During the internal fixation, the type 316LR stainless steel cortical bone screw failed. Extensive spiral deformation was revealed by the fracture surface. Dimple structure characteristic of a ductile failure mode was observed with dimples oriented uniformly in the deformation direction. A zone of heavily deformed grains at the fracture edge was revealed by longitudinal metallographic examination. The shearing fractures of a commercially pure titanium screw and a cast cobalt-chromium-molybdenum alloy were discussed for purpose of comparison.