RESUMEN
Edentulism with associated severe bone loss is a widespread condition that hinders the use of common dental implants. An additively manufactured subperiosteal jaw implant (AMSJI) was designed as an alternative solution for edentulous patients with Cawood and Howell class V-VIII bone atrophy. A biomechanical evaluation of this AMSJI for the maxilla in a Cawood and Howell class V patient was performed via finite-element analysis. Occlusal and bruxism forces were incorporated to assess the loading conditions in the mouth during daily activities. The results revealed a safe performance of the implant structure during the foreseen implantation period of 15 years when exerting average occlusion forces of 200 N. For the deteriorated state of class VIII bone atrophy, increased stresses on the AMSJI were evaluated, which predicted implant fatigue. In addition, excessive bruxism and maximal occlusion forces might induce implant failure due to fatigue. The models predicted bone ingrowth at the implant scaffolds, resulting in extra stability and secondary fixation. For all considered loading conditions, the maximal stresses were located at the AMSJI arms. This area is most sensitive to bending forces and, hence, allows for further design optimization. Finally, the implant is considered safe for normal daily occlusion activities.
Asunto(s)
Implantes Dentales , Arcada Edéntula , Diseño de Prótesis Dental , Prótesis Dental de Soporte Implantado , Análisis de Elementos Finitos , Humanos , Arcada Edéntula/cirugía , Maxilar/cirugía , Estrés MecánicoRESUMEN
This study aimed to reconstruct four real life vehicle-bicycle collisions and evaluates the reconstruction parameters that affect the outcome of head injuries in report based accident reconstructions. A computational model of a car was developed in the multibody software MADYMO (MAthematical DYnamic MOdeling) and was used together with a validated bicycle model and the MADYMO 50 percentile pedestrian model. The accidents were reconstructed through an optimal fit method, based on kinematic and medical information. After the reconstruction, a parametric study on cyclists' movement and accident conditions was performed on the different cases. The velocity of the car and the angle of impact were found to significantly affect the accident outcome. This was demonstrated in terms of head injury criteria such as the Head Injury Criterion (HIC), the peak linear and peak angular velocity and acceleration. It was shown that the severity of the injury increases exponentially with increasing collision velocities. Additionally, the bicycle's parameters; crank rotation, handlebar angle and seat position revealed a large heterogeneity in the results. The maximum alteration between the lowest and highest HIC-value found for a complete crank rotation was a 416 % difference. For a handlebar rotation up to 100° or seat height alteration of maximum 34 cm, this value was respectively 169 % and 294 %. These high percentages of change indicate the need for cycling phase information for case-specific vehicle-bicycle accident reconstructions.
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Traumatismos Craneocerebrales , Peatones , Aceleración , Accidentes de Tránsito , Ciclismo , Fenómenos Biomecánicos , HumanosRESUMEN
The muscle footprint anatomy of the clavicle is described in various anatomical textbooks but research on the footprint variation is rare. Our goal was to assess the variation and to create a probabilistic atlas of the muscle footprint anatomy. 14 right and left clavicles of anatomical specimens were dissected until only muscle fibers remained. 3D models with muscle footprints were made through CT scanning, laser scanning and photogrammetry. Then, for each side, the mean clavicle was calculated and non-rigidly registered to all other cadaveric bones. Muscle footprints were indicated on the mean left and right clavicle through the 1-to-1 mesh correspondence which is achieved by non-rigid registration. Lastly, 2 probabilistic atlases from the clavicle muscle footprints were generated. There was no statistical significant difference between the surface area (absolute and relative), of the originally dissected muscle footprints, of male and female, and left and right anatomical specimens. Visualization of all muscle footprints on the mean clavicle resulted in 72% (right) and 82% (left) coverage of the surface. The Muscle Insertion Footprint of each specimen covered on average 36.9% of the average right and 37.0% of the average left clavicle. The difference between surface coverage by all MIF and the mean surface coverage, shows that the MIF location varies strongly. From the probabilistic atlas we can conclude that no universal clavicle exists. Therefore, patient-specific clavicle fracture fixation plates should be considered to minimally interfere with the MIF. Therefore, patient-specific clavicle fracture fixation plates which minimally interfere with the footprints should be considered.
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Variación Biológica Individual , Clavícula/anatomía & histología , Músculo Esquelético/anatomía & histología , Clavícula/diagnóstico por imagen , Femenino , Humanos , Imagenología Tridimensional , Masculino , Modelos Anatómicos , Músculo Esquelético/diagnóstico por imagen , Tomografía Computarizada EspiralRESUMEN
As the smallest functional unit of force production, the sarcomeres are important in determining muscle function. Actin filament lengths, which are important in determining optimal sarcomere length for a species, have not yet been reported in dogs. This study aims to provide a species-specific value for actin filament length in dogs, while examining intraspecies, intermuscular and intramuscular variations. Muscle samples were taken from the tibialis anterior muscle, the lateral gastrocnemius muscle head and the medial gastrocnemius muscle head in 10 dogs including a Labrador, a Belgian Malinois, a Caucasian Shepherd, German Shepherds and some mixed-breed dogs. Actin filament lengths were determined through transmission electron microscopy. Mean actin filament length across all muscle samples was 0.90 ± 0.01 µm. The low intraspecies variation, combined with a lack of important inter- and intramuscular variation found in this study, affirms the use of a species-specific optimal sarcomere length of 1.89 µm for canine muscles.
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Citoesqueleto de Actina/ultraestructura , Sarcómeros/ultraestructura , Animales , Perros , Contracción Muscular/fisiología , Músculo Esquelético/fisiología , Músculo Esquelético/ultraestructura , Sarcómeros/fisiologíaRESUMEN
OBJECTIVE: This study aims to characterize the deformations in articular cartilage under compressive loading and link these to changes in the extracellular matrix constituents described by magnetic resonance imaging (MRI) relaxation times in an experimental model mimicking in vivo cartilage-on-cartilage contact. DESIGN: Quantitative MRI images, T1, T2 and T1ρ relaxation times, were acquired at 9.4T from bovine femoral osteochondral explants before and immediately after loading. Two-dimensional intra-tissue displacement and strain fields under cyclic compressive loading (350N) were measured using the displacement encoding with stimulated echoes (DENSE) method. Changes in relaxation times in response to loading were evaluated against the deformation fields. RESULTS: Deformation fields showed consistent patterns among all specimens, with maximal strains at the articular surface that decrease with tissue depth. Axial and transverse strains were maximal around the center of the contact region, whereas shear strains were minimal around the contact center but increased towards contact edges. A decrease in T2 and T1ρ was observed immediately after loading whereas the opposite was observed for T1. No correlations between cartilage deformation patterns and changes in relaxation times were observed. CONCLUSIONS: Displacement encoding combined with relaxometry by MRI can noninvasively monitor the cartilage biomechanical and biochemical properties associated with loading. The deformation fields reveal complex patterns reflecting the depth-dependent mechanical properties, but intra-tissue deformation under compressive loading does not correlate with structural and compositional changes. The compacting effect of cyclic compression on the cartilage tissue was revealed by the change in relaxation time immediately after loading.
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Cartílago Articular/fisiología , Soporte de Peso/fisiología , Animales , Cartílago Articular/diagnóstico por imagen , Bovinos , Fuerza Compresiva/fisiología , Fémur/diagnóstico por imagen , Fémur/fisiología , Imagen por Resonancia Magnética/métodos , Rodilla de Cuadrúpedos/diagnóstico por imagen , Rodilla de Cuadrúpedos/fisiología , Estrés MecánicoRESUMEN
OBJECTIVE: The objective of this study was to evaluate the effect of full-thickness chondral defects on intratissue deformation patterns and matrix constituents in an experimental model mimicking in vivo cartilage-on-cartilage contact conditions. DESIGN: Pairs of bovine osteochondral explants, in a unique cartilage-on-cartilage model system, were compressed uniaxially by 350 N during 2 s loading and 1.4 s unloading cycles (≈1700 repetitions). Tissue deformations under quasi-steady state load deformation response were measured with displacement encoded imaging with stimulated echoes (DENSE) in a 9.4 T magnetic resonance imaging (MRI) scanner. Pre- and post-loading, T1, T2 and T1ρ relaxation time maps were measured. We analyzed differences in strain patterns and relaxation times between intact cartilage (n = 8) and cartilage in which a full-thickness and critical sized defect was created (n = 8). RESULTS: Under compressive loading, strain magnitudes were elevated at the defect rim, with elevated tensile and compressive principal strains (Δϵmax = 4.2%, P = 0.02; Δϵmin = -4.3%, P = 0.02) and maximum shear strain at the defect rim (Δγmax = 4.4%, P = 0.007). The opposing cartilage showed minimal increase in strain patterns at contact with the defect rim but decreased strains opposing the defect. After defect creation, T1, T2 and T1ρ relaxation times were elevated at the defect rim only. Following loading, the overall relaxations times of the defect tissue and especially at the rim, increased compared to intact cartilage. CONCLUSIONS: This study demonstrates that the local biomechanical changes occurring after defect creation may induce tissue damage by increasing shear strains and depletion of cartilage constituents at the defect rim under compressive loading.
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Cartílago Articular/lesiones , Cartílago Articular/fisiopatología , Animales , Cartílago Articular/diagnóstico por imagen , Bovinos , Fémur/diagnóstico por imagen , Fémur/fisiopatología , Imagen por Resonancia Magnética/métodos , Estrés Mecánico , Soporte de Peso/fisiologíaRESUMEN
Although the form-function relation of muscles and tendons has been studied extensively, little in vivo data exist on the musculotendon properties of the gastrocnemius complex in dogs. Using a combination of ultrasound and 3D motion tracking, musculotendon parameters were obtained in vivo from the lateral gastrocnemius muscle and the gastrocnemius tendon in nine healthy Labrador Retrievers. These parameters include musculotendon length and excursion potential, tendon slack length, muscle belly length, muscle fibre length, pennation angle and architectural index. This study also examined the variation of muscle and tendon length contributions to musculotendon length, as well as the relation between musculotendon excursion potential and muscle fibre length or tendon length. To facilitate comparison between dog breeds, the femur length as a potential scaling parameter was examined. In the Labrador gastrocnemius musculotendon complex, the tendon contributes 41% (± 9%) of musculotendon length. In longer musculotendon complexes, the contribution of the muscle belly increases while the tendon contribution decreases. Longer muscle belly and musculotendon complexes were, however, associated with shorter muscle fibres. No significant relations were found between musculotendon excursion potential and muscle fibre length or tendon slack length, and femur length did not prove to be a reliable scale factor for the length-related musculotendon parameters examined in this study. Longer musculotendon complexes exhibit relatively longer muscle bellies, which are in turn associated with shorter muscle fibre lengths. This trade-off between gastrocnemius muscle belly length and muscle fibre length might have the advantage that muscle volume stays constant regardless of the length of the limbs.
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Músculo Esquelético/anatomía & histología , Tendones/anatomía & histología , Animales , Perros , Músculo Esquelético/fisiología , Tendones/fisiologíaRESUMEN
Finite element (FE) simulations are increasingly valuable in assessing and improving the performance of biomedical devices and procedures. Due to high computational demands such simulations may become difficult or even infeasible, especially when considering nearly incompressible and anisotropic material models prevalent in analyses of soft tissues. Implementations of GPGPU-based explicit FEs predominantly cover isotropic materials, e.g. the neo-Hookean model. To elucidate the computational expense of anisotropic materials, we implement the Gasser-Ogden-Holzapfel dispersed, fiber-reinforced model and compare solution times against the neo-Hookean model. Implementations of GPGPU-based explicit FEs conventionally rely on single-point (under) integration. To elucidate the expense of full and selective-reduced integration (more reliable) we implement both and compare corresponding solution times against those generated using underintegration. To better understand the advancement of hardware, we compare results generated using representative Nvidia GPGPUs from three recent generations: Fermi (C2075), Kepler (K20c), and Maxwell (GTX980). We explore scaling by solving the same boundary value problem (an extension-inflation test on a segment of human aorta) with progressively larger FE meshes. Our results demonstrate substantial improvements in simulation speeds relative to two benchmark FE codes (up to 300[Formula: see text] while maintaining accuracy), and thus open many avenues to novel applications in biomechanics and medicine.
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Gráficos por Computador , Computadores , Análisis de Elementos Finitos , Adventicia/fisiología , Anisotropía , Aorta Abdominal/fisiología , Fenómenos Biomecánicos , Simulación por Computador , Humanos , Reproducibilidad de los ResultadosRESUMEN
Plantar pressure simulation driven by integrated 3D motion capture data, using both a finite element and a discrete element model, is compared for ten healthy and ten diabetic neuropathic subjects. The simulated peak pressure deviated on average between 16.7 and 34.2% from the measured peak pressure. The error in the position of the peak pressure was on average smaller than 4.2 cm. No method was more accurate than the other although statistical differences were found between them. Both techniques are thus complementary and useful tools to better understand the alteration of diabetic foot biomechanics during gait.
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Simulación por Computador , Diabetes Mellitus/fisiopatología , Análisis de Elementos Finitos , Pie/fisiopatología , Presión , Adulto , Fenómenos Biomecánicos , Estudios de Casos y Controles , Pie Diabético/fisiopatología , Humanos , Persona de Mediana Edad , Reproducibilidad de los ResultadosRESUMEN
Accurate estimation of peak wall stress (PWS) is the crux of biomechanically motivated rupture risk assessment for abdominal aortic aneurysms aimed to improve clinical outcomes. Such assessments often use the finite element (FE) method to obtain PWS, albeit at a high computational cost, motivating simplifications in material or element formulations. These simplifications, while useful, come at a cost of reliability and accuracy. We achieve research-standard accuracy and maintain clinically applicable speeds by using novel computational technologies. We present a solution using our custom finite element code based on graphics processing unit (GPU) technology that is able to account for added complexities involved with more physiologically relevant solutions, e.g. strong anisotropy and heterogeneity. We present solutions up to 17× faster relative to an established finite element code using state-of-the-art nonlinear, anisotropic and nearly-incompressible material descriptions. We show a realistic assessment of the explicit GPU FE approach by using complex problem geometry, biofidelic material law, double-precision floating point computation and full element integration. Due to the increased solution speed without loss of accuracy, shown on five clinical cases of abdominal aortic aneurysms, the method shows promise for clinical use in determining rupture risk of abdominal aortic aneurysms.
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Aneurisma de la Aorta Abdominal , Rotura de la Aorta , Análisis de Elementos Finitos , Humanos , Modelos Cardiovasculares , Reproducibilidad de los Resultados , Riesgo , Estrés MecánicoRESUMEN
BACKGROUND: Bones continually adapt their morphology to their load bearing function. At the level of the subchondral bone, the density distribution is highly correlated with the loading distribution of the joint. Therefore, subchondral bone density distribution can be used to study joint biomechanics non-invasively. In addition physiological and pathological joint loading is an important aspect of orthopaedic disease, and research focusing on joint biomechanics will benefit veterinary orthopaedics. This study was conducted to evaluate density distribution in the subchondral bone of the canine talus, as a parameter reflecting the long-term joint loading in the tarsocrural joint. RESULTS: Two main density maxima were found, one proximally on the medial trochlear ridge and one distally on the lateral trochlear ridge. All joints showed very similar density distribution patterns and no significant differences were found in the localisation of the density maxima between left and right limbs and between dogs. CONCLUSIONS: Based on the density distribution the lateral trochlear ridge is most likely subjected to highest loads within the tarsocrural joint. The joint loading distribution is very similar between dogs of the same breed. In addition, the joint loading distribution supports previous suggestions of the important role of biomechanics in the development of OC lesions in the tarsus. Important benefits of computed tomographic osteoabsorptiometry (CTOAM), i.e. the possibility of in vivo imaging and temporal evaluation, make this technique a valuable addition to the field of veterinary orthopaedic research.
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Densidad Ósea , Perros/anatomía & histología , Astrágalo , Tomografía Computarizada por Rayos X , Animales , Fenómenos Biomecánicos , Astrágalo/anatomía & histología , Astrágalo/diagnóstico por imagen , Articulaciones Tarsianas/anatomía & histología , Articulaciones Tarsianas/diagnóstico por imagenRESUMEN
Current clinical standards to assess sleep and its disorders lack either accuracy or user-friendliness. They are therefore difficult to use in cost-effective population-wide screening or long-term objective follow-up after diagnosis. In order to fill this gap, the use of cardiac and respiratory information was evaluated for discrimination between different sleep stages, and for detection of apneic breathing. Alternative probabilistic visual representations were also presented, referred to as the hypnocorrogram and apneacorrogram. Analysis was performed on the UCD sleep apnea database, available on Physionet. The presence of apneic events proved to have a significant impact on the performance of a cardiac and respiratory based algorithm for sleep stage classification. WAKE versus SLEEP discrimination resulted in a kappa value of κ = 0.0439, while REM versus NREM resulted in κ = 0.298 and light sleep (N1N2) versus deep sleep (N3) in κ = 0.339. The high proportion of hypopneic events led to poor detection of apneic breathing, resulting in a kappa value of κ = 0.272. While the probabilistic representations allow to put classifier output in perspective, further improvements would be necessary to make the classifier reliable for use on patients with sleep apnea.
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Corazón/fisiología , Corazón/fisiopatología , Polisomnografía , Respiración , Síndromes de la Apnea del Sueño/diagnóstico , Síndromes de la Apnea del Sueño/fisiopatología , Sueño , Adulto , Anciano , Femenino , Humanos , Aprendizaje Automático , Masculino , Persona de Mediana Edad , Probabilidad , Procesamiento de Señales Asistido por Computador , Fases del SueñoRESUMEN
The mechanical properties of human biological tissue vary greatly. The determination of arterial material properties should be based on experimental data, i.e. diameter, length, intramural pressure, axial force and stress-free geometry. Currently, clinical data provide only non-invasively measured pressure-diameter data for superficial arteries (e.g. common carotid and femoral artery). The lack of information forces us to take into account certain assumptions regarding the in situ configuration to estimate material properties in vivo. This paper proposes a new, non-invasive, energy-based approach for arterial material property estimation. This approach is compared with an approach proposed in the literature. For this purpose, a simplified finite element model of an artery was used as a mock experimental situation. This method enables exact knowledge of the actual material properties, thereby allowing a quantitative evaluation of material property estimation approaches. The results show that imposing conditions on strain energy can provide a good estimation of the material properties from the non-invasively measured pressure and diameter data.
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Arterias/fisiología , Presión Sanguínea/fisiología , Transferencia de Energía/fisiología , Modelos Cardiovasculares , Resistencia Vascular/fisiología , Rigidez Vascular/fisiología , Animales , Anisotropía , Simulación por Computador , Módulo de Elasticidad/fisiología , Humanos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Estrés MecánicoRESUMEN
In vitro gait simulations are a preferential platform to study new intervention techniques or surgical procedures as they allow studying the isolated effect of surgical interventions. Commonly, simulations are performed by applying pre-defined setpoints for the kinetics and kinematics on all degrees of freedom (DOFs) of the cadaveric specimen. This however limits the applicability of the experiment to simulations for which pre-defined kinematics and kinetics can be measured in vivo. In this study we introduce inertial control as a new methodology for gait simulations that omits the need for pre-defined setpoints for the externally applied vertical ground reaction force (vGRF) and therefore allows the effect of interventions to be reflected upon it. Gait simulations of stance (1 s) were performed in 10 cadaveric specimens under three clinically relevant conditions: native ankle, total ankle prosthesis (TAP) and total ankle prosthesis plus triple arthrodesis (TAP+TA). In the native ankle, simulated vGRF was compared against the vGRF measured in vivo in 15 healthy volunteers and high correlations were found (R(2)=0.956, slope of regression line S=1.004). In TAP and TAP+TA, vGRF changed, therefore confirming the sensitivity of the method to kinematic constrains imposed with surgery. Inertial control can replicate in vivo kinetic conditions and allows investigating the isolated effect of surgical interventions on kinematic as well as kinetics.
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Marcha/fisiología , Modelos Biológicos , Articulación del Tobillo/fisiología , Articulación del Tobillo/cirugía , Artrodesis , Artroplastia de Reemplazo de Tobillo , Fenómenos Biomecánicos , Pie/fisiología , Humanos , Cinética , MovimientoRESUMEN
The typical bone density patterns in the proximal femur can be explained using bone remodeling simulations incorporating a load-adaptive response. Yet, subject-specific variations in bone density have not received much attention. Therefore, the objective of this study was to quantify to what extent subject-specific bone geometry and subject-specific musculoskeletal loading affect the predicted bone density distribution. To accomplish this goal, a computational bone remodeling scheme was combined with gait analysis and a subject-specific musculoskeletal model. Finite element models incorporating the subject-specific geometry as well as the subject-specific hip contact forces and associated muscle forces were used to predict the density distribution in the proximal femur of three individuals. Next, the subject-specific musculoskeletal loads were interchanged between the subjects and the resulting changes in bone remodeling of the proximal femur were analyzed. Simulations results were compared to computed tomography (CT) image-based density profiles. The results confirm that the predicted bone density distribution in the proximal femur is drastically influenced by the inclusion of subject-specific loading, i.e. hip contact forces and muscle forces calculated based on gait analysis data and musculoskeletal modeling. This factor dominated the effect of individualized geometry. We conclude that when predicting femoral density distribution in patients, the effect of subject-specific differences in loading conditions of the hip joint and the associated difference in muscle forces needs to be accounted for.
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Densidad Ósea , Fémur/fisiología , Soporte de Peso , Adulto , Remodelación Ósea , Femenino , Análisis de Elementos Finitos , Humanos , Masculino , Persona de Mediana Edad , Modelos BiológicosRESUMEN
Orthodontic tooth movement is achieved by the process of repeated alveolar bone resorption on the pressure side and new bone formation on the tension side. In order to optimize orthodontic treatment, it is important to identify and study the biological processes involved. This article presents a mechanobiological model using partial differential equations to describe cell densities, growth factor concentrations, and matrix densities occurring during orthodontic tooth movement. We hypothesize that such a model can predict tooth movement based on the mechanobiological activity of cells in the PDL. The developed model consists of nine coupled non-linear partial differential equations, and two distinct signaling pathways were modeled: the RANKL-RANK-OPG pathway regulating the communication between osteoblasts and osteoclasts and the TGF-ß pathway mediating the differentiation of mesenchymal stem cells into osteoblasts. The predicted concentrations and densities were qualitatively validated by comparing the results to experiments reported in the literature. In the current form, the model supports our hypothesis, as it is capable of conceptually simulating important features of the biological interactions in the alveolar bone-PDL complex during orthodontic tooth movement.
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Modelos Biológicos , Ortodoncia , Técnicas de Movimiento Dental , Simulación por Computador , Humanos , Osteoblastos/citología , Osteoblastos/metabolismo , Osteogénesis/fisiología , Osteoprotegerina/metabolismo , Ligando RANK/metabolismo , Reproducibilidad de los Resultados , Transducción de Señal , Factor de Crecimiento Transformador beta/metabolismo , Soporte de PesoRESUMEN
Progress in medicine and higher expectation of quality of life has led to a higher demand for several dental and medical treatments. This increases the occurrence of situations in which orthodontic treatment is complicated by pathological conditions, medical therapies and drugs. Together with experiments, computer models might lead to a better understanding of the effect of pathologies and medical treatment on tooth movement. This study uses a previously presented mechanobiological model of orthodontic tooth displacement to investigate the effect of pathologies and (medical) therapies on the result of orthodontic treatment by means of three clinically relevant case studies looking at the effect of estrogen deficiency, the effect of OPG injections and the influence of fluoride intake. When less estrogen was available, the model predicted bone loss and a rise in the number of osteoclasts present at the compression side, and a faster bone resorption. These effects were also observed experimentally. Experiments disagreed on the effect of estrogen deficiency on bone formation, while the mechanobiological model predicted very little difference between the pathological and the non-pathological case at formation sites. The model predicted a decrease in tooth movement after OPG injections or fluoride intake, which was also observed in experiments. Although more experiments and model analysis is needed to quantitatively validate the mechanobiological model used in this study, its ability to conceptually describe several pathological conditions is an important measure for its validity.
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Resorción Ósea/fisiopatología , Simulación por Computador , Modelos Biológicos , Osteogénesis , Técnicas de Movimiento Dental , Animales , Resorción Ósea/patología , HumanosRESUMEN
Proper body support plays an import role in the recuperation of our body during sleep. Therefore, this study uses an automatically adapting bedding system that optimises spinal alignment throughout the night by altering the stiffness of eight comfort zones. The aim is to investigate the influence of such a dynamic sleep environment on objective and subjective sleep parameters. The bedding system contains 165 sensors that measure mattress indentation. It also includes eight actuators that control the comfort zones. Based on the measured mattress indentation, body movements and posture changes are detected. Control of spinal alignment is established by fitting personalized human models in the measured indentation. A total of 11 normal sleepers participated in this study. Sleep experiments were performed in a sleep laboratory where subjects slept three nights: a first night for adaptation, a reference night and an active support night (in counterbalanced order). Polysomnographic measurements were recorded during the nights, combined with questionnaires aiming at assessing subjective information. Subjective information on sleep quality, daytime quality and perceived number of awakenings shows significant improvements during the active support (ACS) night. Objective results showed a trend towards increased slow wave sleep. On the other hand, it was noticed that % N1-sleep was significantly increased during ACS night, while % N2-sleep was significantly decreased. No prolonged N1 periods were found during or immediately after steering.
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Ropa de Cama y Ropa Blanca , Diseño de Equipo , Sueño , Adaptación Fisiológica , Adulto , Bélgica , Femenino , Humanos , Masculino , Movimiento/fisiología , Polisomnografía , Postura/fisiología , Encuestas y CuestionariosRESUMEN
In morphological analysis of the femur, the hip joint centre (HJC) is generally determined using a 3D model of the femoral head based on medical images. However, the portion of the image selected to represent the femoral head may influence the HJC. We determined if this influence invalidates the results of three HJC calculation methods, one of which we introduce here. To isolate femoral heads in cadaver CT images, thresholds were applied to the distance between femur and acetabulum models. The sensitivity of the HJC to these thresholds and the differences between methods were quantified. For thresholds between 6 and 9 mm and healthy hips, differences between methods were below 1 mm and all methods were insensitive to threshold changes. For higher thresholds, the fovea capitis femoris disturbed the HJC. In two deformed hips, the new method performed superiorly. We conclude that for normal hips all methods produce valid results.