Time-frequency changes in electromyographic signals after hamstring lengthening surgery in children with cerebral...

Area of Science:

• Biomedical Engineering
• Orthopedic Surgery
• Pediatric Gait Analysis

Background:

• Cerebral palsy (CP) often causes increased knee flexion during stance in children.
• Distal hamstring lengthening surgery is a common treatment for CP gait deviations.
• Surface electromyography (sEMG) onset/offset timing shows limited post-surgical muscle activity changes.

Purpose of the Study:

• To investigate if time-frequency characteristics of sEMG, using wavelet analysis, correlate with improved gait kinematics after surgery.
• To explore the relationship between sEMG frequency characteristics and surgical intervention type in CP.
• To analyze changes in muscle activity patterns beyond simple onset/offset timing.

Main Methods:

• Collected sEMG data from medial hamstring (MH) and vastus lateralis (VL) muscles in children with typical development (TD) and CP, pre- and post-surgery.
• Applied wavelet transform for time-frequency analysis of sEMG signals.
• Utilized functional principal component analysis (PCA) to analyze sEMG characteristics.

Main Results:

• Pre-operative sEMG frequency differed based on surgical approach (bilateral vs. bone modification).
• Post-operatively, VL muscle frequency characteristics in CP children approached those of TD children, aligning with kinematic improvements.
• MH muscle frequency characteristics in surgical CP groups diverged from TD, reflecting structural muscle alterations.

Conclusions:

• Wavelet analysis of sEMG provides deeper insight into muscle activity changes post-CP surgery than traditional methods.
• Post-surgical improvements in gait kinematics are associated with normalization of vastus lateralis muscle activity frequencies.
• Medial hamstring muscle activity frequencies may reflect underlying structural adaptations following surgical intervention in CP.