Mechanical characterization of cranial implant designs using finite element analysis

• Main Author: Ang, Ivy Fang Ling
• Other Authors: School of Chemical and Biomedical Engineering
• Format: Final Year Project
• Language: English
• Published: 2013
• Subjects: DRNTU::Engineering::Bioengineering
• Online Access: http://hdl.handle.net/10356/52101
• Institution: Nanyang Technological University

Globally, rising incidences of traumatic brain injury (TBI) have increased the number of cranioplasty procedures performed to repair cranial defects. Cranial implants have thus experienced a significant evolution in aspects such as structural design and method of fixation. The influence of structural design and fixation on the mechanical response of implants were conducted on custom-designed implants using finite element analysis. Implant materials investigated were polymethylmethacrylate (PMMA) and titanium alloy (Ti6Al4V). The mechanical and structural responses of the implants were compared across varying hole geometry designs (Triangle, Circle and Spiderweb shaped), implant thickness (1.5-2.5mm), and fixture orientaion (Vertical and Horizontal). Results of the FEA show that triangle and circle hole geometries developed lower values of maximum von Mises stress and displacement as compared to spiderweb, suggesting better load bearing capability of regularly-shaped hole geometries. All implant hole geometry designs, with a thickness of 2mm and PMMA material applied, had load bearing capacities above 150N and resultant maximum displacements below 0.5mm, thus validating the use of PMMA as a potential replacement material for Titanium. Regardless of thickness, Spiderweb design indicated the highest values of maximum von Mises stress, suggesting poorer load bearing ability of irregularly-shaped hole geometry. As implant thickness increased, maximum displacement decreased. Vertical fixture legs indicated lower values of maximum von Mises stress than horizontal fixture legs, suggesting that fixation points located further away from the fracture site leads to better load bearing capability. Optimised PMMA implants have weaker mechanical strength as compared to Ti6Al4V implants, but remain a viable material for use in cranial implants. The results highlight the importance of the design aspect in optimising the mechanical properties of cranial implants.