Mechanical Strength Study of a Cranial Implant Using Computational Tools

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.

Effects of Pentagonal Pore Sizes in the Zinc Hydroxyapatite Parietal-Temporal Implant

To reconstruct the fractured skull, affected patients are advised to undergo cranioplasty, which is a surgical procedure to repair the cranial defect by implanting materials such as autologous bone grafts or synthetic alloplastic materials. The use of synthetic alloplastic materials such as hydroxyapatite (HA) has been widely accepted due to their biocompatibility and suitability for larger cranial defects. The zinc hydroxyapatite (ZnHA) material is favourable as HA mimics 60% of the actual human bone, whereas zinc helps to improve its biomechanical properties. The purpose of this study is to construct the ZnHA cranial implant with different pore sizes of 600, 900, and 1200 µm in pentagonal shapes and to study its mechanical performance. At the end of the research, it was found that the implant with a pore size of 900 µm is the most appropriate implant to be utilized without affecting its mechanical performance. Aspects such as the deformation and von Mises stress are discussed to assist on the development of the ZnHA cranial implant. Keywords — Biomechanical analysis, cranial implant, finite element analysis, pore size, zinc hydroxyapatite

A New Methodology for Designing a Skull Implant

Cranioplasty is a surgery used to repair a bone defect in the skull caused by an injury. It involves lifting the scalp and restoring the contour of the skull with an implant usually manufactured by additive manufacturing. The cranial implant is a sensitive topic; thus, it must be manufactured to the highest standards. Medical implants are growing significantly due to industrial digitalization and the rapid development of industrial software. With the help of computed Tomography (CT) equipment, a spatial, rotating model of the patient's current state can be obtained quickly, even in minutes where the replacement part of the deficiency can be perfectly designed. Although this requires considerable routine, computational capacity, and time, but taking advantage of the latest software presented in our manuscript, the development time of the implant can be up to 50 times shorter with significant improvements in suitability and adaptability. Subsequently, we can produce more accurate implants with more accessible and faster manufacturing with our developed method. The development steps and methods of designing an implant are described in our article.

Cranial Implant Design Applying Shape-Based Interpolation Method via Open-Source Software

Reconstructing a large skull defect is a challenge, as it normally involves the use of sophisticated proprietary image processing and expensive CAD software. As an alternative, open-source software can be used for this purpose. This study aimed to compare the 3D cranial implants reconstructed from computed tomography (CT) images using the open-source MITK software with commercial 3-matic software for ten decompressive craniectomy patients. The shape-based interpolation method was used, in which the technique of segmenting every fifth and tenth slice of CT data was performed. The final design of patient-specific implants from both software was exported to STL format for analysis. The results of the Kruskal–Wallis test for the surface and volume of cranial implants designed using 3-matic and the two MITK techniques showed no significant difference, p > 0.05. The results of the Hausdorff Distance (HD) and Dice Similarity Coefficient (DSC) analyses for cranial implants designed using 3-matic software and the two different MITK techniques showed that the average points distance for 3-matic versus MITK was 0.28 mm (every tenth slice) and 0.15 mm (every fifth slice), and the similarity between 3-matic and MITK on every tenth and fifth slices were 85.1% and 89.7%, respectively. The results also showed that the open-source MITK software is comparable with the commercial software for designing patient-specific implants.