The standard concentric needle cannula cannot replace the Macro EMG electrode

•Concentric needle EMG needle cannula cannot be used as a substitute for the costly standard Macro EMG needle because there were different motor unit amplitudes between superficially and more deeply recorded motor units with the concentric needle cannula.•There was no deep dependency when using the standard Macro electrode regarding the motor unit amplitudes.•This deep dependency when using the concentric needle EMG cannula for recording is probable due to different degree of so called shunting effect which depends on the length of the exposed concentric needle cannula.

ObjectiveTo establish the usefulness of the single use and affordable standard concentric EMG electrode as a substitute for the expensive standard macro electrode.MethodsMacro EMG performed with macro electrode is compared with recordings from the uninsulated cannula of a standard EMG electrode at two different recording depths in the tibialis anterior muscle. This was performed both in muscles with signs of collateral reinnervation and without.ResultsThe amplitude of the motor units recorded with the uninsulated concentric needle cannula were lower for the deeply recorded motor units compared to motor unit potential (MUP) amplitudes recorded with the standard macro electrode. The deeply recorded concentric needle (CN) cannula recorded MUPs amplitudes were also lower than superficially recorded CN cannula MUPs. The standard Macro EMG signals show no difference between deeply and superficially recorded motor units.ConclusionThe uninsulated cannula of the concentric needle electrode cannot replace the standard Macro EMG electrode due to technical reasons, probably from different effects of shunting of the bare cannula in deep vs. superficially recorded motor units.SignificanceThe standard CN electrode could not be used as substitute for the standard Macro EMG needle.