Acute and sub-acute back pain

Contributed by Dr Mark Ritchie, GPSI in pain management, Morriston, Swansea

Section 1: Epidemiology and aetiology
Back pain can be sinister or non-sinister; generally most of what is seen in general practice is non-sinister.

Back pain can be classified as acute if lasting less than six weeks; sub-acute if lasting 6-12 weeks; and chronic if lasting more than 12 weeks.

Slipped vertebrae

Chronic back pain and the associated disability often become dissociated from the original physical problem, and will be covered in a separate article in next week's issue.

Depending on the source, the annual incidence of new back pain is reported as about 5 per cent of the population.

Economic consequences
In the UK, back and sciatic pain is the most likely cause for time off work; some 300,000 people will be off work with back pain on any given day.

In 1994, it was estimated that 52 million work days were lost and that the costs to the NHS in that year were £481 million. Meanwhile benefits costs were estimated at £1.4 billion and lost production at £3.8 billion.1

Back pain most commonly affects adults aged 25-55 years. In the UK the incidence in middle-aged women is higher, which may be due in part to osteoporosis.

Prevalence
Reports on prevalence in Europe vary from 13-44 per cent at any time with a lifetime prevalence of 59-90 per cent. This makes back pain a major health and socio-economic burden.

In primary care, approximately 85-95 per cent of low back pain will be mechanical, and 4-5 per cent due to nerve root irritation from disc prolapse or vertebral compression fractures (mainly in older people and those with osteoporosis).

Ankylosing spondylitis and spinal infections have a prevalence of less than 1 per cent and the prevalence of prolapsed inter-vertebral disc is low - between 1 and 3 per cent.

Up to 3 per cent may have spondylolisthesis (the slipping of one vertebra over another).

Less than 1 per cent of back pain is due to more sinister pathologies including cancer (about 0.7 per cent - generally unlikely unless the patient has previously had cancer), and spinal infections (0.01 per cent).2

Aetiology
Risk factors for developing back pain include poor posture, incorrect and heavy lifting, heavy physical work, twisting and awkward movements, and whole body vibration due to machine usage or driving a large vehicle.

Psychosocial risk factors include anxiety, depression, and mental stress at work.

Identification of the exact source of pain is not always possible.

The aetiologies can be subdivided into three groups: mechanical, systemic and referred. By far, the most common cause is mechanical (97 per cent).2

Pain may arise from almost any structure in the lumbar spine, but particularly the intervertebral discs, vertebrae, facet joints, fascia, ligaments and/or muscles.

Symptoms, pathology and radiological appearances are poorly correlated.

Possible causes of lower back pain
  • Poor posture
  • Faulty ergonomics
  • Muscle imbalance
  • Faulty lifting techniques
  • Poor abdominal wall function
  • Visceral-somato reflex
  • Spinal fractures
  • Spinal tumours
  • Spinal infections
  • Degenerative disease

Section 2: Diagnosis

The main aim of assessment is to distinguish between benign mechanical back pain and sinister causes of back pain.

European diagnostic guidelines3 suggest that the following are essential in diagnosis:

  • A detailed history and brief examination.
  • Diagnostic triage at first assessment including red flag analysis to exclude sinister causes of back pain.
  • Rule out serious pathology by assessing presence of any of red flags (see box). Red flag symptoms may indicate possible serious spinal pathology or nerve root syndrome and further neurological assessment is necessary.
  • Psychosocial factors (yellow flags) need to be recorded in detail as these can lead to chronicity (see box). If yellow flags are found they need to be monitored regularly and dealt with early.
  • Routine imaging tests such as X-rays, CT and MRI are not usually indicated.
  • Patients not improving or worsening in a few weeks need early review.
Red flag symptoms in acute back pain
Red flags indicative of cauda equina syndrome
- Saddle anaesthesia
- Loss of bladder/bowel sphincter tone
- Major motor weakness

Red flags suggesting spinal fracture
- Sudden onset, severe central back pain, relieved by lying down
- Major trauma
- Minor trauma or strenuous lifting in osteoporosis patients
- Structural spinal deformity

Red flags suggesting cancer or infection
- Onset of back pain in a patient over 50 years, or under 20 years old
- History of cancer
- Sytemic features - fever, chills, or unexplained weight loss
- IV drug abuse
- Immune suppression
- Pain that remains when supine, aching night-time pain, disturbing
sleep; and thoracic pain (which also suggests aortic aneurysm)

Yellow flag symptoms suggesting psychosocial factors
- Incorrect beliefs i.e. activity, exercise, work and pain itself are
harmful
- Sickness behaviour, such as extended rest
- Social withdrawal and lack of social support
- Depression, anxiety, stress
- Work dissatisfaction
- Gain, i.e. compensation claim/benefits
- Extended time off work, i.e. more than six weeks
- Overprotective family
- Low level of active participation in treatment

Section 3: Management

European guidelines3 and clinical experience lead to the following approach.

Patients need clear information and reassurance at an early stage. Information leaflets are invaluable.

Patients should be advised to stay active and continue normal daily activities including work where possible. Bed rest has not been shown to be effective.4

Pharmacotherapy
Paracetamol is an ideal first-line analgesic. NSAIDs can reduce soft tissue inflammation that may be contributing to back pain as well as providing analgesia.

The evidence from trials of more than 11,000 patients showed that NSAIDs can provide short-term relief from back pain, that no particular NSAID is more effective than another, and that they have similar efficacy to other analgesics such as paracetamol.5

If stronger analgesia is needed weak or strong opiates are useful. Their use will depend on the analgesic requirements of the patient as judged by the clinician and is limited by their side-effects, such as constipation, nausea and respiratory depression.

Strong opiates have the potential for tolerance and addiction, so they should be used for as short a time as possible.

Tricyclic antidepressants are advised by NICE in sub-acute and chronic back pain but not specifically in acute back pain.6

A muscle relaxant can be used first line or if initial treatment fails. They can cause side-effects such as drowsiness or dizziness and so should be limited to short-term use.

Other treatments
A systematic review of 29 studies showed that spinal manipulation can help to reduce acute back pain but the duration of effect is unknown as the studies were short.7

NICE have suggested manual therapy (spinal manipulation, mobilisation or massage) as a treatment option,6 although there is no strong evidence for the efficacy of physiotherapy in acute low back pain.

There are grounds for proposing two to six physiotherapy sessions at a rate of two to three sessions a week. A multidisciplinary treatment programme may be needed if pain continues into the sub-acute phase.

Other treatments that may be of use but need further study include: acupuncture; behavioural therapy; biofeedback; epidural steroid injections; exercise, including back exercises; temperature treatments; traction and transcutaneous electrical nerve stimulation (TENS).

Section 4: Prognosis

Clinical guidelines state that recovery from acute low back pain has a favourable prognosis, with 90 per cent of patients recovering in six weeks.

However, data on the natural course and prognostic factors in acute low back pain are fragmentary.9

Patients with acute back pain mostly recover without any residual functional loss but chronic back pain is common and may lead to complicated conditions if not treated in a timely and efficient manner.

From 21 to 90 per cent of patients claimed to be pain free or completely recovered within two to six months, depending on the population studied and outcome measurement.10

Delayed recovery
Another prospective study found that 94 per cent of patients evaluated for a new episode of low back pain were no longer visiting their physician for treatment after three months.

However, this was not an adequate measure of resolution of pain with only 21 per cent pain free at three months and 25 per cent at 12 months.10

Low levels of pain and disability can persist from three to at least 12 months and most people will have at least one recurrence within 12 months.10

Delayed recovery and absenteeism is associated with previous chronic back pain; initial pain worse when standing and lying; compensation status (i.e. gain) and other yellow flags.

Time off work is also influenced by job satisfaction and gender and depends more on sociodemographic and job- related influences.

Variable recurrence rates are reported from a low of 35 per cent to a high of 75 per cent.10

The Agency for Healthcare Research and Quality studies suggest that once a patient has had back pain it becomes part of life and, for many, it is intermittently disabling. Repeated visits and procedures do not appear to improve patients' long-term well-being.10

Finally, back pain prognosis does not differ based on the type of provider initially seen or the level of practitioner confidence.10

- Next week: Chronic back pain

Resources

References

1. Clinical Standards Advisory Group. Epidemiology Review: The Epidemiology and Cost of Back Pain. London: HMSO, 1995. ISBN 0-11-321889-3.

2. Deyo R A, Weinstein J N. Low back pain. N Engl J Med 2001; 344(5): 363-70.

3. Airaksinen O et al on behalf of the COST B13 Working Group. European guidelines for the management of acute nonspecific low back pain in primary care. November 2004.

4. Hagen K B, Jamtvedt G, Hilde G, Winnem MF. The updated Cochrane review of bed rest for low back pain and sciatica. Spine 2005; 30(5): 542-6.

5. Roelofs P D, Deyo R A, Koes B W, Scholten R J, van Tulder M W. Non-steroidal anti-inflammatory drugs for low back pain. Cochrane Database Syst Rev 2008; (1): CD000396.

6. NICE Clinical Guideline 88. Low back pain: Early management of persistent non-specific low back pain. London: NICE, 2009.

7. Assendelft W J, Morton S C, Yu E I, Suttorp M J, Shekelle P G. Spinal manipulative therapy for low back pain: a meta-analysis of effectiveness relative to other therapies. Ann Intern Med 2003; 138: 871-81.

8. Waddell G, Feder G, Lewis M. Systematic reviews of bed rest and advice to stay active for acute low back pain. Br J Gen Pract 1997; 47: 647-52.

9. Waddell G, Burton A K. Occupational health guidelines for the management of low back pain at work - evidence review. Occupat Med 2001; 51: 124-35.

10. Pengel L H M, Herbert R D, Maher C G, Refshauge K M. Acute low back pain: systematic review of its prognosis. BMJ 2003; 327: 323.

- For an archive of all GP clinical reviews visit www.healthcarerepublic.com/GP

 

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