The Security Analysis of Transpedicular Screw Fixation in the Lower Cervical Spine and a Case Report

Study Design. This study evaluated the anatomical parameters of the lower cervical spine by imaging methods and reported a case. Objective. To explain low neurovascular injury rate and provide some suggestions in cervical transpedicular screw fixation (CTSF). Summary of Background Data. Because of anatomical complexity and possible severe complications, application of CTSF was limited. However, recent studies have indicated that although cervical pedicular screw perforations may happen, severe complications seldom occur. Methods. In 20 patients, several anatomical parameters were obtained on computed tomographic angiography (CTA) images of C3-C6, including the inner diameter of vertebral artery (d), the maximal width (A) and height (B) of the transverse foramen, the shortest distance between vertebral artery and cervical pedicle (h), and the angle between the longitudinal axis of pedicle and the hypothetical screw that just touches the vertebral artery (largest safe angle, LSA). Another 35 patients were chosen to measure the shortest distance between cervical pedicle and cervical spinal cord (H) and the angle between the longitudinal axis of pedicle and the hypothetical screw that just touches the cervical spinal cord (smallest angle, SA) on magnetic resonance imaging (MRI) of C4-C7. Results. Between the left and the right sides, there was no statistically significant difference for d, A, B, h, and LSA at C3-C6 or H and SA at C4-C7. d, h, and H were, respectively, 3.97 +/- 0.65 mm, 0.89 +/- 0.44 mm, and 6.56 +/- 2.10 mm, and there was no statistically significant difference among C3-C6 for d and h or among C4-C7 for H. LSA at C6 was larger than that at C3, C4, and C5; it increased from C5 to C7. Conclusion. There was an "escaping space" for the vertebral artery and spinal cord. CTSF in the superior part of pedicle was relatively safer from accidental perforation of the vertebral artery than CTSF in the inferior part, and in C6 and C7, CTSF was safer from this injury than in C3, C4, and C5.