A randomized controlled study of the long-term efficacy of cooled and monopolar radiofrequency ablation for the treatment of chronic pain related to knee osteoarthritis.

Background: Chronic knee pain due to osteoarthritis (OA) is expected to become more prevalent. Although conventional therapies may provide relief they are not long-lasting. Persistent pain may lead to total knee replacement, which is not free of adverse outcomes. Monopolar and cooled radiofrequency ablation (RFA) of genicular nerves is an effective option. However, either method may provide distinctive results depending on expected lesion size, a key aspect considering the anatomical variability of knee innervations. This prospective, double-blind, randomized controlled trial evaluated the efficacy and durability of knee RFA using a cooled probe or a monopolar probe of comparable diameter. Methods: This investigator-initiated, post-market, double-blinded, prospective, randomized controlled trial was approved by the Western IRB. 79 subjects with chronic knee pain due to knee OA were enrolled in multiple locations of a single center. 75 subjects were randomized (1:1) into RFA treatment with either a 4 ​mm/17G cooled active tip (CRFA) or a 10 ​mm/16G monopolar active tip (MRFA) using conventional procedures. Primary endpoint was change in knee pain level (100 ​mm VAS score) from baseline at 24-week post-treatment. Other endpoints include change in functionality, global perceived effect, and frequency of adverse events. Evaluation spanned to 52-week post-treatment. Significance of results (p ​< ​0.05) was calculated using standard statistical analyses. Results: Both CRFA and MRFA provided significant reduction (41 ​mm and 39 ​mm, respectively) of chronic knee pain at 24-week. At the 52-week visit, reduction in pain level was sustained for CRFA (42 ​mm) but seems to decrease for MRFA (31 ​mm). Improvements in functionality were also significant and sustained with both treatments, although tend to decrease with MRFA at 52-week. Most patients also perceived a very good/good effect of treatments along the duration of the study. Conclusion: RFA of knee genicular nerves for the treatment of OA chronic pain is effective for 52 weeks post-ablation when using a CRFA (4 ​mm/17G active tip) or MRFA (10 ​mm/16G active tip). The benefits of CRFA seems to be better sustained beyond 24 weeks than the ones of MRFA, although no significant differences were observed at 52 weeks.