Optimizing the configuration of cement keyholes for acetabular fixation in total 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 drilled into the acetabulum have been recommended to improve this fixation but little 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 maximize 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 rig. One hole at each of the pubic, iliac and ischial sites, of 12 mm diameter and 6 mm depth, was found to be the optimum configuration. The failure torque was most strongly dependent on the hole diameter in the pubic region, decreased with increasing hole depth and was not sensitive to the number of holes.