CT analysis of anatomical variation and injury affecting posterior pedicle screw fixation for unstable Hangman fractures.

The aim of this study was to evaluate the anatomical variations and injuries in patients with unstable Hangman fractures that affected the posterior pedicle screw placement of C2 to C3 and retrospectively review our experience with management of these fractures. Clinical data were reviewed in 72 patients with unstable Hangman fractures, especially using 3-dimensional computed tomography (3D-CT) scan to identify the presence of anatomical variations or injuries and analyzing the treatment strategies we used. Twenty-two patients (22/72, 30.6%) with 39 (C2 or C3) risk factors were not fit for safe C2 to C3 pedicle screw placement, due to factors such as small pedicle size of C2 or C3, high-riding vertebral arteries, fractured fragments encased into vertebral canal, or transverse process foramen of C2, sclerotic pedicles and pedicle fractures of C3. One or more than one of these risk factors could pose more risks of arterial or neural structures damages to pedicle screw fixation for unstable Hangman fractures. Individualized treatment plans were made to minimize the risks of surgery for the 22 patients. There is a high incidence of anatomical variations and injuries in the C2 to C3 region in patients with unstable Hangman fractures that affect the pedicle screw placement. Preoperative evaluation of these conditions using 3D-CT scans is of paramount importance to avoid and decrease operative complications and to choose appropriate surgical techniques.