Dissertationen zum Thema „Spindle stiffness“

Les divisions méiotiques sont très asymétriques en taille et génèrent une très grosse cellule, l'ovocyte, et deux petites cellules, les globules polaires. Cette asymétrie est permise par la migration du fuseau lors de la première division jusqu'au cortex le plus proche. Cette migration ne dépend pas des microbutules mais de la Myosin-II et d'un réseau de filaments d'actine nucléé par la coopération des nucléateurs de filaments droits Formin-2 et Spire1/2. Des observations préliminaires effectuées au laboratoire ont décrit un épaississement du cortex d'actine pendant la migration du fuseau, mais pourtant il avait été montré que la tension corticale, un paramètre décrivant la rigidité de l'ovocyte, diminue pendant la migration du fuseau. J'ai montré que cet épaississement est indispensable à la migration du fuseau et est nucléé par le nucléateur de filaments branchés Arp2/3, sous le contrôle de la voie Mos/MAPK. De plus, il provoque la diminution de la tension corticale en délocalisant la Myosin-II, ce qui est indispensable à la migration du fuseau. Finalement, j'ai montré que le chute de tension est un mécanisme d'amplification du déséquilibre des forces présent initialement (grâce au léger décentrage du noyau) qui déclenche la migration du fuseau
Meiotic divisions are highly asymmetric divisions in size, generating a big cell, the oocyte, and two tiny cells, the polar bodies. This asymmetry is ensured by the migration of the first meiotic spindle to the closest cortex. This migration does not depend on microtubules but on Myosin-II and an F-actin meshwork nucleated by cooperation of straight filament nucleators Formin-2 and Spire1/2. Preliminary studies in the lab described a thickening of the F-actin cortex during spindle migration, but paradoxically cortical tension, a physical parameter describing the stiffness of the cell, drops during spindle migration. I have shown that this thickening is required for spindle migration and nucleated by the branched actin nucleator Arp2/3, under the control of the Mos/MAPK pathway. Furthermore, it promotes the decrease in cortical tension by triggering the delocalization of Myosin-II from the oocyte cortex, which is crucial for spindle migration. Finally, I have shown that the drop in cortical tension is an amplificatory mechanism to the initial unbalance of forces (due to a slight off-centered position of the nucleus) triggering the motion of the spindle

The thesis deals with the design and construction of headstocks of a turning centre. The aim is to design a spindle with an output of 20 kW and a maximum speed of 5000 1/min. The research part of the thesis is focused on the description of the basic parameters of the headstock and turning centres needed for the construction of the headstock and contains an analysis of the available spindles on the market. The next part of the thesis deals with the selection and calculation of cutting conditions and the necessary parameters. Analytical calculations are then verified using FEM analysis. At the end of the thesis, a 3D model was developed and headstock drawing documentation.

Machine tools need to be tested to check they behave correctly while machining. A bigger production (capacity), improving the accuracy in final products (quality) or reducing costs are some of the main goals. Reducing the maintenance of the machines, their nonproductive time and a higher quality of the final parts, have a strong influence in the costs. Even machines built to the same specification present different properties and behaviours, which leads into a reduction of the flexibility when it comes to move operations among them. This study is focused on the measurement and modelling of four machine tools (M1, M2, M3 and M4), with same specifications, from the static point of view. Methods used to measure all these properties are the circular tests under loaded conditions, with the device Loaded Double Ball Bar (LDBB), which measures positional accuracy and static stiffness. Different pressures (0.5, 1, 3, 5, 6, 7 bar) and locations for the LDBB have been used.   After the tests were performed, all the machines shown good properties with the detail of M4, which had a lower stiffness than the other three ones due to its table attachments.
Maskinverktyg måste testas för att kontrollera att de beter sig korrekt vid bearbetning. En större produktion (kapacitet), förbättra noggrannheten i slutprodukterna (kvalitet) eller sänka kostnaderna är några av huvudmålen. Att minska underhållet av maskinerna, deras icke-produktiva tid och en högre kvalitet på de slutliga delarna har ett starkt inflytande i kostnaderna. Även maskiner konstruerade för samma specifikation presenterar olika egenskaper och beteenden, vilket leder till en minskning av flexibiliteten när det gäller att flytta verksamheten bland dem. Denna studie är inriktad på mätning och modellering av fyra verktygsmaskiner (M1, M2, M3 och M4), med samma specifikationer, ur statisk synvinkel. Metoder som används för att mäta alla dessa egenskaper är de cirkulära testerna under laddade förhållanden, med enheten Loaded Double Ball Bar (LDBB), som mäter positionsnoggrannhet och statisk styvhet. Olika tryck (0,5, 1, 3, 5, 6, 7 bar) och platser för LDBB har använts.   Efter testerna visade alla maskiner goda egenskaper med detaljerna i M4, som hade en lägre styvhet än de andra tre på grund av dess bordsfästanordningar.

There is a need for spinal implants that have nonlinear stiffness to provide stabilization if the spine loses stiffness through injury, degeneration, or surgery. There is also a need for spinal implants to be customizable for individual needs, and to be small enough to be unobtrusive once implanted. Past and ongoing work that defines the effects of degeneration on the torque rotation curve of a functional spinal unit (FSU) were used to produce a spinal implant which could meet these requirements. This thesis proposes contact-aided inserts to be used with the FlexSuRe™ spinal implant to create a nonlinear stiffness. Moreover, different inserts can be used to create customized behaviors. An analytical model is introduced for insert design, and the model is verified using a finite element model and tests of physical prototypes both on a tensile tester and cadaveric testing on an in-house spine tester. Testing showed the inserts are capable of creating a non-linear force-deflection curve and it was observed that the device provided increased stiffness to a spinal segment in flexion-extension and lateral-bending. This thesis further proposes that the FlexSuRe™ spinal implant can be reduced in size by joining LET joint geometries in series in a serpentine nature. An optimization procedure was performed on the new geometry and feasible designs were identified. Moreover, due to maintaining LET joint geometry, the contact-aided insert could be implemented in conjunction with this new device geometry.

The contributions of stretch reflexes to overall joint stiffness are unknown in normal and pathological function. The main reason for this is difficulty in distinguishing the mechanical contributions of the two mechanisms. We used a new non-linear system identification technique to achieve this and address three specific objectives.
First, we identified intrinsic and reflex contributions to dynamic ankle stiffness over a wide range of tonic voluntary contraction levels and ankle positions in healthy human subjects (normals). Intrinsic and reflex dynamic stiffness were strongly modulated with operating points; reflex mechanisms made their largest relative contribution to ankle stiffness at low levels of contraction and near the mid-positions. In some cases, reflexes contributed significantly to overall torque indicating that stretch reflexes have a potential to play a significant role in control of posture and movement.
Second, we examined the nature and origin of mechanical abnormalities associated with spasticity in chronic spinal cord injured subjects (SCIs). Reflex and intrinsic stiffness were larger in SCIs than normals. The magnitude and relative size of the changes were strongly dependent on joint position and contraction state. Overall joint stiffness was abnormally and significantly high in SCIs and stretch reflexes contributed strongly to it.
Third, we explored the effects of long-term FES-assisted walking on intrinsic and reflex dynamic stiffness in SCIs. Both reflex and intrinsic stiffness decreased substantially following long-term (>16 months) FES-assisted walking. The results indicate that this rehabilitation approach may cause spastic joint mechanics to become closer to normal behavior, and consequently could be useful for treatment as well as restoring function.

Spinal stability describes the ability of the neuromuscular system to maintain equilibrium in the presence of kinematic and control variability, and may play an important role in the etiology of low-back disorders (LBDs). The primary mechanism for the neuromuscular control of spinal stability is the recruitment and control of active paraspinal muscle stiffness (i.e., trunk stiffness). The two major components of active muscle stiffness include the immediate stiffness contribution provided by the intrinsic stiffness of actively contracted muscles, and the delayed stiffness contribution provided by the reflex response. The combined behavior of these two components of active muscle stiffness is often referred to as "effective stiffness". In order to understand the neuromuscular control of spinal stability, stochastic system identification methods were utilized and nonparametric impulse response functions (IRFs) calculated in three separate studies in an effort to: 1) Quantify the effective dynamics (stiffness, damping, mass) of the trunk Nonparametric IRFs were implemented to estimate the dynamics of the trunk during active voluntary trunk extension exertions. IRFs were determined from the movement following pseudo-random stochastic force disturbances applied to the trunk. Results demonstrated a significant increase in effective stiffness and damping with voluntary exertion forces. 2) Quantify the reflex dynamics of the trunk Nonparametric IRFs were computed from the muscle electromyographic (EMG) reflex response following a similar pseudo-random force disturbance protocol. Reflexes were observed with a mean response delay of 67 msec. Reflex gain was estimated from the peak of the IRF and increased significantly with exertion effort. 3) Separate the intrinsic and reflexive components of the effective dynamics and determine the relative role of each in the control of spinal stability. Both intrinsic muscle and reflexive components of activation contribute to the effective trunk stiffness. To evaluate the relative role of these components, a nonlinear parallel-cascade system identification procedure was used to separate the intrinsic and reflexive dynamics. Results revealed that the intrinsic dynamics of the trunk alone can be insufficient to counteract the destabilizing effects of gravity. This illustrates the extreme importance of reflexive feedback in the maintenance of spinal stability and warrants the inclusion of reflexes in any comprehensive trunk model.
Ph. D.

Few studies have investigated the neuromuscular recruitment and stabilizing control of the spine during pushing and pulling exertions. Past theoretical investigation suggest that co-contraction of the of the paraspinal muscles is necessary to stabilize the spine during pushing exertions. We hypothesized greater levels of co-contraction during pushing exertions. Co-contraction of trunk musculature was quantified during isometric pushing and pulling tasks. The mean value of co-contraction during pushing was two-fold greater (p < 0.01) than during extension. Co-contraction has been shown to increase the stiffness of the ankle but this effect has not been demonstrated in the trunk. Trunk stiffness was measured as a function of co-activation during extension exertions. Results demonstrate trunk stiffness was significantly (p < 0.01) greater with co-activation. Trunk stiffness was calculated during isometric pushing and pulling exertions. We hypothesized trunk stiffness would be greater during pushing tasks due to increased levels of co-contraction to maintain stability of the spine. Results demonstrate trunk stiffness was significantly (p < 0.05) greater during pushing compared to pulling exertions. Results suggest that trunk isometric pushing tasks require more co-contraction than pulling tasks enable to maintain spinal stability. Greater levels of co-contraction during pushing exertions caused trunk stiffness to be greater during pushing compared to pulling tasks. Results may indicate greater risk of spinal instability from motor control error during pushing tasks than pulling exertions. Future studies need to consider co-contraction and neuromuscular control of spinal stability when evaluating the biomechanical risks of pushing and pulling tasks.
Master of Science

La scoliose infantile est une déformation rachidienne évolutive survenant chez l'enfant de moins de 3 ans. La technique de correction la plus répandue actuellement est celle des « tiges de croissance ». Cependant, la rigidité du matériel provoque la dégénérescence des disques intervertébraux, ce qui di-minue l'efficacité du traitement. Des études récentes ont montré l'effet bénéfique d'implants flexibles sur les disques. Notre équipe a donc développé le concept d'une suspension implantable qui permet de garder la mobilité axiale des segments instrumentés, associé à un nouveau système de fixation rotulée. Cepen-dant, quelle valeur de raideur permet de préserver les disques tout en corrigeant efficacement la sco-liose ? Cette thèse a donc pour objectifs de démontrer l'intérêt d'une suspension pour les disques inter-vertébraux et d'obtenir des informations quantifiables sur la valeur optimale de raideur. Pour cela des prototypes de suspension avec fixation rotulée, implantables chez le mammifère quadrupède et l'Homme, ont été développés afin d'étudier in vivo et in silico plusieurs gammes de flexibilité. Une étude in vivo sur chèvres adultes saines a été menée pour tester ces prototypes pour 2 raideurs différentes. L'état des disques intervertébraux après 6 mois a été évalué par IRM et par coupes histologiques. En parallèle la biomécanique d'un rachis humain sain puis scoliotique, instrumenté avec différents disposi-tifs (tiges classiques, suspensions, avec ou sans rotules), a été étudiée avec un modèle numérique mul-ti-corps rigides, préalablement validé par comparaison avec des données in vitro de la littérature. Les résultats de l'étude in vivo n'ont pas montré de différence significative entre les différentes instrumentations testées. Un temps d'essai plus long semble nécessaire pour voir apparaître la dégéné-rescence discale. Les simulations numériques ont montré une nette amélioration de la mobilité des segments ins-trumentés avec une suspension rotulée. La majorité de la mobilité est cependant assuré par le nouveau système de fixation et non par la présence d'une plus grande souplesse axiale. La suspension permet néanmoins un gain supplémentaire pour certains mouvements du rachis. Aucune différence significative n'a été constatée entre les 2 valeurs de raideurs étudiées. La présence de fixations rotulée diminue par contre fortement la correction obtenue lors des simulations de chirurgie de distraction. La suspension seule présente un intérêt certain lors de la correc-tion en diminuant les efforts transmis au matériel. Les développements futurs s'orienteraient donc vers une suspension combinée à des fixations rotulées présentant également des raideurs en rotation pour conserver correction et mobilité
Infantile scoliosis is a progressive spinal deformity occurring in children under 3 years-old. The most common currently correction technic is the "growing rods" one. However, the implant rigidity causes intervertebral discs degeneration, which decreases the treatment efficiency. Recent studies have shown the benefic effect of flexible implants on discs. Our team has developed the concept of an implantable suspension that keeps the axial mobility of the instrumented segments, associated with a new fastening ball joint system. However, which is the stiffness value that preserves discs while correcting scoliosis? This thesis goal is to demonstrate the effectiveness of a suspension device for preserving inter-vertebral discs health and obtain quantifiable information on the optimum stiffness value. Prototype suspensions with ball joint fastenings, implantable in quadruped mammals and humans, have been de-veloped to study several ranges of stiffness values in vivo and in silico. An in vivo study on healthy adult goats was conducted to test these prototypes for two different stiffness values. The intervertebral discs health after 6 months was evaluated by MRI and histological sections. In parallel the biomechanics of a human spine was studied with a rigid multi-body numerical model previously validated against in vitro literature data. Healthy and scoliosis subjects instrumented with different devices (traditional rods, sus-pensions, with or without the ball) were modeled. The results of the in vivo study showed no significant difference between the several instrumen-tations. A longer test time seems necessary to observe the onset of disc degeneration. Numerical simulations have shown a marked mobility improvement for the segments in the in-strumented area with a suspension device associated with a ball joint system. However, the majority of the mobility is provided by the new fixing system and not by a greater axial flexibility. The suspension still allows additional gain for certain spine movements. No significant differences were found between the two studied stiffness values. The presence of a ball joint fastening decreases strongly the correction obtained during surgery distraction simulations. The suspension has an interest during correction by reducing the forces trans-mitted to the material when used alone. Future developments thus would lead to a suspension device associated with ball joint fasten-ings that also have rotational stiffness to keep both good scoliosis correction and segments mobility

More than 50% of intervertebral discs in the third and fourth decade of life exhibit annular tears and fissures with different orientations and extents. On the other hand, in vitro biomechanical investigations of the disc surgery treatment, sometimes requires collaterals lesions, such as incision or disc material removal to recreate biological injuries, as in discoplastly. These lesions could have a mechanical impact on the spine flexibility and in the surrounding tissue and could alter the final outcomes of in vitro studies. The influence of the presence of lesions on the biomechanics of the segment is still a debated research question. Thus, this in vitro study aims to evaluate changes in spine biomechanics, in terms of stiffness, range of motion and disc height, induced by an increasing damage of human disc. In order to assess the impact of the annulus damage on the surrounding tissues, principal strain distributions were investigated in the lateral side opposite than the damaged region. Eight fresh cadaver thoraco-lumbar FSUs were used in this study. The specimens were tested sequentially in flexion and extension in five different configurations: a) with the intact disc; b) with two vertical cuts; c) with four cuts, forming a square, without removing any part of the annulus; d) after having removed the cut part of the AF; e) after having removed the nucleus pulposus. Image analysis and surface strain distribution were performed on the lateral disc by means of the Digital Image Correlation.

Orientador: Tamotsu Hirata
Banca: José Elias Tomazini
Banca: José Geraldo Trani Brandão
Banca: Rubens Corrêa Araújo
Banca: Mauro Gonçalves
Resumo: A mobilização póstero-anterior consiste numa técnica de terapia manual que tem a finalidade de detectar alterações no padrão normal e na amplitude dos movimentos das articulações intervertebrais em pacientes com lombalgia. Mecanicamente, define-se como uma sobrecarga de inclinação de três pontos e, embora, o procedimento de aplicação desta técnica tenha sido descrito, caracteriza-se por um método subjetivo de análise clínica. No sentido de buscar um melhor esclarecimento acerca dos aspectos mecânicos envolvidos na mobilização póstero-anterior, foi desenvolvido um dispositivo eletromecânico, para análise in vivo da rigidez segmentar póstero-anterior da coluna lombar. Tal aparato compõe-se essencialmente de um suporte de sustentação com dois graus de liberdade (x, y) integrado a um motoredutor de corrente contínua acoplado a um pino guia e fixo a uma maca especialmente adaptada. Permite o controle preciso da intensidade, direção e velocidade da força aplicada, além da mensuração da amplitude do deslocamento intervertebral. Os resultados demonstraram que o instrumento desenvolvido apresenta a possibilidade de uma análise quantitativa acurada, em termos de rigidez segmentar na coluna lombar, indicando um grau de confiabilidade significativo para os dados obtidos em testes de repetibilidade (ICC > 0,80). Foi demonstrado haver diferença estatisticamente significativa (p<0,05) entre os valores médios dos graus de rigidez dos níveis vertebrais analisados (LI, LII, LIII, LIV e LV) em 10 sujeitos avaliados. Deste modo, é importante que seja questionado o conceito da comparação do grau de rigidez entre os diferentes níveis vertebrais, num mesmo sujeito, para critério de diagnóstico.
Abstract: The posteroanterior motion test consists of a manual therapy technique to assess the range of motion and stiffness parameters of intervertebral joints in subjects with low back pain. Mechanically, it is defined as a three point bending loading. Although, has been described the technique procedure of the posteroanterior motion test, it is characterized by a subjective method of clinical analysis. In the quest to better understand concerning the mechanical aspects of posteroanterior motion test was developed a mechanical device for assessment the response of the lumbar spine to a posteroanterior pressure in vivo. Essentially, such apparatus is composed of a sustentation support with two degrees of freedom (x, y) fixed to a couch especially adapted and integrated to a continuous current motor and a guidance pin. It allows variables such as force, frequency of oscillation and displacement to be precisely controlled. The results demonstrated high reliability (ICC > 0,80) of the measures obtained in test and re-test. So, the instrument developed presents the prospect of an accuracy quantitative analysis of intervertebral posteroanterior stiffness in lumbar spine. There was statistically significant difference (p<0,05) amongst the means of stiffness coefficients of the vertebral levels analyzed (LI, LII, LIII, LIV and LV) in 10 subjects evaluated. Therefore, its is important to be questioned the concept of the comparison of stiffness in different vertebral levels in a same subject for diagnosis criterion.
Doutor

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
A mobilização póstero-anterior consiste numa técnica de terapia manual que tem a finalidade de detectar alterações no padrão normal e na amplitude dos movimentos das articulações intervertebrais em pacientes com lombalgia. Mecanicamente, define-se como uma sobrecarga de inclinação de três pontos e, embora, o procedimento de aplicação desta técnica tenha sido descrito, caracteriza-se por um método subjetivo de análise clínica. No sentido de buscar um melhor esclarecimento acerca dos aspectos mecânicos envolvidos na mobilização póstero-anterior, foi desenvolvido um dispositivo eletromecânico, para análise in vivo da rigidez segmentar póstero-anterior da coluna lombar. Tal aparato compõe-se essencialmente de um suporte de sustentação com dois graus de liberdade (x, y) integrado a um motoredutor de corrente contínua acoplado a um pino guia e fixo a uma maca especialmente adaptada. Permite o controle preciso da intensidade, direção e velocidade da força aplicada, além da mensuração da amplitude do deslocamento intervertebral. Os resultados demonstraram que o instrumento desenvolvido apresenta a possibilidade de uma análise quantitativa acurada, em termos de rigidez segmentar na coluna lombar, indicando um grau de confiabilidade significativo para os dados obtidos em testes de repetibilidade (ICC > 0,80). Foi demonstrado haver diferença estatisticamente significativa (p<0,05) entre os valores médios dos graus de rigidez dos níveis vertebrais analisados (LI, LII, LIII, LIV e LV) em 10 sujeitos avaliados. Deste modo, é importante que seja questionado o conceito da comparação do grau de rigidez entre os diferentes níveis vertebrais, num mesmo sujeito, para critério de diagnóstico.
The posteroanterior motion test consists of a manual therapy technique to assess the range of motion and stiffness parameters of intervertebral joints in subjects with low back pain. Mechanically, it is defined as a three point bending loading. Although, has been described the technique procedure of the posteroanterior motion test, it is characterized by a subjective method of clinical analysis. In the quest to better understand concerning the mechanical aspects of posteroanterior motion test was developed a mechanical device for assessment the response of the lumbar spine to a posteroanterior pressure in vivo. Essentially, such apparatus is composed of a sustentation support with two degrees of freedom (x, y) fixed to a couch especially adapted and integrated to a continuous current motor and a guidance pin. It allows variables such as force, frequency of oscillation and displacement to be precisely controlled. The results demonstrated high reliability (ICC > 0,80) of the measures obtained in test and re-test. So, the instrument developed presents the prospect of an accuracy quantitative analysis of intervertebral posteroanterior stiffness in lumbar spine. There was statistically significant difference (p<0,05) amongst the means of stiffness coefficients of the vertebral levels analyzed (LI, LII, LIII, LIV and LV) in 10 subjects evaluated. Therefore, its is important to be questioned the concept of the comparison of stiffness in different vertebral levels in a same subject for diagnosis criterion.

Biomechanical testing of cadaveric spinal segments forms the basis for our current understanding of healthy, pathological, and surgically treated spinal function. Over the past 40 years there has been a substantial amount of data published based on a spinal biomechanical testing regimen known as the flexibility method. This data has provided valuable clinical insights that have shaped our understanding of low back pain and its treatments. Virtually all previous lumbar spinal flexibility testing has been performed at room temperature, under very low motion rates, without the presence of a compressive follower-load to simulate upper body weight and the action of the musculature. These limitations of previous work hamper the applicability of published spinal biomechanics data, especially as researchers investigate novel ways of treating low back pain that are intended to restore the spine to a healthy biomechanical state. Thus, the purpose of this thesis work was to accurately characterize the rate-dependent flexibility of the lumbar spine at body temperature while in the presence of a compressive follower-load. A custom spine simulator with an integrated environmental chamber was developed and built as part of this thesis work. Cadaveric spinal motion segments were tested at 12 different rates of loading spanning the range of voluntary motion rates. The testing methodology allowed for comparison of spinal flexibility at room and body temperatures in the three primary modes of spinal motion, both with and without a compressive follower-load. Additionally, the work developed a stochastic model for rate-dependent spinal flexibility that allows for accurate prediction of spinal flexibility at any rate within the range of voluntary motion, based on a single flexibility test. In conclusion, the biomechanical response was significantly altered due to testing temperature, loading-rate, and application of a compressive follower-load. The author emphasizes the necessity to simulate the physiological environment during ex vivo biomechanical analysis of the lumbar spine in order to obtain a physiological response. Simplified testing procedures may be implemented only after the particular effect is known.

Orientador: Tamotsu Hirata
Banca: José Elias Tomazini
Banca: Luiz Fernando Costa Nascimento
Resumo: Um modelo fundamentado nos sistemas multicorpos, com sete corpos rígidos e oito corpos flexíveis, com três graus de liberdade para cada um dos corpos rígidos está sendo proposto. Os corpos rígidos são providos de inércia e os corpos flexíveis trabalham como juntas e não são providos de inércia. A solução numérica do modelo foi obtida com o método Runge-Kutta. Os parâmetros de influência, curvatura inicial da espinha lombar, posições dos centros geométricos das vértebras, tórax e da sacrum-pélvis, e o ponto de aplicação da força póstero-anterior (PA), foram obtidos de radiografia digital de cada paciente. O modelo foi simulado com dados de literaturas (obtidos de experimentos in vivo e em peças anatômicas). Os resultados foram satisfatórios do ponto de vista dos terapeutas e apresentam-se em conformidade com outros modelos propostos. O modelo oferece vantagem na aplicação individualizada a cada paciente pelos terapeutas, e foi construído com a metodologia de análise das forças aplicadas e suas reações diferentemente de outros modelos que apoiam-se nos métodos de análise das energias. O objetivo principal deste trabalho será o de avaliar o comportamento dinâmico do segmento lombar da coluna vertebral humana incluindo as massas do tórax e da pelve, por um modelo não-linear da rigidez viscoelástica estabelecido a partir da relação força-deslocamento obtida por experimentação in vivo.
Abstract: Evaluate a dynamic behavior of the human lumbar spine, with non-linear viscoelastic stiffness model followed by experimental data. Many of the techniques for the clinical treatment of dysfunction acting on lumber segments of the human spine have been based in the application of a postero anterior forces. Existing models to predict the state of lumber segments are restricted to evaluate general characteristic, furthermore, they use unrealistic boundary condition for its analysis. Periodic oscillatory posteroanterior forces were applied on each vertebra with initial lordotic curvature of the lumbar spine. A model is based on the multibody system of seven rigid bodies and eight deformable bodies representing human spine composed of thoratic, lumber and sacrum-pelvis segments. On each lumber were considered three degree of freedom(posterior - anterior, axial and flexion - extension). The rigid bodies are provided with inerti and the deformable bodies, wich would as joints with no inertia provided. Numerical solution of proposed model was solved with Ringe-Kutta methods. Parameter of influence, initial lordotic curvature, positions of the geometric centers of the vertebras, thorax and of the sacrum-pelvis, and point of application of the posteroanterior force (PA) were evaluated from x-ray image of patients. Nonlinear stiffness character introducedin the model affects the motion stability when periodic posteroanterior forces are applied to one vertebra.
Doutor

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Um modelo fundamentado nos sistemas multicorpos, com sete corpos rígidos e oito corpos flexíveis, com três graus de liberdade para cada um dos corpos rígidos está sendo proposto. Os corpos rígidos são providos de inércia e os corpos flexíveis trabalham como juntas e não são providos de inércia. A solução numérica do modelo foi obtida com o método Runge-Kutta. Os parâmetros de influência, curvatura inicial da espinha lombar, posições dos centros geométricos das vértebras, tórax e da sacrum-pélvis, e o ponto de aplicação da força póstero-anterior (PA), foram obtidos de radiografia digital de cada paciente. O modelo foi simulado com dados de literaturas (obtidos de experimentos in vivo e em peças anatômicas). Os resultados foram satisfatórios do ponto de vista dos terapeutas e apresentam-se em conformidade com outros modelos propostos. O modelo oferece vantagem na aplicação individualizada a cada paciente pelos terapeutas, e foi construído com a metodologia de análise das forças aplicadas e suas reações diferentemente de outros modelos que apoiam-se nos métodos de análise das energias. O objetivo principal deste trabalho será o de avaliar o comportamento dinâmico do segmento lombar da coluna vertebral humana incluindo as massas do tórax e da pelve, por um modelo não-linear da rigidez viscoelástica estabelecido a partir da relação força-deslocamento obtida por experimentação in vivo.
Evaluate a dynamic behavior of the human lumbar spine, with non-linear viscoelastic stiffness model followed by experimental data. Many of the techniques for the clinical treatment of dysfunction acting on lumber segments of the human spine have been based in the application of a postero anterior forces. Existing models to predict the state of lumber segments are restricted to evaluate general characteristic, furthermore, they use unrealistic boundary condition for its analysis. Periodic oscillatory posteroanterior forces were applied on each vertebra with initial lordotic curvature of the lumbar spine. A model is based on the multibody system of seven rigid bodies and eight deformable bodies representing human spine composed of thoratic, lumber and sacrum-pelvis segments. On each lumber were considered three degree of freedom(posterior - anterior, axial and flexion - extension). The rigid bodies are provided with inerti and the deformable bodies, wich would as joints with no inertia provided. Numerical solution of proposed model was solved with Ringe-Kutta methods. Parameter of influence, initial lordotic curvature, positions of the geometric centers of the vertebras, thorax and of the sacrum-pelvis, and point of application of the posteroanterior force (PA) were evaluated from x-ray image of patients. Nonlinear stiffness character introducedin the model affects the motion stability when periodic posteroanterior forces are applied to one vertebra.

碩士
國立虎尾科技大學
機械與電腦輔助工程系碩士班
102
As industries take off rapidly and the product demand amounts growing up continuously, most of the related parts and components in a product rely on machine-tool equipment to produce eagerly. In response to global competition, the machining and manufacturing should all be fast, effective and efficient, thus the needs of machine tools are augmented naturally day by day. A high-speed spindle system is the heart of a machine-tool and a high-quality machine-tool is always coupled with a spindle system that has high stiffness and better performance. Since high stiffness spindle system may provide the better abilities to withstand cutting-loading and to keep cutting stability that may satisfy the precision machining requirements, which can help production rate promotion and increase added value effectively. Therefore, the design and manufacturing of a spindle system with stiffness promotion for better machining precision and stability is one issue that the precision spindle makers have to deal with at the present time. A spindle design-aided software and a practical execution of experimental verification are combined together to develop a design technique for a high-speed spindle stiffness promotion construction. First of all, check all possible influencing factors on spindle stiffness and try to ascertain those main influencing factors or design parameters such as span of bearings, ball bearing contact angle, bearing preload, and bearing arrangement and configuration type in a spindle system, etc. Next, the spindle design-aided software is utilized to construct the geometrical model of a spindle system and to determine the spindle stiffness for each combination of design parameters. At the same time, the FEM is applied to simulate the modal analysis and temperature rise in bearings while heat sources generated in a spindle system are estimated preliminarily. By selecting spindle stiffness as an objective function which is subjecting to a constraint of bearing allowable temperature rise and the better design parameters combinations can thus be determined for expected spindle stiffness. A solid spindle system was fabricated according to this better design parameter combination. Finally, experiments were carried out on these spindle systems for static stiffness measurements, and monitoring on dynamic characteristics (run-out) and temperature rise in the bearings during the run-in tests. The results obtained from the simulations exhibits the similar trends to those of experiments. The major factors affecting the spindle stiffness are ball bearing contact angle, span of bearings, and bearing arrangement and configuration type. The greater is the contact angle of bearing and the smaller is the bearing span, the higher is the spindle stiffness which the higher temperature rise accompanied in operations unfortunately. For the bearing arrangement and configuration type, a better arrangement is with two bearings at the front-end and two at the rear in this improved spindle system.

碩士
國立中興大學
機械工程學系所
104
In the present machine tool industry, the calculation process of the bearing stiffness through a spindle''s dynamic state is still under development. Bearing stiffness is determined by the elastic deformation between bearing raceway surface and rolling element when bearing at force condition. The actual bearing stiffness can be known by inversing the natural frequency of the spindle through spindle dynamic experiment. Angular contact ball bearings are usually used in high-speed spindle. Bearing usually add preload to increase its stiffness. According the operation condition to select the preload force is important. The study is given different preload levels and used three simulation methods to discuss the bearing properties. The spindle/shaft natural frequencies are predicted by the Rayleigh-Ritz method and the finite element method. The commercial software of BEARINX is used to predict the bearing life, bearing stiffness and spindle/shaft natural frequencies. The difference between the Rayleigh-Ritz method and the finite element method are assumptions. One is assumed as a rigid body and another is assumed as a beam. The experiment of spindle are the rotation experiment and modal testing. Find the actual spindle natural frequencies and compare the simulation results.

碩士
國立中興大學
機械工程學系所
104
Machine tools are machines mainly for material removing based on cutting, drill-ing and grinding. Cutting precision and stability affect the manufacturing quality of a machine tool. Spindle is a key part of a machine tool. Machining precision, machining productivity and product quality are affected by spindle stiffness. Frequency response function (FRF) is selected to obtain spindle stiffness in this thesis. Excitation force and response are needed to obtain FRFs. Impact hammers, shakers and accelerometers are routinely used for obtaining FRFs. However, contact devices cannot be attached to a rotating spindle. In order to obtain FRFs of rotating spindle, excitation and transducer arranged by non-contact means in this thesis. A non-contact excitation system is designed and manufactured. Attractive force is generated by the electromagnets of the non-contact excitation system. Force trans-ducers, which act on the same line of action with attractive force, are installed to measure attractive force in real time. The non-contact excitation system is operated on two different test stands by exciting the test piece held by the tool holder. Laser Dop-pler Vibrometer (LDV) is selected to capture the response of rotating spindle. Attrac-tive force is measured by the force transducers installed in the non-contact excitation system. With the readings of the non-contact excitation system and LDV, FRFs of rotating spindle can be obtained experimentally. According to the FRFs, stiffness of rotating spindle is sought in this thesis.

碩士
大葉大學
自動化工程研究所
90
A spindle of a machine tool must be designed to provide the required performance features. Some factors, such as bearing’s type, bearing span, bearing preload and level of tool holder’s pull-in force will affect the spindle’s static and dynamic characteristics. The complicated relationships between these factors are urgent topics to be studied. Bearing is one critical component of spindle. Several design parameters must be properly selected by the designer. It is evident that higher preload will provide higher stiffness. However, this will limit the maximum rotational speed. In other words, low preload will result in an unacceptable deflection of spindle, or will cause chattering and noise when machining. Numerous studies have been published regarding to the determination of the optimum bearing span of machine tool spindles with two bearings. However, most of the spindles of machine tools are equipped with more than two bearings. Can simplified two-bearings model be used to determine the optimum span of the far more complicated three or four-bearing system? The purpose of this research is to determine the difference between the static performance of a real spindle mounted with four angular contact bearings and that of the simplified model. Several different 7/24 tool holders and different pull-in force of drawbar system are selected to exam the spindle’s static stiffness. The finite element(FE) analysis software package “I-DEAS” is utilized to build the spindle’s finite element model. The spindle’s static and dynamics characteristics were simulated with several different boundary conditions. The experimental and simulation results were then compared to ensure the FE model’s accuracy. Results showed that the deflection of the spindle housing is significant. The simplified model that did not consider the deflection of the spindle housing can not predict the static stiffness of the spindle accurately. I wish that the conclusions found in this research is helpful to the machine tool industry.

碩士
國立中正大學
機械系
89
The purpose of this work is to study the dynamic characteristics and cutting stability of a high-speed ball bearing spindle. It is known that the bearing stiffness becomes smaller at high speed due to the centrifugal force and gyroscope moment of the rotating elements of the bearings. Based on the model developed by Harris, we are able to analyze the dynamic characteristics of the ball bearings such as deformation, contact angle and stiffness under different preload conditions and rotating speed. Another objective of this work is to study the high speed cutting stability of the spindle. It is known that the natural frequency of the spindle is an important factor of the high speed cutting stability. However, most works related to cutting stability analysis are based on the natural frequency of the spindle tested at the static conditions. We follow the cutting stability theory developed by Smith and Tlusty, but consider the dynamic characteristics of the bearings at high rotating spindle. Through the computer simulation, we are able to analyze the high speed cutting stability under different bearing preloads. The simulation result has shown a significant change of the cutting stability at high rotation speed.

碩士
國立成功大學
機械工程學系
87
This thesis studies the stiffness of angular contact ball bearing and the natural frequencies of spindle-bearing system under different rotational speeds, radial loads and axial loads. We first predict the friction torque and temperature rise of bearing, and calculate the thermal expansion of bearing elements in the condition of temperature rise, and then derive the bearing stiffness with considering the centrifugal forces of balls of bearing. After getting bearing stiffness, the natural frequencies of the spindle-bearing system can be obtained in different rotational speeds and loads. From theoretical and experimental results, we find that rotational speeds and axial loads have great influence on bearing friction torque, temperature rise and the stiffness of bearing. When the speed is higher, the friction torque and temperature rise is higher, but bearing stiffness is lower. In predictions of natural frequencies, including first and second natural frequency, the theoretical results are higher than experimental data, but the difference is acceptable. And in analysis of the vibration amplitude of test bearing, we take the base excitation model to simulate bearing vibration, and assume the maximum vibration amplitude of base is a constant in constant rotational speed. The experimental results show that the differences between experimental and theoretical data are large. And the reason maybe the assumptions of bearing vibration model are not correct.

碩士
國立勤益科技大學
機械工程系
101
In this study, the finite element method was employed to predict the tool system and interface stiffness of tool holder system on the dynamic frequency response of high speed spindle. Since the interface characteristics of tool holder system tend to affect the spindle, therefore tool holder system is very important. In order to assess the influence of interface stiffness on the vibration characteristic of spindle unit, we first created a three dimensional finite element model of a high speed spindle system integrated with tool holder. The key point for the creation of FEM model is the modeling of the rolling interface within the angular contact bearings and the tool holder interface. The former can be simulated by a introducing a series of spring elements between inner and outer rings. The contact stiffness was calculated according to Hertz contact theory and the preload applied on the bearings. The interface stiffness of the tool holder was identified through the experimental measurement and finite element modal analysis. Current results show that the dynamic stiffness was greatly influenced by the tool holder system. In addition, variations of modal damping, static stiffness and dynamic stiffness of the spindle tool system were greatly determined by the interface stiffness of the tool holder which was in turn dependent on the draw bar force applied on the tool holder; while the correlation among them were not in linear relationship. Current results verify that when the drawbar force was controlled at 250kg, the spindle tool shows highest dynamic stiffness and the maximum axial depth for stable machining. Overall, this study demonstrates that identification of the interface characteristics of spindle tool holder is of very importance for the refinement of the spindle tooling system to achieve the optimum machining performance.

碩士
國立彰化師範大學
機電工程學系
97
The objective of this study is to apply finite element analysis to analyze the dynamics of the column and spindle head of Machine tool. The Pro/E is employed to construct the structure the Machine tool, including 3D assembly model. The problem is solved by the use of finite element method. The Pro/Mechanica is applied to obtain crucial designing parameters of dynamics. The variation of natural frequencies, mode shapes, stress distribution and structural rigidity of column and spindle head due to the change of their structures are studied. The result indicates that, as predicted, the location of the axis of center of gravity plays a crucial role; the displacement and torque diminishes with the decrease of the distance between the gravity axis and the symmetrical axis of the machine tool.

碩士
國立中興大學
機械工程學系所
106
Motorized spindle is explored in this paper. It uses front and rear bearings as supports. The motor rotor and stator are not in contact, so the dynamic performance of the spindle is mainly affected by the properties of bearing. The stiffness of bearing will change by the squeezing of the ball, the lubrication and deformation in rotating state. FRFs can be measured by using impact hammers and accelerometers. Non-rotating state of the bearing rigidity can be obtained by the analysis of frequency response function (FRF). However the typical impact test cannot be used to measure the rotating spindle. Thus it is difficult to analyze the stiffness of spindle in the actual rotation state. A non-contact excitation system is designed in this paper and using the Laser Doppler Vibrometer (LDV) to measure. The design of the non-contact exciter is improved upon the first generation exciter. These system will carry out to measure and analyze. Through the electromagnetism, exciter acts on spindle to generate a swept signal excitation. FRFs will be plotted using experimental data and calculate the stiffness of spindle at different speeds.

Research has uncovered an essential role of proper abdominal muscle function in ensuring the health and integrity of the lumbar spine. The anatomical arrangement of the abdominal musculature (rectus abdominis, external oblique, internal oblique, transverse abdominis) and intervening connective tissues is unique in the human body. Despite the hypothesized importance and uniqueness of the abdominal muscles, very little research has been directed to understanding their role from a neuro-mechanical standpoint. Thus, this thesis was designed to study the neuro-activation and mechanical characteristics of the abdominal musculature and connective tissues, with a specific focus on torso stiffening mechanisms. Several experiments were performed and unified around this theme. The first study explored the fundamental relationship between EMG muscle activation recordings and the moments generated by the trunk musculature. This study was novel in that investigation of the abdominal musculature was augmented with consideration of antagonist muscle co-activation. The main finding was that the EMG-moment relationships were quite similar in both the abdominal and extensor muscle groups; however, the form of this relationship differed from that often reported in the literature. Specifically, consideration of antagonist muscle moments linearized the EMG-moment relationship of the agonist muscle groups. Once this activation-moment relationship had been established, the next line of questioning explored the association between torso muscle activation, driven through the abdominals, and torso stiffness. Two studies addressed this issue: the first examined the intrinsic resistance of the torso to bending in the flexion, extension, and lateral bend directions, while varying the levels of torso muscle activation; the second examined the response of the trunk to perturbations while varying the levels of torso muscle activation under the presence of limited reflexes. The first of these two studies demonstrated a rise in trunk stiffness as muscle activation increased over the lower 40% of range of motion. At greater ranges of motion in flexion and lateral bend the trunk appeared to become less stiff as the musculature contracted to higher levels. The latter study revealed substantial spinal displacements in response to trunk perturbations, indicating that in the absence of reflex activity, the stiffness produced by muscular contraction may be inadequate to stiffen the torso to prevent damage to spinal tissues. The fourth study was designed to enable in-vivo observation of abdominal muscle and connective tissue deformation using ultrasound imaging. During relatively simple abdominal contractions, the oblique aponeurosis demonstrated surprising deformation patterns that often exhibited the characteristic of a negative Poisson’s ratio. This was hypothesized to be facilitated by the composite laminate arrangement of the abdominal wall, whereby the loose connective tissues separating layers of collagen fibres may allow for separation of adjacent layers, giving the appearance of structural volume expansion. Further, a lateral displacement of the rectus abdominis muscle was noted in a majority of contractions, highlighting the dominance of the laterally oriented forces generated by the oblique muscles. The final study questioned, at a basic level, the nature of the anatomical arrangement of the abdominal muscle-connective tissue network. Examining the contraction of the rat abdominal wall uncovered the transfer of muscularly generated force and stiffness through the connective tissues binding the layered muscles. This suggests a functionality of the abdominal wall as a composite laminate structure, allowing substantial multi-directional stiffness to be generated and transmitted around the torso, thereby enhancing the ability to effectively stabilize the spine.

Core exercise is a staple of many physical training regimens with goals ranging from improving athletic performance to rehabilitation of spine and knee injuries. Traditionally, dynamic movements such as flexion, lateral bending and twisting core exercise maneuvers are used in training programs; an approach consistent with training the distal limbs where muscular effort is mostly devoted to creating motion. However, knowledge of the functional anatomy of core musculature and spine injury mechanisms questions the use of these types of exercises. Alternative core exercises make use of isometric postures and static bracing to create muscular activation while minimizing spine loads and injury mechanisms linked with movement. This study aims to quantify the effect of various core training programs on the change of passive and active stiffness properties of the torso. This study was driven by several curiosities: 1) Isometric core exercises are reported to help some people who have low back pain. Is there a short lasting ???enhanced stiffness??? after performing these exercises? 2) Core training regimens use Isometric and Dynamic core exercises to enhance core bracing properties. Is one method superior to the other in terms of enhancing core stiffness? 3) If adaptations to core stiffness can be achieved with core exercise, do these adaptations differ between beginners and trained individuals? Twenty four healthy male subjects (22.9 ?? 2.7 years, 1.79 ?? 0.06 m, 77.5 ?? 10.8 kg) were recruited for short and long term core training. Of the overall population, twelve subjects (21.7 ?? 1.89 years, 1.80 ?? 0.076 m, 78.3 ?? 12.3 kg) were University students with little to no experience in performing regular core exercise. The other twelve subjects (24.2 ?? 2.89 years, 1.79 ?? 0.047 m, 76.8 ?? 9.71 kg) were athletically trained with at least one year of experience performing regular core exercise (minimum three times per week). This study was a repeated measures design examining short and long term core stiffness (active and passive) and range of motion before and after a single fifteen minute bout of isometric core exercise and a six week core training program. The long term training groups were divided evenly into isometric, dynamic and control groups. The Isometric group received a six week training program consisting of core bracing exercises ranging from basic static bodyweight exercises to weighted exercises with additional challenge of distal limb mobility while maintaining a braced core, while dynamic group exercises consisted of movement and speed based core exercises. The Control group received no further training during this period. All subjects were asked to refrain from any extra core demands not given by the researchers. After the training period was complete all subjects were retested for stiffness and range of motion. Passive stiffness tests were performed using a frictionless bending apparatus for flexion, extension, left and right lateral bend and left and right axial twist directions. Active stiffness was assessed via a ???quick release??? mechanism, preloaded with a 16 kg mass and randomly released to assess active extension. Participants were instrumented with unilateral electromyography (EMG) of selected core musculature and electromagnetic signals for motion capture for lumbar kinematics. To determine if training had an effect on dependent variables a series of repeated measures ANOVAs were performed; short term training utilized a 2x2 Repeated Measures ANOVA using the pre/post condition and training experience (na??ve vs. savvy) as factors. Long term training utilized a 3x2x2 Repeated Measures ANOVA using training group (Isometric vs. Dynamic vs. Control), training experience (na??ve vs. savvy) and pre/post condition as factors. In general, short term isometric core training increased core stiffness in all directions for na??ve and savvy subjects. Comparisons between these two subject groups did not yield any significant differences. After long term training stiffness was increased the greatest in the Isometric training group with both na??ve and savvy subjects. Dynamic training yielded significant increases in stiffness but for only one direction in each subject group (right lateral bend in na??ve subjects and left axial twist in savvy subjects). The Control group did not show any significant changes in stiffness. Comparisons between training groups and training experience did not yield any significant differences. Isometric training lead to significant stiffness increases in all test except for passive and active extension in na??ve subjects, and similar results were found for savvy subjects except for right lateral bend not showing any significant changes. Researchers believe reasons for insignificant changes are related to high variances which may be due to inadequate statistical power and a wide variety of responses within each subject group. Though some analyses showed inadequate statistical power due to small sample sizes it should be noted that this research is the first of its kind investigating the trainability of core stiffness in the short and long term, and thus difficult to establish sample sizes without any baseline values. The findings of this study can be directly applied to core training for rehabilitation and athletic function. Enhancements in core stiffness are thought to subsequently enhance traits such as load bearing ability, pain management and athletic function. The results of short term training give insight into how a short training session performed prior to a load bearing task can make the task safer and easier to perform. The results of long term training show that Isometric training performed over a long duration may induce more permanent enhancements to stiffness and core function.

Introduction: The purpose of this study was to determine the effect of spinal manipulation therapy (SMT) duration and amplitude on spinal stiffness. Methods: Simulated SMTs were performed at the L6 spinous process in twenty-two felines. SMTs ranging from 25 to 250 ms duration were performed. Groups 1 and 2 received maximal displacements of 1.0mm to 3.0mm. Groups 3 and 4 received maximal loads of 25% to 85% body weight. Local stiffness was quantified by applying an indentation to the vertebra. Results: Repeated SMTs caused minimal changes in stiffness. The interaction effect of duration X displacement in Groups 1 and 2, and the effect of duration in Group 3 were significant. Conclusion: Repeated SMTs cause minimal changes in stiffness thought to be due to a viscoelastic response. Some of the changes following select SMT conditions may be the result of an interaction effect between SMT duration and amplitude. No specific threshold condition was identified as causing a greater stiffness change.
Physical Therapy

abstract: Introduction. Intervertebral disc degeneration (DD) is one of the most common diagnoses in patients with neck pain and contributes to worldwide disability. Despite the advances in diagnostic imaging today, little is known about functional status of cervical DD. The purpose of this research was to 1) develop and validate an ovine model of cervical spine DD, 2) to quantify and compare the effect of disc lesions on dynamic spinal stiffness, and 3) study the effect of disc lesions on spinal accelerations and displacements during two types of spinal manipulative therapy (SMT). Methods. Fifteen sheep received surgically induced disc injury to the mid-cervical spine via scalpel wound a minimum of five months earlier and 15 sheep served as controls. All animals were biomechanically assessed at the level of the lesion using swept-sine mechanical loads from 0-20 Hz under load control to quantify dynamic dorsoventral (DV) spine stiffness (load/deformation, N/mm). The effect of disc lesion on stiffness was assessed using a one-factor repeated measures ANOVA comparing 32 mechanical excitation frequencies. Tri-axial accelerometers rigidly attached to adjacent vertebrae across the target level further evaluated the effect of disc lesion on spinal motion response during two types of SMTs. A 2x6x2 repeated measures ANOVA examined the effect of disc lesion and SMT force-time profile on spine motion response. Postmortem histological analysis graded specimens at the target site and comparison was made with descriptive statistics. Results. Annular disc tears were only observed in the disc lesion group and the mild degeneration identified was localized to the injured annular tissue that did not progress to affect other areas of the disc. No difference in overall DD grading was found among the groups. DV stiffness was significantly increased in the disc lesion group by approximately 34% at 31 of 32 frequencies examined (p<.05). SMTs resulted in decreased displacements in the disc lesion group (p<.05), and SMT type significantly influenced spinal accelerations for both the DV and axial planes. Conclusion. Disc lesions in the ovine cervical spine produce localized annular degenerative changes that increase the cervical spine dynamic stiffness and reduce its spinal motion response during manual examination and treatment that is further augmented by the force-time profile administered by the clinician.
Dissertation/Thesis
Doctoral Dissertation Kinesiology 2015

碩士
國立中央大學
機械工程研究所
97
Generally,the marrow of intervertebral disk was begun degenerating by increasing age of human.This degenerating reduces the thickness of an intervertebral disk & hypertrophy of ligament & facet joint,so that it gives rise to stress the nerve and resulted in DDD. The solution for this kind of case is that we use the static fixation to recover the initial thickness of intervertebral disk by a surgical operation, so that we can solve the problem of degeneration of intervertebral disk. This research utilizes the "SolidWork" to construct the model of lumbar vertebra & static fixation.Firstly, we put the muscle force into the model of lumbar vertebra to make this analysis close to the status of reality. It analyzes three different kinds of model of lumbar vertebra via cosmosworks''s software of limited element : the normal lumbar vertebra、the lumbar vertebra with implanting an alloy of titanium,the lumbar vertebra with implanting 316L Stainless Steel fixation,there are three kinds of model to proceed the analysis of limited element. The majorly simulation is to analyze the height,change of angle,stress of nucleus pulposus,stress of pedicle of the model of lumbar vertebra and the status of stress distribution.

Background: Prolonged sitting in an automobile seat may alter the passive tissue stiffness of the lumbar spine differentially in males and females. Gender specific ergonomic interventions may be indicated for the automobile seat design. Purpose: To compare time-varying passive lumbar spine stiffness in response to a two hour simulated driving trial with time-varying lumbar spine and pelvic postures during sitting in an automobile seat. A secondary purpose was to investigate gender differences in lumbar spine stiffness, seat/occupant pressure profile, discomfort rating and posture. Methods: Twenty (10 males, 10 females) subjects with no recent history of back pain were recruited from a university population. Participants completed a simulated driving task for two hours. Passive lumbar range of motion was measured on a customized frictionless jig before, halfway through and at the end of the two-hour driving trial. Changes in the passive moment-angle curves were quantified using the transition zone slopes, breakpoints and maximum lumbar flexion angles. Lumbar spine and pelvic postures were monitored continuously during the simulated driving trial with average and maximum lumbar flexion angles as well as pelvic tilt angles being calculated. Results: Both men and women initially demonstrated an increase in transitional zone stiffness after 1 hour of sitting. After 2 hours of sitting, transitional zone stiffness was found to increase in males and decrease in females. During sitting, women were found to sit with significantly greater lumbar flexion than males and to significantly change the amount of lumbar flexion over the 2 hour period of simulated driving. Conclusions: Postural differences during simulated driving were demonstrated between genders in this study. In order to prevent injury to the passive elements of the spine during prolonged driving, gender specific ergonomic interventions, such as improved lumbar support, are indicated for the automobile seat.

M. Tech.
Objective: This study was conducted in order to compare the effectiveness of Chiropractic spinal manipulative therapy (SMT) combined with guided imagery versus only guided imagery in the treatment of chronic neck pain and stiffness. Chiropractic SMT is aimed at treating neck pain as well as increasing the range of motion (ROM) of the neck. Guided imagery is aimed at reducing stress levels within the patient with a secondary effect of reducing tension in the neck muscles. This study therefore also has a secondary purpose to assess the effects of stress on chronic neck pain. It was hypothesised that Chiropractic SMT combined with guided imagery would be more effective in the reduction of chronic neck pain than guided imagery or alone. This is based on the fact that Chiropractic SMT has been exhaustively proven to be effective in treating chronic neck pain as well as increasing cervical range of motion. Guided imagery has also been proven to be effective in reducing stress even though there has not been enough research on its effect on chronic neck pain and cervical range of motion. Methods: Patients were recruited by means of placing advertisements in and around the University of Johannesburg. Patients that presented to the Chiropractic day clinic with chronic neck pain between the ages of 18 and 30 were included in this study. The participants were then randomly placed in one of two groups. Group A received four sessions of Chiropractic SMT combined with two sessions of guided imagery while Group B received two sessions of guided imagery relaxation techniques and four sessions of detuned ultrasound (U/S). The researcher performed all the sessions of Chiropractic SMT and detuned U/S while Dr A. Fourie (a registered Counselling Psychologist) performed the Guided Imagery sessions. In the initial visit patients in both groups had to undergo a history taking, physical examination and cervical spine regional examination. They were required to sign subject information and consent form and complete a Neck Disability Index (NDI) Questionnaire, Numerical Pain Rating Scale and the Stress Questionnaire. The researcher measured their cervical range of motion on the first and last treatments. The objective and subjective data was collected on the first visit and again on the final visit.

There are several reasons to research the effects of axial twist exposures and the resulting loading on the spine. The lack of consensus from the limited work that has previously examined the role of axial twist moments and motions in the development of spine injuries or generation of low back pain is the primary reason. From recently published works, axial twist moments appear to represent an increased risk for injury development when it acts in concert with loading about other physiological axes (i.e. flexion, extension, and compression). However, there is a large body of epidemiologic data identifying axial twist moments and/or motion as risk factors for low back disorders and pain, demonstrating the need for this series of investigations. It is likely that these combined exposures increase risk through altering the spine’s load distribution (passive resistance) by modifying the mechanics, but this deduction and related causal mechanism need to be researched. The global objective of this research was focused on determining whether there is evidence to support altered load distribution in the spine, specifically between the intervertebral disc and facets, in response to applied axial twist moments (when added in combination with one and two axes of additional loading). Also included was whether these modes of loading can modify spine mechanics and contribute and/or alter the development of damage and pain. This objective was addressed through one in-vivo (Drake and Callaghan, 2008a– Chapter #2) and three in-vitro (Drake et al., 2008– Chapter #4; Drake and Callaghan, 2008b– Chapter #5; Drake and Callaghan, 2008c– Chapter #6) studies that: (1) Quantified the amount of passive twist motion in the lumbar spine when coupled with various flexion-extension postures; (2) Documented the effects of flexion-extension postures and loading history on the distance between the facet articular surfaces; (3) Evaluated the result of axial twist rotation rates on acute failure of the spine in a neutral flexion posture; and (4) Explored whether repetitive combined loading has the ability to cause enough deformation to the spine to generate pain. Through the combination of findings previously reported in the literature and the outcomes of Drake and Callaghan (2008a– Chapter #2) and Drake et al. (2008– Chapter #4), a postural mediated mechanism was hypothesized to be responsible for governing the load distribution between the facet joints and other structures of the spine (i.e. disc, ligaments). Increased flexed postures were found to decrease the rotational stiffness by resulting in larger twist angles for the same applied twist moment in-vivo relative to a neutral flexion posture (Drake and Callaghan, 2008a– Chapter #2). This suggested there might be an increased load on the disc due to a change in facet coupling in these combined postures. Similarly, increased angles were observed in flexed and twisted postures for in-vitro specimens relative to a neutral flexion posture. These observed differences were found to correspond with altered facet joint mechanics. Specifically that flexed twisted postures increased the inter-facet spacing relative to the initial state of facet articulation (Drake et al., 2008– Chapter #4). These finding supported the postulated postural mechanism. Therefore, in a neutral posture the facet joints likely resisted the majority of any applied twist moment based on the limited range of motion and higher axial rotational stiffness responses observed. It was suspected that the changes in mechanics would likely cause a change in the load distribution however the magnitude of change in load distribution remains to be quantified. Further support for this postulated postural mechanism comes from the mode of failure for specimens that were exposed to 10,000 cycles of 5° axial twist rotation while in a static flexed posture (Drake and Callaghan, 2008c– Chapter #6), and neutrally flexed specimens exposed to 1.5° of rotation for 10,000 cycles reported in the literature. Without flexion, the failure patterns were reported to occur in the endplates, facets, laminae and capsular ligaments, but not the disc. However, with flexion the repetitive axial twist rotational displacements caused damage primarily to the disc. If the load distribution was unchanged, the higher axial rotation angle should have caused the specimen to fail in less cycles of loading, and the failure pattern should not have changed. Modulators of this hypothesized mechanism include the velocity of the applied twist moment and the effects these have on the failure parameters and injury outcomes. The three physiologic loading rates investigated in this work were not shown to affect the ultimate axial twist rotational failure angle or moment in a neutral flexion/extension posture, but were shown to modify flexion-extension stiffness (Drake and Callaghan, 2008b– Chapter #5). All of the flexion-extension stiffness values post failure, from a one-time axial twist exposure, was less than those from a repetitive combined loading exposure that has been established to damage the intervertebral disc but not the facets. Therefore, it is likely that the facet joint provides the primary resistance to acute axial twist moments when the spine is in a neutral flexion posture, but there appears to be a redistribution of the applied load from the facets to the disc in repetitive exposures. The aforementioned studies determined there are changes in load distribution and load response caused by altered mechanics resulting from twist loading, but whether the exposures could possibly produce pain needed to be addressed. Previous research has determined that the disc has relatively low innervation in comparison to the richly innervated facet capsule and vertebra, with only the outer regions being innervated. Likewise, it is assumed that pain could be directly generated as the nucleus pulposus disrupted the innervated outer annular fibres in the process of herniation. Also, direct compression of the spinal cord or nerve roots has been shown to occur from the extruded nucleus and result in the generation of pain responses. Additionally, the nucleus pulposus has been shown to be a noxious stimulus that damages the function and structure of nerves on contact. The other source of nerve root compression commonly recognized is a decrease in intervertebral foramina space, which was previously believed to only be caused through losses in disc height. However, decreased intervertebral foramina space due to repetitive motions appears to be a viable pain generating pathway that may not directly correspond to simply a loss of specimen or disc height (Drake and Callaghan, 2008c– Chapter #6). This is new evidence for combined loading to generate pain through spinal deformation. The objective of many traditional treatments for nerve root compression focus on restoring lost disc height to remove the nerve root compression. Unfortunately, nerve root compression caused by repetitive loading may not be alleviated through this approach. This collection of studies was focused on determining whether altered load distribution in the spine, specifically between the intervertebral disc and facets, in response to applied axial twist loading (when added in combination with one and two axes of additional loading) was occurring, and examining how these modes of loading can contribute and/or alter the development of injury and pain. Therefore, findings generated from this thesis may have important implications for clinicians, researchers, and ergonomists.