Introdução: A microdiscectomia para tratamento de hérnia de disco lombar, mesmo apresentando ótimos resultados, pode resultar em danos consequentes à lesão tecidual local. As cirurgias endoscópicas já são consideradas padrão ouro em outras áreas da medicina devido ao mínimo dano colateral causado e consequente melhora dos resultados. Autores internacionais demonstraram a eficácia e segurança da técnica, mas ainda não existem estudos na América Latina que validem esses estudos. Objetivo: Comparar os resultados cirúrgicos da abordagem endoscópica e convencional para tratamento da hérnia de disco lombar quanto à melhora da dor, da incapacidade e suas complicações. Métodos: Estudo prospectivo randomizado envolvendo pacientes com hérnia de disco lombar, submetidos a tratamento cirúrgico. Quarenta e sete pacientes foram randomizados prospectivamente em dois grupos, discectomia endoscópica e microdiscectomia, e foram acompanhados ao longo de 12 meses. Questionário de incapacidade de Oswestry validado para o português e escala analógica de dor foram aplicados durante o seguimento. Os eventos adversos também foram recordados. Resultados: Após a cirurgia os pacientes tiveram melhoras significativas da dor irradiada (68%), mas sem diferença entre os grupos estudados e apresentaram significativa melhora da incapacidade. Quanto a dor lombar, a discectomia endoscópica resultou em menor dor lombar pós-operatória nas avaliações de uma semana, um e três meses quando comparada a microdiscectomia. Entretanto não se observou diferença entre os grupos no sexto e décimo segundo mês de seguimento. Não foram evidenciadas diferenças estatísticas quanto a recidiva, infecções e cirurgias subsequentes. Conclusão: Os resultados clínicos da discectomia endoscópica são semelhantes aos da microdiscectomia quanto à melhora da dor irradiada e da incapacidade, mas oferecem uma vantagem quanto à dor lombar pós-operatória até o terceiro mês. A discectomia endoscópica consiste em uma técnica segura e eficaz representando uma alternativa ao tratamento padrão ouro representado pela microdiscectomia / Introduction: Microdiscectomy, despite the good results, may result in damages to the local tissue. In other fields, endoscopic surgeries are considered the gold standard due to the minimal collateral damage. There aren\'t studies comparing both methods performed in Latin America. Objective: Compare the traditional microdiscectomy and percutaneous endoscopic lumbar discectomy for the treatment of disc herniation regarding pain, disability and complications. Methods: Prospective randomized trial with patients with sciatica due to lumbar disc herniation comparing two different surgical techniques. Forty-seven patients were divided in two groups and monitored for twelve months. Oswestry disability index and visual analog scale for pain were recorded. Results: After surgery the leg pain and disability improved significantly, but without significant difference between the groups. There was significantly less back pain after surgery until the third month. After that the groups were statistically the same. There were no statistical differences regarding recurrence, infection and subsequent surgeries. Conclusion: Endoscopic discectomy results are similar than conventional microdiscectomy according to pain and disability improvement, however, lumbar pain are less during the first three months. Endoscopic discectomy consists in a safe and efficient alternative to microdiscectomy

No description available.

Thesis (PhD (Industrial Engineering))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Back pain is a common concern amongst a growing population of people across the world today, where in most cases the pain can become unbearable resulting in major lifestyle adjustments. Seventy to eighty percent of the population of the Western world experiences low-back pain at one time or another. Pain can be produced as a worn disc becomes thin, narrowing the space between the vertebrae. Pieces of the damaged disc may also break off and cause irritation to the nerves signalling back pain. Depending on the severity of a patient’s condition, and after conservative treatment options have been exhausted, a disc replacement surgery (arthroplasty) procedure may be prescribed to restore spacing between vertebrae and relieve the pinched nerve, while still maintaining normal biomechanical movement. Typical complications that are however still observed in some cases of disc implants include: anterior migration of the disc, subsidence (sinking of disc) and lateral subluxation (partial dislocation of a joint). Issues such as function, correct placement and orientation, as well as secure fixation of such a disc implant to the adjacent vertebrae are highly important in order to replicate natural biomechanical behaviour and minimise the occurrence of the complications mentioned. As various imaging and manufacturing technologies have developed, the option for individual, patientspecific implants is becoming more of a practical reality than it has been in the past. The combination of CT images and Rapid Manufacturing for example is already being used successfully in producing custom implants for maxilla/facial and cranial reconstructive surgeries. There exists a need to formalise a process chain for the design and manufacture of custom-made intervertebral disc implants and to address the issues involved during each step. Therefore this study has investigated the steps involved for such a process chain and the sensible flow of information as well as the use of state-of-the-art manufacturing technologies. Strong emphasis was placed on automation of some of the processes as well as the user-friendliness of software where engineers and surgeons often need to work together during this multi-disciplinary environment. One of the main benefits for customization was also investigated, namely a reduction in the risk and potential for implant subsidence. Stiffness values from pressure tests on vertebrae were compared between customized implants and implants with flat endplate designs. Results indicated a statistically significant improvement of customized, endplate matching implants as opposed to flat implant endplates. Therefore it may be concluded that the use of customized intervertebral disc implants with patient specific endplate geometry may decrease the risk and potential for the occurrence of subsidence. / AFRIKAANSE OPSOMMING: Rugpyn is ‘n algemene bekommernis vir ‘n groeiende populasie van mense in die wêreld vandag, waar in meeste gevalle die pyn ondraagbaar kan raak en groot leefstyl aanpassings vereis. Sewentig tot tagtig persent van die populasie in die Westerse wêreld ondervind lae rugpyn op een of ander stadium. Die pyn kan veroorsaak word deur ‘n intervertebrale skyf wat verweer en dunner word, en veroorsaak dat die spasie tussen die vertebrae vernou. Stukkies van die beskadigde skyf mag ook afbreek en irritasie aan die senuwees veroorsaak wat verdere pyn kan veroorsaak. Afhangende van die ernstigheid van ‘n pasiënt se geval, en nadat opsies vir konservatiewe behandeling uitgeput is, kan ‘n skyf vervangings-prosedure (artroskopie) voorgeskryf word om die spasie tussen die vertebrae te herstel en sodoende die geknypte senuwee te verlos. Die skyf vervanging herstel spasiëring tussen vertebrae terwyl die normale biomeganiese beweging ook behoue bly, in teenstelling met ‘n fusieprosedure wat die betrokke vertebrae aanmekaar vasheg en normale beweging belemmer. Tipiese komplikasies wat egter steeds na ‘n skyf vervanging in sommige gevalle waargeneem word sluit in: anterior migrasie van die inplantaat, insinking, sowel as laterale sublukasie (gedeeltelike dislokasie van ‘n gewrig). Faktore soos funksie, korrekte posisionering en orientasie, sowel as vashegting van so ‘n skyf inplantaat tot die aanliggende vertebrale bene is besonder belangrik om natuurlike biomeganiese beweging te herstel en sodoende bogenoemde komplikasies te verminder. Soos wat verskeie beeldings- en vervaardigingstegnologië verbeter het oor die laaste dekade, het die moontlikheid vir individuele, pasiënt-spesifieke inplantate al hoe meer ‘n praktiese realiteit begin word. Die kombinasie van Gerekenariseerde Tomografie (GT), tesame met Snel Vervaardiging word byvoorbeeld reeds suksesvol aangewend tydens die ontwerp en vervaardiging van pasiënt-spesifieke inplantate vir maksilla- en kraniale rekonstruktiewe chirurgie. Daar bestaan egter ‘n behoefte om ‘n formele prosesketting vir die ontwerp en vervaardiging van pasiënt-spesifieke intervertebrale skyf inplantate te ontwikkel en om belangrike faktore tydens elke stap noukeurig te beskryf. Hierdie studie het na die verskillende stappe in die prosesketting gekyk om ‘n sinvolle vloei van informasie en benutting van hoë gehalte vervaardigingstegnologië saam te snoer. Sterk klem was gelê op outomatisering van prosesse asook gebruikersvriendelikheid van sagteware waar ingenieurs en medici dikwels saam moet werk tydens hierdie kruisdissiplinêre omgewing. Een van die hoof verwagte voordele met die gebruik van pasklaar skyf inplantate, naamlik die vermindering van moontlike insinking van die inplantaat in die been, is ook ondersoek. Die ondersoek het druktoetse behels en die vergelyking van ooreenstemmende styfheid tussen inplantate wat die kontoer van die bene volg teenoor gewone plat eindplate. Die resultate was statisties beduidend in die guns van die pasklaar inplantate wat die beenkontoere gevolg het, en bewys dus dat die risiko vir insinking verminder is.

Title: Physical activity of patients after surgical treatment of the lumbar spine. Aim: Main aim of my diploma thesis is to present an up to date review on the topic of postoperative physiotherapy in short-term and long-term phase after lumbar surgery and to find out how recommendations about postoperative physiotherapy are created. Methods: A systematic review on the topic. Results: The review answers the questions about physiotherapy after lumbar surgery in short-term and long-term phase and shows current trends and unique approaches in this study area. Keywords: Lumbar spine, intervertebral disc, discectomy, physiotherapy, physical activity.

Introdução: Os discos intervertebrais são estruturas importantes para a manutenção da saúde da coluna vertebral. Sua integridade pode ser afetada quando há desequilíbrio sagital ou alterações nos parâmetros espinopélvicos da coluna vertebral. Propósito: Avaliar potencial associação entre os parâmetros espinopélvicos da coluna vertebral e os componentes bioquímicos dos discos intervertebrais lombares em indivíduos adultos jovens assintomáticos utilizando técnicas quantitativas em ressonância magnética. Métodos: Nosso grupo de estudo foi composto por 93 voluntários assintomáticos com idade entre 20 e 40 anos (49 mulheres e 44 homens). Imagens ponderadas em T2, relaxometria T2 e relaxometria T1? no plano sagital da coluna lombar foram adquiridas por meio de um aparelho de ressonância magnética de 1.5T. Os parâmetros espinopélvicos analizados incluíram inclinação sacral (IS), versão pélvica (VP), incidência pélvica (IP), lordose lombar (LL), cifose torácica (CT), alinhamento toracolombar (TL), eixo sagital vertical (SVA), ângulo espinossacral (SSA), comprimento de T1 a S1 e L1 a S1, estes mensurados em uma radiografia panorâmica da coluna. Os voluntários também foram subdividos dentro dos quatro subtipos posturais de Roussouly para verificar a incidência de discos degenerados entre estes subgrupos. Resultados: A LL correlacionou com os tempos de relaxação T2 em todos níveis discais (L1L2: R=0,28; L2L3: R=0,25; L3L4: R=0,22; L4L5: R=0,24; L5S1: R=0,31). Observou-se uma correlação similar entre CT e a relaxometria T2 em L4L5 (R=0,25) e L5S1 (R=0,29) e também entre TL e o tempo de relaxação de L5S1 (R=0,21). Apenas a VP correlacionou-se com a relaxometria T1? nos níveis de L3L4 (R= -0,24) e L4L5 (R= -0,26). O volume dos discos correlacionou com o comprimento de T1S1 em todos níveis (L1L2: R=0,61, L2L3: R=0,66, L3L4: R=0,64, L4L5: R=0,61, L5S1: R=0,47). O Tipo 2 de Roussouly apresentou uma frequência maior de discos degenerados em L4L5 que o Tipo 4 (P < 0,05). Conclusão: A baixa magnitude de alguns parâmetros espinoélvicos como LL, CT, TL e VP apresentam uma discreta associação com a redução conteúdo hídrico e de proteoglicanos dos discos lombares. Os demais parâmetros espinopélvicos não apresentaram correlação com a composição do disco em indivíduos jovens assintomáticos. / Introduction: Intervertebral discs (IVD) are important structures for the spine health. Its integrity may be affected when there is sagittal imbalance or changes in spinopelvic parameters. Purpose: To evaluate potential associations between spinopelvic parameters and the biochemical composition of lumbar intervertebral discs using quantitative magnetic resonance imaging in asymptomatic young adults. Methods: Our study group comprised 93 asymptomatic volunteers aged 20-40 years (49 women and 44 men). Lumbar spine T2- weighted images, T2 relaxometry and T1? relaxometry were acquired on a 1.5T MRI scanner. Spinopelvic parameters including sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), lumbar lordosis (LL), thoracic kyphosis (TK), thoracolumbar alignment (TL), sagittal vertical axis (SVA), spinosacral angle (SSA), C2 pelvic angle (CPA), and T1S1 and L1S1 length were measured on panoramic spine radiographs. The volunteers were also subdivided into the four postural subtypes of Roussouly. Results: LL correlated with T2 relaxation at all IVD levels (L1L2: R=0.28; L2L3: R=0.25; L3L4: R=0.22; L4L5: R=0.24; L5S1: R=0.31). We observed a similar correlation between TK and T2 relaxometry at L4L5 (R=0.25) and L5S1 (R=0.29) and between TL and L5S1 (R=0.21). Only PT correlated with T1? relaxometry at the levels of L3L4 (R = -0.24) and L4L5 (R = -0.26). IVD volume correlated with T1S1 length at all levels (L1L2: R=0.61, L2L3: R=0.66, L3L4: R=0.64, L4L5: R=0.61, L5S1: R=0.47). Roussouly Type 2 presented a higher frequency of degenerated discs in L4L5 than Type 4 (P <0.05). Conclusion: The low magnitude of some spinopelvic parameters such as LL, TK, TL and PT present a discrete association with the reduction of water content and proteoglycans of the lumbar discs. The other spinopelvic parameters had no correlation with the disc composition in asymptomatic young individuals.

Introdução: A degeneração do disco intervertebral tem alta prevalência e é sabidamente associada à dor lombar. O objetivo deste trabalho foi correlacionar os valores de relaxometria T2 dos discos intervertebrais lombares com os parâmetros espinopélvicos em pacientes com dor lombar crônica. Materiais e métodos: Entre março a setembro de 2015, 91 pacientes consecutivos (56 mulheres, média de idade 53,5 anos, DP 11,6 anos, 23-76 anos e 35 homens, média de idade 53,6 anos, DP 11,9 anos, 19-73 anos) com dor lombar crônica foram incluidos neste estudo prospectivo. O Comitê de Ética Local aprovou o estudo e o consentimento foi obtido de cada paciente. Todos os indivíduos foram avaliados pelo índice de incapacidade Oswestry e escala visual analógica e não possuiam outras doenças da coluna vertebral, exceto degeneração discal. Os parâmetros espinopélvicos incidência pélvica (IP) versão pélvica (VP), inclinação sacral (IS), eixo vertical sagital (EVS), versão global (VG), ângulo espinopélvico (ASP), ângulo espinossacral (ASS), ângulo T1 pélvico (ATP), lordose lombar (LL), cifose torácica (CT), diferença entre a incidência pélvica e a lordose lombar (IP-LL) e a falta de lordose lombar (FLL) foram mensurados a partir de radiografias panorâmicas da coluna e pelve com o paciente na posição supina utilizando o software Surgimap®. O grupo de estudo foi categorizado de acordo com a classificação de Roussouly. Os mapas de relaxometria T2 foram adquiridos em aparelho de ressonância magnética de 1.5 Tesla para extrair os tempos de relaxação T2 e a segmentação manual completa dos discos lombares intervertebrais de cada paciente foi realizada no software Display®. Para verificar a reprodutibilidade desta avaliação, a concordância inter-observador para a segmentação manual dos discos intervertebrais lombares e mensuração dos parâmetros espinopélvicos foi avaliada. A significância estatística foi aceita quando p <0,05. Resultados: Os valores de relaxação T2 se correlacionaram significativamente com os parâmetros VP, VG, ASP, ATP, IP-LL e FLL em pacientes com dor lombarcrônica. Não encontramos correlação significativa entre os valores de relaxação T2 e os parâmetros IS, IP, ASS, EVS, LL, CT e questionários clínicos. A divisão por subtipos de Roussouly não se correlacionou com a degeneração discal avaliado pelo tempo de relaxação T2. A mensuração dos parâmetros espinopélvicos e a segmentação manual dos discos intervertebrais lombares mostraram uma alta reprodutibilidade interobservador. Conclusões: Indivíduos com maiores VP, VG, ATP, IP-LL e FLL apresentaram valores mais baixos de relaxação T2 nos discos intervertebrais. Para o nosso conhecimento, esse é o primeiro estudo a correlacionar os parâmetros espinopélvicos com a degeneração discal avaliada por meio da relaxometria T2. / Purpose: Intervertebral disc degeneration has a high prevalence and is known to be associated with low back pain.The purpose of this study was to correlate quantitative T2 relaxation measurements of lumbar intervertebral discs (IVD) with spinopelvic parameters and clinical symptoms in patients with chronic low back pain. Methods: From March to September 2015, 455 intervertebral discs from 91 consecutive patients (56 women, mean age 53.5 years, SD 11,7 years, 23-76 years and 35 men, mean age 53,6 years, SD 11.9 years, 19-73 years) with chronic low back pain were included in this prospective study. The study was approved by the local ethics committee, and written consent was obtained from all patients. All subjects were assessed by Oswestry Disability Index and Visual Analog Score questionnaires and were confirmed to have no other spine diseases except disc degeneration. Spinopelvic parameters including pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), sagittal vertical axis (SVA), global tilt (GT), spinopelvic angle (SPA), spinosacral angle (SSA), T1-pelvic angle (TPA), lumbar lordosis (LL), thoracic kyphosis (TK), PI-LL (pelvic incidence minus lumbar lordosis) and lack of lumbar lordosis (LLL) were measured from standing spine and pelvis lateral radiographs using the software Surgimap®. The study group was categorized according to the Roussouly classification. Saggital T2 maps were acquired in a 1.5T MRI scanner to extract the IVD relaxation times and the complete manual segmentation of the IVD of each patient in all levels was performed using the software Display®. To assess the reproducibility of this evaluation, the interobserver agreement fot the manual segmentation of the lumbar intervertebral discs and measurement of the spinopelvic parameters was performed. Statistical significance was accepted when p <0.05. Results: Lumbar intervertebral discs T2 relaxation times correlated significantly with PT, GT, SPA, TPA, PI-LL and LLL in patients with chronic low back pain. We found no significant correlation between T2 values and SS, PI, ASS, SVA, LL, TK andclinical questionnaires. Roussouly subtypes and clinical questionnaires did not correlate with T2 relaxation times. Conclusions: Individuals with higher PT, GT, TPA, PI-LL and LLL showed decreased intervertebral disc T2 relaxation values. To our knowledge, this is the first study to correlate spinopelvic parameters with disc degeneration evaluated by T2 relaxometry.

As alterações morfológicas do envelhecimento normal do disco intervertebral confundem-se com as patológicas. O objetivo deste estudo foi elaborar um perfil destas alterações. Discos intervertebrais cervicais e lombares foram coletados de 30 indivíduos assintomáticos: 15 jovens e 15 idosos. A morfologia foi analisada por macroscopia, ressonância magnética, histologia, microscopia eletrônica de varredura (MEV) e imuno-histoquímica para os colágenos de tipo I, II, III, IV, V, VI, IX e X. Alterações degenerativas foram mais acentuadas nos discos de idosos. O anel fibroso possui lamelas oblíquas que se adensam com o envelhecimento. A análise histológica não revela um núcleo distinto em nível cervical, porém a MEV o demonstra. As fibras colágenas sofreram intenso remodelamento e formam um padrão único para cada segmento. Alterações em nível cervical são semelhantes às lombares com algumas peculiaridades: substituição cartilagínea é comum. Muitas das técnicas rotineiras de avaliação não conseguem detectar as alterações discais ultraestruturais únicas de cada segmento. / The morphological alterations of normal aging in the intervertebral disc are frequently mistaken for those considered to be pathologic. Our aim is to elaborate a morphological profile of these alterations. Human cervical and lumbar intervertebral discs were harvested from 15 young (<35 years old) and 15 elderly (>65 years old) asymptomatic individuals. Their morphology was studied utilizing macroscopic technique, magnetic resonance, histology, scanning electron microscopy (SEM) and immunohistochemistry against types I, II, III, IV, V, Vi, IX and X collagens. Degenerative changes were more evident in discs of elderly individuals but even young discs displayed significant degeneration. The annulus is composed of oblique lamellae that get denser as they age. Histology frequently did not reveal a distinct nucleus in the cervical segment but SEM did. Collagen fibers form a pattern unique to each segment. Alterations in cervical discs are similar to those in lumbar specimens but include peculiarities. Several alterations could not be detected by MR or normal histology.

As alterações morfológicas do envelhecimento normal do disco intervertebral confundem-se com as patológicas. O objetivo deste estudo foi elaborar um perfil destas alterações. Discos intervertebrais cervicais e lombares foram coletados de 30 indivíduos assintomáticos: 15 jovens e 15 idosos. A morfologia foi analisada por macroscopia, ressonância magnética, histologia, microscopia eletrônica de varredura (MEV) e imuno-histoquímica para os colágenos de tipo I, II, III, IV, V, VI, IX e X. Alterações degenerativas foram mais acentuadas nos discos de idosos. O anel fibroso possui lamelas oblíquas que se adensam com o envelhecimento. A análise histológica não revela um núcleo distinto em nível cervical, porém a MEV o demonstra. As fibras colágenas sofreram intenso remodelamento e formam um padrão único para cada segmento. Alterações em nível cervical são semelhantes às lombares com algumas peculiaridades: substituição cartilagínea é comum. Muitas das técnicas rotineiras de avaliação não conseguem detectar as alterações discais ultraestruturais únicas de cada segmento. / The morphological alterations of normal aging in the intervertebral disc are frequently mistaken for those considered to be pathologic. Our aim is to elaborate a morphological profile of these alterations. Human cervical and lumbar intervertebral discs were harvested from 15 young (<35 years old) and 15 elderly (>65 years old) asymptomatic individuals. Their morphology was studied utilizing macroscopic technique, magnetic resonance, histology, scanning electron microscopy (SEM) and immunohistochemistry against types I, II, III, IV, V, Vi, IX and X collagens. Degenerative changes were more evident in discs of elderly individuals but even young discs displayed significant degeneration. The annulus is composed of oblique lamellae that get denser as they age. Histology frequently did not reveal a distinct nucleus in the cervical segment but SEM did. Collagen fibers form a pattern unique to each segment. Alterations in cervical discs are similar to those in lumbar specimens but include peculiarities. Several alterations could not be detected by MR or normal histology.

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.

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.