Hypertrophy of the ligamentum flavum (LF) has also been considered as a major cause of Lumbar spinal canal stenosis.

Thickening of the LF can compress the dural sac and nerve root, reducing the diameter of the spinal canal.

Previous studies have demonstrated that ligamentum flavum thickness (LFT) is associated with aging, disc degeneration, and lumbar spinal stenosis.

However, hypertrophy is somewhat different from thickness. LFT may increase by buckling in the mass of the LF without a change.

Thus, for evaluating hypertrophy of the whole LF, we devised a new morphological parameter, called ligamentum flavum area (LFA). In contrast to the LFT, the LFA measures the cross-sectional area of the whole LF.