Lumbar Facet Joint Pain
Lumbar facet pain is a common cause of both acute and chronic pain in the low back. Most people experience low back pain at some time in their life. Lumbar facet (zygoapophyseal joint) pain is the cause of this in many of these cases, particularly as people age. The pain usually comes from degenerating facet joints becoming inflamed. Estimates range that from 16% to 41% of patients with chronic back pain without a herniated disc or "radicular" pain extending below the knee, have pain related to the lumbar facet joints.
Over the years, the diagnosis of this condition has been somewhat of a challenge. Conventional studies such as x-rays, CT scans, and MRIs are often inconclusive. Lab tests are also usually not helpful.
Even physical exam findings, although suggestive of facet syndrome, are not conclusive and have shown very poor reproducibility and correlation with diagnostic blocks.
The way that lumbar facet joint pain is usually diagnosed is by anesthetizing the joints using x-ray guided injections known as medial branch nerve blocks. The medial branch nerves are the tiny nerves that come off of the spinal nerve roots and connect to the lumbar facet joints. These tiny nerves and pain signals back down to the nerve root and then on up to the spinal cord and finally the brain where they are interpreted as painful sensations.
Unfortunately, a single diagnostic block is often not helpful. False positive rates with a single diagnostic block can be as high as 49%. In these situations, this invasive test may be no more of effective or informative than flipping a coin. So, given these findings, how do we diagnose lumbar facet joint pain.
In 2013 a study was published in Pain Physician that that reviewed the current literature evaluating the accuracy of a two-block protocol to more definitively diagnose lumbar facet joint pain.
After reviewing a total of 25 studies, the authors in the study found that there was GOOD EVIDENCE for diagnostic facet joint nerve blocks when using a 75% to 100% pain relief as the criterion standard with the dual blocks. The authors found that there was only FAIR EVIDENCE when using a 50% to 74% pain reduction criterion. Using only a single diagnostic block resulted in limited accuracy whether using 50%-74% or 75%-100%.