Transpedicular screw fixation of articular mass fracture-separation: results of an anatomical study and operative technique.

Articular mass fracture-separation accounts for 9% of the fractures of the lower cervical spine. Neurologic complications are frequent and are usually radicular in nature. Unreduced, these fractures may cause persistent neck pain. The treatment is usually surgical, fusing two or three vertebrae. In this article we present a new treatment modality using reduction and stabilization of the dislocated fragment with a transpedicular lag screw. Previous anatomic studies have shown that the pedicles of the lower cervical spine are wide enough to accept 4.0-mm screws. An anatomic study was performed showing that transpedicular screw fixation is safe when the following technique is used: entry point 3 mm beneath the facet joint on a vertical line in the middle of the articular mass. The drill is angled medially, depending on the preoperative measurement on the computed tomography scan (average 45 degrees). The drill aims toward the cranial third of the vertebral body as seen on lateral fluoroscopy. The tap-drilling method is used. After placement of 33 screws in cadaver pedicles of the cervical spine, 10 had minor breakout of the cortex of the pedicle (only small parts of the threads were penetrating the cortex); none showed major violation of the pedicle wall. The most common direction of minor pedicle violation was lateral. Transpedicular screw fixation has been successfully used in three patients.