Digital Anesthesia for Interdigital Web Space
For anesthetizing the interdigital web space in fingers, use a subcutaneous single-injection digital block with lidocaine 1% (with or without epinephrine) injected into the volar subcutaneous space at the proximal digit using a tumescent technique, which provides complete anesthesia to both dorsal and volar aspects of the digit with a single injection. 1
Recommended Technique: Tumescent Single-Injection Approach
Inject 1% lidocaine into the volar subcutaneous space at the proximal digit to create a firm, turgid feel to the tissue (the "tumescent state"), which has demonstrated 100% success rate in achieving complete digital anesthesia in 123 consecutive patients 1
Volume should be based on digit size: typically 3-4 mL in adults, 1 mL in children 2
This single injection provides anesthesia to both palmar and dorsal digital nerves, eliminating the need for multiple injection sites 1
Epinephrine Use: Safe and Beneficial
Epinephrine-containing local anesthetics are safe for digital blocks, contrary to traditional teaching—a comprehensive literature review of 50 cases of digital gangrene found no cases associated with commercial lidocaine-epinephrine mixtures 3
Adding epinephrine provides significant advantages: creates a bloodless field without tourniquet, reduces need for large anesthetic volumes, and provides longer pain control 3, 4
Proper patient selection is essential: avoid in patients with thrombotic conditions, vasospastic disorders, or uncontrolled hypertension 3
Alternative Technique: Flexor Tendon Sheath Block
The flexor tendon sheath approach involves inserting the needle on the palmar aspect of the metacarpophalangeal joint into the digital flexor tendon sheath, then withdrawing slightly to inject within the sheath (not the tendon) 2
This technique used successfully in 350 cases with volumes of 3-4 mL in adults using either 2% lidocaine or 0.5% bupivacaine without epinephrine 2
Important limitation: this technique does NOT anesthetize the dorsal digital nerves, making it less suitable for procedures involving the interdigital web space 2
Pain Reduction During Injection
Apply topical anesthetic or freezing spray prior to needle insertion to reduce injection pain, particularly for palmar injections 2
For pediatric patients or those requiring IV access, topical lidocaine (LMX4) can provide anesthesia in approximately 30 minutes, though this is less applicable for immediate digital procedures 5
Key Advantages Over Traditional Ring Blocks
Single injection site reduces patient discomfort compared to multiple injections required for traditional ring or interdigital blocks 2, 1
Lower risk of vascular and neurological complications compared to ring blocks, which carry significant risk of these complications 2
No tourniquet required when epinephrine is used, reducing procedural complexity and patient discomfort 3, 4
Critical Pitfalls to Avoid
Never inject directly into the tendon—withdraw the needle slightly after entering the flexor tendon sheath to ensure injection into the sheath space, not the tendon itself 2
Avoid excessive volumes that could cause compartment syndrome or vascular compromise—stick to recommended volumes based on digit size 2, 1
Do not use outdated compounds (cocaine, procaine) or non-standardized mixing methods for epinephrine, which were associated with historical cases of digital necrosis 3
Avoid hot soaks postoperatively and ensure proper infection control, as these factors contributed to historical cases of digital complications 3