Low back pain is a common complaint, with an estimated 70-85% of the adult population reported to experience this problem at some point during their lifetime.
While the source of back pain - incuding pain radiating down from the back into the buttocks and lower extremities - can be difficult to diagnose, there are a number of signs and symptoms that indicate the presence of lumbar spine stenosis, literally, a narrowing of the spinal canal in the lower portion of the back.
These symptoms are generally associated with a fatigue or discomfort felt in the buttocks, thighs, and legs bilaterally (on both sides of the body). This fatigue is made worse by walking or standing and is often relieved by sitting to rest. Patients often complain of decreased ability to walk distances secondary to their fatigue or discomfort.
MRI (sagittal view) of normal spine
Viewed from the side, the spine appears as alternating layers of vertebrae (bones that form a ring-like structure) and disks (soft spongy structures that provide cushioning between the vertebrae and contribute to mobility). Together, the vertebrae and disks form a column and a passageway through which the spinal cord (which houses a bundle of nerves) passes from the brain to the base of the spine.
Viewed on a cross-section, one sees a more complex structure, which can be regarded as approximating that of a house.
Diagram of "House" analogy
Most frequently, narrowing or stenosis within that structure may occur as the culmination of:
MRI (sagittal view) of lumbar spinal stenosis
Trauma to the spine can also result in stenosis.
In addition to the bony structures described above, there are soft tissues present in the spine, including ligaments and fat. Inflammation of these tissues can contribute to the problem.
Illustration of cross-section of spine.
In addition to a narrowing in the central canal of the spine, patients may have narrowing in the foramen, an opening (much like the window of the "house" that has been described) through which nerve roots extend on either side of the spine. Finally, narrowing may occur in the lateral recess of the spine. Patients with stenosis may have any one or more affected areas.
Illustration of spine vertebra
Some people have congenital stenosis, a distinct condition from that which is discussed here. In these individuals, the "walls" of the "house" are abnormally short at birth and through development, thereby bringing pressure to bear on the spinal cord. Pain and other symptoms of this condition are usually manifest by the time the individual reaches young adulthood.
The primary symptom of stenosis at any site is pain and fatigue resulting from pressure on the spinal cord or nerves. People with stenosis of the central canal report pain that waxes and wanes, usually in the lower back, lower extremities, or the buttocks, that is worsened by walking or extension of the spine, and relieved when they sit to rest or when they lean forward.
While the actual site of stenosis is in the spine itself, pressure on the nerves is responsible for the referred pain in the buttocks or legs. The pain from foraminal or lateral recess stenosis can mimic that of sciatica or disc herniations.
Unfortunately, stenosis is a degenerative and chronic disease. In more advanced cases, patients may develop cauda equina syndrome. Named for the appearance of the nerve roots (which extend out at the base of the spine in a group of strands resembling a horses tail), this condition is characterized by urinary or bowel incontinence; saddle anesthesia, numbness or tingling at the inner parts of thighs near the genitals; and motor weakness.
To diagnose stenosis, the orthopedic surgeon takes a detailed history and conducts a physical examination and evaluates images obtained through either magnetic resonance imaging (MRI) or computed tomography (CT) with a myelogram.
In the latter procedure, a contrast material is injected into the affected area to show an outline of the nerve or nerves that are affected as well as the structures that are pressing on them. The orthopaedic surgeon rules out the presence of vascular caudication, a condition that involves poor arterial circulation and shares some symptoms in common with stenosis of the lumbar spine.
He or she also does a thorough evaluation to determine whether other orthopedic conditions are present, such as osteoarthritis of the hip, that may be causing stenosis-like symptoms, or may also require treatment along with stenosis.
Treatment for lumbar spine stenosis begins with conservative measures which may include physical therapy to correct the forward-leaning posture many people with stenosis adopt in order to alleviate pressure on the nerves, use of anti-inflammatory medications, and the application of ice, heat, ultrasound or electrical stimulation to the affected area.
While the space within the spine cannot be expanded by these means, reducing inflammation, and thereby decreasing the pressure on the nerves, can offer pain relief. Braces are not typically used to treat stenosis unless instability is present. Older patients who are not surgical candidates may benefit from injections; however, advanced age alone is not a contraindication to surgery.
If these measures do not provide adequate relief, patients may be given a steroid (a potent anti-inflammatory agent) injection directly into the inflamed area to see if that relieves pressure. Images obtained by MRI or CT myelogram guide the placement of these injections.
Response to this treatment is variable. Sometimes pain relief is significant and long lasting. Other patients derive only transient pain relief, and may or may not respond to a repeat injection. In order to minimize the side effects that can accompany treatment with steroids, no more than three injections be given in the course of a year. At Hospital for Special Surgery (HSS), steroid injections are usually administered by physiatrists (physicians who specialize in rehabilitation medicine) or pain management specialists.
Individuals who experience transient pain relief may be candidates for surgical intervention, since this response confirms that stenosis is at least part of the patient's problem. Surgery is only considered after other treatment options have been exhausted.
As with non-surgical treatment, the goal of surgical intervention is to remove the pressure on the nerves of the spinal cord and to restore mobility that has been lost owing to pain and fatigue. Usually this is achieved by doing a decompressive laminectomy (removal of that portion of the vertebra that forms the "roof" of the house-like structure of the spine.) In addition, the orthopaedic surgeon may remove any bone spurs that are present, as well as any soft tissue that is putting pressure on the spinal cord. In doing so, the space through which the spinal cord passes is "opened up" and the pressure on the nerves is eliminated.
Although in some cases, the disease is focal, that is, affecting just one or two levels of the spine, sometimes it is more widespread, extending the entire length of the lumbar spine to the sacrum. Depending on the extent of the area affected, patients may require fusion of the vertebrae in order to maintain stability of the spine after the laminectomy is performed.
Illustration of lumbar spine to sacrum.
Patients who undergo decompressive surgery usually remain in the hospital for a period of 3 to 5 days. Physical therapy is initiated as soon as possible with an early focus on walking, followed by a program of strengthening and stabilizing for the muscles around the spine. The patient must avoid any back bending, twisting, and lifting for about three months following surgery.
Overall, the success rate for surgical treatment of stenosis at HSS is about 85%, with varying degrees of improvement achieved among cases. "Even if we can't get the patient back to all the physical activities he or she once enjoyed, we can often get them back to performing activities of daily living, without discomfort," says Federico P. Girardi, MD, an associate attending orthopedic surgeon at HSS.
In addition to offering pain relief, treatment of stenosis confers a psychological benefit as mobility is restored.
Since the relatively recent inception of spine surgery as a sub-specialty of orthopaedics, Hospital for Special Surgery (HSS) has been committed to the development of research and clinical expertise in this area of medicine. Today, HSS offers patients the benefit of a highly specialized team of physicians, nurses, anesthesiologists, and physical therapists whose primary focus is the treatment of spinal disorders.