Science News: AIN-to-ECRB Transfer Restores Wrist Extension After Complex Brachial Plexus Injury

Submitted by: Shaohua Xu, MD, PhD

Edited by: Rebecca O'Bryan, MD

Citation: Chim H, Tuffaha SH, Lu JC, Wrist Extension Reconstruction Using Distal Anterior Interosseous to Extensor Carpi Radialis Brevis Nerve Transfer in Brachial Plexus Injuries, Journal of Hand Surgery, February 01, 2026, Volume 51, Issue 2, Pages 175-180.e1

Summary:
The study reviews outcomes of the pronator quadratus branch of anterior interosseous nerve (AIN) to extensor carpi radialis brevis (ECRB) nerve transfer for restoring wrist extension in C5–C8 brachial plexus injuries, where donor options are limited. Across ten patients treated by three surgeons, 70% regained strong (M4, Medical Research Council grading system 4) wrist extension, typically emerging (M2 strength) around 12 months and strengthening (M4 strength) by 20 months postoperatively.

Patients who failed to reach M4 all had double fascicular transfers for elbow flexion and demonstrated a strong Oberlin effect, which appeared to interfere with independent wrist extension recovery. No patient lost pronation or function of FPL/FDP. The authors conclude that AIN to ECRB nerve transfer is an effective strategy for wrist extension reconstruction in high brachial plexus injuries, and outcomes may be more reliable when paired with a single ulnar fascicular transfer rather than median-based or double fascicular strategies.

Comments:
The concept of using the distal AIN (pronator quadratus branch) as a donor for wrist extension was first described by Bertelli in 2012 and later expanded in 2016. This is the first multi‑surgeon, multi‑institutional series specifically examining AIN to ECRB nerve transfer outcomes in C5–C8 root injuries, a uniquely challenging population with limited donor options. The study provides new insight into how concomitant elbow-flexion reconstruction strategies affect wrist-extension recover.

Why is this article interesting/relevant to the AANEM Audience?
The study provides real‑world evidence on how the distal AIN performs as a donor for reinnervating the ECRB. This is directly relevant to clinicians who interpret EMGs and counsel on nerve recovery timelines.