Sensory Stimulation Threshold: A Viable Tool to Improve the Outcome of Lumbar Facet Radiofrequency Denervation?

BACKGROUND: Sensory stimulation threshold (SST) has been used as a surrogate marker to target a nerve branch for radiofrequency (RF) denervation; however, the validity of SST as a prognostic marker is still under debate. OBJECTIVE: To assess whether lower SST values correlate with better outcomes of radiofrequency denervation for facetogenic low back pain. DESIGN: Prospective cohort study. PATIENTS: Sixty-seven patients who underwent radiofrequency denervation for low back pain. METHODS: Correlations, between the average percentage of pain relief from diagnostic medial branch block (MBB) and RF denervation procedure outcome, and between SST and RF denervation procedure outcome, were analyzed using Spearman correlation coefficient (r(s)). Wilcoxon rank sum test was performed to assess whether magnitude and duration of pain relief following RF denervation differed by the levels of SST (<0.5 and ≥0.5) or pain relief (<80% and ≥80%) from diagnostic MBB. RESULTS: There was a positive correlation between pain relief after diagnostic MBB and pain relief 2 weeks after denervation (r(s) 0.31, 95% CI 0.08 to 0.51, p < 0.01), but not between pain relief after MBB and pain relief 6 months after denervation, nor pain relief duration after denervation. There was a negative correlation between SST and pain relief 6 months after denervation (r(s) −0.41, 95% CI −0.59 to −0.18, p < 0.001). There was also a negative correlation between SST and pain relief duration after denervation (r(s) −0.33, 95% CI −0.53 to −0.09, p < 0.01). CONCLUSION: SST is a viable measurement with which to guide needle placement during RF denervation for lumbar facet pain, and enhances pain relief outcomes.