Differences in Cross-Sectional Intervertebral Foraminal Area From C3 to C7.

Abstract

Anatomical comparative study. Few studies have evaluated foraminal areas in the cervical spine without degenerative changes. The purpose of this study was to determine and compare the mean cross-sectional foraminal areas between the C3/4, C4/5, C5/6, and C6/7 levels while also analyzing specimens for differences between sexes and races. We performed an anatomic study of the intervertebral foramen at 4 levels (C3/4, C4/5, C5/6, C6/7) in 100 skeletally mature osseous specimens. Specimens were selected to obtain equal number of African American and Caucasian males and females (n = 25/group) aged 20 to 40 years at time of death. Foramina were photographed bilaterally with and without a silicone rubber disc. The maximal vertical height and mid-sagittal width of each foramen were digitally measured and the areas were calculated using an ellipse as a model. The average age at death for all specimens was 30 ± 6 years. The mean cross-sectional area of the C4/5 foramen was significantly smaller compared with the C5/6 (<i>P</i> < .001). C5/6 was significantly narrower than C6/7 (<i>P</i> < .001) foramen with and without disc augmentation. C3/4 was not significantly different from more caudal levels. There was no difference between male and female specimens, while African Americans had smaller foraminal sizes than Caucasians. This study provides the largest anatomical reference of the cervical intervertebral foramen. In a mature spine without facet joint hypertrophy or osteophytic changes, the C4/5 foramen was narrower than C5/6, which was narrower than C6/7. Understanding the relative foraminal areas in the nonpathological cervical spine is crucial to understanding degenerative changes as well as the anatomical changes in pathologies that affect the intervertebral foramen.