Spinal canal stenosis. Concept of spinal reserve capacity: radiologic measurements and clinical applications.

Radiologic measurement of central spinal canal diameters is considered a static measurement and does not necessarily indicate active stenosis. A free intracanal space is detectable with CT scanning, i.e., a container/content difference expressing reserve capacity and implying a functional identity. The obliteration of this space may induce clinical symptomatology in the elderly and in persons with developmental or acquired lumbar spinal conditions. Normal and pathologic measurements are presented.