Comparison of transthecal and subcutaneous single-injection digital block techniques in cadaver hands.

A controlled, randomized single-blinded study was performed on the thumbs and little fingers of 20 cadaver hands. The digits were randomly divided into 2 groups. In the transthecal group, 2 mL of 0.5% methylene blue was injected into the tendon sheath at the A1 pulley. In the subcutaneous group, the same amount of dye was injected into the subcutaneous tissue superficial to the A1 pulley. The injections were performed by 2 investigators. They exchanged specimens and performed dissections on the injected digits without knowledge of which technique had been used. The distributions of dye along the digit and the color intensity of the dye on the digital nerves were studied. There was no significant difference (p > .05) between results for the 2 techniques. It was expected that both techniques would result in similar anesthetic distribution in the clinical setting. In the transthecal group, intra-articular staining of the metacarpophalangeal joint was noted in 3 little fingers and 1 thumb. This complication did not occur in the subcutaneous group. This difference was significant (p < .05).