Maximum load to failure of high dose versus low dose gamma irradiation of anterior cruciate ligament allografts: A meta-analysis

Background: The objective of this study was to systematically evaluate the existing literature to compare the biomechanical effects of low dose and high dose gamma irradiation on commonly used ACL allografts.

Methods: A systematic search was performed in PubMed, Cumulative Index for Nursing and Allied Health Literature (CINAHL), Cochrane Reviews, SCOPUS, and SportDiscus. Nine studies were identified that met the following inclusion criteria: 1) controlled laboratory study, 2) investigation of standard allografts for anterior cruciate ligament reconstruction (ACLR), 3) gamma irradiation (dose reported) and a negative control group, and 4) mechanical loading (results reported).

Results: Nine studies met all inclusion and exclusion criteria. There was a dose-dependent relationship between radiation and decreased mechanical tendon integrity. Low dose radiation (<2.5Mrad [Mrad]) showed graft weakening with an average of 4.3% decrease in load to failure (standardized mean difference [SMD], 0.23; 95% CI 0.216, 0.68; p=0.31), whereas high-dose radiation showed a significantly larger (32.4% average) decrease in load to failure (SMD, 1.79; 95% CI 1.194, 2.38; p<0.001).

Conclusions: Gamma irradiation has a negative effect on tendon allograft strength that is dose-dependent, with particularly large effects noted at irradiation doses of ≥2.5Mrad.