Sir,
Knee osteoarthritis (OA) is a leading cause of disability; it has been estimated that in the United States nearly one-tenth of the adults are affected by such condition with an expected radiographic prevalence >37%/year [Citation1]. Clinically, knee OA presents with pain, limited range of motion, stiffness, osteophytes and effusions. Accordingly, patients’ quality of life is significantly impaired. Common treatments include conservative approaches (i.e. weight loss, physical therapy, analgesic drugs), intra-articular injections and, for advanced cases, total knee arthroplasty (TKA).
Radiofrequency ablation (RFA) is a relatively novel percutaneous technique, which has been widely applied for the treatment of several different medical conditions including cancers [Citation2–4] and cardiac arrhythmias [Citation5]. More recently, RFA has also been applied to treat chronic pain originating form benign conditions (e.g. radiculopathic pain) [Citation6,Citation7] or from skeletal metastases [Citation8].
From a physical point of view, RFA induces ionic agitation resulting into tissue heating through the application of an electrical current flowing between two dipoles. Basically, three different monopolar RFA techniques are available including conventional RFA, cooled RFA and pulsed RFA. With conventional RFA, ionic agitation is achieved in order to obtain tissue charring and carbonisation at temperatures >60 °C [Citation6,Citation9]. On the other hand, when the shaft of the electrode is continuously cooled with cold saline, high temperatures at the interface between the electrode and the target tissue are prevented, thus avoiding charring and carbonisation. Accordingly, heating can spread homogeneously into the tissue and larger areas of ablations are obtained as compared to conventional RFA. In the end, pulsed RFA produces short (20 milliseconds) pulses of low-amplitude (45 V) every 500 milliseconds. As a consequence, the target tissue is minimally warmed (<42 °C) without any definitive structural change. Nevertheless, it has been largely proved that pulsed RFA results into neuromodulation, which is responsible for the palliative effect [Citation7,Citation10].
In the particular setting of knee OA, all these three RFA techniques have been safely and successfully applied to treat chronic pain; and a large literature core supports RFA with very encouraging results reported both at short- and mid-term follow-up (ranging between 1 week and 12 months) [Citation11]. However, a substantial heterogeneity exists across studies, especially in terms of ablative protocols, imaging guidance and anatomic targets of the ablation. Despite such heterogeneity, most of the available papers reported about US/fluoroscopy guidance applied to target the genicular nerves [Citation11]. Nevertheless, at the moment, it is not possible to state whether one approach/technique is superior to another. Moreover, data about the long-term efficacy of the technique are substantially lacking; and it is not clear whether and how RFA should be combined with other non-surgical treatments such as articular injections.
In conclusion, a large literature core supports RFA as an effective palliative method for patients suffering from painful chronic OA of the knee non-responding to conservative measures. Nevertheless, a standardisation of the technique is needed to allow definitive acceptance of RFA in the armamentarium of treatments available for knee OA.
Disclosure statement
Authors have no conflict of interests to disclose.
Funding
The present paper received no funding.
References
- Guccione AA, Felson DT, Anderson JJ, et al. (1994). The effects of specific medical conditions on the functional limitations of elders in the Framingham Study. Am J Public Health 84:351–8.
- Cazzato RL, Garnon J, Ramamurthy N, et al. (2016). 18F-FDOPA PET/CT-guided radiofrequency ablation of liver metastases from neuroendocrine tumours: technical note on a preliminary experience. Cardiovasc Intervent Radiol 39:1315–21.
- Cazzato RL, Buy X, Alberti N, et al. (2015). Flat-panel cone-beam CT-guided radiofrequency ablation of very small (≤1.5 cm) liver tumors: technical note on a preliminary experience. Cardiovasc Intervent Radiol 38:206–12.
- Kim HJ, Park BK, Park JJ, Kim CK. (2016). CT-guided radiofrequency ablation of T1a renal cell carcinoma in Korea: mid-term outcomes. Korean J Radiol 17:763–70.
- Raatikainen MJ, Hakalahti A, Uusimaa P, et al. (2015). Radiofrequency catheter ablation maintains its efficacy better than antiarrhythmic medication in patients with paroxysmal atrial fibrillation: on-treatment analysis of the randomized controlled MANTRA-PAF trial. Int J Cardiol 198:108–14.
- Kapural L, Mekhail N. (2001). Radiofrequency ablation for chronic pain control. Curr Pain Headache Rep 5:517–25.
- Bogduk N. (2006). Pulsed radiofrequency. Pain Med 7:396–407.
- Dupuy DE, Liu D, Hartfeil D, et al. (2010). Percutaneous radiofrequency ablation of painful osseous metastases: a multicenter American College of Radiology imaging network trial. Cancer 116:989–97.
- Choi WJ, Hwang SJ, Song JG, et al. (2011). Radiofrequency treatment relieves chronic knee osteoarthritis pain: a double-blind randomized controlled trial. Pain 152:481–7.
- Cahana A, Van Zundert J, Macrea L, et al. (2006). Pulsed radiofrequency: current clinical and biological literature available. Pain Med 7:411–23.
- Gupta A, Huettner DP, Dukewich M. (2017). Comparative effectiveness review of cooled versus pulsed radiofrequency ablation for the treatment of knee osteoarthritis: a systematic review. Pain Physician 20:155–71.