Platelet-rich plasma (PRP) treatments can be used to help managed osteoarthritis pain and tendon injury. To understand if you are a good candidate for PRP it is important to understand the severity of the arthritis and the nature of the tendon injury.
The use of PRP is becoming increasingly common in medical practice, but not all PRP is the same. There can be large discrepancies in PRP composition, and most patients don’t understand these differences.
PRP or platelet-rich plasma is when platelets are concentrated from a sample of a patient’s blood. Platelets have growth factors that act as a beacon attracting other cells to heal damaged tissue, and are used to enhance healing. While PRP has been used since the 1970s for wound and bone healing in oral and maxillofacial surgery (Nikolidakis et al, 2008), there are high-quality systematic reviews, meta-analyses and randomized controlled trials supporting is application in orthopedics and sports medicine.
While there is no single standardized PRP protocol most PRP injections follow a similar process. Whole blood is collected from the patient, centrifuged separating the platelets, red blood cells (RBCs) and white blood cells (WBCs). This process can be performed manually using a laboratory preparation or using a commercially available system.
Commercial kits that are used to concentrate platelets can vary in the type of PRP product that is produced. These kits can vary in platelet recovery rates, hematocrit (red blood cell) levels and growth factor release, but in some cases commercial kits can have a higher platelet counts than manual laboratory preparations (Kevy & Jacobson, 2004).
Not all PRP is the same. The goal of these next few sections is to arm you as the patient with the right questions to ask your physician as you discuss whether or not a PRP injection is the right treatment for your tendon, arthritis or ligament injury.
The optimal platelet concentration for PRP has not been identified yet, but in general the ideal platelet concentration for knee osteoarthritis (Milants et al, 2017) and tendinopathies (Kaux et al, 2015) is between a 3 to 4x increase in baseline platelets. In one study, 33 PRP systems and protocols were tested and only 11 met the definition of PRP as having a minimum platelet concentration of 1,000,000/μL or 5x baseline concentration (Marx et al, 2013). In fact, 3 of the 33 systems and protocols tested had a final PRP product with a platelet count less than that of whole blood (Fadadu et al, 2019).
This variable range highlights the importance of system selection and protocol adherence. In studies of commercial kits Emcyte PurePRP GenesisCS has had the highest platelet concentration tested (Fadadu et al 2019). EmCyte kits have produced PRP with an average platelet concentration of 7x baseline, with some studies showing and increase of greater than 9x baseline concentration (Fadadu et al 2019). Administering an adequate dose of platelets is the cornerstone of PRP therapy, and this is one of the reasons we use the Emcyte system at Boston Sports & Biologics.
Other considerations include the number of white blood (WBCs) and red blood cells (RBCs).
Whether to include WBCs is controversial for tendinopathy, but it is generally accepted that WBCs can be detrimental to articular cartilage healing and should not be included when treating osteoarthritis (Xu et al, 2017; Fitzpatrick et al, 2017). Not all commercial kits will significantly decrease WBC counts.
WBC are characterized into neutrophils, lymphocytes and monocyte cell lines. The deleterious effects of WBCs in PRP are largely attributed to neutrophils. Neutrophils primary function is to engulf and destroy foreign material. Another the reasons we use the Emcyte system at Boston Sports & Biologics is that it allows us to obtain a therapeutic strength PRP with low neutrophils.
Additionally, PRP with high red blood cell (RBC) levels can cause damage and oxidative stress. RBCs deliver oxygen throughout the body, but outside of the blood vessels RBCs can cause oxidative stress. Kits with high RBC concentration produce a red PRP and can increase the pain and counteract the benefit of activated growth factors. Emcyte produces a yellow PRP product with low RBCs of an average 1.1% RBC (Fadadu et al 2019).
Anticoagulants are used in the preparation of PRP to prevent the blood from clotting and platelets from degranulating and releasing growth factors when processed in the centrifuge. The choice of anticoagulant can significantly impact platelet recovery rates. In one study, sodium citrate had twice the platelet recovery rate compared to anticoagulant citrate dextrose solution-A (ACD-A) (do Amaral et al, 2016).
At BSBortho we use EmCyte Pure PRP kits. There are no clear regulations for PRP
injectate composition, and PRP falls into a category of products that does not require that it follow the US Food and Drug Administration (FDA) traditional regulatory pathway. Despite this several PRP systems on the market do have FDA clearance, including Emcyte (Emcyte).
Not all PRP is created equal which is one reason it can fail. There is a lot to know as a patient to make sure that you can make sure your treatment is successful, and the hope is this provides you with the background you need to make an informed decision on your treatment.
Once you decide on what type of PRP you are going to get for your procedure, the next step is making sure that the PRP is precisely placed into the damaged tissue. If the platelets are not injected into the damaged tissue how will they fix that tissue? Precise placement can be challenging and many orthopedic surgeons or PAs do not have the advanced training in ultrasound or fluoroscopy to place the PRP in the right spot.
Dr. Sussman is a senior editor for the foundational textbook on Interventional Orthopedics that teaches how to perform these advanced orthopedic procedures. In addition to teaching these injections, Dr. Sussman has also publishing peer reviewed articles and book chapters on ultrasound guided procedures. Precision matters and ensure that the PRP reaches the right place as how and where the PRP is injected makes a difference (MORE ON PRECISION PRP PLACEMENT HERE).
Berger DR, Centeno CJ, Steinmetz NJ. Platelet lysates from aged donors promote human tenocyte proliferation and migration in a concentration-dependent manner. Bone Joint Res. 2019 Feb 2;8(1):32-40.
do Amaral RJ, da Silva NP, Haddad NF, Lopes LS, Ferreira FD, Filho RB, Cappelletti PA, de Mello W, Cordeiro-Spinetti E, Balduino A. Platelet-Rich Plasma Obtained with Different Anticoagulants and Their Effect on Platelet Numbers and Mesenchymal Stromal Cells Behavior In Vitro. Stem Cells Int. 2016;2016:7414036.
EmCyte Announces FDA 510(k) Clearance for its PurePRP® Supraphysiologic Concentrating System. Accessed April 9, 2021. https://www.prnewswire.com/new...
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Milants C, Bruyère O, Kaux J-F. Responders to platelet-rich plasma in osteoarthritis: a technical analysis. BioMed Res Int 2017;2017:1–11.
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Xu Z, Yin W, Zhang Y, et al. Comparative evaluation of leukocyte- and platelet-rich plasma and pure platelet-rich plasma for cartilage regeneration. Sci Rep 2017;7.
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