Pain Relief Blog

Chronic Low Back Pain: epidemiology, pathogenesis, and management

Author: Dr. Faisal Hayat, MBBS

Definition

Chronic low back pain (CLBP) is defined as pain occurring for more than three months period in the lower back region between the posterior lower rib margin and the horizontal gluteal fold.

Epidemiology

Chronic low back pain (CLBP) is the most prevalent type of chronic pain in adults. And is one of the most common health problems worldwide. It has become one of the biggest problems for public health systems in the western world during the second half of the 20th century and now seems to be extending worldwide. Its prevalence is increasing substantially with age due to traumas, stress, or intervertebral disc diseases.

As per the Global Burden of Disease study, low back pain is one of the top ten diseases and injuries people face daily.[1]
It affects around 12 to 34% of the population in developed countries.[2] And is the leading cause of substantial downstream economic losses and reduced quality of life.
In the United States, low back pain (LBP) and neck pain are the leading causes of healthcare spending in 2016, with an estimated $134.5 billion in spendings.[3]

Risk factors

The most important risk factors for chronic low back pain are

Obesity
Female gender
Smoking
Old age
Prior history of back pain
Restricted mobility of the spine
Minimal physical activity
Psychological distress

Pathophysiology

The pathophysiology of low back pain (LBP) is relatively complex, and more than one factor contributes to the development of pain. The main contributors are alteration in the biomechanical properties of the disk structure, sensitization of nerve endings by the release of chemical mediators, and neurovascular ingrowth into the degenerated disks.

Pain-sensitive structures of the spine include the periosteum of the vertebrae, dura, facet joints, annulus fibrosus of the intervertebral disk, epidural veins and arteries, and the longitudinal ligaments. The mechanism by which intervertebral disk injury causes low back pain is uncertain. Some of the theories presented in clinical trials are following

Ingrowth of pain nerve fibers into the nucleus pulposus of a diseased disk is responsible for chronic pain.[4]
Tumor necrosis factor α (TNFα) has the possible pathophysiological role in low back pain suggested in a study.[5]
In another study, obesity was associated with an increased incidence of low back pain.[6] Research evidence to suggest that physical deconditioning and disuse are directly associated with chronic low back pain, in either a causal or consequential manner, is scarce.
A study revealed a slight association between back pain and smoking status. The role of genetic factors is also widely discussed. Twin studies have proven that low back pain and disc degeneration have a genetic background. And almost one-fourth of the genetic effects on pain are attributed to the same genetic factors that affect disc narrowing.
It is suggested that nerve growth factors extracted from degenerative nucleus pulposus might have a role in pain transmission.
Mechanical factors may also have some role in low back pain (LBP).

Management

In the United States, low back pain and related spine disorders are the most expensive medical problems to treat. Following interventions are thought to be effective in relieving low back pain (LBP).

Acute low back pain (ALBP)

It is a self-limited condition and usually resolves without medical treatment in less than a period of one month.

Chronic low back pain (CLBP)

It is a persistent form of low back pain that causes substantial limitations in the activity. In general, activity tolerance is the primary goal, while pain relief is secondary. Evidence supports the use of exercise therapy to relieve pain and improve function. Exercise can be one of the mainstays of treatment for CLBP.

In one randomized trial, cognitive behavioral therapy (CBT) reduced disability and pain in patients with CLBP. These behavioral treatments have similar benefits as exercise therapy. Massage therapy is helpful for short-term relief only.

Non-pharmacological

Heat, massage, acupuncture, or spinal manipulation, are recommended as first-line treatment options. In contrast, initial use of diagnostic imaging, specialty consultation, and prescription of opioid medications in the absence of red flags are not recommended. The red flags to be ruled first are fever, fracture, malignant neoplasms, etc.

Pharmacological

Current literature suggests that NSAIDs and acetaminophen as well as antidepressants, muscle relaxants, and opioids are effective treatments for CLBP. Educate and reassure the patients that improvement is very likely.

In general, avoid bed rest to relieve severe symptoms or keep to a day or two at most. Sometimes it is helpful to use heating pads or blankets.

The anti-inflammatory effects of NSAIDs might provide an advantage over acetaminophen to suppress inflammation, but there is no clinical evidence to support the superiority of NSAIDs. NSAIDs increase the risk of renal and GI toxicity in patients with preexisting medical comorbidities. Some patients take NSAIDs and acetaminophen together for a more rapid benefit.

Skeletal muscle relaxants, such as methocarbamol or cyclobenzaprine, may be useful. Muscle relaxants cause sedation. If these interfere with sleep, prefer to use them only at night. The use of opioid analgesics or tramadol as first-line therapy for ALBP does not have good evidence. So, the use of opioids or tramadol is best reserved for patients who cannot tolerate acetaminophen or NSAIDs and for those with severe refractory pain. Side effects of opioids are constipation, nausea, and pruritus. Falls, fractures, driving accidents, and fecal impaction can also be present. In general, the same treatments recommended for ALBP can be useful for patients with CLBP.

PEMF and TENS

The pulsed electromagnetic field (PEMF) therapy and Transcutaneous electrical nerve stimulation (TENS) are non-invasive and non-pharmacological treatment options for relieving chronic low back pain (LBP). PEMF is established as a low-frequency electromagnetic current with an extended range of frequencies.

Several clinical trials have concluded that Pulsed Electromagnetic Field (PEMF) Therapy alone has a good impact in relieving low back pain. It doesn’t have ionizing or thermal effects. It is safe and drug-free.

TENS is another pain-relieving method that uses an electric current of low voltage. It delivers small electrical impulses to the affected site through these electrodes. Clinical trials have not proven its efficacy and safety in relieving low back pain.

Surgical or invasive techniques

Intensive, multidisciplinary rehabilitation programs are helpful for patients who have not responded to other approaches. It includes daily or frequent physical therapy, exercise, CBT, a workplace evaluation, and other interventions. [4]

Guidelines suggest that referral for an opinion on spinal fusion should be considered for those who have persistent severe back pain or who have completed an optimal nonsurgical treatment program (including combined physical and psychological treatment).
Lumbar disk replacement with prosthetic disks is approved by U.S. Food and Drug Administration (FDA) for uncomplicated patients needing single-level surgery at the L3-S1 levels. This treatment remains controversial for CLBP.

References

Wu, Aimin et al. “Global low back pain prevalence and years lived with disability from 1990 to 2017: estimates from the Global Burden of Disease Study 2017.” Annals of translational medicine vol. 8,6 (2020): 299. doi:10.21037/atm.2020.02.175
El-Sayed, Abdulrahman M et al. “Back and neck pain and psychopathology in rural sub-Saharan Africa: evidence from the Gilgel Gibe Growth and Development Study, Ethiopia.” Spine vol. 35,6 (2010): 684-9. doi:10.1097/BRS.0b013e3181b4926e
Dieleman JL, Cao J, Chapin A, et al. US Health Care Spending by Payer and Health Condition, 1996-2016. JAMA. 2020;323(9):863–884. doi:10.1001/jama.2020.0734
Jameson J.L., Fauci A.S., Kasper D.L., Hauser S.L., Longo D.L., and Loscalzo J., Harrison’s Principles of Internal Medicine. 20^th McGraw-Hill Education.
Biyani, Ashok MD; Andersson, Gunnar B. J. MD, Ph.D. Low Back Pain: Pathophysiology and Management, Journal of the American Academy of Orthopaedic Surgeons: March 2004 – Volume 12 – Issue 2 – p 106-115
Shiri R, Karppinen J, Leino-Arjas P, Solovieva S, Viikari-Juntura E. The association between obesity and low back pain: a meta-analysis. Am J Epidemiol 2010; 171: 135–54.

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