Functional Recovery Following Nerve Transfer for Ulnar Nerve Injuries: A Systematic Review and Meta-Analysis

Introduction: High ulnar nerve injuries can severely impair hand function. Nerve transfer techniques, such as using the anterior interosseous nerve (AIN), offer a promising approach to restore function. By transferring the AIN to the ulnar motor nerve, these procedures aim to reinnervate intrinsic hand muscles before motor endplate atrophy occurs. Transfers can be performed in either an end-to-end or a supercharged end-to-side (SETS) fashion, with SETS preserving native nerve regeneration potential.

Methods: The systematic review followed the PRISMA guidelines. PubMed, Scopus, Embase, and Web of Science were searched up to October 25, 2024, for studies on nerve transfer for ulnar nerve injuries, without restrictions. Two reviewers independently screened and extracted data on study characteristics, outcomes, and complications, resolving disagreements through discussion. Risk of bias was assessed using the Joanna Briggs Institute’s checklists. Statistical analysis will use a random-effects model. Analyses will be conducted using R (version 4.2.3).

Results: Twenty-four studies with 634 patients were included. Ulnar nerve transfer, particularly the SETS technique, showed significant improvements in grip strength (SMD = 0.87 [0.03; 1.71], p = 0.0008, I² = 82.0%) and pinch strength (SMD = 1.08 [0.35; 1.81], p = 0.0012, I² = 77.8%). Subgroup analysis did not show significant differences between Pinch strength SETS, ETS, and ETE transfers (p = 0.1133). Compound muscle action potential (CMAP) for the abductor digiti minimi (ADM) improved significantly (SMD = 1.16 [0.58; 1.74], p < 0.0001, I² = 85.0%), with no significant difference between SETS and ETE transfers (p = 0.1082). High heterogeneity suggests the need to explore factors like technique type and patient characteristics.

Conclusion : This meta-analysis confirms that ulnar nerve transfer, especially using the anterior interosseous nerve (AIN), significantly improves hand function in high ulnar nerve injuries. SETS transfers showed potential benefits in grip and pinch strength, likely due to preserved native nerve regeneration. However, substantial heterogeneity among studies emphasizes the need for further research to refine surgical techniques, patient selection, and rehabilitation strategies.