Nerve anastomoses in the upper limb: an up-to-date meta-analysis

INTRODUCTION: There are numerous communicating branches (CB) between the nerves of the brachial plexus. Therefore, the objective of this study was to provide comprehensive data on the prevalence, morphometry, and anatomical classifications of upper extremity anastomoses such as: Martin-Gruber anastomosis (MGA), Marinacci anastomosis (MA), Riche-Cannieu anastomosis (CRA), Berrettini anastomosis (BA), median and musculocutaneous nerves anastomoses (MMA), or radial and lateral cutaneous nerve of forearm anastomosis (RLCA). MATERIAL AND METHODS: Major online medical databases such as PubMed, Embase, Scopus, ScienceDirect, Web of Science, SciELO, BIOSIS, Current Content Connect and Korean Journal Database were searched to gather all relevant studies regarding the anatomical characteristics of these structures. Finally, a total of 189 studies were included in this meta-analysis, based on 23,572 upper extremities. RESULTS: The prevalence of MGA was 20.74% (cadaveric studies), 18.93% (fetal studies), 16.65% (healthy subjects) and 20.37% (patients with carpal tunnel syndrom). The most prevalent was type II of the Oh et al. classification of MGA, occurring in 58.01%, and pattern I of Rodríguez-Niedenführ et al. classification, which resulted in 96.07%. Nevertheless the pooled prevalence of MA was 2.04%. The BA was found in 67.97% (cadaveric studies), 29.07% (fetal studies) and 11.88% (electrophysiological studies). CONCLUSION: This study represents the most extensive and up-to-date evaluation of nerve anastomoses in upper limb morphometry and anatomy up to date. Its findings provide an important reference for clinicians, particularly surgeons performing procedures in the upper extremities region.