Media release

From: Springer Nature

Neuroscience: This bionic leg is made for walking *BRIEFING*

A neuroprosthetic interface that allows a bionic leg to be fully responsive to the human nervous system is reported in a paper published in Nature Medicine. The interface, comprising surgically constructed agonist-antagonist muscle pairs that restore natural proprioception (the ability to sense limb position and movement), resulted in improved walking control in a clinical trial involving 14 people with below-the-knee amputation. These findings suggest that even partial reinstatement of neural signaling may be sufficient to enable clinically relevant improvements in neuroprosthetic functionality.

Restoration of normal gait in people with below-the-knee amputations remains limited despite the increasing technological sophistication of limb prostheses. To create movement of a limb through its range of motion, muscles act in agonist–antagonist pairs, which in turn transmit proprioceptive signals to the central nervous system, providing humans an awareness of their limbs’ positions and movements. However, surgical amputation of a limb results in considerably impaired neural–muscle architecture within the amputation site, referred to as the residuum, as severed muscles are wrapped to create ample soft tissue padding for comfortable prosthetic socket use, disrupting natural muscle dynamics and proprioception.

Hugh Herr and colleagues generated a neuroprosthetic interface consisting of surgically connected agonist–antagonist muscle pairs with sensing electrodes. These dynamic muscle pairs are surgically constructed within the residuum and serve as neuroprosthetic control and proprioceptive sources for the people with leg amputation. The interface allows neural control information from a patient to be conveyed to an external limb prosthesis, and further provides the proprioceptive sense of prosthetic positions and movements back to the user.

The authors then tested the efficacy of the bionic prosthetic leg in a clinical trial of 14 participants with unilateral below-the-knee amputation, 7 of whom had the neuroprosthetic interface. Compared with the walking speed of individuals with below-the-knee amputation without the neuroprosthetic interface, the walking speed of the participants increased by 41%, which enabled walking speeds equivalent to those of people without leg amputation. Furthermore, walking performance was improved in real-world environments, including slopes, stairs and obstructed pathways.

The authors suggest that their findings could inform future reconstruction techniques that seek to restore neural control of human locomotion in the context of limb amputation or motor paralysis.

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