Characterization of Micro-Threaded Stem Taper Surfaces of Cementless Hip Endoprostheses

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Materials Engineering

Background:

• Premature failures in cementless hip endoprostheses are often linked to modular taper corrosion.
• Understanding the micro-threaded stem taper surface is crucial for improving implant longevity.

Purpose of the Study:

• To investigate the impact of micro-threaded stem taper surface properties on premature failures, aseptic loosening, and infection.
• To analyze fretting and crevice corrosion at the head-stem taper interface, specifically with metallic and ceramic components.

Main Methods:

• Characterization of microstructures and surface properties of new and retrieved Zweymüller stem tapers using SEM, EDS, and EBSD.
• Optical profilometry to measure roughness parameters (Ra, Rz) of micro-threaded stem tapers.
• Electrochemical studies, including potentiodynamic measurements in Hank's solution, to assess corrosion rates.

Main Results:

• No fretting corrosion was observed in retrieved stem tapers with ceramic heads.
• Corrosion rates were low for new and aseptically loosened retrieved samples.
• Infected and low-grade infected tapers exhibited higher corrosion rates.

Conclusions:

• Using ceramic heads in hip arthroplasty appears to reduce taper corrosion.
• Reduced taper corrosion may subsequently decrease the incidence of premature failures in total hip arthroplasty.