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Morgan O’Connor, MD
Charles De Mesa, DO, MPH
Samir J. Sheth, MD
Lower back pain is common with ˜80% of the population having lower back pain at some point in their life.
Most complaints of lower back pain are self-limiting and will resolve without intervention or imaging.
Consideration of, and screening for, red flags is crucial for early identification and management of more serious diagnoses of lower back pain.
Success of therapeutic procedures and surgeries relies heavily on appropriate patient identification/selection.
Lower back pain is a common diagnosis with an estimated 80% of people having at least 1 episode of low back pain during their lifetime.1
Furthermore, lower back is the fifth most common reason for all physician visits in the United States.2
To define the scope of this chapter, lower back pain will be described as the perception of pain within the vertebrae, joints, tendons, and ligaments of the lumbosacral spine as well as the muscles, subcutaneous tissue, and skin overlying this region. Most patients (˜85%) who present to primary care with a chief complaint of lower back pain have symptoms that cannot be reliably attributed to a specific disease or anatomic abnormality (thus termed nonspecific low-back pain),3
and most patients recover without significant medical intervention within a few weeks.4
As with all musculoskeletal complaints it is important to include in the location, duration, details of any prior back pain, severity of the pain and any palliative or provocative features. Although the majority of patients presenting to primary care with a chief complaint of lower back pain will not have a serious condition, it is important to ensure consideration of more concerning causes in your evaluation. For example, pain that fails to improve with 1 month of therapy, unexplained weight loss, and previous history of cancer are associated with high specificity (90%) for cancer.5
In patient with a history of cancer, sudden onset, severe pain should raise concern for a pathologic fracture. Spinal infections such as vertebral osteomyelitis or epidural abscess are modestly associated with a history of intravenous drug use or urinary tract or skin infections (sensitivity of 40%)6
and may have associated symptoms such as fever and malaise. Other concerning findings by history include diminished sensation, weakness, and/or bowel/bladder incontinence, as these raise the threshold of suspicion for neurologic injury such as an acute radiculopathy or cauda equina syndrome. Bladder incontinence, in particular, is very sensitive for the detection of cauda equina syndrome (90%).7
MECHANISM/TIMING OF INJURY
The mechanism of injury for lower back pain can provide insight into possible pain generators in lower back pain. Acute pain after a lifting injury may indicate a soft tissue sprain or strain or possibly an acute disc herniation. An elderly/osteoporotic individual reporting acute-onset back pain after a bumpy car ride, coughing/sneezing, or mild trauma would be concerning for vertebral
compression fracture. Conversely, chronic lower back pain in overweight individuals who spend most of their time at work sitting with poor posture may indicate discogenic pain (see Table 19-1
Pain location and radiation characteristics may help in making an accurate diagnosis (Figure 19-1
). Patients with lumbosacral spondylosis (zygapophysial or facet joint arthropathy) may report a deep achy pain radiating in a band across the lower back and/or radiation into the buttock or thigh, with radiation below the knee being rare.8
TABLE 19-1 Possible Lower Back Pain Diagnoses Based on Timing/Onset of Pain
Sacroiliac joint pain, a common source of nonradicular axial back pain, tends to be located at the lumbosacral-gluteal junction with referral into the ipsilateral lower extremity and/or groin. In general, sacroiliac joint pain causes pain at and below the waistline, whereas those with lumbar facet arthropathy will tend to localize their pain at and above the waistline.
Lumbar or sacral radicular pain is described as sharp/shooting/lancinating pain felt both superficially and deep that radiates down the leg.9
In the absence of objective neurologic deficits this pain is called radiculitis. Radicular pain may occur secondary to mechanical factors causing impingement upon a nerve root (such as neural foraminal stenosis or a disc bulge) or owing to chemical irritation secondary to exposure of the nerve roots to herniated nucleus pulposus (which is enzymatically active and irritating to the nerve roots). This pain, with the possible exception of the S1 nerve root, does not reliably follow a specific dermatomal pattern when patients describe their symptoms.10
Conversely, a lumbar or sacral radiculopathy is characterized by objective signs of neurologic deficits such as diminished sensation, strength, or reflexes in a dermatomal and/or myotomal pattern congruent with a nerve root distribution.
In any complaint of lower back pain, it is important to evaluate for any objective findings of neurologic deficit with examination of strength, sensation, and reflexes in the lower extremities. This can be accomplished efficiently but thoroughly with an understanding of lumbosacral dermatomes, myotomes, and reflexes. A sufficient examination for screening strength would include assessment of hip flexion (L2), knee extension (L3), ankle dorsiflexion (L4), great toe extension (extensor hallucis longus, L5), and ankle plantar flexion (S1). A screening sensory examination should include the L2-S2 dermatomes (see Figure 19-2
for reference). Reflex examination should include patellar reflexes (primarily L4), medial hamstring reflexes (L5), and Achilles reflexes (S1), with particular attention being paid to asymmetry from side to side. In addition, assessment for upper motor neuron signs in the lower extremity should be included, as injury at/above the level of the conus medullaris (generally ˜L1) may cause an up going great toe on plantar response (Babinski sign) and/or clonus on ankle jerk.
Pain primarily located in the soft tissues of the lower back/buttock region may represent myofascial pain. This is conventionally defined as regional pain originating from exquisitely tender taut bands of muscle (trigger points) and may exist in isolation or as a response to postural or muscular accommodations for an underlying anatomic process such as degenerative disc disease, lumbar facet arthropathy, or scoliosis.11
Alleviating and Exacerbating Factors
Identification of movements and positions that exacerbate or alleviate pain can provide clues for diagnosing and treating lower back pain (see Table 19-2
). For example, the zygapophyseal (facet) joints are synovial joints and, like other arthritic joints, pain may
be exacerbated with joint loading. Lumbar extension loads these zygapophyseal joints and causes an exacerbation of pain.12
FIGURE 19-1 Generalized pain referral patterns of lumbosacral facet arthropathy.
FIGURE 19-2 Lower extremity dermatomes.
Discogenic pain, or rather pain secondary to disc degeneration/annular derangement is often characterized as a dull midline pain or feeling of instability that may radiate to the buttocks; however, as compared with zygapophyseal joint pain, discogenic pain tends to be exacerbated by forward flexion of the lumbar spine or postures/positioning that can increase intradiscal pressures (such as sitting). This is due to the degenerative changes of the disc causing abnormal motion provoking mechanical stimulus of local nociceptors13
or disruption of the inner portions of the anulus fibrosus allowing the neuroirritating nucleus pulposus access to the outer one-third of the anulus fibrosus, which is innervated by the sinuvertebral nerves (Figure 19-3
Lumbar spinal stenosis may also be described as a dull lower back pain with some degree of radiation to the sides or buttocks; however, unlike most other types of back pain, spinal stenosis tends to be exacerbated by standing and improved with sitting. Furthermore, a key feature of lumbar spinal stenosis is neurogenic claudication. Like vascular claudication, neurogenic claudication
is a progressively worsening aching/fatigued sensation in the legs (anterior thigh or calves being the most common) with standing and walking. In contrast to vascular claudication, the lower extremity discomfort in lumbar spinal stenosis is often eased by forward flexion of the trunk.14
A common description that patients may provide is that they find themselves leaning over handle of a shopping cart as it eases their pain, a so-called shopping cart sign.
TABLE 19-2 Suspected Lower Back Pain Diagnoses Based on Alleviating Versus Exacerbating Factors
Lumbar spondylosis (facet arthropathy)
Changing positions, rest
Lumbar extension biased postures (such as standing)
Lumbar discogenic pain
Lying supine with legs elevated/supported
Lifting, coughing, Valsalva, lumbar flexion biased postures (such as sitting)
Lumbar radicular pain
Rest, lying supine with or without knees flexed
Increased neural tension (postures with increased lumbar or hip flexion with straight leg). Lifting, coughing, sneezing, Valsalva
Lumbar spinal stenosis
Sitting, spinal flexion
Walking, spinal extension
Sacroiliac joint pain
Unloading affected side
Prolonged sitting, forward flexion of the trunk/hip, transitional activities (i.e., sit to stand)
Gentle stretching of affected soft tissues, changing positions
Rapid activation or stretching of affected soft tissues, being in a single position for a prolonged time
Although uncommon, vascular causes of lower back pain are important to be cognizant of and consider in your differential diagnosis in individuals with risk factors (such as obesity, diabetes mellitus, hypertension, hyperlipidemia, smoking). These vascular causes include peripheral arterial disease that may manifest as axial lower back pain with radiation into the lower extremities with exacerbation by activity with claudication symptoms as discussed earlier.15
Physical examination of these patients may be notable for absence of local lower back symptoms such as tenderness to palpation or exacerbation with flexion/extension and positive for decreased peripheral pulses or color/temperature changes in the lower extremities.
Another vascular cause of lower back pain that is critical to recognize is an arterial aneurysm (such as that of the abdominal aorta or iliac arteries). A patient with an abdominal aortic aneurysm may complain of vague abdominal or lower back pain that is described as deep/throbbing/pulsing and difficulty finding a comfortable position. Physical examination may be notable for a pulsating abdominal mass.16
If patients complain of acute/tearing pain or hypotension is present, they should be taken immediately to an emergency room; otherwise the patient should be evaluated with an abdominal ultrasound and referred to vascular surgery.
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