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This article has been peer reviewed. It is the authors' final version prior to publication in Spine 32(21):2365-2374, 2007. The published version is available at DOI: 10.1097/BRS.0b013e3181557b92. Copyright © Lippincott Williams & Wilkins.


Abstract Background Context Despite technological advances in spine surgery, classification of sub-axial cervical spine injuries remains largely descriptive, lacking standardization and any relationship to prognosis or clinical decision making. Purpose The primary purpose of this paper is to define a classification system for sub-axial cervical spine trauma that conveys information about injury pattern and severity as well as treatment considerations and prognosis. The proposed system is designed to be both comprehensive and easy to use. The secondary objective is to evaluate the classification system in the basic principles of classification construction, namely reliability and validity. Study Design/Setting Derivation of the classification was from a synthesis of the best cervical classification parameters gleaned from an exhaustive literature review and expert opinion of experienced spine surgeons. Multi-center reliability and validity study of a cervical classification system using previously collected CT, MRI, and plain film x-ray images of sub-axial cervical trauma. Methods Important clinical and radiographic variables encountered in sub-axial cervical trauma were identified by a working section of the Spine Trauma Study Group (STSG). Significant limitations of existing injury classification systems were defined and addressed within the new system. It was then introduced to the STSG and applied to 11 cervical trauma cases selected to represent a spectrum of subaxial injury. Six weeks later, the cases were randomly re-ordered and again scored using the novel classification system. Twenty surgeons completed both intervals. Inter-rater and intra-rater reliability and several forms of validity were assessed. For comparison, the reliability of both the Harris and the Ferguson & Allen systems were also evaluated. Results Each of three main categories (injury morphology; disco-ligamentous complex integrity; and neurological status) identified as integrally important to injury description, treatment, and prognosis was assigned an ordinal score range, weighted according to its perceived contribution to overall injury severity. A composite injury severity score was modeled by summing the scores from all three categories. Treatment options were assigned based upon threshold values of the severity score. Inter-rater agreement as assessed by ICC of the DLC, Morphology, and Neurological Status scores was 0.49, 0.57, and 0.87, respectively. Intra-rater agreement as assessed by ICC of the DLC, Morphology, and Neurological Status scores was 0.66, 0.75, and 0.90, respectively. Raters agreed with treatment recommendations of the algorithm in 93.3 % of cases, suggesting high construct validity. The reliability if the SLIC treatment algorithm compared favorably to the earlier classification systems of Harris and Ferguson & Allen. Conclusions The Sub-axial Injury Classification (SLIC) and Severity Scale provides a comprehensive classification system for sub-axial cervical trauma, incorporating pertinent characteristics for generating prognoses and courses of management. Early data on validity and reliability are encouraging. Further testing is necessary before introducing the SLIC score into clinical practice.

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