Low Back Pain
What is Low Back Pain?
Vertebrae in the spinal column are separated from each other by small
cushions of cartilage known as intervertebral discs. Inside each disk is a
jelly-like substance called the nucleus pulposus, which is surrounded by a
fibrous structure. The disk is 80% water, which makes it very elastic. It
has no blood supply of its own, however, but relies on nearby blood vessels
to keep it nourished.
Each vertebra in the spine has a number of bony projections, known as
processes. The spinal and transverse processes attach to the muscles in the
back and act like little levers, allowing the spine to twist or bend. The
articular processes form the joints between the vertebrae themselves,
meeting together and interlocking at the facet joints.
Each vertebra and its processes surround and protect an arch-shaped central
opening. These arches, aligned to run down the spine, form the spinal canal,
which encloses the spinal cord-the central trunk of nerves that connects the
brain with the rest of the body. Each nerve root passes from the spinal
column to other parts of the body through small openings bounded on one side
by the disc and the other by the facets. When the spinal cord reaches the
lumbar region, it splits into four bundled strands of nerve roots called the
cauda equina (meaning horse-tail in Latin).
Back pain may be triggered by various problems that can occur along this
ridge of bone and disc. Injuries and small fractures can occur. As a person
ages, the discs thin; pressure on a weakened disk may cause it to rupture so
the nucleus pulposus protrudes out from the spinal column, a condition known
as a herniated disc. The facets can become misaligned or deteriorate. The
spinal canal itself can become narrowed, a condition called spinal stenosis.
If any of these conditions occur, the nerve roots passing between the discs
and facets may be stretched or pinched, causing pain.
The nerve most likely to cause trouble is the sciatic nerve; at some time,
up to 40% of people experience pain caused by compression of this nerve,
which branches from the nerve roots that descend off the spinal cord in the
lumbar and sacral areas. Each of the two branches of the sciatic nerve is
about as wide as a thumb and threads through the pelvis and deep into the
buttocks, then down the hip and along the back of the thigh to the foot. The
pain known as sciatica usually occurs on one side when a sciatic nerve has
been stretched or pinched, usually by a herniated disc, although spinal
stenosis or other vertebral abnormalities can also cause this pain. The
sensation of sciatica can vary widely-from a mild tingling to pain severe
enough to cause immobility. Some people experience sharp pain in one part of
the leg or hip and numbness in other parts. The pain increases after
prolonged standing or sitting and is aggravated by sneezing, coughing, or
laughing. If spinal stenosis is causing sciatica, patients may also
experience it after bending backwards or walking more than 50 to 100 yards.
Low back pain is usually defined as either acute or chronic. Physicians
diagnose low back pain as acute if it lasts less than a month and is not
caused by serious medical conditions. If the pain lasts over six months, it
is considered chronic low back pain; this constitutes only 1% to 5% of all
low back pain cases. Most cases clear up in a few days without medical
attention. A person should see a physician, however, under certain
circumstances: pain that lasts more than two weeks; very severe
pain-particularly if it awakens the person at night; pain that is increased
by lying down; pain accompanied by fever; weakness or numbness in legs,
feet, arms, or hands; an inability to control urination or defecation; and
neck pain or back pain in children.
What Causes Low Back Pain?
Abnormalities of the Spine
Experts now generally believe that bulging, or even protruding, discs may be normal and do not necessarily indicate serious back problems
requiring surgical procedures. One expert suggested that discs might even swell in response to
stress and then contract again. However, disc material that extrudes, that is, it balloons into the area
outside the vertebrae or is fragmented from the disc itself, most likely is a cause of pain.
Spinal stenosis, the narrowing of the spinal canal, is usually caused by bone
overgrowth, which occurs mostly in the elderly who have degenerative arthritis, but it can
sometimes be caused by other problems, including infection and birth defects.
Osteoporosis is a disease of the skeleton in which the amount of calcium present in
the bones slowly decreases to the point where the bones become fragile and prone to fracture.
Fractures of the hip, wrist, or forearm are usually caused by falls or accidents, but spinal fractures
can occur simply as a result of pressure that compresses the vertebrae together. Osteoporosis is a
major cause of disability and death in the elderly. Between 25% and 60% of women over 60 years
old develop spinal compression fractures. Early spinal compression fractures may go undetected for
a long time, but after a large percentage of calcium has been lost, the vertebrae in the spine start to
collapse, gradually causing a stooped posture called kyphosis, or commonly, a dowager's hump.
Although this is usually painless, patients may eventually lose as much as 6 inches in height. If the
vertebrae collapse suddenly, however, pain is often severe, particularly over the affected vertebrae,
but pain can also radiate around the area.
Osteoarthritis occurs in joints where cartilage is damaged, then destroyed; in reaction
to this destruction, the bones associated with the joints develop abnormalities. Unlike some other
types of arthritis, such as rheumatoid arthritis, osteoarthritis is not systemic-that is, it does not
spread through the entire body, but rather concentrates in one or several joints where deterioration
occurs. (Rheumatoid arthritis can damage the joints in the neck but rarely effects the lower back.)
Osteoarthritis affects joints differently depending on their location in the body. It is commonly
found in the joints of the fingers, feet, knees, hips, and spine and only rarely in the wrist, elbows,
shoulders, or jaw. When it affects the spine, osteoarthritis may damage the cartilage in the discs, the
moving joints of the spine, or both. In any case, the patient can experience pain, muscle spasms,
and diminished mobility. The nerves may become pinched, causing pain and, in advanced cases,
numbness and muscle weakness.
Ankylosing spondylitis is a chronic inflammation of the spine that may
gradually result in a fusion of the spine causing the patient to stoop over. It can be quite mild,
however, and it rarely effects a person's ability to work. Symptoms include a slow development of
back discomfort, with pain lasting for more than three months. The back is usually stiff in the
morning; pain improves with exercise. It can be diagnosed using x-rays or scans. Ankylosing
spondylitis occurs mostly in young Caucasians in their mid-twenties. It was thought that the disease
affected mostly men, but about 30% of the cases are in women. It is probably hereditary; many
patients with ankylosing spondylitis have a protein on their cells called tissue-type HLA-B27.
About 20% of people with inflammatory bowel disease and about 20% of people with psoriasis
develop a form of ankylosing spondylitis.
Causes of back pain in young people
Who develops low back pain?
How is low back pain diagnosed?
How is low back pain treated?
General Guidelines for Treatment of Acute Low Back Pain
Bed rest is usually not needed; if it is, most experts recommend staying in bed no longer than a
couple of days. A recent study reported, however, that even two days may be too long. In the
study, people who avoided bed rest altogether and simply tried to resume normal activities, without
strain or stretching exercises, recovered more quickly than those who were in bed for even as short
a period as two days. Those who are in bed a week or longer do even worse. Long-term bed rest
results in loss of muscle tone and bone strength, increases susceptibility to blood clots, and
produces depression and lethargy. Traction probably has no benefit and may be harmful.
The speed at which patients resume activity can be guided by their level of pain. People usually
recover from a strained back or a mildly herniated disc in a few of days. It may take, however, as
long as six weeks to fully recover from back pain, particularly if it is due to sciatica. At that time, if
the pain has not been relieved, other measures may be needed.
Acetaminophen (Tylenol, Anacin-3, Panadal, Phenaphen, Valadol, and other brands) is the
over-the-counter alternative to NSAIDs. One study reported that acetaminophen was as effective as
an anti-inflammatory drug in relieving chronic pain. Still, many patients report less pain relief with
acetaminophen than with NSAIDs. Acetaminophen can be used alone or in combination with
NSAIDs with some success. Liver and kidney damage, however, are potential serious side effects
of acetaminophen. A recent study showed that taking one tablet daily for a year doubled the risk of
kidney disease, and that amounts as low as 4 to 10 grams daily increased the risk of liver damage in
people who hadn't eaten much for prolonged periods due to illness. Experts recommend taking no
more than 8 extra-strength tablets each day.
Steroids. A one-time injection of a steroid into the area around the spinal column may be an
effective way to short-cut the back pain until the body heals itself, although studies are conflicting.
It is not a cure; steroids are generally useful for reducing inflammation. Two reviews of studies
found that use of steroids had no benefit, but other recent studies support this treatment, finding it
more beneficial than the use of a local anesthetic.
Other Medications. Although physicians may prescribe muscle relaxants such as cyclobenzaprine
(Flexeril), some experts believe that relaxing muscle spasm may actually be harmful, because the
tensed back muscles may be serving a purpose by protecting the damaged disk or vertebrae.
Injections of local anesthetics are occasionally used and can be helpful for temporary relief of severe
pain, but experts now strongly advise against heavy-duty prescription pain killers, such as
morphine and codeine, which they believe do more harm than good.
Exercise appears to be the best approach in treating chronic low back pain. In a study of patients
who had suffered back pain for an average of 18 months, those who were assigned 8 one-hour
exercise sessions over four weeks improved in nearly every area, including reduced pain and
increased capacity, compared to the patients who did not exercise. Another study of 250 men and
women found the same results. Swimming, bicycling, and walking are all good exercises that can
strengthen muscles in the abdomen and back without over straining the back. People vulnerable to
back pain should avoid exercises or activities that put undue stress on the lower back or require
sudden movements, such as football, rowing, ballet, and weight lifting. Jogging is usually not
recommended, at least not initially. Traditional standard sit-ups can be harmful, but bent-knee sit
ups can build stomach muscles without stress to the lower back.
Laminectomy is an operation that cuts away a piece of vertebrae and removes
damaged parts of the disk. If bone growth is causing the problem, as in spinal stenosis, the surgeon
will shave away the bone in order to decompress the nerve. Laminectomy requires general
anesthesia and a two or three day hospital stay. Recuperation takes up to six weeks. Although it
often brings immediate relief from pain, there are small risks to the operation and it is not always
successful. Some recurrence of back pain and sciatica occurs in half to two-thirds of postoperative
Automated percutaneous discectomy (APD) requires the
insertion of a thin tube into the diseased disc. The tube has a device at the tip that cuts away some of
the nucleus pulposes and a vacuum that then sucks this gelatinous matter out, relieving pressure on
the nerve. Lasers may be used for this procedure, although recovery takes longer in such cases. The
disadvantage to this procedure is that surgeons cannot observe the nerve root itself, so they cannot
tell if the fragments removed are the source of the trouble, nor can they locate and remove any
matter that has gone beyond the disk and entered the spinal canal.
Patients best suited for this procedure appear to be those whose pain has lasted less than a year and
who are unable to undergo more invasive procedures.
For herniated discs not treatable by other methods, the
procedure chemonucleolysis (CNL) is effective in some cases. It is not warranted for any other type
of low back problem. CNL still requires general anaesthesia and a brief hospital stay, but it is less
traumatic than laminectomy, and patients may be able to return to work sooner. It is somewhat less
effective than discectomy. The physician injects the herniated disk with
chymopapain, an enzyme
made from the papaya. Chymopapain is a common ingredient in meat tenderizers and it softens the
nucleus purposis-the disc's gelatinous filling, thus reducing the bulge and relieving the pressure on
the sciatic nerve. It may take days or even months for the enzyme to relieve the pain completely, but
in 17 out of 20 studies, CNL was found ultimately to be as beneficial as
laminectomy. In one study
it relieved pain in 75% of patients. Risks include severe allergic reactions to
occur in about 1% of people, and nerve damage if the enzyme leaks out of the disc.
Transcutaneous Electric Nerve Stimulation
How is low back pain prevented?
Sitting puts the most pressure on the back, and driving for long periods in a vehicle increases the
stress. Chairs should either have straight backs or low-back support. If possible, chairs should
swivel to avoid twisting at the waist, have arm rests, and adjustable backs. While sitting, the knees
should be a little higher than the hip, so a low stool or hassock is useful to put the feet on. When
driving, move the seat as far forward as possible to avoid bending forward. A small pillow or rolled
towel behind the back helps relieve pressure while either sitting or driving.
Be sure to have a firm mattress. If the mattress is too soft, a 1/4-inch plywood board can be put
between the mattress and box spring. On the other hand, some people have experienced morning
back ache from a mattress that is too hard. The back is the best guide.
Although exercise is important for recovery from back pain, there are no studies proving that exercise prevents back pain in the first place. Many experts believe, however, that by strengthening the muscles in the trunk, the spine is better protected against injury. Generally, preventive exercise objectives include abdominal strengthening, increasing lower back mobility, hip flexibility, flexibility of hamstring muscles and tendons (those at the back of the thigh), and back muscle strength and endurance. Exercises in which the lower back is under pressure, such as leg lifts done in a prone (face-down) position, should be avoided until the back muscles are well-toned. Straight leg sit-ups and leg curls using exercise equipment should also be avoided unless back muscles are well-strengthened.
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