The lumbar ligamentum flavum is the thickest in the spine (3-5 mm normal), reflecting the highest flexion-extension loads. Its high elastin content maintains pre-tension even in neutral, preventing capsular redundancy. Hypertrophy and calcification from degeneration produce the posterior encroachment visible on MRI that contributes to central and lateral recess stenosis.
| Origin | Inferior surface of the upper lamina (anterior surface) |
|---|---|
| Insertion | Superior border of the lower lamina (posterior surface) |
| Actions | Elastic recoil returning the spine to neutral from flexion; the elastic component (80% elastin) prevents buckling into the spinal canal during extension |
|---|
Ligamentum flavum hypertrophy greater than 4-5 mm on MRI correlates with symptomatic lumbar stenosis. Decompression requires removal of the flavum over the affected levels — laminectomy removes it with the lamina while laminotomy preserves the lamina and removes the medial flavum only. Preserving the supraspinous and interspinous ligaments above reduces adjacent segment instability.
Lumbar flavum thickening causing posterior canal encroachment in lumbar stenosis requiring laminectomy or laminotomy decompression.
