Randomized Controlled Trial of Supercharged End-to-Side (SETS) Anterior Interosseous Nerve Transfer for Severe Cubital Tunnel Syndrome

Null hypothesis: Ulnar nerve decompression with or without supercharged end-to-side (SETS) anterior interosseous nerve transfer for McGowan classification stage III cubital tunnel syndrome results in similar ulnar intrinsic motor recovery.

Background Functional motor recovery distal to a peripheral nerve lesion is predicated upon time to reinnervation of the motor end plate and the number of regenerate axons that reach the target. Supercharged end-to-side (SETS) transfer of the anterior interosseous nerve to the motor fascicle of the ulnar nerve at the level of the distal forearm has been proposed as an adjunct procedure in severe cubital tunnel syndrome to augment motor recovery of the ulnar-innervated intrinsic muscles. The proposed mechanism of action of SETS is twofold: (1) "babysitting" the motor end plates until native regenerate axons reach their target, and (2) augmented partial recovery through axonal growth through the new pathway.

Multiple Level IV Therapeutic studies and a systematic review of Level IV Therapeutic studies have reported favorable clinical and electrodiagnostic outcomes following SETS for cubital tunnel syndrome, with low rates of complications. However, in the absence of controls, it remains unclear what proportion of the observed intrinsic motor recovery is attributable to the SETS procedure. Koriem et al. recently published a prospective, randomized comparative study of ulnar nerve repair with or without SETS for proximal ulnar nerve injuries and demonstrated superior intrinsic recovery and claw correction with the SETS procedure. Prospective, randomized trials of SETS for severe cubital tunnel syndrome are needed.

The objective of this study is to compare the results of ulnar nerve decompression with or without SETS for severe cubital tunnel syndrome. In this study, severe cubital tunnel syndrome is defined as McGowan classification stage III disease (sensory deficits, motor deficits, and the presence of intrinsic atrophy).

Methods Patient Selection A prospective, randomized controlled trial will be conducted at two participating institutions: Brigham and Women's Hospital and Beth Israel Deaconess Medical Center. Inclusion criteria are patients 18 years of age or older indicated for surgical treatment of severe cubital tunnel syndrome at one of the two participating institutions. Inclusion criteria furthermore includes a preoperative nerve conduction study and electromyography documenting ulnar neuropathy at the elbow with present fibrillations and positive sharp waves in the FDI or ADM within one year of surgery. Severe cubital tunnel syndrome is defined in this study as McGowan classification stage IIB or III disease (sensory deficits, motor deficits, and the presence of intrinsic atrophy). Exclusion criteria include ulnar nerve transections, traumatic brachial plexus injuries, brachial plexus neuritis (e.g. Parsonage-Turner), cervical radiculopathy, primary motor neuropathy (e.g. Charcot-Marie-Tooth), prior cubital tunnel surgery, and oncologic etiologies of ulnar nerve compression. Exclusion criteria additionally include patients who are not capable of decision-making or are unable to understand the study procedures. Non-English speaking patients are excluded since our secondary outcome variables may not have been translated and validated in other language(s). Comorbid carpal tunnel syndrome, concomitant carpal tunnel release, comorbid diabetes mellitus, and internervous connections such as Martin-Gruber connections are not criteria for exclusion.