Pulsed Radiofrequency Neuromodulation for the Treatment of Saphenous Neuralgia
A 65-year-old male presented with severe pain and a tingling sensation in the right medial knee, calf, and ankle. He walked with a limp due to pain but and not weakness. The patient had experienced severely disabling conditions for over 1 month. The pain and tingling sensation occurred every 5-10 minutes and lasted more than 5 minutes per episode. A neurological examination was normal, except for severe pain and tingling sensation in the right medial knee, calf, and ankle.\nLumbar magnetic resonance imaging (MRI) revealed no acute lesions except for distal degenerative changes at multiple levels. Knee MRI revealed no acute lesion except for mild degenerative osteoarthritis. A nerve conduction study revealed an absence of a right saphenous response in both the medial leg and the infrapatellar region, while normal findings were recorded from the left side. Electromyography was normal for all muscles tested. Before visiting our outpatient clinic, the patient had undergone a variety of treatments, including medication, an intra-articular injection for knee pain, and acupuncture around the right knee and medial calf. However, his symptoms did not improve but instead progressed. Saphenous nerve blocks using a local anesthetic and steroids were performed twice at 1-week intervals with fluoroscopy in our clinic. The target sites of nerve blocks were two point, the saphenous nerve around adductor's canal and the sartorial branch of the saphenous nerve around superficial saphenous vein. These blocks provided temporary pain relief that lasted about 3 days. After the positive results of the diagnostic nerve blocks, the patient was scheduled for PRF neuromodulation of the saphenous nerve.\nWe performed fluoroscopically guided selective saphenous nerve PRF using a model NT1000 radiofrequency generator (NeuroTherm, Middleton, MA, USA). In the operating room, the patient was supine, with the right leg positioned with hip external rotation, hip abduction, and knee flexion. We drew a hypothetical line for the saphenous nerve (complete nerve, infrapatellar branch, and sartorial branch) and the trajectory for the cannula on his leg (). The target site was prepped with betadine and aseptically draped, and the right knee joint and epicondyle were identified under C-arm fluoroscopy. Disposable 20-gauge, 10-cm radiofrequency cannulas (Model S-1505; NeuroTherm) with a 5-mm active tip were inserted at the level of the adductor's canal and below the epicondyle. The introducer needles were withdrawn, and a Model RFDE-15 disposable radiofrequency electrode (NeuroTherm) was advanced ().\nSelective stimulation of the sensory fibers (50 Hz) showed concordant pain between 0.3-0.5 V, which confirmed proper localization of the PRF electrode. Motor stimulation was negative. After stimulation, PRF neuromodulation was performed for 240 pulses. The maximal temperature was 42℃. After the procedure, the pain measured on a visual analog scale had decreased by 90% without medication. The pain relief was maintained for 6 months of follow-up without medication.