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BACKGROUND: Lesions of structures around the ventral side of the brainstem are located in the deep surface of the craniocervical junction, surrounded by important structures. The far lateral approach is the basic surgical method, but sex and lateral differences should be considered in the approach. OBJECTIVE: To analyze the morphological characteristics of the foramen magnum and occipital condyle by three-dimensional reconstruction measurements, thereby providing anatomical parameters for the far lateral approach to the skull base in clinical practice. METHODS: A total of 673 adult patients (448 males and 225 females) with head and neck CT scans were selected. The age ranged from 20 to 87. The length and width of the foramen magnum were measured. The area and index of the foramen magnum were then calculated by formulas. The length and width of the occipital condyle were measured, as well as the angle between the long and sagittal axis of the occipital condyle (O-S angle), the angle between the line connecting the midpoints of anterior and posterior foramen magnum and the line connecting the midpoint of anterior foramen magnum and the intersection of posterior occipital condyle and lateral foramen magnum (F-O angle), and the angle between the line connecting the midpoints of anterior and posterior foramen magnum and the line connecting the midpoint of anterior foramen magnum and the midpoint of the posterior wall of the hypoglossal canal (F-H angle). The sex and lateral differences of each index were analyzed. RESULTS AND CONCLUSION: There were statistical differences in foramen magnum indexes except between sexes (P > 0.05). The indexes of occipital condyle were significantly higher in males than in females (P < 0.05) except that the left occipital condyle width in males was lower than that in females (P > 0.05). The O-S angle in males was smaller than that in females, and there was a significant difference in the left O-S angle between sexes (P < 0.05). There was no statistical difference between right and left F-H angles. Significant differences were observed in occipital condyle length, occipital condyle width, O-S angle, and F-O angle (P < 0.05). These findings indicate that the parameters of the foramen magnum and occipital condyle were different in sex and on both sides. For the far lateral and transcondylar approaches, the right approach was relatively safe and exposed to a larger range. The length, width, and area of the foramen magnum, the length of the occipital condyle, and O-S angle in males were larger than those in females. Therefore, the sex difference should be considered in the far lateral approach. [ABSTRACT FROM AUTHOR]

BACKGROUND: Both rhesus monkeys and humans belong to primates, and their cervical vertebra structure, physiological function and living conditions are very similar to those of human beings. However, there are few studies on the finite element analysis of the whole cervical vertebra of rhesus monkeys. OBJECTIVE: To establish the C0-T1 finite element model of cervical vertebrae of adult rhesus monkeys and to make a comparative study between the finite element models of cervical vertebrae of adult rhesus monkeys and human cervical vertebrae in order to find out the difference. METHODS: A 7-year-old adult male rhesus monkey was selected and scanned by multi-slice spiral CT in the Imaging Department of the affiliated Hospital of Inner Mongolia Medical University in December 2019. The original CT data of cervical vertebrae were introduced into Mimics21.0 to establish a preliminary three-dimensional model, and the geometric structure of the model was optimized by Cero to get the simulation three-dimensional model of cervical vertebrae. The assembly model was imported into Hypermesh for tetrahedral gridding to divide the tissue grids of various segments, intervertebral discs and ligaments of cervical vertebrae. Then the finite element model of cervical vertebra was constructed by Abaqus&ANSYS, and the validity was verified by referring to the relevant finite element model literature. RESULTS AND CONCLUSION: The three-dimensional finite element model of cervical vertebra of rhesus monkey (including C0-T1 and six intervertebral discs and related ligaments) was successfully established, with a total of 536 215 elements and 461 915 nodes. The overall simulation of the model was high, and the fine structure was restored with high precision, resulting in a high biological simulation performance. Comparing the range of motion of this model with that of human cervical vertebra model, we found that the flexion and extension of this model were smaller than those of normal adults (P < 0.05), and left and right lateral bending of C2-3, C3-4 and C6-7 segments was smaller than the range of standard deviation as reported (P < 0.05). However, axial rotation showed no significant difference as compared with the value reported previously (P > 0.05). To conclude, there is a great difference in the exercise efficiency between the finite element models of rhesus monkey cervical vertebra and human cervical vertebra, which can provide a theoretical basis for the study of rhesus monkey cervical vertebra modeling. [ABSTRACT FROM AUTHOR]