Radiofrequency neurotomy for pain relief in knee osteoarthritis
Chronic knee osteoarthritis (OA) is one of the most common diseases of advanced age. OA often results in clinical consequences such as pain, restricted movement, sleep disturbance, and psychosocial disability. Pharmacological therapy in the form of non-steroidal anti-inflammatory drugs is associated with serious side-effects, such as bleeding and gastrointestinal ulcers. Non-surgical interventions, including intraarticular injection with steroids or hyaluronic acids, acupuncture and periosteal stimulation therapy, are often used as complementary therapies, but are not sufficient to control chronic severe knee OA pain. Although surgery is generally effective for patients with advanced disease, older individuals with limiting comorbidities may not be appropriate surgical candidates. In patients who have failed traditional therapies, radiofrequency (RF) neurotomy might be a successful alternative minimally invasive treatment with low risk of complications.
RF Neurotomy is based on the theory that cutting the nerve supply to a painful structure may alleviate pain and restore function. The knee joint is innervated by the articular branches of various nerves, including the femoral, common peroneal, saphenous, tibial and obturator nerves. These articular branches around the knee joint are known as genicular nerves. Three out of six genicular nerves ie suprolateral SL, supromedial SM and inferomedial IM can be easily approached percutaneously under fluoroscopic guidance as they lie near the periosteum at the junction of shaft of femur and epicondyle. Patients can get a diagnostic genicular nerve block to determine if this will provide adequate relief.
Along with this, intraarticular botulinum toxin injection is also given on more painful side which acts by blocking the presynaptic release of acetylcholine from cholinergic terminals of various nerves causing chemical dennervation similar to RF genicular branch. Since it is very difficult for the patient to tolerate the RF neurotomy in both knees in a single sitting because of pain due to multiple injections therefore only botulinum toxin injection 50 units is given in the lesser involved knee.
RF Neurotomy of genicular nerves is a minimally invasive procedure usually done on day care basis. Under sterile conditions, the patient is placed in a supine position on a fluoroscopy table with a pillow under the popliteal fossa to alleviate discomfort. The true AP fluoroscopic view of the tibiofemoral joint is obtained. Skin and soft tissues are anesthetized with 1 mL 1% lidocaine. A 10 cm 22-gauge RF cannula with a 10 mm active tip is employed for the technique. Under fluoroscopic guidance, the cannula is advanced percutaneously towards areas connecting the shaft to the epicondyle, the so-called ‘‘tunnel technique’’, until bone contact is made (Fig.1). Sensory stimulation at 50 Hz is performed to identify the nerve position. The sensory stimulation threshold is required to be less than 0.6 V. In order to avoid inactivating motor nerves, the nerve is tested for the absence of fasciculation in the corresponding area of the lower extremity on stimulation of 2.0 V at 2 Hz. Lidocaine (2 mL of 2%) is injected before activation of the RF generator. The RF electrode is then inserted through the cannula, and the electrode tip temperature is raised to 80 degree C for 90 s. One RF lesion is made for each genicular nerve (Fig.2).
Fig 1: Fluoroscopic view of final needle positions in both AP and lateral views.
Fig 2: Radiofrequency neurotomy of genicular nerves with RF needles in place and RF console.
We learnt from our previous experience that intraarticular botulinum toxin injection provides short term pain relief lasting around three months in cases of pain due to knee osteoarthritis, whereas RF genicular branch provides longer lasting pain relief lasting six months to a year or more.
Since osteoarthritis is a degenerative disease involving both the knee joints, combining RF neurotomy of genicular branches with the intraarticular injection of botulinum toxin does provide long term pain relief lasting more than a year in the more painful knee whereas only botulinum toxin injection suffices for the less painful knee. After the procedure, patient is encouraged to perform quadriceps strengthening exercises and self management of pain. RF neurotomy might be repeated with similar results when the nerve regenerates causing pain similar in intensity to that present before the procedure.
RF Neurotomy is therefore a safe and reliable intervention to reduce the knee pain in advanced cases of osteoarthritis, who are otherwise not candidates for total knee replacement and provides lot of patient satisfaction to the extent of 70-80% in decreasing the pain originating from the knee joint but also to improve the functional activities.
- Radiofrequency treatment relieves chronic knee osteoarthritis pain: A double-blind randomized controlled trial. Woo-Jong Choi, Seung-Jun Hwang, Jun-Gol Song, Jeong-Gil Leem, Yong-Up Kang, Pyong-Hwan Park, Jin-Woo Shin. PAIN 152 (2011) 481–487.