The Influence of Regional Differences on the Reliability of the AO Spine Sacral Injury Classification System

Study Design: Global cross-sectional survey. Objective: To explore the influence of geographic region on the AO Spine Sacral Classification System. Methods: A total of 158 AO Spine and AO Trauma members from 6 AO world regions (Africa, Asia, Europe, Latin and South America, Middle East, and North America) participated in a live webinar to assess the reliability, reproducibility, and accuracy of classifying sacral fractures using the AO Spine Sacral Classification System. This evaluation was performed with 26 cases presented in randomized order on 2 occasions 3 weeks apart. Results: A total of 8320 case assessments were performed. All regions demonstrated excellent intraobserver reproducibility for fracture morphology. Respondents from Europe (k =.80) and North America (k =.86) achieved excellent reproducibility for fracture subtype while respondents from all other regions displayed substantial reproducibility. All regions demonstrated at minimum substantial interobserver reliability for fracture morphology and subtype. Each region demonstrated >90% accuracy in classifying fracture morphology and >80% accuracy in fracture subtype compared to the gold standard. Type C morphology (p₂ =.0000) and A3 (p₁ =.0280), B2 (p₁ =.0015), C0 (p₁ =.0085), and C2 (p₁ =.0016, p₂ =.0000) subtypes showed significant regional disparity in classification accuracy (p₁ = Assessment 1, p₂ = Assessment 2). Respondents from Asia (except in A3) and the combined group of North, Latin, and South America had accuracy percentages below the combined mean, whereas respondents from Europe consistently scored above the mean. Conclusions: In a global validation study of the AO Spine Sacral Classification System, substantial reliability of both fracture morphology and subtype classification was found across all geographic regions.