Bone Remodeling Under Vibration: A Computational Model of Bone Remodeling Incorporating the Modal Behavior of Bone
The objective of this study is to develop a bone remodeling algorithm that takes into account the effects of bone vibrational behavior. An extended/modified model is presented based on conventional finite element (FE) remodeling models. Frequency domain analysis is used to introduce appropriate correction coefficients to incorporate the effect of bone's frequency response (FR) into the model. The method is implemented on a bovine bone with known modal/vibration characteristics. The rate and locations of new bone formation depend on the loading frequency and are consistently correlated with the bone modal behavior. Results ...
Source: Journal of Biomechanical Engineering - September 25, 2018 Category: Biomedical Engineering Source Type: research

Comparative Fluid –Structure Interaction Analysis of Polymeric Transcatheter and Surgical Aortic Valves' Hemodynamics and Structural Mechanics
This study compares the polymeric SAVR valve's hemodynamic performance and mechanical stresses to a new version of the valve—specifically designed for TAVR. Fluid–structure interaction (FSI) mo dels were utilized and the valves' hemodynamics, flexural stresses, strains, orifice area, and wall shear stresses (WSS) were compared. The TAVR valve had 42% larger opening area and 27% higher flow rate versus the SAVR valve, while WSS distribution and mechanical stress magnitudes were of the same order, demonstrating the enhanced performance of the TAVR valve prototype. The TAVR valve FSI simulation and Vivitro pulse duplicato...
Source: Journal of Biomechanical Engineering - September 25, 2018 Category: Biomedical Engineering Source Type: research

Influence of Uncertainty in Selected Musculoskeletal Model Parameters on Muscle Forces Estimated in Inverse Dynamics-Based Static Optimization and Hybrid Approach
The purpose of the current study was to investigate the robustness of dynamic simulation results in the presence of uncertainties resulting from application of a scaled-generic musculoskeletal model instead of a subject-specific model as well as the effect of the choice of simulation method on the obtained muscle forces. The performed sensitivity analysis consisted of the following multibody parameter modifications: maximum isometric muscle forces, number of muscles, the hip joint center location, segment masses, as well as different dynamic simulation methods, namely static optimization (SO) with three different criteria ...
Source: Journal of Biomechanical Engineering - September 25, 2018 Category: Biomedical Engineering Source Type: research

A Study of the Mechanical Forces on Aphakic Iris-Fixated Intraocular Lenses
Iris-fixated aphakic intraocular lenses (IFIOL) are used in cataract surgery when more common intraocular lenses (IOL) cannot be adopted because of the absence of capsular bag support. These lenses can be implanted on either the posterior or the anterior surface of the iris. In this work, we study whether one of these options is preferable over the other from the mechanical point of view. In particular, we focus on the forces that the IFIOL transmits to the iris, which are associated with the risk of lens dislocation. We study the problem numerically and consider aqueous flow induced by saccadic rotations in the cases of a...
Source: Journal of Biomechanical Engineering - August 20, 2018 Category: Biomedical Engineering Source Type: research

Aortic Expansion Induces Lumen Narrowing in Anomalous Coronary Arteries: A Parametric Structural Finite Element Analysis
Anomalous aortic origin of coronary arteries (AAOCA) is a congenital disease that can lead to cardiac ischemia during intense physical activity. Although AAOCA is responsible for sudden cardiac death (SCD) among young athletes and soldiers, the mechanisms underlying the coronary occlusion during physical effort still have to be clarified. The present study investigates the correlation between geometric features of the anomaly and coronary lumen narrowing under aortic root dilatations. Idealized parametric computer-aided designed (CAD) models of the aortic root with anomalous and normal coronaries are created and static fin...
Source: Journal of Biomechanical Engineering - August 20, 2018 Category: Biomedical Engineering Source Type: research

Computational Fluid Dynamic Study for aTAA Hemodynamics: An Integrated Image-Based and Radial Basis Functions Mesh Morphing Approach
We present a novel framework for the fluid dynamics analysis of healthy subjects and patients affected by ascending thoracic aorta aneurysm (aTAA). Our aim is to obtain indications about the effect of a bulge on the hemodynamic environment at different enlargements. Three-dimensional (3D) surface models defined from healthy subjects and patients with aTAA, selected for surgical repair, were generated. A representative shape model for both healthy and pathological groups has been identified. A morphing technique based on radial basis functions (RBF) was applied to mold the shape relative to healthy patient into the represen...
Source: Journal of Biomechanical Engineering - August 20, 2018 Category: Biomedical Engineering Source Type: research

The Size of Simulated Lytic Metastases Affects the Strain Distribution on the Anterior Surface of the Vertebra
Metastatic lesions of the vertebra are associated with risk of fracture, which can be disabling and life-threatening. In the literature, attempts are found to identify the parameters that reduce the strength of a metastatic vertebra leading to spine instability. However, a number of controversial issues remain. Our aim was to quantify how the strain distribution in the vertebral body is affected by the presence and by the size of a simulated metastatic defect. Five cadaveric thoracic spine segments were subjected to non-destructive presso-flexion while intact, and after simulation of metastases of increasing size. For the ...
Source: Journal of Biomechanical Engineering - August 20, 2018 Category: Biomedical Engineering Source Type: research

Osteoporotic Hip Fracture Prediction: Is T-Score-Based Criterion Enough? A Hip Structural Analysis-Based Model
At present, the current gold-standard for osteoporosis diagnosis is based on bone mineral density (BMD) measurement, which, however, has been demonstrated to poorly estimate fracture risk. Further parameters in the hands of the clinicians are represented by the hip structural analysis (HSA) variables, which include geometric information of the proximal femur cross section. The purpose of this study was to investigate the suitability of HSA parameters as additional hip fracture risk predictors. With this aim, twenty-eight three-dimensional patient-specific models of the proximal femur were built from computed tomography (CT...
Source: Journal of Biomechanical Engineering - August 20, 2018 Category: Biomedical Engineering Source Type: research

Abdominal Aortic Aneurysm Endovascular Repair: Profiling Postimplantation Morphometry and Hemodynamics With Image-Based Computational Fluid Dynamics
Endovascular aneurysm repair (EVAR) has disseminated rapidly as an alternative to open surgical repair for the treatment of abdominal aortic aneurysms (AAAs), because of its reduced invasiveness, low mortality, and morbidity rate. The effectiveness of the endovascular devices used in EVAR is always at question as postoperative adverse events can lead to re-intervention or to a possible fatal scenario for the circulatory system. Motivated by the assessment of the risks related to thrombus formation, here the impact of two different commercial endovascular grafts on local hemodynamics is explored through 20 image-based compu...
Source: Journal of Biomechanical Engineering - August 20, 2018 Category: Biomedical Engineering Source Type: research

Nonlinear Analysis of Human Movement Dynamics Offers New Insights in the Development of Motor Control During Childhood
When aiming at assessing motor control development, natural walking (NW), and tandem walking (TW) are two locomotor tasks that allow analyzing different characteristics of motor control performance. NW is the reference locomotor task, expected to become more and more automatic with age. TW is a nonparadigmatic task used in clinics to highlight eventual impairments and to evaluate how a child deals with a new challenging motor experience. This work aims at investigating motor development in school-aged children, by assessing quantitatively their performance during TW and NW. Eighty children (6 –10 years) participated in t...
Source: Journal of Biomechanical Engineering - August 20, 2018 Category: Biomedical Engineering Source Type: research

Residual Stresses in Titanium Spinal Rods: Effects of Two Contouring Methods and Material Plastic Properties
This study aims at investigating two rod contouring strategies, French bender (FB) contouring (clinical gold standard), and uniform contouring, through validated FE models. A careful characterization of the elastoplastic material response of commercial implants is led. Compared to uniform contouring, FB induces highly localized plasticizations in compression under the contouring pin with extensive lateral sections undergoing tensile residual stresses. The sensitivity analysis highlighted that the assumed postyielding properties significantly affect the numerical predictions; therefore, an accurate material characterization...
Source: Journal of Biomechanical Engineering - August 20, 2018 Category: Biomedical Engineering Source Type: research

Finite Element Analysis to Probe the Influence of Acetabular Shell Design, Liner Material, and Subject Parameters on Biomechanical Response in Periprosthetic Bone
This study recommends the use of the finned design, particularly for weaker bone conditions. For stronger bones, the combined design may also be recommended for higher stability. The use of HC-UHMWPE liner was found to be better for convensional shell design. However, similar biomechanical response was captured in our FE analysis for both the liner materials in case of other shell designs. Overall, the study establishes the biomechanical response of periprosthetic bone in the acetabular with preclinically tested liner materials together with new shell design for different subject conditions. (Source: Journal of Biomechanical Engineering)
Source: Journal of Biomechanical Engineering - July 3, 2018 Category: Biomedical Engineering Source Type: research

Sensitivity of Arterial Hyperelastic Models to Uncertainties in Stress-Free Measurements
Despite major advances made in modeling vascular tissue biomechanics, the predictive power of constitutive models is still limited by uncertainty of the input data. Specifically, key measurements, like the geometry of the stress-free (SF) state, involve a definite, sometimes non-negligible, degree of uncertainty. Here, we introduce a new approach for sensitivity analysis of vascular hyperelastic constitutive models to uncertainty in SF measurements. We have considered two vascular hyperelastic models: the phenomenological Fung model and the structure-motivated Holzapfel –Gasser–Ogden (HGO) model. Our results indicate u...
Source: Journal of Biomechanical Engineering - July 2, 2018 Category: Biomedical Engineering Source Type: research

Acute Surgical Injury Alters the Tensile Properties of Thoracolumbar Fascia in a Porcine Model
This study used a porcine injury model (microsurgically induced local injury) —shown to produce similar results to those observed in humans with LBP—to test the hypothesis that TLF mechanical properties may also be altered in patients with LBP. Perimuscular TLF tissue was harvested from the noninjured side of vertebral level L3-4 in pigs randomized into either control (n  = 5) or injured (n = 5) groups. All samples were tested with a displacement-controlled biaxial testing system using the following protocol: cyclic loading/unloading and stress relaxation tests at 25%, 35%, and then 45% of their resting length....
Source: Journal of Biomechanical Engineering - July 2, 2018 Category: Biomedical Engineering Source Type: research

An Ergonomic Testing System for the First Metatarsophalangeal Joint Stiffness
Osteoarthritis sufferers commonly have first metatarsophalangeal joint (MTPJ) problems in which articular surfaces are changed permanently due to fatigue. Therefore, medical devices for early diagnosis would increase the opportunity for prevention of disease progression. In previous studies on stiffness of the first MTPJ many details, although functionally of great importance, have not been fully considered including: design and size of the device, tribology consideration, and errors from device. Therefore, the motivation of our research was to enhance the device design by reducing the size of the device, and device design...
Source: Journal of Biomechanical Engineering - June 21, 2018 Category: Biomedical Engineering Source Type: research