Comparison of motor unit action potentials using monopolar vs. concentric needle electrodes in the middle deltoid and abductor digiti minimi muscles.

UNLABELLED

Electromyography readings are analyzed noting abnormalities in the parameters of amplitude, duration, and number of phases. Previous studies have demonstrated variability between monopolar needle electrodes (MNEs) and concentric needle electrodes (CNEs) in regard to the above parameters. We hypothesized that a difference in measured parameters would be observed due to the physical differences between the needles. Twenty-three subjects participated in this study. Five readings were recorded from the middle deltoid and the abductor digiti minimi muscles using the MNE, and five readings were recorded using the CNE. A minimal isometric contraction of the tested muscle in the subjects dominant arm was performed. A significant difference was found in amplitudes recorded by the MNE and CNE in both muscles. A significant difference was found in the ADM, and not in the deltoid, with regard to duration. The difference found in the number of phases was clinically insignificant.

DISCUSSION

The MNE detected larger amplitudes and durations because of its larger recording territory. The duration may also be affected by the distance between the active/reference electrodes.