Optimizing the configuration of cement keyholes for acetabular fixation intotal hip replacement using Taguchi experimental design

Cement fixation of the acetabular component is increasingly recognized as a common site of loosening when hip replacements fail. Cement keyholes drill ed into the acetabulum have been recommended to improve this fixation but l ittle is known of the optimum positions or sizes of these holes. This study investigates the diameter, depth and number of keyholes to be drilled to m aximize the failure torque in a model system. A Taguchi experimental design was used to identify the most significant factors and to predict the best configuration of keyholes within the constraints of the experimental test r ig. One hole at each of the pubic, iliac and ischial sites, of 12 mm diamet er and 6 mm depth, was found to be the optimum configuration. The failure t orque was most strongly dependent on the hole diameter in the pubic region, decreased with increasing hole depth and was not sensitive to the number o f holes.