A morphology based failure criterion for implanted bone screws
- Project Number: LSC17_004
- Project Lead: Andreas Reisinger, Karl Landsteiner University of Health Sciences / Division Biomechanics
- Project Partner: AIT Austrian Institute of Technology / Center for Health & Bioresources
- Duration: 48 months starting from 01.06.2019
In modern orthopedic surgery, the complication rate due to bone screw breakout and loosening during the convalescence period is still substantial. The surgeon's decision, whether an implanted screw will bear the occurring loads or not, is mainly based on the personal- or clinical experiences. This research project aims to improve the current situation by developing a computer based method which is able to estimate the failure risk of a bone screw prior its implantation. In particular it is hypothesized that the (multi-axial) failure load of an individual bone screw can be predicted by local morphological parameters at its implantation position. This morphological information is based on computer tomography (CT) scans of the fractured bone. In a mid-term perspective, this morphologically-based screw failure criterion could find its way into pre-operative computer planning tools to be used by surgeons for determining the optimal implant position and screw number in advance. Such a clinical tool could lead to more successful surgeries, less costly complications, and higher quality of life for the patient. For developing this screw failure criterion, the idea of bone biopsies studies is followed. A high number of bone samples with screws will be prepared in the laboratory and scanned with a micro-CT system in order measure the local bone morphology. Biomechanical testing in multiple directions will provide data about the mechanical competence of the bone screws including the relevant failure mechanisms. The obtained screws’ failure loads will be related to the samples’ histomorphometric parameters and expressed in a failure surface. With that failure surface, the failure risk of a bone screw can be predicted based on local bone morphology and a loading state prior implantation. In this study standard titanium screws as well as screws made from biodegradable magnesium will be evaluated. This magnesium alloy degrades naturally in the environment of a living body and could make the extraction of implants obsolete. To gain deeper knowledge about that promising material, the failure loads of magnesium screws at multiple degradation states will be compared with standard titanium screws.