The effect of position on the lumbar intervertebral disc.

This thesis comprises three phases with a combined aim which was to investigate the effect of position on the lumbar intervertebral disc (IVD). The effect of position on the lumbar IVD in asymptomatic subjects and subjects with discogenic low back pain (DLBP) was explored using positional Magnetic Resonance Imaging (pMRI). Convenience samples of 11 asymptomatic and 34 DLBP subjects were recruited to have sagittal and axial pMRI scans performed in sitting (Neutral, Flexed and Extended), standing and lying (Supine and Prone extension) positions. The sagittal plane migration of the nucleus pulposus (NP) of each lumbar IVD in each position was measured from the sagittal and axial pMRI scans. Within and between group inferential analysis was performed using nonparametric tests. Both the asymptomatic and DLBP subjects demonstrated that position had statistically significant effects on the sagittal plane NP migration. Both groups demonstrated significantly greater posterior sagittal plane NP migration in Neutral and Flexed sitting positions compared to the other positions. However, between group comparisons identified that the asymptomatic subjects also demonstrated significantly greater posterior sagittal plane NP migration than the DLBP subjects. This pattern was more common in the upper lumbar IVDs (L1/2 and L2/3) between positions and less common in the lower IVDs (L4/5 and L5/S1) between positions. New knowledge regarding the behaviour of the lumbar IVD emerged from this research. The differences detected between the asymptomatic and DLBP subjects suggest that some current theories regarding DLBP may be incorrect. The results also support imaging of DLBP subjects in sitting positions as opposed to current supine positions. Although the limitations of the study reduce generalisation of the results, the implications for clinical practice, imaging and suggestions for further research from this work are important to improve understanding and conservative management of DLBP

Understanding the Role of Personal, Psychosocial and Occupational Factors and their Interactions on Low Back Pain Severity in Workers

Low back pain (LBP) is the most prevalent work-related musculoskeletal disorder. Occupational risk factors have been studied for current ergonomic prevention strategies; however, other underlying mechanisms may exist since not all workers performing the same task develop the same severity. Previous research has identified personal and psychosocial risk factors that also contribute to LBP. Research quantifying the interactive effects of the various personal, psychosocial and occupational factors is limited, along with research on the effect of risk factor combinations on LBP severity. The objectives of this study were to: 1) study the various factors that are known to be involved in low back pain and analyze interactions, and 2) develop a model to predict low back pain and validate it. In order to address these objectives, 2 studies were conducted. The first study investigated the effects of various personal, genetic, occupational and psychosocial factors on two subjective LBP severity ratings: Oswestry Disability Index (ODI) and a Visual Analog Scale (VAS), and three physician-based ratings: MRI severity, canal stenosis and nerve impingement. Personal and psychosocial factors, in addition to occupational factors, were found to significantly affect the severity ratings. The second study involved building predictive models of LBP severity for each risk factor category as well as a combined risk factor model. Results showed that the combined risk factor models considering interaction effects both within and across risk factor categories were significantly better in predicting severity ratings than the individual models. However, validation conducted using 5 random samples showed inconsistent accuracies. Results obtained may help to develop a more reliable way to predict and, hence, prevent chronic LBP

Understanding the Role of Personal, Psychosocial and Occupational Factors and their Interactions on Low Back Pain Severity in Workers

Low back pain (LBP) is the most prevalent work-related musculoskeletal disorder. Occupational risk factors have been studied for current ergonomic prevention strategies; however, other underlying mechanisms may exist since not all workers performing the same task develop the same severity. Previous research has identified personal and psychosocial risk factors that also contribute to LBP. Research quantifying the interactive effects of the various personal, psychosocial and occupational factors is limited, along with research on the effect of risk factor combinations on LBP severity. The objectives of this study were to: 1) study the various factors that are known to be involved in low back pain and analyze interactions, and 2) develop a model to predict low back pain and validate it. In order to address these objectives, 2 studies were conducted. The first study investigated the effects of various personal, genetic, occupational and psychosocial factors on two subjective LBP severity ratings: Oswestry Disability Index (ODI) and a Visual Analog Scale (VAS), and three physician-based ratings: MRI severity, canal stenosis and nerve impingement. Personal and psychosocial factors, in addition to occupational factors, were found to significantly affect the severity ratings. The second study involved building predictive models of LBP severity for each risk factor category as well as a combined risk factor model. Results showed that the combined risk factor models considering interaction effects both within and across risk factor categories were significantly better in predicting severity ratings than the individual models. However, validation conducted using 5 random samples showed inconsistent accuracies. Results obtained may help to develop a more reliable way to predict and, hence, prevent chronic LBP

Procedures for finite element mesh generation from medical imaging: application to the intervertebral disc

Dissertação de mestrado integrado em Engenharia BiomédicaThe paramount goal of this ‘half-year’ work is the development of a set of methodologies and procedures for the geometric modelling by a finite element (FE) mesh of the bio-structure of a motion segment (or functional spinal unit), i.e., two vertebrae and an intervertebral disc, from segmented medical images (processed from medical imaging). At an initial stage, a three-dimensional voxel-based geometric model of a goat motion segment was created from magnetic resonance imaging (MRI) data. An imaging processing software (ScanIP/Simplewire) was used for imaging segmentation (identification of different structures and tissues), both in images with lower (normal MRI) and higher (micro-MRI) resolutions. It shall be noticed that some soft-tissues, such as annulus fibrosus or nucleus pulposus, are very hard to isolate and identify given that the interface between them is not clearly defined. At the end of this stage, images with different resolutions allowed to generate different 3D voxel-based geometric models. Thereafter, a procedure for the FE mesh generation from the aforementioned voxelized data should be studied and applied. However, as the original geometry was only approximately known from real medical imaging, it was difficult to objectively quantify the quality of the FE meshing procedure and the accuracy between source geometry and target FE mesh. In order to overcome such difficulties, and due to the lack of quality of the available medical imaging, a “virtualization” procedure was developed to create a set of segmented 2D medical images from a well-defined geometry of a motion segment. The main idea was to create the conditions to quantify the quality and the accuracy of the developed FE meshing procedure, as well to study the effect of imaging resolution. Starting from the virtually generated 2D segmented images, a 3D voxel-based structure was achieved. Given that initial domains are now clearly defined, there is no need for further image processing. Then, a two-step FE mesh generation procedure (generation followed by simplification) allows to create an optimized tetrahedral FE mesh directly from 3D voxelized data. Finally, because the virtualization procedure allowed to know the initial geometry, one is able to objectively quantify the quality and the accuracy of the final simplified tetrahedral FE mesh, and thus to understand and quantify: a) the role of the medical image resolution on the FE geometrical reconstruction, b) the procedure and parameters of the FE mesh generation step, and c) the procedure and parameters of the FE mesh simplification step, and thus to give a clear contribution in the definition of the procedure for the FE mesh generation from medical imaging in case of an intervertebral disc.O objetivo fundamental deste trabalho de seis meses é o desenvolvimento de um conjunto de metodologias e procedimentos para a modelação geométrica, através de uma malha de elementos finitos (EF) de uma bio-estrutura de um motion segment (ou unidade funcional da coluna), ou seja, duas vértebras e um disco intervertebral, a partir de imagens médicas segmentadas (processadas a partir de imagiologia médica). Numa fase inicial, um modelo geométrico tridimensional baseado em voxels de um motion segment de uma cabra foi criado a partir de informação de imagens médicas de ressonância magnética (RM). Um software de processamento de imagem (ScanIp/Simplewire) foi usado para segmentação de imagens (identificação de diferentes estruturas e tecidos), em imagens de menor (RM normal) e maior (micro-RM) resolução. Deve ser referido que alguns tecidos moles, como o anel fibroso e o núcleo pulposo são muito difíceis de isolar e identificar, dado que as fronteiras destes não estão claramente definidas. No final desta etapa, as imagens com diferentes resoluções permitiram gerar diferentes modelos geométricos 3D baseados em voxels. Posteriormente, um procedimento para geração de malha de EF, a partir da informação voxelizada acima mencionada, deveria ser estudado e aplicado. No entanto, como a geometria original era aproximadamente conhecida a partir de imagens médicas reais, foi difícil quantificar objetivamente a qualidade do procedimento de geração de malha de EF e a precisão entre a geometria de origem e a malha de EF de destino. A fim de superar tais dificuldades, e devido à falta de qualidade de imagens médicas disponíveis, um procedimento de “virtualização” foi desenvolvido para criar um conjunto de imagens médicas 2D segmentadas a partir de uma geometria de um motion segment bem conhecida. A principal ideia foi criar as condições para quantificar a qualidade e a precisão do procedimento de geração de malha de EF desenvolvido, bem como estudar o efeito da resolução da imagem médica. A partir das imagens 2D segmentadas, geradas virtualmente, uma estrutura de voxels 3D pode ser conseguida. Dado que os domínios iniciais estão agora claramente definidos, não há necessidade de processamento de imagem adicional. Por conseguinte, um procedimento de geração de malha de EF de duas etapas (geração seguida por simplificação) permite criar uma malha de EF tetraédrica otimizada diretamente a partir de informação 3D voxelizada. Por fim, como o procedimento de virtualização permitiu conhecer a geometria inicial, é possível quantificar objetivamente a qualidade e exatidão da malha de EF tetraédrica final simplificada, e assim, compreender e quantificar: a) o papel da resolução da imagem médica na reconstrução geométrica de EF; b) o procedimento e os parâmetros da etapa de geração de malha de EF; c) o procedimento e os parâmetros da etapa de simplificação de malhas de EF, e assim, dar uma contribuição clara na definição do procedimento para a geração de malha de EF a partir de imagem médica, no caso de um disco intervertebral.European Project : NP Mimetic - Biomimetic Nano-Fiber Based Nucleus Pulposus Regeneration for the Treatment of Degenerative Disc Disease, funded by the European Commission under FP7 (grant NMP3-SL-2010-246351

Low Back Pain (LBP)

Low back pain (LBP) is a major public health problem, being the most commonly reported musculoskeletal disorder (MSD) and the leading cause of compromised quality of life and work absenteeism. Indeed, LBP is the leading worldwide cause of years lost to disability, and its burden is growing alongside the increasing and aging population. The etiology, pathogenesis, and occupational risk factors of LBP are still not fully understood. It is crucial to give a stronger focus to reducing the consequences of LBP, as well as preventing its onset. Primary prevention at the occupational level remains important for highly exposed groups. Therefore, it is essential to identify which treatment options and workplace-based intervention strategies are effective in increasing participation at work and encouraging early return-to-work to reduce the consequences of LBP. The present Special Issue offers a unique opportunity to update many of the recent advances and perspectives of this health problem. A number of topics will be covered in order to attract high-quality research papers, including the following major areas: prevalence and epidemiological data, etiology, prevention, assessment and treatment approaches, and health promotion strategies for LBP. We have received a wide range of submissions, including research on the physical, psychosocial, environmental, and occupational perspectives, also focused on workplace interventions

Effects of Compression Loading, Injury, and Age on Intervertebral Disc Mechanics, Biology and Metabolism Using Large Animal Organ and Cell Culture Systems

The intervertebral disc (IVD) is a complex orthopaedic tissue that is located between the vertebrae in the spine. Degeneration of the IVD is thought to be a contributor to low back pain (LBP), which affects up to 80% of the population at enormous economic cost. The role of the intervertebral disc in supporting and resisting applied loading to the spine, along with the observation of disorders associated with abnormal spinal loading, provide support to the theory that applied mechanical loading is crucial in maintaining the health of the intervertebral disc. The encompassing goal of this work was to examine the biological response of the intervertebral disc to changes in the surrounding mechanical environment in a large animal model. Aim 1 utilized an organ culture model to explore the relationship between disc mechanics and biology in needle puncture injury, a commonly used model of experimentally induced disc degeneration, thus providing a possible mechanism for in vivo injury induced disc degeneration models. Aim 2 was to explore the interaction between the amplitude of applied mechanical loading and intervertebral disc cell signaling, also performed in an organ culture model to include cell-matrix signal transduction. Aim 3 addressed frequency and age effects on the IVD response to mechanical stimulation, performed in vitro to control for the effects of varying matrix compositions between old and young animals. Finally, Aim 4 utilized kmeans and fuzzy c-means clustering techniques to reveal patterns in experimental phenotype (determined by gene expression data) and gene response to experimental conditions. The application of biclustering, where the gene responses within experimental phenotypes are clustered to elucidate possible mechanisms for different gene level-responses to experimental conditions, was also accomplished. Finally, the ability for the model to predict the behavior of other genes critical to IVD mechanobiology, or in determining the membership of an unexamined experimental phenotype was explored. Overall, applied dynamic compression was not found to significantly alter disc mechanics, while a disruption in the annulus through needle puncture rapidly decreased the compressive modulus. Changes in disc mechanics may precede biological remodeling, with little evidence of remodeling present without mechanical alteration. Aging, however, crucially impacts disc cell biology, particularly in the nucleus pulposus, and will interact with applied loading to further impact the ability for the intervertebral disc cells to maintain a healthy extracellular matrix

Machine learning in orthopedics: a literature review

In this paper we present the findings of a systematic literature review covering the articles published in the last two decades in which the authors described the application of a machine learning technique and method to an orthopedic problem or purpose. By searching both in the Scopus and Medline databases, we retrieved, screened and analyzed the content of 70 journal articles, and coded these resources following an iterative method within a Grounded Theory approach. We report the survey findings by outlining the articles\u2019 content in terms of the main machine learning techniques mentioned therein, the orthopedic application domains, the source data and the quality of their predictive performance