MS Thesis Defense: Adrianne Gowie

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Meeting ID: 920 9228 0780
Passcode: 193195

"Biodegradable Zinc Alloys for Orthopedic Implants"

Abstract

Orthopedic implants are widely used to restore skeletal function following injury or disease. However, permanent metallic implants, such as those from titanium, cobalt-chromium, or stainless steel, can lead to complications including stress shielding, ion release, and the need for secondary removal surgeries. As a result, there is growing interest in biodegradable metals that safely degrade after fulfilling their mechanical role. Zinc alloys have emerged as promising candidates due to their moderate corrosion rate, essential biological function, reasonable mechanical properties and favorable biocompatible properties.

Zinc-based alloys are particularly suited for temporary orthopedic applications, such as trauma fixation hardware or pediatric implants, in which removal poses additional surgical risks. Unlike permanent implants designed for long-term load-bearing use i.e. the hip or knee, biodegradable systems aim to support healing over a defined period before safely resorbing. Although unalloyed zinc is biocompatible, it lacks the strength and ductility required for clinical use. To overcome this, zinc has been alloyed with trace elements including silver, calcium, iron, magnesium, manganese, titanium, and copper. In this work, several zinc alloys were synthesized using mechanical alloying of powders followed by their compaction using equal channel angular extrusion. They were characterized using X-ray diffraction, scanning electron microscopy, Vickers hardness testing, and density measurements. 

In vivo evaluation of the alloys was undertaken using a subcutaneous implantation of 13.25 mm diameter, 1.00 mm thick disks in BALB/c mice over six time points ranging from 1 day to 12 weeks. Three implants were compared, i.e. mechanically-alloyed zinc (97.5 wt% Zn with Ag, Ca, Fe, Mg, Mn), unalloyed zinc, and stainless steel. In addition, a mock surgery control group was utilized. Mice were monitored for weight change and signs of systemic distress, while local tissue responses were assessed via histological analysis using hematoxylin and eosin (H&E) staining.

Thesis Committee

• Ian Baker (chair)
• Jonathan Elliott
• Katherine Hixon

Contact

For more information, contact Thayer Registrar at thayer.registrar@dartmouth.edu .