The influence of surgeon experience and subspeciality on the reliability of the AO spine sacral classification system

Study Design. Cross-sectional survey. Objective. To determine the influence of surgeons’ level of experience and subspeciality training on the reliability, reproducibility, and accuracy of sacral fracture classification using the Arbeitsgemeinschaft für Osteosynthesefragen Spine Sacral Classification System. Summary of Background Data. A surgeons’ level of experience or subspecialty may have a significant effect on the reliability and accuracy of sacral classification given various levels of comfort with imaging assessment required for accurate diagnosis and classification. Methods. High-resolution computerized tomography (CT) images from 26 cases were assessed on two separate occasions by 172 investigators representing a diverse array of surgical subspecialities (general orthopedics, neurosurgery, orthopedic spine, orthopedic trauma) and experience (<5, 5–10, 11–20, >20yrs). Reliability and reproducibility were calculated with Cohen kappa coefficient (k) and gold standard classification agreement was determined for each fracture morphology and subtype and stratified by experience and subspeciality. Results. Respondents achieved an overall k ¼ 0.87 for morphology and k ¼ 0.77 for subtype classification, representing excellent and substantial intraobserver reproducibility, respectively. Respondents from all four practice experience groups demonstrated excellent interobserver reliability when classifying overall morphology (k ¼ 0.842/0.850, Assessment 1/Assessment 2) and substantial interobserver reliability in overall subtype (k ¼ 0.719/ 0.751) in both assessments. General orthopedists, neurosurgeons, and orthopedic spine surgeons exhibited excellent interobserver reliability in overall morphology classification and substantial interobserver reliability in overall subtype classification. Surgeons in each experience category and subspecialty correctly classified fracture morphology in over 90% of cases and fracture subtype in over 80% of cases according to the gold standard. Correct overall classification of fracture morphology (Assessment 1: P ¼ 0.024, Assessment 2: P ¼ 0.006) and subtype (P₂ < 0.001) differed significantly by years of experience but not by subspecialty. Conclusion. Overall, the Arbeitsgemeinschaft für Osteosynthesefragen spine sacral classification system appears to be universally applicable among surgeons of various subspecialties and levels of experience with acceptable reliability, reproducibility, and accuracy.