Biological Background

Human blood platelet counts are approx imately 200 000/ml. PRP is an autologous concentration of human platelets above this in a small volume of plasma.2 Reports vary regarding the platelet concentration and different growth factors present in the PRP concentrate. Also, there are many preparation protocols, kits, centrifuges and methods to trigger platelet activation before use. The same is true for application methods, including using injectable activated PRP liquid concentrate versus implanting a fibrin scaffold, optimal timing of injection and the specific volume to use. Almost every major manufacturer in the orthopaedic and sports medicine world markets a different commercial kit. Some claim to produce a better quantity and quality of PRP than their competitors from the same amount of blood from the same patient. Costs vary tremendously: a commercial kit yields a PRP concentrate at the cost of several hundred dollars, but inhouse non-automatised techniques produce a PRP concentrate for approximately US$10. Each method to concentrate platelets leads to a different product with different biology and potential uses,3 with a high variation (3 to 27-fold) in growth factor concentration and in the kinetics of release.3,–,5 Most techniques yield a PRP concentrate of approximately 10% of the blood volume taken (eg, 20 ml of whole blood would result in approximately 2 ml of PRP). These differences might be of relevance to clinical management, …