Prevalence and Distribution of Incidental Thoracic Disc Herniation, and Thoracic Hypertrophied Ligamentum Flavum in Patients with Back or Leg Pain: A Magnetic Resonance Imaging-Based Cross-Sectional Study

Objective This study is aimed to comprehensively assess the prevalence and distribution of thoracic disc herniation (TDH) or thoracic hypertrophied ligamentum flavum causing stenosis (HLFS) by magnetic resonance image (MRI) in patients with back or leg pain. Methods The study participants included 2212 patients who underwent MRI evaluation for back or leg pain. The prevalence and distribution of TDH or thoracic HLFS were assessed using lumbar MRI with cervicothoracic sagittal images. The presence of TDH or HLFS and the clinical parameters such as age, sex, lumbar surgical need, and thoracic operation were retrospectively reviewed. Logistic regression analysis of the data was followed. Results The prevalence rates of TDH and thoracic HLFS in all patients were 6.5% (145/2212) and 19.0% (421/2212), respectively. The prevalence of TDH was demonstrated as a relatively even distribution across age groups, higher in male participants (8.0%) than in female participants, and more frequent in patients with lumbar surgical lesions (8.2%) than without surgical lesions. Whereas, the prevalence of thoracic HLFS tended to increase with age, was higher in female participants (21.6%) than in male participants, and had no association with presence of lumbar surgical lesions. The most frequently involved segments of TDH and HLFS were T8/9 and T10/11, respectively. Six of 145 patients with TDH and 15 of 421 patients with HLFS underwent surgery. Conclusions The prevalence of TDH had a significant association with the presence of lumbar surgical lesions and no association with age. The prevalence of thoracic HLFS had a strong association with age and no association with lumbar surgical lesions.