Digital Nerve Block of the Thumb

Indications and Clinical Considerations

Digital nerve block is used primarily in 2 clinical situations: (1) to provide surgical anesthesia in the distribution of the digital nerves for laceration, tendon, and fracture repair; and (2) to provide postoperative pain relief after joint replacement or major surgical procedures on the hand. The technique can also be used to palliate the pain associated with traumatic neuropathy of the digital nerve of the thumb caused by overuse of scissors and pliers, entrapment neuropathies, or tumors of the digital nerve ( Figs. 101.1 and 101.2 ).

Electromyography helps distinguish other causes of hand numbness from neuropathy of the digital nerve. Plain radiographs are indicated for all patients with bowler’s thumb to rule out occult bony disease, such as bone spurs or cysts, which may be compressing the digital nerve. On the basis of the patient’s clinical presentation, additional testing may be indicated, including complete blood cell count, uric acid, sedimentation rate, and antinuclear antibody testing. Magnetic resonance imaging and ultrasound imaging of the hand can be done to rule out soft-tissue tumors such as ganglia that may be compressing the digital nerve ( Fig. 101.3 ). The injection technique described later serves as both a diagnostic and a therapeutic maneuver.

Clinically Relevant Anatomy

The common digital nerves arise from fibers of the median and ulnar nerves ( Fig. 101.4 ). The thumb also has contributions from superficial branches of the radial nerve. The common digital nerves pass along the metacarpal bones and divide as they reach the distal palm. The volar digital nerves supply the majority of sensory innervation to the fingers and run along the ventrolateral aspect of the finger beside the digital vein and artery. The smaller dorsal digital nerves contain fibers from the ulnar and radial nerves and supply the dorsum of the fingers as far as the proximal joints.