Diagnostic evaluation of low back pain

The diagnostic evaluation of chronic LBP is at best a complex and involved undertaking. The most important part of the process lies in the knowledge of the patient and a solid history and physical examination. From there, most of the serious and life-threatening causes of LBP can be elucidated and studies may be used for confirmation. Imaging studies are used most practically as confirmation studies once a working diagnosis is determined. MRI, although excellent at defining tumor, infection, and nerve compression, can be too sensitive with regard to degenerative disease findings and commonly displays pathology that is not responsible for the patient's symptoms. As an example, the high-intensity zones (HIZ) seen on MRI are reliable in determining annular defects in the disc but are not reliable in establishing internal disc disruption as the cause of LBP. Discography is the primary tool used by many physicians to determine the true pain generator when discogenic LBP is suspected. Because the reliability of the patient response is fundamental to discography, interpreting the test in different settings must be considered. In individuals with disc degeneration and annular defects, discography may elicit LBP with injection whether the patient is symptomatic with serious LBP or not. The pain response may be amplified in those subjects with issues of chronic pain, social stressors, such as secondary gain or litigation claims, or psychologic distress disorder. These factors have been shown experimentally to be associated with an increased risk for a false positive injection. The ability of an individual to differentiate the true site of LBP by the quality of sensation with disc injection (concordancy) of pain produced by the injected disc also may not be reliable. In fact, individuals may not have the neural discrimination to differentiate sclerotomal pain originating from different sites in the low back and pelvis. One may realize that chronic LBP illness may not stem from a mechanical spinal disorder alone. In fact, the mechanical pathology may be just a portion of the problem with amplification by neurophysiologic, social, and psychologic issues. Chronic disabling LBP commonly is confounded by chronic pain, emotional troubles, poor job satisfaction, alcohol and narcotic abuse, and compensation issues, just to identify a few. It would follow that expecting to identify a single cause for this symptom complex is impractical and any single test may not be a reasonable approach. Furthermore, surgical correction of the mechanical portion of chronic LBP, even if correctly identified, then can be expected only to relieve a portion of a patient's symptoms as long as the confounding issues continue to be significant or have become lifelong adaptive mechanisms. In the end, the discogram and other diagnostic tests are tools that have clear limitations. In this field, clinical judgment begins and ends with an understanding of a patient's life and circumstances as much as with their specific spinal pathology.