Proof of Concept of a New Revision Procedure for Ceramic Inlays of Acetabular Cups Using a Shape-Memory Alloy Actuator System

Abstract

The revision of ceramic inlays of acetabular cups is a challenging surgical procedure. The mechanical impact during the inlay extraction process can damage the ceramic or metal cup rim. To avoid these risks, a concept for a new revision procedure was developed. It is based on an actuator system, which allows a non-destructive release of the ceramic inlay. To integrate the actuator system, different design concepts of acetabular cup components were investigated, and an actuator based on shape-memory alloy (SMA) wires was developed. The process chain for the actuator, starting from nickel-titanium wires manufactured into the actuator geometry by laser welding and thermo-mechanical treatment for the shape setting process up to the functionality evaluation of the actuator system, was implemented on a laboratory scale. The new revision procedure is based on a phase transformation of the SMA wire actuator, which was obtained through two methods—applying an electrical current by an instrument and rinsing the wire with heated water. The phase transformation of the actuator resulted in a contraction between 3.2% and 4.3% compared to its length after pre-stretching and was able to release the ceramic inlay from the cup. Therefore, the developed actuator design and process chain is a proof of concept towards a new revision procedure for modular acetabular cups.