# Contamination in Bone Substitute Materials: A Systematic Review
The source from which the grafting material originates can be used to distinguish between several grafting materials. (see Figure 1) Autografts (autogenous materials) are derived from the same individual and are transferred from the donor area to the recipient area. Allografts (allogeneic materials) are obtained from another representative of the same species following the appropriate preparation through freezing, freeze-drying, autoclaving, irradiation, or chemical preservation to ensure the absence of an immunological response. Xenogeneic materials (xenografts) are derived from other species [4]. Bone graft materials can be characterized by determining their osteoinductivity, osteoconductivity, and osteogenicity. It can be observed that only autogenous materials possess all three characteristics and are currently the gold standard in surgical procedures. Allogenic materials are the second-best option, offering various forms and large quantities [1]. Xenografts rich in natural hydroksyapatite [5] are also frequently utilized as materials due to their favorable osteoconductivity. However, they are not osteogenic or osteoinductive to the same extent as the aforementioned materials. Despite the implementation of aseptic techniques during the harvesting and transplantation of bone grafts, the possibility of contamination remains. It is possible for microbiostas to form on the material during the interval between harvesting and transplantation [6]. Furthermore, environmental exposure of the donors to osteoporoxic substances, such as lead, plays a significant role in graft purity. While the data in question are not routinely available, it is nevertheless the case that exemplary levels of accumulated lead in animal bone tissue have been demonstrated to impair the healing of fractures and bone metabolism [7]. Nevertheless, the incorporation of selected ions like strontium, iron, magnesium, zinc, or lanthanide substituted or co-substituted in hydroxyapatite has the potential to enhance the properties of the bone graft such as better biocompatibility, improved angiogenesis capability, or enhanced osteoconductivity [8; 9; 10; 11]. It is of the utmost importance that grafting materials undergo appropriate processing, as this can significantly reduce the risk of unwanted contamination. Firstly, a comprehensive donor screening process is conducted, which includes an examination of the donor's medical and social histories, as well as microbial and viral testing. Moreover, aseptic recovery, appropriate processing techniques, and a range of disinfection methods, including antibiotics, detergents, mechanical processes, chemical solutions, and terminal sterilization, are employed [12]. The demineralization of the tissue sample increases the fusion potential of the graft. A decellularization process was employed to minimize the risk of immunological response and graft rejection. However, in the case of bone grafts, the retention of some living cellular elements may be beneficial. This can be achieved through many techniques, including refrigeration in media, freeze-drying, cryopreservation, freezing, and media storage at room temperature [12]. The objective of this study was to conduct a comprehensive review and synthesis of existing data in the scientific literature regarding contamination associated with the preparation and processing of bone graft materials. A systematic review of this topic is necessary as no studies addressing a similar question were identified in the databases searched. The authors, therefore, deemed it essential to address this gap systematically.