The flexor synovial sheath anatomy of the little finger: a macroscopic study.

Abstract

Anatomy texts describe the flexor synovial sheath of the little finger as extending proximally into the palm to join with the ulnar bursa in 80% of cases. Based on this, one would expect frequent extension of little finger flexor synovial sheath infections into the forearm. Methylene blue injection followed by open tenogram was used to define the anatomy of the flexor synovial sheath of the little finger in 60 cadaver hands. In 27 hands, the flexor synovial sheath extended proximally from the bony profundus tendon insertion to terminate at the palmar aponeurosis pulley. A stricture of varying length separated the flexor synovial sheath from the more proximal ulnar bursa. In 19 hands, the flexor synovial sheath was continuous with the ulnar bursa, conforming to the conventional textbook description. In 14 hands, the flexor synovial sheath stopped at the proximal border of the A1 pulley. An inconsistent defect from 1 to 10 mm was noted. The clinical implications of these findings suggest that many little finger flexor synovial sheath infections, when caught early and after careful physical examination, need only be managed by drainage at the distal palmar level.