Persistent Low Back Pain
Eugene J. Carragee, M.D.
A 49-year-old maintenance worker with a history of depression and previous reports of minor back pain is seen after four months of continuing low back pain. He has remained out of work for fear of worsening the injury. Magnetic resonance imaging (MRI) two weeks after the onset of pain showed only mild degenerative changes in the lumbar region without spinal stenosis or disk collapse or extrusion. How should this patient be evaluated and treated?
The Clinical Problem
Low back pain without sciatica, stenosis, or severe spinal deformity is common, with a reported point prevalence as high as 33 percent1 and a one-year prevalence as high as 73 percent.2 In physically active adults not seeking medical attention, the annual incidence of clinically significant low back pain (pain level, 4 or more on a 10-point scale) with functional impairment is approximately 10 to 15 percent.3 Acute low back pain (lasting three to six weeks) usually resolves in several weeks, although recurrences are common and low-grade symptoms are often present years after an initial episode. Serious or persistent disability is uncommon even among those with low back pain lasting more than three months.2 Risk factors for the development of disabling chronic or persistent low back pain (variously defined as lasting more than three months or more than six months) include preexisting psychological distress, disputed compensation issues, other types of chronic pain, and job dissatisfaction.4,5,6,7 However, even among patients with one or more of these factors, only 6 percent were out of work for more than one week during a five-year period.7
Strategies and Evidence
Evaluation
The history and physical examination are helpful mainly in identifying risk factors for delayed recovery that may have a psychosocial basis or identifying signs of serious underlying diseases (such as fracture, tumor, infection, or deformity) that require specific treatment. Back pain associated with predominant sciatica (manifested by more radicular pain in the legs than back pain) or neurogenic claudication requires a different therapeutic approach and must be distinguished from low back pain alone. This article focuses on disabling and persistent low back pain without prominent sciatica.
Imaging
Imaging studies in the great majority of persons with low back pain reveal nonspecific findings but no serious pathology. Case series of patients referred with chronic disabling low back pain have shown that disk degeneration,8 annular disruption,8,9,10 and end-plate changes11 have been associated with the severity of pain (Figure 1). However, these findings are also common in cross-sectional studies of asymptomatic subjects.10,12,13 Furthermore, in prospective studies of subjects with no or trivial low back pain who underwent MRI, neither baseline MRI findings nor changes over time were useful predictors of the subsequent development of low back pain.6,7,14,15
конецформыначалоформыMRI or radiography early in the course of an episode of low back pain do not improve clinical outcomes or reduce costs of care.16 MRI is best used to rule out the possibility of impending neurologic injury, infection, or tumors. Appropriate candidates for MRI include patients with low back pain who have associated neurologic symptoms or signs; associated systemic symptoms; risk factors for cancer, infection, or occult fractures; or persistent pain in the absence of neurologic signs or symptoms after four to eight weeks. Patients should understand that the reason for imaging is to rule out these serious conditions, and that common degenerative findings are expected. Ill-considered attempts to make a diagnosis on the basis of imaging studies may reinforce the suspicion of serious disease, magnify the importance of nonspecific findings, and label patients with spurious diagnoses.
Other Diagnostic Techniques
Among patients with persistent disabling low back pain, there are no characteristic findings on physical examination or standard imaging. Therefore, attempts have been made to use provocative injections and anesthetic blockade to identify a hypothetical primary symptomatic structure ("pain generator"). One test used by some clinicians to direct invasive therapy is provocative diskography, which involves injecting dye into an intervertebral disk. Proponents of the test suggest that if injection into a disk reproduces a patient's usual low back pain, then that disk must be the cause of the patient's pain. However, injection into a disk can simulate the quality and location of pain known not to originate from that disk.17 Furthermore, disk injections are painful 30 to 80 percent of the time for patients who do not have symptomatic disk disease but who have had previous disk surgery or who have psychological distress, remote chronic pain, or disputed compensation claims.18,19 A controlled study comparing outcomes of spinal fusion when diskography was or was not used in the preoperative evaluation showed no differences between groups.20
Psychosocial Factors
Psychosocial factors strongly predict future disability and the use of health care services for low back pain. Chronic disabling low back pain develops more frequently in patients who, at the initial evaluation for low back pain, have a high level of "fear avoidance" (an exaggerated fear of pain leading to avoidance of beneficial activities), psychological distress, disputed compensation claims, involvement in a tort-compensation system, or job dissatisfaction.5,6,7,21,22 These psychosocial factors are particularly prevalent in persons with low back pain for whom imaging shows only degenerative changes; 70 to 80 percent of such patients demonstrate psychological distress on psychometric testing or have disputed compensation issues, compared with 20 to 30 percent of patients whose imaging studies reveal definite pathologic or destructive processes.23,24 These psychosocial factors should be routinely assessed in patients with low back pain and taken into account in decisions regarding treatment.