The Bullard laryngoscope for emergency airway management in a morbidly obese parturient.
Explore the source record for details and available documents.
Adult↗
Biomedical subjects
R T Hart
Publications and source records attributed to R T Hart.
Modeling the biomechanics of the mandible: a three-dimensional finite element study.
Three-dimensional finite element models of a partially edentulated human mandible were generated to calculate the mechanical response to simulated isometric biting and mastication loads. The level of mesh refinement was established via a convergence test and showed that a model with over 30,000 degrees of freedom was required to obtain analysis accuracy. The functional loading cases included muscle loading based on an algorithm that assigns muscle forces in accordance with muscle cross-sectional area, while maintaining static equilibrium. Results were found for isometric application of unilateral and bilateral bite and mastication loading, and two different sets of displacement boundary conditions were imposed at the condyles. The mechanical response is shown in terms of displacements, principal strains, and a new measure called the 'mechanical intensity scalar'. For each load case studied, there was substantial bending in the molar region of the corpus and high tensile strains in the anterior portion of the ramus.
Bicuspid↗
Finite-element model of the human head: scalp potentials due to dipole sources.
Three-dimensional finite-element models provide a method to study the relationship between human scalp potentials and neural current sources inside the brain. A new formulation of dipole-like current sources is developed here. Finite-element analyses based on this formulation are carried out for both a three-concentric-spheres model and a human-head model. Differences in calculated scalp potentials between these two models are studied in the context of the forward and inverse problems in EEG. The effects of the eye orbit structure on surface potential distribution are also studied.
Action Potentials↗
A theoretical study of the influence of bone maturation rate on surface remodeling predictions: idealized models.
The use of a finite element based computational method, RFEM3D, is described for the study of strain-induced bone remodeling. The purpose of the research is to find the potential influence on the predictions of surface bone remodeling when various models for the maturation of newly deposited bone are used. A parameter study is performed using seven hypothetical mechanical descriptions of the bone maturation process. The results show that, theoretically, the process of surface bone maturation may be an efficient mechanism for reducing overload strains in bone, but that differences as a consequence of using any of the proposed maturation rules are rather subtle.
Biomechanical Phenomena↗
Errors in the orientation of the principal stress axes if bone tissue is modeled as isotropic.
The error in the prediction of the orientation of the principal axes of stress in bone tissue is determined in the case when the tissue is modeled as elastically isotropic rather than as orthotropic, the probable symmetry of bone tissue. Results are two-dimensional and assume the same underlying strain state for both the orthotropic and isotropic cases. The maximum error is 45 degrees, and the typical error is generally significant.
Biomechanical Phenomena↗
Functional adaptation in long bones: establishing in vivo values for surface remodeling rate coefficients.
In this paper we describe a computational means, based on beam theory, for application of the theory of adaptive elasticity to examples of real bone geometries. The results of the animal experiments were taken from the literature, and each documented the temporal evolution of a change in bone shape after a significant change in the mechanical loading environment of the bone. For each of these studies, we establish preliminary estimates of the in vivo values of the surface remodeling rate coefficients--the key parameters in the theory of surface remodeling. Our preliminary parameter estimates are established by comparison of published animal experimental results with surface remodeling theory predictions generated by the computational method.
Adaptation, Physiological↗
Mathematical modeling and numerical solutions for functionally dependent bone remodeling.
The phenomenon of bone remodeling is a complex biological process which is dependent on genetic, hormonal, metabolic, and age-related factors as well as functional requirements. The possibility of successfully developing a mathematical model to describe and predict the adaptive response of bone to load will be significantly increased after identification of the nature of the transducer(s) which senses functional requirements and provides signals for the cellular processes responsible for bone synthesis and bone removal. In spite of the present limitations in knowledge about the functional dependence of bone remodeling, a phenomenological model has been developed that assumes that the output signal from the (as yet unspecified) transducer is a remodeling potential that can be modulated by genetic, hormonal, and metabolic factors. An attempt has been made to cast the mathematical model in such a form that the constants and variables appearing in the equations are not mere abstractions, but can be related to biological parameters. In order to use the adaptive hypothesis with specific structural model examples, a numerical procedure has been developed to determine the strain distribution, predict the remodeling (assuming that the remodeling rate is related to the strain history), and update the model by changing the geometry and material properties in response to the remodeling. This numerical procedure is repeatedly iterated to determine the structural architecture at subsequent times. The numerical approach allows use of the remodeling concepts with models of irregular geometry, inhomogeneous material distribution, and anisotropic material properties.
Adaptation, Physiological↗
A computational method for stress analysis of adaptive elastic materials with a view toward applications in strain-induced bone remodeling.
A computational method has been developed to obtain numerical results in the stress analysis of adaptive elastic materials. The method is based on a 3-dimensional finite element model that can change geometry and material properties based on the local strain. The solution procedure is iterative; the model is updated in time steps based on the current remodeling to provide incremental remodeling predictions. The method provides a vehicle for examination of different continuum models and their corresponding parameters for strain-induced remodeling in long bone. Use of the method with simple models of theoretical interest is presented. Results show agreement with available analytical results as well as the importance of coupled remodeling effects not previously examined.
Adaptation, Physiological↗
Load-bearing capacity of the tibial component of the total condylar knee prosthesis. An in vitro study.
The load-bearing capability of the tibial component of total knee prostheses is affected by the coverage of the osteotomized tibial surface by the tibial component. An anthropometric study of the proximal tibia indicated that standard total condylar tibial knee components may significantly underutilize the available weight-bearing tibial surface. The unloaded area values ranged from 6% to 43% in males and from 1% to 25% in females. An experimental study of the load-bearing capability of both standard tibial components and tibial components custom-fitted to conform to the periphery of the upper tibial surface was performed. Improvement in single load to failure with the conforming prosthesis averaged 29% in females with stemless prosthesis, 21% in females with stemmed prostheses, 41% in males with stemless prostheses, and 89% in males with stemmed prostheses. Post-test examination of the failed tibiae with conforming implants indicated failure by major fragmenting of the proximal tibia rather than cancellous bone crushing, suggesting that the maximal load-bearing ability of the upper tibial surface was more nearly being achieved. The results demonstrate the benefit to be gained by fully utilizing the available tibial surface for load transmission across the joint and suggest that use of custom-fitted tibial components has considerable merit.
Anthropometry↗