Intramuscular EMG after targeted muscle reinnervation for pattern recognition control of myoelectric prostheses

This study provides a description of the properties of the intramuscular electromyogram (imEMG) after targeted muscle reinnervation (TMR) surgery, and a preliminary comparison of pattern recognition myoelectric prosthesis control between surface EMG (sEMG) and imEMG in TMR muscle. Fine wire imEMG and sEMG were simultaneously recorded from reinnervated sites in 5 subjects who had TMR surgery. Subjects trained a 7-motion-class linear discriminant classifier, and provided visually-guided ramped contractions to evaluate mean absolute value (MAV) as a measure for proportional velocity control. Characteristics of imEMG in TMR muscle varied with reinnervation site and the contractions´ motion class. Signals with large, sparse motor units and signals resembling normal muscle were both observed. For each subject evaluated, use of imEMG provided no substantial change in classification error than when using sEMG signals. However, at TMR sites with large, sparse motor unit action potentials, the recruitment of such motor units may limit the controllability of mid-range speeds using MAV.