Low Back Pain: Evidence-based Diagnosis and Treatment
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Expires April 30, 2017
Low back pain (LBP) is one of the most common reasons for an office visit, but most cases—at least 95%—have a benign underlying cause. Evaluation of LBP patients in the primary care setting, therefore, must focus on identifying “red flags” in the history and physical exam that suggest a significant underlying process requiring further work-up, including imaging. This evidence-based approach helps control costs and prevents the detrimental effects of unnecessary testing.
DIAGNOSTIC IMAGING
The majority of patients presenting with LBP without concerning symptoms can be assumed to have nonspecific mechanical back pain. These patients do not need radiography unless the pain has not improved after four to six weeks of conservative care, because plain radiographs often detect findings (degenerative joint disease, bone spurs, spondylosis) that are unrelated to symptoms.9 Advanced imaging is generally recommended only for LBP patients with red flags due to the potentially critical nature of these cases.5 Patients with LBP presenting with any of these factors require further testing, even if the duration of their pain is less than four weeks.
If a patient’s LBP persists beyond four weeks, the clinician must decide which diagnostic test to order. General medical knowledge suggests that MRI is superior to plain radiography because it shows soft tissue and can detect more concerning abnormalities, such as infections, cancer, and metastatic tumors. CT is better for showing bony abnormalities, but these rarely correlate with a patient’s LBP, and CT subjects patients to levels of radiation that can increase cancer risks.14 Plain radiography in this cohort (LBP > 4 wk) is not generally recommended as it cannot show intervertebral discs or evaluate the degree of spinal stenosis as accurately as MRI. Additionally, these lumbar radiographs expose patients to more than 35 times the radiation delivered in a single chest radiograph.15
COSTS AND PATIENT OUTCOMES
The estimated cost of unnecessary imaging for LBP is $300 million per year.16 There is evidence of a strong association between advanced lumbar spine imaging and increased rates of surgery and significantly higher total medical expenditures.17,18 One study examined patients with nonspecific LBP who either received MRI within 30 days post-onset (defined as “early MRI”) or did not receive MRI. Early-MRI patients had significantly higher total medical expenses ($12,948, P < .0001) than the no-MRI group.17 The early-MRI group also had significantly longer periods of disability and were less likely to go off disability than the no-MRI group (P < .0001).
Cost-effectiveness studies of plain radiographs, dating back to 1982, have yielded similar findings. Liang et al suggested that if radiography was done routinely at the initial visit in patients with acute LBP but no red flags, the cost would be more than $2,000 (in 1982 dollars) to avert one day of pain.19 A more recent study examined patients with acute LBP who received MRI, with one group blinded (both patients and physicians) to their MRI results for six months while the other group received their results within 48 hours.20 All patients underwent a physical exam by a study coordinator, and treatment was assigned prior to imaging. At six weeks and one year, there was no significant difference in treatment assignments or self-reported surveys between groups, indicating that the MRI results had no significant influence on patient outcomes.
Despite the large increase in the use of advanced diagnostic imaging aimed at improving patient care and outcomes, there is a lack of data showing any correlative or causative connection between the two. Given this lack of evidence, and the potentially detrimental radiation exposure and increased costs to patients, clinicians should follow evidence-based guidelines when considering diagnostic imaging in patients presenting with LBP.
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