  Impairment of hand functions in individuals with spinal cord injury (SCI)
severely disrupts activities of daily living. Recent advances have enabled
rehabilitation assisted by robotic devices to augment the residual function of
the muscles. Traditionally, non-invasive electromyography-based peripheral
neural interfaces have been utilized to sense volitional motor intent to drive
robotic assistive devices. However, the dexterity and fidelity of control that
can be achieved with electromyography-based control have been limited due to
inherent limitations in signal quality. We have developed and tested a
muscle-computer interface (MCI) utilizing sonomyography to provide control of a
virtual cursor for individuals with motor-incomplete spinal cord injury. We
demonstrate that individuals with SCI successfully gained control of a virtual
cursor by utilizing contractions of muscles of the wrist joint. The
sonomyography-based interface enabled control of the cursor at multiple graded
levels demonstrating the ability to achieve accurate and stable endpoint
control. Our sonomyography-based muscle-computer interface can enable dexterous
control of upper-extremity assistive devices for individuals with
motor-incomplete SCI.
