LKnative - Ulnar nerve block 
Ulnar nerve innervation (yellow), median nerve innervation (orange), radial nerve innervation (purple). V = volar, D = dorsal
4 – Anatomy: Bony ulnar nerve innervation of the hand
The ulnar nerve innervates the volar side of the of medial 1 1/2 digits, and it innervates the dorsal side of the medial 2 1/2 digits