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Platelet-Rich Plasma Injections vs Placebo for Patients With Ankle Osteoarthritis—Reply
In Reply We appreciate the opportunity to respond to the Letters to the Editor about the PRIMA study. Dr Barber and colleagues express concerns regarding the lack of detail describing PRP preparation and characterization, the exclusion of patients with polyarticular osteoarthritis and cointerventions, and recommendations made close to the intervention. As described in our protocol, analysis of PRP was not performed because the PRP content of the standardized Arthrex ACP system and protocol has been frequently analyzed. This system produces a leukocyte-poor PRP with approximately 2 to 3 times higher platelet concentration compared with whole blood. An “optimal” PRP preparation protocol has not yet been established. Analyzing the PRP content would not alter the outcome or conclusion of our trial. The generalizability of our findings to other PRP systems remains a limitation that was described in our study. Including patients with polyarticular osteoarthritis might mask a possible intervention effect on the outcome measures. For instance, a potential benefit of PRP on ankle function may be masked by limitations that knee osteoarthritis poses on a patient’s function in daily activities and walking distance. During design of the study, we used the best available evidence from knee osteoarthritis PRP studies for recommendations on activity and NSAID use. Knee osteoarthritis studies that reported a positive effect for PRP generally recommended reduced weight loading for 24 hours to 48 hours and no NSAID use. We recommended no NSAID use 24 hours before the injection and during the follow-up and avoidance of heavy or repetitive stress to the ankle joint for 48 hours after the intervention. We are not aware of any evidence supporting the belief of Barber and colleagues that patients need to abstain from activity for longer than 48 hours after PRP injection.
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