Ultrasonographic movement of the flexor pollicis longus tendon before and after removal of a volar plate for the distal radius fracture

Introduction: The purpose of this study was to compare the movement of the flexor pollicis longus (FPL) tendon on the distal radius during wrist and finger motions before and after removal of a volar plate in patients with distal radius fractures using transverse ultrasound and to evaluate the kinematic effects on the FPL by the removal. Methods: Twenty-five patients with distal radius fracture were evaluated quantitatively by transverse ultrasound using coordinates for the movement of the FPL on the distal radius during wrist and finger motions before and after the plate removal. Results: At all wrist positions, during finger motion, the FPL moved significantly more palmarly away from the radius after plate removal compared to before. However, the FPL was still situated more dorsoulnarly compared with unaffected side. Moreover, the FPL moved significantly most dorsally both before and after removal at the wrist dorsal flexion position with finger flexion. Conclusions: These findings suggested that any adhesion between the FPL and the pronator quadratus (PQ) muscle was released by removing the plate and that the FPL would approach original tendon movement. Additionally, it is speculated that any remaining atrophy and fibrosis of the PQ may be the reason for more dorsoulnar location of the FPL in the affected side compared with the unaffected one. This ultrasound evaluation may be useful in further understanding the FPL kinematics on the distal radius, and in appropriate treatment of the distal radius fracture with plate fixation for preventing FPL rupture.