This article was originally published here

J Orthop Res. December 4, 2021. doi: 10.1002/jor.25224. Online before printing.

This study aimed to quantify the extraoccipital carina (EOP) and the trabecular volume bone mineral density (vBMD) of the upper cervical spine. A retrospective study was conducted on patients who underwent non-contrast-enhanced computed tomography of the cervical spine, including the occipital bone, from 2007 to 2020. The measurement of trabecular vBMD was performed in the occipital midline area, the area of ​​interest extending 4.5 mm above and below the center of the EOP, and the C1 lateral mass and C2 vertebral body using asynchronous quantitative computed tomography. 86 patients (female, 37.2%) were included in the analysis. The patient population was 81.4% white, and the mean ± SD age was 62.3 ± 13.1 years. The total bone thickness at the EOP is 16.7 ± 3.4 mm, and the ratio of trabecular bone to total bone thickness is 0.44. EOP's trabecular vBMD (mean ± SD) was significantly higher than C1 and C2 (EOP = 612.3 ± 145.8 mg/cm3, C1 average = 290.3 ± 66.5 mg/cm3, C2 = 305.8 ± 78.8 mg/cm3; p < 0.0. ). A significant and strong correlation was observed between the trabecular vBMD of C1 and C2 (r = 0.744; p <0.001), but EOP and C1 (r = 0.295; p = 0.008) and C2 (r = 0.413; p < 0.001) only has a low correlation between 0.001). In individuals >65 years of age, cervical vBMD is significantly reduced, but it is still high at EOP. Clinical significance: The trabecular vBMD at the EOP is significantly higher than that of the upper cervical spine, and it is still very high in the elderly. Together with the morphological information about the occipital bone, these results may help determine the occipital-cervical fixation when single or double cortical screws are placed at the EOP.