Sagittal Spino-Pelvic Alignment in Lumbosacral Spondylolisthesis

In normal subjects, sagittal spino-pelvic alignment is such that the shape and orientation of each successive anatomical segment are closely related and influence the adjacent segments. However, the sagittal spino-pelvic alignment in developmental spondylolisthesis is still unclear. The purpose of this study is to evaluate the sagittal spino-pelvic alignment in spondylolisthesis and to compare it with normal subjects. Radiographs of 120 normal subjects and 131 subjects with developmental spondylolisthesis (91 low-grade, 40 high-grade) were reviewed. Subjects with high-grade spondylolisthesis were divided according to their sacro-pelvic balance: balanced vs. unbalanced sacro-pelvis. Parameters of the sacro-pelvis, lumbosacral region, lumbar spine, thoracic spine, and global balance were assessed. Parameters were compared between all groups and a correlation study was performed between all parameters. Significant differences in all parameters are found between the different groups, except for global spino-pelvic balance. The pattern and strength of correlations is similar between normal and low-grade subjects, showing interdependence between adjacent anatomical segments. The pattern of relationships was altered in high-grade spondylolisthesis, especially for subjects with unbalanced sacro-pelvis. A relatively normal spino-pelvic alignment is maintained in low-grade spondylolisthesis and in high-grade spondylolisthesis with balanced sacro-pelvis. Spino-pelvic alignment is abnormal in high-grade spondylolisthesis associated with unbalanced sacro-pelvis. The results of this study suggest that surgical reduction of the local lumbosacral deformity might be attempted to restore a normal spino-pelvic alignment in high-grade spondylolisthesis associated with unbalanced sacro-pelvis.