Dorsal arterial supply to thumb showing ulnar dorsal collateral artery (1) and its anastomosis with ulnar palmar digital artery at neck of first phalanx (2) and with arcade at proximal nail fold (3). Topographic position of essential structures: distance between dorsal arcade of proximal nail fold and cuticle of nail is 0.7 cm, distance between palmar anastomosis and cuticle of nail is 2.3 cm, distance between median axis of thumb and ulnar dorsal collateral artery (1) at level of neck of first phalanx is 1 cm, and distance between median axis of thumb and ulnar dorsal collateral nerve (4) at level of head of first metacarpal bone is 1.4 cm.