title: Fractionation of high-dose electron beam irradiation of BPTB grafts provides significantly improved viscoelastic and structural properties compared to standard gamma irradiation.
abstract: OBJECTIVE
  Irradiation >30 kGy is required to achieve sterility against bacterial and viral pathogens in ACL allograft sterilization. However, doses >20 kGy substantially reduce the structural properties of soft-tissue grafts. Fractionation of irradiation doses is a standard procedure in oncology to reduce tissue damage but has not been applied in tissue graft sterilization.
  
  
  METHODS
  Forty-four human 10-mm wide bone-patellar-tendon-bone grafts were randomized into four groups of sterilization with (1) 34 kGy of ebeam (2) 34 kGy gamma (3) 34 kGy fractionated ebeam, and (4) non sterilized controls. Graft´s biomechanical properties were evaluated at time zero. Biomechanical properties were analyzed during cyclic and load-to-failure testing.
  
  
  RESULTS
  Fractionation of ebeam irradiation resulted in significantly higher failure loads (1,327 ± 305) than with one-time ebeam irradiation (1,024 ± 204; P = 0.008). Compared to gamma irradiation, significantly lower strain (2.9 ± 1.5 vs. 4.6 ± 2.0; P = 0.008) and smaller cyclic elongation response (0.3 ± 0.2 vs. 0.6 ± 0.4; P = 0.05), as well as higher failure loads (1,327 ± 305 vs. 827 ± 209; P = 0.001), were found. Compared to non-irradiated BPTB grafts, no significant differences were found for any of the biomechanical parameters. Non-irradiated controls had significantly lower cyclic elongation response and higher failure loads than ebeam and gamma irradiation.
  
  
  CONCLUSIONS
  In this study, it was found that fractionation of high-dose electron beam irradiation facilitated a significant improvement of viscoelastic and structural properties of BPTB grafts compared to ebeam and gamma irradiation alone, while maintaining levels of non-irradiated controls. Therefore, this technique might pose an important alternative to common methods for sterilization of soft-tissue allografts.
authors.affiliation: Sports Medicine and Arthroscopy Service, Hospital for Orthopaedic Surgery and Traumatology, Campus Mitte, Charité, University Medicine Berlin, Charité Platz 1, 10117 Berlin, Germany. arnd.hoburg@charite.de
authors.forename: A
authors.initials: A
authors.lastname: Hoburg
authors.forename: S
authors.initials: S
authors.lastname: Keshlaf
authors.forename: T
authors.initials: T
authors.lastname: Schmidt
authors.forename: M
authors.initials: M
authors.lastname: Smith
authors.forename: U
authors.initials: U
authors.lastname: Gohs
authors.forename: C
authors.initials: C
authors.lastname: Perka
authors.forename: A
authors.initials: A
authors.lastname: Pruss
authors.forename: S
authors.initials: S
authors.lastname: Scheffler
mesh_terms: D000328:Adult; D000368:Aged; D016118:Anterior Cruciate Ligament / Q000382:microbiology* / Q000528:radiation effects*; D001696:Biomechanical Phenomena; D050376:Bone-Patellar Tendon-Bone Grafting; D018562:Disease Transmission, Infectious / Q000517:prevention & control; D019583:Dose Fractionation, Radiation; D004548:Elasticity; D005720:Gamma Rays; D006801:Humans; D008875:Middle Aged; D011829:Radiation Dosage; D011897:Random Allocation; D013242:Sterilization / Q000379:methods; D014184:Transplantation, Homologous; D014783:Viscosity