Sensory mapping of lumbar facet joint pain: a feasibility study.

Objective: To evaluate the feasibility of sensory mapping of lumbar facet joint pain in patients scheduled to undergo radiofrequency (RF) denervation.

Design: Prospective cohort study.

Setting: University teaching hospital.

Subjects: A total of 15 participants listed for RF denervation of lumbar facet joint.

Method: After written informed consent, participants were recruited to the study. Participants completed a pain diagram prior to their procedure. After successful image-guided placement of RF cannulas, the sensory detection threshold using 50 Hz stimulation was obtained, followed by application of suprathreshold stimulation. Participants mapped their stimulated area in comparison to their pre-procedure pain diagram.

Results: All 15 participants had previously undergone diagnostic blocks. All participants were able to report either pain or paraesthesia during suprathreshold stimulation. In total, 14 out of 15 participants reported complete coverage of their usual painful area with suprathreshold stimulation of nerves scheduled for RF denervation. In one of the participants, an area of upper lumbar pain was not covered during suprathreshold stimulation. Nearly two-thirds of the participants (n = 9), reported either pain or paraesthesia, outside their normal painful area during suprathreshold stimulation. A total of 71 nerves were scheduled for RF denervation. Sensory electrical stimulation was successfully achieved in 68 out of 71 nerves (96%). The average sensory detection threshold was found to be 0.3 V while the suprathreshold stimulation was 0.6 V.

Conclusion: Lumbar facet joint pain can be mapped using suprathreshold sensory stimulation, which has the potential to introduce objectivity during RF denervation.