Dr Cormac Mullins, Fellow in Pain Medicine, and Dr Basabjit Das, Consultant in Pain Medicine, both based in St James’s Hospital, Dublin provide an overview of the physiology and an evidence-based approach to assessment and treatment in primary care
A significant disparity exists between guidelines for management of back pain and clinical practice in many countries with inappropriate use of imaging, rest, opioids, spinal injections and surgery and limited use of first-line treatments.1 The purpose of this article is to review the physiological basis of pain and to outline an evidence-based approach to assessment and treatment of back pain.
Pain is defined as, “an unpleasant sensory and emotional experience characterised by actual or potential tissue damage and described in terms of such damage”.2 Accordingly, pain can be described in either sensory terms (sharp, stabbing, burning, itching), or emotional terms (horrible, unpleasant, excruciating), which may reflect the nature of the pain experience of the sufferer and may guide therapeutic approaches.3
Mechanisms and nociception stages
Pain can arise through three distinct mechanisms: nociceptive; neuropathic; and nociplastic. Nociception is the neural process of encoding a noxious stimulus.4 It consists of four stages: transduction, transmission, modulation, and perception. Noxious stimuli are detected by nociceptors (peripheral sensory nerve endings), which are transduced into electrical activity and transmitted to the dorsal horn of the spinal cord via A-delta and C fibres. Second order neuron transmit this signal in the spinothalamic pathway to the brain.
Modulation can occur at the level of the dorsal horn of the spinal cord by descending inhibitory and facilitatory serotonergic and noradrenergic pathways. This is the mechanism of action of many anti-neuropathic agents in chronic pain such as tricyclic antidepressants. Many exogenous analgesic agents modulate nociception in a similar way as the dorsal horn of the spinal cord (e.g. opioids, clonidine, antidepressants), or by targeting transduction or transmission of the noxious stimulus (e.g. local anaesthetics, nonsteroidal anti-inflammatories).4
Perception involves the integration of sensory signals into a coherent and meaningful message that determines our experience of pain. Pain perception does not necessarily correlate with the severity of an injury. Key components are attention, expectation, and interpretation. The “Fear-Avoidance” model of maladaptive pain behaviour provides a framework for understanding the impact of perception on the development of chronic pain and disability.5
Pain catastrophizing
The presence of “pain catastrophizing” can result in a tendency to magnify the threat of a noxious stimulus (e.g. “I’m afraid that something serious might happen”); feel helpless in the presence of pain (e.g. “There is nothing I can do to reduce the intensity of my pain”); and inability to prevent pain-related thoughts in anticipation of, during, or following a painful event (e.g. “I can’t stop thinking about how much it hurts”).
Pain catastrophizing leads to pain-related fear, avoidance of activity, and hypervigilance. This maladaptive behaviour cycle exacerbates the disability, disuse, and depression experienced by chronic pain sufferers.5
Neuropathic pain is defined as “pain caused by a lesion or disease in the somatosensory nervous system”.6 Postherpetic neuralgia, trigeminal neuralgia, diabetic neuropathy, central post-stroke pain, multiple sclerosis pain are all examples of neuropathic pain syndromes. Neuropathic pain can also present acutely following trauma and surgery.
Screening tools for neuropathic pain include the Douleur Neuropathique in 4 questions (DN4) questionnaire7 and the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS)8 which have an 80 per cent sensitivity and specificity for detecting neuropathic pain.
Recently a third mechanistic descriptor, “nociplastic pain”, has been added to the International Association for the Study of Pain taxonomy. This refers to pain that arises from altered nociception, despite there being no clear evidence of actual or threatened tissue damage causing the activation of nociceptors or evidence for disease or lesion of the somatosensory system causing the pain.9 This pain is often non-mechanical, unpredictable, more widespread, and associated with impaired immune factors and other psychosocial factors.
Flag system and assessment
Assessment of the chronic pain patient begins with history and examination. “Red flag” conditions should be ruled out and the patient stratified for risk of chronicity (“yellow flag” or psychosocial risk factors). A specific cause of back pain is rarely identified, and most back pain is termed “non-specific”.10
Pain history (SOCRATES) should be taken but particular attention should be paid to the impact of pain of function and activities of daily life such as: (i) sleep; (ii) function; (iii) ability to work; (iv) finances; (v) mood; (vi) family life; (vii) social life; and (viii) sex life.
“Red flags” may warrant specialist referral. They include the following:
Thoracic pain;
Fever and unexplained weight loss;
Bladder or bowel dysfunction;
History of carcinoma;
Ill health or presence of other medical illness;
Progressive neurological deficit;
Disturbed gait, saddle anaesthesia;
Age of onset 55 years;
Failure to improve with treatment.
Most “red flag” symptoms have very low specificity for organic pathology and can result in unnecessary specialist referral and imaging. The US guideline for imaging recommends deferral of imaging until after a trial of therapy where there are weak risk factors for cancer or axial spondyloarthritis.11
A substantial overlap exists between “yellow flag” psychosocial factors and the progression from acute to chronic pain.12 These should be assessed early to facilitate intervention. These include:
A negative attitude that back pain is harmful or potentially severely disabling;
Fear-avoidance behaviour and reduced activity levels;
An expectation that passive, rather than active, treatment will be beneficial;
A tendency to depression, low morale, and social withdrawal;
Social or financial problems.
The STarT Back Tool addresses functional limitations and beliefs regarding pain and can stratify patients according to low-, medium-, and high-risk for persistent disabling symptoms.13
Other factors that are important to consider are predictors of “sickness behaviour” such as unhappiness at home or work; and orange flags as markers of underlying psychiatric illness which may warrant referral to a psychiatrist. Lifestyle factors such as obesity,14 smoking,15 and low levels of physical activity16 are associated with the development of low back pain and should be addressed.
A general physical examination should be conducted, including a specific examination of the painful region, a musculoskeletal system examination to look for a biomechanical cause of pain and maladaptive movements, and a neurological examination to outrule radiculopathy. Radiculopathy may be detected by sensory, motor, or reflex impairment in a specific nerve root distribution.
Imaging has not been shown to improve patient outcomes and is associated with unnecessary radiation and medical intervention.17 Guidelines consistently recommend against the use of routine imaging in low back pain except where a specific cause is suspected.18
Treatment options
Most episodes of back pain improve significantly within six weeks, and low levels of pain are reported at 12 months.19 As with any chronic medical illness, chronic pain should be treated initially with lifestyle modification. Recommendations from multiple clinical bodies recommend non-pharmacological approaches as first-line.20-22
This includes self-management advice, reassurance that symptoms should improve over time, encouraging a return to regular activities, exercise and avoiding bed rest. There should be a focus on functional goals and improvement — (“If you had 50% less pain, what would you do that you can’t do now?”) — rather than on spinal abnormalities and investigations. Early supervised physiotherapy is normally not required but it can be considered those with risk factors or for whom recovery is slow.23
For those with radicular pain or radiculopathy, there is insufficient data to recommend that initial management should differ from the approach outlined here.20-22
Exercise programmes: Exercise programmes should consider individual preferences and capabilities. There is no evidence to recommend one form of exercise over another, but options include sports rehabilitation, physical activity as tolerated, aquatic exercises, stretching, aerobic, strength training, endurance, motor control exercise, yoga, and Tai-Chi.
Recommendations for passive therapies such as massage, acupuncture, and spinal manipulation vary across guidelines and short courses can be considered optional for patients who do not respond to other approaches.20-22
For those who exhibit a preference for passive coping strategies or a perceived lack of control over their pain, active strategies should be encouraged, including movement, social participation, early return to work, and diet, and stress management advice.
For those with low expectations of recovery or negative beliefs about their pain, it is important to dispel any “myths” about back pain, offer reassurance regarding imaging. Advice that pain does not necessarily equal damage is important to reduce “fear-avoidance” behaviour. A prompt return to work should be encouraged, although manual handling may be an issue and the healthcare provider may need to liaise with the workplace.
Psychological interventions: Psychological interventions are normally offered to those with persistent pain who have not responded to other treatments, or those with psychosocial barriers to recovery. These include mindfulness meditation delivered in person or through a smart -phone application; cognitive interventions such as cognitive-behavioural therapy, acceptance commitment therapy or compassion-focused therapy; and relaxation therapies. For those with substantial disability, pain management programmes with coordinated delivery of psychological interventions and supervised physiotherapy provide better outcomes than standard treatment.24
Pharmacological treatment: Pharmacological treatment can be used for those with persistent symptoms.20 Paracetamol is no longer recommended as first-line in the management of low back pain due to the lack of evidence of its efficacy and possibility of harm.25 Nonsteroidal anti-inflammatory drugs or (cyclooxygenase) COX-2 inhibitors should be considered as first-line therapy. Ideally a short course of the lowest effective dose should be used with consideration of the potential side effects.22
Most guidelines recommend that weak opioids can be used for short periods, however there is a lack of clear evidence of a benefit so opioids should be avoided where possible considering significant risks and poorer long-term outcomes.23 The use of gabapentinoids is being questioned after a randomised controlled trial failed to show any benefit in radicular pain.26 Muscle relaxants can be considered for a short duration although clear evidence is lacking.22
Two-thirds of patients still report some pain at three months and 12 months.28 Support, reassurance and encouragement is often required, not necessarily more testing, more medication, more referrals, or more procedures.
GP referrals to specialists
Referral to a specialist can be made if there is suspicion of specific pathologies, radiculopathy, or if there is no clinical improvement.
Interventional pain specialists offer assistance in diagnosing and treating pain conditions procedures such as epidural injection, neural blockade, neural ablation, implantable devices, however the role for these therapies is limited and recommendations in guidelines vary.20-22
For prescribing opioids, the Centers for Disease Control and Prevention guidelines recommend establishing and reassessing the goals of treatment regularly and discontinuing therapy if a clear clinical benefit does not exist. Extra precaution is required when prescribing 50mg or more morphine equivalents a day and avoiding 90mg or more. Patients reaching these thresholds should be considered for specialist referral due to the greater clinical risk and likely failure of opioids to achieve clinical goals.27
A surgical referral should be considered in the presence of progressive neurologic deficit, evidence of cauda equina syndrome, or evidence of a fracture.
Psychiatry referral may be warranted in the presence of co-existing anxiety, depression, bipolar disorder, post-traumatic stress disorder, and other psychiatric conditions.
Optimising these conditions may facilitate management of chronic pain. Additionally, addiction psychiatry referral may be required in the presence of substance misuse or a positive urine toxicology screen.
Challenges in implementing clinical guidelines
Internationally, despite recommendations from guidelines, advice regarding education and staying active is only provided in a few consultations,29 about half of patients are prescribed exercise,30 the most common treatment is medication,31 and imaging rates are high.32
Numerous challenges to best practice exist including short consultation times, inadequate knowledge of clinical guidelines, fear of missed pathology and litigation, and a desire to maintain a harmonious doctor-patient relationship.33 Continuous effort is required to challenge societal expectations regarding management of back pain in order to achieve greater alignment with clinical guidelines.
References available upon request.
Read the original article by Dr Cormac Mullins and Dr Basabjit Das , Irish Medical Times, 06.04.2020 - https://www.imt.ie/uncategorised/back-pain-general-practice-06-04-2020/