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SPECT/CT imaging and low back pain

by Roberto Russo

FACET_JOINTMonitor_1Low back pain is an all-too-common problem, with chronic low back pain (of at least 3 months duration) often causing significant disability and imposing an enormous social and economic burden. The prognosis of acute low back pain is uncertain, although the majority of those affected improve within the first few weeks, with approximately half of the remainder having their pain resolve by 12 months1. Often patients are told they have non-specific low back pain when the discomfort is localized to the lumbar region and no radiating neurological features are present. In that group, attempting to localize the specific cause would only be of benefit if a specific treatment exists. This can be the case when pain arises from the facet joints (or more correctly termed Zygapophyseal joint arthritis).

The term facet joint syndrome was first coined by Ghormley in 1933 and is believed to be a common cause of low back pain, albeit estimates vary widely between 5-90% of cases2,3. The clinical significance of facet joint arthritis is often debated since degenerative changes are often seen at these joints on anatomical imaging (such as x-ray and CT scanning) in patients with no pain. However, we know that Osteoarthritis often has a relapsing and remitting course and so what we really need to know is whether the facet joint arthritis is active at the time of the patients’ symptoms. To do this we need a functional imaging modality, such as a nuclear bone scan with SPECT (the SPECT referring to 3-dimensional reconstruction of the activity in order to better localize the active site of disease).

Holder et al4 found that scintigraphy with SPECT was 100% sensitive and 71% specific in the evaluation for facet joint arthritis in a cohort of patients with low back pain. Furthermore, Dolan et al5 found that the positive findings suggestive of active facet joint arthritis predicted a good response to steroid injection in 95% of patients. The recent addition of a low dose CT, in what is then termed SPECT/CT, improves specificity with regards to determining the level involved (particularly in differentiating L4/5 from L5/S1). Consequently, SPECT/CT appears to be a useful test. However, when should this test be used?

That is a question that still needs further investigation to best answer. However, the scenario where I have found it useful in the evaluation of facet joint arthritis is when;

  • I clinically suspect facet joint arthritis and the patient is unable to engage with physical therapy due to pain despite simple analgesia.
  • When the patient has ongoing pain that impairs function and has been unable to progress through their rehabilitation program.
  • Where physical therapy has not resulted in sufficient symptomatic improvement in a reasonable period of time.

What I hope becomes apparent is that I do not see this investigation or the subsequent steroid injection as a sole intervention but rather as an adjunct to physical therapy which aims to provide a longer duration of disease control (in every sense). Obviously, there are other indications for bone scan imaging, especially when alternate diagnoses are entertained, such as malignancy and/or fracture.

In conclusion, it seems that in a select group of patients with low back pain the use of SPECT/CT imaging can give an accurate assessment for the presence of active facet joint arthritis, which may then provide an opportunity to specifically target the cause of pain. Whilst I had presented the data for steroid injections, I suspect this would extend to other targeted interventions such as medial nerve branch blocks, rhizotomy, as well as manipulative therapy techniques. The latter of which I would be most interested to determine whether mobilizing/manipulating the surrounding joints versus the affected joint would be most useful in improving symptoms.

Reference:
  1. Menezes Costa et al. Prognosis for patients with chronic low back pain: inception cohort study. BMJ, 2009; 339: b3829
  2. Ghormley RK. Low back pain with special reference to the articular facets with presentation of an operative procedure. JAMA, 1933; 101: 10883-10777
  3. Cohan SP, Raja SN. Pathogenesis, diagnosis, and treatment of lumbar zygapophyseal (facet) joint pain. Anaesthesiology, 2007; 106: 591-614
  4. Holder L et al. Planar and high resolution SPECT bone imaging in the diagnosis of facet syndrome. Journal of Nuclear Medicine. 1993; 36: 37-44
  5. Dolan AL et al. The value of SPECT scan in identifying back pain likely to benefit from facet joint injection. British Journal of Rheumatology, 1996; 35: 1269-1273.