Air pressure differences noted with elevated vacuum socket

BOSTON Р­Maria Gerschutz, PhD, presented research on air pressure conditions experienced by residual limb skin at the American Orthotic & Prosthetic Association National Assembly, here.

“This study expands the understanding of elevated vacuum sockets and might help you understand the affect that a socket fit might have on a patient,” she said.

Gerschutz’s study included one K3 transtibial amputee with an elevated vacuum prosthesis. Gerschutz examined the air pressure levels at the interface between the skin and the prosthetic liner under different vacuum pressure settings, in different locations and under different socket fit conditions: poorly fitting (6-mm reduction in distal liner thickness) and well-fitting.

Teflon tuning was connected to four measurement locations on the residual limb: distal, medial side of the tibia, lateral side of the tibia and proximal. Gerschutz used vacuum pressures of 0 inches of mercury (inHg), 14 inHg and 20 inHg while the subject walked in each of the two sockets.

“The air pressures were measured, and for stance phase, we saw that positive air pressures were generated, and for swing phase, we saw that negative air pressures were generated,” Gerschutz said. “It varied according to testing conditions.”

Gerschutz said she observed two trends throughout the study. As the vacuum increased due to the increased liner, the researchers saw greater negative pressure during ambulation. The second trend was a slight pressure gradient in between the distal and proximal measurements, and greater negative pressure was generated distally.

For more information:

Gershutz M. Air pressure conditions experienced by residual limb skin active vacuum suspension (CSM). Presented at the American Orthotic & Prosthetic Association National Assembly 2012. Sept. 6-9, Boston.

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