Affiliations: [a] Division of Physical Medicine and Rehabilitation, Stanford University Medical School, Stanford, CA, USA | [b] Department of Radiology, Stanford University Medical School, Stanford, CA, USA | [c] Department of Physical Medicine and Rehabilitation, Seoul National University, College of Medicine, Boramae Municipal Hospital, Seoul, Korea | [d] Department of Radiology, Harvard Medical School, Brigham and Woman's Hospital, Boston, MA, USA
Correspondence:
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Address for correspondence: Michael Fredericson, M.D., Division of Physical Medicine and Rehabilitation, Edwards R105D, Stanford University Medical Center, 300 Pasteur Drive, Stanford, CA 94305-5336, USA. Tel.: +1 650 723 1410; Fax: +1 650 498 7546
Abstract: Flexion and extension of the spine induce loads to the anterior or posterior spinal column and therefore may affect disc hydration. Information related to the effect of activity on hydration of intervertebral discs could lead to a better understanding of the pathophysiology and rehabilitation of low back injury. A pilot study evaluating the effect of spine position and loading on the changes of disc hydration in vivo was conducted with three volunteers without low back pain history. Spines were scanned in neutral, flexion and extension positions. MRI was repeated after 6 hours of normal activity and 4 hours of heavy activity with a weighted vest. Signal intensities of the intervertebral discs were measured at the L4-5 and L5-S1 levels. The signal intensities decreased by 9.3% at L4-5 and 8.3% at L5-S1 intervertebral discs compared to baseline after 6 hours of daily activity. The intensities decreased more (14.5% and 12.4%) with additional four hours of heavy activity. There was no change in disc signal intensity between neutral, flexion and extension of the spine. This study showed that: 1) rapid fluctuation of load such as between flexion and extension does not change disc hydration 2) prolonged loading of the spine decreases disc hydration.
Keywords: flexion-extension, vertically open MRI, disc hydration
