Distinctive features of upright CT myelography in patients with lumbar spine degenerative diseases

Purpose: Recently, a full-body upright computed tomography (CT) scanner has been developed, which when combined with myelography, is expected to provide valuable insights into the pathology of lumbar spine degenerative diseases (LSDD). This study aims to elucidate the distinctive features of upright CT myelography (CTM) in LSDD by comparing it with supine magnetic resonance imaging (MRI). Methods: This study included 110 patients who underwent both supine MRI and upright CTM for LSDD. The anteroposterior diameter (APD), transverse diameter (TD), and area of the dural sac were measured from L1/2 to L5/S1. Lumbar lordosis (LL) was also measured in both modalities. Results: The APD of the dural sac was significantly smaller at L2/3 and L4/5, while the TD was significantly larger at L1/2 and L2/3 on upright CTM compared to supine MRI. The dural sac area was significantly larger at L1/2 and smaller at L4/5 on upright CTM. Subgroup analysis divided patients into Group I (LL greater in upright CTM, n = 56) and Group D (LL smaller in upright CTM, n = 54). The dural sac area was significantly smaller at L3/4 and L4/5 in Group I and larger at L1/2 in Group D on upright CTM. Conclusions: Changes in the APD, TD and area of the dural sac during the transition from supine to standing were markedly dependent on the intervertebral level. These parameters were also influenced by patterns of change in LL between the two positions. Upright CTM revealed diverse position-related morphological changes in the lumbar dural sac in LSDD patients.