Morphometric Characteristics of C1-C2 Vertebrae to Perform Anterior Transarticular Crossing Screw Fixation

In unique clinical situations where C1-C2 posterior fixation is not available or has previously failed, an anterior transarticular screw (ATAS) may be a viable alternative. However, there are no previous reports that investigate possible screw angles, screw entry points, and screw length based on computed tomography (CT) multiplanar reconstruction images in Turkish patients. The aim of this study was to determine the morphometric characteristics C1-C2 vertebrae in order to perform anterior transarticular crossing screw fixation.

Patients who underwent a complete CT scan of the cervical spine for causes other than an investigation of cervical spine malformation or congenital anomaly between the years 2013 and 2015 were included in this study. The anterior transarticular C1-C2 screw angles, screw entry point, and screw length were measured on coronal and sagittal CT multiplanar reconstruction images.

Twenty-five male and 14 female patients were included in the study. The mean maximum screw angle for ATAS was found to be 41.18°±4.49°. The minimum and maximum screw lengths were 27.46±3.39 mm and 28.46±3.60 mm, respectively.

Preoperatively, performing a calculation of the possible screw angles, screw entry point, and screw length based on CT multiplanar reconstruction images for ATAS is a safe and applicable method. In cases in which ATAS fixation across the atlantoaxial joint procedure should be performed without performing a measurement, a screw angle not more than 41.18°±4.49° on the coronal plane does not damage the vertebral artery. Furthermore, using screws shorter than 28.46±3.60 mm doesn"t purchase the atlantoaxial joint.