• Zhi Wang, Stefan Parent, Jean-Marc Mac-Thiong, Yvan Petit, and Hubert Labelle.
• Sainte-Justine University Center Hospital, Quebec, Canada.
• Spine. 2008 Sep 15;33(20):2185-91.

Study DesignA radiographic study was conducted to investigate sacral morphology in a children and adolescent population with developmental L5-S1 spondylolisthesis.ObjectiveTo determine the relationship between sacral morphology and developmental L5-S1 spondylolisthesis.Summary And Background DataThe morphology of the adult sacrum has been recently shown to be abnormal in low grade spondylolisthesis. However, sacral morphology has never been evaluated in a pediatric population where remodeling and secondary changes are less pronounced. It remains unknown if these changes in sacral morphology are primary or secondary in developmental L5-S1 spondylolisthesis.MethodsThe lateral standing radiographs of 131 subjects, aged 6 to 20 years old with developmental L5-S1 spondylolisthesis (91 low grade and 40 high grade) were analyzed with a dedicated software allowing to measure the following parameters, which were analyzed for each subject by the same individual and compared to a cohort of 120 subjects without any spinal pathology with similar age and sex distribution: the sacral table index (STI), sacral table angle (STA), sacral kyphosis (SK), S1 superior angle, S2 inferior angle, and grade of spondylolisthesis. Student t test was used to compare the parameters between the groups.ResultsThis study demonstrated that STA is significantly smaller (P < 0.01) in children and adolescents with L5-S1 spondylolisthesis compared to a similar control group. Furthermore, STA is significantly smaller in high-grade spondylolisthesis when compared to subjects with low grade. There is also a significant difference in segmental sacral morphology (S1 and S2 anatomy) in the spondylolisthesis group. Increasing sacral kyphosis is also found to be significantly associated with spondylolisthesis.ConclusionThe sagittal sacral morphology is a constant anatomic variable specific to each individual and unaffected by the position of the patient in space. The anatomy of the sacrum in children and adolescents with L5-S1 spondylolisthesis is particular and different from a control group. This study suggests that sacral anatomy may have a direct influence on the progression of spondylolisthesis; a lower STA and higher sacral kyphosis may be 2 factors predisposing to vertebral slip in developmental spondylolisthesis.

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