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1. LOW BACK PAIN

ESSENTIALS OF DIAGNOSIS

  • Nerve root impingement is suspected when pain is leg-dominant rather than back-dominant.

  • Alarming symptoms include unexplained weight loss, failure to improve with treatment, severe pain for more than 6 weeks, and night or rest pain.

  • Cauda equina syndrome is an emergency; often presents with bowel or bladder symptoms (or both).

General Considerations

Low back pain remains the number one cause of disability globally and is the second most common cause for primary care visits. The annual prevalence of low back pain is 15–45%. Annual health care spending for low back and neck pain is estimated to be $87.6 billion. Low back pain is the condition associated with the highest years lived with disability. Approximately 80% of episodes of low back pain resolve within 2 weeks and 90% resolve within 6 weeks. The exact cause of the low back pain is often difficult to diagnose; its cause is often multifactorial. There are usually degenerative changes in the lumbar spine involving the disks, facet joints, and vertebral endplates (Modic changes).

Alarming symptoms for back pain caused by cancer include unexplained weight loss, failure to improve with treatment, pain for more than 6 weeks, and pain at night or rest. History of cancer and age older than 50 years are other risk factors for malignancy. Alarming symptoms for infection include fever, rest pain, recent infection (urinary tract infection, cellulitis, pneumonia), or history of immunocompromise or injection drug use. The cauda equina syndrome is suggested by urinary retention or incontinence, saddle anesthesia, decreased anal sphincter tone or fecal incontinence, bilateral lower extremity weakness, and progressive neurologic deficits. Risk factors for back pain due to vertebral fracture include use of corticosteroids, age over 70 years, history of osteoporosis, severe trauma, and presence of a contusion or abrasion. Back pain may also be the presenting symptom in other serious medical problems, including abdominal aortic aneurysm, peptic ulcer disease, kidney stones, or pancreatitis.

Clinical Findings

A. Symptoms and Signs

The physical examination can be conducted with the patient in the standing, sitting, supine, and finally prone positions to avoid frequent repositioning of the patient. In the standing position, the patient’s posture can be observed. Commonly encountered spinal asymmetries include scoliosis, thoracic kyphosis, and lumbar hyperlordosis. The active range of motion of the lumbar spine can be assessed while standing. The common directions include flexion, extension, rotation, and lateral bending. The one-leg standing extension test assesses for pain as the patient stands on one leg while extending the spine. A positive test can be caused by pars interarticularis fractures (spondylolysis or spondylolisthesis) or facet joint arthritis, although sensitivity and specificity of the test is limited.

With the patient sitting, motor strength, reflexes, and sensation can be tested (Table 41–2). The major muscles in the lower extremities are ...

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