Reverse End-to-Side Anterior Interosseous Nerve to Ulnar Nerve Transfer for Severe Ulnar Neuropathy at the Elbow
C. Doherty1; T.A. Miller, MD2; Douglas C. Ross1
1Roth | McFarlane Hand and Upper Limb Centre, Division of Plastic Surgery, University of Western Ontario, London, ON, Canada; 2Rehabilitation Medicine/ Hand and Upper Limb Centre, St. Joseph's Health Centre, University of Western Ontario, London, ON, Canada
Introduction: Ulnar nerve injury or severe nerve compression at the elbow is a difficult clinical problem as decompression or repair at this level may result in variable reinnervation of intrinsic hand muscles. Distal reverse end-to-side nerve transfers (anterior interosseous nerve to ulnar motor fascicles) have been suggested to “supercharge” or augment intrinsic hand muscle recovery while axons regenerate from the level of the elbow and have a significant theoretical advantage. There is little published about the efficacy of this technique.
Materials & Methods: Consecutive patients presenting between June 2013 and December 2013 who had repair of an ulnar nerve injury or severe compressive neuropathy (McGowan Grade III) at the elbow were considered for reverse end-to-side AIN to ulnar nerve transfer at the wrist. Consenting patients underwent nerve transfer by a single surgeon and followed post-operatively with electrodiagnostic studies and clinical evaluation. Changes in MRC grade and evidence of early intrinsic muscle reinnervation (6 months) on EMG were evaluated. Pinch strength and intrinsic hand function were also evaluated. In addition, strength and neurophysiology changes were measured with the forearm in neutral position and pronation (simulating AIN function).
Results: Six patients were eligible for review. Four patients suffered an ulnar nerve laceration with microscopic repair at the elbow and two had a severe compressive neuropathy. Average time from initial injury to transfer was 37.5 months (2 – 120 months). All patients had no recruitable motor units on pre-operative EMG of hand intrinsic muscles. All patients had intrinsic muscle wasting pre-operatively, which persisted post-operatively. Fifty percent (3/6) had an improvement in MRC grade by 6 months. Eighty three percent (5/6) of patients showed evidence of intrinsic muscle reinnervation at a time earlier than expected for regeneration from the elbow level (< 6 months). Eighty three percent (5/6) showed improvement in needle EMG studies with nascent units recruited during active forearm pronation, suggesting contribution of the AIN to the ulnar nerve motor fascicles.
Conclusion: The timing of clinical and electrophysiologic recovery suggests the AIN to ulnar reverse end-to-side nerve transfer enhances the results of surgery for severe ulnar neuropathy at the elbow.
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