Corrosion of surgical implants

Area of Science:

• Biomaterials Science
• Orthopaedic Surgery
• Materials Science

Background:

• Orthopaedic implants are susceptible to corrosion in the physiological environment.
• Understanding implant corrosion is crucial for patient safety and long-term device performance.

Purpose of the Study:

• To investigate the corrosion mechanisms and metal ion release from intramedullary nails and osteosynthesis plates.
• To correlate corrosion products with implantation time and biological factors.

Main Methods:

• Analysis of explanted intramedullary nails (n=12) and osteosynthesis plates (n=12) after 8 and 13 years of implantation, respectively.
• Quantification of nickel and chromium in patient biological fluids.
• Electronic probe analysis to study metal-sulfur reactions.
• Comparison with metal ion release from Ni-Fe-Cr dental alloys in cell culture.

Main Results:

• High concentrations of nickel and chromium were detected in biological fluids, correlating with implantation time.
• All implants exhibited both crevice and intergranular corrosion.
• Intergranular corrosion was linked to mechanical and heating treatments.
• Crevice-like corrosion was potentially exacerbated by sulfur from amino acids.
• Metal-ion release increased with exposure time, consistent with crevice corrosion acceleration.

Conclusions:

• Implantation time significantly influences corrosion and metal ion release from orthopaedic implants.
• Both mechanical/thermal treatments and biological factors like sulfur contribute to implant corrosion.
• The findings highlight the importance of material selection and surface properties in preventing long-term implant degradation.