the stump into the socket, thereby leaving the skin of the stump in direct contact with the inner surface of the socket. Finally, the patient will reattach the plug in sealing engagement with the socket. With the stump in the socket and the plug reinstalled, this will cause any attempted removal of the stump from the socket to naturally draw a vacuum within the socket, thereby resisting withdrawal of the stump from the socket.  
      Unfortunately, without a source of vacuum and without a liner over the stump, it heretofore has not been possible to ensure removal of all of the air between the stump and the socket. Also, it is common for the interface between the skin on the stump and the relatively rigid socket to periodically permit some air to pass by and to enter the socket. When this occurs, the integrity of the fit of the limb and thereby its performance is breached. Indeed, at some point, the suspension will be so inadequate that the patient risks complete detachment from the artificial limb. To reestablish a more secure fit and better suspension, the patient occasionally must force the artificial limb deeper into the socket to reestablish a better fit. This obviously is far from satisfactory performance, may cause some discomfort, and can be very awkward for the patient. To allow the trapped air to escape, the patient must either partially or fully unscrew the threaded plug. Alternatively, the patient may use a plug having a one-way valve. This type of valve typically would be actuated by pressing on a central portion that would allow the trapped air to escape, but would not allow any air to reenter the socket via the valve.  
      There has been a suggestion that the ease of donning and doffing (or removing a prosthetic limb) may be enhanced by not using a donning sock, but rather by lubricating the skin of the stump or the interior surface of the socket and then using sub-atmosphere pressure to draw the stump into the socket and using positive air pressure to push the stump from the socket for removal. Such a system is disclosed for use in donning and doffing in U.S. Pat. No. 5,658,353. However, the system has drawbacks in that a lubricant must be used which is not only messy and inconvenient, but impractical in that it can be ingested into the pump and cause premature pump failure. Moreover, the modified system also contemplates removal of the suction device, and use of a conventional plug or one-way valve once the prosthetic limb is donned, leading to the same potential problems of compromised engagement and suspension during normal use of the artificial limb. Also, such a system is disclosed as being for use with a standard ac power source, limiting when and where it can be used.  
      As noted above, the second type of system is more complicated than the first. It is based on achieving and maintaining fairly substantial sub-atmospheric pressures in the socket for an improved fit and suspension. However, such higher sub-atmospheric pressures commonly would be injurious if applied directly to the naked stump. Therefore, the second system employs a liner to cover the stump or an insert device that is used between the stump and the socket, as is disclosed in U.S. Pat. No. 6,726,726 Thus, a liner covered stump or alternative insert device attached to the stump is inserted into a socket, without permitting the skin of the residual limb to be directly exposed to the relatively high sub-atmospheric pressures.  
      To date, all of the sub-atmospheric systems for improving suspension known to the inventor have been essentially of one of two configurations. The first common form is in a weight activated pump to remove air upon impact, such as when the patient walks or stomps on the ground. These pumps may be referred to as gait-driven pumps, and they can be built into the prosthetic limb, but tend to be heavy and awkward in their manner of use. The second form tends to include an electrically activated pump capable of achieving or, with use of a regulator, maintaining vacuum levels sufficient to ensure a sound fit of a covered stump or insert to the socket. While there are claims that such sub-atmospheric pressures, when used with a stump liner, may serve to enhance circulation and wound healing, the prior art systems capable of sustained sub-atmospheric pressures have required some form of a roll-on urethane or thermoplastic liner or insert to be worn on the stump, to prevent injury to the patient which would occur if the patient&#39;s skin is directly subjected to such high levels of vacuum.  
      These sub-atmospheric type systems have had drawbacks. The need for the liner or insert, and for a power source and pump sufficient to maintain vacuum levels in the range of 10-30 inches of mercury add significantly to the cost of the prosthetic device, and contribute to the weight of the system. Also, these systems are highly customized and generally the entire system must be fabricated and employed together as new equipment. Therefore, these systems do not tend to lend themselves to be adapted or retrofit to the existing artificial limbs used by patients having the above-mentioned first type of system with the relatively rigid molded socket that directly engages the patient&#39;s skin.  
      Accordingly, it is desirable to provide a device that will enhance the fit and performance of prosthetic limb systems, without the additional cost of the stump liner or insert interface, or the weight and size associated with pumps more suited for use in the second type of system. It also is desirable to be able to employ such a device as a retrofit to existing systems of the first type, with portability and attachment to the prosthetic limb to travel with the patient so as to assist in maintaining sound suspension, and without need for messy lubricants, frequent substitution of valves or alternatively the risk of injury to the patient&#39;s residual limb due to a more significant sustained use of vacuum. Further, it is desirable to be able to custom design a device into original equipment systems for use by patients that will have skin to socket contact, without significantly complicating the structures involved.  
      The present invention addresses shortcomings in prior art prosthetic devices, while providing the above mentioned desirable features.  
     SUMMARY OF THE INVENTION  
      The purpose and advantages of the invention will be set forth in and apparent from the description and drawings that follow, as well as will be learned by practice of the invention.  
      The present invention is generally embodied in a power evacuation valve for a prosthetic limb socket. The power evacuation valve may be embodied in various configurations, with each configuration including a housing having at least two portions. The configurations may include a housing having a valve body connected directly to a first housing portion, so as to locate the entire power evacuation valve assembly adjacent a valve body aperture placed in the socket. Alternatively, the valve body may be remote from the housing, so as to permit the larger housing to be connected to the prosthetic limb at a location spaced from the socket valve body aperture.  
      In a first aspect of the invention, a power evacuation valve for a prosthetic limb socket is provided for a socket that is adapted for direct contact with the skin of a stump of a residual limb of a patient and that has an aperture in the socket. The power evacuation valve has a housing, a valve body connected to the housing and being adapted to be removably connected to the socket aperture. The power evacuation valve further has an electrical switch connected to the housing, an electrically activated pump, a one-way valve connected in fluid communication with the pump, the valve body being connected in fluid communication with the pump, and at least one battery connected to the electrically activated pump and to the electrical switch.  
      In another aspect of the invention, the valve body is integrally formed with the housing. In a further aspect of the invention, the valve body is mounted to the housing. In an alternative aspect of the invention, the valve body is spaced from the housing and connected to the housing via a conduit. In a further aspect of the invention, the power evacuation valve includes a regulator to avoid vacuum levels that potentially would injure a patient by automatically preventing the vacuum level from exceeding a preselected sub-atmospheric pressure.  
      Thus, the present invention presents an alternative to the above-mentioned prior art prosthetic limb socket systems that typically used either no vacuum, or vacuum, positive pressure and messy lubricant during donning and doffing, or such strong sustained vacuum for suspension that a protective liner or insert was required to protect the patient&#39;s residual limb from injury. The present invention simplifies the socket to residual limb interface, eliminates the need for a complicated liner or insert, and introduces portability while being readily retrofit to existing sockets of the first type of system.  
      It is to be understood that both the foregoing general description and the following detailed description are exemplary and provided for purposes of explanation only, and are not restrictive of the invention, as claimed. Further features and objects of the present invention will become more fully apparent in the following description of the preferred embodiments and from the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      In describing the preferred embodiments, reference is made to the accompanying drawing figures wherein like parts have like reference numerals, and wherein:  
       FIG. 1  is an exploded perspective view, with a socket in cross-section, of a first preferred embodiment of a prosthetic limb having a power evacuation valve.  
       FIG. 2  is a view of the invention in  FIG. 1 , but with a patient&#39;s stump of a residual limb in the socket and the power evacuation valve connected to the socket.  
       FIG. 3  is a perspective view of a second preferred embodiment of a power evacuation valve of the present invention, with a housing having an integral valve body with a radial diffuser.  
       FIG. 4  is a perspective view of a third preferred embodiment of a power evacuation valve of the present invention, with a valve body mounted to a housing and the valve body having a diffuser screen.  
       FIG. 5  is a fourth preferred embodiment of a prosthetic limb, with a socket in cross-section and having a power evacuation valve housing removably mounted to the socket remotely from a valve body connected to the socket.  
       FIG. 6  is an exploded perspective view of a valve body for use with a remotely mounted power evacuation valve, such as is shown in  FIG. 5 .  
       FIG. 7  is a partially exploded perspective view of a fifth preferred embodiment of a power evacuation valve, with a remote valve body, a rechargeable battery, and first and second housing portions separated for better viewing.  
    
    
      It should be understood that the drawings are not to scale, provide simplified representations of some components, and provide examples of a variety of embodiments that may employ features as desired for the particular application, and are not intended to limit the scope and spirit of the present invention. While considerable mechanical details of a power evacuation valve, including other plan and section views of the particular components, have been omitted, such details are considered well within the comprehension of those skilled in the art in light of the present disclosure. It also should be understood that the present invention is not limited to the preferred embodiments illustrated.  
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      Referring generally to  FIGS. 1-7 , it will be appreciated that the power evacuation valve of the present invention generally may be embodied within numerous configurations for use with a prosthetic limb socket. Moreover, the invention may be retrofit for use with existing prosthetic limbs having the above-mentioned first type of system.  
      Referring to a preferred embodiment in  FIG. 1 , a prosthetic limb L is shown having a formed socket  10  with an upper end  12 , and a molded-in-place fitting  14  having a threaded aperture  16 . Alternatively, aperture  16  may be formed or cut directly into the material of socket  10 . The prosthetic limb L further includes a lower fitting  18  for attachment to a down-tube  20 . Mounted at the distal end of down-tube  20  is a foot structure  22 . Socket  10  is open at its upper end  12  for receipt of a stump  30  of a residual limb  32  of an amputee patient. It will be appreciated that the power evacuation valve of the present invention may be adapted for use with various artificial limbs, whether for arms, upper legs, lower legs or other uses as needed. Also, while the artificial limb L is shown in a simplified format, it will be understood that any of the many types of artificial limbs may include more sophisticated structures with articulating joints or flexible members as appropriate. Moreover, the materials used in such artificial limbs are not the subject of this invention, and therefore, may be of conventional materials in present use or of any other materials suitable for the particular use.  
      Shown in  FIG. 1  is a simplified representation of donning sock  34  for use by a patient to use to cover stump  30  to facilitate insertion of stump  30  into socket  10 . A donning sock may be made of a variety of materials and need not necessarily be closed at one end. Also shown in  FIG. 1  is a first embodiment of a power evacuation valve  40  of the present invention. Power evacuation valve  40  has a housing  41  shown with a first housing portion  42  and a second housing portion  43 . The housing portions may be separate pieces or joined by an integral hinge, and may form a closed body in a variety of ways, such as by snap fit or by fastener(s). A valve body  44  is connected to housing  41  and extends outward therefrom. Valve body  44  (and the other valve bodies disclosed herein) may include an o-ring to achieve a more secure seal to socket  10  when installed. In this embodiment, and the alternative embodiments shown in  FIGS. 2 and 3 , valve body  44  is formed integrally with first housing portion  42 . Also shown in  FIG. 1 , received within first housing portion  42  is an electric pump  50 , electrically connected, such as by wires, to an electrical switch  52  and to a power source  54 , shown as a series of batteries  56  in a holder  58 . To complete the circuit, the electrical switch  52  also is electrically connected, such as by wires, to power source  54 . Electrical switch  52  is connected to second housing portion  43 , for ease of activation by the patient.  
      Electrical pump  50  is shown connected in fluid communication with valve body  44  via a conduit  60 . In this embodiment, further connected in line with conduit  60  is a one-way regulator valve  70 . Also connected in fluid communication with electrical pump  50  is an exhaust conduit  62 . With a housing  41  that is not fully sealed, it is possible to vent or exhaust electrical pump  50  within housing  41  without experiencing back pressure. It will be appreciated that as an alternative to one-way regulator valve  70 , a one-way exhaust valve may be used in fluid communication with electrical pump  50 , such as at exhaust conduit  62 .  
      To engage stump  30  with socket  10  of prosthetic limb L with the present invention, a patient typically will cover stump  30  with donning sock  34 , remove valve body  44  from the aperture  16 , and stretch donning sock  34  (or otherwise guide an elongated donning sock) so as to be able to thread an end of donning sock  34  through aperture  16 . The patient then will insert sock covered stump  30  through open upper end  12  and into socket  10  while grabbing hold of donning sock  34  to pull it through aperture  16  and remove it from the stump  30 , leaving the skin on the surface of stump  30  in direct contact with the inner surface of formed socket  10 . After removal of donning sock  34 , or alternatively if the patient chooses to insert stump  30  into socket  10  without use of donning sock  34 , the patient will then reinstall valve body  44  into aperture  16 . This will effectively seal the interior of socket  10  around its periphery via contact with the skin of stump  30 .  
      However, by employing the present invention, the patient may activate electrical switch  52  to energize electrical pump  50  to remove any air trapped between stump  30  and socket  10 . Importantly, electrical pump  50  is to be of a type that will draw very low vacuum, ideally of less than 3 inches of mercury, or will be a relatively small pump, for example, Part Number VMP1621CN-06-50 distributed by Virtual Industries, Inc., which runs on 6 volts, and draws 1-10 inches of mercury, or any one of other suitable miniature vacuum pumps such as are available from the same distributor. Such types of pumps may be used in conjunction with a bleeder or regulator valve  70  to prevent the actual vacuum drawn from exceeding a preselected value that is chosen so as not to risk injury to the patient&#39;s stump  30 , such as 3 inches of mercury or less, or with an automated system that seeks to maintain the vacuum within a preselected range. The battery power required is dependent on the type of electrical pump used, and may be met by use of a series of 3 volt watch batteries, such as model CR2025 Energizer® brand batteries. This low sub-atmospheric pressure helps achieve better engagement between the skin of stump  30  and the interior surface of socket  10  to enhance the retention or suspension of prosthetic limb L, without causing injury to the patient.  
      In  FIG. 2 , donning sock  34  has been removed and the skin of the patient&#39;s stump  30  of residual limb  32  is in direct contact with the interior surface of socket  1 . Stump  30  is held securely in socket  10  of prosthetic limb L by the vacuum produced by power evacuation valve  40  installed in aperture  16 .  
      Turning to  FIG. 3 , an alternative embodiment is shown, where power evacuation valve  140  has a housing  141  with an integrally formed valve body  144 . Valve body  144  receives a press-fit diffuser  145 . For example, diffuser  145  may be a screen insert having an outer ring and a micromesh screen, which helps reduce the likelihood of injury to the patient by dispersing the suction of the electrical pump over a larger area. In addition, the screen of diffuser  145  helps keep the electrical pump clean by removing contaminants, such as dead skin folicals. First housing portion  142  also is made to accept a second housing portion  143 . As mentioned above, it will be appreciated that housing portions may be connected in many ways, one of which is shown in  FIG. 3 . Second housing portion  143  has tabs  147  that engage slots  148  in an end wall of first housing portion  142 , and a threaded fastener  149  is used to engage a threaded aperture (not shown) in first housing portion  142 . Also shown in  FIG. 3  is a port  180  for receipt of a fitting of an electrical recharger for a rechargeable battery, as will be discussed in more detail in reference to the embodiment shown in  FIG. 7 .  
       FIG. 4  illustrates a further alternative embodiment of a power evacuation valve  240 . Power evacuation valve  240  is somewhat similar to the embodiment shown in  FIG. 3 , with a second housing portion  243  that connects to a first housing portion  242  with tabs  247  that engage slots (not shown), and a threaded fastener  249  that engages a threaded aperture (not shown) in first housing portion  242 . However, power evacuation valve  240  is shown in an inverted position, with housing  241  end-to-end relative to the view of housing  141  in  FIG. 3 , and includes alternative structures for second housing portion  242  and valve body  244 . As shown, valve body  244  is connected about a peripheral rim to second housing portion  242 , and has an alternative diffuser  245 . Diffuser  245  has a series of radial channels  290  in fluid communication with a central channel  292  that is in fluid communication with an electrical pump (not shown). Diffuser  245  may be integrally formed with valve body  244  or may be a separate component fitted to valve body  244 . Diffuser  245  allows the end of valve body  244  to contact the skin of the patient&#39;s stump  30  without the channels  290  being in direct contact with the patient&#39;s skin. This structure also permits a single micromesh screen to be used with the central channel  292  if desired, and channel  292  can be enlarged within valve body  244  for use of a large screen component (not shown). Shown in this particular view is an electrical switch  252  and an exhaust port  264 , both on a side wall of housing  241 , as will be discussed in greater detail in reference to the embodiment shown in  FIG. 7 .  
      Turning now to  FIG. 5 , a further alternative embodiment of a power evacuation valve  340  of the present invention is shown. With this alternative embodiment, a valve body  344  is spaced from a housing  341 . This embodiment still permits the valve body  344  to be retrofit into an aperture  16  of an existing socket  10  of a prosthetic limb L, but also allows housing  341  to be placed in a position remote from valve body  344 . The valve body  344  is connected via conduit  360  to housing  341 , as well as to an electrical pump (not shown) in housing  341 . In  FIG. 5 , housing  341  is shown connected to an exterior surface of socket  10  near its upper end  12 . Housing  341  is shown as including a first housing portion  342  and a second housing portion  343 , and may be mounted to socket  10  permanently, or may be removably connected to socket  10  such as by a strap, a clamp, a hook and loop fastener system, or the like, for the convenience of the patient. In this view, stump  30  is fully inserted into socket  10  and the skin of stump  30  is already in direct contact with the interior surface of socket  10 . With this embodiment, housing  341  may remain in place while valve body  344  is removed to permit insertion of stump  30  into socket  10 .  
       FIG. 6  presents an exploded view of valve body  344 , connected to a conduit  360 . Valve body  344  may be remote from the housing of the power evacuation valve and preferably has a recess to receive a diffuser  345  that includes a press-fit screen. As with the embodiment shown in  FIG. 3 , the screen of diffuser  345  of  FIG. 6  preferably includes an outer ring and a micromesh screen to disperse the affects of the suction generated while also removing contaminants. It will be appreciated that the diffuser may be embodied in alternative structures and may use alternative filter materials if desired.  
      Turning to  FIG. 7 , a further alternative embodiment of a power evacuation valve  440  is shown, with housing  441  having a first housing portion  442  separated from second housing  443 . Second housing portion  443  has tabs  447  that engage slots  448  in first housing portion  442 , and a fastener  449  to secure second housing portion  443  to first housing portion  442 . With second housing portion  443  removed, one can see that switch  452  is electrically connected, such as by wires, to electrical pump  450  and to a suitable rechargeable battery  482 . In turn, electrical pump  450  is electrically connected to rechargeable battery  482 , such as by wires. Rechargeable battery  482  is chosen in accordance with the power requirements of electrical pump  450 , and is further electrically connected to recharger port  480 , such as by wires, to permit engagement by a recharger, as illustrated by recharger plug  484 .  
      The embodiment in  FIG. 7  has a valve body  444  connected to housing  441  by conduit  460 . In addition, valve body  444  is connected in fluid communication with an inlet of electrical pump  450  by conduit  460 . Preferably, conduit  460  includes a regulator valve  470  to assist in achieving and maintaining a preselected pressure that will prevent injury to the patient&#39;s stump. It will be appreciated that regulator valve  470  may be of any suitable type and preferably is adjustable, such as by adjustment screw  472 , or by automated electrical control means (not shown), and preferably incorporates a one-way valve to prevent leakage of air into the socket. The outlet of electrical pump  450  is shown as connected in fluid communication with an exhaust port  464  via conduit  462 . It will be understood that conduit  462  may incorporate a regulator and/or one-way valve to achieve the particular design objectives desired.  
      Thus, it will be appreciated that the present invention can be adapted for use to overcome the disadvantages with existing or previously proposed prosthetic limb systems that either have no supplementary means to achieve sub-atmospheric pressures, or have complicated systems that are messy and inconvenient, or that develop such high sub-atmospheric pressures that they require a protective cover for the patient&#39;s stump or some form of an alternative insert to be mounted to the patient&#39;s stump for insertion into the socket of a prosthetic limb. The present invention is the first system known to the inventor to be able to be used with existing prosthetic limbs, in place of a simple plug or one-way valve, and which is completely portable so as to travel with the prosthetic limb and provide low vacuum levels that will not injure the patient when exposed directly to the skin of the patient&#39;s stump and will enhance suspension of the prosthetic limb. In addition, the invention can be employed in original equipment designs to optimize the size, location and efficiency of the components utilized. In either event, the present invention provides an elegant solution due to its simplicity and ability to be retrofit for immediate use by many, many patients that are not in a position to purchase or be fitted with the more complicated systems that require protective stump covers or socket inserts to be able to withstand the much higher and potentially injurious sub-atmospheric pressures developed in such prior art systems, or that do not want to be hampered by the need to use a lubricant for donning and the insecurity that an adequate engagement and suspension will be maintained after the donning process is completed.  
      It will be appreciated that a power evacuation valve in accordance with the present invention may be provided in various configurations. Any variety of suitable materials of construction, configurations, shapes and sizes for the components and methods of connecting the components may be utilized to meet the particular needs and requirements of an end user. It will be apparent to those skilled in the art that various modifications can be made in the design and construction of such a power evacuation valve without departing from the scope or spirit of the present invention, and that the claims are not limited to the preferred embodiments illustrated.