The forearm squeeze test to identify a congenitally nonfunctioning flexor pollicis longus tendon

Abstract

A 9-year-old boy had limited flexion of the left thumb interphalangeal joint and absence of the interphalangeal joint crease. Magnetic resonance imaging suggested an absent flexor pollicis longus (FPL) tendon. However, intraoperative findings revealed an abnormal insertion site for the FPL tendon, which had 2 branches: a minor branch to the transverse carpal ligament and a major nonfunctioning far laterally located branch to the distal phalanx with bands to the extensor pollicis longus. Rerouting of the fourth flexor digitorum superficialis tendon with formation of a new pathway provided a noteworthy improvement in pinch at 2 years of follow-up.