Effectiveness of Genicular Nerve Cooled Radiofrequency Ablation on Chronic Knee Osteoarthritis Pain

Background: Outside of an invasive total kneearthroplasty, the available therapies for the treatmentof pain secondary to knee osteoarthritis(OA) provide marginal and short-lived symptomaticrelief. Genicular nerve radiofrequencyablation (RFA) serves as an alternative treatmentmodality for OA-associated knee pain anddisability.Objectives: To quantify the effectiveness ofcooled radiofrequency ablation (C-RFA) of thegenicular nerves for chronic knee pain secondaryto OA.Study Design: Retrospective chart reviewperformed using Redcap, implementing currentprocedural terminology codes.Setting: An academic pain management center.Methods: Study population included patientstreated with C-RFA from April 2015 through June2017. Numeric Rating Scale (NRS) data wereanalyzed at 3 time points: 2 weeks, 4-6 weeks,and 7-33 weeks post-RFA (extended follow-up).Primary outcome for statistical analysis was NRSand the change in NRS from baseline at eachof the 3 predetermined time points. Differencesbetween the change in NRS and the number ofdiagnostic blocks performed (1 vs. 2) was evaluated.Correlation between the change in NRS andpatient body mass index (BMI) was calculated.Results: Pre-RFA average NRS scores wereavailable for 47 knees from 31 individuals, whichwere included in the analysis. The mean NRSscore decreased by 50% at 2 weeks (n = 33; P< 0.001), 55% at 4-6 weeks (n = 18; P < 0.001),and 26% at 7-33 weeks (n = 18; P = 0.009).Eight patients (12 knees) provided specific dataon the total duration of relief following RFA. Themean duration was 39 weeks or approximately9 months. There were no statistically significantdifferences between groups receiving 1 versus 2diagnostic blocks at 2 weeks or 4-6 weeks post-RFA. At 7-33 weeks, those who received 1 blockhad a decrease in NRS of –3.1, whereas thosewho received 2 blocks had an increase in NRSof +0.1 (P = 0.008). There was no correlationidentified between BMI and change in NRS atany time point.Limitations: This study’s retrospective designinherently leads to a higher risk of selection bias.The sample size was relatively small as a highpercentage of patients were lost to follow-up. Theprimary outcome measure for this study was thechange in mean NRS pain score, and the meanof ordinal data with a nonnormal distribution lacksvalidity in statistical analysis.Conclusions: In this study population, C-RFA ofthe genicular nerves lead to 50% or greater painrelief at 2 weeks and 4-6 weeks postintervention.A 26% pain relief was achieved at 7-33 weeks,but this did not meet the established minimal clinicallyimportant difference cutoff. Two diagnosticgenicular nerve blocks did not improve the rateof treatment success when compared to a singlediagnostic block. BMI does not appear to correlatewith outcomes.Key words: Genicular radiofrequency ablation,genicular RFA, cooled radiofrequency ablation,chronic knee pain, knee osteoarthritis