One can lower the risk of the injection into vessels by several ways. First, avoiding injecting into deeper planes where these vessels lie is recommended for safety, but may mean less of the fat survives as a graft. Using larger instruments makes it less likely that they can puncture into an vessel. And, constantly moving as one injects makes it less likely that one will inject any significant amount of fat into a vessel. Even still, there always exists a risk. However, I believe that employing the above methods, as well as using vasoconstricting solutions, makes these risks so rare as to be acceptable. The reported cases of deficits with these kind of surgeries do not make any mention of the technique and measures the surgeon used to avoid this complication. So, make sure your surgeon is certified by the American Board of plastic surgery and is performing a safe technique.Best of luck! Dr. SubbioBoard-Certified Plastic Surgeon Newtown Square/Philadelphia, PA