• 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.
• *NYU Hospital for Joint Diseases, New York, New York; ‡Orthopedic Department Aix-Marseille University, Marseille, France; §Washington University School of Medi cine, St. Louis, Missouri; ‖Neurosurgery, University of California San Francisco, San Francisco, California; ¶Neurological Surgery, University of Virginia, Charlottesville, Virginia; #Spine Institute for Special Surgery, University of Louisville, Kentucky; **Maimonides Medical Center, New York, New York.
• Neurosurgery. 2015 Mar 1; 76 Suppl 1: S33-41; discussion S41.

BackgroundGlobal 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.ObjectiveTo propose a classification system of anatomically-based spinal osteotomies and provide a common language among spine specialists.MethodsThe proposed classification system is based on 6 anatomic 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 (posterior approach or combined anterior and posterior approaches). Reliability of the classification system was evaluated by an analysis of 16 clinical cases, rated 2 times by 8 different readers, and calculation of Fleiss kappa coefficients.ResultsIntraobserver 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 interobserver reliability for the classification were 0.96 for resection type and 0.88 for the approach modifier.ConclusionThis 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.

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