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Efficacy of Platelet-Rich Plasma for the Treatment of Interstitial Supraspinatus Tears: Letter to the Editor

Dear Editor: As clinicians and clinical researchers who have studied the use of platelet-rich plasma (PRP) for more than a decade, we reviewed with great interest the article by Schwitzguebel et al published in the American Journal of Sports Medicine (AJSM). This article appears to provide high-level evidence in the treatment of interstitial supraspinatus tears and tendinopathy with the use of PRP. Although this study is considered level 1 evidence (based on the fact that is a randomized controlled trial), as in other articles with seemingly high evidence, these authors failed to appropriately quantify and document what was actually injected. The outdated terminology of ‘‘PRP’’ was used instead. This concern has been raised in the past, but unfortunately, studies that consider PRP and other biologic treatments continue to be published without the recommended biologic characterization. Until these biologics are properly identified, these publications will fail to advance the science regarding the efficacy of specific PRP treatments. Thirteen years have elapsed since the initial publications on the use of PRP for tendinopathy, and yet it remains unclear whether ‘‘PRP works.’’ A great deal of this controversy remains due to a lack of product standardization. It is evident that not all PRP products are equivalent, and there are multiple processing systems yielding a variety of final PRP products. These final products greatly vary in terms of the actual number of platelets, erythrocytes, and leukocytes. Additionally, some articles refer to ‘‘PRP’’ while the injectate was something else, such as autologous conditioned serum, when the methods are reviewed. The lack of detail and accuracy of the treatment is likely to affect its potential efficacy when provided. The AOSSM Biologics Think Tank in 2015 noted 2 primary challenges regarding the science of PRP: characterizing the active elements in the PRP injectate and finding the appropriate dosing regimen. In 2018, a collaborative symposium was held by thought leaders from the American Academy of Orthopedic Surgeons ‘‘to establish a consensus framework for improving and accelerating the clinical evaluation, use and optimization of biologic therapies for musculoskeletal diseases.’’ This document is published in the Journal of the American Academy of Orthopedic Surgeons with a specific outline of ‘‘minimal reporting standards for clinical studies evaluating PRP.’’ Obviously, this should be the standard for further publications of PRP in the orthopaedic literature. This includes PRP characteristics such as ‘‘platelet concentration, number of platelets delivered, differential leukocyte, and red blood cell analysis of all samples.’’ Schwitzguebel et al described a particular PRP system using a blood sample of 8 mL in a single-spin centrifugation with a final product of ‘‘2 mL of PRP.’’ This is an inadequate description of a PRP injectate based on the recommended standards from these orthopaedic thought leaders. A classification system for future biological research was presented .4 years ago. Mazzucco et al published data on the Regen Kit, which was used in the current study. They noted that the average platelet concentration was only 1.65 times above baseline, the lowest of all the systems tested in that study. Therefore, it is unclear whether the final product actually reached a concentration over baseline and could be properly categorized as ‘‘PRP,’’ as the total number of platelets, erythrocytes, and leukocytes was not characterized. Finally, the authors provide no clear rationale why the intervention was given on 2 separate occasions 1 month apart. This article describes clinical improvement from a treatment that is no better than a normal saline injection for interstitial rotator cuff tears. Yet the treatment may not even constitute PRP or, at best, is poorly defined. Unfortunately, the readers of this article and clinicians considering the use of PRP using a variety of different systems will not be able to reach any definitive conclusion regarding their specific PRP product in the treatment of interstitial rotator cuff tears. It is difficult to understand why this study could be considered level 1 evidence. Publications that meet the scientific rigor of defining the PRP used will remedy this problem. We urge that the editors of AJSM and other journals require strict characterization of the PRP content prior to publication of future articles on this ongoing controversial topic. This will be of great benefit to the AJSM readers, physicians, and their patients.