Final answer:
A measurement called Space Available for the Spinal Cord (SAS) indicates a C1 fracture or transverse ligament rupture. This measurement is obtained through imaging techniques and determines the amount of space available for the spinal cord in the spinal canal.
Step-by-step explanation:
The measurement that indicates a C1 fracture or transverse ligament rupture is called a Space Available for the Spinal Cord (SAS) measurement. This measurement is taken through imaging techniques such as magnetic resonance imaging (MRI) or computed tomography (CT) scans. The SAS measurement determines the amount of space available for the spinal cord in the spinal canal.
A normal SAS measurement range is considered to be between 13-27 mm. However, if there is a C1 fracture or transverse ligament rupture, this measurement may decrease, indicating compression or narrowing of the spinal canal. In such cases, a SAS measurement of less than 13 mm could suggest the presence of a C1 fracture or transverse ligament rupture.