The torg ratio of C3–C7 in African Americans and European Americans: A skeletal study

The ratio between the sagittal diameter of the spinal canal and the sagittal diameter of the vertebral body, known as the “Torg ratio”, is often used to test for spinal canal narrowing. Here, we investigate this ratio in a large population, consisting of two ethnicities, both sexes and three age groups. Measurements were taken on the dry cervical verterbrae (C3–C7) of 277 individuals using a digital apparatus allowing for the recording of 3D coordinates of a set of landmarks on the vertebral body. Vertebral body and vertebral foramen lengths were compared across the different subgroups. Vertebral body and vertebral foramen lengths differ significantly between males and females and between African Americans and European Americans. With age, the vertebral body length increases while the foramen length does not undergo significant changes. These anatomical differences are reflected in differences in the Torg ratio calculated for the different subgroups. In conclusion, our findings suggest that a hard cutoff on the Torg ratio used to define a pathological narrowing of the cervical spine should be adapted to the population the patients come from. Clin. Anat. 32: 84-89, 2019.