Z-τ: Solid Metal Direct Skeletally-Attached Prosthesis

Abstract

A new total hip femoral component has been designed with the intent of producing the following effects: loading the endosteal femoral metaphysis with minimal shear by means of a stepped collar, and creation of the proper stress level proximally through the elimination of stress shielding by means of a polished stem to moment load the femoral diaphysis. Bench testing of axisymmetric pins fixed into polymeric cylinders using acrylic bone cement revealed significant enhancement of resistance to subsidence through a surface structure consisting of steps. Analysis of crazing of brittle stress coats revealed significant reduction of hoop stress for stepped-surface pins relative to that produced by smooth pins. This presents an attractive mechanical environment inductive of supportive functional bony adaptation rather than the usual résorption associated with conventional total joint prostheses.