Corrosion of Metal Modular Cup Liners

Area of Science:

• Orthopedic surgery
• Biomaterials science
• Medical device analysis

Background:

• Modular hip implants are common, but corrosion at the shell-liner interface is poorly understood.
• Previous research focused on head taper corrosion, neglecting other modular junctions.

Purpose of the Study:

• To investigate corrosion on the backside of retrieved metal modular hip cup liners.
• To compare corrosion levels between two common modular cup designs: DePuy Pinnacle and Smith & Nephew R3.

Main Methods:

• Visual inspection of 67 retrieved modular cup liners (Pinnacle and R3).
• Energy-dispersive X-ray spectroscopy (EDX) to analyze surface deposits.
• Scanning electron microscopy (SEM) to examine surface morphology and pitting.

Main Results:

• Virtually all liners exhibited corrosion, with the engaging rim significantly more affected than polar regions.
• EDX identified chromium-rich corrosion debris; SEM revealed pitting near these deposits.
• Smith & Nephew R3 liners showed significantly higher corrosion than DePuy Pinnacle liners (P<0.001).

Conclusions:

• The backside of modular hip cup liners is susceptible to significant corrosion.
• Design differences, such as in the R3 and Pinnacle cups, impact corrosion severity.
• Increased corrosion in the R3 design may correlate with its higher revision rates.