| Abstract | | Purpose: To evaluate the in vitro biomechanical characteristics of patellar tendon ligaments (BTB) when stored as fresh frozen or as glycerol cryopreserved allografts. Methods: Seventy patellar tendons were harvested from 35 cadaveric human donors and randomly assigned into seven groups. Grafts in group FRESH were mechanically tested within 2 h of harvesting. FROZ-3, FROZ-6, and FROZ-9 were deep-frozen to -80 degrees C for 3, 6, and 9 months, respectively. Grafts in groups CRYO-3, CRYO-6, and CRYO-9 were initially incubated with 10 % glycerol in a phosphate-buffered saline for 1 h and then stored in glycerol solution (10 % glycerol in PBS) at -80 degrees C for 3, 6, and 9 months, respectively. Grafts were mechanically tested with two cycling modes (50-250 degrees N and 150-500 degrees N) and then loaded to failure. Results: Cryopreserved grafts demonstrated more consistent results and expressed lower elongation rates after both cycling loading protocols compared to their frozen counterparts at all storage times. During load-to-failure analysis, ultimate stiffness levels were predominantly higher (23.9-61.5 %) in cryopreserved grafts compared with frozen grafts, and ultimate stress levels were 26 % (13.3-47.7 %) higher, regardless of the storage time. Moreover, cryopreserved grafts revealed similar ultimate elongation and uniformly higher ultimate stiffness and ultimate stress levels compared to fresh grafts. Conclusion: The results of this in vitro study demonstrated superior mechanical properties of cryopreserved grafts compared to frozen grafts within a preservation period of 9 months. Cryopreservation with glycerol solution might be used to further improve the quality of preserved soft-tissue allografts.
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