Lumbar spinal stenosis is a disease that mainly affects the middle-aged and the elderly. It is caused by the gradual narrowing of the spinal canal due to encroachment by thickened yellow ligament, enlarged facet joints, and bulging discs. This results in the narrowing of space for the nerve.
Typically, a person with spinal stenosis complains about developing tremendous pain in the legs or calves and lower back after walking. It is relieved by sitting down or leaning over. This is because more space is available for the spinal canal when the spine is bent forward, causing a reduction in symptoms.
Although symptoms may arise from narrowing of the spinal canal, not all patients develop symptoms. Why some patients develop symptoms and others do not remains a mystery. Therefore, the term spinal stenosis refers not to the finding of spinal canal narrowing, but rather to manifestation of leg pain caused by compression on the affected nerves.
The risk of developing spinal stenosis increases in those who:
- are born with a narrow spinal canal
- are female
- are 50 years of age or older (osteophytes or bony spurs associated with aging)
- have had previous injury to the spine
How is spinal stenosis diagnosed?
Diagnosis of spinal stenosis is usually made clinically. It is important during the clinical evaluation to rule out peripheral vascular disease (or lack of blood flow to the legs) as a possible diagnosis.
Investigations to confirm spinal stenosis include the use of x-rays. Specialised investigation like MRI will reveal the level and nature, as well as the severity of the spinal stenosis.
In the absence of severe or progressive nerve involvement, we can manage spinal stenosis through the following conservative measures:
- Nonsteroidal anti-inflammatory drugs (NSAIDs) to reduce inflammation and relieve pain
- Analgesics (painkillers) to relieve pain
- Nerve root blocks near the affected nerve to temporarily relieve pain
- Prescribed exercises and/or physiotherapy to maintain motion of the spine, strengthen abdominal and back muscles, and build endurance. All of these help to stabilize the spine. Some patients may be encouraged to try slow, progressive aerobic activity such as swimming or using exercise bicycles.
- A lumbar corset to provide some support and help the patient regain mobility. This approach is sometimes used for patients with weak abdominal muscles or older patients with multi-level degeneration. The corset should be used on a temporary basis only, as prolonged use may weaken the back and abdominal muscles.
- Acupuncture involves stimulating certain places on the skin by a variety of techniques. In most cases it does so by manipulating thin, solid, metallic needles that penetrate the skin.
In many cases, the conditions causing spinal stenosis cannot be cured by nonsurgical treatment, even though these measures may relieve pain for a period of time. The effectiveness of nonsurgical treatments, the extent of the patient's pain, and the patient's preferences may all factor into whether or not to have surgery.
Surgery might be considered immediately if a patient has numbness or weakness that interferes with walking or impairs bowel or bladder function.
The purpose of surgery is to relieve pressure on the nerves, as well as restore and maintain the alignment of the spine. This can be done by decompressive laminectomy, i.e. removal of the lamina (roof) of one or more vertebrae to create more space for the nerves.
If the affected spinal segment is also deemed to be unstable (e.g. spondylolisthesis or lateral subluxation in degenerative scoliosis) or responsible for a significant proportion of the patient's axial back pain, fusion may also be performed at the same setting.
Fusion often involves the use of the patient's own bone from the removed lamina or facet, supplemented by titanium pedicle screws. Various methods may be used to enhance fusion and strengthen unstable segments of the spine following decompression surgery. For example, one can use interbody cages placed in the intervertebral disc spaces after discectomy.
One advancement in the surgical fusion technique is the use of BMP (bone morphogenetic protein) to improve the fusion success rate, especially in patients with higher risks of nonunion - for example, diabetics, smokers, patients who have had multi-level surgeries, and revision surgeries.
The buzz words in spine surgery nowadays are non-fusion surgery and minimally invasive surgery. These techniques are now applicable in the surgical treatment of lumbar spinal stenosis in carefully selected patients.
Non-fusion surgery is possible with the use of dynamic devices (e.g. interspinous spacers) placed after decompression laminectomy in order to restrict - but not completely eliminate - spinal motion at the affected level. Minimally-invasive surgery is now possible with the use of specially designed ports and screw systems, with the added advantage of reduced hospital stay and an earlier return to work.