What is the mechanism for neurogenic claudication in lumbar spinal stenosis?
Symptoms are related to the increase in lordotic posture provoked by standing or walking.
Myelographic studies have shown that in lordosis, the cross-sectional area of the spinal canal narrows because of anterior encroachment by bulging discs, posterior encroachment by shortening and thickening of the ligamentum flavum, and lateral approximation of the articular facets.
In flexion (as in sitting), all of these encroachments reverse, with a resultant increase in the cross-sectional area of the spinal canal.
This may explain why some patients with neurogenic claudication may be able to ride a stationary bike (in the sitting position), while patients with vascular claudication may still have pain.