The double-wall socket system is designed to give above knee amputees a prosthesis that fits intimately and provides increased control and security. An added benefit is that the comfortable trim lines allow for a larger range of motion.
A silicone liner is rolled onto the residual limb. If the limb is relatively uniform in shape, an “off the shelf” will be used. For those residual limbs with bony prominences, neuromas, etc., a custom liner will be designed. All of our medical grade silicone liners are fabricated on-site in our liner manufacturing lab.
The second component of the system is the prosthetic sock. These socks are layered on top of the liner and act as a wick between the liner and the socket. Socks also accommodate for volume changes within the residual limb.
Next, the inner cup is slid over the prosthetic sock. This is where the POA system is different from others. A vacuum chamber laminated into the cup will allow even pressure to be distributed over the entire residual limb. A sealing sleeve, which is attached to the inner cup, is then rolled up to seal against the liner.
Lastly, the outer socket (with the knee and foot attached) is placed over the inner cup and the two pieces are locked together with a pin. Air is evacuated from the socket through a one-way expulsion valve which creates suction. This provides the intimate fit that results in the feeling that the prosthesis is a part of you.
Our NPS system removes air from the space between a sheath or sock, the socket of the prosthesis and the liner. The suction created by the removal of the air attaches the liner evenly to the socket wall without squeezing. The liner acts like a “second skin,” so the residual limb is not directly exposed to the suction. Unlike other prosthetic suspension systems which focus the weight and force of the prosthesis on one point at the bottom of the socket, suction systems spread the pressures evenly over the entire socket. The limb does not shift within the socket because captured air is forced out through an opening at the bottom of the socket, a one-way valve that closes the opening.
NPS sockets provide a superior interface with skin and tissue. Studies have shown that conventional methods of interfacing residual limbs with prosthetic devices decrease blood flow and oxygenation of tissue, cause blisters, traps perspiration, and causes sores and abrasions. The NPS Socket promotes healthier skin and increased comfort.