Classification of Orbital Fractures Using the AO/ASIF System in a Population Surveillance Cohort of Traumatic Optic Neuropathy

Abstract

Purpose: In our prospective nationwide surveillance study of traumatic optic neuropathy (TON) in the United Kingdom, the prevalence of orbital fractures was found to be 39% (47/121). The prevalence of skull fractures was 7.4% (9/121). This study aims to identify the association of craniofacial-orbital fractures with the severity of visual loss.Methods: TON patients who sustained orbital fractures were identified prospectively by population-based active surveillance through the British Ophthalmic Surveillance Unit over a 2-year period. Available CT scans were classified by a head and neck radiologist according to the Arbeitsgemeinschaft für Osteosynthesefragen/Association for the Study of Internal Fixation (AO/ASIF) scheme: the face was divided into 4 units; fractures in each unit were graded according to displacement (A–C) and severity (1.1–3.3). Correlation between severity of craniofacial orbital fractures and visual acuity as well as number of fractured units and visual acuity were evaluated.Results: Twelve of the 25 patients (48%) with imaging available had adequate high resolution craniofacial CT imaging for review and classification using the AO/ASIF system (i.e. 48 classifiable units). Three of 48 (6%) units were undisplaced (grade A), 18 of 48 (29%) units were minimally displaced (grade B), and 4 of 48 (8%) units had largely displaced (grade C) fractures. Twenty-three units (47.9%) had no fractures; 5 patients had radiological evidence of optic canal fractures. Poor visual acuities positively correlated with severity of fractures graded using the AO/ASIF classification (Spearman’s rho = 0.95, p = 0.05) and number of fractured units (Spearman’s rho = 1.0, p < 0.0001).Conclusion: AO/ASIF classification system provides a uniform method in the assessment of orbital fractures which correlates with visual outcome in TON.