Cobalt chromium molybdenum metal combination for modular hip prostheses

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Medical device engineering

Background:

• Polyethylene wear particles in hip implants cause foreign body reactions and aseptic loosening.
• All-metal hip prostheses demonstrate low wear rates and minimal osteolytic issues.

Purpose of the Study:

• To develop a metal combination for modular hip systems addressing wear and loosening concerns.
• To achieve maximum wear resistance and optimal component clearance.
• To ensure compatibility with existing modular hip system components.

Main Methods:

• Developed a metal combination with a carbide-containing cobalt chromium molybdenum wrought alloy (Protasul-21WF) lining.
• Integrated the metal lining into a polyethylene insert for stable anchoring.
• Implanted approximately 40,000 metal combinations (Metasul) between 1988 and 1995.
• Retrieved and examined 44 explanted components with up to 5.5 years in situ.

Main Results:

• The metal combination demonstrated an average total linear wear rate of 2 to 5 micrometers per year per component after the conditioning phase.
• This low wear rate suggests a significant reduction in particle generation.
• No particle-induced late aseptic loosening was observed under these conditions.

Conclusions:

• The developed metal combination effectively minimizes wear in modular hip systems.
• This technology is expected to prevent particle-induced late aseptic loosening.
• The metal combination offers a durable solution for hip arthroplasty, enhancing implant longevity.