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

Abstract

Introduction: Textbook description of spinal stenosis is worsened symptoms in downslope posture and improved symptoms in upslope posture due to respective extension and flexion movements of the lumbar spine causing changes in 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. Methodology: 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 alignments were measured and evaluated. Results and Analysis: The lumbar alignment from L1-L5 did not have significant changes in both downslope and upslope settings. 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. In contrast, the balancing mechanism in upslope setting favours translation of global alignment forward as evident by increased C2-Hip axis angle, sagittal vertical axis, C2-C7 sagittal vertical axis and sacral slope, which is compensated by decreased thoracic kyphosis. Discussion and Conclusion: This study suggests that the lumbar lordosis does not change with different postures, but the spine balance is maintained by compensatory mechanisms contributed by all segments including changes in cervical and thoracic alignments.