Surface anatomical landmarks for spine surgery: A CT-based study of the sternal notch and sternal angle in 1,035 patients

Background: Understanding the location of surface anatomical landmarks in relation to the cervical and thoracic spine is important for a wide array of clinical applications. The objective of this study was to investigate the influence of patient demographic and anthropometric characteristics on the locations of the sternal notch and sternal angle in relation to the spine using computed tomography (CT) of a large cohort of young adult patients without spinal pathology.Methods: Vertebral levels corresponding to the sternal notch and sternal angle were analyzed using CT of 1,035 patients. Influences of patient height, weight, body mass index (BMI), sex, and ethnicity were assessed.Results: 567 male and 468 female patients were included in this study. Mean patient height, weight, BMI, and age were 1.68 +/- 0.11 m, 81.94 +/- 24.39 kg, 27.79 +/- 7.9 kg/m2, and 25.9 +/- 5.9 years. Of the 1,035 patients, 495 were Hispanic or Latino, 321 were Caucasian, 130 were African American, 68 were Asian, 5 were identified as "other," and 16 did not have racial or ethnic data available. The location of the sternal notch in relation to the thoracic spine demonstrated a bimodal distribution pattern clustered at the T2 and T3 vertebral bodies. The location of the sternal angle in relation to the thoracic spine demonstrated a bimodal distribution pattern clustered at the T4 and T5 vertebral bodies. Moderate, negative correlations were observed between patient weight and location of the sternal notch (r =-0.447; p <.001) and sternal angle (r =-0.499; p <.001), respectively. Zero significant correlations were observed between patient height and location of the sternal notch (r =-0.045; p =.377) or sternal angle (r =-0.080; p =.229). A weak, negative correlation was observed between patient BMI and location of the sternal notch (r =-0.378; p <.001). A moderate, negative correlation was observed between patient BMI and location of the sternal angle (r =-0.445; p <.001). The locations of the sternal landmarks did not differ based on patient sex, race or ethnicity.Conclusions: The location of the sternal notch most frequently corresponds to the T2 or T3 vertebral body, while the sternal angle is most frequently located at the T4 or T5 vertebral body. Increased patient weight is associated with relatively cephalad sternal landmarks. Patient height, sex, and ethnicity are not associated with either sternal landmark.