Practical Application of the AO Spine Primary Infection Classification System: Clarifying Definitions, Borderline Cases and Common Misinterpretations.
Publication/Presentation Date
10-14-2026
Abstract
Study DesignNarrative review.ObjectiveTo clarify nuances when applying the AO Spine Primary Infection Classification.MethodsThe international validation of the AO Spine Primary Infection Classification System was successful but recurring themes caused confusion. This included the exact definition and reasons for infections to transition between categories, definition of canal involvement or neural compression and whether an epidural infection superimposed on degenerative disease escalates infection severity. There was uncertainty regarding handling of multi-level or junctional infection and clinicians encountered difficulty applying the modifiers.ResultsThe difference between a Type 0 and Type 1 infection is reasonably distinct given the former is purely extraspinal whilst the latter involves spondylodiscitis or osteomyelitis without canal involvement. Type 2 infections include those with any canal involvement, regardless of whether CSF effacement occurs, in the absence of neural compression. The spinal canal is defined as the compartment dorsal to the posterior longitudinal ligament and excludes infections that are ventral to this ligament but bow into the canal. Any neural compression of the thecal sac centrally or within the foramen escalates categorization to a Type 3 infection.ConclusionsPrimary spinal infections have the potential to rapidly progress and cause devastating neurological deficits. The introduction of the AO Spine Primary Infection Classification establishes a universal language to communicate disease severity. We clarify common nuances encountered during international validation of this system including definition of canal involvement and relevance of CSF effacement, whether foraminal involvement constitutes neural compression and the nomenclature concerning multi-level or junctional disease.
First Page
21925682261498682
Last Page
21925682261498682
ISSN
2192-5682
Published In/Presented At
Kweh, B. T. S., Vaccaro, A. R., Schroeder, G., Aly, M., El-Sharkawi, M., Dandurand, C., Neuhoff, J., Karamian, B., Xiong, G., Chhabra, H. S., Bransford, R., Joaquim, A. F., & Tee, J. W. (2026). Practical Application of the AO Spine Primary Infection Classification System: Clarifying Definitions, Borderline Cases and Common Misinterpretations. Global spine journal, 21925682261498682. Advance online publication. https://doi.org/10.1177/21925682261498682
Disciplines
Business Administration, Management, and Operations | Health and Medical Administration | Management Sciences and Quantitative Methods
PubMedID
42874070
Department(s)
Administration and Leadership
Document Type
Article