title: The effects of freeze-drying and ethylene oxide sterilization on the mechanical properties of human patellar tendon.
abstract: Human patellar tendon allografts are used to replace injured anterior cruciate ligaments. They are often stored by freeze-drying or freezing before use and have been sterilized by gamma irradiation or ethylene oxide gas. Studies comparing the mechanical properties of tendons preserved by freeze-drying and sterilized by ethylene oxide have yielded conflicting results. This study examined the effects of freeze-drying and ethylene oxide sterilization on the mechanical properties of human patellar tendons obtained from 11 human cadavers; all were free of musculoskeletal disease. The 22 patellar tendons were halved longitudinally; 7 were frozen at -70 degrees C for 8 weeks and served as controls; 8 were freeze-dried; and 7 were freeze-dried and sterilized with ethylene oxide gas. Ultimate tensile stress and longitudinal strain were greater for frozen than for freeze-dried, but not greater than freeze-dried, ethylene oxide-sterilized tendons (P < 0.05). The modulus of elasticity was similar in all tendon groups. The study suggests that some in vitro mechanical properties of frozen tendons may be marginally superior to the properties of freeze-dried tendons, even after correction for size difference. Ethylene oxide gas sterilization had no adverse effect on tendon mechanical properties.
authors.affiliation: Orthopaedic Biomechanics Laboratory, Hennepin County Medical Center, Minneapolis, Minnesota 55415.
authors.forename: J E
authors.initials: JE
authors.lastname: Bechtold
authors.forename: D T
authors.initials: DT
authors.lastname: Eastlund
authors.forename: M K
authors.initials: MK
authors.lastname: Butts
authors.forename: D F
authors.initials: DF
authors.lastname: Lagerborg
authors.forename: R F
authors.initials: RF
authors.lastname: Kyle
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D002102:Cadaver; D015925:Cryopreservation; D004548:Elasticity; D005027:Ethylene Oxide; D005260:Female; D005612:Freeze Drying; D006801:Humans; D008297:Male; D008875:Middle Aged; D010329:Patella; D013242:Sterilization / Q000379:methods; D013710:Tendons / Q000502:physiology* / Q000637:transplantation; D013718:Tensile Strength; D014184:Transplantation, Homologous
chemical_list: D005027:Ethylene Oxide