Ulnar Nerve Block for Procedural Anesthesia - Wrist Versus Palm

Ulnar nerve blockade is necessary for sensory anesthesia and analgesia in the hand during minor procedures. The course of the ulnar nerve in the forearm, wrist, and hand is predictable and has low variability. However even with known anatomic location and landmarks, ulnar nerve blocks at the wrist frequently are inadequate for procedural anesthesia. The antebrachial fascia at the wrist acts as a barrier to local infiltration. Since the fascia can not be visualized or palpated, it is commonly not penetrated, resulting in an inadequate block. Furthermore at the level of the wrist the ulnar artery lies in close proximity to the nerve and there is potential for arterial puncture while attempting injection for volar wrist block. The palmar ulnar nerve block is an injection distal to the hook of the hamate in the thenar eminence which avoids the ulnar artery and antebrachial fascia. This block has been used successfully for many years in clinical practice but has not been assessed or compared in a research study. The purpose of this study is to assess the validity of using a palmar ulnar nerve block for procedures in the hand as compared to the standard volar wrist ulnar nerve block.