Anatomical Study on the Safety of Anterior Cervical Craniovertebral Fusion with Clival Screw Placement in Children Aged 1–6 Years

OBJECTIVE: This study aimed to investigate the safety of clival screw placement in children aged 1–6 years. METHODS: The cranial computed tomography data of 92 children aged 1–6 years were divided into three groups, according to age, for three-dimensional reconstruction. Three clival screw placement points were defined: (1) median point A at the middle and upper third of the tripartite distance from the spheno-occipital synchondrosis to the base of the skull; (2, 3) critical points B and C on the horizontal line with point A, where the screw placement passage was parallel to the sagittal plane. Parameters such as the passage length and angle were measured for horizontal, vertical facial, and extreme screw placement. RESULTS: The length parameters of the clival screw placement increased with age, and the screw passage length was the shortest for the vertical facial type in each age group. There were significant differences in all three groups between the length of screw placement in the vertical bone surface, the length of screw placement in the horizontal direction, and the length of screw placement on the limit at points A, B, and C (P < 0.05); the length of screw placement on the vertical bone surface was the shortest. There was no significant difference between the horizontal screw length at point A and the extreme screw length (P > 0.05). The difference between the horizontal screw length and the extreme screw length in the groups aged 1–2 years and 5–6 years was statistically significant (P < 0.05), and the horizontal screw length was longer. CONCLUSION: The cranial slope of children aged 1–6 years has the morphological basis for the placement of 3.5 mm screws, and each placement point has a safe angle range for screw placement.