Inter-observer reliability of osteoporotic fracture classification across imaging modalities for thoracolumbar osteoporotic fractures.

STUDY DESIGN: Retrospective single-center cohort study. PURPOSE: To investigate the inter- and intra-observer reliability of the osteoporotic fracture (OF) classification across different imaging protocols and levels of surgical experience in a large, consecutive cohort of patients with thoracolumbar osteoporotic vertebral fractures (OVFs). OVERVIEW OF LITERATURE: The OF classification provides a standardized morphological assessment of OVFs. Previous studies reported variable agreement (κ=0.49-0.63), and the influence of imaging modality and observer experience on reliability remains debated. METHODS: Patients aged ≥50 years with acute thoracolumbar OVFs diagnosed between 2017 and 2021 were included. Three neurosurgeons (two seniors, one junior) independently assessed fracture morphology using complete Picture Archiving and Communication System studies. Inter-observer agreement was evaluated with Fleiss's kappa and intra-observer agreement with Cohen's kappa from repeated assessments by one senior observer. Subgroup analyses used imaging protocol and observer experience. RESULTS: A total of 482 patients were included. The most common fracture types were OF 2 (43.2%), OF 4 (29.9%), and OF 3 (25.1%). Inter-observer agreement was substantial (κ=0.789; 95% confidence interval [CI], 0.75-0.83), whereas intra-observer agreement for a single senior rater was almost perfect (κ=0.917; 95% CI, 0.88-0.95). Substantial agreement was achieved across all imaging protocols (κ=0.773-0.824), although the magnetic resonance imaging (MRI)+X-ray subgroup (n=17) was underpowered. Among adequately powered subgroups, combined computed tomography (CT) and MRI provided the highest inter-observer consistency, particularly for OF 2 and OF 3 fractures, whereas CT alone was sufficient for OF 4 fractures. OF 1 (n=4) and OF 5 (n=5) cases were considered illustrative only. No significant differences were observed based on observer experience. CONCLUSIONS: The OF classification demonstrates substantial to almost perfect reliability across imaging protocols. Combined CT and MRI assessment improved agreement for intermediate fracture types in adequately powered subgroups, supporting their complementary use in clinical practice.