Upper cervical instability: fact or fiction?

The purpose of this review is to examine the internal validity of the standardized clinical stability tests for the upper cervical spine in relation to symptomatology. Whether radiology can confirm the clinical diagnosis is also examined. The importance of radiology in this situation, the pathogenesis and the prevalence of atlanto-axial hypermobility and the clinical symptomatology are discussed.

A literature search from January 1984 to March 1995. We consulted the CD-ROM Medline with the keywords "atlanto-axial instability," "atlanto-axial dislocation," "hypermobility," "cervical spine" and "atlanto-axial joint." Ninety-six Dutch, French, German, and English publications were selected. The Documentation Centre of the Institute for Research and Postgraduate Education Physiotherapy (SWSF) was consulted with the keywords: atlanto-axial joint, upper cervical spine, segmental examination, interobserver-reliability, intraobserver-reliability, interobserver variation, intraobserver variation, manual therapy, examination, diagnostics. Finally, recent developments and views published during this study were added.

There seems to be no correlation between the amount of hypermobility or subluxation and the presence of clinical signs or neurological signs. The clinical signs can vary from relatively diffuse complaints, no symptoms and signs to serious ones. Radiology does not seem to be a reliable diagnostic mechanism in relation to upper-cervical instability. Conventional X-rays fail to give adequate information about atlanto-axial stability. CT-scan and MRI can visualize much more because of the direct sagittal projection but neither is an absolute standard. Furthermore, in relation to upper-cervical hypermobility, the validity of radiology is under debate.

There is no correlation between the measure of hypermobility and the presence of clinical symptoms. Also, the validity of the upper-cervical stability tests is questionable. In diagnostics, every radiological examination measures anatomical and morphological variables, not functional variables. Despite this, CT and MRI should be preferred in diagnostics over conventional functional radiology.