Pain series: introduction
The enigma and burden of chronic pain
Manoj Sivan MD FRCP is Editor of ACNR’s Pain series. He is Associate Clinical Professor and Honorary Consultant in Rehabilitation Medicine in University of Leeds and Honorary Senior Lecturer in the Human Pain Research Group in University of Manchester.
Chronic non-cancer pain is a global health crisis and affects more than one-third of the population in most countries. Healthcare costs of managing chronic pain exceed those spent on cancer, diabetes and heart disease. £12 billion per year is spent on chronic pain treatments in the UK alone. 40% of this current treatment is not effective and patients continue to struggle with psychological distress, low mood and compromised quality of life. The last few decades of research has enhanced our understanding of the neurophysiology of chronic pain in terms of neural biomarkers and modulation of the nervous system to manage pain. However, treatment options still remain limited and far from effective.
Current pharmacological interventions even with regular use, at their best, have shown only an average of 30% reduction in pain symptoms in half of treated individuals. Opioids remain the most efficacious analgesic medications, but long-term usage has serious adverse effects of addiction and dependence. There are some novel disease modifying non-opioid and combination treatments that are being developed and tested, but they are yet to be shown to overcome the issues of side-effects and inadequate efficacy in all individuals.
Implanted neuromodulation devices such as spinal cord stimulators have been in use since the 1980s. They alter neural plasticity at the spinal cord level to alleviate symptoms and have been tested in a variety of chronic pain conditions. They lack superior efficacy (compared to control treatments) in most conditions except chronic intractable neuropathic pain and this remains the only condition for which NICE recommends their use. The complication rate has been reported as up to 50% and implantation is associated with high healthcare costs (up to £10k per device) limiting their cost-effectiveness.
Surgical interventions such as lumbar fusion surgery and joint replacement surgery are effective for pain relief, but not in all patients. There is now conclusive evidence that outcomes (effect size) are similar to non-operative PMPs. Costs associated with back surgery (£8k per surgery on average) are higher than PMP costs. Joint replacement surgery for specific pathologies such as knee and hip arthritis are effective providing long-term benefits in only 80% of patients, but significant side effects. Recent evidence suggests that other orthopaedic procedures such as shoulder and knee arthroscopy are no better than placebo or exercise therapy.
Psychological therapies for chronic pain have been extensively investigated, but with variable results. Evidence suggest a small (~20%) short-term improvement in pain post-treatment and delivery of CBT needs skilled professionals, service resources, and good compliance. Alternative treatments such as Transcutaneous Electric Nerve Stimulation (TENS), acupuncture, yoga, tai-chi and exercise therapy have been shown to effective in some patients, but again not transformational in efficacy. Comprehensive Pain Management Programmes (PMPs) that are approved by NICE are expensive and can cost at least £5k per individual for a 4-week programme. The average pain reduction via PMPs is around 35%.
Therefore, this area of medicine needs further attention from clinicians, researchers and funding bodies that can invest in discovering novel therapeutic approaches. In this series for ACNR, we will focus on four areas: 1) advances in understanding the neurophysiology of chronic pain 2) epidemiology of chronic pain and relationship with other symptoms such as sleep, mood and fatigue 3) a biospychosocial model of chronic pain and rehabilitation and 4) novel therapeutic approaches to manage chronic pain particularly new neuromodulation treatments.
Read the first article: The brain alpha rhythm in the perception and modulation of pain