Phenol Neurolysis and Radiofrequency Thermocoagulation in Knee Arthroplasty Surgery

140 patients who underwent arthroplasty for chronic knee osteoarthritis will be evaluated in the Algology Department of the Neurology Department at Adnan Menderes University Hospitals between October 2025 and May 2026. Inclusion criteria include patients over the age of 18 who underwent arthroplasty for chronic knee osteoarthritis. Written informed consent will be obtained from all participants. Patients with severe systemic diseases, local infections, or injuries, and those allergic to any of the injection materials will be excluded. All patients will be clinically evaluated (a detailed history, including personal data, medical history, and current treatments). Procedural procedures will be performed in a sterile operating room environment. Patients are positioned supine, and a pillow is placed under the popliteal fossa to support the knee. After visualizing the tibiofemoral joint with fluoroscopy, the potential locations of the geniculate nerves in the medial and lateral regions of the distal femur and medial tibia will be identified with fluoroscopy. After sterile conditions are achieved, local anesthesia is administered both subcutaneously and transcutaneously. A 5 cm long, 5 mm active tip RFT cannula (NeuroThermTM, Medipoint GmbH, Hamburg, Germany) is placed for each geniculate nerve using anteroposterior and lateral fluoroscopy images. For the superior lateral geniculate nerve, it is advanced toward the attachment of the femoral shaft and lateral condyle, for the superior medial geniculate nerve toward the distal femoral diaphysis, and for the inferior medial geniculate nerve toward the proximal tibial diaphysis and medial tibial condyle, ensuring bone contact. The cannula is positioned midline between the diaphysis of the femur and tibia using the lateral image. Sensory stimulation at 50 Hz and motor stimulation at 2 Hz are then applied, followed by a 2 cc 0.5% bupivacaine block for each geniculate nerve. Each cannula is lesioned for 90 seconds using an 80-degree conventional RFT generator (Neurotherm NT1100 / 13001-12).

In the phenol neurolysis group, a 22-gauge, 3.5-inch Quincke needle is advanced toward the junction of the femoral shaft and lateral condyle for the superior lateral genicular nerve; toward the distal femoral diaphysis for the superior medial genicular nerve; and toward the proximal tibial diaphysis and medial tibial condyle for the inferior medial genicular nerve, ensuring bone contact. Lateral imaging confirms the cannula's position in the midline of the diaphysis of the femur and tibia. A mixture of 6 cc of 0.25% bupivacaine and 6% phenol is injected into each geniculate nerve. Post-procedure complications and side effects (infection, bleeding, neurological deficit, etc.) are recorded. Patient response will be determined according to the reduction in pain at follow-up visits at 1, 3, and 6 months after the procedure as follows: good responders will be evaluated as >50% reduction, poor responders will be evaluated as \<50% reduction, or no change will be evaluated as non-responders.