Supercharged End-to-Side Anterior Interosseous-to-Ulnar Motor Nerve Transfer: A Systematic Review and Meta-analysis

Purpose Ulnar nerve (UN) injuries frequently result in intrinsic hand muscle weakness and functional impairment, particularly in high-level lesions where prolonged axonal regeneration limits recovery. The supercharged end-to-side (SETS) anterior interosseous nerve (AIN)-to-ulnar motor nerve transfer was developed to enhance distal reinnervation and preserve intrinsic motor endplates. This study aimed to evaluate outcomes following SETS AIN-to-ulnar motor nerve transfer for UN pathology. Methods A systematic review and meta-analysis were conducted in accordance with Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines. MEDLINE, PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) were searched. Studies reporting postoperative outcomes following SETS transfer for UN pathology were included. A random-effects meta-analysis was performed for binary outcomes. Results Sixteen studies comprising 447 patients met the inclusion criteria. The pooled rate of intrinsic muscle recovery, defined as Medical Research Council (MRC) grade ≥ 3, was 80.6%. Recovery to near-normal strength (MRC ≥ 4) was achieved in 64.4%. Subgroup analysis demonstrated a notably higher MRC ≥ 4 recovery rate in traumatic injuries (85.5%) compared with compressive (52.9%) or mixed pathologies (33.3%). Surgical intervention within 12 months was associated with notably improved MRC ≥ 3 recovery. Functional outcomes improved, with mean grip strength reaching 75.7% of the contralateral side. Residual clinical signs persisted, including Froment's sign (17.6%), ulnar clawing (12.1%), and Wartenberg's sign (59.1%). The overall complication rate was 7.9%. Conclusions SETS AIN-to-ulnar motor nerve transfer is a safe and effective adjunct for high UN pathology, particularly when performed early. Traumatic injuries demonstrate the highest rates of near-normal intrinsic recovery, although residual clinical signs may persist. Type of study/level of evidence Therapeutic III.