Transthecal digital nerve block. An anatomical appraisal.

Injection studies using methylene blue and latex were used in 60 digits from 40 cadavers to study how anaesthetic fluid injected into the flexor tendon sheath might spread around the proximal part of the finger. The injected solution escaped from the flexor tendon sheath around the vincular vessels which are present near the base and head of the proximal phalanx. Outside the digital canal, the dye flowed smoothly through the perivascular loose areolar tissue and spread alongside the main digital vessels and nerves and their palmar and dorsal branches.