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

Abstract

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 (8.39 +/- 2.42 mm vs. 5.96 +/- 2.93 mm, p<0.001) and OLF diameter ratio (0.63 +/- 0.15 vs. 0.42 +/- 0.33, 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.