The hydrolytic degradation of polydioxanone (PDSII) sutures. Part II: Micromechanisms of deformation

An investigation of morphological changes in hydrolytically degraded polydioxanone sutures (PDSII) during in situ tensile deformation is reported. These changes were followed with the use of real-time small-angle X-ray scattering with simultaneous tensile deformation experiments. The results are correlated with separately performed wide-angle X-ray scattering, and optical microscopy experiments on the effects of tensile strain. Interlamellar and interfibrillar amorphous regions appear to control the microdeformation and the shape of the stress-strain curves of PDSII sutures. The fibers deform initially by interlamellar separation and at larger strains by fibrillar slip. Fractures appear to be caused by the catastrophic growth of cracks. The degradation of interlamellar tie chains in PDSII sutures does not appear to significantly affect the progress of deformation, because deformation through interlamellar separation is largely unchanged by degradation. Conversely, hydration and scission of interfibrillar tie chains lowers the load required to propagate interfibrillar shear. The fibers fail at progressively lower strains as degradation proceeds.