The role of blood platelets in the treatment of tendinopathies

Abstract

Tendinopathies are overuse disorders seen in many professional and recreational athletes. It is characterized by a poor healing response with the absence of inflammatory cells. Common tendinopathies are Achilles tendinopathy, jumper’s knee, tennis elbow and rotator cuff tendinopathy. Existing treatment options, like eccentric exercises or shock-wave therapy, are not always satisfactory. Therefore, new possibilities are currently under investigation and the use of autologous blood platelets in sports medicine is rising. Blood platelets are not only of importance during hemostasis, but are also involved in other processes in the human body, like wound healing. Platelets are rich in secretory granules which contain several different growth factors, namely platelet-derived growth factor, vascular endothelial growth factor, transforming growth factor β, epidermal growth factor, insulin-like growth factor, fibroblast growth factor and hepatocyt growth factor. These growth factors are, along with different cytokines and chemokines, involved in general wound healing and platelets are therefore already used in different fields of medicine. Platelets can be administered in the form of platelet-rich plasma (PRP) injections or as a platelet-rich clot releasate (PRCR) during surgery. The effect of PRP or PRCR on in vitro tenocyte proliferation, differentiation and collagen synthesis has already been demonstrated. Studies investigating the in vivo effect of PRP or PRCR on human tendinopathies report contrasting results. Unfortunately, high-quality RCTs are unable to reproduce the promising results seen in case-control or cohort studies. Despite inconclusive results, PRP injections are minimally invasive and side effects are uncommon. On top of that, injections might possibly avoid surgery and PRP treatment deserves therefore further investigation. Still, a lot of questions remain unanswered and further research is required before PRP treatment becomes a well accepted standardized therapy for different tendinopathies.