Temperature-based protection of biochemical and biomechanical characteristics during 25 kGy 60Co irradiation for allograft tendons

While prior studies have investigated cryopreservation, cross-linkers, and radical scavengers for tendon irradiation protection, optimal implementation protocols remain underexplored. We specifically evaluated temperature-dependent efficacy in preserving human tibialis posterior allograft tendons during 25kgy γ-irradiation. Twenty-four human tibialis posterior tendons were irradiated at -70 °C, 0 °C and room temperature. Collagen integrity was assessed through: (1) HE/Masson-stained fiber arrangement, (2) Sirius Red-polarized collagen periodicity, (3) hydroxyproline quantification. Biomechanical properties including elastic modulus and maximum stress were measured via tensile testing. In the - 70 °C group, the structure and morphology of collagen fibers were significantly better than in the 0 °C group. At -70 ºC, collagen damage was 46.27% and 50.03% lower compared to 0ºC (P = 0.016) and RT (P < 0.004). The maximum stress of -70 °C (68.19 ± 30.11 MPa) is superior to that at 0 °C (36.58 ± 12.00 MPa) and RT (41.27 ± 16.34 MPa) (P < 0.01). The histological results based on fiber continuity, crimp integrity, and staining uniformity revealed superior collagen organization at -70 °C (7.2 ± 0.8) versus 0 °C (4.1 ± 1.1, P = 0.016) and RT (3.9 ± 1.3, P < 0.004). Hydroxyproline release was reduced by 46.27% (0 °C) and 50.03% (RT) in the - 70 °C group. Deep cryogenic preservation (-70 °C) demonstrates enhanced protective effects over conventional refrigeration for γ-irradiated tendon allografts, suggesting temperature optimization as critical in clinical processing protocols.