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Difficulty: MediumOrthopedic Surgery

A 6868-year-old man comes to the clinic reporting a 66-month history of bilateral leg pain, tingling, and cramping. The symptoms consistently begin after walking for about 1010 minutes and radiate from his lower back down the posterior aspect of both thighs to the calves. He notes that the discomfort is significantly relieved when he sits down or leans forward on a shopping cart at the grocery store, but it does not improve when he simply stops walking and stands upright. He has a medical history of hypertension and hyperlipidemia. Vital signs are within normal limits. Physical examination reveals normal muscle strength (5/55/5) and intact deep tendon reflexes in both lower extremities. Dorsalis pedis and posterior tibial pulses are 2+2+ bilaterally. The skin on the lower legs is warm with normal hair distribution. Which of the following is the most appropriate next step in the diagnostic evaluation of this patient's condition?

  1. Obtain an MRI of the lumbar spineAnswer
  2. B
    Measure the ankle-brachial index
  3. C
    Perform a computed tomography angiography of the lower extremities
  4. D
    Refer the patient for immediate decompressive laminectomy
  5. E
    Initiate empiric intravenous broad-spectrum antibiotics

Answer

Obtain an MRI of the lumbar spine
This patient's presentation of bilateral leg pain, tingling, and cramping that occurs with walking and is notably relieved by leaning forward (the 'shopping cart sign') or sitting is the hallmark of neurogenic claudication due to lumbar spinal stenosis. Lumbar spinal stenosis is a narrowing of the spinal canal, often due to degenerative changes such as osteoarthritis, facet joint hypertrophy, bulging intervertebral discs, and thickening of the ligamentum flavum. Extension of the spine (standing upright) further narrows the canal, exacerbating the compression of the nerve roots, while flexion (leaning forward) widens the canal, providing relief. Because the physical exam shows normal peripheral pulses, peripheral artery disease (vascular claudication) is highly unlikely. The most appropriate next step in diagnosis to confirm the anatomical narrowing and evaluate the soft tissues and neural elements is magnetic resonance imaging (MRI) of the lumbar spine.

Step-by-Step Solution

1
Analyze the patient's symptoms and exacerbating/alleviating factors.
The patient experiences bilateral leg pain with exertion that is relieved by spinal flexion (sitting or leaning forward) rather than just rest.
This specific pattern points toward central canal narrowing rather than peripheral ischemia.
2
Evaluate the physical examination findings.
The patient has normal 2+2+ peripheral pulses and normal skin findings in the lower extremities.
Normal pulses rule out significant peripheral artery disease, confirming the symptoms are neurogenic rather than vascular.
3
Determine the optimal diagnostic modality.
Select magnetic resonance imaging (MRI) of the lumbar spine.
MRI provides the best non-invasive visualization of the spinal cord, nerve roots, and surrounding soft tissues (e.g., ligamentum flavum, intervertebral discs) to confirm spinal stenosis.

Key Concept

Neurogenic claudication is characterized by exertional leg pain relieved by lumbar flexion; the diagnostic test of choice is an MRI of the lumbar spine.

Alternative Method

If a patient has an absolute contraindication to an MRI (such as a non-MRI compatible pacemaker), a computed tomography (CT) myelogram is the preferred alternative imaging study to evaluate for spinal stenosis.
Estimated Time:1m 30s
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Orthopedic Surgery

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