Biomechanical Comparison of Two Atlantoaxial Arthrodeses in a Cadaveric Spine Model: Transarticular Screw Fixation Versus Screw and Rod Fixation

The causes of atlantoaxial instability include trauma, tumor, congenital malformation, or rheumatoid arthritis. Commonly available fixation techniques to stabilize the atlantoaxial complex are several posterior wiring procedures (Brooks fusion, Gallie fusion), transarticular screw procedure (Magerl technique), either alone or in combination. Wiring procedures are obviously easier to accomplish however these do not provide sufficient immobilization across the atlantoaxial complex^1,3,4. On the other hand, although transarticular screw fixation (TSF) affords a much stiffer atlantoaxial arthrodesis than posterior wiring procedures. However, TSF has some drawbacks; for example the injury of vertebral artery. Furthermore, body habitus (obesity or thoracic kyphosis) may prevent from achieving the low angle needed for correct placement of screws between C1 and C2. Recently, a new technique of screw and rod fixation (SRF) that minimizes the risk of injury to the vertebral artery and allows intraoperative reduction has been reported^2,6. The purpose of this study was to compare the biomechanical stability imparted to the C1 and C2 vertebrae by either TSF or SRF technique in a cadaver model.