Title: Reverse End-to-side Anterior Interosseous to Ulnar Motor Nerve Transfer.
Published: 3/2/2011, Updated: 4/6/2011.
Author(s): Susan E. Mackinnon MD, Andrew Yee BS.
Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, St. Louis, MO.
The anterior interosseous to ulnar motor nerve transfer was first performed by Mackinnon SE in April of 1991 in a patient with a complete high ulnar nerve injury. Since then, the procedure has been used by our institution to recover some intrinsic function in patients with otherwise irreparable ulnar nerve injuries. However, there is a much larger population of patients with the varied ulnar intrinsic function: (1) patients with some, but not normal ulnar intrinsic function, (2) patients with good, but not certain likelihood of some intrinsic recovery with a more distal ulnar nerve repair, and (3) patients with high ulnar nerve injury, but have a martin-Gruber component to their ulnar intrinsic function. This larger population pool of patients, with indications that do not fall under the anterior interosseous to ulnar motor end-to-end nerve transfer, could utilize an augmentation of some ulnar nerve function with additional motor fibers. The anterior interosseous nerve (AIN) is also the donor nerve choice for augmentation of ulnar nerve intrinsic function. Rather than an end-to-end (ETE) nerve transfer with the AIN, a reverse end-to-side (RETS) nerve transfer is completed. That is, the end of the donor AIN is coaptated to the side of the recipient motor fascicular group of the ulnar nerve through an epineural window. This allows for the “supercharge” of the ulnar motor component. The RETS anterior interosseous to ulnar motor nerve transfer was first performed by our institution in August of 2009 and found, a year later, excellent recovery of ulnar nerve intrinsic function in a patient with recurrent cubital tunnel syndrome. The RETS procedure was performed after completing a rat experimental study, which definitively showed motor axons regenerating into a denervated nerve in a RETS fashion. This study was originally designed as a potential negative study, but surprisingly found equal transversing nerve fibers in the RETS coaptation when compared to an ETE coaptation. Since the experimental study, our institution has found many clinical situations where the RETS procedure has been an excellent addition to the surgical management of patients with ulnar intrinsic weakness.