Summary

This study was designed to determine the effect offlattening the lateral aspect of a commercially availablefemoral prosthesis on its rotational stability inpolymethylmethacrylate cement. Five standard designand five laterally flattened size 7 canine femoral componentswere evaluated. The stems were embeddedin commercially available medical grade polymethyl-methacrylateand rotated 15° while torque and angulardisplacement data were collected. The stiffness,yield and failure variables were compared betweencommercial and flattened stems. None of the mechanicaltesting variables were statistically differentbetween commercial and flattened stems although allof the mean values for flattened stems were higher(1-30%) than mean values for commercial stems.Rotational stability of a canine total hip replacementfemoral component was not significantly enhanced bythe flattened component design modification evaluatedby the testing protocol in this study.