RESUMO
Objective To observe the arrangement and distribution of the fascicular groups in the ulnar nerve trunk to the intrinsic muscles so as to provide anatomical evidence for selective repair in the clinic.Methods 12 cadaveric upper extremities recently embalmed with formalin were obtained. The ulnar nerve and its branches were exposed. Microanatomy and longitudinal contradissection of each functional fascicular group were performed by tracing their terminal branches, and the arrangement and distribution were observed and recorded. The fascicular groups to the intrinsic muscles of hand in the nerve trunk were observed to see how they crossed and mixed with other fascicular groups. The diameter of the nerve trunk and the fascicles to the intrinsic muscles were measured, and the area and the distribution range of the fascicles calculated. Results The shape and the diameter of the ulnar nerve trunk varied at different positions. The fibers of functional fascicular groups had the definite differentiation at distal while interfused and diffused at proximal. The fascicular groups to the intrinsic muscles of hand were the largest and their fibers relatively concentrated (the distribution range occupied 40% ～ 80% of the ulnar nerve), and had the definite localization at the forearm and distal to the 3/8 segment of upper arm. Conclusion Since the fascicles to the intrinsic muscles of the hand are the most important in the ulnar nerve, selective repair by using epineural and perineural techniques at the forearm and upper arm will reduce the loss of nerve fibers and will contribute to the functional recovery.