Study: Load-adaptive Devices Could Help Lighten the Load for Amputees

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Researchers conducted a study to test powered robotic devices among people with transfemoral amputations in more challenging real-world situations, such as when the user carries groceries or a backpack. The results suggest that this population could benefit from load-adaptive powered knee controllers.

"We wanted to first understand how load affects amputees' walking with normal prosthesis settings that are typically prescribed in the clinic, and then to what degree different settings could benefit them," said Andrea Brandt, a PhD student in the North Carolina State University and the University of North Carolina-Chapel Hill Joint Department of Biomedical Engineering.

Five people with a transfemoral amputation participated in the study, which focused on a powered knee prosthesis with a motor to actuate the knee and a fixed ankle joint. The participants walked with and without load (i.e. a weighted backpack) and a powered knee prosthesis with two pre-programmed controller settings (i.e. for load and no load). The research team recorded the subjects' kinematics, kinetics, and perceived exertion.

After walking on a lab treadmill with and without the backpack that added 20 percent of his or her body weight, and with or without the load-bearing power settings, each participant reported having more difficulty when carrying the load when the prosthetic device was set at the normal setting. When subjects did not carry load, their perceived exertion and gait performance did not significantly change with controller settings.

"Perceived exertion definitely increased, the device would hyperextend, and people relied more on their intact limb, which is already being overused," Brandt said. "Those problems were reduced when the device was set to the load-bearing setting."

Editor's Note This story was adapted from materials provided by North Carolina State University.