Written by Megan Hilbert
Spoon Feed
Having an array of techniques for digital nerve blocks in your back pocket can only serve to improve your patient care. Let’s review some approaches.
Why does this matter?
Injuries to the extremities and particularly to the digits represent upwards of 1 million ED visits per year. It is important to be able to adjust your method of anesthesia according to each presentation etiology (dislocation, fracture, laceration repair, etc) and patient tolerance.
This little piggy went to market, this little piggy went numb
A PubMed search was completed, and the authors reviewed three approaches. Table below adapted from the paper to include all relevant information. Associated images to demonstrate nerve block approach.
As always when completing nerve blocks, make sure to aspirate as you advance and prior to injection to confirm you are not intravascular and prevent potential LAST.
| Dorsal Web Space | Transthecal | Volar Subcutaneous | |
| Also known as… | Traditional Finger Block | Flexor Tendon Sheath Block | Tumescent Block |
| Use for | Fingers or Toes | Fingers only | Fingers only |
| Success rate (%) | 60-92 | 94-100 | 89 |
| Volume of anesthetic (assuming 1% lidocaine) | 1-3mL per aspect (2-6mL total) | 1.5-3mL | 2-3mL |
| Onset of action (min) | 3.9-4.5 | 2.8-7.2 | 1.6-3.3 |
| Advantages | Enhanced anesthesia to dorsal digit and nail bed | Single injection only, reduced risk of neuromuscular injury or compression | Single injection only, easier to perform, patient preferred (less procedure related pain) |
| Disadvantages | Two injections, increased rate of incomplete anesthesia, Higher potential for direct nerve injury | Potential increased risk of post-procedural pain 2/2 tendon sheath puncture/injection | Reduced dorsal anesthesia compared to other blocks |
Dorsal Web Space Block Technique:
- Insert the needle into dorsal aspect of web space distal to MCP joint at the level of the phalangeal-palmar crease on one aspect of digit
- Advance needle around the bone toward the palmar aspect of finger without puncturing palmar skin. Aspirate then inject anesthetic while slowly withdrawing the needle.
- Repeat the same on the other side of the finger in the contralateral web space.
- Consider potential dorsal injection for nail bed injuries (three-sided ring block) – before removing the needle from the skin redirect across dorsal aspect of the finger from first injection site and inject over the dorsum of the finger (additional 1-2mL)
Transthecal Block Technique:
- Insert needle through skin at 90 degree angle at proximal digital crease while staying midline to avoid neurovascular structures.
- Advance until needle strikes bone of proximal phalanx then withdraw 2-3mm.
- Direct needle 45 degrees distally along long axis of the finger and begin injection while palpating the tendon sheath (soft tissue of the patient’s middle phalanx). Sheath should become full and finger may flex slightly.
Volar Subcutaneous Block Technique:
- Identify proximal digital crease, insert needle at this site aiming 45 degrees distally along long axis of the digit.
- Inject 2-3mL of local anesthetic in subcutaneous tissues to achieve distension of skin over palmar aspect. If you only achieve skin wheal, the needle is too superficial and needs to be advanced.
Source
Digital Nerve Blocks: A Comprehensive Review of Techniques. J Emerg Med. 2022 Oct 10;S0736-4679(22)00428-0. doi: 10.1016/j.jemermed.2022.07.002. Online ahead of print.
