Reverse End to Side Anterior Interosseous Nerve to Ulnar Nerve Transfer for Severe Ulnar Neuropathy
Christopher D Doherty, MD MPH FRCS(C)1; Thomas Miller, MD FRCPC1; Sol Gregory, MD FRCS(C)2; Brett Byers, MD FRCS(C)1; Douglas C. Ross, MD MEd FRCS(C)3; (1)Western University, London, ON, Canada, (2)Campbell River Hospital, Campbell River, BC, Canada, (3)Roth | McFarlane Hand and Upper Limb Centre, Division of Plastic Surgery, University of Western Ontario, London, ON, Canada
Purpose
The purpose of this study is to evaluate the reverse end to side anterior interosseous nerve (AIN) to ulnar nerve transfer for various forms of severe ulnar neuropathy.
Methods
This study is a retrospective analysis with approval from Western University Biomedical Ethics review board. Chart review was performed for consecutive patients presenting to our institution between January 1st 2013 and January 31st 2016 who underwent AIN to ulnar nerve reverse end to side transfer for severe ulnar neuropathy (intrinsic muscle wasting and weakness). All procedures were performed by two plastic surgeons with a subspecialty practice in peripheral nerve surgery. Medical Research Council (MRC) intrinsic strength, DASH, and Patient Rated Ulnar Nerve Evaluation (PRUNE) survey scores were reviewed. A subset of patients is presented with formal strength testing. Electromyography was used to determine if reinnervation was evident at an earlier than expected time post-operatively.
Results
Forty-five patients were reviewed. The mean follow-up was 16 months. Nine patients underwent nerve transfer for closed trauma, six for laceration and 30 for severe compressive ulnar neuropathy at the elbow (McGowan grade 3). Mean post-operative MRC scores for first dorsal interossei was comparable and not statistically significant between all groups: 3.11, 3.0 and 3.02 respectively. All groups had statistically significant improvements in MRC grade from pre-operative values. Regarding intrinsic strength, 79% of patients achieved MRC grade 3 or greater, 58% grade 4 and 6% grade 5. The mean time (months) to presence of nascent units on EMG was 7.33, 6.92 and 6.6 respectively, which is earlier than expected. In a subset of patients, mean pinch strength (kg) was 7.67 kg in the affected hand versus 11.72 in the unaffected hand.
Conclusions
Reverse end to side nerve transfer appears to improve intrinsic strength and clinical outcomes for patients with various forms of severe ulnar neuropathy. Results are similar between groups thus demonstrating expanding indications for this nerve transfer.
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