Danger zones for flexor tendons in volar plating of distal radius fractures.

PURPOSE: To define a danger zone for volar plates using magnetic resonance imaging by analyzing the position of the flexor tendons at risk around the watershed line.

METHODS: We analyzed 40 wrist magnetic resonance images. The location of the flexor pollicus longus (FPL) and index flexor digitorum profundus (FDPi) tendons was recorded at 3 and 6 mm proximal to the watershed line of the distal radius. We measured the distance between the volar margin of the distal radius and the FPL and FDPi tendons, and the coronal position of the tendons.

RESULTS: At a point 3 mm proximal to the watershed line, FPL and FDPi were located on average 2.6 and 2.2 mm anterior to the volar margin of the distal radius. This distance increased to 4.7 and 5.3 mm at a point 6 mm proximal to the watershed line. The FPL and FDPi were located at 57% and 42% of the total width of the distal radius from the sigmoid notch at 3 mm from the watershed, and at 66% and 46% at 6 mm from the watershed.

CONCLUSIONS: Surgeons should be aware of the close proximity of the flexor tendons to the volar cortex of the distal radius proximal to the watershed line and their radial to ulnar position. Three millimeters proximal to the watershed line, plate placement more than 2 mm anterior to the volar cortex or the use of plates thicker than 2 mm poses a high risk for directly contacting flexor tendons.

CLINICAL RELEVANCE: This article may prove to be helpful in avoiding flexor tendon injury during volar plate fixation.