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Gripping is a major challenge faced in the tensile testing of tendons. As soft and aqueous materials, tendons are prone to slip and experience premature failure during mechanical testing. Several gripping methods were attempted and evaluated, including serrated jaw, sandpaper, frozen ends, and air-dried ends. It was found that 1 kN pneumatic grips (Shimadzu Company) lined with cardboard provided an adequate grip without perceptible slip and damage to the tendons. It was found that using the pneumatic grips with cardboard lining the stress concentration at the grip-specimen interface reduced substantially. An analysis of specimens that failed at the grip-specimen interface versus those that failed at mid-substance shows that there was no significant difference in their tensile properties.

The purpose of this study is to evaluate the effect of strain rate on the failure properties of tendons. Seventy-five chicken flexor digitorum profundus (FDP) tendons were tensile tested at 15 strain rates, ranging from 0.05 to 150 per cent/s. Results showed that strain rate had little effect on the shape of the stress-strain curve. No significant change was observed in the toe region, while the slope of the linear region increased with the increase in strain rate. Generally, the ultimate tensile strength (UTS) and elastic modulus increased significantly as strain rate increased (p < 0.01), while no significant change in strain at UTS (p > 0.01) was observed. It was found the change in failure properties of tendons was not significant, with small change in strain rate.

The basic mechanism of reinforcement in tendons addresses the transfer of stress, generated by the deforming proteoglycan (PG)- rich matrix, to the collagen fibrils. Regulating this mechanism involves the interactions of PGs on the fibril with those in the surrounding matrix and between PGs on adjacent fibrils. This understanding is key to establishing new insights on the biomechanics of tendon in various research domains. However, the experimental designs in many studies often involved long sample preparation time. To minimise biological degradation the tendons are usually stored by freezing. Here, we have investigated the effects of commonly used frozen storage temperatures on the mechanical properties of tendons from the tail of a murine model (C57BL6 mouse). Fresh (unfrozen) and thawed samples, frozen at temperatures of -20°C and -80°C, respectively, were stretched to rupture. Freezing at -20°C revealed no effect on the maximum stress (σ), stiffness (E ), the corresponding strain (ε) at σ and strain energy densities up to ε (μ) and from ε until complete rupture (μp). On the other hand, freezing at -80°C led to higher σ,E and μ; ε and μp were unaffected. The results implicate changes in the long-range order of radially packed collagen molecules in fibrils, resulting in fibril rupture at higher stresses, and changes to the composition of extrafibrillar matrix, resulting in an increase in the interaction energy between fibrils via collagen-bound PGs. [ABSTRACT FROM AUTHOR]

Corticosteroid injection using hypodermic needles is one of the commonly accepted treatments for patients with hand conditions. However, in some cases the needle perforations may cause tendon ruptures. This paper aims to investigate the relationships between a tendon's ultimate tensile strength (UTS) and the number of hypodermic needle perforations as well as needle sizes. The UTS was determined for all specimens at the loading rate of 0.4 mm/s. Tendon specimens with perforations punctured by large-sized (19 G) hypodermic needles were found to have significantly lower UTS than those with perforations punctured by medium-sized (23 G) and small-sized (27 G) needles. For specimens punctured by medium- and small-sized needles, no significant difference in UTS was observed between tendons with three perforations and those with one perforation. [ABSTRACT FROM AUTHOR]