Postural Model of Sagittal Spino-Pelvic Alignment and Its Relevance for Lumbosacral Developmental Spondylolisthesis

Comparative study of sagittal spino-pelvic alignment in children and adolescents with developmental lumbosacral spondylolisthesis compared with asymptomatic subjects. To develop a global postural model of sagittal spino-pelvic alignment. The relationships between parameters of sagittal spino-pelvic alignment in developmental spondylolisthesis are still unclear. Radiographs of 120 control 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 alignment: balanced versus retroverted sacro-pelvis. Parameters of the sacro-pelvis (pelvic incidence, pelvic tilt, sacral slope), lumbosacral region (lumbosacral angle, slip percentage), lumbar spine (lumbar lordosis, lumbar tilt), thoracic spine (thoracic kyphosis, thoracic tilt), and global balance (spinal tilt, sagittal offset between C7 and femoral heads) were assessed. Parameters were compared between all groups and a correlation study was performed between all parameters. A postural model that includes the measured parameters was used to analyze the obtained correlations. Significant differences in all parameters are found between all groups, except for sagittal offset. The pattern and strength of correlations is similar between normal and low-grade subjects, showing interdependence between sacro-pelvic, lumbosacral, lumbar, and thoracic regions. The pattern of relationships was altered in high-grade spondylolisthesis, especially for subjects with a retroverted sacro-pelvis for which correlations between pelvic incidence and pelvic tilt, and between the sacro-pelvic unit and lumbar spine geometry are lost. Children and adolescents stand with a relatively constant global sagittal spino-pelvic alignment, regardless of the local lumbosacral deformity. A normal posture is maintained in low-grade spondylolisthesis and in high-grade spondylolisthesis with a balanced sacro-pelvis. Posture is abnormal in high-grade spondylolisthesis associated with a retroverted sacro-pelvis, suggesting that surgical reduction of the local lumbosacral deformity in these patients could be attempted to restore a normal posture.