• Frank Schwab, Benjamin Blondel, Edward Chay, Jason Demakakos, Lawrence Lenke, Patrick Tropiano, Christopher Ames, Justin S Smith, Christopher I Shaffrey, Steven Glassman, Jean-Pierre Farcy, and Virginie Lafage.
• 1NYU Hospital for Joint Diseases, New York, NY, USA 2Orthopedic Department, Aix-Marseille University, Marseille, France 3Washington University School of Medicine, St. Louis, MO, USA 4Neurosurgery, University of California San Francisco, San Francisco, CA 5Neurological Surgery, University of Virginia, Charlottesville, VA 6Spine Institute for Special Surgery, University of Louisville, KY, USA 7Maimonides Medical Center, New York, NY, USA.
• Neurosurgery. 2013 Nov 4.

Background:Global sagittal malalignment is significantly correlated with health related quality of life scores in the setting of spinal deformity. In order to address rigid deformity patterns, the use of spinal osteotomies has seen a substantial increase. Unfortunately, variations of established techniques and hybrid combinations of osteotomies have made comparisons of outcomes difficult.Objective:To propose a classification system of spinal osteotomies, which is anatomically based, in order to provide a common language among spine specialists.Methods:The proposed classification system is based on six anatomical grades of resection (1 through 6) corresponding to the extent of bone resection and increasing degree of destabilizing potential. In addition, a surgical approach modifier is added (P or A/P). Reliability of the classification system was evaluated by an analysis of 16 clinical cases, rated two times by eight different readers, and calculation of Fleiss' Kappa coefficients.Results:Intra-observer reliability was classified as 'almost perfect'; Fleiss' Kappa coefficient averaged 0.96 (range 0.92-1.0) for resection type and 0.90 (0.71-1.0) for the approach modifier. Results from the inter-observer reliability for the classification were 0.96 for resection type and 0.88 for the approach modifier.Conclusion:This proposed anatomically-based classification system provides a consistent description of the various osteotomies performed in spinal deformity correction surgery. The reliability study confirmed that the classification is simple and consistent. Further development of its use will provide a common frame for osteotomy assessment and permit comparative analysis of different treatments.Clinical Relevance:Level IV.

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