Lumbar spinal stenosis occurs mainly in older patients. It is a narrowing of the lumbar canal which generally occurs slowly leading to pressure on the nerves of the spine. This generally causes pain in the back and down the legs and causes progressive difficulty walking.
The stenosis is due to osteoarthritis of the spine. At the front of the spine are discs. At the back of the spinal canal are two facet joints, one on the left and one on the right. As patients age, the discs slowly collapse and tend to bulge posteriorly. The facet joints slowly enlarge. This in combination with thickening and buckling of the ligament that runs between the vertebrae causes progressive lumbar canal stenosis. Bone spurs form (osteophytes) which contribute to the narrowing. Occasionally, patients will develop a spondylolisthesis especially at the lowermost two levels in the spine, the L4-5 and the L5-S1 levels.
The most common symptom of lumbar canal stenosis is “neurogenic claudication”. This is painful cramping discomfort and/or weakness which arises in the back and radiates down either one or both legs. Symptoms are brought on by walking and prolonged standing. Patients often have no pain when sitting or lying down. In general, the distance the patients can walk i.e. the claudication distance, gradually reduces as the stenosis progresses. Patients will describe pain in the back and down the legs which causes them to stop walking and have to sit down. The pain generally resolves over 5-10 minutes and then the patients can start walking again. Patients may also report weakness, sensory disturbance and if severe, bladder and bowel dysfunction can occur. In general, the symptoms are slowly progressive. Often patients have minimal back pain.
The diagnosis of lumbar canal stenosis is made using a magnetic resonance imaging (MRI) scan. Once symptoms begin, they generally tend to relentlessly progress in severity. The claudication distance becomes shorter as the narrowing slowly progresses. Conservative treatments such as medication with analgesia, physical therapy and manipulative techniques may give short term relief. Cortisone injections generally do not alleviate symptoms as they only treat acute inflammation and in general, stenosis tends to progress with time. When symptoms become severe and persistent, surgical treatment is indicated.
The surgical procedure is minimally invasive decompression through a posterior lumbar incision of 2cm. The surgery is aimed at decompressing the spinal canal removing ligament and bone that is contributing to the compression. The surgery generally takes 1.5 hours and patients are in hospital 1-2 days. In general, symptoms of neurogenic claudication are completely alleviated and patients can return to normal activities.
Some patients i.e. around 10% will develop multilevel stenosis and may require surgery at more than one level. Once the stenosis has been decompressed, it generally does not reoccur. Occasionally patients with a high grade spondylolisthesis may require fusion of the vertebrae rater than simple decompression alone. This involves placing titanium screws into the vertebrae to ensure the spine remains stable.