SIMBIO-M 2014, SIMulation technologies in the fields of BIO-Sciences and Multiphysics: BioMechanics, BioMaterials and BioMedicine, Marseille, France, june 2014

Proceedings de la 3ème édition de la conférence internationale Simbio-M (2014). Organisée conjointement par l'IFSTTAR, Aix-Marseille Université, l'université de Coventry et CADLM, cette conférence se concentre sur les progrès des technologies de simulation dans les domaines des sciences du vivant et multiphysiques: Biomécanique, Biomatériaux et Biomédical. L'objectif de cette conférence est de partager et d'explorer les résultats dans les techniques d'analyse numérique et les outils de modélisation mathématique. Cette approche numérique permet des études prévisionnelles ou exploratoires dans les différents domaines des biosciences

Utilization of Finite Element Analysis Techniques for Adolescent Idiopathic Scoliosis Surgical Planning

Adolescent Idiopathic Scoliosis, a three-dimensional deformity of the thoracolumbar spine, affects approximately 1-3% of patients ages 10-18. Surgical correction and treatment of the spinal column is a costly and high-risk task that is consistently complicated by factors such as patient-specific spinal deformities, curve flexibility, and surgeon experience. The following dissertation utilizes finite element analysis to develop a cost-effective, building-block approach by which surgical procedures and kinematic evaluations may be investigated. All studies conducted are based off a volumetric, thoracolumbar finite element (FE) model developed from computer-aided design (CAD) anatomy whose components are kinematically validated with in-vitro data. Spinal ligament stiffness properties derived from the literature are compared for kinematic assessment of a thoracic functional spinal unit (FSU) and benchmarked with available in-vitro kinematic data. Once ligament stiffness properties were selected, load sharing among soft tissues (e.g., ligaments and intervertebral disc) within the same FSU is then assessed during individual steps of a posterior correction procedure commonly used on scoliosis patients. Finally, the entire thoracolumbar spine is utilized to mechanically induce a mild scoliosis profile through an iterative preload and growth procedure described by the Hueter-Volkmann law. The mild scoliosis model is then kinematically compared with an asymptomatic counterpart. The thoracic deformation exhibited in the mild scoliosis model compared well with available CT datasets. Key findings of the studies confirm the importance of appropriately assigning spinal ligament properties with traditional toe and linear stiffness regimes to properly characterize thoracic spine FE models. Stiffness properties assigned within spinal FE models may also alter how intact ligaments and intervertebral discs respond to external loads during posterior correction procedures involving serial ligament removal, and thus can affect any desired post-surgical outcomes. Lastly, the thoracolumbar spine containing mild scoliosis experiences up to a 37% reduction in global range of motion compared to an asymptomatic spine, while also exhibiting larger decreases in segmental axial rotations at apical deformity levels. Future studies will address kinematic behavior of a severe scoliosis deformity and set the stage for column-based osseoligamentous load sharing assessments during surgical procedures

Design and development of a MEMS-based capacitive bending strain sensor and a biocompatible housing for a telemetric strain monitoring system.

Lumbar arthrodesis or spinal fusion is usually performed to relieve back pain and regain functionality from ruptured discs, disc degenerative disease, trauma and scoliosis. Metal rods are often fixed to the spine with screws or hooks, while fusion develops on the affected vertebrae. Fusion is determined by visual examination of radiographic images (X-ray), computed tomography (CT) scans or magnetic resonance imaging (MRI), yet these inspection procedures are subjective methods of review. They do not objectively confirm the presence of spinal fusion, which can lead to exploratory surgery to determine if fusion has occurred. Therefore, a need has arisen to develop an objective method that will offer unbiased information for the determination of fusion. Discussed herein is a housing and sensor designed to be used in conjunction with telemetric circuitry that will attach to the spinal instrumentation rods. The housing will transmit strain to an internatal capacitive MEMS-based sensor that will relay strain magnitudes via telemetry. Observed reductions of bending strain will indicate a successful fusion. These objective assessments will reduce the incidence of costly exploratory surgeries where fusion is in question. The housing design was fabricated using Polyetheretherketone (PEEK) material, which was selected for its physical properties and its ability to be implanted for long durations. The housing was tested under cyclical, static and maximum strain transfer loading configurations in the Material Testing System (MTS). Results from these tests demonstrated that the housing transferred 102% of the bending strain and successfully met the design criteria. Additionally, a MEMS-based sensor was developed to change the capacitance with detected alterations in bending strain transmitted through the housing. Sensors were fabricated using microfabrication techniques and highly doped boron silicon wafers to create a transverse comb drive or an interdigitated finger array. The sensor was tested using similar methods that were used for the housing. Results from cyclical testing demonstrated the sensor\u27s response needed to be increased 50% and it did not exhibit any capacitance drift

An EMG-Driven Cervical Spine Model for the Investigation of Joint Kinetics: With Application to a Helicopter Pilot Population

As the workforce has been shifting from manufacturing to office work, reports of neck pain have been on the rise. Unfortunately, the mechanism for the development of chronic neck pain still remains disputed. Most current cervical spine biomechanical models are aimed at the simulation of whiplash and are forward models employing the finite element method or multibody dynamics that are ill-equipped for incorporating motion capture data, with even fewer models capable of interfacing with electromyography (EMG) data. Therefore, there is a considerable opportunity to develop an inverse dynamic model that can drive muscle forces using EMG with the goal of determining the joint mechanics that could lend insight to the loading patterns and injury mechanics in the cervical spine. The current model is an inverse dynamic multi-body model of the whole cervical spine, head, and thorax. It was created entirely in Python, using anatomical data obtained from the Anatomography project, which were rescaled to match dimensions from a 50th percentile male. Constitutive expressions for ligaments are described by nonlinear springs, while the disc and facet joints are lumped into exponential rotational springs. Active muscle forces are estimated from EMG using a Hill-type muscle modeling framework. The model has endured a rigorous validation procedure comparing its predicted compression and shear values to a previously published model. The gains for each muscle were analyzed to evaluate how well muscle forces are being predicted from EMG. Finally, a sensitivity analysis was conducted to identify if the outputs of the model were overly dependent on the numeric value of a specific parameter. Overall, compression and mediolateral shear values were in good agreement with the previous model, while anteroposterior shear values were significantly smaller in magnitude. Despite this, muscle gains were, in some cases, alarmingly high. Finally, the sensitivity analysis revealed that the model is somewhat sensitive to ligament and muscle slack lengths, albeit to a much lesser extent than previously published models. The model was used to evaluate the change in joint kinetics with a flexed posture compared to a neutral one. With 45 degrees of flexion, compressive forces increased twofold throughout the cervical spine. In addition, anteroposterior shear tended to increase fourfold in the upper cervical spine, however, equalized with a neutral posture around the C4-C5 level. These findings may have implications for injury mechanisms, as a flexed posture under compression has been strongly associated with the development of posterior disc prolapse. In addition, the model was used to assess the joint kinetics from an existing data set on helicopter pilots who are required to wear night vision goggles during night flights. The classic solution to the anteriorly placed weight of the night vision goggles has been to counterbalance it with a posterior counterweight. While this works theoretically in a neutral posture, once a deviated posture is assumed, joint kinetics correspondingly increase. Adding a helmet increased the compression at C5-C6 from 204 N to 258 N, a 26% increase. Furthermore, adding night vision goggles and a counterweight increased it by 60%. Increasing the mass of the head-segment leads to an increase of compression

Advanced Applications of Rapid Prototyping Technology in Modern Engineering

Rapid prototyping (RP) technology has been widely known and appreciated due to its flexible and customized manufacturing capabilities. The widely studied RP techniques include stereolithography apparatus (SLA), selective laser sintering (SLS), three-dimensional printing (3DP), fused deposition modeling (FDM), 3D plotting, solid ground curing (SGC), multiphase jet solidification (MJS), laminated object manufacturing (LOM). Different techniques are associated with different materials and/or processing principles and thus are devoted to specific applications. RP technology has no longer been only for prototype building rather has been extended for real industrial manufacturing solutions. Today, the RP technology has contributed to almost all engineering areas that include mechanical, materials, industrial, aerospace, electrical and most recently biomedical engineering. This book aims to present the advanced development of RP technologies in various engineering areas as the solutions to the real world engineering problems

Control of the Mechanical Properties of the Synthetic Anterior Longitudinal Ligament and its Effect on the Mechanical Analogue Lumbar Spine Model

The development and validation of an anatomically correct mechanical analogue spine model would serve as a valuable tool in helping researchers and implant designers understand and alleviate low back pain. Advanced composite ligaments were designed to mimic the tensile mechanical properties of human spinal ligaments. By changing the composite properties, the stiffness and deformation at toe were controlled in a repeatable manner. Five analogue spine models, with three different Anterior Longitudinal Ligament (ALL) stiffness configurations, were tested in bending and compression using displacement control in a MTS load frame. The bending stiffness and kinematic ranges of motion of the spines were compared for each ALL stiffness configuration. The ALL stiffness had a significant effect on the stiffness and peak moment in extension of the overall spine model. The study demonstrated that a change in the synthetic ligament properties successfully controls the biomechanics of the analogue spine model and the model effectively mimics the human cadaveric biomechanical response

Biomechanical investigation of a new implant for cervical spine fusion

The project consists of: - mechanical tests of the prototype of the new implant and comparison to existing anterior fixation systems in a bone model material; - a literature review in order to classify the test results; - the development of a finite element model for the tension case, which will be validated by the mechanical tests

Natural Degradation: Polymer Degradation under Different Conditions

This book focuses on some fundamental issues of polymers’ natural degradation. It is mostly devoted to the different aspects of biodegradation, but some data on the action of water, oxygen, ozone, and UV/Vis light is also included. The consideration of the biodegradation in vivo as the superposition of decay and synthesis provides the opportunity for a fresh look at well-known processes