Background and rationale of platelet gel in orthopaedic surgery.

Autologous platelet gel, which is usually prepared by adding thrombin and calcium to a platelet concentrate, is used to accelerate bone repair as a possible alternative to recombinant growth factors (GF), through the osteogenic GF released from alpha-granules. The advantages of platelet gel lie in its mimicking the GF effects of the physiological bone healing and regenerative processes, in addition to a relatively simple and low cost technique. Moreover, if autologous platelet gel is used, immunological reactions are avoided. In in vitro systems, platelet gel stimulated osteogenic differentiation of bone marrow stromal cells, while it inhibited complete osteoclast differentiation and activation. Moreover, platelet gel favoured endothelial cell proliferation and expression of pro-osteogenic functions. In experimental animals and in clinical application, the efficacy of platelet gel was increased by the combination with bone allografts, acting as scaffolds, and with bone marrow stromal cells.