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Back pain is pain felt in the back. It may be classified based on the segment affectedas

neck pain (cervical),

middle back pain (thoracic),

lower back pain (lumbar) or

coccydynia (tailbone or sacral pain).

The lumbar area is the most common area affected. An episode of back pain may be acute, subacute or chronic depending on the duration. The pain may be characterized as a dull ache, shooting or piercing pain or a burning sensation. Discomfort can radiate to the arms and hands as well as the legs or feet, and may include numbness or weakness in the legs and arms.

The majority of back pain is nonspecific and idiopathic. Common underlying mechanisms include degenerative or traumatic changes to the discs and facet joints, which can then cause secondary pain in the muscles and nerves and referred pain to the bones, joints and extremities. Diseases and inflammation of the gallbladder, pancreas, aorta and kidneys may also cause referred pain in the back.Tumors of the vertebrae, neural tissues and adjacent structures can also manifest as back pain.

Back pain is common; approximately nine of ten adults experience it at some point in their lives, and five of ten working adults experience back pain each year.Some estimate that as many of 95% of people will experience back pain at some point in their lifetime.It is the most common cause of chronic pain and is a major contributor to missed work and disability. For most individuals, back pain is self-limiting. Most people with back pain do not experience chronic severe pain but rather persistent or intermittent pain that is mild or moderate.In most cases of herniated disks and stenosis, rest, injections or surgery have similar general pain-resolution outcomes on average after one year. In the United States, acute low back pain is the fifth most common reason for physician visits and causes 40% of missed work days. It is the single leading cause of disability worldwide.. 

Classification

Back pain is classified in terms of duration of symptoms.

  1. Acute back pain lasts <6 weeks
  2. Subacute back pain lasts between 6 and 12 weeks.
  3. Chronic back pain lasts for greater than 12 weeks.


Causes

There are many causes of back pain, including blood vessels, internal organs, infections, mechanical and autoimmune causes. Approximately 90 percent of people with back pain are diagnosed with nonspecific, idiopathic acute pain with no identifiable underlying pathology. In approximately 10 percent of people, a cause can be identified through diagnostic imaging. Fewer than two percent of cases are attributed to secondary factors, with metastatic cancers and serious infections, such as spinal osteomyelitis and epidural abscesses, accounting for approximately one percent.


Common causes

Cause

% of people with back pain

Nonspecific

90%

Vertebral compression fracture

4%

Metastatic cancer

0.7%

Infection

0.01%

Cauda equina

0.04%

Non Specific

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In as many as 90 percent of cases, no physiological causes or abnormalities on diagnostic tests can be found. Nonspecific back pain can result from back strain or sprains, which can cause peripheral injury to muscle or ligaments. Many patients cannot identify the events or activities that may have caused the strain. The pain can present acutely but in some cases can persist, leading to chronic pain.

Chronic back pain in people with otherwise normal scans can result from central sensitization, in which an initial injury causes a longer-lasting state of heightened sensitivity to pain. This persistent state maintains pain even after the initial injury has healed. Treatment of sensitization may involve low doses of antidepressants and directed rehabilitation such as physical therapy. 

Spinal disc disease

Spinal disc disease occurs when the nucleus pulposus, a gel-like material in the inner core of the vertebral disc, ruptures. Rupturing of the nucleus pulposus can lead to compression of nerve roots. Symptoms may be unilateral or bilateral, and correlate to the region of the spine affected. The most common region for spinal disk disease is at L4–L5 or L5–S1. The risk for lumbar disc disease is increased in overweight individuals because of the increased compressive force on the nucleus pulposus, and is twice as likely to occur in men. A 2002 study found that lifestyle factors such as night-shift work and lack of physical activity can also increase the risk of lumbar disc disease.