Two of four adjustable Moore pins, which had been used to stabilize a proximal femur fracture, were found to be broken and deformed at their threads. The pins were made from a cobalt-chromium alloy and were not in the same condition. Brittle precipitates in the grains and grain boundaries were seen in one of the pins and hence the fracture was revealed to have occurred along the grain boundaries. The other pin made from cold-worked cobalt-chromium alloy was observed to have randomly lines of primary inclusions. Intermingled dimples and fatigue striations were exhibited on the fracture surface of this pin. Thus, the effect of different conditions of cobalt-chromium alloys on failure behavior was demonstrated as a result of this study.

The bone cement failed at the distal end of the prosthesis stem of femoral head prosthesis six months after implantation. A small indentation on the lateral contour of the stem was visible where the stem had broken. The degree of loosening (gap between the lateral stem contour and the bone or cement) and implant loading was revealed by the dislocation of fragments of the prosthesis. Secondary cracks that had originated at the lateral aspect of the stem were revealed by metallographic examination of a section parallel to the stem surface and perpendicular to the fracture surface of the distal fragment. Gas pores are apparent in the grain and at the grain boundaries were revealed by a transverse section. Fine parallel line structures that run diagonally through the fractograph may be slip traces were revealed by scanning electron microscopy. One of the cracks was revealed to have propagated through a larger gas pore by a ruptured gas pore. The stresses created through the fatigue process activated glide systems which served the formation of secondary cracks along glide planes.

Threads of a bone screw (Co-Cr-Mo alloy, type ASTM F75) had broken off, and other threads had cracked. 15x sectioning showed porosity, and 155x magnification showed gas holes, segregation, and dissolved oxides. This supports the conclusion that manufacturing defects caused the failure.