Positional MRI changes in supine versus sitting postures in patients with degenerative lumbar spine

Back pain is associated with a degree of alteration in the alignment and movement of the lumbar spine. The purpose of this study is to investigate how the degree of lumbar segmental degeneration affects sagittal changes in the lumbar spine as it shifts from the supine to the sitting (load-bearing) posture.

Thirty patients with chronic low back pain were enrolled (14 male and 16 female patients); mean age 44.5 years. Their lumbar spines were initially investigated by conventional supine magnetic resonance imaging (MRI) followed later by positional MRI in the seated posture. Of the 150 discs studied, 87 were classified as healthy grade 1, 16 as grade 2, 34 as grade 3, and 13 as grade 4.

As the lumbar spine was loaded from the supine to the sitting position, the end-plate angles were decreased significantly as the degeneration was increased. There were also significant changes in the anterior and middle disc heights between the supine and the sitting postures irrespective of the degree of degeneration. The overall lumbar lordosis did not significantly change between the two postures.

We have found that the changes in the segmental motion were related to the degree of degeneration. With positional MRI, we were able to demonstrate changes in healthy and degenerative discs in the weight-bearing position. More similar studies are needed to understand the complex kinematics of the lumbar spine.