Ultrasonographic evaluation of contact configuration between flexor pollicis longus tendon and the volar prominence of volar plate in patients with distal radius fracture

Introduction We classified the contact configuration between the volar prominence of volar locking plate (VLP) and flexor pollicis longus (FPL) tendon using ultrasound (US) into indentation contact and smooth contact, and investigated whether the contact configuration is associated with the flexor tendon attrition. Materials and methods Ninety-four patients who underwent VLP removal were included in this study. We assessed pain using visual analogue scale, grip strength, and Disabilities of the Arm, Shoulder and Hand score for clinical evaluations, radial inclination, palmar tilt, ulnar variance, and Soong classification for radiological evaluations, and contact configuration using US at 1 year after VLP fixation. After these evaluations, we removed the VLP with observation for the presence of fibrillation or wear of FPL tendon substance. Subsequently, we classified the patients into either of FPL attrition and FPL intact group. Results Twenty-eight patients had indentation contact configuration and 66 patients had smooth contact configuration. The kappa value for inter-observer reliability for the contact configuration was 0.78. Twelve patients were included in the FPL attrition group and 82 in the FPL intact group. There was no significant difference in clinical outcomes and Soong classification between the groups. However, palmar tilt of the flexor tendon attrition group was significantly lower than that of the flexor tendon intact group and the FPL attrition group showed significantly higher indentation contact configuration rate than the FPL intact group. FPL tendon attrition was diagnosed using the contact configuration on US with a sensitivity of 100% and specificity of 80%. Conclusion This study demonstrated that FPL tendon attrition was significantly associated with indentation contact on US with high sensitivity. Therefore, we recommend selective implant removal in patients with indentation contact configuration.