In vivo degradation performance of micro-arc-oxidized magnesium implants: a micro-CT study in rats

Area of Science:

• Biomaterials Science
• Orthopedic Surgery
• Materials Engineering

Background:

• Biodegradable magnesium (Mg) alloys are promising for osteosynthesis, avoiding secondary removal surgeries.
• Fast-degrading ZX50 Mg alloy implants require surface modification to control degradation rates.
• Micro-arc oxidation (MAO) is a surface treatment technique for metallic implants.

Purpose of the Study:

• To evaluate the effect of MAO surface treatment on the degradation behavior of ZX50 Mg implants.
• To assess the impact of MAO treatment on bone and tissue response in a rat femoral model.
• To determine the suitability of MAO-treated Mg implants for osteosynthetic applications.

Main Methods:

• ZX50 Mg implants were treated with MAO and implanted into rat femurs alongside untreated controls.
• Implant degradation was monitored using microfocus computed tomography (μCT) over 24 weeks.
• Histological analysis was performed at 4, 12, and 24 weeks post-implantation.

Main Results:

• MAO-treated implants exhibited minimal corrosion in the first week, followed by accelerated degradation.
• Degradation rate of MAO-treated implants became faster than untreated controls after three weeks.
• Histology revealed improved bone and tissue response with MAO treatment, including enhanced osteoblast apposition and a stable bone-implant interface.

Conclusions:

• MAO treatment effectively delays initial degradation of Mg implants, promoting early fracture stabilization and better bone integration.
• The surface treatment leads to improved biocompatibility by reducing early hydrogen evolution.
• MAO-treated Mg alloys show significant potential for osteosynthesis due to controlled degradation and enhanced bone healing.