Lumbar Spinal Stenosis

What is narrowing, and why

The spinal canal is a bony tunnel running down the back, carrying the nerves that supply the legs. Over decades it gets crowded from several directions at once: discs lose height and bulge backward, the ligament forming the roof of the canal thickens, and the facet joints at the back enlarge as they become arthritic.

None of that is unusual. It is what spines do with time. It becomes a problem when the accumulated narrowing leaves the nerves without enough room to function when you stand up.

That last part explains the whole symptom pattern. Standing upright closes the canal slightly; leaning forward opens it. So the symptoms are positional rather than constant, which is the single most useful thing about them diagnostically.

The walking pattern is the diagnosis

Patients describe legs that feel heavy, tired, achy or numb after a certain distance. Stopping helps a little. Sitting down helps a lot, and quickly. Leaning on a trolley or a walker extends the distance considerably.

That constellation is called neurogenic claudication, and it is quite different from the leg pain of sciatica, which tends to be sharper, follows one nerve, and is often worse sitting rather than better.

It is also worth distinguishing from vascular claudication, where narrowed arteries limit blood flow. That version is relieved by standing still, without needing to sit or bend, and is not affected by posture. Pulses, skin changes and the specific relieving position separate the two on examination.

How it is confirmed

The examination establishes the pattern and rules out the alternatives: hip arthritis, peripheral neuropathy, vascular disease.

An MRI shows the canal, the ligament, the facet joints and the degree of crowding. Standing flexion and extension X-rays answer a different and important question: whether any segment is moving abnormally. That finding, more than the severity of the narrowing itself, is what determines whether a decompression alone is enough.

The severity of narrowing on a film correlates loosely with symptoms. Plenty of alarming looking canals belong to people walking several miles a day. The functional history, specifically how far the patient can walk now compared with a year ago, carries more weight than the radiologist’s adjective.

What helps before surgery

Physical therapy that emphasises flexion-based exercise and general conditioning suits this condition well, because the postures that open the canal are the ones patients tolerate.

Activity modification is about preserving distance rather than avoiding movement. Interval walking, sitting down before symptoms peak rather than after, and using a stick or a trolley on longer outings all keep people active.

Epidural steroid injections are reasonable to try, particularly during a flare. The relief tends to be partial and temporary, because the underlying problem is structural rather than inflammatory.

When decompression becomes reasonable

The decision is driven by function, not by the film.

Walking distance that keeps falling, and a life that has narrowed to fit it, is the usual reason patients decide they have had enough. When the imaging shows narrowing at the levels the symptoms point to, and non-operative measures have stopped producing meaningful relief, a decompression has a clear target: remove the thickened ligament and arthritic bone crowding the canal, and give the nerves room again.

Nothing is repaired by this. The arthritis remains arthritis and the disc remains a worn disc. What changes is the space available, and for the right patient that is the entire problem.

For selected patients the same decompression can be performed through an endoscope or a tubular retractor, which spares more of the surrounding muscle.

The fusion question

Patients frequently arrive having been told the segment will need fusing.

Sometimes that is correct. A segment that moves abnormally on flexion and extension films, a significant slip, or a decompression that would require removing enough bone to destabilise the level, all argue for adding stabilisation.

Often it is not. Randomised trials have compared decompression alone against decompression plus fusion for stenosis, including in patients with a mild degenerative slip, and routinely adding the fusion did not produce better outcomes. Fusion adds operating time, hardware, a longer recovery and permanent load on the neighbouring levels.

So it is fair to ask which specific finding makes a fusion necessary in your case. A good answer names a structure, such as a slip that moves between flexion and extension views. A vague answer about arthritis or degeneration is worth a second opinion.