Validity and reliability of an electromyography-based similarity index to quantify lower extremity selective...

Area of Science:

• Neuroscience
• Biomedical Engineering
• Rehabilitation Medicine

Background:

• Selective voluntary motor control (SVMC) is crucial for functional mobility.
• Objective quantification of SVMC in children with cerebral palsy (CP) remains challenging.
• Existing assessments may lack precision in measuring subtle motor control deficits.

Purpose of the Study:

• To introduce and evaluate a novel neurophysiology-based measure, the Similarity Index (SI_SCALE), for quantifying SVMC.
• To assess the preliminary validity and reliability of the SI_SCALE in children with CP.
• To explore the potential of SI_SCALE for refined assessment of motor impairments.

Main Methods:

• Combined the Selective Control Assessment of the Lower Extremity (SCALE) with surface electromyography to derive the SI_SCALE.
• Investigated concurrent validity by correlating SI_SCALE with established measures (SCALE, GMFCS) in 24 children with CP.
• Assessed discriminative validity by comparing SI_SCALE scores between children with CP and 31 neurologically intact peers.
• Quantified test-retest reliability using intraclass correlation coefficients (ICC) and minimal detectable change (MDC).

Main Results:

• The SI_SCALE demonstrated strong concurrent validity, correlating highly with the SCALE (ρ=0.90) and inversely with the GMFCS (ρ=-0.74).
• Children with CP exhibited significantly lower SI_SCALE scores compared to their healthy peers, indicating discriminative validity.
• Test-retest reliability was good for both affected and unaffected legs (ICC ≥ 0.84, MDC ≤ 0.17).

Conclusions:

• The SI_SCALE shows promising preliminary validity and reliability for assessing SVMC in children with CP.
• This neurophysiology-based approach offers a more precise and objective method for evaluating motor control.
• Future research should investigate the responsiveness of the SI_SCALE to interventions.