Dimensions of the spinal canal in individuals symptomatic and non-symptomatic for sciatica: a CT study.

Measurements obtained in 50 spinal CT studies of patients referred for suspected lumbo-sacral nerve root compression, were compared to those of a group of 30 individuals asymptomatic in this respect, who had been referred for abdominal pathology. Transverse ligamentous interfacet and transverse dural dimensions were significantly reduced in the sciatica group, with usually normal interpedicular and sagittal dimensions ruling out idiopathic developmental stenosis. The borderline value for ligamentous interfacet distance (ILD) at L4-5 appeared to be 11 mm.