Feasibility of a Shape-Memory-Alloy-Actuator System for Modular Acetabular Cups

Area of Science:

• Biomaterials Engineering
• Orthopedic Surgery
• Mechanical Engineering

Background:

• Modular hip implants offer customization and facilitate revision of worn components.
• Current methods for removing ceramic inlays from acetabular cups risk ceramic chipping and metal cup damage.

Purpose of the Study:

• To present and evaluate a novel shape-memory alloy (SMA) actuator system for minimally invasive ceramic inlay revision in hip implants.
• To assess the feasibility of using thermal activation to generate disassembly forces for ceramic inlays.

Main Methods:

• An in vitro study was conducted using a novel SMA actuator designed to loosen ceramic inlays from acetabular hip cups.
• Two thermal activation methods (heating currents and hot water) were investigated.
• Mechanical testing included push-in/push-out forces, acetabular cup deformation, and actuator-generated forces.

Main Results:

• The SMA actuator generated a significant push-out force, reaching up to 1951 N.
• The required disassembly force for the modular acetabular device averaged 602 N (static) and 713 N (cyclic).
• Implant modifications for the SMA system did not alter the mechanical properties compared to conventional systems.

Conclusions:

• The developed SMA actuator system offers a viable solution for ceramic inlay revision in hip implants, preventing damage to surrounding components.
• The system demonstrates effective loosening of ceramic inlays with substantial force generation.
• This innovation has the potential to improve the safety and efficiency of hip revision surgeries.