Do the Properties of the Achilles Tendon's Graft Change Following Excessive Freeze‐Thaw Cycles?
Authors: Zarzecki Michał P. , Pękala Jakub R. , Pękala Przemysław A. , Baginski Adam Piotr , Ekiert Martyna , Walocha Jerzy A. , Tomaszewski Krzysztof A. 
Published: June 2021

IntroductionSurgical reconstruction of damaged tendons and ligaments is a common, but onerous procedure nowadays. An injury to the anterior cruciate ligament of the knee occurs frequently thus many grafting methods have been developed to repair it. One of them involves use of the Achilles tendon (AT). In order to carry out a successful allograft surgery, the material must exhibit equal or greater biomechanical properties than of those tissues it is supposed to replace. The number of freeze‐thaw (F/T) cycles might be a variant that influences the characteristics of the graft, especially worth considering since the extracellular ice crystals forming during freezing might damage the matrix fibers.AimThis study aimed to investigate the influence of the F/T cycles upon tendon graft biomechanical properties, applying a novel methodology involving digital image correlation with ex vivo strain tracking.Materials and methodsThe authors evaluated 12 ATs from healthy patients which were immediately frozen following their collection. The samples were randomly assigned to one of 3 groups subjected to 1, 2 or 3 F/T cycles that included 1 week of deep freezing, followed by 6 hours of thawing at room temperature. Biomechanical tests were performed with a uniaxial tension testing machine (INSTRON®) using a load cell with a maximum capacity of 10 kN in standard atmospheric conditions. The elasticity of the AT samples was evaluated in terms of Young's modulus, derived from the strain curves. The Shapiro‐Wilk test, t‐tests, non‐parametric tests and p of <0.05 applied in the statistical analysis. The research protocol was approved by local Ethics Committee in accordance with the 1964 Declaration of Helsinki and its later amendments.ResultsNo morphological statistically significant differences were found in terms of the samples' widths, lengths or ages of the patients, nor gender. Based on the stress‐strain curves the researchers noted that Group I had the highest mean value of the Young's modulus (279.8±38.6 MPa), hence the highest elasticity. A statistically significant decrease between Group I and Group II (168.4±26.1 MPa, p<0.01) was observed. Group III had the lowest mean value of Young's modulus (119.8±26.6 MPa), which was significantly lower than the values of Group I (p<0.01) and Group II (p<0.05).ConclusionsThe results from this study point out to the fact that repetitive F/T cycles diminish the biomechanical properties of the AT tendon grafts. Due to the tendon grafting being a commonly used orthopaedic procedure, any aspects that can influence outcomes of the treatment should be carefully and meticulously assessed.Support or Funding InformationThis research was supported by National Science Center Poland (OPUS program no. UMO‐2014/13/B/ST7/00690).This study was supported by “The Best of the Best! 3.0 (Najlepszy z Najlepszych! 3.0)” Grant of the Polish Ministry of Science and Higher Education.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.