環軸関節固定術の３Ｄ‐ＣＴによる術後評価 Ｔｒａｎｓａｒｔｉｃｕｌａｒ ｓｃｒｅｗの安全性に関する検討

Abstract

In recent years, atlanto-axial transarticular screw fixation performed as described by Magerl for atlanto-axial subluxation has been popular because of its excellent biomechanical stability. However, there is a risk of vertebral artery injury with placement of transarticular screws.Twelve patients (age range: 18 to 72 years, mean: 60 years) underwent surgery as described by Magerl & Brooks for reducible atlanto-axial subluxation. Four were men and eight were women. Computed tomography (CT) was performed after surgery. We evaluated the position of the transarticular screw by means of sagittal reconstruction CT images. There was no screw that deviated from the C2 isthmus and had been placed incorrectly in the spinal canal. One screw (4.2%) passed through the C2 isthmus and bordered on the foramen of the transverse process. The screw angle measured between a line through the axis of the screw and the mid-sagittal line was -3-13 degrees. The screw length projected out of the C1 lateral mass was -3.6-10.8mm. There was no complication such as vertebral artery injury during screw insertion.Because of translational or rotational atlanto-axial subluxation, presurgical computed tomographic scans with sagittal reconstruction may provide information necessary to perform transarticular screw fixation safely.