Natural course of back pain

 

Development of back pain over time

Back pain can be subdivided into acute, subacute and chronic back pain. Back pain often begins with an episode of acute pain that can persist for a period of weeks. There may then follow a period of subacute pain persisting for weeks to months. Back pain that continues for three months is termed chronic back pain. 

I. Acute phase

Rapid recovery in the first month for the majority of patients.
 
II. Subacute phase
Rate of recovery slows down between 1 and 3 months.
 
III. Chronic phase
Very few patients recover after 3 months.
(1)
Frank JW et al. Disability resulting from occupational low back pain. Part II: What do we know about secondary prevention? A review of the scientific evidence on prevention after disability begins. Spine 1996;21(24):2918-29

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Aetiology of back pain

Differentiation of back pain causes

The causes of back pain are most often non-specific – leading to a functional disorder that may involve wear or damage, although often the exact aetiology of non-specific back pain is hard to determine. Specific, clearly identifiable causes of back pain, such as nerve root irritation or compression and inflammatory diseases, are less common.

Specific back pain is often associated with radiculopathy or spinal stenosis, but can also be associated with another specific spinal cause.

(1)
Chou R, et al. Diagnosis and Treatment of Low Back Pain: A Joint Clinical Practice Guideline from the American College of Physicians and the American Pain Society. Ann Intern Med. 2007;147:478-91

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Classification of back pain

Pain intensity correlates to neuropathic components

Chronic back pain can have nociceptive, neuropathic, inflammatory, and/or dysfunctional features1.

  • Nociceptive pain is caused by responses to noxious stimuli and associated with tissue damage.
  • Neuropathic pain is related to a primary lesion in the nervous system.
  • Another type of pain is dysfunctional pain, for which there is no obvious nerve damage.

Pain can also be composed of two overlapping components – nociceptive and neuropathic parts – like for example in many forms of chronic back pain2.

Interestingly, the presence of neuropathic component is more frequent with increasing severity of chronic low back pain. In patients with mild pain intensity, neuropathic pain symptoms are clearly diagnosed in 16% of patients, while in patients with severe pain, this percentage increases up to more than 52%3.

(1)
DiDuro J., Neuropathic Low Back Pain: where does it hurt?. Dynamic Chiropractic December 16, 2009, Vol. 27, Issue 26
(2)
Costigan M, et al. Neuropathic pain: A maladaptive response of the nervous system to damage. Annu Rev Neurosci. 2009;32:1-32.
(3)
Freynhagen R, Baron R, Gockel U, Tolle TR. painDETECT: a new screening questionnaire to identify neuropathic components in patients with back pain. Curr Med Res Opin 2006; 22 (10): 1911-1920

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Diagnosing chronic back pain – red flags

Red flegs in diagnosis

Diagnosis and assessment of the patient presenting with back pain requires thorough and focused history-taking and physical examination to help place patients into three broad categories – those with non-specific pain, back pain associated with radiculopathy or spinal stenosis, or back pain potentially associated with another, specific spinal cause.

The diagnostic process must also ascertain how the back pain manifests physically and how it affects patient function.

Another key objectives in diagnosing back pain are to discover any physical causes that explain the complaint and, in so doing, to diagnose any serious or urgent pathology (red flags) requiring treatment. These include bone fractures, tumours, infections, and spinal crush injury.

(1)
Van Tulder M, Becker A, Bekkering T, Breen A, Del Real MTG, Hutchinson A, Koes B, Laerum E, Malmivaara A. Chapter 3: European guidelines for the management of acute nonspecific low back pain in primary care. Eur Spine J 2006; 15 Suppl 2: S169-S191

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DiagnosinG chronic back pain – yellow flags

Yellow flags in diagnosis

A key element of the assessment of the patient presenting with back pain is to evaluate for psychosocial factors – or yellow flags – that are known to increase the risk for developing or perpetuating pain with an increased likelihood of long-term disability and work-loss due to back pain.

These include:

  • Inappropriate attitudes and beliefs about back pain (for example, high expectation of passive treatments rather than a belief that active participation will help)
  • Inappropriate pain behaviour (for example, fear-avoidance behaviour and reduced activity levels)
  • Work-related problems or compensation issues (for example, poor work satisfaction)
  • Emotional problems (such as depression, anxiety, stress, tendency to low mood, and withdrawal from social interaction)

When taking a history, consider coexisting disease (cardio-respiratory disease, smoking, psychiatric diseases) and lifestyle habits (working conditions, social circumstances, and level of patient education).

(1)
Van Tulder M, Becker A, Bekkering T, Breen A, Del Real MTG, Hutchinson A, Koes B, Laerum E, Malmivaara A. Chapter 3: European guidelines for the management of acute nonspecific low back pain in primary care. Eur Spine J 2006; 15 Suppl 2: S169-S191.

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Examinations of patients with back pain

Typical back pain examinations

Physical examination of the patient with back pain is a crucial element of diagnosis.

  • The straight leg raise test, for example, is positive if pain in the sciatic distribution is produced at 30–70 degrees of passive inflexion of the straight leg. The Lasègue sign can be used to diagnose nerve-root irritation.
  • Other simple tests include asking patients to walk on heels and toes, trying pelvic tilts and a range of motion of trunk movements – all of which may identify pain.
  • The Schober test measures the flexibility of the spine and the FABER (Flexion Abduction External Rotation) test is used to differentiate lumbar spinal problems from primary hip pathology.
  • Referral for imaging may be indicated in patients with severe or progressive neurological deficits or signs of radiculopathy or spinal stenosis.
(1)
Chou R, et al. Diagnosis and Treatment of Low Back Pain: A Joint Clinical Practice Guideline from the American College of Physicians and the American Pain Society. Ann Intern Med. 2007;147:478-91.
(2)
Van Tulder M, Becker A, Bekkering T, Breen A, Del Real MTG, Hutchinson A, Koes B, Laerum E, Malmivaara A. Chapter 3: European guidelines for the management of acute nonspecific low back pain in primary care. Eur Spine J 2006; 15 Suppl 2: S169-S191.

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Rationale for mechanism-orientated pharmacotherapy

Rationale for combining pharmacological principles

A combination of drugs with complementary pharmacokinetic profiles, or use of agents combining more than one analgesic mechanism of action, targets multiple pain pathways and offers the potential of synergy of effect.

Methods of combining drugs include use of single, loose-drug combinations and fixed combination preparations (formulated to contain two agents).

  • The use of free combinations may be limited by the difficulty of maintaining the dose-ratio within the desired therapeutic range and the possibility of poor adherence.
  • This limitations could be overcome by using fixed-dose combinations or analgesics with more than one mechanism of action.

New analgesics with more than one mechanism of action in a single molecule offer the advantage of addressing different underlying mechanisms.

(1)
Morlion B. Pharmacotherapy of low back pain: targeting nociceptive and neuropathic components. Curr Med Res Opin. 2011; 27:1133
(2)

National Institute for Health and Clinical Excellence. 2009. http://www.nice.org.uk/nicemedia/live/11887/44334/44334.pdf


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Overview of pharmacological treatment options

Pharmacotherapy for chronic back pain

Paracetamol, NSAIDs, and cyclooxygenase inhibitors target the nociceptive component of chronic back pain but are largely ineffective on specific neuropathic pain mechanisms.

Opioid therapies target both nociceptive pain and, to a lesser extent, neuropathic pain, reflecting the fact that in chronic pain conditions the role of the opioidergic system in controlling pain perception is frequently reduced.

Agents that inhibit neurotransmitter uptake (e.g. antidepressants) target the neuropathic component of chronic back pain.

Anticonvulsant drugs (ion channel blockers) may offer some efficacy in managing chronic neuropathic back pain but are apparently not effective in nociceptive pain.

Other type of topical agents, like lidocaine plaster preparations, can be useful in managing localized neuropathic pain.

Newer agents like the MOR-NRI tapentadol combine two mechanisms of action, µ-opioid receptor agonism (MOR) and noradrenaline reuptake inhibition (NRI) in a single molecule.

(1)
Morlion B. Pharmacotherapy of low back pain: targeting nociceptive and neuropathic components. Curr Med Res Opin. 2011; 27:1133
(2)
Kress HG. Tapentadol and it two mechanisms of action: is there a new pharmacological class of centrally-acting analgesics on the horizon? Eur J Pain 2010; 14 (8): 781-783

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Headline

Which mechanisms are involved in chronic back pain? Select correct response.
Nociceptive mechanisms predominate
Inflammatory and nociceptive mechanisms principally
Nociceptive, neuropathic, inflammatory, and dysfunctional features may each play a part
Which statement best describes the categories in back pain? Select correct response.
Radicular pain is the most common type of pain and involves radiating pain, while non-radicular pain affects few patients and has a clear aetiology
Non-radicular pain is the most common type of back pain, the cause is usually unclear and pain is limited to one region of the vertebral column
Radicular pain and non-radicular pain are distinguished by the radiating or non-radiating nature of pain and occur equally in patients with chronic back pain
What are yellow flags in diagnosing chronic back pain? Select correct response.
Signs and symptoms suggesting serious pathology requiring urgent treatment
Risk factors increasing risk for developing/perpetuating chronic pain/long-term disability
Used to distinguish radicular pain from non-radicular pain
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Thank you for participating in the tenth basic module “Treatment of chronic back pain”. We hope you enjoyed it. The PAIN EDUCATION platform provides more eModules concerning pain therapy. If you like to, please continue with these eModules and check your knowledge.

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