Orthopedists should never forget the utility of osteotomy as an option for regenerative medicine: the importance of joint preservation surgery and its dissemination

served not only in hip joints but also in the knee and other joints. Although regenerative medicine has recently seen a sudden resurgence of popularity, there seems to be a view that its use is limited to tissue regeneration by transplantation of tissue cultured in vitro using embryonic stem cells or somatic stem cells. However, I believe that regeneration of tissue by stimulating primitive mesenchymal stem cells already present in the living body and by providing an environment suitable for the regeneration of the required cells is a natural form of regenerative medicine. This practice has long been used in the domain of orthopedics. Thus, it is obvious that joint regeneration by osteotomy is one representative type of regenerative medicine. Research on bone fracture healing mechanisms and heterotopic bone formation has been conducted since the eighteenth century, when it was fi rst recognized that bone tissue has particularly strong regenerative potential. The concept of bone induction was formulated more recently. After M.R. Urist, one of the advocates of this concept, fi rst reported the existence of bone morphogenetic protein (BMP), research on BMP advanced rapidly during the second half of the twentieth century. In 1964, Till and McCulloch carried out bone marrow transplants in lethally irradiated mice and observed the formation of many cell colonies in the spleens of these mice. They called them “colony-forming units” (CFU). A CFU is a colony formed by a single hematopoietic stem cell. Their dissertation is thought to have been the fi rst to establish the stem cell concept. Surprisingly, however, in 1962 C.A.L. Bassett (Orthopedic Research Laboratories, Department of Orthopedic Surgery, Colombia University College of Physicians and Surgeons) had already presented an instructional course lecture at the American Academy of Orthopaedic Surgeons (AAOS) in which he stated that induction of cartilage, bone, and tendinous fi ber tissue can be observed during Introduction