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[Functional roentgen diagnosis of the upper cervical spine].

For evaluation of the function of the upper cervical spine, especially assessment of the range of motion, functional X-rays films are useful in addition to the clinical examination. For the diagnosis of segmental instability, passive motion should be induced in order to obtain the full range. If anterior instability of the upper cervical spine is suspected, flexion-extension X-rays in the lateral view are appropriate. If a lesion of the alar ligaments is suspected, then lateral flexion X-rays films should be taken. In the normal situation, the atlas glides in the direction of bending, coupled by forced rotation of the axis. In cases with rotatory instability of the upper cervical spine, functional computed tomography should be performed. Atlantoaxial rotation of more than 52 degrees should be considered pathological as a result of a lesion of the alar ligaments. For examination of the relationship between the spinal cord and bony structures or inflammatory tissue in patients with rheumatoid arthritis, functional MRIs are helpful. Not only the exact diameter of the spinal canal can be measured during flexion and extension, but the degree of basilar impression or cranial migration of the axis can also be assessed. Optimal use of functional X-ray diagnostics, including functional the CT and MRI, is not only helpful for clinical diagnoses, but also for the planning of surgical procedures.