The Modified Spinal Instability Spondylodiscitis Score (mSISS): Adaptation and Validation of a Novel Classification System for Spinal Instability in Spondylodiscitis
Journal
Global Spine Journal
ISSN
2192-5682
Date Issued
2026-05-26
Author(s)
Friederike Schömig
Nima Taheri
Mohammad El-Sharkawi
Mohamed M. Aly
Gaston Camino Willhuber
Charlotte Dandurand
Martin Holas
Harvinder Singh Chhabra
Klaus Schnake
Maximilian Reinhold
Andrei F. Joaquim
Gregory D. Schroeder
Claudius Thomé
Julian Scherer
Eugen Cezar Popescu
Ulrich J.A. Spiegl
Sebastian F. Bigdon
Richard Bransford
Matthias Pumberger
Type
journal-article
Abstract
<jats:sec>
<jats:title>Study Design</jats:title>
<jats:p>Multicenter reliability and validation study.</jats:p>
</jats:sec>
<jats:sec>
<jats:title>Objectives</jats:title>
<jats:p>To adapt and validate the Spinal Instability Spondylodiscitis Score (SISS) to create a practical and reliable classification system for assessing spinal instability in pyogenic spondylodiscitis.</jats:p>
</jats:sec>
<jats:sec>
<jats:title>Methods</jats:title>
<jats:p>The original SISS was modified through structured consensus meetings within the AO Spine Trauma and Infection Knowledge Forum, resulting in the modified SISS (mSISS). The mSISS incorporates four parameters—location, extent of bone lesion, spinal alignment, and mechanical pain—to classify lesions as stable, potentially unstable, or unstable using computed tomography (CT) and clinical data. Fifteen experienced spine surgeons independently evaluated ten representative cases in two rating sessions. Intra- and interrater reliabilities were calculated using intraclass correlation coefficients (ICC) and Fleiss’ Kappa. The gold standard was established by consensus of five expert spine surgeons.</jats:p>
</jats:sec>
<jats:sec>
<jats:title>Results</jats:title>
<jats:p>The mSISS demonstrated excellent intrarater reliability for the total score (ICC 0.90, 95% CI 0.84-0.96). Interrater reliability for the total score was 0.87 (95% CI 0.77-0.97) in the first assessment and 0.89 (95% CI 0.80-0.98) in the second. Reliability of individual parameters ranged from moderate to excellent, with spinal alignment showing the highest variability but remaining within acceptable agreement levels. Agreement with the gold standard ratings was high across all parameters.</jats:p>
</jats:sec>
<jats:sec>
<jats:title>Conclusion</jats:title>
<jats:p>The mSISS is a simplified and clinically applicable scoring system for the assessment of spinal instability in pyogenic spondylodiscitis, demonstrating strong reliability among expert spine surgeons. Broader international validation is ongoing to support its integration into clinical decision-making.</jats:p>
</jats:sec>
<jats:title>Study Design</jats:title>
<jats:p>Multicenter reliability and validation study.</jats:p>
</jats:sec>
<jats:sec>
<jats:title>Objectives</jats:title>
<jats:p>To adapt and validate the Spinal Instability Spondylodiscitis Score (SISS) to create a practical and reliable classification system for assessing spinal instability in pyogenic spondylodiscitis.</jats:p>
</jats:sec>
<jats:sec>
<jats:title>Methods</jats:title>
<jats:p>The original SISS was modified through structured consensus meetings within the AO Spine Trauma and Infection Knowledge Forum, resulting in the modified SISS (mSISS). The mSISS incorporates four parameters—location, extent of bone lesion, spinal alignment, and mechanical pain—to classify lesions as stable, potentially unstable, or unstable using computed tomography (CT) and clinical data. Fifteen experienced spine surgeons independently evaluated ten representative cases in two rating sessions. Intra- and interrater reliabilities were calculated using intraclass correlation coefficients (ICC) and Fleiss’ Kappa. The gold standard was established by consensus of five expert spine surgeons.</jats:p>
</jats:sec>
<jats:sec>
<jats:title>Results</jats:title>
<jats:p>The mSISS demonstrated excellent intrarater reliability for the total score (ICC 0.90, 95% CI 0.84-0.96). Interrater reliability for the total score was 0.87 (95% CI 0.77-0.97) in the first assessment and 0.89 (95% CI 0.80-0.98) in the second. Reliability of individual parameters ranged from moderate to excellent, with spinal alignment showing the highest variability but remaining within acceptable agreement levels. Agreement with the gold standard ratings was high across all parameters.</jats:p>
</jats:sec>
<jats:sec>
<jats:title>Conclusion</jats:title>
<jats:p>The mSISS is a simplified and clinically applicable scoring system for the assessment of spinal instability in pyogenic spondylodiscitis, demonstrating strong reliability among expert spine surgeons. Broader international validation is ongoing to support its integration into clinical decision-making.</jats:p>
</jats:sec>