Alternative for carpal tunnel injection: palmar injection site (Rankin's zone)

This study investigates an alternative approach for steroid injection into the carpal canal through a palmar site and its exposure of vital wrist structures to potential injury. The Rankin's zone entry site is more distally located than conventional sites. This cadaveric study investigated 28 wrists from 26 cadavers. Red latex dye was injected as a localizing aid. Layered dissections were performed to localize the needle tip with respect to vital wrist structures. Calipers measured the distance from the needle to nerves. Twenty-three of the 28 injections using this approach demonstrated dye solely within the carpal tunnel. One median nerve was punctured. The mean distance from the median nerve was 5.76 ± 2.9 mm and 18.27 ± 5.27 mm from the palmar cutaneous branch. This study suggests that the Rankin's zone approach might be utilized with diminished frequency of neural puncture.