A Randomized Controlled Trial Comparing the Efficacy of a Three-Point Versus a Six-Point Genicular Nerve Radiofrequency Ablation for Chronic Knee Osteoarthritis

Background Knee osteoarthritis (KOA) is a leading cause of chronic knee pain and disability, with a lifetime prevalence of 45%1. While treatment for symptomatic KOA includes physical therapy, oral anti-inflammatory medications and intra-articular steroid injections, the definitive treatment is total knee arthroplasty. However, approximately 600 000 fewer surgeries were performed in the first three months of the COVID pandemic which has created an overwhelming backlog of patients awaiting elective surgical management2. The significant delays caused by the backlog in surgery are leading to worsened pain requiring increased opioid use, functional impairment, and psychological well-being of patients3. Therefore, the use of fluoroscopy-guided genicular nerves radiofrequency ablation (GNRFA) has become a valuable treatment option for patients either awaiting arthroplasty or are ineligible for arthroplasty due to comorbidities or for personal preference3.

GNRFA uses thermal energy to percutaneously create lesions in neural tissues of the genicular nerves that innervate the anterior knee capsule and disrupt the conduction of pain signals. Classically, the three branches of the genicular nerve that are targeted in this procedure include the superolateral genicular nerve (SLGN), superomedial genicular nerve (SMGN) and the inferomedial genicular nerve (IMGN). As these nerves run consistently on their way to the joint between the diaphysis and metaphysis of the femur and tibia, they provide reliable landmarks to targets for an RFA procedure7. Subsequently, the safety of GNRFA in the management of KOA and its greater efficacy compared to other options including intraarticular steroid injections, viscosupplementation and oral analgesics has been replicated in several large clinical studies and systematic reviews, leading to its wide adoption1,4-7. The knee joint innervation is much more extensive, however, as 10 nerves innervate the knee capsule. Unfortunately, not all of them can be targeted percutaneously8. Recent anatomic validation studies, though, have revealed three additional nerves that are suitable targets under fluoroscopy with bony landmarks. These include the two branches from the nerve of vastus intermedius (VIN), which run consistently in the lateral and medial third of the femoral diaphysis 2 cm above the patella, and the recurrent fibular nerve (RFN), which runs consistently on the surface of the fibular head at its widest diameter. Consequently, a six-target technique has been described that includes the recurrent fibular nerve (RFN), and the two branches of the VIN in addition to the conventional three targets9,10.

To date, four-, and six-target knee neurolysis procedures have shown to be effective pain relief in KOA, showing significant improvement in validated pain and functional scores for more than 6 months after the procedure11-14. However, the studies demonstrating these results have primarily consisted of case series with small sample sizes11,13. Thus far, only a four-target technique (adding a single lesion above the patella) has been retrospectively investigated against the original three-target technique, showing improvement in pain in both groups with less opiate medications consumption in the four target group12. Therefore, targeting additional nerves to the three-target technique may improve pain and functional outcomes for this relatively new procedure which has become particularly valuable in the last decade to manage pain due to knee OA and especially during the covid 19 pandemic, where the waiting list of patients for joint replacement has been significantly increasing.

Purpose The overall purpose of this randomized controlled trial is to evaluate the efficacy of a six- target GNRFA technique (T2) in managing the pain and function of KOA patients in comparison to the standard three-target GNRFA technique (T1).

Specific Aims: