title: The effect of gamma irradiation on anterior cruciate ligament allograft biomechanical and biochemical properties in the caprine model at time zero and at 6 months after surgery.
abstract: BACKGROUND
  High levels of gamma irradiation are required to eliminate the risk of bacterial and viral transmission during implantation of musculoskeletal allografts. The effects of high levels of gamma irradiation on anterior cruciate ligament allograft biomechanics are still not known.
  
  
  OBJECTIVE
  High-dose gamma irradiation (4 Mrad) adversely affects anterior cruciate ligament allograft biomechanics at surgery and at 6 months after surgery and affects biochemistry at 6 months.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  Bilateral anterior cruciate ligament reconstructions were performed in 18 adult goats, with one knee receiving an irradiated patellar tendon allograft (4 Mrad) and the other receiving a frozen control allograft (0 Mrad). In 6 recipients (time zero group), graft pairs were tested immediately after sacrifice, and load relaxation of the femur-allograft-tibia preparation was measured during cyclic anterior displacement. Twelve recipients received bilateral anterior cruciate ligament reconstructions, staged 2 months apart, and were sacrificed a mean of 6 months postoperatively. Load relaxation and tensile failure testing were performed, followed by allograft biochemistry assessment.
  
  
  RESULTS
  At time zero, irradiated grafts showed less load relaxation than did contralateral controls, but by 6 months, the trend had reversed because of decreases in control graft relaxation, with no changes in irradiated graft relaxation. By 6 months, irradiated grafts showed lower stiffness and maximum force compared to controls but no differences in modulus, maximum stress, or biochemistry.
  
  
  CONCLUSIONS
  High levels of gamma irradiation affect anterior cruciate ligament allograft subfailure viscoelastic and structural properties but not material or biochemical properties over time.
  
  
  CONCLUSIONS
  Although high levels of gamma irradiation may inactivate infectious agents, this treatment is not a feasible clinical option because of altered allograft biomechanics.
authors.affiliation: Noyes Tissue Engineering and Biomechanics Laboratories, Department of Biomedical Engineering, University of Cincinnati, Ohio, USA.
authors.forename: Herbert E
authors.initials: HE
authors.lastname: Schwartz
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Matava
authors.forename: Frank S
authors.initials: FS
authors.lastname: Proch
authors.forename: Charles A
authors.initials: CA
authors.lastname: Butler
authors.forename: Anthony
authors.initials: A
authors.lastname: Ratcliffe
authors.forename: Martin
authors.initials: M
authors.lastname: Levy
authors.forename: David L
authors.initials: DL
authors.lastname: Butler
mesh_terms: D000818:Animals; D016118:Anterior Cruciate Ligament / Q000601:surgery*; D050376:Bone-Patellar Tendon-Bone Grafting; D005260:Female; D005720:Gamma Rays; D006025:Glycosaminoglycans / Q000032:analysis; D006041:Goats; D006909:Hydroxyproline / Q000032:analysis; D023421:Models, Animal; D017847:Patellar Ligament / Q000737:chemistry / Q000502:physiology / Q000528:radiation effects*; D011509:Proteoglycans / Q000032:analysis; D011897:Random Allocation; D013242:Sterilization / Q000379:methods; D013718:Tensile Strength; D013997:Time Factors; D014184:Transplantation, Homologous; D016474:Weight-Bearing
chemical_list: D006025:Glycosaminoglycans; D011509:Proteoglycans; C013786:A73025; D006909:Hydroxyproline