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Low Back Pain Causes
What are common causes of lower back pain?
Common
causes of low back pain (lumbar backache) include
lumbar strain,
nerve irritation,
lumbar radiculopathy, bony encroachment, and conditions of
the bone and joints.
- Lumbar strain (acute, chronic)
A
lumbar strain is a stretch injury to the ligaments,
tendons, and/or muscles of the low back. The stretching
incident results in microscopic tears of varying degrees
in these tissues. Lumbar strain is considered one of the
most common
causes of low back pain. The injury can
occur because of overuse, improper use, or trauma.
Soft-tissue injury is commonly classified as "acute" if
it has been present for days to weeks. If the strain
lasts longer than three months, it is referred to as
"chronic."
Lumbar strain most often occurs in people in their 40s,
but it can happen at any age. The condition is
characterized by localized
discomfort in the low back
area with onset after an event that mechanically
stressed the lumbar tissues. The severity of the injury
ranges from mild to severe, depending on the degree of
strain and resulting spasm of the muscles of the low
back.
The diagnosis of lumbar strain is based on the history
of injury, the
location of the pain, and exclusion of
nervous system injury. Usually, X-ray testing is only
helpful to exclude bone abnormalities.
The treatment of lumbar strain consists of resting the
back (to avoid reinjury),
medications to relieve pain
and muscle spasm,
local heat applications, massage, and
eventual (after the acute episode resolves)
reconditioning exercises to strengthen the low back and
abdominal muscles. Initial treatment at home might
include heat application, acetaminophen (Tylenol) or
ibuprofen (Advil, Motrin), and avoiding reinjury and
heavy lifting. Long periods of inactivity in bed are no
longer recommended, as this treatment may actually slow
recovery. Spinal manipulation for periods of up to one
month has been found to be helpful in some patients who
do not have signs of nerve irritation. Future injury is
avoided by using back-protection techniques during
activities and support devices as needed at home or
work.
- Nerve irritation
The
nerves of the lumbar spine can be irritated by
mechanical pressure (impingement) by bone or other
tissues, or from disease, anywhere along their
paths -- from their roots at the spinal cord to
the skin surface. These conditions include
lumbar disc
disease (radiculopathy), bony encroachment, and
inflammation of the nerves caused by a viral infection
(shingles).
- Lumbar radiculopathy
Lumbar radiculopathy is nerve irritation that is caused
by damage to the discs between the vertebrae. Damage to
the disc occurs because of
degeneration ("wear and
tear") of the outer ring of the disc, traumatic injury,
or both. As a result, the central softer portion of the
disc can rupture (herniate) through the outer ring of
the disc and abut the spinal cord or its nerves as they
exit the bony spinal column. This rupture is what causes
the commonly recognized "sciatica" pain of a herniated
disc that shoots from the low back and buttock down the
leg.
Sciatica can be preceded by a history of localized
low-back aching or it can follow a "popping" sensation
and be accompanied by
numbness and tingling. The pain
commonly increases with movements at the waist and can
increase with coughing or sneezing. In more severe
instances, sciatica can be accompanied by
incontinence
of the bladder and/or bowels. The sciatica of lumbar
radiculopathy typically affects only one side of the
body, such as the left side or right side, and not both.
Lumbar radiculopathy is suspected based on the above
symptoms. Increased radiating pain when the lower
extremity is lifted supports the diagnosis. Nerve
testing (EMG/electromyogram and
NCV/nerve conduction velocity) of the lower
extremities can be used to detect nerve irritation. The
actual disc herniation can be detected with imaging
tests, such as CAT or
MRI scanning.
Treatment of lumbar radiculopathy ranges from medical
management to surgery. Medical management includes
patient education,
medications to relieve pain and
muscle spasms,
cortisone injection around the spinal
cord (epidural injection), physical therapy (heat,
massage by a therapist, ultrasound, electrical
stimulation), and rest (not strict bed rest but avoiding reinjury). With unrelenting pain, severe impairment of
function, or
incontinence (which can indicate spinal
cord irritation), surgery may be necessary. The
operation performed depends on the overall status of the
spine and the age and health of the patient. Procedures
include removal of the herniated disc with
laminotomy (a
small hole in the bone of the lumbar spine surrounding
the spinal cord),
laminectomy (removal of the bony
wall), by needle technique (percutaneous discectomy),
disc-dissolving procedures (chemonucleolysis), and
others.
- Bony encroachment
Any condition that results in movement or growth of the
vertebrae of the lumbar spine can limit the space
(encroachment) for the adjacent spinal cord and nerves.
Causes of bony encroachment of the spinal nerves include
foraminal narrowing (narrowing of the portal through
which the spinal nerve passes from the spinal column,
out of the spinal canal to the body, commonly as a
result of
arthritis),
spondylolisthesis (slippage of one
vertebra relative to another), and
spinal stenosis
(compression of the nerve roots or spinal cord by bony
spurs or other soft tissues in the spinal canal).
Spinal-nerve compression in these conditions can lead to
sciatica pain that radiates down the lower extremities.
Spinal stenosis can cause lower-extremity pains that
worsen with walking and are relieved by resting
(mimicking the pains of poor circulation). Treatment of
these afflictions varies, depending on their severity,
and ranges from rest to
surgical decompression by
removing the bone that is compressing the nervous
tissue.
- Bone and joint conditions
Bone and joint conditions that lead to low back pain
include those existing from birth (congenital), those
that result from wear and tear (degenerative) or injury,
and those that are due to inflammation of the joints
(arthritis).
Congenital bone conditions --
Congenital causes (existing from birth) of
low back
pain include
scoliosis and
spina bifida. Scoliosis
is a sideways (lateral) curvature of the spine that
can be caused when one lower extremity is shorter
than the other (functional scoliosis) or because of
an abnormal architecture of the spine (structural
scoliosis). Children who are significantly affected
by structural scoliosis may require treatment with
bracing and/or surgery to the spine. Adults
infrequently are treated surgically but often
benefit by support bracing.
Spina bifida is a birth defect in the bony vertebral
arch over the spinal canal, often with absence of
the spinous process. This birth defect most commonly
affects the
lowest lumbar vertebra
and the
top of
the sacrum. Occasionally, there are abnormal tufts
of hair on the skin of the involved area. Spina
bifida can be a minor bony abnormality without
symptoms. However, the condition can also be
accompanied by serious nervous abnormalities of the
lower extremities.
Degenerative bone and joint conditions
-- As we age, the water and protein content of the
body's cartilage changes. This change results in
weaker, thinner, and more fragile cartilage. Because
both the discs and the joints that stack the
vertebrae (facet joints) are partly composed of
cartilage, these areas are subject to
wear and tear
over time (degenerative changes). Degeneration of
the disc is called
spondylosis. Spondylosis can be
noted on X-rays of the spine as a narrowing of the
normal "disc space" between the vertebrae. It is the
deterioration of the disc tissue that predisposes
the disc to herniation and localized lumbar pain
("lumbago") in older patients. Degenerative
arthritis (osteoarthritis) of the facet joints is
also a cause of localized lumbar pain that can be
detected with plain X-ray testing. These causes of
degenerative back pain are usually treated
conservatively with intermittent heat, rest,
rehabilitative exercises, and
medications to relieve
pain, muscle spasm, and inflammation.
Injury to the bones and joints
-- Fractures (breakage of bone) of the lumbar spine
and sacrum bone most commonly affect elderly people
with
osteoporosis, especially those who have taken
long-term cortisone medication. For these
individuals, occasionally even minimal stresses on
the spine (such as bending to tie shoes) can lead to
bone fracture. In this setting, the vertebra can
collapse (vertebral compression fracture). The
fracture causes an immediate onset of severe
localized pain that can radiate around the waist in
a band-like fashion and is made intensely worse with
body motions. This pain generally does not radiate
down the lower extremities. Vertebral fractures in
younger patients occur only after severe trauma,
such as from motor-vehicle accidents or a convulsive
seizure.
In both younger and older patients, vertebral
fractures take weeks to heal with rest and pain
relievers.
Compression fractures of vertebrae
associated with
osteoporosis can also be treated
with a procedure called vertebroplasty, which can
help to reduce pain. In this procedure, a balloon is
inflated in the compressed vertebra, often returning
some of its lost height. Subsequently, a "cement" (methymethacrylate)
is injected into the balloon and remains to retain
the structure and height of the body of the
vertebra.
Arthritis -- The
spondyloarthropathies are inflammatory types of
arthritis that can affect the lower back and
sacroiliac joints. Examples of spondyloarthropathies
include reactive arthritis (Reiter's disease),
ankylosing spondylitis, psoriatic arthritis, and the
arthritis of inflammatory bowel disease. Each of
these diseases can lead to low back pain and
stiffness, which is typically worse in the morning.
These conditions usually begin in the second and
third decades of life. They are treated with
medications directed toward decreasing the
inflammation. Newer biologic medications have been
greatly successful in both quieting the disease and
stopping its progression.
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