Comprehensive Summary of Anastomoses between the Median and Ulnar Nerves in the Forearm and Hand

Four main presentations of median-ulnar anastomosis exist. Those manifesting in the forearm include Martin-Gruber and Marinacci, while those found in the hand are referred to as Riche-Cannieu and Berrettini. Martin-Gruber anastomosis involves branching of the median nerve proximally to ulnar nerve distally. Marinacci anastomosis, the rarest of all the presentations, is often termed reverse Martin-Gruber, with the ulnar nerve stemming proximally to meet the median nerve distally in the forearm. Riche-Cannieu anastomosis occurs as an interconnection between the recurrent branch of the median nerve and the deep branch of the ulnar nerve in the hand. Berrettini anastomosis is the most frequently encountered of the anomalies and is described as a neural connection between common digital nerves of the ulnar and median nerves. Due to altered innervation patterns, musculoskeletal disorders of the forearm and hand may present with misleading symptoms. Additionally, existence of an anastomosis may require an alteration of surgical methods or be a source of iatrogenic injury. Consequently, knowledge of these anastomoses is crucial to clinical practice. Therefore, the objective of this review is to concisely present the most relevant information regarding median and ulnar anastomoses in the forearm and hand.