This past week the New England Journal of Medicine reported an interesting advance in prosthetic limbs - the development of nerve controlled robotic limbs. The original article can be accessed here.

Although robotic hands and arms*, and even a few experimental legs have been built before in robotics labs around the world, this new result incorporates the patient's original nerves in a new way. Specialized surgeons redirect the severed nerves into part of the thigh muscle, resulting in small muscle twitches in the upper leg when the patient tries to move their non-existent lower leg and foot. Sensors attached to the thigh muscle can detect these twitches, and control servos and motors in an electronic prosthetic.

The researchers claim that this new technology allows patients to operate their prosthetic in much the same way as people move their legs normally. As the technology develops, patients should be able to walk on uneven ground or ascend and descend stairs without thinking about it. 

The work was done as a collaboration with Vanderbilt University in Nashville and researchers from Northwestern University in Evanston, Illinois, and the University of Seattle, funded by an $8 million dollar grant from the US military.

*It should be noted here that similar technology does exist for arms and hands, but is not necessarily as precise. An arm can move roughly and make small errors without major negative effects. However a leg must not only take the entire weight of the patient, but a slight mistake in position can cause a fall and significant injury. Therefore a proper nerve controlled leg must be more accurate and reliable than an arm or hand.