Chronic low back pain

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

Section 1: Epidemiology and aetiology
A diagnosis of chronic back pain is made by definition rather than physical examination.

Low back pain is defined as pain localised below the costal margin and above the inferior gluteal folds, with or without referred leg pain. Chronic low back pain is defined as that exceeding three months in duration or continuing beyond the normal expected recovery period; most normal connective tissue heals in six to 12 weeks.

Epidemiology
European guidelines suggest that the prevalence of chronic low back pain is around 23 per cent, with 11-12 per cent of the population disabled by it.1

With a high lifetime incidence of back pain of about 84 per cent, relapses of 44-78 per cent and repeated sick leave of 26-37 per cent, this has major health implications.

In a Canadian health survey of 118,000 households, a prevalence of chronic back pain of 9 per cent was found together with a strong link to depression in affected patients. Some 19.8 per cent of those with pain had concurrent depression, compared with 5.9 per cent in those without pain.2

Causes
Chronic low back pain is not simply acute low back pain that has existed for a long time. The development of chronic low back pain is complex and influenced by physiological, psychological and psychosocial factors.3

These influences can be divided into three main categories: neurophysiological mechanisms (peripheral and central sensitisation); psychological mechanisms (behavioural, cognitive-affective and psychophysiological); and barriers to recovery (yellow flags). Specific causes of low back pain are uncommon, representing less than 15 per cent of all back pain.

Chronic back pain is associated with physical neurological changes, as well as psychological and social changes that drive its chronicity and reduce its recovery.

Support levels
Strong evidence shows that low levels of support in the work- place is a predictor of chronicity in patients with acute back pain. The longer the time off work with back pain, the lower chance of ever returning to it.1

Moderate evidence gives the following predictors of chronicity: psychosocial distress, depression, severe pain and functional impact, shorter job tenure, heavy physical work and the inability to modify duties and radicular (pain that radiates) symptoms.1

Section 2: Diagnosis
When assessing chronic pain epidemiologic studies have shown that is best understood on the background of psychosocial factors. Thus a multifaceted approach to management will be needed.2

Exclude sinister pathology
Patients should have been assessed as for acute back pain to exclude sinister pathology (red flags) as these pathologies would need specific emergency treatment.

It is important to remember that any patient can have a severe acute episode on top of the chronic problem, which may result in emergency treatment being necessary.

Neither the European guidelines1 nor the 2009 NICE guidelines4 recommend plain radiography, CT, MRI or bone scans or electromyography unless a specific cause is suspected or spinal fusion is being considered.

Once red flags have been excluded a diagnosis of chronic back pain is made on the basis of unremitting back pain beyond 12 weeks duration.

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.
  • Systemic 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).

 

Section 3: Cognitive and pharmacological management
Considering the psychosocial complexity of chronic back pain it seems reasonable to adopt a multidisciplinary biopsychosocial rehabilitatory approach involving the patient as a member of the team.

This is supported by strong evidence that such an approach reduces pain and improves function and improves work readiness in chronic back pain.1

NICE suggests that individual needs and preferences should be taken into account when considering treatment.

Any psychological barriers (yellow flags) to recovery should be evaluated so that appropriate therapy in the form of cognitive behavioural therapy (CBT) can be implemented.

CBT
CBT is recommended by NICE4 and European guidelines1 and is supported by good evidence.

A systematic review including 25 trials and 1,672 patients showed that CBT was effective in reducing the pain experience, improving coping in individuals with chronic pain.5

CBT for pain management is based on a cognitive model of pain and aims to empower the patient into self-management. It has three basic components:

  • Understanding that cognitions and behaviour can affect the pain experience and showing that patients can partly control their pain.
  • Coping and behavioural strategies; skills training, including pacing, relaxation replacing negative thought processes with positive; distraction techniques.
  • The application and maintenance of these coping skills.6

Pharmacological management
By the time a patient is defined as having chronic back pain most treatments for acute pain will usually have been tried. Those that give relief or partial relief can be continued.

The 2009 NICE guidelines suggest paracetamol and NSAIDs as first-line treatments, with opiates where extra analgesia is required.4

There is good evidence that NSAIDs are effective in chronic back pain1 but, because of GI and cardiovascular side-effects, these are generally used for short-term exacerbations.

Strong level A evidence for weak opiates and limited level C evidence for strong opiates shows that they relieve pain and disability in chronic back pain.1 Because of addiction, sustained-release opiates are preferable to immediate-release products.1 These should be used regularly, rather than on an as-needed basis.

Strong evidence for relieving chronic low back pain exists for tricyclic antidepressants (noradrenergic) and SNRIs.1

Tricyclic antidepressants are mentioned as second-line therapy and advocated for concomitant prescribing where needed.4

Tricyclics have been used in chronic pain for years. Clinically they tend to work better when there is an element of neuropathic pain.1 Tricyclics are limited particularly by their anticholinergic side-effects.

NICE guidance specifically excludes SSRIs for the management of pain,4 although because a large number of patients with chronic pain have concurrent depression it seems perfectly logical to use them to treat the comorbidity of depression, and so indirectly affect the course of pain in the patient.

Generally antidepressants are used in combination with other analgesics rather than in isolation. European guidelines recommend the use of antidepressants as a co-medication for pain relief in patients without renal disease, glaucoma, COPD or heart failure.1

There is insufficient evidence to recommend the use of anti-epileptic drugs, such as gaba-pentin, in nonspecific back pain, but when there is evidence of a neuropathic component then they may be appropriate.

Benzodiazepines are sometimes used but are limited by drowsiness, addiction, reduced liver function and GI side-effects. They should be used at low dosage for a short period of time. The evidence for pain effectiveness is level A.1

From a clinical perspective chronic pain management will often require combination therapy and so drugs from more than one group may be required.

Pathophysiology

Factors affecting chronicity3

  • Premorbid factors
  • Depression, dysthymia
  • Anxiety disorders including panic disorder
  • Cognitive process
  • Traumatic factors
  • Anxiety/panic
  • Fear
  • Psychophysiological response
  • Post-traumatic factors
  • Anxiety, panic
  • Depression
  • Personality disorders
  • Borderline personalities

 

Section 4: Physical treatments and surgery

Physical therapies
NICE suggests a choice of physical treatments including acupuncture, exercise and manual therapy.4 The evidence for acupuncture is not strong and the European guidelines do not recommend it.1

NICE goes on to say that if these treatments fail then intensive treatment should be offered that includes one of these three together with psychological treatments.

NICE advises against offering laser, inferential therapy, ultrasound therapy, TENS, lumbar supports, traction or steroid back injections due to lack of evidence.4

Invasive therapies
NICE and European guidelines generally show little evidence in chronic back pain for invasive therapies including epidurals, facet joint injections, intradiscal injections, intramuscular botulinum toxin and sacroiliac injections.1,4

Surgery
Surgery is rarely suitable for chronic nonspecific back pain and little evidence exists for pain reduction with any surgery except spinal fusion. It should only be considered if combined therapy has failed and pain is persistent and severe.

NICE suggests that surgery other than fusion, for example intradiscal electrothermal therapy (IDET), should not be offered as it lacks evidence.4

NICE also recommends that if pain is causing distress that appropriate therapy to deal with this stress is provided prior to a surgical opinion on spinal fusion being given.

New minimally-invasive surgical techniques are being developed, but will need to be subjected to the same scrutiny as traditional methods before they can be recommended.1

References
1. Airaksinen O et al, on behalf of the COST B13 Working Group. European guidelines for the management of chronic nonspecific low back pain in primary care. November 2004. www.bainpaineurope.org/web/files/WG2_guidelines.pdf

2. Tunks E R, Crook J, Weir R. Epidemiology of chronic pain with psychological comorbidity: prevalence, risk, course, and prognosis. Can J Psychiatry 2008; 53(4): 224-34.

3. Wheeler A H. Pathophysiology of chronic back pain. eMedicine http://emedicine.medscape.com/article/1144130-overview

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

5. Morley S, Eccleston C, Williams A. systematic review and meta-analysis of randomised controlled trials of cognitive behaviour therapy and behaviour therapy for chronic pain in adults, excluding headache. Pain 1999; 80: 1-13.

6. Keefe F J. Cognitive behavioral therapy for managing pain. Clin Psychol 1996; 49(3): 4-5.

 

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