The difference of subcutaneous digital nerve block method efficacy according to injection location.

Introduction: Finger injuries are commonly attended to in the emergency department, and digital nerve block is a frequently performed procedure for such injuries. This study compared the efficacy levels of the subcutaneous method according to the different injection sites.

Method: This was a simulation study for medical students who rendered medical service at the emergency department. One group performed subcutaneous injection of lidocaine at the volar side of the metacarpophalangeal (MCP) joint, while another group injected at the volar side of the proximal interphalangeal (PIP) joint. The time to anesthesia was measured at 30-s intervals. Pain at the injection site was measured using the numeric rating scale (NRS), while the length from the fingertip to the injection site and the circumference of the injection site were measured.

Results: A total of 82 participants were included, with 41 under the MCP joint group and the rest under the PIP joint group. The mean length from the fingertip to the needling point was 3.62 ± 0.63 cm in the PIP joint group and 5.90 ± 0.65 cm in the MCP joint group, while the mean circumference of the needling point was 4.93 ± 0.51 and 5.61 ± 0.58 cm, and the mean time to anesthesia was 2.55 ± 1.11 and 3.79 ± 1.28 min (p-value < 0.001), respectively. The median value of NRS was 4 in both groups (p-value = 0.921). Length was correlated with the time to anesthesia (p-value = 0.018).

Conclusion: Injection into the PIP joint showed the same anesthetic effect as injection into the MCP joint, but this effect occurred faster in the former.