Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Leg – Socket holder
Reexamination Certificate
1999-05-05
2002-01-01
Snow, Bruce (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Leg
Socket holder
C623S038000
Reexamination Certificate
active
06334876
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to prosthetics, and, more specifically to a safety suction valve that synchronously actuates a latch mechanism and valve mechanism during donning/doffing of a stump socket and during use of a prosthesis, and an alignment kit/method that allows easy and inexpensive alignment of the prosthesis.
2. Background of the Related Art
It has long been appreciated that differential air pressure or “suction” may be utilized to retain or “suspend” a prosthetic limb on an amputee's stump. Gravitational and other forces tend to cause separation between the prosthetic limb and the patient's residual extremity during use. This happens, for example, during the swing phase of gait, when a prosthetic leg is additionally subjected to centrifugal forces. Patients have routinely worn a variety of belts, straps, cuffs and harnesses to retain their prosthetic limbs against separation from the residual limb. But such devices are inconvenient and tend to cause chafing against the patient's body giving rise to sores and abrasions.
The manner in which an artificial limb is suspended and/or attached to the residual limb determines the amount of control an amputee has over the prosthesis. Suction suspension typically involves the utilization of a socket liner and a “hard” stump socket. The liner, which is usually fabricated from silicone, fits snugly over the residual limb and is, in turn, enveloped by the socket. A region of negative pressure between the liner-sheathed stump and the interior of the socket serves to hold the prosthesis upon the limb during use. The suspension method is very advantageous for the amputee. It gives the amputee the ability to better control the prosthesis and provides for useful sensory or proprioceptive feedback. Suction suspension also makes a prosthesis feel lighter as compared to other forms of suspension.
Some form of valve means is usually employed to regulate the air pressure in the socket such that undesirable pressure differentials do not prevent or complicate the donning and doffing of the socket. The valve means also maintains the suction or negative pressure once the socket has been satisfactorily clad. During donning, the patient's liner-sheathed stump is inserted into the socket. At some stage or stages during the insertion the socket liner will form a roughly circumferential air-tight seal through contact with the hard socket. As the patient's stump is inserted further into the socket, air pressure builds up under the stump. The provision of valve means permits air to escape from the socket until the pressure inside the socket equalizes with the ambient pressure and, hence, allows the stump to be fully inserted inside the socket. As a result, when the stump is completely inserted in the socket, the air pressure is equal inside and outside the socket. The valve means are now closed so that no air is allowed to flow into the distal end of the stump socket. Any tendency to remove the stump from the socket would increase the space between the inner socket wall and the stump, reducing the pressure inside the socket, since external air is unable to enter. The difference between the ambient pressure and the reduced pressure within the socket creates a “suction” effect that acts to maintain the socket on the stump. In this manner, the prosthesis is “suspended” on the patient's stump. During removal of the stump from the socket (or doffing) the valve means are opened or adjusted so as to equalize the ambient pressure and the pressure inside the socket, thus dissipating the “suction” effect and allowing for an easy removal of the stump.
There are several suction valves available in the market today. One class of valves consists of a valve and seat combination in which the valve and seat are threadably engaged. The seat is side-mounted on to the distal end of the socket and the valve/seat assembly is usually disengaged during donning and doffing. Another type of suction valve is an automatic air expulsion one-way valve which automatically exhausts air from the socket during donning, thereby permitting insertion of the stump into the socket. The one-way valve may be manually operated, during doffing, to allow air to pass from the outside into the interior of the socket.
Though the principle of employing “suction” for “suspending” an artificial limb is quite clear, there are some associated practical problems. One of these is the difficulty in providing a reliable and permanently effective seal at the proximal open end of the socket This issue being important in maintaining the reduced pressure inside the socket. Moreover, in some instances it is doubtful whether the suspending suctional force can independently support the weight of the lower limb prosthesis. This is problematic from a safety stand-point, because if the suspension means fail, and there is no redundant or back-up support mechanism, the artificial limb could detach from the patient's stump.
U.S. Pat. No. 5,376,131 to Lenze et al. sets forth a socket with an elastic diaphragm that sealingly engages a patient's stump, and hence attempts to provide an effective seal, but the local constriction due to such a tightly fitting diaphragm can result in impairment of circulation in the amputee's residual limb. Suspension sleeves, which are substantially elongated bands fabricated from a resilient material and envelop part of the stump and part of the outer socket, have been used to provide complementary mechanical support and may additionally function in some capacity as a sealing means. But since these sleeves constrictingly grip the residual limb over a wide region they can limit limb movement or otherwise be uncomfortable.
A different approach to tackling this problem has led to the design of a socket liner which is attachable at its distal end to a socket or artificial limb. In this manner, the liner is mechanically secured and can provide additional suspension, if needed, and/or can play the role of a backup suspension means. Typically, the socket liner is equipped with a detachable attachment component, at its distal end, which mates with a locking device and hence secures the residual limb to an artificial limb. The locking devices generally employ a spring-loaded clutch mechanism or a pin-lock mechanism to lock on to the liner attachment component. This attachment component is either a barb-shaped structure or a frictionally-retained pin. These attachment components can lock in a plurality of positions which affects the overall length of the prosthesis. Though this may be advantageous in some cases, it can make it difficult for the patient to consistently achieve the same prosthetic configuration when the residual limb and the artificial limb are articulated. It should further be noted that in this mode of limb suspension the locking means and the valve means are autonomous entities which are separately invasive and additive in weight on the distal end of the socket.
Another type of suspension device which is in widespread use today is known as a roll-on suction socket. The suction socket, which is typically fabricated from silicone, is basically a long tubular structure with one open end. The distal end of the suction socket is attachable to a prosthesis via an attachment component and a locking device employing the same principle and design described above. During donning, the suction socket is turned inside out and rolled on to the residual stump in a fashion basically the same as donning a condom, being careful to avoid trapping of any air between the skin of the limb and the suction socket. Since the suction socket creates/destroys a partial vacuum at its distal end during rolling-on/rolling-off of the socket the function of a valve means are intrinsically incorporated into the donning/doffing technique. Thus, it would appear that the suction socket is a simple and effective device to suspend a prosthesis. But, this can be misleading because the suction socket may not be
Pedersen Barbara S.
Pedersen Ken J.
Snow Bruce
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