Sensitivity and specificity of dural sac and herniated disc dimensions in patients with low back-related leg pain

Narrow spinal canals or herniated discs can be associated with leg pain. Ho wever, it is not known whether quantitative measurements of the spinal cana l or herniated disc are sensitive and specific for low back-related leg pai n. The size and cross-sectional area of the dural sac and any herniated dis cs were measured from magnetic resonance Imaging examinations of 22 asympto matic individuals and 44 patients with sciatica. The sensitivity and specif icity of these measurements were determined. in this small population of pa tients, a dural sac anteroposterior (AP) diameter of 10.2 mm at the L3-4, L 4-5, or L5-S1 vertebral levels was 74% sensitive and 74% specific for leg p ain. Based on measurements in symptomatic patients, a herniated disc with a n AP diameter of approximately 3 mm was over 95% sensitive and 95% specific . However, if the AP diameters of herniated discs in symptomatic patients w ere compared with similar measurements In asymptomatic controls, the most s ensitive and specific threshold value was 6.8 mm. These findings must be co nfirmed in a larger population before they are applied clinically. (C) 2000 Wiley-Liss, Inc.