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  Elevated Vacuum Suspension Systems:

Reprinted with permission of Miki Fairley

"It feels like I got my leg back!"

This is how amputee Andy May described the first time he ran with a prosthesis incorporating the new LimbLogic™ VS prosthetic vacuum suspension system from Ohio Willow Wood, Mount Sterling, Ohio.

Although every type of prosthetic suspension system has advantages and disadvantages, with no one system being right for everyone, elevated vacuum suspension offers significant benefits. "Time after time, patients have commented that now the prosthesis feels like a part of them," says Jeff Denune, CP, LP, Ohio Willow Wood clinical director of prosthetics. With their previous prostheses, amputees would experience pistoning or other movement within the sockets, which made them continuously aware of them. "It's sort of like dentures," he explains. "When you wear them, you always know they're in there."

Steve Smith, BSc, director of technical service for Smith Global, Laurie, Missouri, agrees. "Amputees feel more as though the prosthesis is an extension of their body, with more proprioception and stability.

One of the most important benefits of elevated vacuum suspension is that it maintains limb volume throughout the day. With other suspension systems, amputees' residual limbs lose volume as they go about daily activities. This loosens the socket, which makes controlling the prosthesis more difficult, reduces proprioception, and increases the potential for skin damage. The amputee may add more sock layers as the day goes on, but this is a time-consuming inconvenience for busy people.

Carl Caspers, CPO, pioneered the concept. His company, TEC Interface Systems, St. Cloud, Minnesota, developed the Harmony® VASS™ (Vacuum-Assisted Socket System) in cooperation with research by the St. Cloud University Human Performance Laboratory. TEC was acquired by Otto Bock HealthCare, Minneapolis, Minnesota, in 2003.

In addition to Otto Bock's Harmony and the LimbLogic VS, current elevated vacuum systems on the market include the eVAC® from Smith Global, with other companies poised to enter the marketplace.

Exciting Impact on Transfemoral Socket Design

Elevated vacuum suspension—also known as subatmospheric technology—also is having successful transfemoral and upper-limb applications. But it's the impact on transfemoral socket design that has Denune excited. With the elevated vacuum suspension system it has been possible to design transfemoral sockets with lower trimlines, greatly increasing amputees' comfort and range of motion. Denune first revealed the brimless socket design at the 2007 Annual Meeting of the American Academy of Orthotists and Prosthetists (the Academy) in 2007. "We've been getting phone calls from all over the world; clinicians are saying they've been able to cut the brim down. The floodgates have opened."

With other transfemoral designs, whether ischial containment, narrow M-L, or others, the "sitting bone," or ischium, sits in the socket, which creates discomfort for the amputee.

"Traditionally, transfemoral sockets have been made with walking in mind, and all of the design changes have focused on holding the prosthesis securely while the person is standing up and in motion," Doug Smith, MD, medical director for the Amputee Coalition of America (ACA), explains in the article "Great Prosthetic Components Are Good, but a Good Socket Is Great" (inMotion, September/October 2004). However, the optimal shape for walking is not the best shape for sitting, Smith notes. A transfemoral socket molds up to or around the ischium to transfer weight when the person is upright; however, the socket can dig uncomfortably into the groin and buttocks when the person is seated. "Technically, it's hard to design one socket that's optimal for both sitting and standing," says Smith.

A landmark socket design, the M.A.S. socket by Marlo Ortiz, unveiled in 1999, allows far more comfort, range of motion, and cosmesis than previous designs. However, Denune notes that the socket is somewhat difficult and complex to fit and depends on a skeletal lock for control.

Commenting on one of Ohio Willow Wood's test patients, Denune says, "He's able to do things that [are] just amazing to see. He feels secure on his limb. It doesn't move in the socket, and we're able to cut the trimlines down very low."

Miki Fairley is a contributing editor for The O&P EDGE and a freelance writer based in southwest Colorado. She can be contacted via e-mail at miki.fairley@gmail.com

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Carl Caspers, CPO, pioneered the concept. His company, TEC Interface Systems, St. Cloud, Minnesota, developed the Harmony® VASS™ (Vacuum-Assisted Socket System) in cooperation with research by the St. Cloud University Human Performance Laboratory. TEC was acquired by Otto Bock HealthCare, Minneapolis, Minnesota, in 2003.

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