This study compared the radiological feasibility and safety of three different atlas (C1) lateral mass screw trajectory (LMST) designs. The three C1 LMSTs, extroversion trajectory (LMST 1), vertical trajectory (LMST 2), and introversion trajectory (LMST 3), were designed based on the inclination angle in the axial plane. The related measurements were made on a workstation using the multiplanar reconstruction technique and cervical spine computed tomography data of 50 patients. The following parameters were included: the sagittal cephalad angle (∠A), the abduction angle α of LMST 1, the adduction angle β of LMST 3, the distance from the entry point to the midline (D), trajectory length (L), trajectory width (W), trajectory height (h), and height of the C1 posterior arch at the screw entry point (H). ∠α: 25 ± 6°; ∠β: 24 ± 5°; ∠A: 15 ± 10°. From LMST 1 to LMST 3, the corresponding values demonstrated the following trends: H gradually decreased from H1 to H3; D gradually increased from D1 to D3; L1 was the longest, significantly longer than L3, while L2 was the shortest; W3 was significantly wider than W2; h2 was significantly higher than h1. Additionally, the entry point in LMST 3 basically crossed the vertebral artery groove. Each of the three trajectories demonstrated advantages and disadvantages. Understanding these anatomical characteristics and parameters may assist surgeons in making more informed, anatomy-driven trajectory selections for C1 lateral mass screw placement.
Ding et al. (Wed,) studied this question.