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Evaluation tridimensionnelle du complexe scapulo-huméral et du rachis cervical : méthodologie d'évaluation et applications cliniques / 3D assessment of the shoulder and the cervical spine : assessment methodologies and clinical applicationsRoren, Alexandra 29 October 2012 (has links)
Le but de ce travail est d’améliorer les techniques de mesure cinématique tridimensionnelle (3D) afin d’étudier les schémas cinématiques du complexe de l’épaule et du rachis cervical chez des sujets sains et pathologiques. La première partie de ce travail propose un rappel d’anatomie fonctionnelle, une revue de la littérature de la cinématique du complexe scapulo-huméral et une mise au point sur les techniques de mesure de ces deux complexes articulaires. La deuxième partie de ce travail a pour objectif d’évaluer à partir d’études cliniques originales : - la reproductibilité des techniques de mesure des rotations des complexes scapulo-huméral et cervical et d’en proposer une amélioration par une analyse simultanée des translations du barycentre de la scapula ainsi que par la mesure couplée des deux complexes articulaire. - les schémas cinématiques de la scapula dans différents modèles de pathologies ostéo-articulaires au cours de gestes analytiques et fonctionnels. En conclusion, ce travail de thèse met en évidence : une variabilité intra-individuelle dans la capacité à reproduire un mouvement à l’identique avec le membre supérieur et à conserver la même précision dans le repositionnement de la tête. - des mouvements de translation 3D de la scapula, dont certains de grande amplitude, associés aux rotations des mouvements de faible amplitude du rachis cervical associés aux mouvements du membre supérieur en faveur de son rôle proprioceptif. - des schémas cinématiques scapulaires spécifiques : - de la lésion neurologique en cas de scapula alata dynamique. - de la nature fonctionnelle de la tâche en cas de pathologies ostéo-articulaires communes / The aim of this work was to improve the methods of kinematic assessment of the shoulder complex and of the cervical spine in order to improve understanding of scapular and cervical spine kinematics in asymptomatic and symptomatic subjects. The first part of this work provides a reminder of functional anatomy, a literature review of the 3D kinematics of the shoulder complex and issues relating to measurement techniques of both articular complexes. The second part is based on original clinical studies assessing: - the reliability of the measurement techniques of the rotations of both articular complexes and their enhancement by addition of scapular translations and the coupled mobility of the cervical spine and shoulder complexes. - the patterns of scapular kinematic in different ostéo-articular pathologies In conclusion, this work highlights: - intra-individual variability in the ability to reproduce a movement with the upper arm and in the accuracy of repositioning the head . -3D scapular translations (some with large ranges) associated with scapular rotations. - small movements of the cervical spine associated with upper limb movements relating to the proprioceptive role of the cervical. - spine specific scapular kinematic patterns depending on: - neurological lesions in the case of dynamic scapula alata, - the type of movement in common osteo articular pathologies
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Degenerativní změny krční páteře se zaměřením na výhřez meziobratlové ploténky a její verifikace pomocí zobrazovacích metod a 3D modelu / Degenerative changes in the cervical spine with a focus on the intervertebral disc prolapse and its verification using imaging methods and 3D modelPíglová, Tereza January 2012 (has links)
Title: Degenerative changes in the cervical spine with a focus on the intervertebral disc prolapse and its verification using imaging methods and 3D model Objectives: The aim of this work is to describe the problems of degenerative changes in the cervical spine with a focus on the intervertebral disc prolapse. The second part deals with the possibility of imaging methods that are able to detect pathological processes. Part of this work is the study of three cases of patients with a diagnosis of disc herniation. In conclusion, there are some possibilities of 3D modeling of the cervical spine. Methods: The theoretical part is based on the available literature. Images from MRI were obtained from medical facilities in Prague, described and assessed by a specialist. After studying the functions suitable graphical programs were created 3D models of the cervical spine. Results: Degenerative changes in the cervical spine naturally come from the aging of the organism, but a number of modifiable factors accelerating the onset. Among such factors include especially hypokinesia and unilateral overloading of cervical spine. Modern imaging techniques can in detail detect these pathological processes, but are limited by the patient's position during the investigation. The resulting series of images are used as...
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Estudo morfométrico do atlas / Morphometric study of the atlasFerreira Filho, Narcélio Mendes 09 November 2018 (has links)
O tratamento cirúrgico das afecções que acometem a coluna cervical alta colocam em risco estruturas neurovasculares, como a artéria vertebral e a medula espinhal, durante a colocação de parafusos transarticulares em C1-C2 e parafusos de massa lateral em C1. O presente estudo visa determinar os parâmetros anatômicos do atlas (C1) em uma amostra da população brasileira, compará-los aos resultados já apresentados na literatura para outras populações e, assim, identificar e alterar as indicações dos implantes utilizados no tratamento das afecções da coluna cervical alta. Foi realizado um estudo observacional retrospectivo de um banco de dados prospectivo, incluindo 100 pacientes atendidos em um hospital terciário, entre janeiro de 2012 a dezembro de 2013. Foram utilizados cortes axiais e sagitais de tomografias computadorizadas. Os parâmetros estudados foram, no corte axial: o ponto de entrada do parafuso (DTPPE), o ângulo de segurança (ADSPA), o tamanho ideal do parafuso (TPA) e o tamanho da massa lateral entre os forames vertebral e transverso (DCVFT); no corte sagital foi medido o tamanho ideal do parafuso (TPS), o ângulo de segurança (ADSPS) e a espessura do arco posterior (EAP). Todos os parâmetros foram divididos de acordo com a idade, sexo e o lado esquerdo e direito. Resultados: O ponto de entrada dado pelo DTPPE foi 21,86 ± 1,5 mm a esquerda e 22,7 ± 1,44 mm a direita no sexo masculino; e 20 ± 1,4 mm a esquerda e 20,24 ± 1,34 mm a direita no sexo feminino. A zona de segurança (ADSPA) foi 23,68 ± 6,12º a esquerda e 24,0 ± 5,82º a direita no sexo masculino e 18,09 ± 5,46º a esquerda e 18,57 ± 5,34º a direita no sexo feminino. A espessura do arco posterior (EAP) encontrada no sexo masculino foi 8,95 ±1,75 mm a esquerda e 8,92 ± 2,22 mm a direita, no sexo feminino encontramos uma espessura menor de 7,21 ± 1,53 mm a esquerda e 7,41 ± 1,58 a direita. Por meio de uma técnica original e reprodutível de avaliação de exames de tomografia computadorizada, os parâmetros anatômicos do Atlas encontrados na amostra da população estudada em nosso estudo foram semelhantes aos apresentados previamente na literatura. No entanto, foram observadas diferenças entre os sexos. Assim, recomendamos a utilização do exame de tomografia computadorizada como método de avaliação pré-operatória quando a fixação da massa lateral pelo arco posterior do Atlas for empregada. / The surgical treatment of conditions affecting the high cervical spine puts at risk neurovascular structures, such as the vertebral artery and the spinal cord, during the placement of transarticular screws in C1-C2 and lateral mass screws in C1. The present study aims to determine the anatomical parameters of the atlas (C1) in a sample of the brazilian population, to compare them with the results already presented in the literature for other populations and thus to identify and change the indications of the implants used in the treatment of spinal affections cervical high. A retrospective observational study of a prospective database including 100 patients treated at a tertiary hospital between January 2012 and December 2013 was performed. Axial and sagittal sections of computed tomography were used. The parameters studied were, in the axial section: the screw entry point (DTPPE), the safety angle (ADSPA), the ideal screw size (TPA) and the lateral mass size between the vertebral and transverse foramina (DCVFT) ; in the sagittal cut, the ideal screw size (TPS), the safety angle (ADSPS) and the posterior arch thickness (EAP) were measured. All parameters were divided according to age, sex and left and right side. The entry point given by the DTPPE was 21.86 ± 1.5 mm on the left and 22.7 ± 1.44 mm on the right in the male; and 20 ± 1.4 mm on the left and 20.24 ± 1.34 mm on the right in the female. The safety zone (ADSPA) was 23.68 ± 6.12 ° on the left and 24.0 ± 5.82 ° on the right in the male sex and 18.09 ± 5.46 ° on the left and 18.57 ± 5.34 ° on the right in females. The posterior arch thickness (EAP) found in males was 8.95 ± 1.75 mm on the left and 8.92 ± 2.22 mm on the right, in females we found a thickness less than 7.21 ± 1.53 mm on the left and 7.41 ± 1.58 on the right. Using an original and reproducible technique for the evaluation of CT scans, the Atlas anatomical parameters found in the sample of the population studied in our study were similar to those previously reported in the literature. However, differences between the sexes were observed. Thus, we recommend the use of computed tomography (CT) examination as a preoperative evaluation method when lateral mass fixation by the posterior arch of the Atlas is used.
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Avaliação da mobilidade da coluna cervical e do segmento vertebral C1/C2 com o flexion rotation test em pacientes com migrânea episódica e crônica / Evaluation of the mobility of the cervical spine and vertebral segment C1/C2 with the flexion rotation test in patients with episodic migraine and chronicOliveira, Ana Izabela Sobral de 13 May 2016 (has links)
Objetivo: Investigar a mobilidade cervical e do segmento C1/C2 com o Flexion Rotation Test (FRT) em pacientes com migrânea crônica e episódica, e analisar a influência da cronicidade, da incapacidade cervical e da alodinia cutânea nessa mobilidade. Métodos: Foram avaliadas 85 mulheres com idade de 18 a 55 anos divididas em três grupos: migrânea crônica (MC)(n=25), migrânea episódica (ME)(n=30) e controle (n=30). O FRT e a avaliação da amplitude de movimento cervical foram avaliados com o instrumento CROM® acoplado a cabeça. Foram realizadas três repetições de cada movimento, aleatorizadas previamente. A média das repetições foi utilizada para a análise dos dados. A incapacidade cervical foi avaliada pelo Neck Disability Index e a alodinia cutânea pelo Allodynia Symptom Checklist (ASC-12). Quanto a mobilidade, os grupos foram comparados utilizando o teste Manova com pós teste de Bonferroni. A razão de prevalência foi utilizada para identificar a associação entre o diagnóstico de migrânea e a cronicidade com a mobilidade do segmento C1/C2. A regressão linear simples foi usada para identificar a influência da incapacidade cervical e da alodinia cutânea no FRT. Resultados: Todos os grupos diferiram nos valores do FRT (MC = 25.79º e 26.81º; ME = 33.44º e 32.18º; controle= 41.98º e 40.18º; nos movimentos a direita e esquerda, respectivamente, p<0.05). Apenas o grupo MC diferiu na amplitude de movimento cervical (p<0.05) do grupo controle em todos os movimentos. Pacientes com migrânea apresentaram 2.85 vezes mais associação ao risco de apresentar hipomobilidade no segmento C1/C2 comparado aos controles. A incapacidade cervical influenciou em 19% a amplitude desse segmento independente do diagnóstico de migrânea, enquanto que a alodinia cutânea não apresentou influência significativa. Conclusão: Mulheres com migrânea apresentam reduzida amplitude de movimento cervical, especialmente no segmento C1/C2, e maior risco de desenvolver hipomobilidade cervical superior comparado a mulheres sem cefaleia, sendo este risco aumentado pela cronicidade da doença. Além disso, a incapacidade cervical influencia no resultado do FRT, contrariamente a alodinia cutânea / Objective: To investigate the cervical and C1/C2 mobility with the Flexion Rotation Test (FRT) in patients with chronic and episodic migraine, and analyze the influence of the chronicity, cervical disability and cutaneous allodynia in this mobility. Methods: Were analyzed 85 women with age between 18 and 55 years, divided in three groups: chronic migraine (CM)(n=25), episodic migraine (EM)(n=30) and control (n=30). The FRT and cervical range of motion has been applied with the CROM® device coupled to the head. Were conducted three repetitions of each movements, randomized previously. The mean of the repetitions was used for data analysis. Cervical disability was assessed by the Neck Disability Index and cutaneous allodynia by the Allodynia Symptom Checklist (ASC-12). As for mobility, the groups were compared using MANOVA test with post-hoc de Bonferroni. The prevalence ratio was used to identify the association between the migraine diagnostic and chronicity with C1/C2 mobility, and simple linear regression was used to identify the influence of cervical disability and cutaneous allodynia in FRT. Results: All groups differed in the FRT (CM = 25.79º and 26.81º; EM = 33.44º and 32.18º; control = 41.98° and 40.18º; right and left movements, respectively, p <0.05). Only, CM group differed in cervical range of motion (P <0.05) to the control group in all movements. Migraine patients shows 2.85 times more association with risk for C1/C2 hypomobility compared to controls. Cervical disability influenced by 19% the ranger of this segment independent the diagnosis of migraine, while the cutaneous allodynia has not a significant influence. Conclusion: Women with migraine have reduced cervical range of motion, especially in the C1/C2 segment, and higher risk of develop superior cervical hypomobility compared to women without headache, and this risk was increased by the chronicity. Also, cervical disability influence the FRT, in contrast to cutaneous allodynia
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Estudo morfométrico do pedículo cervical / Morphometric study of the cervical pedicleNascimento, Anderson Luis do 13 February 2017 (has links)
A inserção do parafuso pedicular cervical é um procedimento cirúrgico tecnicamente desafiador. Assim, o amplo conhecimento da morfologia das vértebras cervicais, particularmente do pedículo, é essencial para minimizar o risco de ferimentos graves a estruturas neurovasculares. O objetivo deste estudo foi conduzir uma avaliação detalhada de exames de tomografia computadorizada (TC) na população brasileira do ponto de entrada, trajetória, e dimensões dos pedículos da coluna cervical. Duzentos pacientes consecutivos foram retrospectivamente avaliados utilizando a TC da coluna cervical, com a reconstrução da imagem de cada vértebra no plano axial com 2 mm, e no plano sagital com 3 mm. Os parâmetros no plano axial incluíram a espessura pedicular (EP), o comprimento pedicular axial (CPA), o ângulo pedicular transverso (APT) e a distância do ponto de entrada ao ângulo entre a lâmina e o processo espinhoso (DPE). As medidas no plano sagital envolveram a altura pedicular (AP) e o ângulo pedicular sagital (APS). A EP e AP média são menores nos pacientes do sexo feminino do que nos pacientes do sexo masculino em todas as vertebras cervicais, porém não houve diferença significativa do APT entre os sexos. O APS variou de 15,2° a 23,7°. Os valores médios do CPA e DPE apresentaram uma tendência a diminuir de proximal para distal na coluna cervical. A EP encontrada foi menor que 4 mm em 7,5% dos pacientes do sexo masculino (C3) e em 25% dos pacientes do sexo feminino (C3), e menores que 4,5 mm em 20% dos pacientes do sexo masculino (C3) e em 66% dos pacientes do sexo feminino (C3). A confiabilidade intra e interobservador foram muito boas para a medida tomográfica da EP, e boa para a AP. Para o CPA, a confiabilidade intraobservador foi boa, porém a confiabilidade interobservador variou de moderada a boa. Considerando o APT e APS, a confiabilidade intraobservador foi boa, mas a confiabilidade interobservador moderada para o APT e fraca para o APS. As medidas do DPE evidenciaram fraca confiabilidade intraobservador e fraca ou moderada confiabilidade interobservador. Nossos resultados apresentaram tendência similar aos de estudos prévios, no entanto a frequência de pacientes com a EP < 4,5 mm em nossa população é maior, sugerindo um risco aumentado durante a tentativa de realizar a técnica transpedicular / Pedicular screw insertion is a technically challenged surgical procedure. Thus, extensive knowledge of the morphology of the cervical vertebra, primarily the pedicle, is crucial to reduce severe damage to neurovascular structures. The goal of this study was to conduct a detailed computed tomography (CT) assessment in the Brazilian population of the screw starting point, trajectory, and dimensions of pedicle in the cervical spine. Two hundred consecutive patients were retrospectively evaluated using cervical spine CT, with imaging reconstruction of each cervical vertebra in the axial plane with 2mm, and in sagittal reconstructions with 3mm. Parameters in axial plane included the pedicle width (PW), pedicle axis length (PAL), pedicle transverse angle (PTA), and the distance from the entry point to the point between the lamina and spinous process (DEP). Measurements in the sagittal plane involved the pedicle height (PH) and the pedicle sagittal angle (PSA). The mean PW and PH were smaller in females than in males in all cervical vertebrae, but there were no significant differences of PTA among genders. PSA ranged from 15.2° to 23.7°. Mean values of PAL and DEP had a tendency to decrease from the proximal to distal cervical vertebrae. PW was <4 mm in 7.5% of men (C3) and 25% of women (C3), and <4.5 mm in 20% (C3 male) and 66% (C3 female). The intra- and inter-observer reliability were very good for the tomographic measurement of PW, and good for PH. For PAL, the intraobserver reliability was good, but the interobserver reliability varied from moderate to good. Considering PTA and PSA, the intraobserver reliability was good, but the interobserver reliability moderate for PTA and poor or fair for PSA. DEP measurements showed poor intraobserver reliability, and poor or moderate interobserver reliability. Our results presented similar trend of previous studies, but the frequency of patients with PW <4.5 mm in our population is higher, suggesting an increased risk during the attempting of transpedicular screw technique
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Estudo da correlação biomecânica entre desordens oclusais e desvio de coluna no plano sagital / Study of biomechanics correlaction between oclusal disorders and spine deviation in the sagital planeBittar, Ana Elise Lobo 12 November 2007 (has links)
Este estudo avaliou biomecanicamente o efeito da força resultante, em região de coluna cervical, exercida por um aparelho odontológico ortopédico mecânico, instalado em um paciente tipo classe III de Angle, durante o período de 06 meses. Para isso, selecionou-se um paciente de 10 anos e 04 meses de idade, leucoderma, do sexo masculino, para servir de modelo para este estudo. Ao exame intra-oral foram observadas chave de molares em classe III de Angle, mordida cruzada anterior, dentição mista e arcada superior atrésica. Na avaliação radiográfica, juntamente com análises de USP, Mac Namara, Bimler e Petrovic, foram constatadas maloclusão tipo classe III e potencial de crescimento mandibular maior que maxilar. Na análise de modelos, observaram-se, discrepâncias positivas tanto no sentido transversal como ântero-posterior nas duas arcadas. Foram solicitados exames radiográficos panorâmico, tele-radiografia lateral e de coluna torácica para elaboração do diagnóstico e plano de tratamento. Após isso, foi proposta a disjunção da arcada superior através de disjuntor de Mc Namara modificado e tracionamento da maxila com máscara facial de Petit, utilizando para isso, elásticos extra-orais com tração de força média (400gf). Após o uso da máscara por 06 meses, numa média de 14 horas por dia, foram feitas novas radiografias crânio cervicais para a avaliação da nova situação. O que se pode observar, além da correção da mordida cruzada anterior (clinicamente), foi, radiograficamente, a flexão da coluna do paciente com uma extensão compensatória do crânio e encurtamento de alguns músculos extensores da coluna cervical, analisados em seus marcos ósseos de origem e inserção. / This study has evaluated biomechanicaly the effect of the resultant strength at the cervical column developed by an odonthologic orthopedical mechanic appliance installed in a class III of Angle patient during 6 months. The model for this study is a 10 years and 4 months old patient, during six months. The model for this study is a 10 years and 4 months old patient, male and white. By the intra-oral exam it was possible to observe that the patient had molars in class III of Angle, previous crossed bite, mixed teething and the superior arcade is atresical. By the radiographic evaluation with analysis from USP, Mac Namara, Bimler e Petrovic, was detected a malocclusion class III and a potential of bigger mandibular growth then jaw. By the model analysis, a positive differences in the transversal as well as in the antero-posterior region of both arcades. Panoramic radiological exams, lateral and thoracic vertebral column teleradiografic exams were done in order to elaborate a diagnosis and a treatment plan. Afterwards a disjunction from the superior arcade through a modified disjunctor was proposed and a maxilla tracking through a Petit facial mask, with intra oral gummy strings with a medium strength force (400gf). After using this mask for 6 months, about 14 hours a day, other cranial-cervical x rays were done to evaluate the new results. It\'s possible to observe that not only the crossed bite was corrected (clinically) but also the cervical column flexion from the patient with a compensatory cranial extension. A shortening of some extensor muscles of cervical column, analyzed in its osseous marks of origin and insertion, was also observed.
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Form and function of the primate cervical vertebral columnJanuary 2019 (has links)
abstract: As the junction between the head and the trunk, the neck functions in providing head stability during behaviors like feeding to facilitating head mobility during behavior like grooming and predator vigilance. Despite its importance to these vital behaviors, its form and function remain poorly understood. Fossil hominin cervical vertebrae preserve a striking diversity in form despite the commitment to orthograde bipedality. Do these differences in cervical vertebral form correspond to functional variations among our recent ancestors? This dissertation attempts to understand 1) how does the neck function in head stability and mobility 2) how do these functions relate to cervical vertebral form. Kinematic and passive range of motion studies were conducted in several species of primate to obtain measures of function which were subsequently related to skeletal form.
Results show that cervical vertebral morphology does not significantly covary with differences in joint mobility. Rather, they implicate the critical role of ligaments and muscles in facilitating head mobility. Results of the kinematics study show that the neck plays a role in maintaining head stability during locomotion. However, the kinematic data do not significantly correlate with morphological variation among primate species. Given the negative results of the extant morphological analyses, it is difficult to apply them to the fossil record. As such, the functional significance of the disparate morphologies found in the hominin fossil record remain ambiguous. / Dissertation/Thesis / Doctoral Dissertation Anthropology 2019
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Biomechanical effects of multi-level laminoplasty and laminectomy: an experimental and finite element investigationKode, Swathi 01 December 2011 (has links)
Cervical spondylotic myelopathy is the most common spinal cord disorder in persons over 55 years of age in North America and perhaps in the world. Surgical options are broadly classified into two categories namely, anterior and posterior approaches. This study focuses on the posterior based approach (i.e. laminectomy or laminoplasty) which is considered when multiple levels of the spine have to be decompressed or when most of the cord compression results from posterior pathological conditions. The external and internal behavior of the spine after laminoplasty and laminectomy has been evaluated using both experimental and computational methods. Computationally, a validated intact 3D finite element model of the cervical spine (C2-T1) was modified to simulate laminectomy and laminoplasty (open door (ODL) and double door (DDL)) at levels C3-C6. During flexion, after ODL the adjacent levels C2-C3 and C6-C7 showed a 39% and 20% increase in the motion respectively; while no substantial changes were observed at the surgically altered levels. The percent increase in motion after DDL varied from 4.3% to 34.6%. The inclination towards increased motion during flexion after double door laminoplasty explains the role of the lamina-ligamentum flavum complex in the stability of spine. Compared to the intact model, laminectomy at C3-C6 led to a profound increase (37.5% to 79.6%) in motion across the levels C2-C3 to C6-C7. Furthermore, the changes in the von Mises stresses of the intervertebral disc observed after laminoplasty and laminectomy during flexion can be correlated to the changes in the intersegmental motions.
An in-vitro biomechanical study was conducted to address the effects of laminoplasty (two-level and four-level) and four-level laminectomy on the flexibility of the cervical spine. Both two-level and four-level laminoplasty resulted in minimal changes in C2-T1 range of motion. For flexion/extension, two-level and multi-level laminoplasty showed an approximate 20% decrease (p>0.05) in the range of motion at C4-C5 and C2-C3 respectively due to the encroachment of the spinous process into the opened lamina. The decrease was mostly observed in older specimens and specimens with adjacent laminae close to each other; thus leading to the encroachment of the spinous process into the opened lamina. Laminectomy resulted in a statistically significant (p<0.05) increase in the range of motion compared to the intact condition during the three loading modes. These results correspond well with the finite element predictions, where a four-level ODL and laminectomy resulted in a minimal 5.4% and a substantial 57.5% increase in C2-T1 motion respectively during flexion. Adaptive bone remodeling theory was applied to the open door laminoplasty model to understand the effect of the surgical procedure on the internal architecture of bone. Bone remodeling was implemented at the C5 vertebra by quantifying the changes in apparent bone density in terms of the mechanical stimulus (i.e. SED/density). After laminoplasty, the increased load distribution through the bony hinge region led to the increased bone density during extension. This increased bone density could eventually lead to bone formation in those regions through external remodeling.
The current study proved laminoplasty to be a motion preservation technique wherein the plates and spacer provided additional stability via reconstruction of the laminar arch while laminectomy can cause instability of spine especially during flexion. In the future, patient-specific finite element models that incorporate geometry-related differences could be developed to optimize the number of operated levels and to further explain the effect of surgical procedure on the unaltered levels.
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Cervical Total Level Arthroplasty System With PEEK All-Polymer ArticulationsLangohr, Gordon Daniel George January 2011 (has links)
The cervical spine must provide structural support for the head, allow large range of motion and protect both the spinal cord and branching nerves. There are two types of spinal joints: the intervertebral discs which are flexible connections and the facets, which are articulating synovial joints. Both types degenerate with age. Current surgical treatments include spinal fusion and articulating disc replacement implants. If both disc and facet joints are degenerated, fusion is the only option. In spinal fusion, the disc is removed and the adjacent vertebrae are fused which causes abnormally high stress levels in adjacent discs. In disc replacement, an articulating device is inserted to restore intervertebral motion and mimic healthy spinal kinematics. Disc arthroplasty does not significantly increase adjacent level stress but the lack of rotational constraint causes increased facet contact pressures. Thus, there is a need for a cervical total level arthroplasty system (CTLAS) that has a disc implant specifically designed to preserve the facet joints and implants for facet arthroplasty that can act independently or in-unison with the disc replacement.
The conceptual design of a CTLAS implant system was proposed that would replace the disc and the facet joints. To facilitate medical imaging, PEEK (polyetheretherkeytone) was selected as the structural and bearing material. In the present thesis, multi-station pin-on-plate wear testing was initiated for pairs of unfilled (OPT) and carbon-fiber-reinforced (CFR) PEEK. Wear is important in arthroplasty implant design because wear particles can cause osteolysis leading to loosening. A variety of experiments were performed to investigate the effects of load, contact geometry and lubricant composition on wear. CFR PEEK was found to have much lower and more predictable wear than OPT PEEK in the present experiments. The wear of OPT PEEK pairs showed sensitivity to lubricant protein concentration. The coefficient of friction during testing was found to be quite high (up to 0.5), which might have clinical implications. Also, some subsurface fatigue was found, exposing carbon fibers of CFR PEEK. This remains a concern for its long-term application. Further wear testing is recommended using actual implants in a spine wear simulator.
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Strain Rate Dependent Properties of Younger Human Cervical Spine LigamentsMattucci, Stephen January 2011 (has links)
The cervical spine ligaments play an essential role in limiting the physiological ranges of motion in the neck; however, traumatic loading such as that experienced in automotive crash scenarios can lead to ligament damage and result in neck injury. The development of detailed finite element models for injury simulation requires accurate ligament mechanical properties at relevant loading rates.
The objective of this research was to provide detailed mechanical properties for the cervical spine ligaments, by performing tensile tests at elongation rates relevant to automobile crash scenarios, using younger specimens (less than 50 years old), and to provide a comprehensive investigation of spinal level and gender effects.
The five primary ligaments (present between C2-T1) investigated were: the anterior longitudinal ligament, posterior longitudinal ligament, capsular ligament, ligamentum flavum, and interspinous ligament. The craniovertebral ligaments (Skull/C0-C2) investigated were the tectorial membrane/vertical cruciate/apical/alar ligament complex, transverse ligament, anterior atlanto-occipital membrane, posterior atlanto-occipital membrane, anterior atlanto-axial membrane, and posterior atlanto-axial membrane. Tests were performed within an environmental chamber designed to mimic in vivo temperature and humidity conditions, and specimens were preconditioned for 20 cycles at 10% strain prior to testing to failure. Ligaments were tested at quasi-static (0.5s-1), medium (20s-1) and high (150-250s-1). These strain rates were predicted by an existing cervical spine finite element model under typical crash scenarios.
Two hundred sixty-one total primary ligament tests were performed, with approximately even distribution within elongation rate, spinal level, and gender. Another forty-four craniovertebral ligaments were tested. Results were plotted as force-displacement curves and the response characteristics determined from the curves were: failure force, failure elongation, stiffness of the linear region, toe region elongation, failure stress, failure strain, modulus and toe region strain. The measured force-displacement data followed expected trends when compared with previous studies. The younger ligaments had less scatter, and were both stiffer and stronger than the older specimens that were reported in previous studies at both quasi-static and comparable higher elongation rates.
Statistical analysis was performed on the results to establish significant effects. Strain rate effects were most significant whereas spinal level effects were not found. In general, gender effects were not found to be significantly different, but consistent trends were identified with male ligaments having a higher stiffness and failure force than female ligaments. The post-ultimate load region of the curves was reported to offer insight into the ligament failure mechanism.
The characteristic values obtained were used to develop average curves for each ligament, with the intention to eventually be directly integrated into finite element models to better represent the ligament structures. Curves were developed to incorporate the strain rate, spinal level and gender effects for each ligament based on the statistical analyses. Post-failure response was incorporated into these curves because this region has been shown to have an effect on neck behaviour in mathematical models.
Recommendations for future studies include measuring accurate cross sectional areas of ligaments during tensile testing to obtain true stress and true strain measurements to better understand if differences in mechanical properties are structural or material. Other possible improvements would be further testing of young cervical spine ligaments with larger sample sizes to further explore spinal level and gender effects. Additional testing performed under identical testing conditions as the current study would allow for pooling of the results effectively increasing the sample size.
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