Changes in sagittal alignment in upslope or downslope: An insight into dynamic spinal stenosis symptomatology

Abstract

Introduction: Classical textbook description of symptomatic spinal stenosis is worsened symptoms while walking on a downslope and improved in upslope posture as a result of respective extension and flexion movements of the lumbar spine with resultant reduction and relative increased spinal canal diameter. However, these dynamic changes and resulting changes in sagittal alignment have not been studied. Hence, the aim of study is to analyze the changes in sagittal alignment with downslope and upslope positions to better understand the dynamic changes in the spine related to lumbar spinal stenosis. Methods: Ten asymptomatic young adults without back pain, spinal disease or surgery were recruited. Whole body biplanar images were obtained at level ground standing, standing on 20 degrees downslope and 20 degrees upslope using an adjustable slant board. Sagittal parameters included spinopelvic parameters (lumbar lordosis (L1-S1), thoracic kyphosis (T5-12), pelvic tilt, sacral slope, pelvic incidence), lower limb parameters (posterior pelvic shift, knee flexion angle) and global balance parameters (sagittal vertical axis, C2-hip axis) were measured and evaluated. Results: The lumbar alignment did not have significant changes in both downslope and upslope settings. Main compensatory changes occurred in the lower lumbar segments at L4/5 and L5/S1 The balancing mechanism in downslope setting were different in each individual but the net outcome was to maintain a balanced spine with little change in global alignment. The balancing mechanism in upslope setting favors translation of global alignment forward as evident by increased C2-Hip axis angle, sagittal vertical axis, C2-C7 sagittal vertical axis and sacral slope, along with decreased thoracic kyphosis. Discussion: This study suggests that the overall balance and posture, especially lumbar lordosis do not change with different postures. The spine balance is maintained by compensatory mechanisms contributed by all segments including changes in cervical and thoracic alignments. Our findings of compensatory changes occurring more dramatically at L4/5 and L5/S1 suggest that in lumbar spinal stenosis, lower levels’ spinal canal diameter may be affected more by dynamic postures than the upper levels. Symptoms occurring with different slope-walking may only be relevant to lower lumbar compressions.