 The periosteum is a membrane that covers the long bones, jawbone, ribs and the skull.This membrane contains an endogenous population of pluripotent cells called the periosteal cells, which are a type of mesenchymal stem cells (MSC), which reside in the cambium layer, i.e., the side facing the bone.A key step in the procedure is the elevation of the periosteum without damaging the cambium surface and to ensure this a new technique called hydraulic elevation was developed.