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Validation and Reliability Analysis of the New SRS-Schwab Classification for Adult Spinal Deformity

Liu, Yong MD*; Liu, Zhen MD; Zhu, Feng MD; Qian, Bang-ping MD; Zhu, Zezhang MD; Xu, Leilei MD; Ding, Yitao MD; Qiu, Yong MD

doi: 10.1097/BRS.0b013e318280c478
Deformity

Study Design. An inter- and intra-observer reliability study.

Objective. To determine the inter- and intra-observer reliabilities of the new SRS-Schwab system for classifying adult spinal deformity (ASD) using nonpremarked cases.

Summary of Background Data. Schwab et al reported excellent inter- and intra-observer reliability and interobserver agreement for classification based on curve type and 3 modifiers.

Methods. A total of 102 patients with ASD were included in this study, which was conducted from February 2009 to January 2012. Long-cassette standing posterior-anterior and lateral radiographs of the spine and the pelvis were obtained from patients with ASD in the fist-on-clavicle position. All 102 cases were classified according to the new SRS-Schwab classification by 4 observers. After a 2-week interval, the same classification was independently repeated by each observer with the cases in a different randomly assigned order. The Fless κ coefficient was calculated to test the inter- and intra-observer reliabilities of the new SRS-Schwab classification.

Results. With the new SRS-Schwab classification system, 12 patients were classified as having a type T curve, 30 cases as having a type L, 45 cases as having a type D, and 15 cases as having a type S. For overall classification, the mean κ value was 0.73 for interobserver reliability and 0.83 for intraobserver reliability. Disagreements occurred most often when differentiating type T curves from type L curves and when determining the pelvic incidence minus lumbar lordosis modifier.

Conclusion. With the nonpremarked cases, this new SRS-Schwab system for patients with ASD could achieve good to excellent intra- and inter-observer reliability, but the definition of thoracic or lumbar curves was still predisposed to confusion. Overall, the SRS-Schwab system is a simple and clear classification system with incorporated spinopelvic parameters, which significantly increase its value for practical usage.

With the 102 nonpremarked cases, the new SRS-Schwab system for patients with adult spinal deformity achieved excellent intraobserver reliability and good interobserver reliability, but its definition of thoracic and lumbar curves seem to need improvement. The SRS-Schwab system is a simple and clear classifi cation system with integrated spinopelvic parameters.

*School of Medicine, Southeast University, Nanjing, Jiangsu Province, China

Department of Spine Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, Jiangsu Province, China

Institute of Hepatobiliary Surgery, Affiliated DrumTower Hospital of Nanjing University Medical School, Nanjing, Jiangsu Province, China.

Address correspondence and reprint requests to Yong Qiu, MD, Spine Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Zhongshan Road No. 321, Nanjing 210008, China; E-mail: scoliosis2002@sina.com

Acknowledgment date: August 7, 2012. First revision date: October 17, 2012. Acceptance date: November 29, 2012.

The manuscript submitted does not contain information about medical device(s)/drug(s).

National Public Health Benefit Research Foundation (201002018) grant funds were received to support this work.

No relevant financial activities outside the submitted work.

© 2013 by Lippincott Williams & Wilkins