Analysis of Dynamic Factors and Spinal Sagittal Alignment in Patients with Thoracic Spondylotic Myelopathy.

Introduction: Although thoracic spondylotic myelopathy (TSM) without ossification or disc disorder has been associated with some dynamic factors in the thoracolumbar area, a detailed investigation is yet to be published. Thus, in this study, we investigated the segmental motion and sagittal alignment of the thoracolumbar area in patients with and without TSM. Methods: Patients with TSM who were treated from 2013 to 2020 were enrolled in this study. The non-TSM group consisted of sex- and age-matched patients with spinal disorders other than TSM. Segmental mobility from T10-L2 during passive maximum flexion and extension following myelography and the sagittal cobb angles of T10-L1 and L1-L5 in the standing position were measured using multidetector computed tomography (CT). The mobility of each segment was set as the difference in the angles between the two positions. Results: In total, 10 patients (8 males and 2 females, mean age 65.8 years) with TSM and 20 without TSM were enrolled. The most stenotic level was observed at T10-T11 in four cases and T11-T12 in six. The average mobility at this segment in the TSM group (5.8°) was significantly greater than that in the non-TSM group (2.1°) (p<0.001). In the TSM group, the cobb angles of T10-L1 and L1-L5 were 2.3° and 17.4° of lordosis, respectively, which differed significantly from those in the non-TSM group, which were 8° of kyphosis and 32.2° of lordosis, respectively (p<0.001 and p=0.001, respectively). Conclusions: Compared with those without TSM, patients with TSM were found to have greater segmental mobility at the most stenotic level, thoracolumbar lordosis, and decreased lumbar lordosis.