Genicular Artery Embolization for the Treatment of Knee Pain Secondary to Osteoarthritis

Clinical question

Is hyperemic synovial tissue embolization for knee pain secondary to osteoarthritis a safe procedure? Does the embolization of at least 1 genicular artery provide symptom relief?

Take-away point
Yes, genicular artery embolization for moderate-to-severe pain secondary to osteoarthritis refractory to conservative therapy is safe and efficacious in this 20 patient pilot study.

Reference
Genicular Artery Embolization for the Treatment of Knee Pain Secondary to Osteoarthritis. Bagla, S, Piechowiak, R, Hartman, T, Orlando, J, Gaizo DD, Isaacson, A. Journal of Journal of Vascular and Interventional Radiology (JVIR), Volume 31, Issue 7, 1096-1102.

Click for abstract

Study design
Single arm, prospective, two-center study of 20 patients with radiographic evidence of knee OA and moderate-to-severe pain refractory to conservative therapy who underwent embolization of at least 1 genicular artery with a follow-up of 6 months.

Funding Source
No funding source was disclosed.

Setting
Academic hospitals. Vascular Institute of Virginia, Woodbridge, Virginia and University of North Carolina Hospital, Chapel Hill, North Carolina.





Figure 3 and 4. Superior medial genicular artery angiography showing hypervascular “blush” (black arrows, left) over the medial inferior aspect of the knee which was “pruned” after embolization (right). The parent superior medial genicular artery remained patent.

Summary

Conventional and conservative treatments for knee osteoarthritis (OA) in patients not yet appropriate for total knee arthroplasty (TKA) have potential complications and demonstrate inconsistent efficacy. Recent research has shown that OA is associated with chronic inflammation, which drives the releases cytokines such as vascular endothelial growth factor (VEGF) and the resultant osteophyte formation, cartilage breakdown, and progressive knee pain.

Genicular artery embolization (GAE) has been described as safe and effective in post-TKA hemarthrosis. Similar techniques were also reported for OA-related pain palliation, including one large study using rapidly absorbable embolic antibiotics mixture with 72 patients and 95 knees, a clinical follow up of 36 months, and 80% clinical success rate. Safety and clinical efficacy using permanent embolic agent in GAE for knee pain secondary to OA remain scarce in the literature.

The authors performed a single-arm, prospective, two-center study of 20 patients with osteoarthritic knee pain who underwent GAE. Inclusion criteria included age 40+, mild-to-moderate knee OA by radiograph, pain 5+/10, and failure of conservative treatments for 3+ months. Exclusion criteria included rheumatoid arthritis, renal insufficiency, irreversible coagulopathy, previous arthroplasty, joint infection, Kellgren–Lawrence grade 4 radiographic findings, or MRI incompatibility. All 20 patients underwent further MRI delineation of the affected knee. The WOMAC questionnaire and VAS were used for clinical assessment at 1, 3, and 6 months after GAE. Technical success defined as embolization of 1+ genicular artery. Clinical success defined as 20% change in VAS or 16% change in WOMAC at 6-month follow-up without increase in pain medication use of intra-articular injection.

Procedural pearls included 1) digital subtraction angiography (DSA) at the distal superficial femoral artery to identify the target genicular arteries in the region of the maximal pain; 2) identify a hypervascular “blush”; 3) embolization with (9 mL contrast and 6 mL particle mixture) using either 75- or 100 µm spherical particles (Embozene); 4) 0.2 mL aliquots embolization with intermittent DSA after each injection until hypervascular “blush” is no longer evident. Patients were discharged on the same day.

20 embolization procedures were performed with 2.5 genicular arteries embolized on average. At 6-month follow-up, significant mean decreases from 76 to 31 for VAS and 61 to 31 for WOMAC were observed. 65% of patients reported decrease in daily analgesic use. Adverse events included 65% reporting skin discoloration without ulcer which resolved by the 3-month follow-up (class A), 1 small access site hematoma (class A), and 10% reporting great toe plantar numbness which resolved within 2 weeks (class B; which prompted the change from 75- to 100- µm particles from the 10th patient on with no further neurologic events reported).

Commentary

The authors in this paper have demonstrated that GAE using permanent embolic particles for osteoarthritic knee pain refractory to conservative management, especially with 100-µm sized particles, is safe and effective. It is important to remain cautious as this study has a relatively short follow-up period of 6 months, relatively small patient sample size of 20, and a pilot single-armed prospective design. As the authors have described, a control arm, preferentially double-blinded, may be necessary to determine the therapeutic effect masked by the placebo effect. A larger sample size may enable detailed analysis beneficial for optimal patient selection. In addition, long term adverse outcomes, such as accelerated progression of OA or potential issues with eventual TKA, could not be assessed. Nonetheless, GAE is a promising minimally-invasive alternative method of pain palliation in patients with moderate-to-severe osteoarthritic knee pain. Future larger, long-term, and placebo-controlled clinical trial designed in a scientifically rigorous manner similar to this presented work, is needed for full evaluation.

Post Author
Ningcheng (Peter) Li, MD, MS
Integrated Interventional Radiology Resident, PGY-4
Department of Interventional Radiology
Oregon Health and Science University, Dotter Interventional Institute
@NingchengLi