Bipolar Versus Unipolar Intraarticular Pulsed Radiofrequency Thermocoagulation in Chronic Knee Pain Treatment: A Prospective Randomized Trial.

Background: Chronic knee pain is a major widespread problem causing significant impairment of daily function. Pulsed radiofrequency has been shown to reduce severe chronic joint pain as a non-pharmacological and less invasive treatment method.

Objective: We aimed to compare the effectiveness of unipolar and bipolar intraarticular pulsed radiofrequency methods in chronic knee pain control.

Study Design: Prospective, randomized, double-blind study.

Setting: Pain clinic in Cukurova University Faculty of Medicine.

Methods: One hundred patients, aged 20 - 70 years with grade 2 or 3 knee osteoarthritis were included in this study. Patients were randomly allocated into 2 groups to receive either unipolar (group U, n = 50) or bipolar (group B, n = 50) intraarticular pulsed radiofrequency (IAPRF) with a 45 V voltage, 2 Hz frequency, 42° C temperature, 10 msec pulse width, and 10 minute duration. We recorded visual analog scale (VAS) and Western Ontario and McMaster Universities Osteoarthritis Index LK 3.1WOMAC (Western Ontario and McMaster Universities Osteoarthritis Index LK 3.1) scores of patients at baseline and one, 4, and 12 weeks after the procedure. The primary outcome was the percentage of patients with ≥ 50% reduction in knee pain at 12 weeks after the procedure.

Results: There was a significant difference between the groups according to VAS scores at all post-intervention time points. In group B, 84% of patients, and in the group U, 50% of patients achieved at least 50% knee pain relief from the baseline to 3 months. In group B, WOMAC scores were significantly lower than the group U at one and 3 months.

Limitations: Lack of long-term clinical results and supportive laboratory tests.

Conclusion: Bipolar IAPRF is more advantageous in reducing chronic knee pain and functional recovery compared with unipolar IAPRF. Further studies with longer follow-up times, laboratory-based tests, and different generator settings are required to establish the clinical importance and well-defined mechanism of action of PRF. This study protocol was registered at clinicaltrials.gov (identifier: NCT02141529), on May 15, 2014. Institutional Review Board (IRB) approval date: January 16, 2014, and number: 26/9Key words: Chronic pain, intraarticular, knee joint, knee osteoarthritis, pain management, pulsed radiofrequency treatment, quality of life, recovery of function.