Sonomyography (SMG) control for powered prosthetic hand: a study with normal subjects

Area of Science:

• Biomedical Engineering
• Rehabilitation Technology
• Musculoskeletal Biomechanics

Background:

• Sonomyography (SMG), derived from ultrasonography, measures muscle thickness changes during contraction.
• Previous research established SMG for skeletal muscle functional assessment and potential in prosthetic control.

Purpose of the Study:

• To investigate the feasibility of using one-dimensional SMG (1-D SMG) signals for controlling a single-degree-of-freedom powered prosthesis.
• To evaluate the performance of 1-D SMG control in visual pursuit tracking of prosthetic hand opening and closing patterns.

Main Methods:

• Nine healthy subjects participated, with SMG signals recorded from the extensor carpi radialis muscle.
• Subjects performed wrist extension to match prosthetic hand movements to target patterns (sinusoid and square waves) at varying rates.
• Control performance was quantified using normalized root mean square (RMS) tracking error.

Main Results:

• Mean RMS tracking errors were 12.8 ± 3.2% for sinusoid tracks and 14.8 ± 4.6% for square tracks.
• Statistical analysis (ANOVA) revealed significant effects of movement rate (p = 2.0 x 10⁻⁶) and track type (p = 0.007) on tracking errors.

Conclusions:

• 1-D SMG signals demonstrate feasibility for controlling a powered prosthesis.
• SMG shows potential as an alternative control method for prosthetic devices, pending further development.