Association Between Clinical Outcome Measures and Sonomyography-Derived Metrics in Individuals with Spinal Cord Injury

Background: To examine the association between ultrasound-based muscle activity detection, or sonomyography (SMG) derived metrics, and clinical measures of upper-extremity function in individuals with cervical spinal cord injury (cSCI), and to evaluate SMG-based trajectories derived directly from muscle activity as a muscle-level assessment compared to conventional kinematic approaches. Methods: Eight individuals with cSCI (n = 8; American Spinal Injury Association Impairment Scale grades A to C; injury levels C5 to C6) participated. Participants performed a wrist tenodesis based target achievement task while SMG data were collected. SMG derived metrics were correlated with performance-based upper extremity function assessed using the Jebsen Taylor Hand Function Test (JTHFT) and self-reported function assessed using the Capabilities of Upper Extremity Questionnaire (CUE-Q). Associations were quantified using distance correlation (dCorr). Results: Strong associations between SMG-derived metrics and clinical measures were observed. Movement Arrest Period Ratio (MAPR) showed the strongest association with JTHFT performance (dCorr = 0.75), while Time to Peak Velocity (TTPV) demonstrated a moderate association (dCorr = 0.62). Rate of Change of Acceleration (ROCAcc) showed a strong correlation with CUE-Q scores (dCorr {approx} 0.70), and spectral arc length (SAL) showed moderate correlations (dCorr {approx} 0.66). Conclusions: SMG-derived metrics show meaningful associations with both performance-based and self-reported measures of upper-extremity function in individuals with cSCI. These findings suggest that SMG metrics can serve as objective tools to complement clinical assessments for tracking functional status and recovery. Larger studies are needed to confirm these observations.