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As an amputee, Carl was familiar with the problems amputees experience on a daily basis.  In a field that severely lacked research and development funding, the central problem that no manufacturer had resolved before was volume loss in the stump.  With conventional prosthetic devices the repeated pressure on the stump forced body fluids upward into the leg, eventually shrinking the size of the limb and loosening the prosthesis.  The loosened fit caused friction - leading to common side effects of painful blisters, rashes, chafing and even ulcers.


For many amputees using a prosthetic device, mobility was limited to only a few steps at a time before movement became painful.

He had been an active athlete and did not want to give up on athletic activities.  He wanted to be able to be able to wear a prosthesis for an entire day, doing what he wanted, and not have any soreness issues, which was not possible with the existing technology.

With a commitment to making a difference in the lives of amputees, in 1978 Carl founded Northwestern Artificial Limb and Brace, a manufacturing company that heavily invested in research and development. Carl and his company quickly earned a reputation as the industry innovator.

Carl says the development work of prosthetics at the time was more like that of a machinist, but the research he was conducting took him on a different path.  He developed a prosthesis built from urethane.  The connection between it and the residual limb had a better fit and was more comfortable.   However, his work did not end there. 

He then developed a vacuum pump within an artificial limb to hold the prosthesis in place.  The idea for using a vacuum pump came to him while visiting a friend who works in a wood shop.  Rather than using clamps to hold the wood in place and in an effort to keep marks off the wood, the wood was held in place by a vacuum. 

Working with St Cloud State University he developed a vacuum-assisted socket system, the Harmony® VASS™.  With each step, the vacuum maintains a balanced volume in the stump, practically eliminating shrinkage of the stump and the related painful side effects.  The technology creates a seal that not only holds the prosthesis in place, it also keeps the connection dry.  The vacuum pump Carl developed allows the person using it to have a greater range of motion.

Carl continues to refine the vacuum strategy to improve control for amputees and to improve the  environment for the residual limb.  His latest contribution is a custom fabricated, multi-surface socket.  Improved suspension can be accomplished by increasing the vacuum, but merely increasing the vacuum provides very little suspension along the vertical sides of the socket.  Carl explains, using the analogy of a suction cup used to lift a plate of glass.  When the glass is horizontal you can lift the glass, when the glass is vertical it can slide along the suction cup and fall to the ground.  His solution is using a socket with an inner surface that is textured.   When vacuum is applied to the socket, the gel liner is drawn into the textured surface, adding friction, increasing the surface area, and significantly increasing the linkage between the liner and the socket. The new socket system is called the EMS socket.   


While his business has been successful, the most rewarding result for Carl has been the remarkable increase in mobility and comfort for amputees, giving them back their independence and in many cases, their self-esteem.  His innovations, including 18 patents, have enhanced the quality of life for amputees around the world.

Note: This short biography has been compiled from information in the nomination form submitted to the Minnesota Inventors Hall of Fame and from information available on the Internet and a variety of other sources.

Carl A. Caspers

Carl A. Caspers, a St. Cloud entrepreneur, has devoted his life pursuing technology to provide amputees with a well-fitting prosthetic leg.   His inventions, including a urethane liner and a vacuum pump, have allowed him and others to lead more active lives. 


When Carl was 18 an accident left him without part of his right leg. While no one who has lost a limb would admit that was a good thing, the reality is that good came from this very traumatic event.  “The first prosthesis I had was terrible,” he says.  “I really paid a price when I wore it.  I just knew there had to be a better way.”


In search of a more comfortable and functional socket, Carl became interested in prosthetic limb design. He studied the science of prosthetics and human physiology at Northwestern University. He graduated in 1967 and became a certified prosthetist/orthotist.

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