Technology Insight: Imaging of Low Back Pain

Philip Finch

Disclosures

Nat Clin Pract Rheumatol. 2006;2(10):554-561. 

In This Article

Summary and Introduction

Summary

Chronic low back pain is a common condition that has significant economic consequences for affected patients and their communities. Despite the prevailing view that an anatomic diagnosis is often impossible, an origin for the pain can frequently be found if current diagnostic techniques are fully used. Such techniques include a mixture of noninvasive and invasive imaging. Prevalence data suggest that the intervertebral disc is one of the most common sources of back pain, accounting for around 40% of cases. The pathologic basis for discogenic low back pain might be full-thickness radial tears of the annulus fibrosus. Unfortunately, only MRI can image the internal morphology of the disc, and both CT and MRI lack the necessary specificity to validate this hypothesis. Many so-called radiographic abnormalities seen on CT and MRI are commonly encountered in asymptomatic individuals. Invasive techniques such as joint injections, nerve blocks and provocative discography can show the connection between an abnormal image and the source of low back pain, but do have notable related risks. The development of a noninvasive, low-risk technique that can show this connection is desirable.

Introduction

That an anatomic diagnosis must precede rational treatment of chronic low back pain (CLBP) seems intuitive. Many clinicians, however, consider this approach impossible or of little use, because of the complex psychosocial backgrounds of low back pain patients and the high percentage of 'abnormalities' seen on imaging of asymptomatic individuals.[1] An estimated 80% of the general population suffers an episode of low back pain at some point in their lives,[2] and 5–10% of patients develop persistent back symptoms.[3] This subgroup dominates the patient lists of pain clinics and consumes substantial amounts of their community's health budgets. The likelihood of patients returning to work diminishes as time progresses. CLBP might even be considered a rheumatologic emergency, as prompt, appropriate therapy can help prevent progression.[4]

The intervertebral disc, the facet (zygapophyseal) joint and the sacroiliac joint are not the only sources of low back pain,[5] but are the most common. The literature suggests that 85% of CLBP cannot be diagnosed accurately; however, this proportion can be reduced to less than 50% if modern diagnostic techniques are used to their full potential.[6] The ability to achieve an accurate structural diagnosis of CLBP is thus a matter of considerable importance, as it can lead to rational, evidence-based patient management.

CT and MRI show a wealth of anatomic and pathologic detail, but the specificity of both modalities for diagnosing the cause of low back pain is low.[7] Plain radiographs can also provide information on degenerative change,[8] but invasive techniques such as joint injections and provocative discography are needed to distinguish the painful structure from the asymptomatic. This article focuses on imaging techniques that assist in the diagnosis of discogenic pain. Evidence to date would suggest that pain originating in the disc constitutes one of the most common, but least recognized, forms of CLBP.

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