New sagittal classification of AIS: validation by 3D characterization
Introduction and aim
In order to improve surgical planning of sagittal correction in AIS, we proposed a new sagittal classification—Abelin-Genevois et al. Eur Spine J (27(9):2192–2202, 2018. https://doi.org/10.1007/s00586-018-5613-1). The main criticism is related to the fact that 2D lateral view results from the projection of the 3D deformity. The aim of this study is to show that the new sagittal classification system is a reliable system to describe the different sagittal scenarios that AIS could create both in 2D and 3D.
We performed retrospective radiograph analysis of prospectively collected data from 93 consecutive AIS patients who underwent an examination of the whole spine using the EOS® imaging system. 2D (Keops®) and 3D analyses (sterEOS®) provided frontal and sagittal spinal and spinopelvic parameters. In addition, 3D analysis provided apical vertebra rotation (AVR).
Comparing 2D and 3D measurements for the general cohort, excellent correlation can be found for all parameters, but only fairly good for T10L2 and L1S1 angles. The highest variability was observed for T10L2, differences between 2D and 3D measurements being greater when the Cobb angle increased. AVR did not influence concordance between 2D and 3D measurements. Eighty-two percent were similarly classified in 2D and 3D according to the new classification. Misclassified patients were all AIS sagittal type 3 in 3D analysis, thoracolumbar junction (TLJ) lordosis being underestimated on 2D view.
In conclusion, for the majority of cases (82%), 2D analysis may provide enough information for decision making when using a semi-automated 2D measurement system. However, in severe cases, especially when Cobb angle exceeds 55°, 3D analysis should be used to get a more accurate view on the thoracolumbar junction behavior.
KeywordsAdolescent idiopathic scoliosis Classification 3D modeling Sagittal alignment sterEOS
This paper is the result of the Masters of Science project conducted by Mareille Post under the responsibility of Pr Barend Van Royen, MD, PhD and under the supervision of Dr Kariman Abelin-Genevois, MD, PhD. The authors acknowledge Pr Barend Van Royen, MD, PhD for his support and supervision of Mareille Post, MSc, in the achievement of her scientific work, as a collaboration between the research group of Orthopedic Department of the Centre Medico Chirurgical des Massues Croix Rouge Francaise and the Medical Science School of VU Amsterdam. KAG and MP designed and wrote the manuscript. KAG conceived the study and the cohort. KAG, PR and MP collected the patients' data. SV was in charge of the methodology of the study and analyzed the data, and as biostatician was entirely and independently in charge of the statistical analysis. KAG, MP and SV reviewed and edited the manuscript. All authors read and approved the manuscript.
Conflict of interest
None of the authors have conflict of interest, except Pierre Roussouly as shareholder of Keops(R), Smaio, France.
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