Ultrasonographic evaluation of the distance between the flexor pollicis longus tendon and volar prominence of the plate as a function of volar plate positioning and pronator quadratus repair - A cadaver study.

Flexor tendon injury after volar plating of distal radius fractures is due to friction against the plate. To assess this risk, the distance between the flexor pollicis longus (FPL) and the volar prominence of the plate was measured with ultrasonography under various conditions: a standard plate fixed proximal or distal to the watershed line and a low-profile volar rim plate, with and without transection of the pronator quadratus (PQ). Distance from the FPL to the volar prominence of the plate decreased significantly when the PQ was cut and when a standard plate was placed distal to the watershed line, with the tendon often bulging over the plate. No statistical difference was measured between a volar rim plate and a standard plate distal to the watershed line. Our results confirm the importance of positioning the volar plate proximal to the watershed line and of repairing the PQ.