PARAMETRIC FINITE ELEMENT ANALYSIS OF MAGNESIUM-BASED ANTERIOR CRUCIATE LIGAMENT INTERFERENCE SCREWS FOR THE PURPOSE OF OPTIMIZING SCREW PURCHASE

Abstract

Purpose: Most interference screws (IFS) for anterior cruciate ligament (ACL) reconstruction are manufactured from traditional materials like titanium. The advent of degradable metals (i.e. magnesium (Mg) alloys) has shown great promise for numerous orthopedic applications, including IFS for ACL replacement. Questions surrounding the mechanical integrity of degradable Mg alloys, as well as the impact of design changes on behavior, are still unanswered. The purpose of this research was to determine the impact of thread shape, diameter and screw taper on pullout strength of Mg-based IFS. Methods: Four different thread shapes were modeled, and analyzed, using finite element analysis. It was hypothesized that the thread shape, diameter and taper of the screw would significantly impact the pullout performance of the screw. Results: A buttress design resulted in the highest reaction (pullout) force (1247N) providing the greatest hold. Conclusion: Results of this study indicate that design factors impact pullout force and suggest thread shape, taper, and major diameter having the greatest impact.