CT evaluation of upper thoracic spine for surgical application of transarticular screw placement

Introduction Although pedicle screw fixation has been increasingly used in the upper thoracic spine in recent years, controversies exist about the safety and complications such as nerve or vascular intrusion associated with the technique. In this study, an alternative method of transarticular screw fixation was validated. Materials and methods Morphometric analysis was performed on computed tomography (CT) scans of the upper thoracic zygapophysial joints of C7, T1, T2 and T3 in 20 male and 20 female patients in the axial and sagittal planes. The degree of screw angulation was recorded in the sagittal and axial planes and the screw length was measured at the spinal level from C7 to T3. Results The smallest medial–lateral diameter and anterior–posterior diameter of IAP was found at T3 in the female patients and C7 in the male patients. The screw trajectory length ranged from 14.9 to 20.5 mm in all patients. All the above measurements were significantly different between male and female patients at all levels ( P < 0.05). The mean value of screw trajectory angle was 19.3°–20.1° in the axial plane and 44.3°–45.7° in the sagittal plane. There was no statistically significant difference ( P > 0.05) between male and female patients in the axial and sagittal angles. Conclusion The morphometric data of C7–T3 zygapophysial joints indicate the suitable screw diameter and screw length for this technique. Transarticular screw fixation proved to be a potentially safe alternative to pedicle screw fixation in this region.