Non-invasive Degradation Tracking of Mg Implants in Humans: A Measurement Approach

Abstract

Measurement of degradation progression of biodegradable metals such as magnesium in vivo is of great importance for customer satisfaction and regulatory purposes. Current methods are based on x-ray/CT (computed tomography) or MRI (magnetic resonance imaging) and have only limited validity. MRI results are heavily impacted by the implant’s position and orientation in the magnetic field. CT scans expose patients to radiation and, due to similar attenuation, precisely distinguishing between bone, magnesium degradation products or metal, makes proper degradation tracking impossible. Both methods rely on subjective assessments of the results. In this work, we describe two non-invasive methods to prospectively overcome these adverse and often inaccurate methods: hydrogen measurement and metal detection. We validated both methods and assessed their feasibility for a clinical application. Both methods are suitable to detect the state of degradation of magnesium implants in vivo directly or indirectly by means of periodically recurring standardized measurements in future studies.