X-Rays in the Diagnosis and Treatment of Ankylosing Spondylitis

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Ankylosing spondylitis (AS) is a chronic inflammatory disease that primarily affects the spinal and sacroiliac joints, which link the pelvis and spine. Fusion (ankylosis) of the spine's vertebrae, which happens over time, is a hallmark sign of this disease.

Although the signs of AS usually aren't visible on conventional X-rays during the disease's early stages, X-rays are the gold standard for monitoring bone changes and joint fusion if the disease progresses.

This article explains why X-rays are used for diagnosing and monitoring AS, their pros and cons, what to expect during a procedure, and more.

Ankylosing Spondylitis X-Ray

Chinnapong / Getty Images

Why X-Rays for Ankylosing Spondylitis?

X-rays, also known as conventional radiography, are a fast and reliable way to make two-dimensional images of a person's bones and joints. The term "plain X-rays" implies that conventional radiographs are being used alone and not along with other imaging techniques, such as computed tomography (CT) scans or magnetic resonance imaging (MRI). 

Plain X-rays are used to detect and monitor ankylosing spondylitis because they are effective and relatively inexpensive.

Although the hallmark signs of AS may not be visible on an X-ray early in the disease, conventional radiographs produce reliable images that show bone and joint changes. X-rays play a vital role in monitoring the condition over time because AS can cause spinal bones (vertebrae) to calcify and grow together. Plain X-rays are the best way to monitor if vertebrae are fusing together.

Since 2009, the Assessment of SpondyloArthritis International Society's classification criteria recommend using conventional radiography (X-rays) to differentiate two noteworthy stages of ankylosing spondylitis on a continuum. 

In its early stages—when sacroiliitis isn't visible on a conventional X-ray—it is referred to as "non-radiographic axial spondyloarthritis" (nr-axSpA). In later stages, if radiographic sacroiliitis becomes visible on a conventional X-ray, the diagnostic terms "axial spondyloarthritis" (axSpA) or "ankylosing spondylitis" are used interchangeably.

Ankylosing Spondylitis Terminology

Technically speaking, diagnosing AS requires radiographic sacroiliitis being visible on a conventional X-ray. There is an ongoing debate about the terminology used to differentiate among nr-axSpA, axSpA, and ankylosing spondylitis. Some argue that unless there's a meaningful medical reason to differentiate between non-radiographic and radiographic sacroiliitis, the term "axSpA" should be used when diagnosing patients with what has historically been called "ankylosing spondylitis."

Pros and Cons

Some advantages of X-rays include their:

  • Widespread availability
  • Ease of use
  • Speed
  • Low cost

X-rays tend to be less expensive and less time-consuming than CT scans or MRI.

Because they are practical and produce reliable images with minimal hassle, X-rays are ideal for monitoring changes in the bones and joints over time.

Although plain X-rays can chronicle changes in the spine's vertebrae, sacroiliac joints, and pelvic area over time, these changes may take years to become visible using plain X-rays alone. During the early stages of AS, plain X-rays won't show visible signs of the disease. This is a significant disadvantage of only using conventional radiography when the disease is in its early stages.

Another disadvantage of using X-rays too frequently is that high doses of electromagnetic radiation can cause cell damage or mutations that may increase cancer risk. It's important to weigh the benefits of monitoring AS progression using conventional radiography against the risks of radiation exposure.

X-Ray Imaging During Pregnancy

Conventional radiography exposes a fetus to low or very low doses of radiation. Nevertheless, imaging that doesn't emit ionizing radiation, such as MRI, may be safer than X-rays when pregnant or potentially pregnant people need imaging for ankylosing spondylitis.

X-ray technologists use the smallest amount of radiation required to get a clear image. Plain X-rays use relatively small amounts of radiation, while CT scans use more. Evidence-based studies suggest that conventional radiography is safe and shouldn't be feared or avoided.

In general, the pros of using X-rays to monitor and diagnose AS outweigh the cons. Despite advances in medical imaging technology, conventional X-rays remain the gold standard imaging criteria for assessing structural damage in the spine or sacroiliac joints caused by AS.

What to Expect

X-rays are a routine outpatient procedure requiring minimal preparation. Typically, no fasting or other dietary changes are needed before getting an X-ray.

Sometimes, X-ray contrast dye is administered to accentuate a specific body part and make radiographic images more clearly defined. If a contrast agent is used, dietary restrictions may be necessary. 

All metal objects, such as jewelry or watches, should be removed before an X-ray. You'll also be asked if you have any implanted medical devices. Most likely, you'll wear a hospital gown during the X-ray.

The main steps of the procedure include:

  1. You will lie on an X-ray table and be positioned so that the part of your spine being X-rayed is properly aligned with the machine. You may also be asked to stand for an X-ray.
  2. A lead apron may be used to shield parts of your body that aren't being imaged.
  3. Just before an image is taken, the X-ray technician will position themselves behind a partition and ask you to stay very still.
  4. You may hear some clicking and buzzing sounds as the X-ray captures the radiographic image.
  5. If multiple images are needed, the process will be repeated.

This procedure is painless and doesn't have any immediate side effects. Once the X-ray is complete, you'll change back into your clothes and may find out when the results will be available.

What Other Ways Is AS Diagnosed?

There aren't specific lab tests that can automatically diagnose AS.

If someone has symptoms of ankylosing spondylitis, a diagnosis is made based on a set of clinical criteria that, in its early stages, typically includes inflammatory back pain before age 40 that lasts for at least three months and is worse in the morning or after periods of inactivity, but improves with exercise.

Accurately diagnosing AS at various stages of the disease requires taking a multipronged approach. In addition to conventional X-rays, rheumatologists also use MRI and CT scans.

An AS diagnosis may also require blood tests to check for certain inflammatory markers, a medical history of the patient, and a physical exam. Ultimately, though, AS is diagnosed through imaging.

Summary

Diagnosing ankylosing spondylitis can be tricky, especially in the disease's early stages, before bone and joint changes are visible using plain X-rays. MRI works best when the disease is in its early stages, also known as non-radiographic axial spondyloarthritis (nr-axSpA).

Once AS is visible using conventional radiography, X-rays remain the gold standard for monitoring the progression and severity of ankylosing spondylitis. 

A Word From Verywell

Living well with ankylosing spondylitis requires taking a multifaceted approach that includes finding the right healthcare team, cultivating a social support network, staying active, and making other healthy lifestyle choices. Although there isn't a cure for AS, regular exercise and physical therapy can reduce inflammation and help disease symptoms. Medications for AS also can alleviate your pain and slow disease progression.

Frequently Asked Questions

  • What is radiographic ankylosing spondylitis?

    Radiographic ankylosing spondylitis (AS) is when ankylosing spondylitis is visible using conventional radiography (X-rays). If AS is in its early stages and can't be seen using conventional X-rays, it's called non-radiographic axSpA (nr-axSpA).

  • How does ankylosing spondylitis show up on an MRI?

    MRI plays a vital role in the early diagnosis and monitoring of ankylosing spondylitis. It's the most sensitive musculoskeletal imaging technique for detecting AS in its early stages. If radiographic sacroiliitis or other inflammatory changes aren't visible on a conventional X-ray, these signs of ankylosing spondylitis will show up on an MRI.

  • What kind of X-ray can see ankylosing spondylitis?

    In the early stages of ankylosing spondylitis, conventional X-rays can't pick up signs of this inflammatory disease, but magnetic resonance imaging can. As the disease progresses, conventional X-rays, CT scans, and MRI can all be used to view signs of ankylosing spondylitis.

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