Gamma irradiation. An effective procedure for bone banks, but does it make sense from an osteobiological perspective?

BACKGROUND Bone grafts promote bone healing by supplying a three-dimensional structure that supports bone ingrowth. Autologous bone therefore still remains the "gold standard" for grafts. Unfortunately, autologous bone grafts are associated with an increased morbidity. In order to avoid such problems, intensive research has been carried out on alternative materials such as allogeneic bone. However, its use is dependent on bone banks and its availability is limited. Gamma irradiation is now becoming established as a procedure for inactivating bacteria, fungal spores and viruses. Its effects on the biomechanical properties of bone have been analyzed in numerous studies. However, the current literature provides little information as to the effects of gamma sterilization on the osteobiology of allogeneic bone grafts. PURPOSE The purpose of this study was to evaluate the effect of gamma-sterilized bone grafts on immunocompetent cells by an in vitro model (a culture of human bone marrow cells). METHODS We decided to use the model of human bone marrow cells in culture for the in vitro analysis because the physiological conditions in the human body can best be simulated in this model and the observed reactions are applicable to humans. RESULTS AND INTERPRETATION In sum, we found a maximum immune response in gamma-irradiated bone grafts, which, interpreted as a sole result, must be seen as a negative biological effect. However, in view of the good clinical results for gamma-sterilized bone grafts other influences would seem to be the determining factors in clinical outcome. Further research is needed to gain a more exact understanding of these factors.