- The two main types of lumbar spine stenosis are Foraminal Stenosis (claudicant neuropathic leg pain or nerve root compression) and Central Canal Stenosis.
- Stenosis occurs as a result of spondylosis. Normal degenerative changes of the spine include reduction in disc height, thickening of surrounding ligaments (ligamentum flavum), and development of bony spurs or osteophytes; all of which could reduce foraminal or central canal spaces and possibly cause symptoms.
“Stenosis has been found in 80% of subjects over 70 years” (Szpalski & Gunzburg, 2003.) Normal intervertebral height is 20-23mm. If this height is reduced to <15mm then spinal stenosis is likely (Janis & An, 2000.) An extended position (such as standing or walking) is thought to reduce intervertebral space by 15%, therefore making symptoms worse. A flexed position (such as sitting) is thought to increase the space by 12%, therefore reducing pressure on the nerve and relieving symptoms (Janis & An, 2000.)
- If the symptoms are unilateral, foraminal, rather than central stenosis is more likely. Further history testing and physical examination would reveal whether the leg pain was claudicant neuropathic, or a nerve root compression. Most common changes are at L4/5, L5/S1 (which would explain typical referred symptoms into the leg.)