American Society for Peripheral Nerve

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Anterior Interosseous-to-Ulnar Motor Nerve Transfer in Chronic Ulnar Neuropathy
Graham J McLeod, BSc. MD, PGY-51, Tanis Quaife, BSc. MD, PGY-21, Tod A. Clark, MD, FRCSC2 and Jennifer Lindsay Giuffre, MD, FRSCS3, (1)University of Manitoba, Winnipeg, MB, Canada, (2)Department of Orthopedics, University of Manitoba, Pan Am Clinic, Winnipeg, MB, Canada, (3)Section of Plastic Surgery, University of Manitoba, Pan Am Clinic, Winnipeg, MB, Canada

Hypothesis:The transfer of the terminal branch of anterior interosseous nerve (AIN) into the deep ulnar motor nerve branch improves intrinsic hand function in patients with high ulnar nerve injuries by providing motor input closer to the motor end plates. We report outcome measurements of this nerve transfer in patients with compressive ulnar neuropathy and hypothesize that any improvement in intrinsic hand function is beneficial to patients.

Methods:A retrospective review was conducted of all AIN to ulnar motor nerve transfers, including both end-to-side (ETS) and end-to-end (ETE) transfers, from Jan 2011 to October 2018 performed by 2 surgeons. All adult patients that underwent the nerve transfer for compressive ulnar neuropathy (cubital tunnel syndrome), with >6 month follow-up and completed charts were included. Primary outcome measures were motor function using the British Medical Research Council (BMRC) grading system.Secondary outcome measures included complications and donor site deficits. Preoperative nerve conduction studies were also reviewed.

Results:Of sixty-five patients (mean age 56.1, 68% male) who underwent the nerve transfer, 32 patients met the inclusion criteria. The average follow-up was 12 months. The average time to surgery from initial injury or symptom onset was 14.1 months. The overall average BMRC was 2.94/5 with a statistically significant better recovery in patients who received earlier surgery (<12months =BMRC 3.73, >12months =BMRC 2.24, p-value <0.01). Patients with an ETS neurorrhaphy had a trend towards better results that those with an ETE neurorrhaphy (ETS = BMRC 3.24, ETE =2.6). All patients who underwent nerve transfer had severe compressive ulnar neuropathy with intrinsic wasting (McGowan 3). All patients at final follow-up, regardless of BMRC grade, had a positive Froment's sign and some wasting of their first dorsal interosseous muscles. Therefore, recovery of intrinsic function was measured by the ability to abduct/adduct fingers and loss of Wartenburg's sign. There were no donor deficits post-operation. One patient developed CRPS post-operation.

Conclusions:Patients with earlier surgery and receiving an ETS transfer showed improved recovery with a higher BMRC grade compared to those who underwent later surgery and/or and ETE transfer. Despite evidence of significant intrinsic wasting, patients that received surgery within 12 months of motor symptom onset had improved function with relatively higher BMRC scores. Even patients with low BMRC scores reported improved hand dexterity in follow up. We would recommend this surgery for patients with chronic compressive ulnar neuropathy, as any improvement is hand function is beneficial.

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