Abductor Digiti Minimi and Anterior Interosseous to Ulnar Motor Nerve Transfer: The Super Turbocharge End-to-Side Transfer

Summary: Anterior interosseous nerve to ulnar motor nerve supercharged end-to-side (SETS) nerve transfer to restore intrinsic function is a recently adopted nerve transfer in severe ulnar neuropathy. Its success is predicated on the critical threshold number of axons innervating the intrinsic muscles. Given the relative expendability of the abductor digiti minimi (ADM) muscle and the critical function of the other intrinsic muscles, the authors modified their SETS transfer to redirect axons from the ADM to turbocharge the ulnar motor nerve to innervate the more critical intrinsic muscles. They refer to this procedure as a super turbocharged end-to-side (STETS) procedure. The ADM has been used previously as a muscle/tendon transfer for thumb opposition and more recently as a nerve transfer to reinnervate the thenar branch of the median nerve. Although current methods of assessment of reinnervation are likely unable to differentiate between contributions from the anterior interosseous nerve SETS versus ADM STETS transfer, this technique follows the fundamentals of modern nerve surgery, where directing the maximum number of nerve fibers in a timely fashion to the most critical target is paramount for the best functional recovery. The authors suggest that the STETS technique may optimize outcomes in ulnar neuropathy without additional patient morbidity.