Jesse M. Pines1,2 and Ali S. Raja3 1 US Acute Care Solutions, Canton, OH, USA 2 Department of Emergency Medicine, Drexel University, Philadelphia, PA, USA 3 Department of Emergency Medicine, Massachusetts General Hospital, Harvard Medical School, Boston, MA The lifetime incidence of back pain is 90%, and low back pain accounted for 1.5 million emergency department (ED) visits in 2017.1,2 Only a minority of back pain episodes, approximately 14%, last more than 2 weeks. Low back pain may originate from the lumbar spine, vertebral ligaments, annulus fibrosus, vertebral periosteum, facet joints, paravertebral musculature, blood vessels, or spinal nerve roots. Low back pain may also be a presenting symptom for many systemic disease processes (Table 55.1). Clinicians should seek to answer three key questions in the evaluation of acute back pain:3 Table 55.1 Differential diagnoses of acute back pain Systemic diseases can include vascular disease, cancer, spinal infections, compression fractures, and ankylosing spondylitis. A thorough history is superior to extensive ancillary diagnostic testing to identify these disease processes. For example, abdominal aortic aneurysm is typically found in patients who are older than 60 years, have atherosclerosis, and experience pain at rest.4 Cauda equina syndrome is often the result of a massive midline herniated disc, most commonly in the L4–5, L5–S1, or L3–4 disc space.5 The recognition of cauda equina is most often delayed because the diagnosis was not considered.6,7 Ankylosing spondylitis typically presents with symptom onset before age 40 years with gradual onset, night pain, morning stiffness, and improvement with exercise.8 Epidural abscesses progress from back pain with fever to spinal irritation with Lasegue’s, Kernig’s, and Lhermitte’s signs with neck stiffness and sometimes radiation to the arms or legs, to motor‐sensory deficits and ultimately paralysis.9 It is essential that clinicians recognize that the duration of each phase is highly variable and may be extremely short. Risk factors for epidural abscess include intravenous drug abuse, alcohol abuse, obesity, distal bacterial infections, trauma, and invasive procedures.9–11 ED diagnostic delays in epidural abscesses have occurred in 83.6% of cases, but implementation of a guideline to systematically assess signs and symptoms, erythrocyte sedimentation rate (ESR) and C‐reactive protein (CRP), and then magnetic resonance imaging (MRI), reduced delays to 9.7%.12 The prevalence of these systemic diseases has not been defined in ED populations. By contrast, in primary care patients with back pain, 4% will have a compression fracture, 3% spondylolisthesis, 0.7% spinal malignancy, 0.3% ankylosing spondylitis, and 0.01% spinal infections.2 In a large sample of insurance claims for ED patients with lower back pain aged 18–64 years, imaging was obtained in 34% of visits.13 However, the study found that between 2011 and 2016, imaging decreased from 35% to 32%. Most patients underwent pain radiography, 3% underwent computed tomography (CT), and 0.8% received an MRI. An earlier study found that in the prior decade, in primary care settings, using MRI as the first‐line imaging test for low back pain was not associated with improved functional status, but did result in more surgical interventions and higher costs of care.14 Similarly, multiple randomized trials have failed to demonstrate any measurable benefit to immediate imaging in the absence of features suggesting serious problems.15 A recent systematic review examined the impact of imaging (X‐ray, CT, and MRI) on costs of care and absence from work.16 The review found with moderate quality evidence that costs increased among patients receiving X‐ray and moderate quality evidence that MRI and CT when performed for back pain increases healthcare utilization. Emergency physicians are generally more conservative than primary care physicians in the radiographic evaluation of low back pain.17 Clinical decision support systems have also reduced the inappropriate utilization of lumbar MRI.18,19 Following back pain diagnostic guidelines reduces costs and improves outcomes, but clinicians rarely follow these recommendations.20 Although no emergency medicine guidelines exist for the diagnostic evaluation of acute back pain, multiple specialty societies have published guidelines upon which an evidence‐based approach can be formulated.21 In general, the diagnosis being contemplated should guide the initial imaging choice and urgency. “Red flags” generally signal clinicians to expedite advanced imaging considerations, and 22 “red flags” have been identified in various guidelines (Table 55.2).22 Guidelines for the imaging of suspected spine fractures sometimes diverge because multidetector CT is the method of choice for bony structures (i.e., spinal fracture or bony metastasis), but MRI is the investigation of choice for the spinal cord and ligaments (i.e., cauda equina syndrome or spinal cord infection).22 The duration of back pain should also be included when deciding whether and when to image patients. Two key considerations in contemplating test ordering are noteworthy. First, although guidelines are based upon evidence appraisal and expert consensus, they often ignore clinical realities such as malpractice risk and third‐party payors’ management recommendations.23 Second, clinicians mistakenly assume that negative or positive diagnostic test results offer reassurance to anxious patients, while the evidence suggests the opposite.24 In fact, ordering tests that are unlikely to yield diagnoses for which effective therapies exist (such as back pain) can independently increase the duration of symptoms.25 Table 55.2 Red flags symptoms for high‐risk diagnoses in the ED Source: Data from [21].
Chapter 55
Acute Low Back Pain
Background
Abdominal aortic aneurysm
Ankylosing spondylosis
Compression fracture
Discitis (or spinal osteomyelitis)
Epidural abscess
Herniated disc
Malignancy
Musculoskeletal inflammation
Occult trauma
Pancreatitis
Pyelonephritis
Reactive or psoriatic spondyloarthritis
Spinal stenosis
Disease
Red flags
Cauda equina syndrome
Fecal incontinence
Gait abnormality
Limb weakness
Saddle numbness
Urinary retention
Widespread neuro symptoms
Malignancy
Age > 50
Cancer history
Pain at multiple sites
Pain at rest
Refractory pain
Unexplained weight loss
Urinary retention
Spine fracture
Age ≥50 years
Osteoporosis
Steroid use
Structural deformity
Spine infection
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