Observer agreement in assessing flexion-extension X-rays of the cervical spine, with and without the use of quantitative measurements of intervertebral motion.

Background Context: Flexion-extension X-rays are commonly used to identify abnormalities in intervertebral motion, despite little evidence for the reliability of the information that clinicians derive from these test.

Purpose: Quantify observer agreement on intervertebral motion abnormalities assessed with and without the use of computer-assisted technology.

Study Design: Assess interobserver agreement among clinicians when they evaluate cervical flexion-extension X-rays using the methods they now use in clinical practice, and compare this to observer agreement when the same clinicians reassess the X-rays using computer-assisted technology.

Methods: Seventy-five flexion-extension X-rays of the cervical spine, obtained from several clinical practices, were assessed by seven practicing physicians who routinely assess these X-rays. Observers assessed the studies using the methods they routinely use, and then reassessed the studies, at least a month later, using validated computer-assisted methods. Agreement among clinicians with and without computer-assisted technology was assessed using kappa statistics.

Results: Agreement was poor (kappa=0.17) with methods routinely used in clinical practice. Computer-assisted analysis improved interobserver agreement (kappa=0.77). With computer-assisted methods, disagreements involved cases with severe degeneration or static misalignment where motion was within normal limits, or in fusion cases where there was between 1 and 1.5 degrees of motion at the fusion site.

Conclusions: This study suggests that commonly used methods to assess flexion-extension X-rays of the cervical spine may not provide reliable clinical information about intervertebral motion abnormalities, and that validated, computer-assisted methods can dramatically improve agreement among clinicians. The lack of definitions of instability and fusion acceptable to all the clinicians was likely a primary source of disagreement with both manual and computer-assisted assessments.