OBJECTIVE: To establish the mechanism of the thoracolumbar spine during trunk rotation and its restriction.
DESIGN: Patients with one-sided rotation restriction were examined seated on a chair with the pelvis fixed in neutral position, at maximum right and left trunk rotations, before and after mobilization of movement restriction; anteroposterior X-rays were taken with a horizontal beam on a vertical X-ray cassette.
SETTING: University neurology clinic.
MAIN OUTCOME CRITERIA: Assessment of rotation and side bending of the thoracolumbar spine (a) on the normal and the restricted side and (b) after mobilization.
RESULTS: In all cases, there was both (coupled) rotation and side flexion during side bending, except that the thoracolumbar junction was frequently near midline; in such cases, the thoracic spine above was bent in the opposite direction. Both rotation and side-bending started at L5 and continued gradually in a cranial direction without a noticeable maximum at any level.
CONCLUSIONS: Although it is generally assumed that the configuration of the lumbar zygapophyseal joints precludes axial rotation in the lumbar spine, I find that, during trunk rotation, a coupled movement of side bending and rotation takes place in the lumbar spine and continues without a noticeable break into the thoracic spine. The site of movement restriction, which usually seems to be located at the thoracolumbar junction, cannot be visualized on X-rays.
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