Design and Simulation in Biomedical Mechanics

Human bone tumors, severe trauma, and infection are the main causes of large bone defects. Currently, these defects are repaired using reconstruction plates that connect remaining bone, without any bone grafting. This study focuses on two aspects: the first, experimental testings using digital image correlation and secondly numerical testing studies in order to evaluate the influencing factors in the design of a custom prosthesis and maxillofacial applications. In this work, it is proposed to design and characterize a prototype mandibular prosthesis for hemimandibulectomy recovery class IVc to a patient with bone cancer. For the design and prototype, the physical and morphological characteristics of the patient as well as the strength properties of the used material are necessary. The mandibular prosthesis prototype design will be created based on the 3D reconstruction of the mandible of tomographic studies, which were obtained using the ScanIP software. Subsequently, the 3D models were exported to a CAD software in order to fix the necessary adaptations to the bone. The 3D models were printed in acrylonitrile butadiene styrene, and a digital image correlation was used in order to evaluate the residual stress and strain differences which can be observed in all the cases, also in the case of implants and the remaining healthy bone, caused by masticatory forces.

A numerical evaluation of an orthognathic prosthesis used in patients with facial asymmetry and mandibular prognathism was performed for this study. Mechanical testing was also performed by using axial tomography (computed tomography scan), and experimental methods such as photo-stress and image correlation were included. Our clinical case was a patient diagnosed with prominent mandible and abnormal size; atypical morphology, abnormal mastication and sense of smell, and difficulty talking as a consequence of the bone deformity; bad alignment of the mandible and upper maxilla, atypical movement of the tongue and deficiency for the occlusion process (closing of the mouth). This study aimed mainly to characterize the mechanical stress and structural behavior of numerical models obtained by the patient’s clinical and morphological profile through a computational approach based on the finite element method.

This work details the study of the effectiveness in the use of plates, as a treatment support during the fracture of a mandibular angle. It also analyzes the mechanical operation of the fissure repair plates on the jawbone using methods like finite element simulation and image correlation experimentation. With the purpose to evaluate the mechanical capacities of a new prototype plate compared to one of the commonly used namesakes, since the mechanical capacities of the new model are unknown.

The present study comprises a comparative exercise to determine stress, strain, and amorphic structural state in a hip prosthesis with the use of the photoelastic and image correlation technique. Several photoelastic models, some of them with a stochastic finish were created by the use of a computed tomography scan, stereolithographic three-dimensional printing, and rapid prototyping. Ideally, our results could yield a significant time reduction of techniques aimed to evaluate stress and strain of surgical models either pre or postoperatively.

In the present work, the effect of trauma impacts on the cranium and the influence of cranial brain fluid on the walls of the cranial vault are analyzed. Using experimental methods (photoelasticity and image correlation), as well as numerical methods with ANSYS Mechanical APDL^®, the results were studied in order to know the mechanical behavior in the surface of the cranial vault in which the cranial plates for replacement or reconstructive surgery for injuries by trauma (third degree) are required. Also, it would be considered as an economic and capable option for prosthesis which only considers titanium and stainless steel as material for the replacement.

Today, assisted design software offers more capacity and iterations, and its methodology optimally solves geometries with enough rigidity and weight, keeping their specific characteristics desirable for some design objectives, and thus achieving originality, affordable functionality and reproducibility through manufacturing systems such as three-dimensional manufacturing. For this reason, the present study uses a computerized generative design method to optimize the main components of a cranial distraction system aiming to perform a geometric optimization of the original components and preserving the actual mechanical performance in spite of reducing the weight of the distractor components. By the use of commercial software packages such as PTC Creo Parametric©, PTC Creo Simulate©, Frustum©, Autodesk fusion 360°©, and Solid edge©, several generative proposals were evaluated. These evaluations were performed under load and boundary in order to preserve the cranial distractor function and optimize the amount of material used by the additive manufacture technique.

This work proposes and demonstrates the application of Biomechanics to make printed designs in 3D systems, in order to improve customized prosthetic components. The study provides solutions that benefit patients with orthopedic area defects. In addition, the publication of this work will increase the scientific production and international recognition of the National Polytechnic Institute.

Equinovarus foot or known as clubfoot is a frequent musculoskeletal deformity occurring at birth. It comprises a misalignment of the foot and shortened tendons and produces pain and serious physical limitations. It occurs mainly in patients with cerebral palsy, duchenne muscular dystrophy, residual clubfoot deformity, and spina bifida. The initial gold standard treatment for an equinovarus foot is the structural correction with the use of ortheses aimed to allow the patient to walk and perform rehabilitation exercises. These ortheses come mainly in the form of boots molded with plaster of Paris or fiberglass bandages. Premanufactured ortheses are also available and yield great resistance and support to the foot; however, they can be very costly and out of reach for some population. Recently, our research center of investigation and biomechanics laboratory (CILAB), with the assistance of the Instituto Politécnico Nacional (IPN) started printing three-dimensional personalized ortheses for diverse musculoskeletal problems, including clubfoot patients aiming to lower the costs of treatment for our pediatric patients. Our preset study analyzed the resistance of two 3D printed ortheses: one for a normal subject and another for a clubfoot patient through optical interferometry and numerical analysis. Our purpose was to anticipate failure of our personalized designs, especially in cases, where the foot gait is abnormal such as in the case of clubfoot patients.

Scoliosis and lordosis are medical conditions, which present an atypical curvature of the spine. These deformations can be easily diagnosed, altogether with the degree of their severity through orthopedic measurement processes and clinical reviews. However, the preformed studies which classify the severity of these deformations are, in their majority, empirical and present great opportunity for improvement. Therefore, they are based on radiographies that offer a clear image of the spine, but present the problem of a constant patient’s exposition to ionizing radiation and as a consequence an increment of potential hazards for health. This also means, results are subject to the physician’s interpretation and expertise. The present work intends to describe and analyze the design and function of a mechanical system that is capable of significantly reducing the radiological exposure of patients with scoliosis and lordosis. The main goal of this device is to diagnose both deformations by obtaining the angles of curvature of the patient’s spine, using a method that does not depend entirely on human interpretation.