RRS Education Chiropractic BLOG - Musculoskeletal Research Reviews

Finding the exact anatomical cause of most low back pain is challenging. The prevalence of lumbar zygapophysial joint (Z joint, or facet) pain in patients with chronic low back pain is quite variable, with estimates ranging from 5% or less to 45% with several other estimates in between. Z joint pain is often diagnosed by injecting an anesthetic into the painful joint(s) or the medial branches that innervate the suspected joint(s) to see if the pain is relieved (termed diagnostic block).
What may have led to the diverse prevalence rates in the various studies is the use different criteria for case definition, including whether the patients experience 50% relief, 80% relief, or complete relief of pain after a diagnostic block to signify that the condition is present and whether controlled blocks (i.e. placebo [normal saline] vs. anesthetic) were used. When complete relief of pain is required, studies typically report very low prevalence rates, whereas they are higher when partial relief is used as the diagnostic criterion.
There is also inconsistency about whether age is factor in the prevalence of lumbar Z joint pain. Some studies have reported its prevalence to be very low in young patients (as low as 2%) yet very high in older patients, 30% to 40% in those over the age of 65. On the other hand, other studies have reported that age is not a factor in lumbar Z joint pain prevalence.
No previous study on the prevalence of lumbar Z joint pain has based its estimate on complete relief of pain following placebo controlled diagnostic blocks. Confidence in the diagnosis is much stronger when a study’s criteria require complete relief of pain and the use of placebo controls which virtually eliminates false positives, occurring in 25% to 45% of patients when uncontrolled blocks are used.
Therefore, the objective of this study was to estimate the prevalence of lumbar Z joint pain using stringent operational criteria, testing the following 2 hypotheses:
  1. that “pure” lumbar Z joint pain has a nonzero prevalence; and
  2. that the prevalence of lumbar Z joint pain is significantly less than current estimates.
THIS WEEK'S RESEARCH REVIEW: “Prevalence of “Pure” Lumbar Facet Joint Pain in Patients with Chronic Low Back Pain”
This paper was published in Pain Medicine (2021) and this Review is posted in Recent Reviews, Low Back Pain and the 2022 Archive.

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