Genicular artery embolization (GAE) is “highly effective and durable” in reducing symptoms due to moderate-to-severe knee osteoarthritis that is refractory to other conservative therapy (such as joint injections and medication), and has an acceptably low toxicity profile. So concludes Siddharth Padia (University of California, Los Angeles, USA), speaking at a press briefing in advance of the Society of Interventional Radiology (SIR) annual meeting (20–26 March, online). He will present these results to attendees of the virtual congress.
Padia cites GAE as a “promising therapy” to treat patients with symptomatic knee osteoarthritis by reducing synovial arterial hypervascularity. “As we all know, having arthritis is a very common problem, resulting in pain and physical dysfunction,” he said. Current treatment options for this disease are to “do nothing” and rest up, to take medications (including nonsteroidal anti-inflammatory drugs; NSAIDs), or, if these have failed, to receive a joint injection: “typically a steroid, such as cortisone, or a gel,” Padia said.
“While those can work,” he continued, “they have relatively short-term results. A typical joint injection lasts for anywhere from one to three months, so it is not really built as a long-term solution. Currently, the only long-term solution is a knee replacement, which does work, and is recommended for people with severe, symptomatic osteoarthritis, but the problem, the challenge with total knee replacement is it involves anaesthesia, it involves a hospital stay, and it has a long recovery and rehabilitation time. Many patients are either not candidates, or want to defer their operation to a later date.”
The investigators therefore conducted a prospective, single-centre, open-label, US Food and Drug Administration (FDA)-approved investigational device exemption (IDE) study that aimed to evaluate the safety and efficacy of the minimally invasive GAE procedure for the treatment of symptomatic knee osteoarthritis, with an eye to looking at potential long-term outcomes.
“In theory, if we can reduce the inflammation, we can make people’s pain go away, and make their overall function improve,” Padia explained, justifying the rationale underpinning GAE. “The goal is to normalise or even decrease the blood flow in the knee joint, because right now, in a patient with arthritis, the blood flow is abnormally increased.”
Knee osteoarthritis is age-related, Padia explained, and as such the study enrolled patients aged 49–80 years (median age of 69). All patients had moderate or severe focal knee pain and osteoarthritis on knee radiograph (Kellgren-Lawrence grades 2–4; 18% were grade 2, 43% were grade 3, and 40% were grade 4), no prior knee surgery, and were not candidates or not willing to undergo total knee replacement surgery. Patients had to have failed conservative therapy, including NSAIDs and/or joint injections. Baseline pain (visual analogue scale) and symptom scores (Western Ontario and McMaster Universities Osteoarthritis Index; WOMAC) were assessed. Median body mass index (BMI) was 28 (range 18–44).
After obtaining femoral arterial access, GAE was performed using 100μm particles (Embozene, Varian) of one to three genicular arteries supplying the location of the patient’s pain, as determined by digital subtraction angiography and cone-beam computed tomography (CT). GAE is performed as an outpatient procedure, and not under general anaesthesia, because “the procedure itself is completely painless”.
Over a nine-month period, 40 patients were treated with GAE. The left knee was treated in 25 of the 40 patients (62%), and the right knee was treated in the remaining 15 (38%). Medial knee pain was treated in 27 of 40 patients (68%), and lateral knee pain was treated in 13 (32%). Technical success was achieved in 100% of patients.
WOMAC and pain scores decreased from a median of 52 (out of 96) and eight out of 10 at baseline to 21 out of 96 (60% decrease) and three out of 10 (63% decrease) at 12 months, respectively. “We saw an immediate drop in WOMAC score, from quite a high score at baseline [52 out of 96] to a median of 22 at one month. It further improved with time: at three months, WOMAC score was 15, and it stayed low for the entire duration of the study.”
Padia and colleagues used a cut-off of 50% to consider their procedure a success. In total, 27 out of the 40 patients (68.5%) had a greater than 50% reduction in WOMAC score, and a further 28 patients from the full cohort (70%) experienced a more than 50% reduction in pain score. “A 50% reduction is quite an aggressive threshold to use,” Padia stated. “The orthopaedic surgery literature uses a much smaller cut-off when they define success. When we use a higher threshold, such as a 75% reduction—a 75% reduction in WOMAC score essentially means you are pain free—that was achieved in 43% [of patients]. There are significant improvements in pain in the majority of patients.”
The investigators also noted any adverse events and symptoms scores, assessing these at one week, one month, three months, six months, and one year after GAE. Transient skin discoloration and transient mild post-procedure knee pain were common and expected. Treatment-related adverse events included: one patient with a groin haematoma requiring overnight observation, seven patients with self-resolving focal skin ulceration, and two patients with asymptomatic small bone infarct on MRI at three months.