[CT findings of ossification of the posterior longitudinal ligament (OPLL), with special emphasis on the relationship to clinical symptoms].

To analyze the CT findings of OPLL quantitatively, stenotic rate (thickness of OPLL/A-P diameter of the spinal canal) and occupying rate (area occupied by OPLL/area of spinal canal) were correlated with severity of the myelopathy. The cervical vertebrae were most frequently involved (88.9%). The shapes of OPPL on lateral plain radiography were various but there were slightly more continuous and mixed types than segmented or protrusion types in this series. When the occupying rate exceeded 20%, myelopathy tended to appear. And when the stenotic rate became over 30%, myelopathy tended to appear. There was statistically significant tendency that the higher the stenotic rate or patient had. Therefore we concluded the stenotic rate and occupying rate were useful indicators to evaluate the severity of OPLL.