Magnetic resonance imaging of the lumbar spine in asymptomatic older adults

Asymptomatic subjects greater than 55 years old received lumbar spine magnetic resonance imaging studies. Two radiologists, blinded to the subjects' history, independently read the scans for the presence of abnormalities. One radiologist also measured spinal canal dimensions. In 33 subjects, at least one disc bulge was present in 28 (84.8%) subjects, at least one disc herniation in 6 (18.2%), at least one degenerated facet joint in 25 (75.7%), ligamentous thickening in 22 (66.7%), and anterolisthesis in 6 (18.2%). Twenty-four (68.5%) had at least mild, 10 (28.6%) had at least moderate, and 2 (5.6%) had severe central canal stenosis. Mean osseous spinal canal diameter gradually decreased from 20.4 mm at the L1-2 level to 16.0 mm at L5-S1. Midline thecal sac diameter and lateral recess anterior-posterior diameter were relatively unchanged. Interfacet distances both slowly increased from L1-2 to L5-S1. To achieve 95% and 90% specificities, the lower-limit cutoff should be 10.7 mm and 11.9 mm for the osseous spinal canal diameter, 6.5 mm and 7.6 mm for the thecal sac, and 3.7 mm and 4.3 mm for the lateral recess. Understanding the range of findings in asymptomatic older subjects will help clinicians better treat older patients with spinal disorders.