Segmental stem fracture of a cemented femoral prosthesis.

We report an unusual case of segmental stem fracture in 4 places of a cemented femoral prosthesis in a 43-year-old man 4 years after total hip arthroplasty. To our knowledge, this is the first reported case of segmental stem fracture. Detailed analysis of the prosthesis was performed at an independent testing laboratory. Initiation of all the cracks occurred on the medial aspect on the stem where the manufacturer's identification lettering was present, and the fractures occurred sequentially along the stem from distal to proximal. Laser etching is likely to have caused the microstructural alterations found on the surface of the stem, which, in turn, predisposed to fatigue cracking. Proximal debonding of the cement-bone interface observed in prefracture radiographs suggests that cantilever-bending stresses represented the initial mode of failure.