PRP consists of the fractionated liquid component of autologous whole blood, which contains increased concentrations of platelets and cytokines. Different methods and commercial preparations are available for collecting and preparing PRP. Variations in the amount of blood drawn, use of anticoagulants, presence or absence of an activating agent, number of centrifuge spins, and overall platelet and white blood cell concentrations lead to difficulty in evaluating and interpreting the available evidence regarding PRP therapy.
In vitro and animal studies demonstrated promising and safe results regarding the healing effect of PRP on injured soft tissues, such as tendons, ligaments, and muscles. In this regard, a number of studies have evaluated the effect of PRP on human MSK injuries. However, in addition to the above-mentioned variabilities in PRP, many of such studies lack standardization and randomization techniques and include a small number of patients only, thereby limiting the overall comparison and clinical application.
A landmark study conducted by Mishra and Pavelko19 concluded that PRP significantly reduced pain in patients with chronic elbow tendinosis. Similar findings were reported in high-level overhead athletes with ulnar collateral ligament insufficiency, which did not improve with conservative management.20 Fitzpatrick and colleagues21 found improvements in pain with the use of single PRP injection as treatment for chronic gluteal tendinopathy. PRP can effectively improve pain and recovery in chronic ligament and tendon injuries, such as lateral epicondylitis, patellar tendinopathy, and plantar fasciitis, when patients are unresponsive to traditional conservative management. The application of PRP to treat acute MSK injuries has produced mixed results. Hamid and colleagues22 conducted a level II randomized controlled trial to evaluate the effect of PRP combined with a rehabilitation program for treatment of grade 2 hamstring injuries on return-to-play compared with rehabilitation alone. Fourteen athletes were randomized into the study and control groups. Hamid and colleagues22 reported improved return-to-play in the study group compared with that in the control (26.7 and 42.5 days, respectively). This study also reported lower pain scores in the PRP group over time, but the difference was not statistically significant. Zanon and colleagues23 conducted a prospective study to evaluate return-to-play in professional soccer players with acute hamstring strains treated with PRP and a rehabilitation program. This study determined that athletes treated with PRP were “match fit,” meaning they would be available for match selection in an average of 36.8 days. However, Zanon and colleagues23 did not include a control group for comparison. Other studies reported that PRP treatment of acutely injured muscles and medial collateral ligaments of soccer and basketball players decreased their return-to-play interval.18 Reviews by Hamilton and colleagues24 and Pas and colleagues25 concluded that PRP treatment of acutely injured tissues with good blood supply (eg, hamstring muscles) did not improve pain or return-to-play compared with standardized rehabilitation protocols. Similarly, in a double-blinded placebo controlled trial, Reurink and colleagues26 evaluated return-to-play in 80 athletes with acute hamstring injuries treated with a rehabilitation program and either PRP or placebo. Reurink and colleagues26 found no difference in return-to-play (42 days for both groups), but the difference was not statistically significant. PRP has also been used intraoperatively and shows promising results in total knee arthroplasty, anterior cruciate ligament reconstruction, acute Achilles tendon repair, rotator cuff repair, and cartilage repair. However, many of these intraoperative studies are limited to animal models.
In 2009, the World Anti-Doping Agency (WADA) prohibited the use of PRP because it contains autologous growth factors and IGF-1, which could produce an anabolic effect. Recent studies have failed to demonstrate any athletic advantages of using PRP. WADA has since removed PRP from its prohibited list. PRP is also not prohibited by the US Anti-Doping Agency (USADA) and many major professional sporting leagues in the United States. However, care must be taken in reviewing the components of PRP because many commercially available products differ in PRP formulation. Since 2010, many team physicians have increasingly used PRP to treat a wide range of athletic injuries. A recent anonymous survey conducted by a team of physicians on PRP use in elite athletes revealed minimal complications but significant variability among physicians with regard to timing, belief in evidence, and formulation and dosing of PRP treatments. Many physicians did implicate athlete desire as the main indication for treatment.27
As an autologous treatment, PRP injection has no serious adverse effects beyond mild discomfort as a result of the procedure and pro-inflammatory state in the days following injection. Recent concerns regarding the potential of PRP treatment for heterotopic ossification have been reported, but published information is limited to case reports. PRP can improve pain and function in patients with chronic MSK injury. PRP appears to be a safe and effective alternative to surgery for patients with injury to poorly perfused tissue, which has not improved with conservative measures, such as rest, physical therapy, and anti-inflammatory medications. Care should be taken when treating athletes with PRP to establish regulations on doping by individual governing bodies.
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