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Electrodiagnostic abnormality characterization in pronator quadratus associated with end-to-side nerve transfers for ulnar neuropathy at the elbow: a retrospective study.
Veronica Pentland, MD Candidate
1, Raahulan Rathagirishnan, MD
2, B Ritsma, MD
1, J. Trier, MD
3, Parham Daneshvar, MD, FRCS(C)
4; J. Michael Hendry, MD, MSc, FRCSC
3(1)Queen's University, Kingston, ON, Canada, (2)University of Ottawa, Ottawa, ON, Canada, (3)Queen's University, Kingston, ON, Canada, (4)Orthopaedic Surgery, University of British Columbia, St. Paul's Hospital, Vancouver, BC, Canada
Background: Supercharged end-to-side (SETS) nerve transfer is an emerging surgical intervention for ulnar neuropathy at the elbow (UNE), offering the potential for improved motor recovery in severe cases. Preoperative electromyography (EMG) of the pronator quadratus (PQ), a surrogate for anterior interosseous nerve integrity, is routinely performed despite limited evidence supporting its utility in atraumatic UNE.
Methods: We conducted a retrospective cohort study of patients with electrodiagnostically confirmed, non-traumatic UNE evaluated for surgical treatment of UNE at a single academic institution. All patients underwent comprehensive electrodiagnostic testing, including EMG of the PQ muscle. The primary outcome was the prevalence of PQ abnormalities. Clinical and electrodiagnostic parameters were extracted to characterize the cohort.
Results: In our preliminary results, 25 patients met inclusion criteria (mean age 61 years; 24% female) and none demonstrated PQ abnormalities on EMG. All exhibited moderate-to-severe UNE with preserved median nerve function. Ulnar motor latency was prolonged, and compound muscle action potential amplitudes were reduced in all cases, consistent with isolated ulnar pathology. Clinical examination revealed high rates of intrinsic muscle atrophy (68%) and claw hand deformity (60%), further supporting advanced motor involvement.
Conclusions: In patients with atraumatic UNE, EMG of the PQ muscle revealed no donor nerve abnormalities, suggesting that routine assessment of the anterior interosseous nerve may be unnecessary in this population. Eliminating EMG of the PQ muscle from standard SETS preoperative protocols may streamline care, reduce healthcare burden, and expedite surgical intervention without compromising safety. These findings support a more selective, pathology-driven approach to donor nerve evaluation in the surgical management of UNE.
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