March 27, 2018
A minimally invasive, image-guided procedure that blocks small vessels in the knee with the help of biodegradable microspheres relieves symptoms of knee osteoarthritis (OA), a small study found. In the first US clinical trial of geniculate artery embolization (GAE), the procedure provided durable results out to 6 months in 6 of 13 patients tested.
"It's long understood that much of the pain that comes from OA of the knee comes from the synovium, and GAE aims to reduce pain and inflammation in the synovium by blocking some of the small capillaries in the area with microparticles," explained Sandeep Bagla, MD, director of interventional radiology, Vascular Institute of Virginia, Woodbridge.
"Our current hope is that we can prove not only that GAE is safe and feasible but we can actually treat patients for their knee pain who are not yet ready for a knee replacement or patients who are taking chronic pain medication, where we may be able to demonstrate that they can go through a minimally invasive procedure like this to reduce their knee pain and they won't need to be on these medications anymore," he added.
The new study was discussed in a presscast ahead of the Society of Interventional Radiology (SIR) 2018 annual scientific meeting in Los Angeles, California, and presented at the meeting March 19, 2018.
The procedure is performed through a pinhole-sized incision in the skin through which practitioners insert a catheter into the geniculate artery. They then block small capillaries in the synovium with 75- to 100-μm microspheres used in the treatment of multiple conditions, including uterine fibroids. Patients are initially assessed by using two validated clinical scales for knee pain: the visual analogue scale and the Western Ontario and McMaster University Osteoarthritis Index (WOMAC) for pain and disability. They are assessed again after the procedure.
"All patients had moderate to severe OA-related pain," Bagla noted, "and had greater than 50 out of 100 mm on the visual analog pain scale," he added. Investigators plan to enroll 20 patients into the feasibility study, although as of now only 13 patients have actually received GAE treatment for OA of the knee. "The procedure was successfully completed in all 13 patients," Bagla reported, "and all patients received the embolization material to the capillaries in the knee."
Only 8 of the 13 patients treated with GAE had made it out to the 1-month follow-up point at the time of his presentation. However, among these 8 patients, the mean decrease in VAS pain was 58 mm from a score of 72 mm at baseline (P = .016), as Bagla reported. Global WOMAC score was also decreased by a mean of 36.3 points from baseline (P = .0008).
"Overall physical function in the knee also improved after the procedure, and there were no serious adverse events related to the treatment," Bagla observed. He explained that the small capillaries they are blocking with the microspheres are in abnormal tissues lining the knee — "so you don't normally have this degree of increased blood supply to the lining," he explained.
This means that they are not actually blocking normal blood supply to the knee or surrounding structures; as such, "we don't believe that this procedure should have any long-term negative effects," Bagla said. He also noted that the procedure itself takes about an hour — 90 minutes at most — and the amount of radiation required to carry out the procedure is minimal. Researchers expect to present final results in all 20 patients sometime soon.
Meanwhile, interim results clearly suggest that GAE can safely reduce pain and disability in patients with mild to moderate OA of the knee, as Bagla suggested. "Many treatments that are available to treat OA of the knee are either short-term or invasive," he noted. "By short-term, we mean usually joint injections that don't necessarily work for more than a few months or invasive treatments, such as knee replacement, which require hospitalization and a prolonged recovery," he added. "So we are very encouraged by these results and the implications they may have for the millions of people suffering from this common yet debilitating condition."
Commenting on the study, Suresh Vedantham, MD, president of the SIR and professor of radiology and surgery, Washington University School of Medicine in St Louis, Missouri, noted that all would agree more detailed prospective testing of GAE in a broader range of patients is important before the treatment goes "prime time."
Nevertheless, "the biological mechanism behind OA pain is inflammation and proliferation of new blood vessels in the synovium, and this therapy is very well targeted to that particular mechanism so certainly it should be investigated further," Vedantham said.
Some 11 patients have now made it out to the 6-month follow-up point, and they continue to report a similar degree of relief at 6 months.
"This parallels overseas experience with GAE, where they have also found a very durable clinical success rate at 2 and 3 years after the procedure," Bagla noted.
Bagla reports that he is a consultant for Medtronic, Boston Scientific, Teleflex, Terumo, and Merit. He also has received research grants from Medtronic, Boston Scientific, Terumo, BTG, and Renovo. Vedantham reports receiving a research grant from Cook Medical.