Back pain is a common complaint and the origin of this frequently attributed to degenerative disc disease. In the most severe cases, the integrity of the disc and surrounding tissue is lost to such an extent that surgical intervention is necessary. Fusion procedures are commonly used to treat severely degenerated discs. Yet this is known to alter the biomechanics of the operated level, and may create a progression of degenerative decline. Total disc replacement has emerged as a viable treatment but the complexity of the spine is reflected in the clinical results, which trail far behind the success of hip and knee arthroplasty. This may be due to a failure of total disc replacement procedures to restore the natural biomechanics of the spine. The present study has led to the development of a dynamic pre-clinical testing protocol to quantitatively assess the efficacy of disc replacement devices. A six-axis spine simulator was designed and built, and the stiffness matrix testing of porcine lumbar specimens was completed, both with and without an axial preload. Intact specimens were tested, and the testing repeated after a total disc replacement procedure with a DePuy In Motion artificial disc. This is the first study to complete dynamic six-axis spinal testing of this kind. The testing demonstrated the disc replacement device compared favourably with the intact porcine disc both in shear and axial stiffness. However, the low-friction, double ball and socket design of the In Motion device lacks stiffness in the three rotational axes, and it is unstable in lateral bending. Rotations are the primary movements in the spine, and it is crucial if the natural biomechanics are to be restored, that a disc replacement device should replicate the stiffnesses of these axes. The next generation of disc replacement devices feature elastomeric materials that may more closely replicate the natural intervertebral disc. From patents registered with DePuy, this may also be true of the next generation of In Motion disc. This research provides a means to complete standardised performance tests of new spinal devices and lays the foundations for future comparison studies. Additionally, the spine simulator and testing protocol would provide valuable data during the design stage of new total disc replacements, aiding the development of the next generation of artificial discs.

No description available.

Low back pain is a costly financial and loss of productivity societal issue. Although its aetiology is unclear, it has been associated with the intervertebral disc and its degeneration which has been thought to be caused in part by poor nutrition. In this thesis the caudal disc of skeletally mature equines is utilised as an animal model. Techniques such as x-ray, light imaging, histology and magnetic resonance imaging were employed to investigate the vascular and structural anatomy of the disc and its surroundings and the uptake of tracers within the disc tissue. A detailed study of the anatomy revealed similarities with the human disc. The equine disc consists of two distinct structural areas; a nucleus and annulus. The surrounding vascularisation is similar; a main anteriorly positioned artery, the median caudal artery splits and encircles the centre of the vertebral body providing nutrition to the vertebral body. Smaller vessels anastomose over the surface of the vertebral body. Within the vertebral body the vessels end in capillary terminations at the edge of the vertebral cartilage endplate. As in humans these terminations were seen to vary along the endplate with shape and density; the capillaries are densest and larger in the area next to the nucleus. The cartilage endplate itself was found to have a variable width; of between 0.16 mm and 0.33 mm being widest at the nucleus. The annulus was seen to consist of lamellar rings which had high collagen content. A marked difference between equines and humans found was the number and width of lamellae present; equines were found to have on average 5 lamellae with a width range of 140 10 1110 microns. The shape of the discs was also found to be different with equines having almost circular coccygeal discs which have a concave superior and inferior surface. The nucleus of the disc, unlike current literature was found to have local order. An important contribution to knowledge which this thesis has made is data collected on diffusion time and partition coefficient on many regions within the disc. It was found that to reach equilibrium it took up to 22 hours in the outer anterior annulus but only 5 ½ hours in the central nucleus. Diffusion was found to be fastest with the neutral ring-shaped molecule Gadovist and slowest in the positive ion, manganese. Partition coefficients between the tracers were also found to vary. The highest partition coefficient was 6 in the central nucleus with manganese and the lowest was 0.5 with Magnevist at 0.5 in the nucleus area. This information will be useful in aiding drug delivery clinically and performing contrast enhanced imaging for pathology detection.

Low back pain is highly prevalent in the developed world, with 80% of the population being affected at some point in their lives. Herniation, a common injury to the intervertebral disc, is characterized as the posterior migration of the nucleus pulposus through the layers of the annulus fibrosus. Various risk factors have been associated with the development of disc herniation, but the mechanisms are largely not understood. For example, exposure to vibration has been linked to the occurrence of herniation, yet our understanding of this association is not clear. It is hypothesized that vibration cyclically loads the tissues of the intervertebral disc until failure occurs as a result of fatigue. Tissues at risk of fatigue failure may include the intra-lamellar matrix, the connective tissue found between collagen fibres within a single lamella, and the inter-lamellar matrix, the connective tissue found between adjacent lamellae. In order to determine the mechanistic link between vibration and herniation, a firm understanding of the properties of the intervertebral disc as well as the intra and inter-lamellar matrices are of utmost importance. Further, it is important to determine these properties under physiological loading scenarios. This thesis consists of five studies, which have each provided a unique piece to the intervertebral disc herniation puzzle in order to better understand this mechanistic link. First, it was discovered that annular tissue is subject to significantly higher stresses and is stiffer under biaxial strain as compared to uniaxial strain. Biaxial strain is more representative of the in vivo loading scenario and provides more accurate information regarding scenarios that the annulus can tolerate and those that can result in injury. It was also revealed that, when strained at physiological strain rates (up to 4%/sec), these mechanical properties do not change such that they are independent of strain rate. Therefore, when strained at varying rates akin to voluntary movement, the annulus is not subject to higher stresses or altered stiffness. Second, the effect of vibration, an acknowledged risk factor for herniation, was examined on the mechanical properties of the intra and inter-lamellar matrices. It was discovered that vibration altered these matrices such that they were more extensible and strained to greater magnitudes, yet did not reach higher stresses before failing. It was hypothesized that this increased extensibility was due to damage to elastin, as elastin assists in minimizing tissue deformation and helps tissues recover from tensile strain. The final study assessed the effect of exposure to vibration on the development of disc herniation. The initiation of herniation was observed in a significantly greater number of intervertebral discs exposed to vibration as compared to a control condition. Although epidemiological studies had documented a correlation between exposure to vibration and herniation, this was the first study to conclude that exposure to vibration is in fact a mechanical risk factor for the development of herniation and increases the incidence of herniation. Further, based on the findings of the mechanical properties of the intra and inter-lamellar matrices, and in particular the observed 15-20 times greater failure strength of the intra as compared to inter-lamellar matrix, it would appear that the inter-lamellar matrix, and thus delamination, may be the weakest link in the herniation pathway. This thesis has uncovered new information regarding physiological mechanical properties of the annulus. Further, new information regarding the intra and inter-lamellar matrices was obtained, improving our understanding of the healthy disc. Last, by subjecting the disc to a known risk factor for herniation, hypotheses were generated regarding the initiation and progression of disc herniation, specifically related to the roles of the intra and inter-lamellar matrices.

Low back pain is highly prevalent in the developed world, with 80% of the population being affected at some point in their lives. Herniation, a common injury to the intervertebral disc, is characterized as the posterior migration of the nucleus pulposus through the layers of the annulus fibrosus. Various risk factors have been associated with the development of disc herniation, but the mechanisms are largely not understood. For example, exposure to vibration has been linked to the occurrence of herniation, yet our understanding of this association is not clear. It is hypothesized that vibration cyclically loads the tissues of the intervertebral disc until failure occurs as a result of fatigue. Tissues at risk of fatigue failure may include the intra-lamellar matrix, the connective tissue found between collagen fibres within a single lamella, and the inter-lamellar matrix, the connective tissue found between adjacent lamellae. In order to determine the mechanistic link between vibration and herniation, a firm understanding of the properties of the intervertebral disc as well as the intra and inter-lamellar matrices are of utmost importance. Further, it is important to determine these properties under physiological loading scenarios. This thesis consists of five studies, which have each provided a unique piece to the intervertebral disc herniation puzzle in order to better understand this mechanistic link. First, it was discovered that annular tissue is subject to significantly higher stresses and is stiffer under biaxial strain as compared to uniaxial strain. Biaxial strain is more representative of the in vivo loading scenario and provides more accurate information regarding scenarios that the annulus can tolerate and those that can result in injury. It was also revealed that, when strained at physiological strain rates (up to 4%/sec), these mechanical properties do not change such that they are independent of strain rate. Therefore, when strained at varying rates akin to voluntary movement, the annulus is not subject to higher stresses or altered stiffness. Second, the effect of vibration, an acknowledged risk factor for herniation, was examined on the mechanical properties of the intra and inter-lamellar matrices. It was discovered that vibration altered these matrices such that they were more extensible and strained to greater magnitudes, yet did not reach higher stresses before failing. It was hypothesized that this increased extensibility was due to damage to elastin, as elastin assists in minimizing tissue deformation and helps tissues recover from tensile strain. The final study assessed the effect of exposure to vibration on the development of disc herniation. The initiation of herniation was observed in a significantly greater number of intervertebral discs exposed to vibration as compared to a control condition. Although epidemiological studies had documented a correlation between exposure to vibration and herniation, this was the first study to conclude that exposure to vibration is in fact a mechanical risk factor for the development of herniation and increases the incidence of herniation. Further, based on the findings of the mechanical properties of the intra and inter-lamellar matrices, and in particular the observed 15-20 times greater failure strength of the intra as compared to inter-lamellar matrix, it would appear that the inter-lamellar matrix, and thus delamination, may be the weakest link in the herniation pathway. This thesis has uncovered new information regarding physiological mechanical properties of the annulus. Further, new information regarding the intra and inter-lamellar matrices was obtained, improving our understanding of the healthy disc. Last, by subjecting the disc to a known risk factor for herniation, hypotheses were generated regarding the initiation and progression of disc herniation, specifically related to the roles of the intra and inter-lamellar matrices.

Made available in DSpace on 2014-06-11T19:34:57Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-22Bitstream added on 2014-06-13T21:06:51Z : No. of bitstreams: 1 lemos_ff_dr_guara_parcial.pdf: 67760 bytes, checksum: 8abbb6c32f12d888cf49226d69fd138e (MD5) Bitstreams deleted on 2014-10-03T16:24:39Z: lemos_ff_dr_guara_parcial.pdf,Bitstream added on 2014-10-03T16:27:37Z : No. of bitstreams: 2 lemos_ff_dr_guara_parcial.pdf.txt: 11034 bytes, checksum: 59c288b2b373bbe58255effddd89bb52 (MD5) 000671151.pdf: 2407167 bytes, checksum: 0e13b6a8dfac5d68060ec4460476f509 (MD5) Bitstreams deleted on 2014-10-03T16:33:14Z: 000671151.pdf,Bitstream added on 2014-10-03T16:43:28Z : No. of bitstreams: 2 lemos_ff_dr_guara_parcial.pdf.txt: 11034 bytes, checksum: 59c288b2b373bbe58255effddd89bb52 (MD5) 000671151.pdf: 2407167 bytes, checksum: 0e13b6a8dfac5d68060ec4460476f509 (MD5) Bitstreams deleted on 2014-10-03T16:48:54Z: 000671151.pdf,Bitstream added on 2014-10-03T16:49:46Z : No. of bitstreams: 1 000671151.pdf: 2407167 bytes, checksum: 0e13b6a8dfac5d68060ec4460476f509 (MD5) Bitstreams deleted on 2014-10-27T11:47:07Z: 000671151.pdf,Bitstream added on 2014-10-27T11:48:04Z : No. of bitstreams: 1 000671151.pdf: 2407167 bytes, checksum: 0e13b6a8dfac5d68060ec4460476f509 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A desidratação do núcleo pulposo que, juntamente com o anulus fibroso, compõe o disco intervertebral, participa do processo de degeneração da coluna vertebral. Torna-se importante entender como este processo de desidratação e a consequente alteração das propriedades mecânicas influenciam na biomecânica dessa articulação. O principal objetivo deste estudo é analisar a influência da desidratação no coeficiente de amortecimento viscoso e como esta variação pode alterar o comportamento mecânico do disco intervertebral lombar. Este estudo é composto de duas etapas: na primeira, o coeficiente de amortecimento viscoso foi obtido experimentalmente de unidades funcionais de colunas lombares suínas antes e após o processo de desidratação das mesmas; na segunda, foi simulado em modelo computacional a resposta harmônica, utilizando-se dados da literatura e do coeficiente de amortecimento viscoso, analisando as diferenças entre uma simulação com o disco intervertebral hidratado e desidratado. O coeficiente de amortecimento viscoso hidratado (4,7) e desidratado (2,7) apresentou diferença estatisticamente significante (p<0,001). Na simulação computacional podese evidenciar uma menor influência da variação do coeficiente de amortecimento viscoso quando analisado de forma isolada do que quando analisado em conjunto com variações nos dados referentes à rigidez, principalmente nas frequências de ressonância e nas amplitudes de pressão intradiscal e deformação do disco intervertebral. Concluiu-se que discos intervertebrais desidratados respondem de forma diferente à vibração, o que pode contribuir para os processos lesivos da coluna vertebral / The dehydration of the nucleus pulposus which, with the anulus fibrosus, composes the intervertebral disc, participates in the process of degeneration of the spine. It is important to understand how this process and the consequent alteration of dehydration of the mechanical properties influence the biomechanics of this joint. The aim of this study is to analyze the influence of dehydration in the viscous damping coefficient and how this variation can change the mechanical behavior of lumbar intervertebral disc. This study consists of two stages: first, the viscous damping coefficient was obtained experimentally in functional units of porcine lumbar spine before and after the dehydration process of them; second, an harmonic response was simulated in a computer model, using literature data and the viscous damping coefficient, analyzing the differences between a simulation with the hydrated and dehydrated intervertebral disc. The hydrated (4.7) and dehydrated (2.7) viscous damping coefficient showed a statistically significant difference (p <0.001). In the computer simulation, a lower influence of variation of the viscous damping coefficient can be detected when analyzed separately than when analyzed together with variation on stiffness data, especially in the resonance frequencies and in the amplitudes of the intradiscal pressure and deformation of the intervertebral disc. We conclude that dehydrated intervertebral discs respond differently to vibration, what can contribute to the damaging processes of the spine

Abstract Genetic factors have been implicated to play a role in both degenerative lumbar spinal stenosis (LSS) and intervertebral disc disease (IDD). Sequence variations in the genes coding for collagen IX and inflammatory mediators have been indicated as risk factors for IDD. Nine genes coding for intervertebral disc (IVD) collagens I, II, IX and XI and aggrecan (AGC1) were analyzed for sequence variations in 29 Finnish individuals with LSS. In addition, two polymorphisms in the vitamin D receptor gene and one in the matrix metalloproteinase-3 gene were studied. Study subjects were analyzed both clinically and radiologically. Results indicated an association between the COL11A2 IVS6-4 a to t polymorphism and LSS (p = 0.0016). Moreover, the t/t genotype was found more often in the patient group compared to controls (p = 0.0011). A novel splicing mutation, likely resulting in the synthesis of a truncated protein, was identified in COL9A2. Eight hundred four Chinese individuals were screened for the presence of the Trp2 and Trp3 alleles. The Trp2 allele was found in 20% of the individuals compared to the previously reported 5% in Finnish patients with IDD characterized by sciatica. The Trp2 allele was found to predispose to IVD degeneration and end plate herniations, increasing the risk by 2.4-fold from 40 to 49 years of age. In addition, the degeneration was worse in individuals with the Trp2 allele. The risk for annular tears was 4-fold greater in study subjects from 30 to 39 years of age who were Trp2 positive. Surprisingly, the Trp3 allele was absent even though it was found in about 9% of Finnish individuals. One hundred fifty-five Finnish individuals with IDD characterized by sciatica were analyzed for sequence variations in four genes coding for inflammatory mediators IL1A, IL1B, IL6, and TNFA. In addition, sixteen polymorphisms in inflammatory mediator genes were analyzed. The results identified an association between sciatica and the E5+15T>A polymorphism in IL6 (p = 0.007). A significant association was also seen in the IL6 haplotype analysis (-597 g>a, -572 g>c, -174 g>c and E5+15T>A). The association of the GGGA haplotype with the disease was highly significant (p = 0.0033).

Abstract Genetic factors have been shown to have an important role in intervertebral disc disease. The associations of known genetic risk factors and whole-body vibration, a proposed environmental risk factor, for intervertebral disc disease (IDD) were evaluated. Eleven variations in eight genes (COL9A2, COL9A3, COL11A2, IL1A, IL1B, IL6, MMP-3 and VDR) were genotyped in 150 male train engineers with an average of 21-year exposure to whole-body vibration and 61 male paper mill workers with no occupational exposure to vibration. The number of individuals belonging to the IDD group was significantly higher among train engineers (42% of train engineers vs. 17.5% of sedentary workers; p = 0.005). In addition, the IL1A-889T allele represented a risk factor for the IDD-phenotype. In order to clarify the role of genetic variations in the genes coding for several proinflammatory mediators, hundred fifty-five Finnish individuals with IDD were analyzed for mutations in the genes coding for inflammatory mediators IL-1α, IL-1β, IL-6 and TNF-α. In addition, sixteen single nucleotide polymorphisms (SNPs) in inflammatory mediator genes were genotyped. An association was identified between IDD and IL6 polymorphism +15T>A in exon 5 (p = 0.007). In addition, IL6 haplotype GGGA of -597G>A, -572G>C, -174G>C and +15T>A in exon 5 associated with IDD (p = 0.0033). A functional SNP in the CILP gene has been suggested to cause IDD in the Japanese population. This functional variation was analyzed in 243 Finnish IDD patients and 259 controls, and in 348 Chinese individuals with degenerative MRI findings and 343 Chinese individuals with normal MRI. No association was found in the Finnish and Chinese study populations. In order to reveal chromosomal susceptibility loci and new candidate gene(s) for IDD a genome-wide scan was performed on 14 Finnish families with 186 individuals. Genome-wide and fine mapping analysis provided maximum two-point LOD scores of 2.71, 2.36 and 2.04 for chromosomes 21, 4, and 6, respectively. Second fine mapping confirmed the susceptibility of chromosome 21. Two candidate genes, ADAMTS-1 and ADAMTS-5, were analyzed in the region suggesting linkage, leading to the identification of thirteen sequence variations. However, none of the variations were disease causing.

The purpose of this study was to determine whether magnetic resonance imaging (MRI) accurately predicts surgical findings in dachshund dogs with thoracolumbar intervertebral disc extrusions (TLDE). Sixteen dogs presenting with signs of acute TLDE took part in this investigation. MRI was performed on each dog. This was followed by decompressive surgery with the completion of an intra-operative questionnaire documenting the site of the extrusion and spatial distribution of the disc material for each dog. An independent veterinary radiologist evaluated each MRI study, measured and recorded the same parameters from images, utilising 3 sequences (T1-, T2-weighted and Short T1 Inversion recovery) without knowledge of the surgical findings. The imaging findings were compared with the intra-operative measurements. The specific intervertebral disc (IVD) space from which the material extruded and lateralization of the extruded disc material (EDM) were found to be similar between MRI and surgical observations. Longitudinal distribution of the EDM was described as being cranial, caudal or equally distributed in relation to the affected IVD. A Kappa test showed moderate agreement in longitudinal distribution between MRI and surgery. Circumferential distribution was recorded on transverse images and compared to surgical findings. Recorded distribution only coincided completely in 1 case, although the rest of the cases showed good overlap of findings between the MRI and intraoperative findings.Our results could not demonstrate a statistically significant difference between T1-, T2-weighted or STIR sequences when determining the length of the extruded mass in the vertebral canal. We found that when evaluating the absolute error and range of error for each sequence, that the T2-weighted sequence had a narrower range of errors and was thus more consistent in predicting the size of the lesion pre-surgically. MRI was validated as a very useful imaging modality for neurological disorders in dogs. / Dissertation (MMedVet)--University of Pretoria, 2007. / Companion Animal Clinical Studies / unrestricted

<p> This study is one of the projects of the artificial joints group conducted by Professor W. R. Newcombe, Department of Mechanical Engineering and Dr. G. R. Viviani, Department of Surgery.</p> <p> A summary of the literature survey of the lower back which is pertinent to the design of a replacement for the lumbar spine is reported. Motions, force system, and strengths of the lumbar intervertebral joint are obtained from the literatures and calculation.</p> <p> Advantages of silicone elastomer and titanium as the biomaterials for the artificial disc are presented. An experiment to test the bond between titanium and silicone reveals that the strength provided by only applying primer is insufficient.</p> <p> Surface structure for prosthetic stabilization and initial fixation is discussed. Proposed design alternatives for artificial discs are presented with the attempts to reduce the number of moulds needed by introducing a prosthesis with a more regular shape.</p> <p> An important part of this thesis is to indicate the direction in which further work in this area should proceed.</p> / Thesis / Master of Engineering (MEngr)