Fig. 1.

(A) The cross-sectional area (CSA) of the spinal canal (red arrow and text) and the thickness (yellow arrow and text) and area (green arrow and text) of the ligamentum flavum (LF) were measured at the mid-disc level of the axial sequence using T2-weighted magnetic resonance imaging. (B) Intervertebral disc height (DH) was measured in lateral radiography as the length of the line from the midpoint of the inferior endplate to the superior endplate vertically. (C) Subsidence was measured by the degree of cage subsidence into the vertebral endplates on lateral radiography.