Importance of gap evaluation in the ossification of posterior longitudinal ligament lesions using three-dimensional computed tomography.

BACKGROUND CONTEXT Evaluating the gaps within the ossification of the posterior longitudinal ligament (OPLL) lesions, which may contribute to neurological symptoms, using conventional imaging techniques is challenging. OBJECTIVE This study aimed to investigate the importance of evaluating gaps using three-dimensional computed tomography (3D-CT) and their association with the occurrence of magnetic resonance imaging (MRI) T2 high intensity in the spinal cord. STUDY DESIGN/SETTING Retrospective cohort study. PATIENT SAMPLE Retrospective analysis of 116 patients diagnosed with cervical OPLL. OUTCOME MEASURES Presence of gaps in OPLL, presence of T2 high intensity in the cervical spinal cord, and OPLL thickness were evaluated. METHODS Lateral X-ray, CT, and reconstructed 3D-CT images were reviewed to assess lesion characteristics and the presence of gaps. MRI was used to evaluate the change in spinal cord signal intensity. The relationship among gap presence, lesion morphology, and MRI T2 high intensity in the spinal cord was examined. RESULTS A significant difference in gap detection accuracy was observed between CT and 3D-CT (p = 0.0054). CT demonstrated false-positive results in the detection of gaps as compared with 3D-CT. The presence of gaps was significantly associated with an increased likelihood of MRI T2 high intensity in the spinal cord (p = 0.037). Patients with thicker lesions and smaller space available for the spinal cord (SAC) were more likely to exhibit T2 high intensity. Meanwhile, patients with gaps co-occurring with T2 high intensity exhibited significantly thinner lesions (p = 0.011) and larger SACs (p = 0.0002). Patients with gaps had a significantly lower JOA scores (p = 0.0035), which indicates that patient with gaps are likely to exhibit more severe clinical neurological symptoms. CONCLUSION 3D-CT showed superiority in accurately identifying gaps within OPLL lesions, while CT demonstrated false-positive results in the detection of gaps. Furthermore, the gap presence was a risk factor for MRI T2 high intensity in the spinal cord, independent of lesion thickness. In addition, gaps are related to more severe clinical symptoms. This study highlighted the importance of evaluating gaps within OPLL lesions using 3D-CT to clarify neurological pathogenesis.