Effect of accelerated electron beam on mechanical properties of human cortical bone: influence of different processing methods

Abstract

Accelerated electron beam (EB) irradiation has been a sufficient method used for sterilisation of human tissue grafts for many years in a number of tissue banks. Accelerated EB, in contrast to more often used gamma photons, is a form of ionizing radiation that is characterized by lower penetration, however it is more effective in producing ionisation and to reach the same level of sterility, the exposition time of irradiated product is shorter. There are several factors, including dose and temperature of irradiation, processing conditions, as well as source of irradiation that may influence mechanical properties of a bone graft. The purpose of this study was to evaluate the effect e-beam irradiation with doses of 25 or 35 kGy, performed on dry ice or at ambient temperature, on mechanical properties of non-defatted or defatted compact bone grafts. Left and right femurs from six male cadaveric donors, aged from 46 to 54 years, were transversely cut into slices of 10 mm height, parallel to the longitudinal axis of the bone. Compact bone rings were assigned to the eight experimental groups according to the different processing method (defatted or non-defatted), as well as e-beam irradiation dose (25 or 35 kGy) and temperature conditions of irradiation (ambient temperature or dry ice). Axial compression testing was performed with a material testing machine. Results obtained for elastic and plastic regions of stress–strain curves examined by univariate analysis are described. Based on multivariate analysis, including all groups, it was found that temperature of e-beam irradiation and defatting had no consistent significant effect on evaluated mechanical parameters of compact bone rings. In contrast, irradiation with both doses significantly decreased the ultimate strain and its derivative toughness, while not affecting the ultimate stress (bone strength). As no deterioration of mechanical properties was observed in the elastic region, the reduction of the energy absorption capacity of irradiated bone rings apparently resulted from changes generated by irradiation within the plastic strain region.

Global maxillary ridge augmentation with frozen radiation-sterilised bone blocks followed by implant placement: a case report

“…Other studies (Dziedzic-Goclawska et al 2005 ; Kaminski et al 2012a , b ), as well as the presented case report, proved that the concerns are groundless. Frozen bone grafts radiation-sterilised even with as high dose as 35 kGy were entirely safe for the recipient’s health and its structure provided excellent scaffold for the new bone formed in the process of osteoinduction.…”

Disinfection of human musculoskeletal allografts in tissue banking: a systematic review

“…Two studies indicated recovery of cadaveric tissues in processing labs (Guo et al 2012; Kaminski et al 2012). Twelve studies indicated that during recovery, allografts were recovered under aseptic conditions, but did not address specific methods to reduce the bioburden.…”

“…Twelve studies indicated that during recovery, allografts were recovered under aseptic conditions, but did not address specific methods to reduce the bioburden. Only one study reported the use of class C and D air filters to reduce potential contamination of tissues by airborne contaminant (Kaminski et al 2012). …”

“…Seven studies showed that there was a reduction in tensile strength (acoustic emission), maximum force, and deformation energy with exposure to large doses of irradiation (>35 kGy). Interestingly, two studies showed an increase in ultimate strain, Young’s modulus, and strain energy density or the resilience and elastic limit of bones, following irradiation at 18–50 kGy, and 35 kGy, respectively (Grieb et al 2005; Kaminski et al 2012). …”

Soft-Tissue Allografts Terminally Sterilized with an Electron Beam Are Biomechanically Equivalent to Aseptic, Nonsterilized Tendons

“…Early concerns regarding the limited penetrability of dense materials by electrons have been addressed through process improvements, including increasing the power of the electron beam to 10 MeV and incorporating two-sided dose delivery 27 . Several medical device companies have successfully adopted e-beam technology to terminally sterilize their tissuebased products because of the benefits of reduced tissue degradation, well-controlled dose ranges, and rapid turnaround 25,28 . Encouraged by this progress, our organization has validated that e-beam sterilization of soft-tissue allografts at delivered doses between 9.2 and 21.0 kGy achieves a sterility assurance level (SAL) of 10 26 , as measured in accordance with the ANSI/AAMI/ISO (American National Standards Institute/Association for the Advancement of Medical Instrumentation/International Organization for Standardization) 11137 standards.…”