Locking finger due to a partial laceration of the flexor digitorum superficialis tendon: a case report.

A 39-year-old woman sustained a small wound on the palm of her right hand, which quickly healed naturally; however, a month later pain and limited range of motion were noted in her right finger. Surgery revealed the radial half of the flexor digitorum superficialis (FDS) tendon was ruptured and formed a flap, which hooked at the entrance of the A1 pulley. The proximal stump was sutured to the remaining ulnar (normal) side of the FDS tendon. Locking occurs between the tendon flap and the tendon sheath; therefore, when there is no fibrous tendon sheath near the partially ruptured tendon, locking will not occur.