SP04. Abductor Digiti Minimi Turbocharged End-to-side Nerve Transfer is a Novel Technique to Restore Ulnar Motor Function
Year: 2023
Type: article
Abstract: PURPOSE: Supercharged end-to-side (SETS) anterior interosseous nerve transfer (AIN) to reinnervate the ulnar intrinsic musculature is an increasingly accepted mode of treatment following ulnar nerve injury. However, results can remain suboptimal if the critical threshold number of axons innervating the intrinsic muscles is not reached. The recent use of the abductor digiti minimi (ADM) as a nerve transfer to reinnervate the recurrent motor nerve suggests that it is relatively expendable and may be used as a donor nerve in severe ulnar neuropathy to augment the number of axons reaching the critical ulnar intrinsics. This study hypothesizes that redirecting the ADM to the ulnar motor nerve (UMN) distally in a turbocharged end-to-side fashion (TETS) either alone or with concomitant AIN nerve transfer in a super-turbocharged (STETS) fashion may improve functional recovery. METHODS: A retrospective study of patients who underwent turbocharged (TETS) ADM to UMN or combined super-turbocharged (STETS) AIN and ADM to UMN nerve transfers for severe ulnar nerve injuries was performed. Primary outcomes were improvement in first dorsal interosseous (FDI) Medical Research Council (MRC) strength, pinch strength, grip strength, Visual Analogue Scale pain (VAS) score, and Disabilities of the Arm, Shoulder, and Hand (DASH) scores. Dichotomous and continuous variables were compared with Fisher’s exact and t tests, respectively. RESULTS: Thirty-two patients with severe ulnar nerve injuries were identified in this study with greater than 1 year follow-up after surgery. Seven patients underwent turbocharged ADM transfer, and 25 patients underwent combined super-turbocharged AIN and ADM to UMN nerve transfers from June 2020 to September 2021. Symptom duration prior to surgery was an average of 13.3 months with an average age at surgery of 51 years. Nerve conduction studies confirmed ulnar nerve injury with severely diminished compound motor action potentials in the ADM and FDI of 2.70 and 2.92 in the turbocharged ADM and 1.33 and 1.35 in the super-turbocharged AIN and ADM nerve transfer groups. Electromyography also demonstrated reduced FDI motor unit action potentials in all patients with severely reduced, single, or no action potentials in 57% of turbocharged AIN and 76% of super-turbocharged AIN and ADM nerve transfer groups. Post-operatively, the turbocharged ADM nerve transfer group demonstrated significant decrease in DASH scores from 52 to 25 (p=0.031), VAS pain scores from 5.7 to 2.0 (p=0.005), and improved FDI MRC from 2.3 to 3.4 (p=0.015) with a trend toward increased pinch and grip strength. The super-turbocharged AIN and ADM nerve transfer group demonstrated significant increase in pinch from 5.1 to 8.5lbs (p<0.001), grip from 39 to 57lbs (p<0.001), FDI MRC from 1.1 to 3.4 (p<0.001), and decreased DASH and VAS pain scores from 54 to 28 (p=0.002) and 4.8 to 1.3 (p<0.001), respectively. CONCLUSION: This study presents the novel use of distally redirecting the ADM nerve to innervate critical ulnar intrinsics and reports outcomes in a patient cohort with long-term severe ulnar neuropathy. These findings suggest that incorporating the ADM nerve transfer into the current AIN SETS procedure will optimize patient outcomes and warrant further investigation with prospective cohort studies.
Authors: David Chi, Lauren Bechtold, Susan E. Mackinnon
Institution: Washington University in St. Louis
Language: English
Subfield: Surgery
Field: Medicine
Domain: Health Sciences
Open Access status: gold
Estimated APC paid: $2,195
OpenAlex ID: W4384948575