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Introduction
This retrospective analysis aims to review the effectiveness of cooled radiofrequency ablation (CRFA) for providing relief to patients with chronic knee pain. Our hypothesis is that CRFA will reduce Pain Disability Index (PDI) score, Numerical Pain Rating Scale (NPRS) score and Morphine Equivalent Dose (MED) in the treatment of chronic knee pain.
Methods
Two hundred nineteen patients with knee pain over 3 months who reported at least a 50% improvement in pain after the diagnostic genicular nerve block underwent CRFA of the genicular nerves. These 219 patients excluded any patients with inflammatory conditions, lower limb amputation, depression or pregnancy. One hundred four patients who had PDI, pain and MED scores before and at least 3 months after CRFA were included in the final analysis.
Under fluoroscopy guidance, 17 gauge RF needles were used to target the superior medial, superior lateral and inferior medial genicular nerves at the junction between the femoral or tibial shaft and the epicondyle, respectively, at 50% across the diaphysis. Radiofrequency lesioning was performed for 150 s at 60°C. Then, 1 cc of solution containing 3 cc of bupivacaine 0.25% and 40 mg of triamcinolone acetate was injected through each needle.
Statistical analysis
After normality tests (Shapiro-Wilk and Anderson-Darling showing p<0.03), Wilcoxon signed-rank tests (alpha=0.05) and distribution-free 95% CIs for median change in PDI, pain and MED scores were performed (SAS/STAT V.14.2).
Outcomes
The primary outcome was improvement in PDI scores. The secondary outcomes were pain scores, assessed by NPRS and opioid consumption, assessed by daily MED.
Results
See figure 1 for overview of patients.
Overview of 219 patients reviewed for study. PDI, Pain Disability Index; CRFA, cooled radiofrequency ablation.
The excluded 115 patients had 39 males and 76 females with a minimum age of 22 and maximum age of 89 (mean 67.9 (SD 11.8)). See table 1 for included patients.
Data on included patients
See table 2 for pain and opioid dose outcomes. After CRFA, 67.3% of patients had a decrease in PDI scores with a mean reduction of approximately 31.5%, 27.9% had no change and 4.8% had an increase (p<0.001, 95% CI (−11 to –7)). Ninety-three per cent of patients had a reduction in NPRS scores and approximately 50% of patients had a pain score reduction of 2.2 points. The MED did not change significantly for 80.7% of patients. Postprocedure scores were collected with a median of 169 days and mean of 185 days. No procedure-related serious adverse events were identified on chart review.
Pain and opioid outcomes before and after treatment
Discussion
The PDI score measures the degree to which aspects of a patient’s life are disrupted by chronic pain and the overall impact of pain in a patient’s life.1 2 After CRFA, the majority of patients had a decrease in PDI scores and pain scores despite many patients having other sources of pain contributing to their PDI score. CRFA did not significantly reduce opioid consumption; however, there was not a concerted effort to do so which could have affected results.
Study limitations
Out of 219 patients reviewed, 104 patients were included in the analysis and follow-up times varied. No data were collected on adjunct treatments or comorbidities that may contribute to overall pain. Other limitations include the retrospective nature of the review and small variability of technique among multiple providers.
Conclusion
Our results are comparable with Kapural et al study results indicating improved pain relief without reduction in opioid consumption.3 In addition, our study reports improved disability scores following CRFA. Further research is necessary to analyse the long-term effects of CRFA.
Ethics statements
Footnotes
Contributors MG offered the research question and oversaw the study along with YE. MG and YE guided RK to investigate specific outcomes and supervised findings of the study. RK collected data and wrote the majority of the manuscript with the guidance of all contributing authors. YE and OS reviewed the results and wrote parts of the manuscript. CV verified the analytical methods and performed statistical analysis. All authors discussed the results and contributed to the final manuscript.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.