The Journal of Bone and Joint Surgery, Vol 76, Issue 1 110-115, Copyright © 1994 by Journal of Bone and Joint Surgery, Inc
Intergranular corrosion-fatigue failure of cobalt-alloy femoral stems. A failure analysis of two implants
JL Gilbert, CA Buckley, JJ Jacobs, KC Bertin and MR Zernich
Division of Biological Materials, Northwestern University, Chicago, Illinois 60611.
Two modular hip implants with a cobalt-alloy head and a cobalt-alloy stem
were retrieved after a fracture had occurred in the neck region of the
femoral component, eighty-five and seventy months after implantation. Both
implants failed less than one millimeter distal to the taper junction
between the head and the stem (outside of the taper). The fracture surfaces
of the implant were investigated with the use of scanning electron
microscopy, to determine the nature of the failure process. The fractures
occurred at the grain boundaries of the microstructure and appeared to be
the result of three factors: porosity at the grain boundaries;
intergranular corrosive attack, initiated both at the head-neck taper and
at the free surface; and cyclic fatigue-loading of the stem. The corrosive
attack of the free surface was initiated, in part, by the egression of
surface grains and by the ingression of fluid into the intergranular
regions. Sectioned surfaces showed extensive intergranular corrosive attack
in the prosthetic neck localized in the region of the head-neck taper
junction and penetrating deeply into the microstructure.
CiteULike 
Connotea 
Del.icio.us 
Technorati What's this?
