Flexor pollicis longus tendon rupture by sandwiched underlying volar locking plate and distal radius

Flexor pollicis longus (FPL) tendon rupture is a major complication of volar locking plate fixation for distal radius fractures. The tendon rupture is usually caused by friction between the distal edge of the plate and the FPL tendon, and has been well detected recently with ultrasonography. Rarely, the volar locking plate itself entraps the FPL tendon, leading to its rupture. A 63-year-old man was consistently unable to flex his right thumb after previous surgery for a distal radius fracture at another hospital. Ultrasonography demonstrated loss of tendon gliding and unusual patterns of the FPL tendon. The tendon was sandwiched between the plate and the distal radius, and was penetrated by the distal locking screw, which was comparable to intraoperative findings of complete entrapment and rupture of the FPL tendon from the underlying plate. The tendon defects were repaired using a palmaris longus tendon graft after removing the screws and plate. Finally, he could flex his thumb actively with satisfaction. Unusual patterns of FPL tendon rupture buried under inadequate plate positioning must be recognized, as in this case. Ultrasonographic assessment is routinely recommended to visibly determine any FPL tendon damage after volar locking plate fixation for distal radius fractures.