Causes and Sources of Chronic Low Back Pain

This article is still missing information.

While The causes of acute low back pain are largely unknown, this is not the case for chronic low back pain, where a biomedical diagnosis is possible in some 50-70% of cases.

The Myth of Non-Specific Low Back Pain

It is often incorrectly stated that the cause of low back pain cannot be diagnosed in 85% of cases with exact figure differing with different publications (some say 80%, some say 90%) This "convenient truth" has been proven to be false time and time again. Unlike acute low back pain where the causes are largely unknown, The causes of chronic low back pain are largely known. History and examination are insufficient for diagnosis, yet the cause can be established in 50-70% of cases as long as there is access to appropriate investigations and the investigations are done in a logical manner.

The fact that some authors and clinicians continue to perpetuate the myth that most chronic low back pain is "non-specific low back pain" appears to be ideological in nature, rather than based on evidence. Typically the references given for the incorrect figure are either non-existent, are other review articles that reference yet further review articles, or are review articles that don't support the figure at all.

An example of this "train of intellectual dishonesty" regarding the prevalence of "non-specific back pain" is presented here for illustration. The lancet review by Hartvigsen 2018 ("nearly all") which has been cited 416 times as of writing references a review by Maher from 2017 ("90%"), which references a review by Koes from 2006 ("90%"), which references a review by Deyo from 1992 ("85%"), which references an expert opinion workshop by White from 1982 ("20% to 85%") and speech by Nachemson from 1984. The workshop figure is unreferenced, and I am unable to access the full speech. The 2017 review by Maher also dishonestly references a study on acute low back pain, another review by Deyo from 2001 ("85%") which does not reference the figure, and another study of older adults that only looked for vertebral fracture in patients with mixed acute and chronic back pain. The reference train runs dry at that point. Sometimes we find that the reference train leads to a report by the Quebec Task Force in 1987.

The reference train usually leads to articles published at a time that predated the advent of precision diagnosis, or dishonestly references articles on acute low back pain where precision investigations were appropriately not done. These older articles also commonly confused sciatica, spondylosis, spondylolisthesis, and spondylolysis with low back pain, and so false-positives were likely also common, not just false-negatives.

In the last 30 years imaging and investigation techniques have drastically improved, and it is now possible to determine the cause in the majority but not all cases. In New Zealand it is usually lack of funding for access to the appropriate diagnostic tools that renders diagnosis impossible, rather than the tools themselves not existing.

Red Flags

Red flag conditions, such as tumours and infections are uncommon, if not rare causes P% = prevalence of a serious condition in patients with acute back pain Z% = of these patients above, develops chronic back pain Prevalence of serious condition in patients that develop chronic lower back pain = (P/Z)% Eg tumours: P=1%, If 30% of acute patients become chronic, prev in chronic = (1/30)% = 3%

Structural Abnormalities

Tempting, but incorrect, to attribute chronic low back pain to structural abnormalities

• Congenital
  • Transitional vertebrae, non-dysjunction (congenital fusion) and spina bifida occulta occur equally commonly in asymptomatic and symptomatic individuals
• Spondylolisthesis
  • Large scale epidemiological studies shown in adults – not associated with pain
• Spondylolysis
  • Pars defect occur in 7% of asymptomatic population, more common in sports people
  • Equally as common in asymptomatic and symptomatic
  • Definitive test – anaesthetize the defect
  • “stress fracture” in pars interarticularis. relief of pain with LA implies defect is source, predicts surgical success
• Spondylosis/Disc degen/facet degen/OA
  • Do not constitute legitimate diagnoses of cause or source of pain

Instability

Controversial term, various definitions. Clinicians have classified instability according to nature of lesions on imaging

1. Fractures and fracture dislocations
2. Infections of ant elements
3. Neoplasms
4. Spondylolisthesis
5. Degenerative

Does not require demonstration of instability in biomechanical sense

Spondylolisthesis

Spondylolithesis rarely progresses in adults Radiographic studies show that Grade 1 and 2 are associated with reduced range of motion rather than instability Further precision studies have shown that motion patterns of patients are indisguishable from degenerative disc disease

Degeneration of the Lumbar Spine

Several types of instability have been attributed to degen of lumbar spine These include:

• Rotational – hypothetic entity, certain radiographic signs suggested, reliability/validity not est
• Retrolisthetic – during extension (but this movement can occur in asymptm)
• Translational – abnormal forward translation during flexion. Difficulty in defining upper limit of normal (3-4mm in different studies)

Despite all efforts to define – no studies have shown that it is related to cause of pain, nor rectifying it abolishes symptoms

Degenerative changes are an expression of metabolic stress, not a disease No known mechanism whereby degenerative changes can be painful Lots of different triggers, however final common pathway Degenerative joint disease is a disturbing label that patients associate with a poor prognosis Genetic factors predispose to degenerative changes, but age is the strongest correlate In contrast, features of internal disc disruption correlate strongly with back pain

Biology

• Chondrocytes maintain balance between synthesis and degradation
• Synthesis promoted by growth factors
• Degradation achieved by action of MMP, whose synthesis is activated by TNF𝛼
• Osteophytes – adaptive modelling, attempt to increase surface area to reduce load. May be normal joint, with excessive load, or joint which capacity to bear loads is compromised by degradation of matrix.

Regional Differences - Discs

• Cervical
  • Differ from lumbar discs in their anatomic structure and their expression of degenerative change
  • Cervical discs lack a concentric anulus fibrosus, only well developed anteriorly
  • Nucleus pulposus persists until 2nd decade, changes to firm, dry fibrocartilage plate
  • Changes are essential for allowing axial rotation
• Lumbar
  • Degen changes are more chemical in nature, expressed as changes in PG/hydration. Seen on MRI with change in signal intensity

ZA Joints

• Cervical:
  • Face upwards and backwards, therefore equally share compressive load with discs
  • Injuries most likely to occur from weight bearing
  • Degenerative changes occur at all levels, most commonly C3/4
• Lumbar:
  • Face posteriorly and laterally, share little of the axial load
  • Resists axial rotation and anterior translation
  • Degenerative changes arise earlier, more common in L4/5

Causes of degenerative disc disease

Specific metabolic causes are rare

• Limited to diabetes mellitus and ochronosis
• Impaired nutrition promoted, evidence lacking
• Vascular disease, smoking weak correlate
• Low grade infection explored – not conclusive
• Strongest relationship – AGE

Aging Changes

• Chondrocytes might be subject to innate senescence
• They may have genetic abnormalities that affect matrix quality
• Or normal cells may become impaired with accum toxins/mechanical stresses
• Z joints have not been explicitly studied
  • Under umbrella of synovial joints – combination of genetic factors/abnormal biomechanics
• Lumbar disc degeneration – evidence more explicit (twin studies)
• Heavy loads account for some variance
  • Larger proportions explained by genetic factors

Correlations

• One method is to compare prevalence in people with and without pain. If prev is higher in people with pain, association is established
• Another method is to anesthetize joint. If relieves pain, target joint is implicated as source.

The prevalence of lumbar disc degeneration in asymptomatic individuals, clearly increases with age Radiographic features of cervical spine in asymptomatic people again increases with age (hardly any “normal” looking spines in over 50)

Neck Pain

Study compared patients with neck pain, with controls. There were no differences in prevalence of spondylosis, severe disc changes or facet joint changes between cases and controls. Degenerative changes in cervical discs/z joints do not correlate with pain

Low Back Pain

A large population study looked at osteoarthosis in the context of pain No association with pain, irrespective of grade Many studies on disc degeneration Systematic reviews on high quality studies showed no clinical association between degenerative disc changes and pain

Spondylolisthesis

• Spondylolithesis – translation of 1 vertebral body on another. 6 broad categories – (wiltse classification) isthmic, traumatic, degen, pathologic, dysplastic and post surgical. It can also be classified according to severity (Merding)
• Bogduk – not associated with pain, finding it on xray does not constitute diagnosis. Rarely progresses. Grade 1 – 2 associate with reduced ROM rather than instability.

Degenerative Lumbar Spondylolisthesis

• Incidence 19-43%, mean age 71, most common in females
• Most common L4/5
• Initial event – disc degeneration/narrowing of disc space - micro-instability
• Cause of pain multi factorial
• Most are grade 1 (75%) – less than 25% slip
• Average slip progression – 18%, no correlation between progression and symptoms
• Natural history and management of low grade slip is controversial, conservative management generally indicated. Surgery for refractory cases

Isthmic Lumbar Spondylolisthesis

• Isthmic meaning movement of one vertebrae on another, due to a defect in the pars, termed spondylolysis (unhealed stress fracture). Spondylolysis can be present without displacement. Spondylolistesis occurs in 40-60% of patients with bilateral spondylolysis (unlikely if unilateral).
• Most are asymptomatic, 25% have back/radicular pain
• Prevalence in children 2.6%, increasing to 4% in adult
• Asymptomatic in 3-11% of adults
• More common in men, L5/S1
• Causes are multifactorial, genetic component
• Back pain may be from micro-stability or pain from degenerative disc
• Symptomatic patients are initially treated non-operatively

High grade lumbar sponylolisthesis

• Defined as >50% slippage
• Most are at L5/S1, a result of isthmic spondylolisthesis
• Most have a degree of neurologic compromise
• Pain usually with hyperextension, resolves with time due to fracture union
• Treatment is focused on correction of lordosis and sagittal balance
• Natural history – difficult to predict if further slippage will occur
• Conservative management trialed in adolescence, usually unable to provide permanent relief�

Surgical vs Non Surgical Treatment of Lumbar Spondylolithesis – Karsy et al.

• Non operative effective in patients without neurogenic claudication or radiculopathy and stable spondylolisthesis (grade 1)
• 1/3 show progression over time
• Lumbar decompression alone can be effective for low grade, fusion if higher grade
• Mechanical instability is change of 3mm-6mm between flexion/ext films, or change from sitting to standing
• Meta analysis – surgical intervention is more effective than non operative, for patients with pain and functional limitations

Lumbar instability – J. Beazell

• Historical term, that has been debated through 1980-90’s
• Encompasses two types:
  • Mechanical (radiographic)
  • Functional (clinical)
• Topic is subject to much debate on exact nature of problem, correlation with history and relevance to patient management

Seminal Journal Articles

Degenerative Joint Disease of the Spine – N. Bogduk. Radiol Clin N Am 50 (2012) 613–628

High-Grade Lumbar Spondylolisthesis – A. Beck et al. Clin N Am 30 (2019) 291-298

Isthmic Lumbar Lumbar Spondylolisthesis – A. Bhalla. Clin N Am 30 (2019) 283-290

Degenerative Lumbar Spondylolisthesis – M. Bydon. Clin N Am 30 (2019) 299-304

Surgical vs Non Surgical Treatment of Lumbar Spondylolisthesis. Clin N Am 30 (2019) 333-340

Lumbar instability: an evolving and challenging concept. J. Beazell. Journal of Manual and Manpulative Therapy. Vol 18 1 (2010)