Vertebral body osteonecrosis: proposal of a treatment-oriented classification system

Purpose To present a classification system for vertebral body osteonecrosis (VBON) based on imaging findings and sagittal alignment and consequently to propose treatment guidelines. Methods Chart review and classification of imaging and clinical findings. An analysis of literature about VBON has been evaluated to conceive the classification. The current data allows to correlate radiological findings with different stages of the pathophysiological process and consequently to propose a patient-tailored treatment plan. Results The classification identifies 4 stages: stage 0 (theoretical phase), stage 1 (early phase), stage 2 (instability phase) and stage 3 (fixed deformity phase). Local (angular kyphosis expressed as anterior–posterior wall height ratio) and global (sagittal vertical axis and pelvic tilt) sagittal alignment are considered as complementary modifiers to tailor the most suitable treatment. Stage 1 is generally managed conservatively. Stage 2 and 3 often require different surgical approaches according to local and global sagittal alignment. Conclusions The classification allows a systematic staging of this disease and can help establish a proper and patient-oriented treatment plan. Further researches are advocated to fully validate the proposed classification system. Graphical abstract These slides can be retrieved under Electronic Supplementary Material.