Study of superficial variations of ulnar nerve beyond the flexor retinaculum: a comprehensive review for surgical practice

Purpose: The ulnar nerve in the palm exhibits significant anatomical variations, including branching patterns and interconnections. Understanding these variations is crucial for the management of neuropathies. This study aimed to analyze the branching of the superficial branch of the ulnar nerve, the presence of communications between it and the median nerve, and the morphometric characteristics of these connections in cadaveric specimens and clinical cases. Methods: Fifty hands were dissected to examine the different patterns, morphometric variations between the ulnar and median nerves. Variations in Berrettini’s anastomosis were classified according to established criteria. Clinical cases related to surgical complications, nerve injuries related to these anatomical variations were also evaluated and correlated. Results: In the wrist, the branching pattern of the ulnar nerve showed bifurcation in 90% and trifurcation in 10% of specimens. Communicating branches were observed, between the superficial branch of ulnar nerve and the median nerve, and showed variations in trunk length, angle, and distance of origin. Berrettini’s anastomosis (Type I and Type III) was identified in 36% of specimens. Double communications and fiber networking between nerves were documented. Patient cases of unexpected claw hand, iatrogenic injuries and altered sensory nerve choice of transfer were correlated to these variations. Conclusion: The study stresses the irregularity in the branching patterns of the ulnar nerve and the interconnections between the ulnar and median nerves, providing analytical insights into their developmental and clinical inferences. These findings highlight the value of identifying anatomical variations to reduce iatrogenic injuries and improve diagnostic and surgical results.