Lumbar spinal stenosis (narrowing of the space for the nerve in the lower back) is a condition affecting mainly the middle-aged and beyond. It occurs due to gradual narrowing of the space for the nerves. One of the functions of the spinal column in our body is to facilitate the passage and exit of nerves. The nerves in the lower back or lumbar spine mainly travel to the legs, and they serve both motor (giving instructions to the muscles in the legs to move) and sensory (receiving various sensory feedback from the skin of the legs) functions. Some of the nerves that travel in the lower back spinal column are responsible for control of the bladder and bowel.

Contributing Factors

Thickening of the ligamentum flavum (yellow ligament) in the spinal canal over time

Enlarged facet joints on both sides of the spinal column that protrude against the nerves

Bulging discs that protrude against the nerves

Misalignment of the spinal column resulting in compression of the nerves. If there is forward slip of the vertebra when viewed from the side, this is called spondylolisthesis (Figure 1). Similarly, if there is a backward slip of the vertebra when viewed from the side, this is called retrolisthesis. If there is misalignment when viewed from the back, this is called scoliosis (Figure 2).

An x-ray of a forward slip of the vertebra viewed from the side

Figure 1

An x-ray of a spinal misalignment viewed from the back

Figure 2

Common Symptoms

Pain in the legs or calves, as well as the lower back after standing and walking, which is relieved by sitting down or leaning forward. When the lower back is bent forward, slightly more space is made available for the nerves, causing a reduction in symptoms.

Numbness, pins and needles sensation, or loss of motor strength in the leg(s). These complaints can lead to significant impairment in quality of life. Patients may find shopping, travelling, and social activities increasingly difficult, as leg symptoms tend to worsen when standing or walking for prolonged periods. In one-third of cases, the ability to walk gradually diminishes.

Diagnosis

Medical history – It is important during the clinical consultation to rule out peripheral vascular disease (reduced blood flow to the legs) as another possible diagnosis.

Physical examination

Investigations

X-rays – reveal structural changes, such as loss of disc height, bone spurs, and malalignment of the spine, which may signify abnormal motion and possible instability.

MRI (Figure 3) – allows closer assessment of nerve compression and identification of the structures involved (e.g. discs, bone spurs, thickened ligaments).

An MRI scan on the low back (lumbar) spinal nerve

Figure 3

Lumbar Spinal Stenosis Treatment Options

Non-Surgical

In the absence of severe or progressive nerve damage, the doctor will usually manage spinal stenosis using the following non-surgical measures:

Non-steroidal anti-inflammatory drugs to reduce inflammation and relieve pain. Other medications that modulate nerve pain can also be used, for example pregabalin.

Prescribed exercises and/or physiotherapy to maintain motion of the spine, strengthen abdominal and back muscles, and build endurance, all of which help stabilize the spine. Patients may be encouraged to try slowly progressive aerobic activities such as swimming or using stationary bicycles.

A lumbar corset or back brace to provide support and help regain mobility. This approach is sometimes used if the patient has weak abdominal muscles or multi-level degeneration of the spine. The corset should be used on a temporary basis only, as prolonged use may weaken the back and abdominal muscles.

Acupuncture to help with pain management.

Spinal Injection

The doctor may recommend spinal injections if the above non-surgical treatments do not adequately relieve symptoms. Spinal injections or nerve root blocks near the affected nerves are performed to temporarily relieve pain and nerve inflammation. This can be done as a day surgery procedure in the operating room where sterility is ensured and imaging access to the spine is available.

At the same time, injections into the facet joints and the medial branch nerves (nerve supply to the facet joints) may also be performed to relieve inflammation of the facet joints.

Surgery

Surgery should be considered if patients develop numbness or weakness that interferes with walking, or impaired bowel or bladder function. Otherwise, surgery may be considered if there is no significant improvement with non-surgical treatments, or if quality of life is significantly affected.

The purpose of surgery is to relieve pressure on the nerves (decompression), and in some cases restore and maintain spinal alignment (stabilization). Such procedures can be performed using minimally invasive techniques with specially designed tubular systems.

Decompression

Decompression can be performed by decompressive laminectomy, i.e. removal of the lamina (roof) of one or more vertebrae to create more space for the nerves. This procedure can often be done via minimally invasive techniques using tubular retractors.

The decompression removes structures that compress the nerve(s), including thickened ligamentum flavum, bone spurs from the facet joints, and protruding discs.

Stabilization

If the affected spinal segment is unstable, e.g. spondylolisthesis (forward slip of the vertebra) or lateral listhesis in degenerative scoliosis (sideways slip of the vertebra), stabilization may be required. This involves both fusion and instrumentation.

Fusion often involves the use of the patient’s own bone from the removed lamina or facet. Instrumentation involves placement of titanium screws into the vertebrae (Figure 4).

Various methods may be used to enhance fusion and strengthen unstable segments, e.g. cages placed in the intervertebral disc spaces (Figure 4). The doctor may also use BMP (bone morphogenetic protein) to improve fusion success rates, especially in higher-risk patients such as those with diabetes, smokers, multi-level surgeries, or revision surgeries.

An x-ray of five titanium screws placed on the vertebrae

Figure 4

Non-fusion Surgery

Non-fusion surgery (often performed in a minimally invasive manner) may be used in selected patients. This involves the use of dynamic devices (e.g. interspinous spacers inserted between the spinous processes) together with decompression laminectomy, to restrict but not completely eliminate spinal motion at the affected level.

When to Consult a Spine Specialist

Lumbar spinal stenosis can lead to progressive pain, numbness, or weakness that affects mobility and quality of life. Early assessment by a spine specialist helps determine whether non-surgical treatment or surgery is appropriate based on the severity of nerve compression and symptoms.

	Dr Hee Hwan Tak Orthopaedic Surgeon & Spine Specialist MBBS (Singapore) \| FRCS (Edinburgh) \| FRCS (Glasgow) \| FAMS (Ortho)
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