medwireNews: Early trial results suggest that ultrasound-guided genicular nerve block (GNB) may represent a promising short-term treatment option for pain associated with knee osteoarthritis (OA).
Discussing the background to their study, Michael Shanahan (Flinders Medical Centre, Adelaide, South Australia) and colleagues explain that “[s]everal branches of the genicular nerve innervate the knee joint,” and three of these “can be safely accessed with ultrasound.”
They add that application of GNB, using a variety of agents targeting these nerves, “has emerged as a novel alternative treatment, with several case reports or case series demonstrating temporary relief for patients.”
The 12-week phase 1/2 trial, which was presented as a poster at ACR Convergence 2022 in Philadelphia, Pennsylvania, USA, and published simultaneously in Arthritis & Rheumatology, included 59 participants with knee OA and pain intensity of at least 4 on a 10-point VAS.
These people were randomly assigned to receive single-dose injections of celestone chronodose 5.7 mg and bupivacaine 0.5% to the inferomedial, superomedial, and superolateral genicular nerves, or to receive subcutaneous placebo injections at each site.
The investigators report that people treated with GNB experienced improvements in pain, with significantly lower VAS scores in the GNB versus the placebo arm at weeks 2, 4, and 8 after treatment. Specifically, average scores in the two groups were 6.2 versus 5.3 at baseline, 2.7 versus 4.7 at week 2, 3.2 versus 5.1 at week 4, and 3.9 versus 4.9 at week 8.
They note that the between-group difference in average pain VAS was no longer statistically significant at the 12-week follow-up (4.6 vs 5.1), but “the change at week 12 compared with baseline [in the GNB arm] remained greater than the minimum clinically meaningful change” of 1.3 points.
Shanahan et al say that GNB-treated patients also experienced significantly greater improvements in WOMAC total and subscale scores than those given placebo at most timepoints, but with a similar attenuation of the between-group difference to that seen for VAS pain scores over time.
“The degree of improvement in our patients is similar to other studies with active comparator groups, with a similar pattern of diminution of effect at 12 weeks,” write the researchers. They note that “[t]he beneficial effect shown with GNB was similar to the reported effect of radiofrequency ablation, although the duration of the effect of ablation may be longer.”
In his poster presentation at ACR Convergence 2022, Shanahan said that the trial additionally showed “high levels of patient satisfaction in the active group compared with the placebo arm.”
He believes that GNB may be “an efficacious treatment for both pain and function for knee osteoarthritis in adult patients,” particularly those who are unable to undergo total knee replacement or are waiting for the procedure.
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