Causes of low back pain

 

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Non-specific low back pain or lumbago (pron.: /lʌmˈbeɪɡoʊ/) is a common musculoskeletal disorder affecting 80% of people at some point in their lives. In the United States it is the most common cause of job-related disability, a leading contributor to missed work, and the second most common neurological ailment — only headache is more common.[1] It can be either acute, subacute or chronic in duration. With conservative measures, the symptoms of low back pain typically show significant improvement within a few weeks from onset.

 

 
 
 
Contents
  • 1 Classification
  • 2 Cause
  • 3 Pathophysiology
    • 3.1 Pain sensation and perception
    • 3.2 Back structures
  • 4 Diagnostic approach
    • 4.1 Imaging
    • 4.2 Risks of imaging
  • 5 Prevention
  • 6 Management
    • 6.1 Acute pain
      • 6.1.1 Physical therapy
      • 6.1.2 Medications
      • 6.1.3 Manual therapies
    • 6.2 Chronic pain
      • 6.2.1 Exercise
      • 6.2.2 Medications
      • 6.2.3 Manual therapies
      • 6.2.4 Surgery
  • 7 Prognosis
  • 8 Epidemiology
  • 9 History
  • 10 Economics
  • 11 Women
  • 12 References
  • 13 External links

Classification

Lower back pain may be classified by the duration of symptoms as acute, subacute and chronic. Within these classifications, there is no agreement across medical organizations for the specific duration of symptoms, but generally pain lasting less than six weeks is classified as acute, pain lasting six to 12 weeks is subacute, and more than 12 weeks is chronic.[2]

Cause

The majority of lower back pain is referred to as non specific low back pain and does not have a definitive cause.[3] It is believed to stem from benign musculoskeletal problems such as muscle or soft tissues sprain or strains.[1] This is particularly true when the pain arose suddenly during physical loading of the back, with the pain lateral to the spine. The full differential diagnosis includes many other less common conditions.

  • Mechanical:
    • Apophyseal osteoarthritis
    • Diffuse idiopathic skeletal hyperostosis
    • Degenerative discs
    • Scheuermann's kyphosis
    • Spinal disc herniation ("slipped disc")
    • Thoracic or lumbar spinal stenosis
    • Spondylolisthesis and other congenital abnormalities
    • Fractures
    • Sacroiliac joint dysfunction
    • Leg length difference
    • Restricted hip motion
    • Misaligned pelvis - pelvic obliquity, anteversion or retroversion           
    • Abnormal foot pronation
  • Inflammatory:
    • Seronegative spondylarthritides (e.g. ankylosing spondylitis)
    • Rheumatoid arthritis
    • Infection - epidural abscess or osteomyelitis
    • Sacroiliitis
  • Neoplastic:
    • Bone tumors (primary or metastatic)
    • Intradural spinal tumors
  • Metabolic:
    • Osteoporotic fractures
    • Osteomalacia
    • Ochronosis
    • Chondrocalcinosis
  • Psychosomatic
    • Tension myositis syndrome
  • Paget's disease
  • Referred pain:
    • Pelvic/abdominal disease
    • Prostate Cancer
    • Posture
  • Oxygen deprivation

Pathophysiology

 
The lumbar region in regards to the rest of the spine.
 
The nerve and bone components of the vertebrae.

Pain sensation and perception

In general, pain is an unpleasant feeling in response to stimuli that have the potential to damage the body's tissues (noxious stimuli). There are four fundamental steps in the process of pain perception: transduction, transmission, perception and modulation. The process starts when the painful event stimulates the endings of the pain-sensing nerve cells (nociceptors). A nociceptor converts the stimulus into an electrical signal by transduction. Several different types of nerve fibers carry out the transmission of the electrical signal from the transducing nociceptor to the dorsal horn of the spinal cord, from there to the brain stem, and then from the brain stem to the various parts of the brain such as the thalamus and the limbic system, where pain signals are processed and given context in the process of pain perception. Through modulation, the brain can then modify the sending of further pain impulses by signaling the release of neurotransmitters that either inhibit them (for example, serotonin and endorphins) or excite them.[5]

Back structures

The lumbar region (or lower back region) is made up of five vertebrae (L1-L5). In between these vertebrae lie fibrocartilage discs (intervertebral discs), which act as cushions, preventing the vertebrae from rubbing together while at the same time protecting the spinal cord. Nerves stem from the spinal cord through foramina within the vertebrae, providing muscles with sensations and motor associated messages. Stability of the spine is provided through ligaments and muscles of the back, lower back and abdomen. Small joints which prevent, as well as direct, motion of the spine are called facet joints (zygapophysial joints).[6]

 

 

 

 

 

Causes of lower back pain are varied. Most cases are believed to be due to a sprain or strain in the muscles and soft tissues of the back.[1] Overactivity of the muscles of the back can lead to an injured or torn ligament in the back which in turn leads to pain. An injury can also occur to one of the intervertebral discs (disc tear, disc herniation). Due to aging, discs begin to diminish and shrink in size, resulting in vertebrae and facet joints rubbing against one another. Ligament and joint functionality also diminishes as one ages, leading to spondylolisthesis, which causes the vertebrae to move much more than they should. Pain is also generated through lumbar spinal stenosis, sciatica and scoliosis. At the lowest end of the spine, some patients may have tailbone pain (also called coccyx pain or coccydynia). Others may have pain from their sacroiliac joint, where the spinal column attaches to the pelvis, called sacroiliac joint dysfunction which may be responsible for 22.6% of low back pain.[7] Physical causes may include osteoarthritis, rheumatoid arthritis, degeneration of the discs between the vertebrae or a spinal disc herniation, a vertebral fracture (such as from osteoporosis), or rarely, an infection or tumor.[8]

In the vast majority of cases, no noteworthy or serious cause is ever identified. If the pain resolves after a few weeks, intensive testing is not indicated.[9][unreliable source]

 

 

 

 

Diagnostic approach

For correct diagnosis, non-specific low back pain must be differentiated from radiculopathy and serious spinal problems such as a tumor, infection or spinal fracture. Certain signs, termed "red flags," may indicate a more serious condition, and prompt a more extensive investigation using diagnostic imaging or laboratory testing; even so, most individuals seeking treatment for acute low back pain have one or more red flags but no serious underlying problem. With other causes ruled out, people with non-specific low back pain typically are treated symptomatically, without exact determination of the underlying cause.[2][3]

Imaging

X-rays, CT or MRI scans are not required in lower back pain except in the cases where "red flags" are present.[11] If the pain is of a long duration X-rays may increase patient satisfaction.[12] However routine imaging may be harmful to a person's health and more imaging is associated with higher rates of surgery but no resultant benefit.[13] From 1994 to 2006, in the United States MRI scans of the lumbar region increased by more than 300%.[14]

Risks of imaging

Complaints of lower back pain are one of the most common reasons why people visit doctors.[15] Although many patients and doctors try to find the cause of the pain with imaging tests such as an X-ray, CT scan, or MRI, in most cases these tests are not necessary.[15] Most people with lower-back pain feel better after a month regardless of whether they get imaging.[15] Fewer than 1% of imaging tests identify the cause of a problem.[15]

The negative effects of imaging include the following:

  • The tests rarely result in a faster or better recovery[15]
  • X-rays and CT scans involve exposure to potentially harmful radiation
  • They can detect harmless abnormalities which encourage the patient to request further unnecessary testing or to worry[15]
  • Testing for acute back pain often leads to unnecessary surgery[15]
  • The tests are expensive[15]

Medical societies do not recommend imaging tests for lower back pain within a few weeks of the onset of pain as the pain is likely to subside.[15]

Prevention

Exercise is effective in preventing recurrence of non-acute pain, however in the treatment of acute episodes results are mixed.[16] Proper lifting techniques may be useful.[17] Lumbar support does not appear effective.[18] Firm mattresses have demonstrated less effectiveness in preventing back pain than medium-firm mattresses.[19]

Cigarette smoking impacts the success and proper healing of spinal fusion surgery in patients who undergo cervical fusion; rates of nonunion are significantly greater for smokers than for nonsmokers.[20] Smoke and nicotine accelerate spine deterioration, reduce blood flow to the lower spine, and cause discs to degenerate.[21]

Management Acute pain

For acute cases that are not debilitating, the treatment goal is to restore normal function and return the individual to work while minimizing pain. The condition is normally not serious, most often resolves without significant intervention, and recovery is aided by attempting to resume normal activity as soon as possible within the limits of pain; providing afflicted individuals with coping skills through reassurance of these facts is effective in hastening recovery.[3] Low back pain may be best treated with conservative self-care,[22] including: application of heat or cold,[23][24] and continued activity within the limits of the pain.[2][9][unreliable source]

Engaging in physical activity within the limits of pain aids recovery. Prolonged bed rest (more than 2 days) is considered counterproductive.[25] Even with cases of severe pain, some activity is preferred to prolonged sitting or lying down - excluding movements that would further strain the back.[9][unreliable source] Structured exercise in acute low back pain has demonstrated neither improvement nor harm.[16] Heat application may have a modest benefit. The evidence for cold therapy however is limited.[23]

Physical therapy

Physical therapy can include heat, ice, massage, ultrasound, and electrical stimulation. Active therapies can consist of stretching, strengthening and aerobic exercises. Exercising to restore motion and strength to your lower back can be very helpful in relieving pain and preventing future episodes of low back pain.[26]Treatment according to McKenzie method is somewhat effective for acute low back pain, but not for chronic low-back pain.[27] The benefit in the short term does not appear clinically significant.[3]

Medications

Short term use of pain and anti-inflammatory medications, such as NSAIDs or acetaminophen may help relieve the symptoms of lower back pain.[25][28] NSAIDs are slightly effective for short-term symptomatic relief in patients with acute and chronic low-back pain without sciatica.[29] Muscle relaxants for acute and chronic pain have some benefit,[25][28] and are more effective in relieving pain and spasms when used in combination with NSAIDs.[30] Oral steroids have not been shown to be useful.[3]

Manual therapies

It is not known if chiropractic care improves clinical outcomes in those with lower back pain more or less than other treatments.[31] A 2012 Cochrane review found that spinal manipulation was no more effective than either inert interventions, sham manipulation, or other treatments and adding it to other treatment does not appear to increase the benefit.[32] A 2010 systematic review found that most studies suggest SM achieves equal or superior improvement in pain and function when compared with other commonly used interventions for short, intermediate, and long-term follow-up.[33] In 2007 the American College of Physicians and the American Pain Society jointly recommended that it be considered for people who do not improve with self care options.[22] Acupuncture and massage is without substantial benefit.[3]

Chronic pain

Low back pain is more likely to be persistent among people who previously required time off from work because of low back pain, those who expect passive treatments to help, those who believe that back pain is harmful or disabling or fear that any movement whatever will increase their pain, and people who have depression or anxiety.[9][unreliable source] A number of factors predict disability from back pain and include those who have poor coping behaviors or who fear activity are about 2.5 times as likely to have poor outcomes at a year.[34] Intensive multidisciplinary treatment programs may help subacute[25] or chronic[28] low back pain.[9][unreliable source] Behavioral therapy may be useful.[28]

Exercise

Exercise therapy appears to be slightly effective at reducing pain and improving function in the treatment of chronic low back pain.[35] Compared to usual care, exercise therapy improved post-treatment pain intensity and disability, and long-term function.[36] Exercise programmes are effective for chronic LBP up to 6 months after treatment cessation, evidenced by pain score reduction and reoccurrence rates.[37] There is no evidence that one particular type of exercise therapy is clearly more effective than others.[38] The Alexander technique appears useful for chronic back pain.

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