Changes in Distance Between the Flexor Pollicis Longus Tendon and Volar Locking Plate: An Ultrasonographic Study

Abstract

Flexor pollicis longus rupture is a major complication after volar locking plate fixation of distal radius fractures. Although the distance between the flexor pollicis longus tendon and the plate (plate-tendon distance) measured by ultrasonography is used to predict tendon rupture risk, the timing of the ultrasonography can affect the measurements. Therefore, this study aimed to analyze the chronological change of the plate-tendon distance between the tendon and plate. A total of 166 wrists underwent the plate-tendon distance measurement twice or more times within 15 months after surgery. Longitudinal ultrasonography scans with the wrist in a neutral position and the thumb flexed were used to measure the plate-tendon distance. The plate-tendon distances at 0-5 months, 5-10 months, and 10-15 months after surgery were compared. A multiple linear regression analysis was performed to evaluate the influence of the interval between surgery and examination, Soong grade, and plate type on the plate-tendon distance. The plate-tendon distance decreased as the interval between surgery and examination increased. The plate-tendon distance was an average of 2.0 ± 1.1 mm, 1.4 ± 0.9 mm, and 1.2 ± 0.9 mm at 0-5 months, 5-10 months, and 10-15 months after surgery, respectively. Significant differences were observed between 0-5 months and 5-10 months and between 5-10 months and 10-15 months after surgery. A multiple linear regression showed that significant predictors of the plate-tendon distance were the intervals between surgery and examination and Soong grade. The plate-tendon distance decreased as the time since surgery increased. When ultrasonography is used for the assessment of tendon rupture risk, it should be considered that the plate-tendon distance decreases as the interval between the surgery and examination increases. Prognosis IV.