Biomechanical properties and dry weight content of the developing superficial digital flexor tendon in rabbit

Composition and structural organization of tendon changes during aging and these alterations affect the mechanical behaviors of this structure. Therefore, this experiment was designed to study the biomechanical properties together with changes in dry weight content of normal superficial digital flexor tendon of rabbits from pre-natal stage to 112 days post-natally. Forty-two White New Zealand rabbits were assigned to seven different age groups (from 5-7 days before birth to 112 days after birth), each consisting of six animals. The right superficial digital flexor tendons were used for biomechanical studies and the left ones for percentage dry weight investigation. Ultimate tensile strength, stiffness, maximum energy, and percentage dry weight values significantly increased in each higher age group compared to those of the younger group and the yield strain and maximum strain decreased comparatively as a function of age. This improvement in the mechanical behavior of tendons during aging could be correlated with increase in collagen content, alteration in the collagen fibril differentiation and distribution from small-sized unimodal fibrils to trimodally distributed collagen fibrils, improvement in quantity and quality of the cross-linking, fibril continuity, type of collagen, development and maturation of crimp pattern, tissue alignment and organization. Therefore, characterization of mechanical behavior and tissue dry weight, as an index of collagen content, from fetal stage to skeletally mature animals is essential in better understanding the tissue structural development and hierarchical organization coincidental with the material properties of this organ. © Springer-Verlag London Limited 2008.