Changes in Posterior Lumbar Disk Contour Abnormality with Flexion-Extension Movement in Subjects with Low Back Pain and Degenerative Disk Disease

Objective To determine whether posterior lumbar disk contour dimensions differ in the flexed seated, upright seated, and extended seated positions. Design Two subgroups of subjects with degenerative disk disease were compared: those with central posterior disk bulge (at L4-5 or L5-S1 levels) and those with a dark nucleus pulposus without posterior disk bulge (L3-4, L4-5, and/or L5-S1 levels). Setting Academic medical center. Participants Eight subjects with a central disk bulge and 9 subjects with a dark nucleus pulposus on magnetic resonance imaging. Interventions Not applicable. Main Outcome Measures Quantitative comparisons of posterior disk contour between neutral, flexed, and extended sitting positions. Results Of 8 subjects with central disk bulge, spinal flexion (from the neutral position) produced a decreased disk contour in all subjects, whereas spinal extension (from the neutral position) produced an increased disk contour in 6 subjects, a decreased disk contour in 1 subject, and no measurable change in 1 subject. Changes in posterior disk contour in subjects with a dark nucleus pulposus were variable. Approximately half increased and half decreased, but no relation to position was determined. Conclusions The results of this pilot study suggest a consistent pattern of decreased posterior disk contour with spinal flexion and increased posterior disk contour with spinal extension in subjects with central disk bulge, but not in those with a dark nucleus pulposus.