A new study has determined genicular artery embolization (GAE) to be a “safe intervention” for mild knee osteoarthritis (OA), showing a sustained benefit at two years. Published in the journal CardioVascular and Interventional Radiology, the authors state that the “learning curve” reflected in their technical success rates uncovers the “complexities” behind the safe and successful performance of GAE.
The study, titled Genicular artery embolization in patients with osteoarthritis of the knee (GENESIS) and led by Mark Little (Royal Berkshire NHS Foundation Trust, Reading, UK) et al, is a National Institute for Health and Care Research (NIRH) portfolio single-centre prospective trial which recruited patients presenting to the orthopaedic department at Royal Berkshire Hospital in Reading. Patients were aged 45 years or older with mild-to-moderate knee OA, defined as Kellegren-Lawrence grade 1–3, who had experienced pain for more than six months despite conservative management.
Little et al enrolled 46 patients with a median age of 60 years, performing GAE using 100–300μm Embosphere (Merit Medical) permanent particles diluted in 20ml (300mg/ml) iodinated contrast (Iomeron). Technical success—defined as embolization of the targeted genicular artery—was achieved in 40 patients (87%) and mean visual analogue scale (VAS) improved from 58.63 (standard deviation [SD] 20.57, 95% confidence interval [CI] 52.7–65.5) at baseline to 37.7 at two years.
The authors also assessed knee injury and osteoarthritis outcome score (KOOS) which they state showed significant improvement at six weeks, three months, one- and two- year timepoints, with associated reductions in analgesia usage. Concerning complications following GAE, Little and colleagues observed a self-limiting groin haematoma and a single case of deep vein thrombosis due to immobilisation, which they say highlights the importance of early mobilisation post GAE.
Further, Little et al detail that nine patients underwent total knee replacement following GAE but when followed up post-surgery, no intraprocedural issues or adverse events were experienced by the operating surgeons or the patient. “This provides further support for the procedure’s utility in those with mild-moderate disease,” the authors state, “as it appears that embolization can be utilised in this cohort without being prohibitive of further surgical intervention in cases of disease progression.”
The authors also carried out functional magnetic resonance imaging (MRI) and psychometric assessments, observing an “unexpected” correlation between baseline catastrophising—maladaptive pain cognitions—and greater reduction in pain post GAE. The authors note that these findings may suggest that patients who catastrophise at baseline experience a bi-fold improvement.
“The neurological data suggest that those who catastrophise at baseline are associated with higher functional connectivity between pain modulatory and processing regions of the brain, perhaps representative of frequent dependency on pain modulation. These patients could be benefitting from a successful reduction in nociceptive signalling via embolization and an overreliance on pain modulatory circuitry.”
Remarking on the operator learning curve visible in their technical success data, the authors identify that a “thorough knowledge” of genicular vascular anatomy, including a “myriad” of anastomoses and non-target tissues supplied by these vessels, is crucial to obtain good technical outcomes. They explain that improved anatomical understanding and the application of intraprocedural cross-sectional imaging has enabled GAE to be undertaken in more complex cases today.
Of their limitations, the authors highlight their small sample size, the lack of an experimental control group and note a placebo effect which “requires consideration” when evaluating modes of treating pain. Going forward, the team detail the GENESIS 2 randomised sham-controlled trial which will consider the placebo effect “inherent with GAE”. Little et al note that they are currently recruiting patients for this study and hope to build on experiences gained from the current work.
