not be replanted, depending on the individual needs of the patient and the ability of the patient to tolerate a long surgery and a long course of rehabilitation. However, if an amputated specimen is not able to be replanted to its original location entirely, this does not mean that the specimen is unreplantable. In fact, replantation surgeons have learned that only a piece or a portion may be necessary to obtain a functional result, or especially in the case of multiple amputated fingers, a finger or fingers may be transposed to a more useful location to obtain a more functional result. This concept is called "spare parts" surgery. Transplantation Microsurgical techniques have played a crucial role in the development of transplantation immunological research because it allowed the use of rodent models, which are more appropriate for transplantation research (there are more reagents, monoclonal antibodies, knockout animals, and other immunological tools for mice and rats than other species). Before it was introduced, transplant immunology was studied in rodents using the skin transplantation model, which is limited by the fact that it is not vascularized. Thus, microsurgery represents the link between surgery and transplant immunological research. The first microsurgical experiments (porto-caval anastomosis in the rat) were performed by Dr. Sun Lee (pioneer of microsurgery) at the University of Pittsburgh in 1958. After a short time, many models of organ transplants in rat and mice have been established. Today, virtually every rat or mouse organ can be transplanted with relative high success rate. Microsurgery was also important to develop new techniques for transplantation, that would be later performed in humans. In addition, it allows reconstruction of small arteries in clinical organ transplantation (e.g. accessory arteries in cadaver liver transplantation, polar arteries in renal transplantation and in living liver donor transplantation). Treatment of infertility Microsurgery has been used to treat several pathologic conditions leading to infertility such as tubal obstructions, vas deferens obstructions, and varicocele, which is one of the most frequent cause of male infertility. Microsurgical drainages by placing microvascular bypasses between spermatic and inferior epigastric veins as proposed by Flati et al. have been successfully performed in treating male infertility due to varicocele. Microsurgical treatment has been shown to significantly improve fertility rate also in patients with recurrent varicocele who had previously undergone non-microsurgical treatments. References External links E-Medicine Microsurgery Principles Video recorded through Microscope of Ulnar Artery Repaired using Microsurgical Techniques