**5. Sterilisation, transmission of infectious diseases and biological safety**

The sterilisation is a crucial issue involving grafts and it can change their mechanical properties, as well as may affect transmission of diseases or even tumours [60, 64]. Radiation as Cobalt 60 can significantly reduce bone mechanical properties and even in low doses can destroy morphogenetic properties, in a progressive dose-dependent manner over the bone biomechanics [10]. Several authors studied gamma radiation and other sterilisation methods (ethanol and ethylene oxide at 55°C) and their effect on graft osteoinduction. Gamma radiation with 25 kGy inactivate HIV virus but reduces osteoinduction capacity of grafts in nearly 40%; ethylene oxide at 55°C provides an almost complete loss of this important potential. On the other hand, ethanol has not affected osteoinduction [10, 64]. However, toxic factors should be observed. Ethylene oxide may be maintained in the graft and may interact or be released when in contact with any liquid, including blood. Gamma radiation may be toxic when in direct contact with fat that is present in the grafts [27, 37]. Autoclaving is another way to sterilise grafts. However, xenografts must be sterilised at a temperature of 132°C to inactivate infectious proteins, i.e., prions, though this method reduces the mechanical resistance of xenografts in approximately 70% [62].

risk of transmission of diseases and tumour cells [32, 34, 41, 53]. The vast majority of USA Tissue Banks produce lyophilised human grafts (allogeneic); however, there are few studies on its use or production. Therefore, lyophilised human grafts are still not widespread used among us [8, 56]. The bovine bone has a chemical composition, porosity, size, shape and biological behaviour similar to its human counterpart, although controversial bovine grafts is commonly used in dentistry surgeries and reconstructions [14]. It provides structural support, osteoconduction and a high content of calcium and phosphorus; essential factors for the newly formed bone tissue [40]. For these reasons, its use is growing in orthopaedic surgeries as reported by Prof. Galia [14] and by his co-workers in his research group, Rosito et al. [45, 46], Henning et al. [23] and Diesel et al. [9]. The most important issue is whether the graft has been processed and stored according to the standards of Associations of Tissue Banks and by national and international health authorities.

Biology of Bone Graft and the Use of Bovine Bone for Revision of Total Hip Arthroplasty…

http://dx.doi.org/10.5772/intechopen.79485

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Musculoskeletal tissue banks such as in the USA, there is an institution – the American Association of Tissue Banks (AATB) – to regulate and supervise the functioning of all incountry tissue banks since 1976 [1]. In Brazil, however, is the Ministry of Health, under the regulation order No. 55 (Dec. 2015) [24] that provides the technical regulations for the functioning of musculoskeletal and skin tissue banks of human origin, determining guidance from the facility characteristics, screening of living donors or cadavers up to equipment and human resources [24]. These regulations, though quite strict, have greatly improved the quality of tissue processing and safe use. For accrual, the decision to accept or reject a donor is carried out by the chairman of the Bank of Musculoskeletal Tissues (BMST) after rigorous tests and following an established protocol [38]. As the protocols used by the Tissue Banks, one must consider the history, physical examination and laboratory tests of the donor

**7. Tissue banks**

(**Table 1**).

Frozen grafts from tissue banks undergo several protocols for donor selection before being used for transplantation. Graft rejects are reported to reach 20 to 30% [4, 51]. But even with these severe protocols for selection, transmission of an infectious disease may occur [25, 53, 55, 59. Sugihara et al [53] in 1999 reported the presence of tumour cells in frozen femoral heads and suggested inclusion of histopathological examinations as part of the screening protocol for donor tissues [41, 53].

The lyophilisation process until now has not been linked with infection as confirmed by Shibuya et al. [48], Ledford et al. [29] and Ribeiro et al. [44] who also reported no clinical signs of infections in patients submitted to revision of total hip arthroplasty with acetabular reconstruction, as well as no case of bovine spongiform encephalopathy disease (BSE) and its new variant the Creutzfeldt-Jakob disease (CJD). It is believed that lyophilisation process chemically inactivates most of the bacterial agents, viral and prion agents to a safe and acceptable level to be used in humans as reported by Wenz et al. [63] and among us, by Galia et al. [16] and Rosito et al. [45].
