Percutaneous fixation of the scaphoid through a dorsal approach: an anatomic study

Percutaneous surgical treatment of nondisplaced scaphoid fractures is becoming more common. Although the surgical anatomy at risk has been well described for the volar approach to the scaphoid, we have not found articles elucidating the dangers with a percutaneous dorsal approach. Additionally, direct placement of the screw is not possible with a percutaneous approach, and there is a risk of not seating the screw below the subchondral bone. The purpose of this study was to delineate the anatomy at risk using a dorsal percutaneous approach to the scaphoid and to determine the accuracy of using fluoroscopy to seat the screw flush with the subchondral surface.

Cannulated, headless screws were placed into the scaphoids of 12 fresh-frozen cadavers in standard percutaneous fashion through a dorsal approach. Fluoroscopy was used to seat the screw just below the subchondral surface. The wrists were then dissected and the distance from the guide wire to various anatomic structures was measured. The distance that the screw was protruding above or buried below the subchondral bone was also measured.

The distances from the guide wire to the posterior interosseous nerve, to extensor digitorum communis to the index, and to extensor indicis proprius were 2.2 mm, 2.2 mm, and 3.1 mm, respectively. These structures were most at risk. The screw was prominent (above the subchondral bone) in 2 of 12 specimens and flush with or buried in the remaining 10 specimens.

The results of this study show that there are anatomic structures at risk of injury with dorsal percutaneous placement of a headless screw into the scaphoid. Despite using live and static fluoroscopy views, we incorrectly placed the screw above the subchondral bone in 2 of the specimens. We support use of a limited incision when internally fixing a scaphoid from the dorsal approach.