To acquire autologous PRP, a technician collects blood from the cubital vein. The amount of blood acquired depends on the clinical application (treatment area) and desired concentration. A centrifuge or filtration then separates the platelets from the plasma. Many different systems are available on the market today to obtain the PRP.
When using a simple centrifugation process, the collected blood spins down between five and 20 minutes. This is determined by the speed of the centrifuge and the concentration desired. A technician then collects the PRP from the tube using a syringe and 18-gauge needle, being careful not to collect any platelet poor or red cells.
A similar method of collection uses an automated centrifugation process that separates the platelets from the whole blood and then automatically sends the product to a separate syringe, using an infrared micro-processing sensor to differentiate between red blood cells and platelet-rich plasma. This type of system seems to lead to more accuracy and allows for more reproducible concentrations.
One such device is the Magellan Autologous Platelet Separator System (Arteriocyte Medical Systems). With either method, the tube that initially collected the blood must have an anticoagulant. The kits that come with the products usually have tubes that already have anticoagulant or come with a separate anticoagulant.
The literature seems to be mixed on the idea of activating the platelets before use. De Vos and colleagues presented a study on the effects of PRP on Achilles tendinopathy without mentioning activation.10 In their review article, Foster and co-workers suggest activation with bovine thrombin.11 Thomas and colleagues mention use of a combination of calcium and thrombin (bovine, human or recombinant).12 Fufa and co-workers used type I collagen to activate PRP and create a collagen-PRP gel.13 The brochure for the Magellan system calls for the activation of PRP by using adenosine diphosphate. The proper way to activate the platelets depends on the intended use of the PRP.
Thrombin and calcium can activate the PRP into a platelet gel. This creates a product that can distribute growth factors to stimulate wound healing while constricting blood vessels to reduce bleeding. In addition, the PRP activation will increase the function of the platelets. The gel can improve tissue adhesion as a scaffold and protect from infection with its concentration of leukocytes. The gel has also reduced pain postoperatively. The platelet gel material is in use mostly for intraoperative situations to promote bone healing as well as being a wound sealant.2,5,6