# A Structural Optimization Framework for Biodegradable Magnesium Interference Screws

## TL;DR

This paper presents a new structural optimization framework for biodegradable magnesium interference screws that accounts for material degradation during use.

## Contribution

The novel contribution is a structural optimization framework for magnesium interference screws using a continuum damage model and surrogate modeling techniques.

## Key findings

- The Kriging model's optimization results were validated through finite element analysis and found to be acceptable.
- The framework explores the relationships between design parameters and optimization outcomes.
- A final design proposal and design recommendations for interference screws are provided.

## Abstract

Biodegradable magnesium alloys have garnered increasing attention in recent years, with magnesium alloy–based biomedical devices being clinically used. Unlike biologically inert metallic materials, magnesium-based medical devices degrade during service, resulting in a mechanical structure that evolves over time. However, there are currently few computer-aided engineering methods specifically tailored for magnesium-based medical devices. This paper introduces a structural optimization framework for Mg-1Ca interference screws, accounting for degradation using a continuum damage model (CDM). The Optimal Latin Hypercube Sampling (OLHS) technique was employed to sample within the design space. Pull-out strengths were used as the optimization objective, which were calculated through finite element analysis (FEA). Both Response Surface Methodology (RSM) and Kriging models were employed as surrogate models and optimized using the Sequential Quadratic Programming (SQP) algorithm. The results from the Kriging model were validated through FEA, and were found to be acceptable. The relationships between the design parameters, the rationale behind the methodology, and its limitations are discussed. Finally, a final design is proposed along with recommendations for interference screw design.