MECHANICAL-PROPERTIES OF TENDONS - CHANGES WITH STERILIZATION AND PRESERVATION

Tendon allografts are commonly used to replace damaged anterior crucia te ligaments (ACL). Some of the sterilization and preservation techniq ues used by tissue banks with tendon allografts ai-e thought to impair the mechanical properties of graft tissues. The tensile mechanical pr operties of porcine toe extensor tendons were measured using a dynamic testing machine following either freezing, freeze-drying, freezing th en irradiation at 25 kGy (2.5 MRad), freeze-drying then irradiation, o r freeze-drying then ethylene oxide gas sterilization. There was a sma ll but significant differ ence in Young's modulus between the frozen g roup (0.88 GPa +/- 0.09 SD) and both the fresh group (0.98 GPa +/- 0.1 2 SD) and the frozen irradiated group (0.97 GPa +/- 0.08 SD). No value s of Young's modulus were obtained for the freeze-dr-led irradiated te ndons. The ultimate tensile stress (UTS) of the freeze-dried irradiate d group (4.7 MPa +/- 4.8 SD) was significantly different from both the fresh and the frozen irradiated groups being reduced by approximately 90 percent. There were no significant changes in UTS or Young's modul us between any of the other groups. If irradiation is to be used to st erilize a tendon replacement for an ACL it must take place after freez e-drying to maintain mechanical properties.