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Interv Pain Med
Interv Pain Med
Interventional Pain Medicine
2772-5944
Elsevier

S2772-5944(23)00008-0
10.1016/j.inpm.2023.100182
100182
Case Report
Genicular nerve neurolysis with phenol for chronic knee pain: A case series
Wilkinson Alex J. Alexwilk25@gmail.com
a∗
Chai Thomas b
Roldan Carlos J. b
Huh Billy K. b
a -McGovern Medical School at UTHealth Houston, Houston, Texas, Harris County, USA
b -Department of Pain Medicine, Division of Anesthesiology, Critical Care Medicine, and Pain Medicine, M.D. Anderson Cancer Center, USA
∗ Corresponding author. 6431 Fannin St, Houston, TX 77030, USA. Alexwilk25@gmail.com
24 2 2023
3 2023
24 2 2023
2 1 1001826 1 2023
28 1 2023
1 2 2023
© 2023 The Author(s)
2023
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Chronic knee pain continues to be a common complaint amongst patients and continues to grow as the elderly population lives longer. New ways to treat chronic pain conditions, including chronic knee pain, are necessary as increased co-morbidities prevent patients from being surgical candidates. Recently, the genicular nerves have received more attention due to their role in innervating the anterior knee joint capsule as well as the intraarticular and extraarticular knee ligaments. Initial interest in the genicular nerve included radiofrequency ablation. RFA while effective, also brings with it increased procedure and equipment costs with a non-response rate of around 25%. Alcohol neurolysis of the genicular nerve is being seen as a potential alternative, low-cost, effective option for relieving chronic knee pain in patients. Previous case reports have focused on the use of alcohol, we report the use of phenol for genicular neurolysis. Of the four genicular nerve branches, only three are targeted due to the proximity of the inferolateral genicular nerve to the common peroneal nerve. The purpose of this case report is to show the effectiveness of phenol for neurolysis of the genicular nerves in relieving chronic knee pain in patients in which surgery is not an option.
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pmc1 Introduction

As the population continues to age and advancements are made in prolonging life in patients it is paramount to find ways to treat chronic knee pain non-operatively as co-morbidities (ie. obesity, infection, tobacco use, metastatic cancer, compromised cardiopulmonary state) may exclude them from being surgical candidates. While intraarticular injections, physical therapy, and operations have been traditionally seen as methods to treat knee pain, all of which are limited in conditions that can be effectively treated, long-term effectiveness, and safety of carrying out the procedure. Recently, the genicular nerves have received more attention to treat knee pain [1] due to their role in innervating the anterior knee joint capsule as well as the intraarticular and extraarticular knee ligaments [1,2,[4], [5]]. (Fig. 1).Fig. 1 Genicular Nerve anatomical position with demonstration of three areas of interest for genicular nerve neurolysis.

Fig. 1

Initial interest in the genicular nerve included treatment with radiofrequency ablation (RFA) [2]. RFA while effective, also brings with it increased procedure and equipment costs, yet still reports a non-response rate of around 25% [[1], [2], [3]]. Alcohol neurolysis of the genicular nerve is being seen as a potential alternative, low-cost, effective option for relieving chronic knee pain in patients [[1], [2], [3]]. Previous case reports have focused on the use of alcohol, we report the use of phenol for neurolysis of the genicular nerves in the treatment of chronic knee pain in patients that have failed multiple therapies including surgery or that surgery is no longer an option.

2 Cases

Case #1: In the first case, a 79-year-old female with metastatic breast cancer presented to the clinic due to chronic pain in her neck, low back, shoulders, hips, and knees. She reported operations previously at most of these areas for her pain, will little long-term pain relief. Due to her chronic co-morbidities, including her metastatic breast cancer, any further operations were not a viable option. More specifically, she complained of continued right knee pain, even after her right total knee arthroplasty. She rated her right knee pain at an 8/10 initially. She had failed multimodal therapy including diclofenac gel, duloxetine, gabapentin, and opioid therapy (hydrocodone). She underwent a right genicular nerve block for diagnostic purposes under ultrasound guidance and reported pain relief from a 9/10 to a 4/10. She later underwent the right knee genicular nerve neurolysis procedure using 3 mL of phenol 6% in sterile water at each of the three areas of interest. Afterward, at two weeks post-procedure, she reported pain relief from a 7/10 to 0/10 (Fig. 2).Fig. 2 Fluoroscopic images taken during the genicular neurolysis procedure with phenol on a patient with previous right TKA. Three areas of neurolysis can be seen due to needle placement.

Fig. 2

Case #2: In the second case, a 48-year-old male with a history of germ cell tumors, and ALL presented due to chronic low back and left knee pain. He complained of repeated left knee effusions with no abnormal findings on MRI or x-ray to indicate the utility of operative treatment. His pain was previously treated with repeated knee aspirations and steroid injections by both the orthopedics and pain medicine teams. He rated his pain at 9/10 initially. He was on multi-modal pain therapy including methadone, hydromorphone, gabapentin, baclofen, and topical compound cream. He underwent a right knee arthrocentesis and a right genicular nerve neurolysis procedure with 3 mL of 6% phenol in sterile water. He reported a 75–100% improvement in his pain and reported being “very satisfied” ten days after the procedure (Fig. 3).Fig. 3 Fluoroscopic images taken during the genicular nerve block neurolysis procedure with phenol indicating appropriate placement of needles for neurolysis.

Fig. 3

Case #3: In the third case, an 81-year-old female with a history of lung cancer presented to the pain clinic due to chronic pain in her left knee and back. She was previously evaluated by the orthopedics team and determined to have osteonecrosis of the left medial femoral condyle. After consulting with the patient, she preferred to undergo non-operative treatment instead of left total knee arthroplasty. Her pain was refractory to multiple founds of arthrocentesis and intraarticular steroid injections. She rated her pain at a 9/10 in the clinic pre-procedure. She underwent a left knee arthrocentesis and left genicular nerve neurolysis procedure with 3 mL of 6% phenol in sterile water at each nerve. Post-procedure, she rated her pain at a 0/10 with continued pain relief at follow-up one week later (Fig. 4).Fig. 4 Fluoroscopic images taken during the genicular neurolysis procedure with phenol on a patient with left knee osteonecrosis that prefers non-operative management of her knee pain.

Fig. 4

3 Discussion

Chronic knee pain due to osteoarthritis affects up to 20 million adults in the United States, with a growing number of people not candidates for invasive procedures due to BMI, age, or other comorbidities. The Genicular Nerve branches, excluding the inferolateral genicular nerve due to concerns over common peroneal nerve damage, have shown promise in treating chronic knee pain in this population. Radiofrequency ablation was the first modality used for the treatment of chronic knee pain with ablation of the genicular nerves. RFA successfully provided patients with significant, lasting relief from chronic knee pain. Notwithstanding, RFA also comes with high equipment costs and a longer duration of the procedure [1,2,4].

Chemical neurolysis of the GN has the potential to add increased benefits of low cost, ease of the procedure, less logistical support, and potential for more widespread neurolysis (depending on volume of injectate) compared to RFA [1,2,4]. The technique used to perform the procedure varies between ultrasound or fluoroscopic guidance per physician preference. [1] The authors primarily utilize fluoroscopic guidance to place 22-gauge 3.5 inch Quinke needles at the junction of the femoral metaphysis and epiphysis to target the superomedial and superolateral genicular nerves, and at the junction of the medial tibial metaphysis and epiphysis to target the inferomedial genicular nerve.

There are still potential risks to the procedure, including pain at the injection site, infections, increased pain afterward, bleeding, dizziness, nausea, allergic reactions to the anesthetics, or failure of the procedure due to anatomic difficulties or ill-identification of the nerve location [[6], [7], [8]]. The ideal volume and selection of neurolytic is the subject of debate. In previous case reports using 50–100% alcohol, we utilized 3 mL of 6% phenol in sterile water at each target nerve for each patient [[1], [2], [3], [4]].

While previous case reports have used alcohol for neurolysis, this report highlights the alternative of phenol for neurolysis. Some potential advantages to phenol include more localization given higher viscosity, local anesthetic properties to reduce procedural discomfort, and lower rate of neuritis compared to absolute alcohol [[9], [10], [11], [12]]. A potential disadvantage of phenol is that it must be constituted and stored, whereas absolute alcohol is readily available in vials.

4 Conclusion

In this case series, we demonstrate the successful use of chemical neurolysis of the genicular nerves for the treatment of chronic knee pain in patients that are not surgical candidates, using phenol as the neurolytic agent of choice. Immediate pain relief ranging from 75 to 100% overall pain relief was obtained immediately post-procedure and sustained at follow-up greater than one week later. Genicular nerve neurolysis with phenol is a low-cost and effective treatment option for chronic knee pain in comparison to other treatment modalities, including RFA. More research is needed to quantitatively analyze the long-term outcomes, cost savings, and side effects of this procedure. In addition, comparative studies against absolute alcohol for genicular neurolysis are needed.

Declaration of competing interest

Alex Wilkinson: None.

Thomas Chai: None.

Carlos J. Roldan: None.

Billy K. Huh: None.

Acknowledgements

None.
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References

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