EFFECT OF LORDOSIS ON THE POSITION OF THE NUCLEUS PULPOSUS IN SUPINE SUBJECTS - A STUDY USING MAGNETIC-RESONANCE-IMAGING

Study Design. Healthy young women (N = 20) underwent magnetic resonanc e imaging while supine with their hips and knees flexed (flexed positi on) and supine with a lumbar roll under the low back (extended positio n). The posterior and anterior margins of the nucleus pulposus (NP) re lative to posterior and anterior margins of the adjacent vertebral bod ies were calculated from mid-sagittal T2-weighted images to determine the position change of the NP as a function of two supine postures. Ob jectives. This study describes the effect of two commonly used supine postures on the position of the NP. Summary of Background Data. Manage ment of patients with low back pain is often based on theorized positi onal changes of the NP during spinal extension and flexion. Data descr ibing NP positional changes have not been reported for noninvasive mea surements. Results. The distance of the posterior margin of the NP to the posterior margins of the adjacent vertebral bodies was greater in the extended compared with the flexed position. There was no differenc e in the anterior distance. Eight of the 20 subjects had at least one degenerative disc in the lower lumbar spine. The NPs of the degenerati ve discs did not move the same as normal discs.Conclusions. The use of a lumbar roll under the low back when supine causes an increase in th e distance from the posterior margin of the NP to the posterior portio ns of the vertebral bodies in normal discs of healthy young females. D egenerative discs deform differently from nondegenerative discs.