Mechanical Strength Study of a Cranial Implant Using Computational Tools

Pedro O Santos,Ricardo J Alves De Sousa,Gustavo P Carmo,Mariusz Ptak,Fábio A O Fernandes

doi:10.3390/app12020878

Abstract

The human head is sometimes subjected to impact loads that lead to skull fracture or other injuries that require the removal of part of the skull, which is called craniectomy. Consequently, the removed portion is replaced using autologous bone or alloplastic material. The aim of this work is to develop a cranial implant to fulfil a defect created on the skull and then study its mechanical performance by integrating it on a human head finite element model. The material chosen for the implant was PEEK, a thermoplastic polymer that has been recently used in cranioplasty. A6 numerical model head coupled with an implant was subjected to analysis to evaluate two parameters: the number of fixation screws that enhance the performance and ensure the structural integrity of the implant, and the implant’s capacity to protect the brain compared to the integral skull. The main findings point to the fact that, among all tested configurations of screws, the model with eight screws presents better performance when considering the von Mises stress field and the displacement field on the interface between the implant and the skull. Additionally, under the specific analyzed conditions, it is observable that the model with the implant offers more efficient brain protection when compared with the model with the integral skull.

Highlights

Cranioplasty is a medical-surgical procedure that aims to fill skull defects provoked by a craniectomy or skull fracture, recovering the skull’s protective function and bringing aesthetic satisfaction to patients
The holes situated near the impact zone led to increased stress concentrations near these holes, which is explained by the principles of fracture mechanics
For the models with five, six, and seven screws, the maximum von Mises stress was in the implant near the interface between implant and skull, while for the models with eight and nine screws, the maximum von Mises stress was in the region nearby the impact zone

Summary

Introduction

Cranioplasty is a medical-surgical procedure that aims to fill skull defects provoked by a craniectomy or skull fracture, recovering the skull’s protective function and bringing aesthetic satisfaction to patients. The human skull is a vital part of the human body, mainly because it has the task of protecting the brain, an essential organ of the human body. Skullbone is composed of both cortical bone and trabecular bone. Cortical bone is treated as a compact bone that acts as the outer layer of the skeleton, surrounding the trabecular bone and providing a hard covering for the skeleton [2]. The skull contains cranial sutures, which act as connectors of the skull bones and are composed mainly of collagen [3]. Since the brain is a susceptible organ and needs the protection of all parts that surrounds it against impact loads, a good indicator of the effectiveness of external components, such as a cranial implant, is their capacity to protect the brain against severe injuries. Traumatic brain injury (TBI) can be classified as a combination of two parameters: deformation processes due to brain motion and indentation processes on the skull (or implant) [4]

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