The Influence of In Vitro Test Conditions on the Biomechanical Properties of Degenerated Lateral Menisci - A Ring Study

The biomechanical properties of degenerated meniscal tissue are increasingly being studied in the context of osteoarthritis research. Spatial indentation testing using a multiaxial testing machine allows non-destructive characterization of viscoelastic properties. However, in vitro testing conditions can significantly influence the results. The purpose of this round robin study was to evaluate the effects of different fixation methods and laboratory environments on the viscoelastic properties of degenerated lateral menisci. Spatial normal indentation tests were performed on nine degenerated human lateral menisci in two laboratories using a multiaxial testing machine. Key parameters, including the maximum applied force (P _max ), instantaneous modulus (IM), and elastic modulus (E _t10 ), were analyzed across different meniscus regions. Significant differences in the IM, E _t10 , and P _max were observed between the laboratories, highlighting the influence of testing conditions on biomechanical results. The results indicated that variations in fixation methods, environmental conditions, and freeze-thaw cycles significantly affect the elastic and viscoelastic properties of meniscal tissue. Unphysiological strains in the inner region of the menisci suggested that strain-controlled indentation may be preferable to distance-controlled testing. These results underscore the importance of standardizing in vitro conditions for meaningful comparisons with the existing literature.