Changes in posterior disc bulging and intervertebral foraminal size associated with flexion-extension movement: a comparison between L4-5 and L5-S1 levels in normal subjects.
BACKGROUND
No 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.


OBJECTIVE
To determine changes in posterior disc bulging and intervertebral foraminal size with flexion-extension movement, comparing L4-5 versus L5-S1 intervertebral levels.


METHODS
An in vivo study of magnetic resonance kinematics with spine flexion extension.


METHODS
Spines 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.


RESULTS
With 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.


CONCLUSIONS
This pilot study demonstrates two distinct behavior characteristics of the normal spine with flexion-extension movement.
Fredericson
M
M
Division of Physical Medicine and Rehabilitation, Stanford University Medical School, Stanford, CA 94305-5336, USA. mfred2@stanford.leland.edu
Lee
S U
SU
Welsh
J
J
Butts
K
K
Norbash
A
A
Carragee
E J
EJ
D000328:Adult; D001175:Arthrography / Q000592:standards / Q000706:statistics & numerical data; D005260:Female; D006801:Humans; D007403:Intervertebral Disc / Q000000981:diagnostic imaging* / Q000502:physiology; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging* / Q000502:physiology; D008297:Male; D009068:Movement; D015588:Observer Variation; D010865:Pilot Projects; D012016:Reference Values; D015203:Reproducibility of Results; D012447:Sacrum / Q000000981:diagnostic imaging* / Q000502:physiology; D016474:Weight-Bearing