Abstract Low back pain (LBP) is a truly enervating condition, presenting with considerable negative socioeconomic and health impacts on many levels. Although LBP may be attributed to many factors, there is increasing evidence that disc degeneration (DD) of the lumbar spine is a strong contributing factor, especially among young individuals. Understanding the aetiopathogenesis of DD has changed over the past few decades as numerous studies have indicated that inherited factors are largely responsible for the development of DD. Despite the many genetic associations in DD that have been reported, these associations have proven difficult to validate. The genetic component of DD is still unexplained for the most part. Previous studies have focused on adults, who have been exposed to environmental risk factors of DD, which may mask genetic associations. Thus, investigations among young individuals are well justified. The purpose of this study was to validate the associations between DD defined by magnetic resonance imaging (MRI) and genetic polymorphisms in two study populations of Finnish and Danish young individuals. New polymorphisms that have not been associated with DD were also included in the study. Associations with progression of DD were also investigated among Danish individuals. Furthermore, this study aimed to clarify the level of evidence of previously identified associations. Among Finnish individuals, polymorphisms in IL6, SKT and CILP were associated with moderate DD, but the association in CILP was significant only in women. Among Danish individuals, polymorphisms in IL6 and IL1A were associated with early DD and progression of DD. The genetic associations among the Danish teenagers were gender-specific as they were mainly observed in girls. Among both populations, the individuals with DD were significantly taller than individuals without DD. In the systematic analysis of previous reports, polymorphisms in GDF5, THBS2, MMP9, COL11A1, SKT and ASPN were found to have a moderate level of association evidence. The results mostly support earlier findings in adults. However, unexpected differences between genders were observed. In conclusion, this study increased the knowledge of genetics in DD but more investigations are needed to draw any solid conclusions. / Tiivistelmä Alaselkäkipu on yksi merkittävimmistä toimintakykyyn vaikuttavista sairauksista. Alaselkäkivun riskitekijöitä tunnetaan useita, mutta näyttö siitä, että selän välilevyrappeuma on yksi tärkeimmistä riskitekijöistä, erityisesti nuorilla henkilöillä, lisääntyy jatkuvasti. Aiemmat tutkimukset ovat osoittaneet, että perintötekijöillä on merkittävä osuus välilevyjen rappeutumisessa. Useiden geenien on raportoitu vaikuttavan välilevyrappeumaan. Positiivisten tulosten toistaminen on kuitenkin osoittautunut vaikeaksi, ja kokonaiskuva on vielä suurelta osin epäselvä. Aikaisemmat tutkimukset aiheesta ovat keskittyneet aikuisiin, joilla nuoria pidempi altistus ympäristötekijöille saattaa peittää geneettisten tekijöiden yhteyttä. Tämän tutkimuksen tavoitteena oli varmentaa yhteyksiä magneettikuvauksella (MRI) määritetyn välilevyrappeuman ja geneettisten monimuotoisuuskohtien (polymorfioiden) välillä käyttäen yhtä suomalaisista ja yhtä tanskalaisista nuorista koostuvaa aineistoa. Työssä analysoitiin myös polymorfioita, joita ei ole aiemmin yhdistetty välilevyrappeumaan. Yhteyttä polymorfioiden ja välilevyrappeuman etenemisen välillä tutkittiin tanskalaisessa aineistossa. Lisäksi tutkimuksen tavoitteena oli selvittää aiemmin tunnistettujen geneettisten yhteyksien näytön aste. Suomalaisten nuorten aineistossa polymorfiat IL6-, SKT- ja CILP-geeneissä olivat yhteydessä kohtalaista astetta olevaan välilevyrappeumaan. Tanskalaisten nuorten aineistossa polymorfiat IL6- ja IL1A-geeneissä olivat yhteydessä varhaiseen välilevyrappeumaan ja sen etenemiseen. Tanskalaisten nuorten aineistossa nämä yhteydet olivat sukupuolesta riippuvaisia, koska yhteyksiä havaittiin pääasiassa tytöillä. Suomalaisten nuoren aineistossa yhteys CILP-geenissä havaittiin ainoastaan nuorilla naisilla. Kummassakin tutkimusaineistossa nuoret, joilla oli välilevyrappeuma, olivat pidempiä, kuin nuoret, joilla ei ollut välilevyrappeumaa. Aikaisempien tutkimusten systemaattinen analyysi osoitti, että tunnistetun geneettisen yhteyden näytön aste on kohtalainen GDF5-, THBS2-, MMP9-, COL11A1-, SKT- ja ASPN-geenien polymorfioissa. Tutkimusten tulokset ovat pääosin samansuuntaisia aiempien tutkimuksien kanssa, mutta nyt nähty eroavaisuus sukupuolten välillä on uusi havainto. Kokonaisuudessaan tämä väitöstutkimus kasvattaa ymmärtämystä välilevyrappeumasta, mutta lisätutkimuksia aiheesta tarvitaan.

Abstract Modic changes are vertebral bone marrow signal intensity changes adjacent to the endplates of the degenerated intervertebral discs in magnetic resonance imaging (MRI). This study evaluated the prevalence and the determinants of Modic changes and their association with low back pain symptoms in an occupational cohort of middle-aged Finnish men. The prevalence and the natural course of Modic changes were assessed over a 3-year follow-up period among sciatica patients. Finally, in a patient population, the characteristics of bone marrow changes in MRI were compared to the imaging findings in CT. The prevalence of Modic changes was 56% in an occupational cohort of middle-aged males. Besides age, the determinants of Modic changes and disc degeneration were different. Weight-related factors, which add to the load of the lumbar spine, were associated with Modic changes, whereas whole-body vibration was associated with severe disc degeneration. The prevalence of Modic changes among sciatica patients was 65%, type II change being the most frequent. During the 3-year follow-up, 14% of changes converted to another type, while the incidence of new Modic changes was 6%. Among middle-aged working males, Modic changes located at L5–S1 and type I Modic changes were more likely to be associated with pain symptoms than other types of Modic changes or changes located at other lumbar levels. Thirty-eight percent of the endplates with Modic changes had sclerosis in CT. Of specific Modic types, mixed I/II and II/III associated significantly with endplate sclerosis. Endplate sclerosis was not detected in MRI. In conclusion, Modic changes are a common MRI finding both among patients and middle-aged working males. In addition to age, weight-related factors seem to be important in the pathogenesis of Modic changes. Modic changes can convert from one type to another and type II changes may be less stable than previously assumed. A considerable proportion of Modic changes are sclerotic as observed in CT. Modic changes were always found in combination with a degenerative intervertebral disc and thus they are assumed to be a specific phenotype of degenerative disc disease. Finally, Modic changes may be painful – especially when located at L5–S1 and type I changes.

Back pain is a highly prevalent condition whose pathogenesis is associated with intervertebral disc (IVD) degeneration. Degeneration is driven by abnormal cell biology, particularly within the IVD’s inner core, the nucleus pulposus (NP). In recent years, there has been an ever-increasing search for cell-based therapies aimed at correcting the cell biology and thus repairing/regenerating the degenerate IVD. The success of these novel therapies, however, requires a thorough understanding of IVD development and of the phenotype of its cells. The embryonic, foetal and juvenile NP is populated by large vacuolated notochordal cells that with skeletal maturity are replaced by smaller NP cells. Since notochordal cells have been shown to display protective and anabolic roles in the IVD their loss in humans has often been suggested to initiate the degenerative process. As such, a detailed understanding of notochordal cells and their regulatory pathways may help identify factors involved in IVD homeostasis and aid the development of novel cell-based therapies targeting IVD degeneration. The study of human notochordal cells has, however, been hindered by ethical, logistical and technical difficulties in obtaining suitable samples and, as such, the human notochordal cell phenotype is, to date, unknown, constituting a major limitation in the field. The work presented here was conducted with the objective of developing a methodology to isolate human developing notochordal cells (NP progenitors) from adjacent sclerotomal cells (annulus fibrosus and vertebral body progenitors), to characterise the notochordal cell phenotype and identify potential factors involved in notochordal cell biology. Initially, human embryonic and foetal spines were characterised to assess their suitability as a source of notochordal cells and to identify a notochord-specific marker that could be used to isolate notochordal cells for microarray studies. The human developing spine contained large vacuolated notochordal cells in all stages analysed (3.5-18 weeks post-conception (WPC)) that specifically expressed KRT8, KRT18 and KRT19 at all stages and CD24 between 5.5-18 WPC. KRT18 and CD24 were independently used to label notochordal cells (7.5-14 weeks post-conception) and separate them from sclerotomal cells. Methodologies were developed to allow extraction of RNA of sufficient quality for microarray analysis from fixed, permeabilised (in the case of KRT18) and/or, labelled and sorted cells (CD24). Microarray analysis identified and real-time qPCR and, for some markers, immunohistochemistry, validated GRB14, SLC19A1, FGF10, ADORA3, TBXA2R, CDH6, ANPEP, CD69, CD24, RTN1, PRPH, MAP1B, ISL1 and CLDN1 as human notochordal cell markers. Ingenuity pathway analysis was performed to investigate the pathways/networks and upstream regulators and downstream effectors of notochordal cells. Inhibition of inflammation and angiogenesis were identified as relevant to notochordal cell biology, function and, possibly, to the known protective and anabolic role notochordal cells display in the IVD. Notochordal marker gene expression was identified in adult NP tissue, and negatively correlated with degeneration. Proteins encoded by ADORA3 and MAP1B were expressed by a proportion of adult NP cells, suggesting the presence of notochord-derived cells in the adult NP.Importantly, this is the first study to detail a methodology and successfully isolate human notochordal cells. Such methodology has the potential to be used to culture and investigate the biology of viable human notochordal cells (CD24+ve). Future studies aimed at developing cell-based therapies for IVD degeneration could also use these identified markers to assess appropriate stem cell differentiation to notochordal cells.

Intervertebral disc (IVD) degeneration is associated with low back pain (LBP). It has been suggested that changes in the IVD physio-chemical microenvironment (i.e. hypoxia, reduced nutrient and acidic conditions) may lead to disc degeneration. Studying the response of human nucleus pulposus (NP) cells to these conditions could establish the causal relationship between IVD microenvironment and aberrant cellular behaviour, characteristic of disc degeneration. Human bone marrow mesenchymal stem cells (BM-MSCs) are a promising cell population for disc regeneration. However, knowledge of their survival and functioning in the microenvironment of the IVD is still lacking. Moreover, in vitro co-culture model studies that are used to study MSC/disc cell interaction, also need to consider the effect of the microenvironment on cellular responses. BM-MSCs and degenerate NP cells were cultured alone or co-cultured in monolayer under hypoxia (2%O2), reduced nutritional (2% serum or/and 5mM glucose) and acidic (moderate pH 6.8 or severe pH 6.5) conditions alone or in combination for 7 days. Cell viability, proliferation, gene and protein expression was assessed. Degenerate NP cells and BM-MSCs maintained good cell viability under all conditions. Both cell types demonstrated overall similar proliferation and gene and protein responses under the majority of the conditions and combinations studied. Hypoxia promoted aggrecan and versican matrix biosynthesis in both cell types. Nutrient deprived and moderate acidic conditions (pH 6.8) inhibited proliferation of both cell types. Interestingly the combination of hypoxia with these conditions showed a protective effect in modulating cell proliferation. These results imply that hypoxia may be beneficial in some instances. Nutrient deprived conditions had a relatively minor effect on degenerate NP cell gene and protein expression but these conditions specifically inhibited VCAN expression in BM-MSCs. The combination of hypoxia with these conditions increased or restored VCAN expression. Interestingly the combination of hypoxia with reduced glucose conditions increased aggrecan and versican matrix biosynthesis in both NP cells and BM-MSCs. The combination of hypoxia and complete nutrient deprived conditions (both reduced serum and reduced glucose) impaired ACAN, VCAN and PAX-1 gene and aggrecan and versican protein expression in degenerate NP cells implicating disc hypoxia and complete nutrient deprived combined microenvironment in accelerating degenerate changes in NP cells. In contrast, these conditions showed no such detrimental effects on BM-MSC gene and protein expression. pH 6.5 was critical for both cell types proliferation and ACAN and VCAN gene expression suggesting that severe acidic conditions may exacerbate degenerative changes and be inhibitory for implanted MSCs. Finally, a combination of hypoxia, complete nutrient deprived and moderate acidic conditions, reduced cell proliferation without affecting the gene expression profile of both cell types. IVD-like physio-chemical microenvironmental conditions also appeared to influence differentiation of BM-MSC and modulation of degenerate NP cell phenotype observed during co-culture. Noticeably hypoxia, reduced serum or reduced glucose conditions stimulated BM-MSC differentiation and modulation of degenerate NP cell phenotype. Hypoxia also increased or recovered changes at gene expression level in both BM-MSCs and degenerate NP cells under nutrient deprived (reduced serum or/and reduced glucose) conditions during co-culture. Degenerate NP cell and BM-MSC co-culture also showed noticeable increase in aggrecan and versican biosynthesis under hypoxia and reduced glucose combine conditions, implicating these in improving the co-culture responses. Severe pH condition alone, pH 6.8 in combination with hypoxia and finally all IVD-like physio-chemical conditions together compromised co-culture responses. Such results imply that IVD-like physio-chemical microenvironmental conditions may influence MSC based regenerative outcomes. This work has increased our understanding about the influence of disc harsh microenvironment on degeneration and regeneration processes.

Gymnastics is noted for involving highly specialized strength, power, agility and flexibility. Flexibility is perhaps the single greatest discriminator of gymnastics from other sports. The extreme ranges of motion achieved by gymnasts require long periods of training, often occupying more than a decade. Gymnasts also start training at an early age (particularly female gymnasts), and the effect of gymnastics training on these young athletes is poorly understood. One of the concerns of many gymnastics professionals is the training of the spine in hyperextension—the ubiquitous ‘arch’ seen in many gymnastics positions and movements. Training in spine hyperextension usually begins in early childhood through performance of a skill known as a back-bend. Does practising a back-bend and other hyperextension exercises harm young gymnasts? Current information on spine stretching among gymnasts indicates that, within reason, spine stretching does not appear to be an unusual threat to gymnasts’ health. However, the paucity of information demands that further study be undertaken.

No description available.

The increasing incidence of disc degeneration and its correlation with lower back pain is an alarming trend in modern society. The research of intervertebral disc degeneration and low back pain would greatly benefit from additional methods to study its etiology and possible treatment methods. A large animal model that maintains the biological and mechanical environment that is most similar to the human lumbar spine could provide substantial improvements in understanding and resolving the problem of intervertebral disc related low back pain.This dissertation presents my doctoral work of investigating the potential for the camelid cervical spine to serve as a suitable animal model for advancing biomechanical research of low back pain and intervertebral disc degeneration in the human lumbar spine. Specifically, this work identifies the cellular, morphological and biomechanical characteristics of the camelid cervical spine and intervertebral disc as compared to the human lumbar spine. My results demonstrate that there are remarkable similarities in all aspects. Many of the similarities with respect to the cellular environment of the intervertebral disc are a consequence of the camelid status as a large mammal. Additional testing of the cellular makeup of the camelid intervertebral disc cells revealed that many human qRT-PCR primers associated with disc degeneration are suitable for use in alpacas without modification. From a biomechanics standpoint, the camelid cervical spine also has a vertically oriented spinal posture and is unsupported near the end in an open kinetic chain, providing a mechanical parallel with the human lumbar spine. The camelid cervical intervertebral disc size is closer to the human lumbar intervertebral disc than all other currently used animal models available for comparison in the literature. Average flexibility (range of motion) of a camelid spinal motion segment showed similarities in all modes of loading. Based on magnetic resonance imaging and radiologic grading of the intervertebral disc, almost 90% of elderly camelids exhibited advanced degeneration (Pfirrmann grade 3 or higher) in their cervical spine, and about half of aged camelids have developed severe degeneration (Pfirrmann grade 4 or higher) in at least one or more of their cervical segments, most commonly within the two lowest cervical segments (e.g. c6c7 and/or c7t1). Thus, while there remain differences, the remarkable similarities between the camelid and human spine strengthen the case for using camelids as a model for human disc degeneration, normal and pathological biomechanics and fluid transport, and potentially as a pre-clinical model for investigating the efficacy of novel spinal devices.

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

The primary objective of this research is to associate lumbar segmental mechanical response with intervertebral disc degeneration under physiologic testing conditions. Because no mathematical model exists for lumbar spine segmental rotations, a portion of this thesis evaluates potential methods for curve fitting the torque-rotation curves. The Dual Inflection Point (DIP) Boltzmann equation was developed during the course of this research and is presented here as a method for fitting spinal motion data wherein a physical meaning can be assigned to each of the model coefficients. This model can tell us more about the effects of degeneration, testing conditions, and other factors that are expressed in the change in spinal motion. Previous studies have investigated the relationship between the degeneration grade and flexibility of the intervertebral disc, but were completed without the presence of a compressive follower load. This study builds on past work by performing the testing under a compressive follower load. Segmental stiffness, range of motion (ROM), hysteresis area, and normalized hysteresis (hysteresis area/ROM) were evaluated and the effect of degeneration, segment level, temperature, and follower load were analyzed. Twenty-one functional spinal units (FSUs) were tested in the three primary modes of loading at both body temperature and room temperature in a near 100% humidity environment. A compressive follower load of 440 N was applied to simulate physiologic conditions. Fifteen of the twenty-one segments were also tested without the follower load to determine the effects of the load on segmental biomechanics. The grade of degeneration for each segment was determined using the Thompson scale and the torque-rotation curves were fit with the DIP-Boltzmann sigmoid curve.The effect of degeneration was statistically significant (α = 0.05) for stiffness, ROM, and hysteresis area in axial rotation (AR) and lateral bending (LB); it was also statistically significant for ROM and normalized hystersis in flexion-extension (FE). The lumbosacral joint (L5-S1) was significantly stiffer in AR and LB; the decrease in ROM and hysteresis area in AR and LB were also statistically significant for the lumbosacral joint compared to L1-L2 and L3-L4. Temperature had a significant effect on stiffness and hysteresis area in AR and on hysteresis area in LB. The follower load increased stiffness in all three modes of loading, but was significant only in AR and LB; it also reduced ROM and increased normalized hysteresis in all three modes of loading.

The purpose of this research was to investigate the influence of applying an intrinsic decompressive pre-load to a particular dynamic stabilization device on the biomechanical response of the lumbar spine. The FlexSPAR, which supports this ability, was used as a test case. A finite element model of a full lumbar spine was developed and validated against experimental data, and tested in the primary modes of spinal motion. The model was used to compare five lumbar spine test cases: healthy, degenerate, implanted with a pre-loaded device, implanted with a device without a pre-load, and implanted with rigid fixators. Results indicated that a pre-loaded FlexSPAR led to improved disc height restoration and segmental biomechanics. Results also showed that a pre-loaded FlexSPAR led to less change in bone remodeling stimulus in comparison to the device without a pre-load and rigid fixators. This work shows that there is a potential to improve the performance of posterior dynamic stabilization devices by incorporating a pre-load in the device.