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pISSN 2005-9159
eISSN 2093-0569

Letter to the Editor

Korean J Pain 2025; 38(1): 81-84

Published online January 1, 2025 https://doi.org/10.3344/kjp.24312

Copyright © The Korean Pain Society.

Genicular nerve radiofrequency ablation: proposal of a technical protocol for managing procedural pain

Andrés Rocha-Romero1 , Tony Kwun Tung Ng2,3,4,5,6 , Guilherme Ferreira-Dos-Santos7

1Department of Anesthesia and Pain Medicine, National Rehabilitation Center, San José, Costa Rica
2Department of Anaesthesia and Intensive Care, The Chinese University of Hong Kong, Hong Kong, China
3Department of Anaesthesia, Boxhill Hospital, Melbourne, Australia
4Frankston Pain Management, Melbourne, Australia
5Department of Anaesthesia and Operating Theatre Services, Tuen Mun Hospital, Tuen Mun, Hong Kong
6Center for Regional Anesthesia and Pain Management, Wan Fang Hospital, Taipei Medical University, Taipei, Taiwan
7Division of Pain Medicine, Department of Anesthesiology, Reanimation, and Pain Medicine, Hospital Clínic de Barcelona, University of Barcelona, Barcelona, Spain

Correspondence to:Andrés Rocha-Romero
Department of Anesthesia and Pain Medicine, National Rehabilitation Center, Uruca 37th Av, Alborada, San José 10107, Costa Rica
Tel: +506 2232 8233, Fax: +5062232 8233, E-mail: rocharomeroandres@gmail.com

Handling Editor: Seong-Soo Choi

Received: September 20, 2024; Revised: November 1, 2024; Accepted: November 12, 2024

This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/), which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

The authors of this letter read with great interest the recent work by Karm et al. [1], a review updating radiofrequency denervation for arthritis-related knee joint pain, which comprehensively covered the topic. Nonetheless, a crucial issue that has not been adequately addressed in the literature to date is the pain associated with the procedure. Albeit current ultrasound-guided genicular nerve ablation protocols [2], performed for 90 seconds at 80 degrees Celsius, have been demonstrated to be clinically effective in treating chronic joint pain in patients with advanced knee osteoarthritis, these protocols typically target only the medial superior genicular nerve, medial inferior genicular nerve, and lateral superior genicular nerve [14]. This limited targeting has led some authors to suggest that achieving effective coverage may require more extensive lesions, as demonstrated in recent preliminary studies employing cooled radiofrequency or chemical ablation [5,6]. However, more extensive lesions may increase the risk of adverse effects that require careful management [7].

Despite its efficacy, a standardized protocol for genicular nerve radiofrequency treatment remains elusive. Various authors have reported the use of conventional radiofrequency ablation, cooled radiofrequency, and even chemical denervation with similar results [5,6]. Additionally, the authors’ understanding of knee joint innervation has evolved, leading some practitioners to recommend five or more lesions for patients unresponsive to the traditional three-target approach [6,8]. Consequently, personalized approaches rather than standardized protocols have been proposed [3,6].

Another critical consideration is managing procedural pain, particularly in patients with chronic joint pain who may have developed peripheral sensitization. While some studies reported no use of sedation [2,5], the authors’ clinical experience suggests that the insertion of 17-gauge introducers for cooled radiofrequency procedures is often painful, even under local anesthesia. Most of the pain associated with the genicular nerve radiofrequency technique is primarily caused not by the ablation itself, but by the introduction of the cannulas into the skin. Currently, there are only two alternatives to manage this type of procedural pain: sedation, which carries risks associated with patient comorbidities and prevents patient feedback if sensory stimulation is desired, or subcutaneous infiltration of local anesthesia, which can alter stimulus interpretation, double the number of injections, and sometimes be insufficient, requiring repeat infiltration. The emerging role of procedural pain, anxiety, and stress in pain perception during this procedure has also driven the search for new alternatives, such as the implementation of virtual reality technologies [9].

The anterior femoral cutaneous nerve (AFCN) includes both the intermediate femoral cutaneous nerve (IFCN) and the medial femoral cutaneous nerve (MFCN) (Fig. 1). The MFCN innervates the distal medial thigh and the anteromedial region of the knee, while the IFCN innervates the distal anterior thigh [10].

Figure 1. Sonoanatomy and schematic diagrams illustrate the relationships between the branches of the anterior femoral cutaneous nerve (AFCN), the nerve to vastus medialis (NVM), the saphenous nerve, and the lateral femoral cutaneous nerve. For the block: The patient is positioned supine with the knee slightly flexed. Using a high-frequency linear transducer, the saphenous nerve is identified at the level of the apex of the femoral triangle. An in-plane, low-volume (around 3 mL) block is administered using an equal mixture of lidocaine with epinephrine and bupivacaine, carefully avoiding spread to the NVM. Before withdrawing the needle, the AFCN, including its medial and intermediate branches, is targeted above the sartorius muscle with a low-volume block of the same local anesthetic mixture. Time is allowed for the local anesthetic to take effect while the rest of the radiofrequency ablation setup is prepared. A: anterior, M: medial, P: posterior, L: lateral.

The efficacy of AFCN blocks has been previously described in managing incisional pain following knee arthroplasties. This technique provides the added advantage of facilitating blockade of the saphenous, medial femoral cutaneous (anterior branch), and intermediate femoral cutaneous nerves usually with a single skin puncture [10]. In the authors’ approach, at the apex of the femoral triangle, the focus is exclusively on blocking the saphenous nerve to prevent motor blockade, achieved by excluding the nerve to the vastus medialis. This nerve is located outside the adductor canal, residing instead within a separate fascial tunnel along the medial vastus muscle [11].

Blocking these nerves before genicular nerve ablation offers several advantages: (a) significant improvement in patient comfort as the anesthetized area is larger than the actual injury; (b) prolonged analgesic efficacy compared to subcutaneous infiltration of local anesthetic, as the medication is injected directly to the nerves innervating not only the skin but also the underlying fascia lata; (c) reduction in the number of required punctures to cover a larger area compared to subcutaneous infiltration of local anesthetic; (d) minimal interference with sensory stimulation, except potentially for the infrapatellar branch of the saphenous nerve; (e) no risk of motor blockade since all targeted nerves are purely sensory.

In the authors’ clinical experience, incorporating AFCN and saphenous nerve blocks (in case the infrapatellar branch of saphenous nerve is not targeted) significantly reduces procedure-related pain and discomfort, particularly in patients requiring more than three ablations with large introducers (17G or larger) or in cases where sedation is not an option. Our suggested regime would be 2 mL 1% lignocaine to the AFCN, 3 mL 1% lignocaine to the saphenous nerve. The primary limitation of this technique is the challenge of visualizing these small nerves, which requires specialized training. Although time is allotted for the local anesthetic to take effect during the setup for radiofrequency ablation, the additional time required for this step, along with the associated costs, should be considered potential limitations.

We also recommend blocking the lateral femoral cutaneous nerve (LFCN) at the groin level (Fig. 1), as attempting to block it at the thigh level may be ineffective due to extensive branching, making it difficult to anesthetize the lateral side. Our suggested regime is 2 mL 1% lignocaine to the fat-filled fat tunnel.

We consider this topic essential, as procedural pain remains a significant challenge that must be acknowledged and effectively managed. Future research is warranted to explore the optimal approach for procedural pain control in genicular nerve radiofrequency ablation.

The authors would like to express their sincere gratitude to Maria Fernanda Rojas for her invaluable contribution in creating the illustrations used in this study. Her artistic skills and attention to detail greatly enhanced the visual quality of this paper.

Data sharing is not applicable to this article as no datasets were generated or analyzed for this paper.

No potential conflict of interest relevant to this article was reported.

Andrés Rocha-Romero: Study conception; Tony Kwun Tung Ng: Formal analysis; Guilherme Ferreira-Dos-Santos: Methodology.

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