Abstract
Acellular porcine super flexor tendon (pSFT) offers a promising solution to replacement of damaged anterior cruciate ligament [1]. It is desirable to package and terminally sterilise the acellular grafts to eliminate any possible harmful pathogens. However, irradiation techniques can damage the collagen ultra-structure and consequently reduce the mechanical properties [2]. The aims of this study were to investigate the effects of irradiation sterilisation of varying dosages on the biomechanical properties of the acellular pSFT.
Tendons were decellularised using a previously established protocol [1] and subjected to irradiation sterilisation using either 30 kGy gamma, 55 kGy gamma, 34 kGy E-beam, 15 kGy gamma, 15 kGy E-beam and (15+15) kGy E-beam (fractionated dose). Specimens then underwent stress relaxation and strength testing at 0 and 12 months post sterilisation to determine whether any effect on these properties was progressive. For stress relaxation testing, specimens were analysed using a Maxwell-Wiechert model. For strength testing, the ultimate tensile strength, Young's modulus and failure strain were assessed.
Significant differences were found which demonstrated that all irradiation treatments had an effect on the time-independent and time-dependent viscoelastic properties of irradiated tendons compared to per-acetic acid only treated controls. Interestingly, no significant differences were found between the irradiated groups. Similar trends were found for the strength testing properties. No significant differences were found between groups at 0 and 12 months.
Tendons retained sufficient biomechanical properties following sterilisation, however it was notable that there were no significant differences between the irradiated groups, as it was believed higher dosages would lead to a greater reduction in the mechanical properties. The changes observed were not altered further after 12 months storage, indicating the acellular pSFT graft has a stable shelf-life.
