Decellularisation affects the strain rate dependent and dynamic mechanical properties of a xenogeneic tendon intended for anterior cruciate ligament replacement

Development of new replacement grafts for anterior cruciate ligament (ACL) repair requires mechanical testing to ensure they can provide joint stability following implantation. A decellularised porcine superflexor tendon (pSFT) has been developed previously as an alternative to current reconstruction methods and subjected to biomechanical analysis. The application of varied strain rates to biological tissues is known to alter their biomechanical properties, however the effects of decellularisation on strain rate dependent and dynamic mechanical behaviour of tissues have not been explored. This study utilised tensile testing to investigate the material properties of native and decellularised pSFTs at three different strain rates (1%.s−1, 10%.s−1 and 100%.s−1). In addition, dynamic mechanical analysis (DMA) was used to ascertain the relative contributions of the solid and fluid phase components of the tissues.

Ultimate tensile strength was significantly reduced in decellularised compared with native untreated pSFTs but was unaffected by strain rate. In contrast, toe region moduli increased with increasing strain rate for native tissues, but this effect was not observed in decellularised pSFTs. Linear region moduli were unaffected by strain rate, but were significantly reduced in decellularised pSFT compared with native tissue.

Following DMA, significant reductions in dynamic modulus, storage modulus and loss modulus were seen in decellularised compared with native pSFT. Interestingly, the damping ability of the tendons was unaffected by decellularisation, suggesting that solid and fluid phases of the tissue were affected equally. These results, alongside previous studies, suggest that decellularisation affects collagen crimp, tissue swelling and collagen fibre sliding. However, despite these findings, the biomechanical properties of decellularised pSFT remain sufficient to act as an off-the-shelf solution for ACL reconstruction.