The Super-Turbocharged End-to-Side Abductor Digiti Minimi and Anterior Interosseous Double Nerve Transfer Is Associated With Improved Ulnar Intrinsic Function

Background: Nerve transfers to reinnervate ulnar intrinsic musculature can restore function in severe ulnar neuropathy, and supercharged end-to-side (SETS) nerve transfers have garnered early adoption. Given the relative expendability of the abductor digiti minimi (ADM), redirecting its axons to more critical components of the ulnar motor nerve (UMN) in a turbocharged end-to-side (TETS) nerve transfer with concomitant anterior interosseous SETS nerve transfer (AIN) as a super-turbocharged end-to-side (STETS) or twin-charged double nerve transfer may improve functional recovery.

Methods: A retrospective study of patients undergoing the STETS AIN/ADM to UMN double nerve transfer or TETS ADM to UMN nerve transfer for severe ulnar neuropathy between 2020 and 2022 was performed. Primary outcomes were improvement in first dorsal interosseous (FDI) strength and Disabilities of the Arm, Shoulder, and Hand (DASH) scores. Dichotomous and continuous variables were compared with χ² and t tests, respectively.

Results: Fifty patients with severe ulnar nerve injuries were identified with at least 1-year surgical follow-up. Preoperative symptom duration was an average of 11.3 months. The STETS cohort (n = 42) reported significantly decreased DASH scores from 58 to 28 (P < .001) and improved FDI Medical Research Council (MRC) score from 0.7 to 3.3 (P < .001). The TETS cohort (n = 8) reported significantly decreased DASH scores from 54 to 23 (P = .016) and improved FDI MRC score from 2.0 to 3.6 (P = .008).

Conclusions: Distal transfer of the ADM nerve to the ulnar deep motor branch in a turbocharged fashion is reported. The findings suggest that the STETS double nerve transfer may improve patient outcomes and warrants further investigation with prospective cohort studies.