Seated Lateral X-ray Is a Better Stress Radiograph of the Lumbar Spine Compared to Standing Flexion.

Study Design: Prospective lumbar radiograph analysis.

Objective: To compare changes in lumbar lordosis in standing flexion versus seated lateral radiographs.

Methods: Standing lateral, standing flexion, and seated lateral X-rays of the lumbar spine were obtained in patients presenting with low back pain. Trauma, tumor, and revision cases were excluded. Changes in global lumbar as well as segmental lordosis were measured in each position.

Results: Seventy adult patients were reviewed. Overall, the greatest changes in lordosis were seen at L4-S1 in both the seated and flexion X-rays (12.5° and 6.3°, respectively). Greater kyphosis was seen in seated versus flexion X-rays (21.6° vs 15.8°); changes in lordosis from L1-L3 were similar in both positions, with little change seen at these levels (approximately 5° to 7°). On subgroup analysis, these differences were magnified in analyzing only patients that moved at least 20° globally, and there were no significant differences between sitting and flexion in "stiff" patients that moved less than 20° globally.

Conclusion: Greater lumbar kyphosis was seen in the seated position compared to standing flexion, especially from L4-S1. Given these results we suggest the use of seated lateral X-rays to dynamically assess the lumbar spine. These findings may also guide future research into the mechanism and clinical relevance of a stiff versus mobile lumbar spine, as well as into the sensitivity of seated X-rays in detecting instability.