Lumbar Spine and Pelvic Posture Between Standing and Sitting: A Radiologic Investigation Including Reliability and Repeatability of the Lumbar Lordosis Measure

ObjectiveSitting has been identified as a cause of mechanical low back pain. The purpose of this study was to use plain film x-rays to measure lumbar spine and pelvic posture differences between standing and sitting.MethodsEight male subjects were radiographed standing and sitting in an automobile seat. Measures of lumbar lordosis, intervertebral disk angles, lumbosacral angle, lumbosacral lordosis, and sacral tilt were completed. One-way analysis of variance (α = .05) was conducted on the variables stated above. A Bland-Altman analysis was conducted to assess agreement and repeatability of the lumbar lordosis angle using 2 raters.ResultsLumbar lordosis values in standing (average, 63° ± 15°) and sacral inclination (average, 43° ± 10°) decreased by 43° and 44°, respectively, in sitting. Intervertebral joint angles in sitting underwent substantial flexion (L1/L2—5° [±3°], L2/L3—7° [±3°], L3/L4—8° [±3°], L4/L5—13° [±3°], and L5/S1—4° [±10°]). Measures of lumbar lordosis; intervertebral disk angles between L2/L3, L3/L4, and L4/L5; lumbosacral lordosis; lumbosacral angle; and sacral tilt were significantly decreased between standing and sitting (P < .001). Intervertebral disk angle between L5/S1 was not significantly different. Analysis using the Bland-Altman technique found good agreement and stable repeatability of measures with no statistical significant differences between or within raters (R1, P = .8474; R2, P = .4402; and R-R2, P = .8691).ConclusionThe significant differences in lumbar and pelvic measures from standing to sitting further emphasize the range of motion experienced at vertebral levels in sitting. Based on the results of this study, interventions to return motion segments to a less flexed posture should be investigated because they may play a role in preventing injury and low back pain.