Chapter 80F: Wrist Block

INTRODUCTION

The wrist block involves anesthesia of the median, ulnar, and radial nerves, including the dorsal sensory branch of the ulnar nerve. The wrist block is simple to perform, essentially devoid of systemic complications, and highly effective for a variety of procedures on the hand and fingers. Wrist blocks can be used in the office or operating room setting. As such, skill in performing a wrist block should be in the armamentarium of every practitioner.^1-9 A study comparing intra-articular and portal infiltration versus wrist block for analgesia after arthroscopy of the wrist has shown that wrist block provides better and more reliable analgesia in patients undergoing arthroscopy of the wrist without exposing patients to the risk of chondrotoxicity.¹⁰

INDICATIONS & CONTRAINDICATIONS

A wrist block is most commonly used for hand and finger surgery.^11,12 The most common hand surgery in the United States is carpal tunnel release. Sir James Paget described carpal tunnel syndrome in 1853.^1,13 Although Sir James Learmonth reported release of the carpal tunnel at the wrist in 1933, it was not until the 1950s that the surgery became popular through the efforts of George Phalen.^14,15,16 Because of the ease of performing a wrist block, wrist blocks are used in a variety of settings including the emergency room, outpatient surgery centers, and office-based anesthesia practices. Hand surgeons rely on the wrist block to perform minor procedures in their offices. A wrist block can be used in a patient with a full stomach requiring emergency surgery, thereby obviating the need for general anesthesia and reducing the risk of aspiration.

Although only there are only a few contraindication to wrist blocks, local infection at the site of needle insertion and allergy to local anesthetic are the most cited. Patients are usually able to tolerate a tourniquet on the arm without anesthesia for 20 minutes; a wrist tourniquet can be tolerated for about 120 minutes.

FUNCTIONAL ANATOMY OF WRIST BLOCK

Innervation of the hand is shared by the ulnar, median, and radial nerves (Figure 80F–1). The ulnar nerve innervates more intrinsic muscles than the median nerve, and supplies digital branches to the skin of the medial one and a half digits (Figure 80F–2). A corresponding area of the palm is innervated by palmar branches that arise from the ulnar nerve in the forearm. The deep branch of the ulnar nerve accompanies the deep palmar arch and supplies innervation to the three hypothenar muscles, the medial two lumbrical muscles, all the interossei, and the adductor pollicis. The ulnar nerve also innervates the palmaris brevis muscle.