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Intraoperative FCU CMAP Amplitude During Oberlin Nerve Transfer: Association with Reinnervation Timing and Functional
Diana M Ortega-Hernández1,2, Isabel Fernández-Conejero3, Aroa Casado-Rodríguez4
1Hand and Microsurgery Unit, Traumaunit, Teknon Medical Center, 08022 Barcelona, Spain.
Journal of Clinical Medicine
|April 14, 2026
Summary
Intraoperative mapping of flexor carpi ulnaris (FCU) compound muscle action potential (CMAP) amplitude aids donor fascicle selection for brachial plexus injury nerve transfers. Higher FCU CMAP amplitudes correlate with earlier electromyographic reinnervation but not final elbow flexion strength.
Area of Science:
- Neurosurgery
- Neurophysiology
- Orthopedic Surgery
Background:
- Selective ulnar nerve fascicle transfer to the musculocutaneous nerve restores elbow flexion after brachial plexus injury.
- Intraoperative neurophysiological mapping with compound muscle action potentials (CMAPs) aids donor fascicle selection.
- The prognostic value of intraoperative CMAP amplitude for functional recovery remains unclear.
Purpose of the Study:
- To evaluate the association between intraoperative flexor carpi ulnaris (FCU) CMAP amplitude and time to biceps brachii reinnervation.
- To assess the relationship between FCU CMAP amplitude and final elbow flexion strength.
- To determine if intraoperative CMAP amplitude predicts functional outcomes after selective nerve transfer.
Main Methods:
- Retrospective observational study of patients undergoing selective nerve transfer for brachial plexus injury.
- Intraoperative neurophysiological mapping with quantitative CMAP recordings from ulnar-innervated muscles.
- Analysis of time to electromyographic reinnervation and final elbow flexion strength (British Medical Research Council scale).
Main Results:
- Higher intraoperative FCU CMAP amplitudes were significantly associated with a shorter time to electromyographic reinnervation (Spearman ρ = -0.572, p = 0.0106).
- No significant association was found between FCU CMAP amplitude and final elbow flexion strength (Spearman ρ = -0.168, p = 0.479).
- A positive association existed between the injury-to-surgery interval and intraoperative CMAP amplitude (Spearman ρ = 0.681, p = 0.000943).
Conclusions:
- Intraoperative FCU CMAP amplitude is a valuable tool for objective donor fascicle selection and predicts earlier electromyographic reinnervation.
- FCU CMAP amplitude is not a reliable predictor of final elbow flexion strength in this cohort.
- Functional recovery after nerve transfer is multifactorial, influenced by determinants beyond single intraoperative measurements.
