Concentric Versus Delta Bipolar Probes for Intraneural Fascicle Selection: A Rabbit Model Study

L. Marina Ono, E. Sanz, M. Arenillas, M.C. Morillo, R. Giannetti, J.D. Muñoz Frías, E. Alonso, L. Cristóbal, A.A. Maldonado

Plastic and Reconstructive Surgery-Global Open Vol. 14, nº. 6, pp. e7851

Summary:

Background: Bipolar stimulating probes are widely used during intraoperative monitoring in nerve surgery. However, there are no reports comparing different types of bipolar probes. We present the differences between 2 different bipolar probes (concentric and Delta) in a rabbit animal model for brachial plexus injury, focusing on their applicability for intraoperative neuromonitoring in peripheral nerve surgery.

Methods: Using a previously described rabbit animal model, the biceps brachii muscle’s compound muscle action potentials (CMAPs) were recorded after stimulation with increasing intensities (ranging from 0.2 to 3 mV) of the middle and lower trunks using both concentric and Delta probes. The correlation between stimulus intensity and CMAP amplitude was studied, as well as interstimulus amplitude variability.

Results: Five rabbit brachial plexuses were studied. CMAP amplitude ranged from 0 to 9 mV. No correlation was found between stimulus intensity and CMAP for the Delta probe (Spearman rank test R = 0.181; P =0.264). A strong correlation was found between stimulus intensity and CMAP using the concentric probe (Spearman rank test R = 0.74; P = 0.001). The Delta probe showed less variability (coefficient of variation 0.01 versus 0.1).

Conclusions: Delta probes elicit highly reproducible, high-CMAP amplitude responses even with low-intensity stimuli. Concentric probes produce slightly less reproducible, progressively higher CMAP amplitudes with increasing stimulus intensities.

Spanish layman's summary:

Se han comparado diferentes electrodos EMG en modelos de cirugía nerviosa en conejos. Las sondas delta dieron señales musculares fuertes y repetibles incluso con baja estimulación. Las concéntricas aumentaron de forma más predecible, pero fueron algo menos reproducibles.

English layman's summary:

We tested different EMG probes in a rabbit nerve-surgery model. Delta probes gave strong, repeatable muscle signals even at low stimulation. Concentric probes rose more predictably with stronger stimulation, but were slightly less reproducible.

Keywords: peripheral nerve surgery; intraoperative neuromonitoring; EMG probes; cirugía nerviosa periférica; neuromonitorización intraoperatoria; electrodos EMG;

JCR-JIF Impact Factor and WoS quartile: 1,800 - Q2 (2024)

DOI reference: https://doi.org/10.1097/GOX.0000000000007851

Published on paper: June 2026.

Published on-line: June 2026.

Citation:
L. Marina Ono, E. Sanz, M. Arenillas, M.C. Morillo, R. Giannetti, J.D. Muñoz Frías, E. Alonso, L. Cristóbal, A.A. Maldonado, "Concentric Versus Delta Bipolar Probes for Intraneural Fascicle Selection: A Rabbit Model Study", Plastic and Reconstructive Surgery-Global Open, Vol. 14, nº. 6, pp. e7851, June 2026. [Online: June 2026] doi: 10.1097/GOX.0000000000007851