Screening and Predictive Value of Thoracic Ossification Observed on Lateral Radiography for Myelopathy

Purpose: Ossification of the ligamentum flavum (OLF) is known to compress neural structures, leading to myelopathy.Although computed tomography (CT) is a reliable diagnostic tool, thoracic OLF is often underdiagnosed due to the challenges of routinely performing thoracic imaging in clinical practice.Radiographs offer a more accessible option but lack established criteria for screening clinically significant thoracic OLF. Materials and Methods:Retrospective study conducted at a single institution, evaluating radiographic and clinical data from patients with thoracic OLF.A total of 142 patients were included: 69 in the myelopathy group, who had myelopathy symptoms due to thoracic OLF, and 73 in the non-myelopathy group, who had OLF observed on CT but no myelopathy symptoms.Results: The OLF diameter (8.392.42mm vs. 5.962.93mm, p<0.001) and OLF diameter ratio (0.630.15 vs. 0.420.33,p<0.001) were significantly larger in the myelopathy group compared to the non-myelopathy group.Receiver operating characteristic analysis revealed that an OLF diameter ratio 0.58 on lateral radiographs had an area under the curve of 0.817, with 73% sensitivity and 82% specificity for predicting myelopathy. Conclusion:The OLF diameter ratio measured on lateral radiographs is an effective and non-invasive parameter for identifying thoracic OLF cases with myelopathy symptoms.When the OLF diameter ratio is 0.58, clinicians should consider the possibility of myelopathy and perform further diagnostic imaging, such as CT or magnetic resonance imaging, to guide treatment decisions.