• M Fredericson, S U Lee, J Welsh, K Butts, A Norbash, and E J Carragee.
• Division of Physical Medicine and Rehabilitation, Stanford University Medical School, Stanford, CA 94305-5336, USA. mfred2@stanford.leland.edu
• Spine J. 2001 Jan 1; 1 (1): 10-7.

Background ContextNo previous study has used magnetic resonance imaging (MRI) to evaluate changes of posterior disc bulging and intervertebral foraminal size in the normal spine with flexion-extension movement, comparing L4-5 versus L5-S1 intervertebral levels.PurposeTo determine changes in posterior disc bulging and intervertebral foraminal size with flexion-extension movement, comparing L4-5 versus L5-S1 intervertebral levels.Study DesignAn in vivo study of magnetic resonance kinematics with spine flexion extension.MethodsSpines of three volunteers with no history of low back pain were scanned in neutral, flexion, and extension positions in a vertically open MRI system. MRI was repeated after 6 hours of normal activity and an additional 4 hours of heavy activity with a weighted vest. Posterior bulging of the intervertebral disc and the size of intervertebral foramen were measured at the L4-5 and L5-S1 levels.ResultsWith spine flexion, posterior bulging of the discs increased at L4-5 in eight of nine measurements (three different spine-loading states for each of three subjects) and L5-S1 discs in six of nine measurements. In most cases, posterior bulging decreased with extension. No significant difference was noted in the degree of disc bulge between levels. Foraminal size at L4-5 increased with flexion and decreased with extension, and the extent of these changes was greater at the L4-5 level than at L5-S1.ConclusionsThis pilot study demonstrates two distinct behavior characteristics of the normal spine with flexion-extension movement.

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