Sterilization effects on the mechanical properties of human bone-patellar tendon-bone allografts

Novel allograft processing methods are available from tissue banks to decrease disease transmission. This study evaluated the effects of 3 of these techniques on the initial mechanical properties of bone-patellar tendon-bone (BPTB) allografts: (1) aseptic harvest with low-dose radiation processing, (2) BioCleanse Tissue Processing System, and (3) Clearant Process. Ten-mm BPTB allografts were potted in an MTS 858 machine (MTS Systems Corp, Eden Prairie, Minnesota), cycled, and loaded to failure at a strain rate of 100%/s. Data were critically analyzed for graft dimensions and age and sex of donor. The 10th cycle and last cycle stiffness after 1000 cycles were measured at the toe region and at all points. The 2% yield stress (MPa), Young's modulus (MPa), elongation failure (mm), strain fracture (%), ultimate stress (MPa), and toughness (kJ) were measured. Forty-two tendons were tested (15 control, 11 BioCleanse, and 16 Clearant). No statistically significant differences were detected between the groups at their 10th cycle and last cycle stiffness (P>.05). Yield stress ranged from 19 to 28.8 MPa without a statistically significant difference (P>.05). Young's modulus ranged from 178.3 to 213.8 MPa without a statistically significant difference (P>.05). Similarly, elongation to failure, strain to failure, ultimate stress, and toughness showed no statistically significant differences among the 3 groups (P>.05). These processing techniques did not affect the time zero mechanical properties of the BPTB allograft tendons under these testing conditions. Clinical use of allografts should proceed with caution for selected patients.