Staging of osteonecrosis of the jaw requires computed tomography for accurate definition of the extent of bony disease

Management of osteonecrosis of the jaw associated with antiresorptive agents is challenging, and outcomes are unpredictable. The severityof disease is the main guide to management, and can help to predict prognosis. Most available staging systems for osteonecrosis, includingthe widely-used American Association of Oral and Maxillofacial Surgeons (AAOMS) system, classify severity on the basis of clinical andradiographic findings. However, clinical inspection and radiography are limited in their ability to identify the extent of necrotic bone diseasecompared with computed tomography (CT). We have organised a large multicentre retrospective study (known as MISSION) to investigate theagreement between the AAOMS staging system and the extent of osteonecrosis of the jaw (focal compared with diffuse involvement of bone)as detected on CT. We studied 799 patients with detailed clinical phenotyping who had CT images taken. Features of diffuse bone diseasewere identified on CT within all AAOMS stages (20%, 8%, 48%, and 24% of patients in stages 0, 1, 2, and 3, respectively). Of the patientsclassified as stage 0, 110/192 (57%) had diffuse disease on CT, and about 1 in 3 with CT evidence of diffuse bone disease was misclassifiedby the AAOMS system as having stages 0 and 1 osteonecrosis. In addition, more than a third of patients with AAOMS stage 2 (142/405, 35%)had focal bone disease on CT. We conclude that the AAOMS staging system does not correctly identify the extent of bony disease in patientswith osteonecrosis of the jaw.