What is the difference between Vacuum and Suction suspension systems?
Both elevated vacuum suspension and suction suspension use a difference in atmospheric pressure to attach the socket to the residual limb, according to Ohio Willow Wood. As air is expelled from the prosthetic socket, your residual limb is pulled toward the socket wall and held in place by the force of negative air pressure as the vacuum effect is created. Suction suspension normally uses a passive expulsion valve to allow air to exit from the prosthetic socket but only creates a negative pressure differential when the prosthetic leg begins to move.
Vacuum suspension uses an active pump to create a negative pressure differential that doesn't depend upon the prosthetic leg position. In a suction socket you still have some movement, but with elevated vacuum you eliminate almost all pistoning.
Suction suspension basically is just a sealed chamber. Suction suspension is created during swing phase of gait, which creates the negative pressure required to suspend your prosthetic leg. To weight bear, you have to reseat your residual limb into the socket, creating forces on your limb. But with elevated vacuum, you're under vacuum continuously, so there is no pressure because your residual limb is held to the socket wall.
Elevated vacuum systems are the preferred method for those amputees with sensitive skin or vascular disorders including diabetes. The vacuum pump prevents your residual limb from significantly changing size during the day and the continuous vacuum aids in circulating fluid in and out of your residual limb at a constant rate. Whereas suction suspension allows fluid to leave your residual limb, but does not influence fluid to return like vacuum.
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