Localized bone resorption in the femur in mechanical failure of cemented total hip arthroplasties.

In 70 total hip arthroplasties exchanged because of mechanical loosening of the stem prosthesis, localized bone resorption or scalloping was found in 33 cases. In 19 of the 33 cases the process started at the level of the tip of the stem, which in 15 cases was found to be in direct contact with cortical bone as observed in the radiographs obtained immediately after the primary surgery. In 37 failures without scalloping this metal-to-bone contact was less common. It is concluded that localized bone resorption may occur as a result of mechanical stress and in the absence of deep infection. It is also suggested that the phenomenon might be avoided by proper cementing technique and centering of the tip of the stem, perhaps with the help of a centering device.