The quality of bone tissue used for structural allografts is a key factor in long-term success of revision total joint arthroplasty (TJR). However, terminal sterilisation with gamma irradiation impairs the properties of bone allograft, and subsequently the outcome of revision TJR. This study sought to determine if tocopherol and ascorbic acid was effective as a radioprotection agent to improve the quality of bone allografts.
Ten paired femora were processed according to Queensland Tissue Bank standard protocols. Bones were infused with a mixture of tocopherol and ascorbic acid, and saline (control). Control and vitamin-infused bone samples were equally grouped in five gamma irradiation doses: 0, 10, 15, 25, and 50 kGy, and irradiated frozen. Morselized cancellous bone (MCB) was subjected to both cyclic loading and displacement-controlled compressive tests. Cortical bone specimens were subjected to 3-point bending tests, followed by biochemical analyses of collagen degradation using the alpha chymotrypsin method and analysed for hydroxyproline content. Sterility testing was carried out on cortical bone rings in accordance with ISO standards.
Mechanical responses of bone allograft treated with tocopherol and ascorbic acid were significantly enhanced compared to controls, providing allografts of equal material and structural quality to non-irradiated bone up to 25 kGy in cortical bone specimens (P<0.005). Untreated MCB was significantly stiffer than MCB treated with tocopherol and ascorbic acid (P<0.005). Furthermore, sterility testing confirmed that treatment with tocopherol and ascorbic acid does not reduce sterility assurance levels. A dose-dependent increase of collagen degradation was observed across irradiation groups, however, there was no significant difference in collagen degradation between the control and treated bone specimens.
Our data provides evidence to support the use of the combination of antioxidants, tocopherol and ascorbic acid, as a radioprotectant to improve the mechanical performance of bone allografts whilst maintaining sterility assurance levels.