PRP Injections Show No Significant Improvements in Ankle Osteoarthritis Outcomes

In a recent study, a team of investigators, led by Liam D. A. Paget, MD, Amsterdam UMC, University of Amsterdam, looked to determine the effect of platelet-rich plasma (PRP) injections on symptoms and function in patients with ankle osteoarthritis.

They found that in these patient populations, intra-articular PRP injections, in comparison to placebo injection, had no significant improvement in the primary outcomes that assessed pain, function and alignment over a period of 26 weeks.

Methods

Entitled the “Platelet Rich Plasma Injections for the Management of Ankle Osteoarthritis (PRIMA)”, the study was a randomized clinical trial aimed to assess efficacy of PRP injections in ankle osteoarthritis. It was performed in 6 centers in the Netherlands.

Eligibility for patients included ages ≥18 years, with a score of ≥40 for ankle osteoarthritis pain severity on a visual analog scale (0 - 100, higher score indicating more severe pain) during daily activities, as well as radiographic imaging indicating at least grade 2 tibiotalar osteoarthritis on the van Djk classification.

Then, randomization assigned participants 1:1 to receive 2 ultrasonography-guided intra-articular injections of PRP or a saline placebo. Patients received the injections 6 weeks apart.

Primary outcomes for the study consisted of the American Orthopedic Foot and Ankle Society (AOFAS) score over 26 weeks. The score ranged from 0 - 100, with higher scores indicating less pain and better function. It measured 3 subdomains including pain (40 points), function (50 points), and alignment (10 points).

Findings

Enrollment for the study began in August 2018 and the last 26-week follow-up occurred in December 2020.

A total of 320 patients had been assessed for eligibility, from which 100 were enrolled in the trial and randomized to either PRP (n = 48) or placebo (n = 52). The mean age of participants was 56 years, with 45% women. No patients were lost to follow-up in the primary outcomes.

At baseline, data show the mean AOFAS scores were 63 in the PRP group and 64 in the placebo group. Then, at the 26-week follow-up, mean scores were shown to improve by 10 points in the PRP group (95% CI, 6 - 14, P <.001), in comparison to 11 points in the placebo group (95% CI, 7 - 15, P <.001).

Data show the adjusted between-group differences of PRP versus placebo over 26 weeks was -1 point (95% CI, -6 to 3, P = .56) During the post-hoc sensitivity analysis, no statistically significant between-group differences of PRP versus placebo was observed (-2 points, 95% CI, - 5 to 11, P = .16).

Additionally, the placebo group reported 1 serious adverse event, deemed unrelated to the intervention, with 13 other adverse events in the PRP group and 8 in the placebo.

Takeaways

Investigators noted that ankle symptoms and function did not show significant improvement over 26 weeks with intra-articular injections, compared to placebo, in patients with ankle osteoarthritis.

“The likelihood of clinically relevant benefit is small, because the minimum clinically important difference was outside the 95% CI of the primary outcome,” they wrote.

The study, “Effect of Platelet-Rich Plasma Injections vs Placebo on Ankle Symptoms and Function in Patients With Ankle Osteoarthritis,” was published in JAMA.