Knee osteoarthritis is one of the leading causes of pain and disability among aged people. As age advances the morbidity was further scaled up with other associated comorbid conditions. Hence early steps to alleviate the knee pain could benefit the functional improvements and quality of life in those patients. The various non-surgical treatment available for symptomatic knee OA includes weight loss management, physical and aquatic therapy, bracing, non-steroidal anti-inflammatory drugs, intra articular cortisone, hyaluronic acid, PRP injections and finally genicular RF ablation (GNRFA). Among these treatments genicular nerve radiofrequency ablation is targeted to those who have had failure of other conservative treatment and poor candidates for surgery. This new innovative treatment option has the capacity to decrease pain, improve function and thereby improves the quality of life in aged patients. This article narrates the relevant neuroanatomy, procedural approach, effectiveness and safety relating to genicular RFA.
Procedure Description :
The sensory neuroanatomy of the knee joint is relayed through the superior lateral genicular nerve (SLGN), superior medial genicular nerve (SMGN), inferior medial genicular nerve (IMGN), inferior lateral genicular nerve, recurrent fibular nerve, and the infrapatellar branch of the saphenous nerve along with the terminal articular branches of the nerves to the vastus group of muscles. But in genicular nerve block the targeted nerves are only the superior medial genicular nerve, inferior medial genicular nerve, and superior lateral genicular nerve.
Because these three nerves are primarily responsible for sensory supply of knee joint. Two kinds of thermal RFA techniques are available one is conventional RF and recent one is cooled RF.
Thermal GNRFA differs from all other alternative treatment because this procedure causes denaturing of the 3 sensory nerves primarily responsible for transmitting knee pain. Both these ablations use the electrical current produced by radiofrequency waves to destroy a part of nerve tissue thereby creating lesion and relieves pain.
Genicular nerve RFA is a two step procedure. First step is the diagnostic block, which could be performed under guidance of fluoroscopy or ultrasound. By using spinal needle, about 1 -2ml of local anaesthetics are injected around the superior lateral, superior medial, and inferior medial genicular nerve branches. The diagnostic block is extra-articular but the RF procedure is intraarticular. The thermal RFA is performed for those who have positive response with the diagnostic block (i.e., 50% or more reduction in baseline pain for a minimum of 24 hours following the injection).
In the second step, RF needle is placed under fluoroscopic guidance. The radiofrequency waves at the tip of the cannula produces a pre-set heat for a particular time period. This process produces heating and neural denaturation at the particular site(lesion). This created lesion denatures the genicular nerves and decreases the nociceptive signaling from the target tissue. This mechanism produces partial sensory denervation of the joint capsule through targeted delivery of radiofrequency energy to the genicular nerves. Both the procedures are well tolerated in the office setting under local anaesthesia or can be done in the operating room under conscious sedation using a low-dose sedative. In cooled RF ablation (CRFA) probes have a system of water running through the probe tip which produces less damage to the surrounding tissues along with increased area of nerve destruction (larger lesions). This property of CRFA has demonstrated a superior efficacy of pain relief, quality of life and better knee function than the conventional RFA.
GNRFA provides temporary relief from symptomatic OA knee for a period of 6 months to maximum of 12months. Because it doesn’t affect the potential for peripheral nerve regrowth and regeneration. Hence once we noted a successful pain relief with this procedure, it can be safely repeated once in 12months period. Regarding the complications are concerned only minor issues like vascular injuries, infections and neuritis are noted. There is no chance of Charcot joint in GNRFA, because this technique only partially deafferents the knee joint. But the Charcot joint will develop in the context of permanent chronic compromised vascularity as well as in peripheral neuropathy.
In knee osteoarthritis pain treatment modalities, the non-operative management gained substantial interest in last few years. In those modalities the GNRF scores over the others because several RCTs have demonstrated the superiority of GNRF. With these available data and the clinical effectiveness GNRF emerged as an effective treatment for painful OA knee.
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Dr. Karthick Raja.V MD, DA, FIPM
Senior Consultant Anaesthesiologist and Pain Physician
Department of Anaesthesia and Pain Medicine,
Kauvery Hospital, Chennai