Abstract
Background Flexor tendon injury is a rare but serious complication of distal radius volar plating.
Purpose This study aims to determine whether the design of distal radius volar plates impacts
the amount of force exerted on the flexor digitorum profundus (FDP) and flexor pollicis
longus (FPL) tendons when the plates are placed proximal and distal to the watershed
line.
Methods Three commercially available plates were applied to 10 fresh, matched-pair upper
extremity specimens. Cyclical loading was applied to the tendons, and the force generated
between tendon and plate was measured. Linear mixed effect models were used to evaluate
differences in maximum and mean forces by plate position, plate design, and the interaction
between position and design.
Results Forces on the tendons differed significantly by position but not plate design. For
the FPL tendon, the average maximum force with a plate in Soong's grade 2 was 4.50
(95% confidence interval [CI]: 2.8–7.3) times higher than when the plate was in a
Soong's grade 0 placement, and 4.63 (95% CI: 2.82–7.61) times higher for the FDP tendon.
While not statistically significant, lower observed force values with thinner plates
when plates were placed distal to the watershed line suggest that that plate thickness
could also be a critical plate characteristic for distally placed plates.
Conclusion Despite differences in plate design, the main determinant of plate prominence and
therefore flexor tendon injury potential is placement in relation to the watershed
line.
Clinical Relevance This study may help to guide surgeon implant selection and volar plate design.
Keywords
distal radius fracture - distal radius volar plate - flexor tendon injury - tendon
rupture - watershed line
