GAMMA-IRRADIATION - EFFECTS ON BIOMECHANICAL PROPERTIES OF HUMAN BONE-PATELLAR TENDON-BONE ALLOGRAFTS

Sixty 10-mm bone-patellar tendon-bone allografts from young human dono rs were placed into four test groups, a control fresh-frozen group and three fresh-frozen irradiated groups. The irradiated groups were expo sed to 2.0, 3.0, or 4.0 Mrad of gamma irradiation. The specimens were tested to tensile failure. The initial biomechanical strength of fresh -frozen allografts was reduced up to 15% when compared with fresh-froz en controls after 2.0 Mrad of irradiation. Maximum force, strain energ y, modulus, and maximum stress demonstrated a statistically significan t reduction after 2.0 Mrad of irradiation (P < 0.01). Stiffness, elong ation, and strain were reduced but not with statistical significance. A 10% to 24% and 19% to 46% reduction in all biomechanical properties were found after 3.0 (P < 0.005) and 4.0 (P < 0.0005) Mrad of irradiat ion, respectively. After irradiation with a 4.0 Mrad dose, the ultimat e load was below that of reported values for the human anterior crucia te ligament. It is clinically important to observe and document change s in human ligaments that result from currently used doses of gamma ir radiation. The results from this study provide important information r egarding the initial biomechanical properties of fresh-frozen human bo ne-patellar tendon-bone allografts after bacterial sterilization with gamma irradiation. The current accepted dose for sterilization is betw een 1.5 and 2.5 Mrad. There appeared to be a dose-dependent effect of irradiation on all the biomechanical parameters studied. Four of seven parameters were found to be reduced after 2.0 Mrad of irradiation. Re ductions were found in all parameters after 3.0 and 4.0 Mrad of irradi ation.