Sage Journals: Discover world-class research

Abstract

BACKGROUND:

Monopolar radiofrequency ablation (MRFA) of the genicular nerves has been considered the main interventional treatment for chronic knee pain. However, the variable locations of these nerves could suggest that traditional MRFA of genicular nerves may be insufficient to cover the area needed to provide complete sensory denervation. For these reasons, some alternatives have been proposed to achieve an increase in the lesion area that offers better outcomes such a bipolar radiofrequency ablation (BRFA).

OBJECTIVE:

To describe the efficacy and safety of the bipolar radiofrequency ablation (BRFA) of the genicular nerves in the patients with chronic knee pain.

METHODS:

A retrospective study was conducted in the Pain Medicine Department. Institutional review board approval from the Hospital Ethical Committee and informed consent were obtained. We reviewed our database for BRFA of genicular nerves from January 2018 to December 2021 for patients with chronic knee pain. The cannulas were placed using ultrasound guidance (10 cm, 22-gauge and 10 mm active curved tip), and each pair of cannulas were subjected to BRFA for 90 seconds at 80 ${}^{\circ}$ C. Data analysis was conducted using T-test for paired variables (Visual analogue scale and EuroQol, an instrument intended to complement other forms of quality-of-life measures).

RESULTS:

Twenty-five patients met inclusion criteria after excluding 7 based on the study design. The mean improvement of our patients according to the VAS was $-$ 3.98 (95%CI: $-$ 4.37 to $-$ 3.59) $p<$ 0.0001 and EuroQol $+$ 0.416 (95%CI: 0.364 to 0.468) $p<$ 0.0001. The mean duration of improvement was 8 (6–11) months after BRFA. There were no reported serious adverse events related to the procedure, only local pain for 24 to 48 hours in 3 patients.

CONCLUSIONS:

We can conclude that BRFA reduces procedural pain and increases the treatment area, providing more complete sensory denervation and improved clinical outcomes.

Keywords

Chronic knee pain bipolar radiofrequency radiofrequency ablation genicular nerves ultrasound guidance procedure

1. Introduction

Chronic knee pain is a common cause of disability in adults and poor quality of life [1]. Many therapeutic options have been used to manage this symptom, such as local anesthetics and corticosteroid injections, hyaluronic acid, platelet-rich plasma, ozone, and botulinum toxin [2, 3, 4].

Monopolar radiofrequency ablation (MRFA) of the genicular nerves has been considered the main interventional treatment for chronic knee pain. Several reports have demonstrated its effectiveness in reducing pain and improving knee functionality [5, 6, 7]. However, the traditional technique can be painful and difficult due to the need for repetitive needle repositioning to obtain correct sensory stimulation, which is associated with vascular lesions in 24-40% [8].

Nowadays, ultrasound is widely used as guidance for diagnosis and treatment. With ultrasonography, the localization of genicular arteries and nerves at the junction of epiphysis and diaphysis (near periosteum) on the medial and lateral aspects of the lower end of the femoral bone and on the medial aspect of the proximal tibia next to their genicular arteries is not difficult, being more accurate and preventing vascular lesions. Several studies have demonstrated similar or better clinical results compared to fluoroscopy-guided treatment [9, 10, 11].

However, the variable locations of these nerves and the additional accessory articular nerves could suggest that traditional MRFA of genicular nerves may be insufficient to cover the area needed to provide complete sensory denervation [12, 13, 14]. For these reasons, some alternatives have been proposed to achieve an increase in the lesion area that offers better outcomes, such as Cooled-RFA, three-tined RFA electrode, or bipolar radiofrequency ablation (BRFA). BRFA is a system formed by two active electrodes separated by less than 20mm for 18G needles, where the dispersion plate does not intervene. The electric area is concentrated between the active electrodes, increasing the treatment area more than MRFA with homogeneous lesions, providing more complete sensory denervation [15]. In this study, we aimed to describe the efficacy and safety of the BRFA of genicular nerves in patients with chronic knee pain.

2. Material and methods

This was a retrospective study conducted through chart review at the Pain Medicine Department. Institutional review board approval was obtained from the Ethical Committee of University General Hospital of Ciudad Real (IRB 12/2018), and informed consent was obtained from all individuals included in this study.

2.1 Patient cohort

We reviewed our database for all cases of BRFA of genicular nerves from January 2018 to December 2021 on patients with chronic knee pain (post-arthroplasty and osteoarthritis). Patients who received any changes to their treatment that could alter the result of the BRFA, and/or were not documented in their medical records used for the study variables were excluded.

The grade of osteoarthritis was classified according to the Kellgren and Lawrence system:

Grade 0 (none): definite absence of X-ray changes of osteoarthritis.

Grade I (doubtful): doubtful joint space narrowing and possible osteophytic lipping.

Grade II (minimal): definite osteophytes and possible joint space narrowing.

Grade III (moderate): moderate multiple osteophytes, definite narrowing of joint space and some sclerosis and possible deformity of bone ends.

Grade IV (severe): large osteophytes, marked narrowing of joint space, severe sclerosis and definite deformity of bone ends.

2.2 Interventional procedure

Figure 1.

Ultrasound location of genicular arteries using color Doppler (superior medial, superior lateral, and inferior medial). Each nerve is located near its respective artery, allowing for safer and more accurate injection targeting.

Figure 2.

RFA needle positions for BRFA: Two cannulas were placed in each nerve area, first near the genicular artery, and then the second cannula was placed approximately 10 mm from the first one (proximal to the superior-lateral and superior-medial genicular nerve, and distal to the inferior-medial genicular nerve). The fluoroscopy image shows the anteroposterior (A-P) and lateral views with six cannulas, two for each target point.

Table 1

Baseline demographic, clinical, and procedural characteristics of genicular nerve BFRA ( $n=$ 25 procedures)

Variables	Frequency	Mean (standard deviation)
Sex
Female	20 (80)
Male	5 (20)
Age (years)		79.44 $\pm$ 9.07
BMI		30.06 $\pm$ 3.74
Diagnostics
Osteoarthritis	19 (76)
Painful prosthesis	6 (24)
Osteoarthritis grade K&L
I	0 (0)
II	2 (10.5)
III	9 (47.4)
IV	8 (42.1)
Pain chronicity (years)		6.23 $\pm$ 3.64
Baseline VAS		8.36 $\pm$ 0.57
Baseline EuroQol		0.184 $\pm$ 0.054
Procedure indication
Improvement $<$ 30% on previous MRFA	14 (56)
Destructuring of the area	6 (24)
Pacemaker	5 (20)
Post-procedure VAS		4.38 $\pm$ 0.74
VAS improvement	21 (84)
Pose-procedure EuroQol		0.601 $\pm$ 0.0115
Improvement time (months)		8.14 $\pm$ 1.46
Complications after the procedure	3 (12)

BRFA $=$ bipolar radiofrequency ablation, BMI=body mass index, K&L $=$ Kellgren and Lawrence score, VAS $=$ visual analogue score, MRFA $=$ monopolar radiofrequency ablation.

Table 2

Characteristic of each patient, the indication of procedure, pain VAS and EuroQol baseline and change from baseline to follow-up after genicular nerve bipolar radiofrequency ablation

Patient	Knee	TKA	Indications	Baseline VAS	Baseline EuroQol	Post-procedure VAS	Post-procedure EuroQol	Adverse events
1	Right	No	Pacemaker	8	0.273	5	0.604	None
2	Bilaterally	No	Improvement $<$ 30% on previous MRFA	8	0.218	8	0.218	Local pain $<$ 48 hours
3	Left	No	Destructuring of the area	9	0.115	4	0.594	None
4	Right	No	Pacemaker	8	0.218	5	0.594	None
5	Left	No	Improvement $<$ 30% on previous MRFA	8	0.218	4	0.485	None
6	Right	No	Improvement $<$ 30% on previous MRFA	8	0.273	5	0.485	None
7	Left	No	Improvement $<$ 30% on previous MRFA	8	0.122	4	0.752	None
8	Left	No	Pacemaker	9	0.17	5	0.594	None
9	Left	No	Improvement $<$ 30% on previous MRFA	9	0.17	5	0.659	None
10	Right	No	Pacemaker	9	0.122	5	0.659	None
11	Bilaterally	No	Improvement $<$ 30% on previous MRFA	8	0.215	8	0.215	None
12	Right	No	Improvement $<$ 30% on previous MRFA	8	0.215	3	0.79	None
13	Left	No	Destructuring of the area	9	0.115	5	0.429	Local pain $<$ 48 hours
14	Right	No	Destructuring of the area	9	0.115	9	0.115	Local pain $<$ 48 hours
15	Bilaterally	No	Improvement $<$ 30% on previous MRFA	9	0.115	5	0.493	None
16	Left	No	Pacemaker	8	0.218	4	0.429	None
17	Left	No	Improvement $<$ 30% on previous MRFA	8	0.115	4	0.594	None
18	Left	No	Improvement $<$ 30% on previous MRFA	8	0.215	5	0.594	None
19	Right	No	Destructuring of the area	8	0.17	5	0.604	None
20	Right	Yes	Improvement $<$ 30% on previous MRFA	7	0.273	4	0.429	None
21	Right	Yes	Improvement $<$ 30% on previous MRFA	9	0.222	3	0.79	None
22	Right	Yes	Improvement $<$ 30% on previous MRFA	9	0.222	3	0.79	None
23	Right	Yes	Destructuring of the area	8	0.17	4	0.659	None
24	Left	Yes	Destructuring of the area	8	0.218	5	0.594	None
25	Right	Yes	Improvement $<$ 30% on previous MRFA	9	0.115	9	0.115	None

VAS $=$ visual analogue score of pain, TKA $=$ total knee arthroplasty, MRFA $=$ monopolar radiofrequency ablation.

The procedure was performed on outpatients who had a positive diagnostic genicular nerve block ( $>$ 50% pain reduction). Patients were monitored and positioned in a supine position with the knee supported by a small pillow placed beneath the popliteal fossa. First, the location of genicular arteries/nerve (superior medial, superior lateral and inferior medial) was determined using ultrasound and marked (Fig. 1). The lower femoral and upper tibial regions were prepared in a sterile manner. Local anesthesia was administered through subcutaneous 1% lidocaine injections, and conscious sedation (midazolam 1–2 mg IV) and supplemental nasal cannula oxygen were administered. The linear probe (4–15 MHz) of the ultrasound device Sonosite PX was used, and a cannula (A 10 cm, 22-gauge with a 10 mm active curved tip) was placed in the nerve area near to genicular artery. Then, a second cannula was placed approximately 10 mm near the first one (proximal to superior-lateral and superior-medial genicular nerve and distal to inferior-medial genicular nerve). Finally, the correct location was confirmed by fluoroscopy (Fig. 2). A radiofrequency (RF) electrode was placed into each cannula. Sensory stimulation was tested and captured at 50 Hz, 0.4–0.7 V with one or both other cannulas without requiring manipulation. Once the location was confirmed, each pair of cannulas (superior medial, superior lateral and inferior medial) underwent BRFA for 90 seconds at 80 ${}^{\circ}$ C, completing two cycles (Cosman G4 device). After the treatment, a 0.25% levobupivacaine and corticoids (betamethasone phosphate 6mg/betamethasone acetate 6mg) were injected.

2.3 Clinical outcome measures

The Improvement of visual analogue scale (VAS) ranging from 1 to 10 (0 $=$ no pain, 1–4 $=$ mild pain, 5–7 $=$ moderate, 8–10 $=$ severe pain), EuroQol (an instrument intended to complement other forms of quality-of-life measures), and the occurrence of adverse events were recorded in the clinical records of subsequent visits.

2.4 Statistical analysis

Quantitative variables were presented as mean and standard deviation, and qualitative variables were presented as number and percentages. T-test for paired variables (VAS and EuroQol) was used for quantitative variable analysis, as this data was normally distributed. The odds ratio (OR) was calculated to assess the association between clinical variables and the improvement of outcomes. A significance level of 95% ( $p=$ 0.05) was considered. The SPSS 18.0 statistical package was used.

3. Results

Thirty-two patients were studied after excluding 7 subjects based on study design, as they had received changes to their treatment or did not have complete information in their medical records. The final analysis was performed with 25 patients. The average age was 79.44 $\pm$ 9.07 years (80% female) with a baseline VAS 8.36 $\pm$ 0.57 and EuroQol 0.184 $\pm$ 0.054. Seventy-six percent had osteoarthritis (47.4% grade III and 42.1% grade IV). Other baseline demographic, clinical, and procedural characteristics are shown in Table 1.

BRFA was indicated in patients with pacemakers, those who had less than 30% pain reduction with genicular nerve MRFA (a non-significant improvement was defined by the research group as a reduction of less than 30% in the VAS or an increase of less than 30% in the EuroQol compared to the baseline), or in those who had severe destruction of the femorotibial area that made it difficult to correctly locate the geniculate artery/nerve by ultrasound and/or fluoroscopy (Table 2).

Table 3
Global response to interventional treatment

	Baseline	Post-procedure	$t$ student
VAS	8.36 $\pm$ 0.57	4.38 $\pm$ 0.74	$-$ 3.98	(CI95%: $-$ 4.37 a $-$ 3.59)
			$P<$ 0.0001
EuroQol	0.184 $\pm$ 0.54	0.601 $\pm$ 0.115	$+$ 0.416	(CI95%: 0.364 a 0.468)
			$P<$ 0.0001

VAS $=$ visual analogue score.

Eighty-four percent of the patients showed a VAS reduction of at least 3 points, and 16% showed a reduction of 5 points. The mean improvement according to the VAS was $-$ 3.98 (95%CI: $-$ 4.37 to $-$ 3.59, $p<$ 0.001) and EuroQol $+$ 0.416 (95%CI: 0.364 to 0.468, $p<$ 0.001) (Table 3). In the odds ratio analysis, it was not possible to determine if any of the variables studied (age, diagnosis, Kellgren and Lawrence scoring system, or pain chronicity) correlated with better clinical outcome. The mean duration of improvement was 8 (6–11) months after BRFA. There were no serious adverse events related to the BRFA, only 3 patients reported local pain in the site of injection for 24 to 48 hours after the procedure.

4. Discussion

MRFA of the genicular nerves is a current interventional treatment used for chronic knee pain [5, 6, 7]. Some authors have demonstrated an improvement of 88–95% in the first month, which can be maintained for up to 6 months, while in other series, the improvement drops to 64%. Recently published studies have claimed that this procedure can achieve functional improvement and analgesic effect lasting between 3 and 12 months [16]. This variability is explained by the different anatomical variants found in clinical practice. The localization of genicular nerves as a therapeutic target poses a challenge for the physicians performing this procedure [14]. Currently, there are published articles advocating for the use of ultrasound in this process because it is possible to identify the genicular artery using color Doppler ultrasound and locate the nerve in close proximity [10, 11]. However, it is still difficult to accurately place the needles to obtain the best outcomes. For all these reasons, several alternatives have been proposed to increase the lesion area and achieve better outcomes.

In 2017, McCormick et al. described a clinical improvement in thirty-three patients of 50% or greater reduction in Pain Numeric Rating Scale, who had undergone genicular nerve Cooled-RFA for chronic knee pain for more than six months. Nearly 20% of patients experienced complete relief of pain [17]. In 2020, Koshie et al described a novel protocol utilizing a three-tined RFA electrode to target the superomedial (SMGN), superolateral (SLGN), and inferomedial genicular nerves (IMGN) in eleven patients. The study demonstrated the best outcomes and locations of these specific nerves, as well as additional articular nerves, with a reduction of 50–80% in Pain Numeric Rating Scale at six months [18].

This study investigated the clinical outcomes of patients who underwent genicular nerve BRFA for the treatment of chronic knee pain using ultrasound and fluoroscopic guidance. The use of BRFA is widely described in the literature for other joints with good outcomes, as it increases the treatment area by using two or more needles [19]. There are very few published articles on the use and effectiveness of BRFA on the genicular nerve. In 2015, Jadon described, for the first time, two cases, in which BRFA of the genicular nerve was used in patients with a permanent pacemaker. Both subjects experienced effective pain relief with 60% pain reduction until the 3rd month (VAS 9/10 to 3–4/10) and 40% reduction at the end of the 6th month (VAS 9/10 to 5/10), without any technical difficulties or complications [20]. In 2018, another study was published that compared monopolar ( $n=$ 15) and bipolar ( $n=$ 15) radiofrequency ablation of genicular nerves in chronic knee pain due to osteoarthritis. The study described that BRFA has similar analgesic efficacy but significantly less procedural pain when compared to MRFA, with a Numeric Rating Scale for pain of 3/10 vs 5/10, respectively [21].

In our research, the clinical improvement after the procedure resulted in a reduction of VAS by $-$ 3.98 and an increase in EuroQol-5D by $+$ 0.416 until 11 months after treatment, with fewer complications, only experiencing local pain for 24–48 hours post procedure. These results may be attributed to the technique increasing the probability of genicular nerve ablation without requiring additional manipulation.

4.1 Limitations

Although the results demonstrated good effectiveness of the procedures, it is important to note that this study is descriptive and retrospective in nature. Therefore, we cannot generalize our findings. However, these results provide a foundation upon which we can design a prospective, randomized and controlled study. Such a study would allow us to determine the impact of these procedures on the patients in a real-world context, using the variables that were studied.

5. Conclusions

In our study, we observed an improvement in 84% of patients, with an average reduction of 53% in the VAS (8.36 to 4.38), and an increase of 42% in the EuroQol (0.184 to 0.601), with mean duration of improvement of 8 (6–11) months. Although the efficacy of BRFA in genicular nerves has only been described in some case reports with a few patients, this study concludes that BRFA could be a new alternative technique that increases the treatment area, providing more complete sensory denervation. It shows equal or better effectiveness than current techniques (64–88% MRFA, 50% Cooled-RFA, 50-80% three-tined RFA electrode) and less pain throughout the procedure.

Funding

The authors declare that they have not received any type of funding to carry out the study.

Author contributions

This study was done with the equal participation of all authors.

Ethical statement

The authors of this study have followed ethical research guidelines.

Informed consent

Informed consent was designed and obtained from all individuals included in this study.

Footnotes

Acknowledgments

The authors thank the Ciudad Real pain unit for all the dedication, effort, and teamwork.

Conflict of interest

The authors have no conflicts of interest to declare.

References

Hunter

Riordan

. The impact of arthritis on pain and quality of life: an Australian survey. Int J Rheum Dis. 2014; 17(2): 149-55.

Bennell

Hunter

Hinman

. Management of osteoarthritis of the knee. BMJ. 2012; 345(2): e4934-e4934.

Duymus

Mutlu

Dernek

Komur

Aydogmus

Kesiktas

. Choice of intra-articular injection in treatment of knee osteoarthritis: platelet-rich plasma, hyaluronic acid or ozone options. Knee Surg Sports Traumatol Arthrosc. 2017; 25(2): 485-92.

Singer

Silbert

Singer

. The Role of Botulinum Toxin Type A in the Clinical Management of Refractory Anterior Knee Pain. Toxins. 2015; 7(9): 3388-404.

Iannaccone

Dixon

Kaufman

. A Review of Long-Term Pain Relief after Genicular Nerve Radiofrequency Ablation in Chronic Knee Osteoarthritis. Pain Physician. 2017; 20(3): E437-E444.

Konya

Akin Takmaz

Başar

Baltaci

Babaoğlu

. Results of genicular nerve ablation by radiofrequency in osteoarthritis-related chronic refractory knee pain. Turk J Med Sci. 2020 Feb 13; 50(1): 86-95.

Fogarty

Burnham

Kuo

Tate

Sperry

Cheney

, et al. The Effectiveness of Fluoroscopically Guided Genicular Nerve Radiofrequency Ablation for the Treatment of Chronic Knee Pain Due to Osteoarthritis: A Systematic Review. Am J Phys Med Rehabil. 2022 May 1; 101(5): 482-492.

Kim

Kosharskyy

Kaye

Shaparin

Downie

. Is Genicular Nerve Radiofrequency Ablation Safe? A Literature Review and Anatomical Study. Pain Physician. 2016; 19(5): E697-705.

Sarı

Aydın

Turan

Şen

Özlülerden

Ömürlü

İK

, et al. Which imaging method should be used for genicular nerve radio frequency thermocoagulation in chronic knee osteoarthritis?. J Clin Monit Comput. 2017; 31(4): 797-803.

10.

Kim

D-H

Choi

S-S

Yoon

S-H

Lee

S-H

Seo

D-K

Lee

I-G

, et al. Ultrasound-Guided Genicular Nerve Block for Knee Osteoarthritis: A Double-Blind, Randomized Controlled Trial of Local Anesthetic Alone or in Combination with Corticosteroid. Pain Physician. 2018; 21(1): 41-52.

11.

Kim

D-H

Lee

M-S

Lee

Yoon

S-H

Shin

J-W

Choi

S-S

. A Prospective Randomized Comparison of the Efficacy of Ultrasound- vs Fluoroscopy-Guided Genicular Nerve Block for Chronic Knee Osteoarthritis. Pain Physician. 2019; 22(2): 139-46.

12.

Tran

Peng

PWH

Lam

Baig

Agur

AMR

Gofeld

. Anatomical Study of the Innervation of Anterior Knee Joint Capsule: Implication for Image-Guided Intervention. Reg Anesth Pain Med. 2018; 43(4): 407-14.

13.

Fonkoué

Behets

Kouassi

J-ÉK

Coyette

Detrembleur

Thienpont

, et al. Distribution of sensory nerves supplying the knee joint capsule and implications for genicular blockade and radiofrequency ablation: an anatomical study. Surg Radiol Anat. 2019; 41(12): 1461-71.

14.

Roberts

Stout

Dreyfuss

. Review of Knee Joint Innervation: Implications for Diagnostic Blocks and Radiofrequency Ablation. Pain Med. 2020; 21(5): 922-38.

15.

Cosman

Jr. Gonzalez

. Bipolar radiofrequency lesion geometry: Implications for palisade treatment of sacroiliac joint pain. Pain Practice. 2011; 11(1): 3-22.

16.

Santana Pineda

Vanlinthout

Moreno Martín

van Zundert

Rodriguez Huertas

Novalbos Ruiz

. Analgesic Effect and Functional Improvement Caused by Radiofrequency Treatment of Genicular Nerves in Patients With Advanced Osteoarthritis of the Knee Until 1 Year Following Treatment. Reg Anesth Pain Med. 2017; 42(1): 62-8.

17.

McCormick

Korn

Reddy

Marcolina

Dayanim

Mattie

, et al. Cooled Radiofrequency Ablation of the Genicular Nerves for Chronic Pain due to Knee Osteoarthritis: Six-Month Outcomes. Pain Med. 2017; 18(9): 1631-41.

18.

Koshi

Cheney

Sperry

Conger

McCormick

. Genicular Nerve Radiofrequency Ablation for Chronic Knee Pain Using a Three-Tined Electrode: A Technical Description and Case Series. Pain Med. 2020; 21(12): 3344-9.

19.

Cosman

Jr. Dolensky

Hoffman

. Factors That Affect Radiofrequency Heat Lesion Size. Pain Med. 2014; 15(12): 2020-36.

20.

Jadon

. Bipolar Radiofrequency Ablation of Genicular Nerves in Patients with Pacemaker. J Recent Adv Pain. 2015; 1(2): 97-9.

21.