What is the surface anatomy of the seventh cervical vertebra (C7)?

From the Research

The C7 vertebra, also known as the vertebra prominens, is not always reliably identified by its prominently projecting spinous process, as it is only the most prominent in less than 50% of cases, according to a recent cadaveric study 1. To locate C7, having the patient flex their neck forward and identifying the most prominent spinous process at the cervicothoracic junction can be attempted, but this method may not be accurate in all cases. The identification of C7 is crucial for several clinical purposes, including counting vertebrae, localizing spinal levels during physical examination, and guiding needle placement for procedures like epidural injections. Some studies suggest that using a flexion-extension method, where the patient's cervical spine is flexed and extended to identify the lowest freely moving spinous process as C6 and the following stationary cervical spinous process as C7, may be more accurate than the conventional method of palpation 2. However, the variability in the projection level of the most prominent spinous process of the cervical vertebrae, as noted in the study by 1, highlights the importance of considering individual anatomical variations when attempting to identify C7. Key points to consider when locating C7 include:

• The spinous process of C7 may not always be the most prominent, with C6 being the most prominent in 35.9% of cases in one study 1.
• The use of three-dimensional computed tomography reconstruction can provide detailed information about the anatomy of the C7 spinous process, including its deviation and dimensions 3.
• The accuracy of identifying C7 can be influenced by factors such as the patient's age, gender, and body mass index (BMI), but the flexion-extension method has been shown to be more accurate than the conventional method regardless of these factors 2. Therefore, a combination of palpation techniques, including the flexion-extension method, and consideration of individual anatomical variations, is recommended for accurately identifying the C7 vertebra 1, 2.