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Patients with ankle osteoarthritis got no more relief from platelet-rich plasma (PRP) injections than placebo shots in a randomized, double-blind trial in The Netherlands.

Six months after the participants received two ultrasound-guided intraarticular injections of either PRP or saline, had increased 10 points (reflecting less pain and improved function) on average with the active treatment compared with an 11-point mean increase in the placebo group, according to Liam D.A. Paget, MD, of the University of Amsterdam, and colleagues.

Improvement of 12 points is the threshold for clinically significant relief, the group noted in their . No advantage for PRP was found for any of 14 secondary outcomes, either, which included both physician- and patient-assessed measures of pain and function.

The investigators expressed some surprise at the findings, insofar as a , and some others, had shown a benefit for PRP in knee osteoarthritis. Whether this was because osteoarthritis pathology differs between the joints or because of subtle differences in the treatment is unclear, Paget and colleagues indicated. Both the PRP product and methods of injecting it, as well as patient selection, are not standardized.

But the group did make efforts to adhere to commonly used protocols, including use of the same PRP system employed in the 2016 trial.

PRP is an autologous extract from patients' blood. Platelets release certain growth factors thought to "modulate the intraarticular environment, potentially facilitating an anti-inflammatory, anabolic, and analgesic effect," Paget's group explained. PRP injections have become enormously popular, with suppliers and providers promising osteoarthritis symptom relief to patients who might otherwise have no option other than joint replacement.

Randomized trials have come down on both sides for some forms of the disease. The current study appears to be the first, however, in ankle osteoarthritis: Paget and colleagues could find only "four small case series," all of which reported benefit from the injections.

For the new trial, called , Paget and co-authors randomized 100 patients in blocks of two to six to receive PRP (n=48) or saline (n=52). Participants and those giving the injections and conducting the assessments were blinded to treatment assignments.

Baseline characteristics included the following:

• 55% men

• Mean age: 55

• Mean body mass index: 27

• Median symptom duration: 5 years in PRP group, 8 years in placebo group

• Mean AOFAS score: 63

All patients scored pain at 40 or higher on a 100-point scale. As well, all showed some degree of radiological ankle pathology consistent with osteoarthritis, and severe in roughly 40%. Patients were excluded if they had osteoarthritis in other leg joints that impaired daily activities or if they had undergone ankle surgery in the past year.

Secondary outcomes included five subscales from the Foot and Ankle Outcome score, the AOFAS's pain subscale, Ankle Osteoarthritis Score, the 100-point visual analog pain score, Ankle Activity Score, the mental and physical components of the Short Form-36, the Global Attainment Score, and quality-of-life assessments for health and overall status.

On none of these did PRP show even a hint of benefit.

In sum, wrote Paget and colleagues, the results "do not support the use of PRP injections for ankle osteoarthritis."

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