• Zhi Wang, Stefan Parent, Jacques A de Guise, and Hubert Labelle.
• Research Center, Sainte-Justine University Hospital Center, Montréal, Québec, Canada.
• Spine. 2010 Jan 1;35(1):71-5.

Study DesignA radiographic study was conducted to investigate the accuracy of computer-assisted measurement of sacral morphology in a population with developmental L5-S1 spondylolisthesis.ObjectiveThe purpose of this study was to evaluate the inter- and intraobserver variability of computer measurements of sacral morphology.Summary And Background DataRecent studies have shown differences in sacral morphology among patients with spondylolisthesis. The sacral table angle (STA) is a fundamental sacral anatomic parameter that is specific and constant to each individual, while the S1 superior and S2 inferior angles are defined as anatomic measures specific to S1 and S2. Sacral kyphosis measured by Ferguson or Cobb method has also been used to evaluate the sagittal shape of the sacrum. Currently, computerized measures are gaining popularity for the study of sagittal balance, but their reliability especially in sacral morphology has never been properly evaluated.MethodsThe standing lateral radiographs of 30 adolescents were randomly selected from the radiographic database of our institution: 10 radiographs of asymptomatic individuals, 10 of subjects with low grade L5-S1 spondylolisthesis and 10 with high grade L5-S1 developmental spondylolisthesis. Three surgeons measured sacral morphologic variables on the 30 radiographs at 2 occasions, with a 15 days interval between the 2 sessions, using a computer assisted technique. Intraclass correlation coefficients (ICCs) were used for statistical analysis.ResultsThe ICC values measured within observers varied between 0.951 to 0.995, whereas the ICC measured between observers varied between 0.957 to 0.995. There was a slight decrease of the ICC measured in the high grade L5-S1 spondylolisthesis group compared to the normal subjects. However, the difference was not statistically significant.ConclusionThese results confirm the reliability and repeatability of computer-assisted angular measurement of sacral morphology in subjects with L5-S1 spondylolisthesis, even in the presence of lumbosacral junction dysplasia. The use of computerized measurements can be recommended for the evaluation of the sagittal sacral anatomy in future clinical and research studies.

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