Marina Corral-Bobadilla

Using the Finite Element Method to Determine the Influence of Age, Height and Weight on the Vertebrae and Ligaments of the Human Spine

This study uses the Finite Element Method (FEM) to analyze the influence of age, height and weight on the vertebrae and ligaments of the human functional spinal unit (FSU). Two different artificial segments and the influence of the patient’s age, sex and height were considered. The FSU analyzed herein was based on standard human dimensions. It was fully parameterized first in engineering modelling format using CATIA© software. A combination of different elements (FE) were developed with Abaqus© software to model a healthy human FSU and the two different sizes of artificial segments. Healthy and artificial FSU Finite Element models (FE models) were subjected to compressive loads of differing values. Spinal compression forces, posture data and male/female anthropometry were obtained using 3DSSPP© software Heights ranging from 1.70 to 1.90 meters; ages, between 30 and 80 years and body weights between 75 and 90 kg were considered for both men and women. Artificial models were based on the Charite prosthesis. The artificial prosthesis consisted of two titanium alloy endplates and an ultra-high-molecular-weight polyethylene (UHMWPE) core. An analysis in which the contacts between the vertebrae and the intervertebral disc, as well as the behavior of the seven ligaments, were taken into consideration. The Von Mises stresses for both the cortical and trabecular bone of the upper and lower vertebrae, and the longitudinal stresses corresponding to the seven ligaments that connect the FSU were analyzed. The stresses obtained for the two geometries that were studied by means of the artificial FE models were very similar to the stresses that were obtained from healthy FE models.

The design of a knee prosthesis by Finite Element Analysis

The purpose of this paper is to study two types of knee prosthesis that are based on the Finite Element Method (FEM). The process to generate the Finite Element (FE) models was conducted in several steps. A 3D geometric model of a healthy knee joint was created using 3D scanned data from an anatomical knee model. This healthy model comprises a portion of the long bones (femur, tibia and fibula) as well as by the lateral and medial meniscus, cartilage and ligaments. The digital model that was obtained was repaired and converted to an engineering drawing format using CATIA© software. Based on the foregoing format, two types of artificial knee prostheses were designed and assembled. Mentat Marc© software was used to model the healthy and artificial knee FE models. The healthy and artificial knee FE models were subjected to different loads. The an-thropometry of the human body that was studied and the combination of loads to apply to the knee were obtained by use of 3D Static Strength Prediction software (3DSSPP©). The Von Mises stresses, as well as all the relative displacements of the components of the healthy and artificial knee FE model, were obtained from the Mentat Marc© software. The Von Mises stresses for both the cortical and the trabecular bone of the artificial and healthy knee FE model were analyzed and compared. The stresses that were obtained from the two knee prosthesis that were studied based on the artificial FE models were very similar to those stresses that were obtained from healthy FE models.