Guyon's canal decompression at the time of AIN to ulnar motor nerve transfer: To release or not to release?
Sasha Gabrielle Létourneau, MD1, Eric C Mitchell, MD, MSc1, Juliana Larocerie-Salgado, MSc, OT Reg. (Ont.), CHT2, E. Ali Bateman, MD, MSc1, Thomas Miller, MD3,4, Douglas Ross, MD, MEd5,6 and Stahs Pripotnev, MD1,6, 1Western University, London, ON, Canada, 2Roth-McFarlane Hand and Upper Limb Centre, London, ON, Canada, 3Rehabilitation Medicine/ Hand and Upper limb Centre, University of Western Ontario, London, ON, Canada, 4Parkwood Hospital, London, ON, Canada, 5Plastic and Reconstructive Surgery, St. Joseph's Health Care Center, Western University, London, ON, Canada, 6Roth | McFarlane Hand and Upper Limb Centre - St. Joseph's Health Care, London, ON, Canada
Introduction:
The supercharged end-to-side anterior interosseus to ulnar motor (AIN-to-UM) nerve transfer is widely used as an adjunctive procedure in the management of severe ulnar neuropathy at the elbow. Although Guyon’s canal release (GCR) with AIN-to-UM nerve transfer was initially done to delineate intraneural topography of the ulnar nerve, most surgeons no longer consider it necessary for that reason. Conversely, surgeons still commonly perform GCR at the time of AIN-to-UM nerve transfer, based on the rationale that decompression reduces potential distal “roadblocks” to axonal regrowth from both the transfer and the ulnar nerve. However, convincing evidence to support the benefit of routine GCR is lacking. The purpose of this study was to determine whether GCR improves outcomes in AIN-to-UM nerve transfer.
Materials & Methods:
We conducted a retrospective cohort study of AIN-to-UM nerve transfers performed with or without GCR at our center from January 1st, 2019 to December 31st, 2021 by three surgeons, two of whom routinely performed GCR and one who did not. Patients with pre- and post-operative electrodiagnostic data at and/or beyond their one-year follow-up were included. Demographics, surgical details, and changes in pre- and post-operative clinical and electrodiagnostic findings were compared using descriptive and statistical analysis (p<0.05).
Results:
Of the 69 AIN-to-UM nerve transfers reviewed, 47 met inclusion criteria, including 22 performed with GCR. All patients had modified McGowan grade 3 ulnar neuropathy. The two groups did not differ significantly (p>0.05) in terms of demographic or surgical characteristics (Table 1). Additionally, there were no significant differences (p>0.05) in change in grip or key pinch strength, 5th digit sensory nerve action potential (SNAP) or intrinsic muscle compound muscle action potential (CMAP) amplitudes (Table 2). Finally, nascent motor unit action potentials were found on EMG at the last follow-up in 7 (31.8%) patients who had undergone GCR and in 7 (28.0%) who had not (p<0.05).
Conclusions:
This study sought to investigate the impact of GCR on outcomes in AIN-to-UM nerve transfers. Preliminary results suggest this additional procedure may not provide clinical or electrodiagnostic benefit in AIN-to-UM nerve transfers. Future directions include identifying subpopulations who could benefit from GCR.
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