Effects of Standing on Spinal Alignment and Lumbar Intervertebral Discs in Young, Healthy Individuals Determined by Positional Magnetic Resonance Imaging

Abstract

Traditional diagnostic imaging of the spine is performed in supine, a relatively unloaded position. However, the spine is subjected to complex loading environments in daily activities such as standing. Therefore, we seek to quantify the changes from supine to standing in the spines of young, healthy individuals in standing using a positional MRI system. This is an observational study that examined the changes in the spine and individual intervertebral discs (IVDs) during supine and standing of forty healthy participants (19 males / 21 females) without a history of low back pain. The regional lumbar spinal alignment was measured by the sagittal Cobb angle. Segmental IVD measurements included the segmental Cobb angle, anterior to posterior height (A/P) ratio, and IVD width measured at each L1/L2 - L5/S1 levels. The intra-observer intra-class correlation (ICC) consistency model showed values for measurements ranged from 0.76-0.98. The inter-observer ICC values ranged from 0.68-0.99. The Cobb angle decreased in standing. The L5/S1 segmental Cobb angle decreased in standing. The L2/L3 and L3/L4 A/P ratios increased and the L5/S1 A/P ratio decreased in standing. No differences in IVD width were observed from supine to standing. This study examined the regional lumbar spinal alignment and segmental IVD changes from supine to standing in young, healthy individuals without LBP using pMRI. In developing and validating these measurements, we have also established the normative data for healthy, asymptomatic population that could be useful for other investigations examining how individuals with spinal or IVD pathologies may adapt between supine and standing.