Subcutaneous Versus Submuscular Anterior Transposition of the Ulnar Nerve for Cubital Tunnel Syndrome: A Systematic Review and Meta-Analysis of Randomized Controlled Trials and Observational Studies.

Subcutaneous and submuscular anterior ulnar nerve transposition have been widely used in patients with cubital tunnel syndrome. However, the reliable evidence in favor of 1 of 2 surgical options on clinical improvement remains controversial. To maximize the value of the available literature, we performed a systematic review and meta-analysis to compare subcutaneous versus submuscular anterior ulnar nerve transposition in patients with ulnar neuropathy at the elbow. PubMed, Cochrane Library, and EMBASE databases were searched for randomized and observational studies that compared subcutaneous transposition with submuscular transposition of ulnar nerve for cubital tunnel syndrome. The primary outcome was clinically relevant improvement in function compared to the baseline. Randomized and observational studies were separately analyzed with relative risks (RRs) and 95% confidence intervals (CIs). Two randomized controlled trials (RCTs) and 7 observational studies, involving 605 patients, were included. Our meta-analysis suggested that no significant differences in the primary outcomes were observed between comparison groups, both in RCT (RR, 1.16; 95% CI 0.68-1.98; P = 0.60; I2= 81%) and observational studies (RR, 1.01; 95% CI 0.95-1.08; P = 0.69; I2 = 0%). These findings were also consistent with all subgroup analyses for observational studies. In the secondary outcomes, the incidence of adverse events was significantly lower in subcutaneous group than in submuscular group (RR, 0.54; 95% CI 0.33-0.87; P = 0.01; I2 = 0%), whereas subcutaneous transposition failed to reveal more superiority than submuscular transposition in static two-point discrimination (MD, 0.04; 95% CI -0.18-0.25; P = 0.74; I = 0%). The available evidence is not adequately powered to identify the best anterior ulnar nerve transposition technique for cubital tunnel syndrome on the basis of clinical outcomes, that is, suggests that subcutaneous and submuscular anterior transposition might be equally effective in terms of postoperative clinical improvement. However, differences in clinical outcomes metrics should be noted, and these findings largely rely on the outcomes data from observational studies that are potentially subject to a high risk of selection bias. Therefore, more high-quality and adequately powered RCTs with standardized clinical outcomes metrics are necessary for proper comparison of these techniques.