Knee embolization: current evidence and ongoing trials

Musculoskeletal embolotherapy continues to move at pace. From the initial potential shown by Dr Yuji Okuno’s pioneering work [1], there is now data from two published randomized sham-controlled trials elucidating the role of genicular artery embolization [GAE] in the treatment of knee OA [2,3].

Research into GAE for knee OA remains the most widely studied MSK embolotherapy. It is becoming clear that complete embolization of a diseased territory is important for clinical success [3]. Research has shown the anatomical complexity encountered during GAE, with frequent anastomoses between vessels posing a risk of non-target embolization [4]. Systematic review and meta-analysis has shown GAE to be safe, with potential mid-term efficacy [5]. Future trials will provide more data on GAE against a sham procedure, further addressing the placebo effect [6]. Data should also concentrate on imaging, biomarkers, and neuropsychological correlates for clinical success. The GENESIS and GENESIS 2 studies both included functional MRI neuroimaging and neuropsychometric testing [6,7]. The GENESIS 1 long term data is now complete showing sustained significant clinical success of GAE in patients with mild to moderate knee OA at 2-years. Furthermore, a correlation between patient catastrophising and clinical outcome was found. The consideration of chronic pain and patient-specific neuropsychological phenotypes will potentially have a significant role in understanding patient selection and clinical outcome for MSK embolotherapy.

Aside from GAE, emerging data has shown potential for embolization as a treatment for patients with plantar fasciitis, adhesive capsulitis, lumbar back pain, as well as osteoarthritis of the fingers, to name but a few [8–11].  The pathophysiology, anatomy and embolization endpoint need careful consideration to perform safe and effective embolotherapy. A significant area of development within MSK embolization is within resorbable embolics. Resorbable embolic technology has several advantages over permanent particles, particularly in end-organ territories such as the hands and feet, where permanent embolics would pose too great a risk of non-target embolization.

As interventional radiology transitions to become a stand-alone clinical specialty, we need to gain a complete understanding of the MSK conditions we treat. Providing patient-centred management that considers other treatment options, limitations of embolization, and patient expectations are important. Understanding the role of biomechanics on pain and clinical outcome is essential. Collaborating with orthopaedic and rheumatology colleagues is needed to gain knowledge and access to physiotherapy and orthotics; both of which can optimize outcome following embolization. Furthermore, some patients will fail to respond to embolization. IRs need a robust mechanism of being able to send patients back to orthopaedics and rheumatology for other options that are in our patients’ best interests.