Individuals with above-knee leg amputations have severely impaired mobility and a reduced quality of life. For the millions of people that have to rely on traditional leg prostheses, walking is highly inefficient because a large amount of the leg’s muscle is removed during surgery, which limits strength and range of motion. Walking under these conditions quickly leads to overexertion, as the residual-limb and intact muscles have to be coerced into unnatural walking movements.
An experimental exoskeleton, recently developed by a team of mechanical engineers at the University of Utah may help to restore mobility to amputees. The battery-powered exoskeleton fits around the leg and waist of the wearer to provide a boost while they are walking.
The exoskeleton (📷: M. Ishmael et al.)
An electric motor attached to the wearer’s thigh, just above the amputation site, helps reduce the effort required for the leg to perform walking motions. A harness at the waist contains custom electronics, sensors, and microcontrollers to control the leg-assist motor. An artificial intelligence algorithm has been trained to understand how the wearer moves, and ensure that walking motions are smooth and natural. The exoskeleton can provide assistance to the left or right leg by swapping the position of the motor unit.
The device was tested in a cohort of six people with above-knee amputations. They were asked to walk on a treadmill both with, and without, the exoskeleton. Metabolic rate was recorded during the trial, which served as a proxy for energy expenditure. On average, energy expenditure was found to decrease by 15.6% while wearing the device. To understand the significance of this finding, you can imagine that it is roughly equivalent to removing a backpack containing a 26 pound weight. The lightweight exoskeleton weighs in at just over five pounds.
Early users of the system have described it as being very close in feeling to walking on a natural leg. They have also described a feeling of being “fused” with the exoskeleton, which helps them move faster. While the initial trials have been small, this device looks like it has great potential to help amputees regain mobility. With funding already secured from the U.S. Department of Defense and National Science Foundation, further development of this exoskeleton may help more people to walk in the future.