Goal of the Study?
The objective of this study 1 evaluates the feasibility of sensory mapping of lumbar facet joint pain in patients scheduled to undergo radiofrequency (RF) denervation.
Why are they doing this study?
Lower back pain (LBP) is a widespread condition that can result in chronic pain. While there are many treatment approaches, one of the most established interventions uses diagnostic blocks to identify the source of nociception. Though many parts of the back can be involved in LBP, facet joints are among the most common sources contributing to back pain. Most often, for treatment in clinical practice, the medial branches are anesthetized to establish the diagnosis of facet joint pain. RF denervation of these nerves, which is a process to stop nerves from transmitting pain, is used as pain management.
The authors argue that while this approach has been well established, the use in a clinical setting has been questioned due to the high rates of false-positive (30%), cost-effectiveness and lack of standardization and anatomical variation. For this reason, the authors hope to develop a strategy for a more precise identification of the nerves involved in LBP.
What was done?
In total, they had 15 participants for this study. After written consent, participants completed a pre-procedure pain diagram and rated their pain on a scale of 1-10. The researchers used a standard procedure for RF denervation, including a single diagnostic block and imaging in determining cannula placement. To reproduce the pain in patients with chronic back pain, medial branches were stimulated using 50Hz electrical stimulation to determine the threshold. This was then increased threefold to achieve the suprathreshold stimulation, after which participants were asked to map their pain and compare this against the initial pre-procedure pain diagram.
What did they find?
A total of 71 nerves were scheduled for RF denervation. Sensory stimulation was successful in 68 out of 71 nerves using 50Hz electrical stimuli. All 15 participants reported either pain or paraesthesia (tingling or prickling) during suprathreshold stimulation, and 14 (93%) reported complete coverage of their usual painful area. In one participant, the upper lumbar pain was not covered by suprathreshold stimulation. For 60% of the participants, they reported pain/paraesthesia outside of their normal pain area during suprathreshold. Overall, in their population, 7.5% of the denervated nerves did not contribute to pain transmission. The average sensory detection threshold was 0.3V, with the suprathreshold was 0.6V.
Why do these findings matter?
Using suprathreshold stimulation, lumbar facet joint pain can be mapped and offers objectivity by reproducing patients’ back pain. This approach can also improve patient safety and experience by limiting RF denervation to nerves involved in pain transmission. This can improve patient safety and experience.