New device could help make prosthetic legs less painful

Prosthetic legs could become less painful thanks to new research paving the way for sockets that better accommodate swelling in amputees’ limbs.

Researchers at the University of Washington in the US have created a device to monitor how prostheses users’ limbs swell and shrink throughout the day, which they hope will enable them to predict how and when swelling will take place.

This data could lead to the design of more robust and flexible sockets, potentially even guiding technology such as vacuum-suction systems that can be used to adjust the fit of prosthetic legs and keep users’ own limbs snug inside them.

‘This provides us a window into what’s happening,’ said principal investigator Joan Sanders, a UW professor of bioengineering. ‘Each person has his or her own characteristics and qualities that affect how limb volume changes. You really have to look at each person on a case-by-case basis.’

Soft tissues in a prosthesis socket swell and shrink often during the day due to fluid volume changes caused by physical activity (or lack thereof) and salty foods.

The device uses electrodes to calculate the amount of fluid change in the limb.

These changes can cause pain to amputees wearing prostheses with fixed sockets and they may have to manually adjust the fit of the limb by adding or removing fabric socks or remove it altogether.

The Washington system is worn around the waist and calculates the percentage increase or decrease of fluid volume in a patient’s limb using data from small electrodes placed in different spots on the leg.

The engineers spent the last two years testing a large prototype on about 60 patients in their Seattle lab but have now developed a more portable version.

Trial patients are asked to go through a routine that includes sitting, standing and walking, and data is transmitted wirelessly to a tablet computer that displays the changes in limb size about 15 times a second.

Researchers are using the device to monitor fluid changes in amputees’ limbs as they exercise.

The researchers hope clinics could go through a similar routine to help track an individual’s swelling and shrinking patterns.

They plan to build a smaller device that patients could wear for several weeks to monitor changes in their limb size as they go about their daily routines.