Anatomical analysis of the occipital bone in patients with basilar invagination: a computed tomography-based study

BACKGROUND CONTEXT: The occipital bone is often involved in the surgical treatment of basilar invagination (BI). However, the anatomy of the occipital bone associated with BI patients has yet to be investigated. PURPOSE: To present a morphological map of the occipital bone in BI patients and help guide screw placement for occipitocervical fusion. STUDY DESIGN: A retrospective case-control study. METHODS: Radiological measurements of the occipital bone were performed on computed tomography images based on a matrix of 99 points centered around the external occipital protuberance (EOP) in a cohort of 50 BI patients and 50 cases with no head and cervical disease. The comparison between the BI group and the control group was assessed using Student t analysis and p<.05 was considered statistically significant. RESULTS: All thicknesses measured from points of the matrix in the BI group were thinner than those in the control group (p<.05). The maximum thicknesses in both groups were located at the center of the EOP, which were 15.11 +/- 2.84 mm in the BI group and 17.56 +/- 3.03 mm in the control group, respectively. Additionally, thickness decreased with the distance away from the center of EOP. CONCLUSIONS: The occipital bone in BI patients is thinner than that in the general population. A limited safe zone in BI patients is available for surgeons to place screws, which may need to be fully evaluated before operation. (C) 2020 Elsevier Inc. All rights reserved.