Long-term pain relief after genicular nerve cooled radiofrequency ablation in chronic knee osteoarthritis – A prospective observational case study

Background: Osteoarthritis (OA) of the knee is the most frequent progressive degenerative joint disease with a 20% prevalence in India. Many patients with knee OA elect to avoid surgery, and others are poor surgical candidates due to medical comorbidities. Aims: This study aimed to determine 3-, 6-, and 12-month clinical outcomes of genicular nerve cooled radiofrequency ablation (CRFA) for the treatment of chronic pain due to primary knee OA. Study Settings and Design: The present study, a single-armed prospective observational study, was conducted in a tertiary care hospital between March 2020 and December 2021. The genicular nerve CRFA treatments were performed in chronic knee OA patients with a radiological grade of 2 (mild), 3 (moderate), or 4 (severe) (Kellgren and Lawrence system) not responding to conservative therapies for at least 6 months. A total of 70 patients were enrolled in the study. Out of this, 62 patients were finally analyzed for the study. Methods: All the patients received procedural sedation and were placed in the supine position on the operating table. Fluoroscopy-guided CRF genicular nerve ablation was performed using anatomic landmarks at superior lateral, superior medial, and inferior medial sites. Further needle position was confirmed by motor and sensory stimulation. Each target was sequentially lesioned for 2 min and 30 s at a set temperature of 60°C. The average procedure duration was 40 min for the index knee. The patient was discharged on the same day. All patients were followed up in person after 3, 6, and 12 months. Patients answered the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire (96 points) and Numeric Rating Scale (NRS) pain score (0 – no pain and 10 – maximum pain) before the procedure and during each follow-up after treatment. Statistical Analysis: Results were analyzed using Pearson's Chi-square test, Fisher's exact test, and ANOVA as appropriate. P >0.05 was considered statistically significant. Results: The average mean baseline pain score was 9.00 (8.41 ± 0.66) and the mean WOMAC score was 80.00 (80.02 ± 6.92). The pain score (NRS) and WOMAC score at 3-, 6-, and 12-month intervals after postprocedure follow-up were reduced significantly from the baseline level (P < 0.001). Total 91.93% (57/62) of the patients successfully responded (≥50% improvement from the baseline was a good response) to the treatment according to NRS pain score during 3- and 6-month follow-up visits. Then, it was reduced to 77.41% (48/62) during 12 months of follow-up visits. Similarly, the average median WOMAC score was reduced to 25.00 (28.80 ± 10.82), 25.00 (29.35 ± 11.12), and 34.00 (34.96 ± 11.28) during a subsequent follow-up visit at 3, 6, and 12 months. Hence, the response to the cooled radiofrequency treatment was good (≥50% improvement) throughout the study period of 12 months according to the NRS pain score and the global subjective improvement score (WOMAC score). There were a few 11 (17.74%) minor complications, e.g. mild swelling and pain were reported in the immediate postprocedure period. Moreover, only 4 (6.45%) patients had late complication as hypoesthesia over shin bone in our study. Conclusions: CRFA of the genicular nerve in chronic knee OA provides long-term pain relief and improved function for at least a 12-month duration without any significant complications.