OVERVIEW
Chronic low back pain:
an overview
This article provides an overview of the epidemiology of low back pain, its aetiology, and differential
diagnosis. Current treatment recommendations are reviewed as well as new therapeutic approaches
under development
Rainer Freynhagen
MD DEAA
Professor, Chair,
Department of
Anaesthesiology, Critical
Care Medicine, Pain
Medicine & Palliative
Care, Pain Center Tutzing
Feldafing, Benedictus
Hospital Feldafing;
Academic Teaching
Hospital Technische
Universität München,
Feldafing, Germany
According to the World Health Organization,
low back pain is highly prevalent in Western
countries and one of the major contributors to loss
of quality of life as well as absenteeism. The
condition can be classified, according to the
duration of pain, as acute (less than 6 weeks),
subacute (lasting from 6 to 12 weeks), and chronic
(more than 12 weeks). Although occupation and
working conditions, obesity, lifestyle, body height,
and age are some of the known risk factors, the
exact causes of low back pain still need to be fully
elucidated and its diagnosis is not always
straightforward. It is clear, however, that the chronic
form of the disease, which is frequently associated
with comorbidities such as depression, panic/anxiety
disorders, and sleep disturbances and may even lead
to long-term disability, poses a substantial burden to
societies and health care systems alike. 1,2
Epidemiology and pathophysiology
In 2010, the World Health Organization ranked low
back pain already among the top ten diseases and
injuries worldwide in terms of highest number of
disability-adjusted life years. Its lifetime prevalence
is estimated to be between 60% and 70% in
industrialised countries, with an incidence of 5% per
year among adults. The incidence of low back pain
reaches its peak at ages 35–55 years, and its overall
prevalence increases until 60–65 years and then
slowly decreases. 1 A recent systematic review of the
literature describing studies reporting prevalence
data from medical records in the US, Canada,
Sweden, Belgium, Finland, Israel, and the
Netherlands revealed a wide range of values, from
1.4% to 20%. 3
A total of 37% of the cases worldwide can be
attributed to working postures and repetitive
movements. 1 The Global Burden of Disease Study,
conducted in 2015, reported a global point
prevalence of activity-limiting low back pain of 7.3%,
corresponding to 540 million people, and low back
pain is now regarded as the first cause of disability
worldwide. 4 About 90% of all patients will have
non-specific low back pain, which, in essence,
is a diagnosis based on exclusion of a specific
pathology. Non-specific low back pain has an
estimated point prevalence of 18%. 5
Many physiological mechanisms may act to cause
low back pain. Therefore, the traditional binary
classification of pure nociceptive (arising from
damage to non-neuronal tissue and activation of
nociceptors) pain or neuropathic pain (due to
a lesion/disease affecting the somatosensory system)
was limited in the sense that it was inaccurate and
did not cover all patients. For this reason, the term
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‘mixed pain’ was adopted to designate low back pain
with overlapping nociceptive and neuropathic
symptoms.
Therefore a first definition has been published
recently: Mixed pain is a complex overlap of the
different known pain types (nociceptive,
neuropathic, nociplastic) in any combination, acting
simultaneously and/or concurrently to cause pain in
the same body area. Either mechanism may be more
clinically predominant at any point of time. Mixed
pain can be acute or chronic. 6
Why is that so important? A systematic review
of chronic low back pain studies highlighted that
20–55% of patients had a greater than 90% likelihood
of having a neuropathic pain component, and
a meta-analysis of 20 studies describing the
prevalence of the neuropathic component showed
values ranging from 25% to 73%. 7,8 What is known is
that it has a substantial economic impact and can
lead to suboptimal treatment. The costs of treatment
for patients with back pain plus a neuropathic
component can, in fact, be 50% higher than the costs
incurred by the average patient. 2 A model of
prevalence and cost for back pain in the general
population estimated as much as 67% higher costs
for patients with neuropathic back pain compared
to those with nociceptive back pain only, and 16% of
the total back pain-related costs were attributable to
pain with a neuropathic component. 9
A typical neuropathic pain component is
radicular low back pain, which radiates below the
knee along a dermatome, due to irritation/
inflammation/compression of a lumbar nerve root.
Sciatica, a common symptom in different medical
conditions, can be caused by nerve compression
owing to a protruding intervertebral disk or
inflammation. Pseudoradicular pain, however,
mimics irritation of the nerve root and, while it
projects to the extremities, it cannot be attributed to
a typical dermatome of a nerve root. This distinction
is relevant from the clinical point of view because
projected pain has necessarily a neuropathic
component, whereas referred pain may be
predominantly nociceptive. Moreover, the
therapeutic strategies followed for these two
conditions are theoretically distinct, with
nociceptive pain being sensitive to drugs as non-
steroidal anti-inflammatories (NSAIDs) or opioids
and neuropathic pain being more responsive to
antidepressants and anticonvulsants. 7
For most patients with low back pain, a self-
limited course constitutes the natural history of the
disease. Serious causes of low back pain, on the
other hand, are uncommon, and an exhaustive
search of the aetiology is rarely fruitful.