AME 8.11.08 to 8.15.08 Low Back Pain
Author: Sara McCune, M.D.
Competencies: Medical Knowledge, Practice Based Learning
Learning Objectives: After reading this information you should be able to:
1. Classify low back pain by duration of symptoms
2. Appropriately order diagnostic imaging for low back pain
3. Correctly identify history or exam findings that warrant an urgent specialist referral
4. Properly initiate drug therapy for low back pain
1. “Low Back Pain” Annals of Internal Medicine 6 May 2008, Volume 148 Issue 9,
Low Back Pain (LBP):
o Has a lifetime prevalence of nearly 80% and is the fifth most common reason for
o Is usually due to non-specific musculoskeletal strain
o Is associated with obesity, physical inactivity, occupational factors and depression
o Has a spontaneous rate of recovery of 50-75% at 4 weeks, and more than 90% at 6
o Can be classified by the duration of symptoms:
Acute – less than 4 weeks
Subacute – 4-12 weeks
Chronic >12 weeks
Examination for LBP
o Key elements of a physical exam for LBP include: checking for sensory loss, muscle
weakness, limited range of motion in legs or feet and the characterizing the pain level
o When patients present with back pain and leg pain, nerve root involvement must be
o When patients present with upper motor neuron signs (bowel or bladder dysfunction,
diminished perineal sensation, sensory motor deficits and severe or progressive
motor deficits), urgent sub-specialist consultation is required
o Radiographic exams are usually of limited use unless the history or PE suggests a
specific underlying cause
o Imaging is most useful when the pretest probability of underlying serious disease
requiring surgical intervention is high
o Subacute and chronic LBP may be difficult to treat
o Goal for therapy should be to maintain function and manage psychological distress
o Prolonged bedrest and inactivity are associated with worse outcomes
o Patients should be encouraged to maintain normal activities as possible
o Physical interventions (PT, massage, rehab, back schools, exercise therapy) should
be considered for patients with acute symptoms that persist after 1-2 weeks
o First line drug therapy for LBP is acetaminophen and non-steroidal anti-
o Second line therapy may include short courses of muscle relaxants or opiates
o Opiates have not been shown to be more effective than acetaminophen or NSAIDs
o Short acting opioids should not be used in the treatment of chronic back pain
Patients should have follow up within 2-4 weeks for re-assessment
AME is due in the clinic box by August 15, 2008 for credit
Questions – Part I Name: ______________________________
1. Which one of the following statements about low back pain (LBP) is true?
A. A specific pathoanatomical cause cannot be determined in at least 85% of patients who
B. Acute LBP (pain that lasts six weeks or fewer) and subacute LBP (pain that lasts 6-12
weeks) account for fewer than 50% of cases of LBP.
C. In most cases, the prognosis for a patient who has acute LBP is not favorable unless he or
she receives specific treatment
D. Activity limitation due to LBP is primarily a concern among older adults
2. Which one of the following statements about the evaluation of acute and subacute LBP is true?
A. Routine diagnostic imaging is recommended for all patients who have acute and subacute
B. In patients who have LBP, “yellow flag” findings, such as pain on simulated tests for
axial loading and nonanatomical or superficial tenderness, are definitive signs of
C. A straight leg raise (SLR) test, which is recommended in the evaluation of all patients
who have LBP can be performed in a seated or supine position
D. Waddell’s signs can help the physicians identify the presence of “red flags” that may
require further diagnostic evaluation
3. Which one of the following statements regarding the management of acute and subacute LBP is true?
A. Immediate referral for fluoroscopically guided epidural injections is warranted in patients
who have radicular pain
B. Non-pharmacologic therapies such as “back schools”, interferential therapy, lumbar
supports and ultrasound is never recommended in the treatment of patients who have
acute or subacute LBP
C. Because of the potential risks for abuse, addiction and adverse events, short term opioid
therapy is never recommended in the treatment for patients who have acute or subacute
D. Emergent referral for surgical evaluation is warranted in patients whose medical history
and physical exam indicate possible signs of cauda equine syndrome.
4. Which one of the following red flags requires emergent referral for surgical evaluation when identified
in the medical history or physical exam of a patient who has acute or subacute LBP?
A. Urinary retention
B. History of osteoporosis
C. Decreased Achilles reflex
D. Recent trauma
5. Acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs) are the recommended first line
treatment for pain relief in patients who have acute or subacute radicular symptoms and non-specific LBP.
True or false?
Answers- part I:
Answers for MKSAP:
1. D The patient has acute sciatica with probable L5–S1 nerve root involvement. Nonsurgical
treatment is appropriate initial management because she has no evidence of cord compression or cauda
equina syndrome. Controlled trials demonstrate that NSAIDs provide effective short-term symptomatic
relief for patients with acute low back pain with or without sciatica. Narcotic analgesics should be
reserved for patients with severe pain and prescribed for only a limited time. Spinal manipulation,
physical therapy, and muscle relaxants also demonstrate modest benefit in patients with acute back
pain. Surgical intervention should be considered only if symptoms persist for more than 6 weeks or she
develops progressive neurologic deficits. Two or 3 days of bed rest may be appropriate for patients
with severe pain and disability. Available evidence shows no difference in pain relief or functional
status between bed rest and symptom-limited activity for patients with sciatica, although activity is
more beneficial for patients without sciatica. Prolonged bed rest (7 days) can lead to cardiovascular
deconditioning, bone demineralization, and increased subsequent absenteeism from work. Magnetic
resonance imaging of the lumbar spine early in the course of low back pain is not helpful because the
false-positive rate is high. Patients undergoing early MRI are more likely to undergo surgery—and
incur higher care costs—than patients evaluated with only radiography, but clinical outcomes are
similar for both groups. However, routine plain films are appropriate in patients older than 50 years
because they are at increased risk for malignancy and osteoporotic fractures. Back exercises are not
helpful for treating acute low back pain but may help patients with chronic low back pain return to
2. B The patient's examination findings, consisting of widespread superficial tenderness, pain on axial
loading of the skull, and inconsistent straight-leg–raising tests (should be positive both when the
patient is sitting and supine), suggest a nonorganic component to his back pain. These findings
(Waddell signs) are considered nonorganic because they do not correspond to anatomic distributions or
make physiologic sense. The examination findings and the pending disability claim also suggest that
the patient is at high risk for persistent symptoms. Psychological evaluation is appropriate because
Waddell signs have been correlated with hypochondriasis and hysteria, and the patient may benefit
from antidepressants or cognitive behavioral therapy. There is no convincing evidence that epidural
corticosteroids benefit patients with chronic low back pain resulting from herniated disks or spinal
stenosis; no controlled trials have evaluated patients without neurologic deficits. A meta-analysis
found no convincing evidence that the antispasmodic cyclobenzaprine is more effective than placebo
for treating chronic low back pain. However, cyclobenzaprine does provide modest treatment benefits
for patients with acute low back pain, although adverse effects are common. The patient does not have
any red flags warranting plain radiography, such as trauma, age older than 50 years, history of
malignancy, fever, immunosuppression, substance abuse, or neurologic deficits. An MRI is not
indicated because there are no red flags necessitating early imaging and no reason for considering back
surgery in this patient.
3. B. This patient has evidence of cauda equina syndrome, including urinary retention, saddle anesthesia,
and radiculopathy, probably resulting from epidural spinal cord compression caused by metastatic
prostate tumor. Suspected cauda equina syndrome is an indication for urgent evaluation and requires
definitive imaging to visualize the spinal cord and epidural space. Magnetic resonance imaging is a
noninvasive definitive imaging study for confirming epidural spinal cord compression. Computed
tomographic myelography is also a definitive imaging study, although it requires a lumbar puncture.
Computed tomography of the lumbar spine does not provide an image of the cord and epidural space
as well as MRI does, and it requires longer imaging time in addition to exposing the patient to ionizing
radiation. Although positron emission tomography (PET) is used to detect metastatic tumors, it has
poorer anatomic resolution than MRI, and there are few data on its role in detecting spinal cord
compression. Radiography of the lumbar spine can detect vertebral body collapse and lytic lesions, but
it has limited sensitivity for detecting spinal cord compression. Although radionuclide bone scanning
has a high sensitivity (>90%) for identifying metastases, it also cannot determine the presence of spinal
4. E. This patient has no red flags except possible urinary problems, but has normal sensory and rectal
examinations, making cauda equina syndrome unlikely. This patient has sciatica (about 2% of all
patients with back pain) involving the S1 nerve root as demonstrated by his weak ankle-jerk and
dorsiflexion. The most cost-effective method of caring for a patient in this situation is educational
materials and appropriate pain medication, with bedrest and activity as tolerated for the next few days.
Although chiropractic care or physical therapy are slightly better than traditional care and are preferred
by patients for low-back pain, this patient has sciatica for which neither mode of treatment has been
shown to be effective. Indeed, vigorous exercise programs or prolonged bed rest impede recovery.
Traction therapy has not been shown to be effective for sciatica. Of note, the evidence for
corticosteroid injection or chymopapain injection suggests that, although corticosteroid injections may
provide pain relief in some patients, these treatments do not affect intermediate or long-term outcomes
and carry some risk.
Finally, although he may eventually need an MRI (about 50% of asymptomatic patients in this age
group have a bulging or degenerated disk on MRI) or even surgery, at this point he will likely recover
with conservative care. In fact, 65% to 70% of patients with sciatica recover in 12 weeks, and 10-year
outcomes are almost identical (84% recover), for return to work and neurologic findings, with or
without surgery. A recent cohort study (Atlas and colleagues) reported that, at 5 years, 19% of surgical
patients had at least 1 additional procedure and 16% of nonsurgical patients had opted for surgery.
Early relief from pain was reported by 70% of surgical versus 56% of nonsurgical patients (P < 0.001)
and more surgical patients were satisfied with their condition (64% vs. 46%, P < 0.001), but surgical
patients were just as likely as nonsurgical patients to be receiving disability.
Therefore, this patient should be managed with NSAIDs and perhaps muscle relaxants or tricyclic
antidepressants (for neuropathic pain) and if he is not improving or has worsened after 4 weeks,
referral should be considered. Restriction to lifting less than 20 lbs is appropriate.
5. A. This patient most likely has Mycobacterium tuberculosis infection of the lumbar spine and
requires a CT-guided needle biopsy of the lesion to establish the diagnosis and guide therapy. The
clinical scenario is compatible with various entities, but some type of spinal infection seems most
likely because of the time frame. Distinguishing mycobacterial from bacterial infections of the spine is
difficult without tissue for histopathologic examination and culture, as there is some overlap between
the presentations of more common bacterial infections and less common mycobacterial infections.
Local pain, muscle spasm, and rigidity are the most common presenting symptoms for both types of
infection. Fever and other constitutional symptoms are reported by less than 50% of patients.
Almost all immunocompetent patients with spinal tuberculosis have a positive intermediate-strength
tuberculin skin test, whereas false-negative test results are more common in immunosuppressed
patients. However, a negative tuberculin skin test can never exclude the diagnosis of tuberculosis in
any clinical setting. In immunosuppressed transplant recipients and other persons at high risk for
developing active tuberculosis (for example, patients with HIV infection or persons having recent close
contact with someone with tuberculosis), a tuberculin skin test result of more than 5 mm of induration
is now considered positive and is a key finding in the patient described in this clinical scenario.
Although there is no report of past tuberculin skin testing in this patient, transplantation candidates are
routinely tested before transplantation, and therapy is initiated for any candidates with positive test
results. This preventive therapy does not need to delay the transplantation procedure.
There is no single classic radiographic presentation of spinal tuberculosis. Most series report
infection at one spinal level that usually first involves the anterior vertebral body. However, contiguous
involvement, including the disk space, is not uncommon. As the disease progresses, a paravertebral
abscess may develop that is associated with further destruction of the anterior vertebral body and
subsequent collapse and wedging. A recent review of patients with spinal tuberculosis in France
described purely osteolytic lesions of the spine without disk involvement. This is probably one of the
major distinctions between tuberculous and bacterial osteomyelitis. The latter almost always begins in
and involves the intervertebral disk and tends to involve adjacent vertebrae in a "kissing" fashion.
More than 50% of patients with spinal tuberculosis have normal chest radiographs. Therefore, a
negative chest film does not rule out this infection, but a positive chest radiograph showing active or
inactive disease would strongly support the diagnosis. In a patient with a normal chest radiograph, a
CT scan of the chest provides no additional useful information.
Spinal cord compression is the most serious complication of spinal tuberculosis and requires emergent
MRI and follow-up surgical decompression. However, in a patient without symptoms suggestive of
compression, a normal neurologic examination, and a CT scan suggestive of involvement limited to the
anterior vertebral body, imminent spinal cord compression is unlikely and urgent MRI is not necessary.
Multiple myeloma should always be considered in the differential diagnosis of destructive spinal
lesions, but the patient's age, immunosuppressed state, and positive tuberculin skin test make spinal
tuberculosis a much more probable diagnosis. Therefore, serum protein electrophoresis and urine
immunoelectrophoresis are not needed at this time. Although testicular cancer is the most common
solid malignancy in males between 15 and 35 years of age, pelvic and abdominal lymph nodes are
usually the first site of metastatic disease. The involvement of contiguous vertebral bodies and the
positive tuberculin skin test also argue against the possibility of metastatic testicular cancer as the
cause of the patient's back pain. In addition, the initial evaluation of suspected testicular cancer would
include scrotal ultrasonography, studies for serum markers, and a high-resolution CT scan of the pelvis
and abdomen. Positron emission tomography is usually reserved for evaluation of residual masses
following curative therapy.