Fig. 1 A, Lateral radiograph of the lumbar spine demonstrating grade I spondylolisthesis. B, AP radiograph showing severe osteoarthritis of the left hip. Reprinted from Grimm, BD; Blessinger, BJ; Darden, BV; Brigham, CD; Kneisl, JS; Laxer, EB: J Am Acad Orthop Surg 2015;23:7-17

AAOS Now

Published 2/1/2015
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Maureen Leahy

Radiating Lower Extremity Pain: Is It Lumbar Radiculopathy?

Pain that radiates from the back into the lower extremity is often caused by a herniated disk or spinal stenosis. However, several different pathologies can mimic the symptoms of lumbar radiculopathy. It’s important for physicians to recognize this so they can make accurate diagnoses and render appropriate care.

To learn more, AAOS Now spoke with Eric B. Laxer, MD, one of the authors of “Mimickers of Lumbar Radiculopathy,” appearing in the January issue of the Journal of the AAOS (JAAOS).

AAOS Now: What prompted you and your coauthors to write this article?

Dr. Laxer: In our spine referral practice, it is not unusual for my colleagues and me to see patients whose pain is not actually spine-related. For example, I examined an elderly woman who had been referred to us with persistent back and leg pain. She had received three epidural injections, but they had not helped. It turned out she had a hip fracture.

Another patient referred to us for possible surgery was an elderly gentleman who complained of leg pain both when walking and when trying to sleep. However, patients with spinal stenosis rarely have pain in their legs at night. Plus, when I took the patient’s medical history, I learned he was taking statins for high cholesterol; statins are known for having musculoskeletal side effects. I asked him to check with his primary care physician about stopping his medication and to return in 3 weeks. At that time, his pain was completely gone.

What’s interesting is that both of these patients had lumbar pathology. Lumbar pathology is very common as people age; many patients with degenerative changes in their backs have spinal stenosis. However, being too quick to draw a correlation between lumbar pathology and symptoms—without first delving into the patient’s medical history or doing a thorough examination—may result in unnecessary treatment and a delay in the delivery of appropriate care for some patients.

AAOS Now: What are the most common pathologies that mimic lumbar radiculopathy, and what do clinicians need to know or do to distinguish these pathologies from lumbar radiculopathy?

Dr. Laxer: I don’t believe we know definitively what the most common mimickers are—not enough literature is available. Potential mimickers include musculoskeletal, neurogenic, immunogenic, and iatrogenic conditions. The two mimickers we commonly see are musculoskeletal problems, especially around the hip (osteoarthritis, bursitis) and vascular problems such as vascular claudication.

To distinguish these conditions from lumbar radiculopathy, clinicians need to take a careful patient history, conduct a thorough physical examination, and make sure that what shows on the imaging studies correlates with the patient’s pain pattern. Take the patient I mentioned earlier with the hip fracture. Her pain started as soon as she put her foot on the floor—she couldn’t weight bear at all. And that’s not typical of spinal stenosis; the pain from spinal stenosis normally begins after the patient has been walking for a few minutes.

AAOS Now: In the article, hip abductor weakness is mentioned as being present in 85 percent of cases with either L4 or L5 nerve root etiology, compared to compression of a peripheral nerve. What is the best test for this finding? Can it be picked up on gait analysis only, or is a Trendelenburg test needed for every patient?

Dr. Laxer: If the patient has a compressed peripheral nerve, he or she will usually have other abnormal findings, such as pain that is provoked by a straight leg raise test. In some patients, hip abductor weakness can be picked up on regular gait analysis, but I think the gold standard remains the Trendelenburg test.

AAOS Now: You mention injecting a local anesthetic into the hip joint in patients with both osteoarthritis of the hip and lumbar stenosis (Fig. 1) to help determine the patient’s primary source of pain. If the groin pain disappears but the patient still has leg pain, what is the next step?

Dr. Laxer: If the injection results in a significant reduction in the patient’s groin pain and the clinician believes that the hip is the dominant area of pain, then obviously the hip should be treated in the most appropriate manner. If, however, the patient still has significant leg pain after the injection, the clinician needs to consider that the patient also has a spine problem that causing pain as well.

AAOS Now: What is the role of isolated nerve root injections in determining the patient’s cause of the pain?

Dr. Laxer: The challenging thing with nerve root injections is that sometimes they can be very useful and diagnostic; other times they fall into a bit of a gray zone where the patient gets some—but not dramatic—improvement in pain. Isolated nerve root injections, therefore, can be helpful when they have an obvious impact on reducing the patient’s pain, but that is not always the case.

AAOS Now: What is the impact of mimickers of lumbar radiculopathy on costs of care and liability risks?

Dr. Laxer: At this point, we don’t know enough about the problem to recognize its impact on healthcare costs. But I think potentially this could have a huge impact. That’s because if treatment starts—with medication, therapy, injections, or surgery—and the patient does not improve because it wasn’t a spine problem after all, that care ends up being very costly.

AAOS Now: What advice do you have for orthopaedic surgeons who treat patients with symptoms of lumbar radiculopathy?

Dr. Laxer: As I mentioned earlier, it is very important to take a good patient history and conduct a thorough physical examination. Physicians also have to be very open-minded. We should not assume that what we see on the MRI is the cause of the patient’s pain until we’ve done a complete evaluation and can connect the results of the imaging studies to the patient’s symptoms.

Dr. Laxer’s coauthors are Bennett Douglas Grimm, MD; Brian Joseph Blessinger, MD; Bruce Vaiden Darden, MD; Craig D. Brigham, MD; and Jeffrey S. Kneisl, MD. One or more of the authors reported potential conflicts of interest; visit www.aaos.org/disclosure for more information.

Maureen Leahy is assistant managing editor of AAOS Now. She can be reached at leahy@aaos.org

Bottom Line

  • Several different pathologies have a similar presentation to lumbar radiculopathy.
  • To distinguish these pathologies from lumbar radiculopathy, physicians must first perform a careful patient history and physical examination.
  • Physicians also need to correlate the results of imaging studies with the patient’s pain pattern.
  • Being able to differentiate other conditions from lumbar radiculopathy aids the physician in providing the correct treatment.