microRNAs (miRNAs), ~21-24 nucleotide-long RNAs that post-transcriptionally regulate gene expression, have rapidly become one of the most extensively studied mechanisms of the past decade. Since their discovery as temporal regulators of post-embryonic development in C. elegans, miRNAs have been functionally implicated in almost every cellular process investigated to date. miRNAs are integral to the complex biological processes of embryonic development and aging. In this research, we sought to determine whether misregulation of miRNAs could be responsible for eliciting adverse effects during these two distinct developmental stages. First, to uncover the potential role of miRNAs in teratogenicity, we investigated whether miRNAs were involved in regulation of retinoic acid (RA) induced vertebrate axis defects. Global miRNA expression profiling revealed that RA exposure suppressed the expression of miR-19 family members during zebrafish somitogenesis. Bioinformatics analyses predict that miR-19 targets cyp26a1, a key RA detoxifying enzyme, and a physiological reporter assay confirmed that cyp26a1 is a bona fide target of miR-19. Transient knockdown of miR-19 phenocopied RA-induced body axis defects. In gain-of-function studies, exogenous miR-19 rescued the axis defects caused by RA exposure. Our findings indicate that the teratogenic effects of RA exposure result, in part, from repression of miR-19 and the subsequent misregulation of cyp26a1. This highlights a previously unidentified role of miR-19 in facilitating vertebrate axis development. Next, to explore whether age-related changes in miRNAs trigger deficits in regeneration capacity, we performed mRNA and small RNA sequencing on regenerating and non-regenerating caudal fin tissue from aged, adult and juvenile zebrafish. An unbiased approach identified cbx7 as the most abundant transcript with significantly increased expression in regenerative-competent adult and juvenile tissue and decreased expression in regenerative-compromised aged tissue. While cbx7 is a known regulator of aging, this is the first report of its role in tissue regeneration. A computational approach was used to discover mRNAs expressed during regeneration, which are potential targets of the significantly expressed miRNAs in regenerating tissue. miR-21 was one of the most abundant and significantly increased miRNAs in regenerating tissue and exhibited an aberrant age-dependent expression profile. Bioinformatics predicts miR-21 to target the 3' UTR of cbx7 and a reporter assay confirmed that miR-21 targets cbx7 in vivo. Transient knockdown of miR-21 inhibited tissue regeneration, suggesting a role for miRNA mediated regulation of cbx7 during regeneration. These findings reveal a novel, age-dependent regenerative function of cbx7 and emphasize the importance of miR-21 as a master regulator of vertebrate regenerative responses. This research, when combined, underscores the negative consequences misregulation of miRNAs has on embryonic development and aging. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from Dec. 5, 2012 - Dec. 5, 2013

The present work is analyzing the general biomechanical aspects of fixation techniques in the upper and lower cervical spine along with clinical implications. The in vitro biomechanical properties of five different posterior atlanto-axial fixation techniques are compared. They provided for either a one, two or three-point fixation between atlas and axes. A new device, the C1 claw was biomechanically tested, which allow for fixation without the need for a structural bone graft. The three-point reconstructions indicated superior biomechanical properties compared to all others. The new C1 claw device was clinically evaluated in a series of 26 patients treated with a posterior C1-C2 fusion. There were no clinical or radiological failures in the series, Twenty-one patients out of twenty-three with any length of follow up either showed a solidly healed fusion or a healed fracture. Distractive flexion (DF) injuries in the lower cervical spine treated with anterior plate alone were analyzed with respect to healing rate and complications in a consecutive series of 36 patients. Results indicated that DF injury stage 1 and 2 according to Allen and Ferguson healed without complication, whereas DF injuries stage 3 had a high frequency of failure, needing an additional posterior fixation. The in vitro biomechanical properties of four different fixation techniques for a distractive flexion injury stage 3 were analyzed. The result indicated that anterior plate alone for fixation of a DF injury stage 3 is insufficient supporting the clinical finding in the previous study. Adjacent level motion was analyzed following a one segment fusion in the lower cervical spine. Motion was found to increase in adjacent levels possibly contributing to accelerated degeneration.

Pathologische Veränderungen der Wirbelsäule können zur Verkleinerung der Foramina intervertebralia der Halswirbelsäule sowie zur Verkürzung der Abstände zwischen den Dornfortsätzen der Brustwirbelsäule führen. Eine Veränderung der Kopf-Hals-Haltung kann ebenfalls die Dimension der Foramina intervertebralia sowie die Abstände zwischen den Dornfortsätzen beeinflussen. Die Bestimmung des Einflusses der Kopf-Hals-Haltung auf die genannten Parameter bei der radiologischen Darstellung der Wirbelsäule war deshalb das Ziel der vorliegenden Arbeit. In drei unterschiedlichen Kopf-Hals-Haltungen wurde die Halswirbelsäule von 25 klinisch unauffälligen Pferden im laterolateralen Strahlengang dargestellt. Laterolaterale Röntgenaufnahmen der Brustwirbelsäule von 23 Pferden ohne klinische Anzeichen einer Erkrankung der Wirbelsäule wurden ebenfalls in drei verschiedenen Kopf-Hals-Haltungen angefertigt. Die Auswertung dieser Aufnahmen erfolgte mit Hilfe von neu entwickelten Messmethoden, die eine hohe Reproduzierbarkeit aufwiesen. Auf den Aufnahmen der Halswirbelsäule wurde die Länge der Wirbelkörper und die Dimension der Foramina intervertebralia bestimmt. Zusätzlich wurden die Winkel zwischen angrenzenden Halswirbeln ermittelt. Der Abstand zwischen benachbarten Dornfortsätzen sowie die Breite der Dornfortsätze wurden für die Auswertung der Aufnahmen der Brustwirbelsäule gemessen. Für eine exaktere Auswertung der Aufnahmen der Brustwirbelsäule wurde ein spezieller Bildfilter entwickelt, der durch eine bessere Detailerkennbarkeit zu einer genaueren Messung der Streckung führte. Sowohl für die Breite der Dornfortsätze als auch für die Länge der Wirbelkörper der Halswirbel konnten keine signifikanten Unterschiede zwischen den Röntgenaufnahmen in den verschiedenen Kopf-Hals-Haltungen gefunden werden. Beide Strecken dienten zur Überprüfung des Versuchsaufbaus, um andere Ursachen für eine unterschiedliche Größe der Messstrecken auszuschließen. Die Foramina intervertebralia waren bei tiefer Kopf-Hals-Haltung signifikant größer als bei den anderen beiden Kopf-Hals-Haltungen (p < 0,05). Zwischen hoher und physiologischer Kopf-Hals-Haltung stellten sich nur die Foramina intervertebralia zwischen sechstem und siebten Halswirbel unterschiedlich groß dar (p < 0,05). Die Abstände zwischen angrenzenden Brustwirbeln waren vom achten bis zum vierzehnten Dornfortsatz in tiefer Kopf-Hals-Haltung größer als in den beiden anderen Kopf-Hals-Haltungen (p < 0,05). Diese Abstände nahmen insgesamt von kranial nach kaudal ab (p < 0,05) ab. Der zwölfte Dornfortsatz diente dabei zur Identifizierung der anderen, da er sich signifikant von den schmaleren kranialen und den breiteren kaudalen Dornfortsätzen unterschied (p < 0,01). Die Kopf-Hals-Haltung während der radiologischen Untersuchung beeinflusst sowohl die Dimension der Foramina intervertebralia als auch den Abstand zwischen den Dornfortsätzen. Deshalb sollte diese bei der Auswertung radiologischer Aufnahmen immer berücksichtigt werden. Die Foramina intervertebralia stellten sich bei tiefer Kopf-Hals-Haltung am größten dar und können somit in dieser am besten beurteilt werden, jedoch kommt es zu einer Veränderung der Anordnung der Wirbel, so dass diese nur noch eingeschränkt beurteilt werden können. Eine tiefe Kopf-Hals-Haltung führt zur Vergrößerung der Abstände zwischen den Dornfortsätzen und kann somit die Beurteilung von Röntgenaufnahmen der Brustwirbelsäule, gerade im Rahmen einer Kaufuntersuchung, beeinflussen. Die Kopf-Hals-Haltung bei der Anfertigung von Röntgenaufnahmen der Wirbelsäule sollte standardisiert werden, um durch verbesserte Vergleichbarkeit Manipulationen und Fehlinterpretationen einzuschränken. / Pathological changes of the spine can lead to reduction of the intervertebral foramina dimensions in the cervical spine and to shortening of the distances between the spinous processes in the thoracic spine. However, alteration of the head and neck position influences the dimensions of the intervertebral foramina as well as the distances between the spinous processes. Determining the influence of the head and neck position on these parameters during radiological examination of the equine spine was the aim of this study. In three different head and neck positions lateral-lateral views of the cervical spine in 25 clinically sound horses were radiographically obtained. Lateral-lateral radiographs of the thoracic spine from 23 horses lacking clinical signs of spine diseases were taken in three different head and neck positions. Evaluation of the radiographs was carried out with newly developed measurement techniques providing high reproducibility. On the radiographs of the cervical spine the length of the vertebral bodies and the dimension of the intervertebral foramina were measured. Additionally, the angles between adjacent cervical vertebrae were determined. The distances between adjacent spinous processes and the width of the spinous processes were measured for evaluating the radiographs of the thoracic spines. For a more accurate evaluation of the thoracic spine radiographs a purpose-built image filter was developed, which provided more accurate measurement of the distances through better detail recognition. No significant differences were found for the width of the spinous processes of the thoracic vertebrae and the length of vertebral bodies of the cervical vertebrae between the radiographs taken in the three different head and neck positions. Both these distances were used to verify the experimental set-up to rule out other causes for differences in the measured distances. The intervertebral foramina were significantly wider in the low head and neck position than in the other two head and neck positions (p < 0.05). Between the high and the free head and neck position only the intervertebral foramina of the sixth and seventh cervical vertebrae showed different dimensions (p< 0.05). The distances between the adjacent thoracic vertebrae from the eighth to the fourteenth spinous processes were wider in the low head and neck position compared to the other two head and neck positions (p < 0.05). Altogether, these distances decreased from cranial to caudal (p < 0.05). The twelfth spinous process served for numerical identification of the other spinous processes due to its significant difference in width to the narrower cranial and broader caudal spinous processes (p < 0.05). The head and neck position during radiographic examination influences the dimensions of the intervertebral foramina as well as the distances between the spinous processes. Therefore, it should always be considered when evaluating radiographs. In the low head and neck position the intervertebral foramina turned out to be the widest and could be best assessed. However, this resulted in changes to the alignment of the vertebrae and therefore a limited assessment. A low head and neck position leads to an increase in the distances between the spinous processes and could influence the evaluation of radiographs especially if these are taken as part of a pre-purchase examination. During the radiographic examination of the spine the head and neck position should be standardised in order to reduce manipulation and misinterpretation through better comparability of such radiographs.

Many families of catfish produce sounds via pectoral spine stridulation and/or swim bladder compression using sonic muscles attached to the swim bladder. The sound production capabilities and characteristics in Loricariidae, the largest catfish family, have not been well examined. Sounds produced by two loricariid catfish species, Macrotocinclus affinis and Pterygoplichthys gibbiceps were recorded. Both species produce broad band calls via pectoral spine stridulation. These species produce sounds by rubbing the ridges of the dorsal process of the pectoral spine base against the groove of the pectoral girdle. Call duration was generally shorter in M. affinis (2-15 ms) as opposed to those produced by P. gibbiceps (20-200 ms). Mean dominant frequencies were approximately 4000 Hz for M. affinis and 1000 (abduction) and 4500 Hz (adduction) for P. gibbiceps. Light and scanning electron microscopy were used to examine the dorsal process of the pectoral spines from the largest and smallest M. affinis, and from a wide range of sizes from P. gibbiceps. Mean distances between dorsal process ridges of M. affinis and P. gibbicepswere approximately 50 and 160 microns, respectively. For P. gibbiceps, dominant frequency was an inverse function of total length and inter-ridge distance.

Firefighting is a very hazardous profession. Firefighters experience an injury rate that is three times higher than other physically demanding professions and the death rate in the fire service is also much higher compared to typical. Throughout the literature, data suggest the physical nature of firefighting contributes to the high incidence of injury and death among firefighters. As such, special interest groups and firefighting organizations advocate for firefighters to exercise and stay fit in order to safeguard their physical health. Yet, despite these efforts, firefighters still experience a very high incidence of back injuries and heart attacks which can lead to early retirement from disability or death. In the first aim of this dissertation, we examined the relationships between specific back fitness tests and history of back injuries in 113 firefighters in an effort to understand which fitness tests may aid in screening firefighters for risk of back injury. We found that a test of lumbar extension flexibility was associated with a higher incidence of back injuries among our sample (p<0.01). In the second aim of the study, we investigated whether perceived fitness was related to history of back injuries since firefighters’ perceptions of their fitness level may direct how they choose to perform job tasks that pose high risk for injury. Within the same sample of firefighters, we found that perceived fitness was not related to history of back injuries nor was the relationship between actual fitness and history of back injuries mediated by perceived fitness. However, perceived fitness correlated with scores on our back strength (r=0.28; p=0.003) and hamstring strength (r=0.21; p=0.03) tests. In the third aim of the dissertation, we sought to develop a treadmill walking protocol to screen firefighters for low aerobic capacity which is a major risk factor for heart attack. Thirty-eight male firefighters wore a vest weighing 20% of their body weight and performed a walking VO2max test in which the treadmill grade increased by 1% each minute. The predicted VO2max from this walking test was very accurate; within a standard error of the estimate of 3.2 ml/kg/min. This new (Moore) protocol requires only a standard treadmill and is more job specific than a running test. In conclusion, more research needs to be conducted to understand how firefighters’ perceived fitness directs their behaviors when performing job tasks and how high levels of fitness can protect against back injuries and heart attacks in firefighters. This dissertation has contributed to the development of screening protocols to aid in preventing these adverse events. / Graduation date: 2013

BACKGROUND and OBJECTIVES: Low-back overexertion injuries represent a large proportion of fireground “strains, sprains and muscular pains” and are a leading cause of disability and early retirement in firefighters. Given the inherently hazardous and unpredictable nature of many fireground activities, it is often infeasible to implement “task-focused” ergonomic controls and there are limited options to accommodate injured firefighters. Accordingly, effective and practical “worker-focused” injury prevention approaches are needed. Toward this end, four studies were conducted to address the following global thesis objectives: 1) Examine the possible role that firefighters’ personal movement strategies could have on their occupational low-back loading demands and injury potential; and 2) Compare the effects of two different exercise approaches on firefighters’ occupational low-back loading demands and injury potential. STUDY 1: Low-Back Loading Demands during Simulated Firefighting Tasks – Inter-Subject Variation and the Impact of Fatigue and Gender. Background: Non-modifiable fireground duties are considered hazardous for low-back health, but personal movement strategies could modulate low-back loading demands and injury potential. Study objectives were to quantify low-back loading demands during simulated firefighting tasks and to examine the impact of fatigue and gender on the peak loading response. Methods: Ten men and 10 women performed a battery of laboratory-simulated firefighting tasks before and following repeated bouts of a fatiguing stair-climbing protocol. An EMG-assisted three-dimensional dynamic biomechanical model was used to compute peak L4/L5 joint forces during task performance. Results: Peak low-back loading demands varied considerably between subjects and tasks, but 70% of all loading variables examined were of greater magnitudes in male subjects and 40% of all loading variables were of lower magnitudes in both males and females after stair-climbing. Some inter-subject variation in low-back loading was attributed to body size differences, but between- and within-subject differences in movement strategies also contributed to low-back loading variability between subjects and over time. Conclusions: Results of this study suggest that characteristics of individuals, tasks performed, and physical fatigue may influence peak low-back loading demands and injury potential in firefighters. Despite considerable inter-subject variation in the internal low-back loading response to fixed external task and environmental constraints, opportunities to attenuate low-back loading demands through movement behaviour adaptations alone may be limited to only a subset of fireground activities. STUDY 2: Ankle Immobilization alters Lifting Kinematics and Kinetics – Occupational Low-Back Loading Demands and Potential for Injury. Background: Firefighters with lingering lower extremity functional impairments could be forced to move in ways that increase their potential for sustaining occupational low-back lifting injuries. The study objective was to examine the impact of unilateral ankle immobilization on lifting kinematics and kinetics. Methods: With and without their right ankle immobilized, 10 male volunteers performed laboratory-simulated occupational lifting tasks. Together with force platform data, three-dimensional kinematics of the lumbar spine, pelvis, and lower extremities were collected, and a three-dimensional dynamic biomechanical model was used to calculate peak low-back compression and shear loading demands. Results: In comparison to the unaffected conditions, ankle immobilization resulted in less knee (p-values between 0.0004 and 0.0697) and greater lumbar spine (p-values between 0.0006 and 0.3491) sagittal motion when lifting. Associated with this compensatory movement strategy were greater L4/L5 anterior/posterior reaction shear forces (p-values between 0.0009 and 0.2450). However, in a few cases where individual compensatory movement strategies differed from the “group” response (i.e., subjects increased their sagittal knee and hip motion on the affected side), peak L4/L5 joint compressive loads increased while the peak L4/L5 anterior-posterior shear did not change. Conclusions: Distal lower extremity joint dysfunction can alter the way in which individuals move and load their low-backs when lifting. The specific ways in which individuals compensate for personal movement constraints could alter the potential site and mechanism of occupational low-back injury. STUDY 3: FMS™ Scores and Occupational Low-Back Loading Demands – Whole-Body Movement Screening as an Ergonomic Tool? Background: Results of Study 1 suggested that a whole-body movement screen could be used to identify personal characteristics that constrain movement behaviour in ways that impact occupational low-back loading demands and injury potential. The purpose of this study was to examine if Functional Movement Screen™ (FMS) scores could be used to project the low-back loading response to lifting. Methods: Sagittally symmetric and asymmetric laboratory-based lifting tasks were performed by 15 firefighters who scored greater than 14 on the FMS (high-scorers) and 15 size-matched low-scorers (FMS < 14). A three-dimensional dynamic biomechanical model was used to calculate low-back loading demands, and lumbar spine posture was recorded when peak low-back compression was imposed. Results: Regardless of the task performed, there were no differences in peak L4/L5 joint compression (p ≥ 0.4157), anterior/posterior reaction shear (p ≥ 0.5645), or medial/lateral reaction shear (p ≥ 0.2581) loading demands between high- and low-scorers. At the instant when peak compression force was detected, lumbar spine deviation was not different between high- and low-scorers about the lateral bend (p ≥ 0.4215), axial twist (p ≥ 0.2734), or flexion/extension (p ≥ 0.1354) axes. Conclusions: Using the previously established musculoskeletal injury prediction threshold value of 14, the composite FMS score did not project the low-back loading response to lifting. Future attempts to modify or reinterpret FMS scoring are warranted given that several previous studies have revealed links between composite FMS scores and musculoskeletal complaints. STUDY 4: Movement- vs. Fitness-Centric Exercise – Firefighter Fitness, Whole-Body Movement Qualities, and Occupational Low-Back Loading Outcomes. Background: The impact of exercise on firefighter job performance and cardiorespiratory fitness has been studied extensively, but its effect on musculoskeletal loading remains less understood. The aim of this study was to compare various physical fitness, general movement quality, and low-back loading outcomes between groups of firefighters who completed fitness- or movement-centric exercise. Methods: Fifty-four firefighters participated and were assigned to a control (CON), fitness-centric exercise (FIT), or movement-centric exercise (MOV) group. Before and after 12 weeks of exercise, subjects performed a physical fitness test battery, the Functional Movement Screen™ (FMS), and laboratory-simulated firefighting tasks during which low-back loading demands were quantified. Results: FIT and MOV subjects exhibited statistically significant improvements in nearly all measures of physical fitness (i.e., body composition, cardiorespiratory capacity, muscular strength, power, endurance, and flexibility), but FMS scores and occupational low-back loading demands were not impacted in a consistent way across individuals. Conclusions: Improving physical fitness can enhance job performance and prevent cardiac events in firefighters, but it was not clear that 12 weeks of exercise would alter their occupational low-back loading demands. Given variability in individual responses, the short study duration, and limited number and nature of tasks examined, more research incorporating alternative biomechanical and statistical analyses is needed to better understand how individuals adapt to chronic exercise and what impact these adaptations have on occupational movement behaviours, low-back loading demands, and low-back loading capacity. SUMMARY and CONCLUSIONS: Results confirmed that fireground activities are potentially hazardous for low-back health, as simulated occupational low-back loading demands routinely exceeded recommended exposure limits in the studies performed. However, results also indicated that personal movement strategies – possibly influenced by body size, preference, gender, physical fatigue, or distal lower extremity joint dysfunction – could alter occupational low-back loading demands and injury potential. It could not be concluded that occupational low-back loading demands and injury potential would be consistently affected by short-term improvements in physical fitness, nor could the low-back loading response to lifting be projected by scoring above or below 14 on the Functional Movement Screen™. Future research is warranted to examine the low-back loading demands associated with performing non-fireground duties, as opportunities may exist to implement ergonomic strategies to control cumulative low-back loading exposures. Particular attention should be paid to the exercise and training practices of firefighters, as musculoskeletal injuries sustained during these activities are potentially avoidable and could reduce the capacity of the musculoskeletal system to withstand demands imposed during non-modifiable fireground operations.

Eight out of ten people in the United States will have problems with low back pain at some point in their life. The most significant surgical treatments for low back pain can be distributed into two main groups of solutions: arthrodesis and arthroplasty. Spinal arthrodesis consists of the fusion of a degenerated functional spine unit (FSU) to alleviate pain and prevent mechanical instability. Spinal arthroplasty consists of the implantation of an artificial disc to restore the functionality of the degenerated FSU. The objective of this study is to analyze and compare the alteration of the biomechanics of the lumbar spine treated either by arthrodesis or arthroplasty. A three-dimensional finite element model of a ligamentous lumbar motion segment, constituted of two FSUs, was built and simulated through a static analysis with the finite element software ABAQUS. It was shown that the mobility of the segment treated by arthrodesis was reduced in all rotational degrees of freedom by an average of approximately 44%, relative to the healthy model. Conversely, the mobility of the segment treated by arthroplasty was increased in all rotational degrees of freedom by an average of approximately 52%. The FSU implanted with the artificial disc showed a high risk of instability and further degeneration. The mobility and the stresses in the healthy FSU, adjacent to the restored FSU in the segment treated by arthroplasty, were also increased. In conclusion, the simulation of the arthroplasty model showed more risks of instability and further degeneration, on the treated level as well as on the adjacent levels, than in the arthrodesis model.

Over the past several decades rates of spine surgeries in the U.S. have increased dramatically. Spinal fusion surgery rates, in particular, have grown exponentially despite being one of the most costly, invasive, and controversial methods for treating patients suffering from back conditions. Furthermore, lumbar fusion surgeries continue to be performed at increasing rates despite a lack of scientific evidence and consensus that they are cost-effective and produce better clinical outcomes than less radical treatment of lower back pain. As a result, large amounts of healthcare dollars continue to be invested in these costly procedures which are potentially dangerous and have questionable efficacy in terms of improving patient outcomes. Importantly, there is a lack of population studies in the literature on spinal fusion surgeries from a health services research perspective. Therefore, the present research is a population based study using an administrative database and includes patients of all ages and payer types. The data used in the present study come from the Florida Agency for Health Care Administration (AHCA) and include all hospitalizations in Florida in 2010. The objective of the study is to analyze the incidence of spinal fusion surgeries in Florida hospitals for patients of all ages and payer types by demographic variables to understand who gets these surgeries and for which conditions. The first null hypothesis is that there are no statistically significant predictors of the incidence of lumbar/lumbosacral, dorsal/dorsolumbar spinal fusion surgeries in Florida hospitals. Logistic regression was used to analyze the incidence of fusion surgeries. The binary dependent variable was coded as a "1" for all patients who were a case (i.e. they received one of the five procedure codes being studied in the present research) and a "0" for all patients who were controls (meaning they did not receive any of the five fusion procedure codes). Logistic regression was used to predict the probability of an observation being a "1" given the independent variables included in the model. Additionally, hospital charges were analyzed to understand the associated hospital charges with these surgeries. The second null hypothesis is that there are no statistically significant predictors of the charges of Lumbar/Lumbosacral, Dorsal/Dorsolumbar spinal fusion surgeries in Florida Hospitals. A mixed effects model was used to test this hypothesis and the fixed effects which were included in the model were gender, age, race, principal payer, and principal procedure. A mixed effects model was chosen due to the fact that cases who had surgeries performed at the same hospital are not independent and therefore the data were clustered on hospitals. A random intercept term was used to address this fact. SAS software was used to complete all of the analyses. In 2010, there were 16,236 Lumbar/Lumbosacral, Dorsal/Dorsolumbar fusion surgery cases in Florida hospitals that were included in the case population and 21,856 individuals included in the control population for a total of 38,092 included in the study population. An understanding of who is most likely to receive a fusion surgery, at what age, and for which diagnoses, as has been done here, is extremely important. This knowledge can help researchers, policy makers, and physicians alike. Comprehensive physician practice guidelines for performing fusion surgeries still do not exist in the year 2013; therefore, in order to have the greatest impact, the efforts for creating the guidelines should be focused on those individuals who are most likely to receive fusions as shown for the first time by the data analyzed here. Given the high incidence of these surgeries in Florida alone, the need for practice guidelines cannot be overstated. The total hospital charges in Florida hospitals for the 16,236 cases were $2,095,413,584. Despite having the same principal diagnoses and a similar number of additional diagnoses, patients who received a fusion surgery resulted in approximately three times the charges as those incurred by the controls. Overall, the high incidence and charges for fusion surgeries shown in this study emphasize the importance of having a better understanding of when these surgeries are justified and for which patients. Without comprehensive practice guidelines established through evidence-based research this is difficult, if not impossible, to accomplish. The diagnoses which are most prevalent and show the most inconsistencies between cases may be a good starting point for such guidelines.

Background Spinal pain is one of humanity’s most frequent complaints with high costs for the individual and society, and is commonly related to spinal disorders. There are many origins behind these disorders e.g., trauma, disc hernia or of other organic origins. However, for many of the disorders, the origin is not known. Thus, more knowledge is needed about how pain affects the neck and neural function in pain affected regions. The purpose of this dissertation was to improve the medical examination of patients suffering from chronic whiplash-associated disorders or other pain related neck-disorders. Methods A new assessment tool for objective movement analysis was developed. In addition, basic aspects of proprioceptive information transmission, which can be of relevance for muscular tension and pain, are investigated by studying the coding of populations of different types of sensory afferents by using a new spike sorting method. Both experiments in animal models and humans were studied to accomplish the goals of this dissertation. Four cats where were studied in acute animal experiments. Mixed ensembles of afferents were recorded from L7-S1 dorsal root filaments when mechanical stimulating the innervated muscle. A real-time spike sorting method was developed to sort units in a multi-unit recording. The quantification of population coding was performed using a method based on principal component analysis. In the human studies, 3D neck movement data were collected from 59 subjects with whiplash-associated disorders (WAD) and 56 control subjects. Neck movement patterns were identified by processing movement data into parameters describing the rotation of the head for each subject. Classification of neck movement patterns was performed using a neural network using processed collected data as input. Finally, the effect of marker position error on the estimated rotation of the head was evaluated by computer simulations. Results Animal experiments showed that mixed ensembles of different types of afferents discriminated better between different muscle stimuli than ensembles of single types of these afferents. All kinds of ensembles showed an increase in discriminative ability with increased ensemble size. It is hypothesized that the main reason for the greater discriminative ability might be the variation in sensitivity tuning among the individual afferents of the mixed ensemble will be larger than that for ensembles of only one type of afferent. In the human studies, the neural networks had a predictivity of 0.89, a sensitivity of 0.90 and a specificity of 0.88 when discriminating between control and WAD subjects. Also, a systematic error along the radial axis of the rigid body added to a single marker had no affect on the estimated rotation of the head. Conclusion The developed spike sorting method, using neural networks, was suitable for sorting a multiunit recording into single units when performing neurophysiological experiments. Also, it was shown that neck movement analysis combined with a neural network could build the basis of a decision support system for classifying suspected WAD or other pain related neck-disorders.

Η διενέργεια εμβιομηχανικών μελετών σε μοντέλο με τη βοήθεια ηλεκτρονικών υπολογιστών βρίσκεται σήμερα σε προχωρημένο στάδιο εξέλιξης. Σε αυτή την εξέλιξη κεντρική θέση κατέχουν λογισμικά δύο κατηγοριών. Στην πρώτη κατηγορία κατατάσσονται τα λογισμικά εμβιομηχανικής προσομοίωσης του ανθρωπίνου σώματος και στη δεύτερη κατηγορία τα λογισμικά ανάλυσης πεπερασμένων στοιχείων. Σε αυτή τη Μεταπτυχιακή Εργασία έγινε μία προσπάθεια διερεύνηση της συνεργασίας των δύο αυτών κατηγοριών λογισμικού με την κινηματική μελέτη ενός οσφυϊκού σπονδύλου και την ανάλυση φορτίσεών του με την μέθοδο των πεπερασμένων στοιχείων. Για αυτό το λόγο επιλέχτηκαν δύο λογισμικά εμπορικά διαθέσιμα. Το λογισμικό εμβιομηχανικής προσομοίωσης Anybody modeling system και το λογισμικό ανάλυσης πεπερασμένων στοιχείων Ansys multiphysics. Στο Πρώτο κεφάλαιο γίνεται παρουσίαση του λογισμικού Anybody. Πιο συγκεκριμένα. αναφέρονται τα στοιχεία εκείνα που υλοποιούν ένα μοντέλο του ανθρώπινου σώματος (τμήματα, αρθρώσεις, μύες, σύνδεσμοι) καθώς και οι μελέτες που μπορούν να εκτελεστούν δηλαδή η κινηματική και η δυναμική. Κύρια θέση κατέχει η αντιστροφή δυναμική μελέτη που χαρακτηρίζεται από την εξαγωγή συμπερασμάτων για τις δυνάμεις και τις ροπές που αναπτύσσονται σε ένα σώμα αφού έχει περιγραφεί εκ των προτέρων η κίνησή του. Στο Δεύτερο κεφάλαιο γίνεται μια λεπτομερής περιγραφή της ανατομίας της σπονδυλικής στήλης στην οποία αναφέρονται τα επιμέρους κοινά στοιχεία που έχουν οι σπόνδυλοι καθώς κου οι διαφορές στις διαφορετικές μοίρες της σπονδυλικής στήλης. Μετά την ανατομική περιγραφή παρατίθεται η εμβιομηχανική θεώρηση της κατασκευής της οσφυϊκής μοίρας της σπονδυλικής στήλης, αναλύοντας τα επιμέρους δομικά στοιχεία από μηχανική άποψη και η λειτουργικότητά τους. Στο Τρίτο κεφάλαιο περιγράφεται η κατασκευή ενός μοντέλου της σπονδυλικής στήλης στο λογισμικό Anybody το οποίο υποβάλλεται σε κινήσεις κάμψης, έκτασης, πλάγιας κάμψης και στροφής και επιχειρείται ο σχολιασμός των ευρημάτων. Τέλος, στο τέταρτο κεφάλαιο τα δεδομένα τα οποία παράγει η αντίστροφή μελέτη και συγκεκριμένα οι φορτίσεις που δέχεται ο Ο5 σπόνδυλος κατά τις κινήσεις στις οποίες υποβάλλεται η οσφυϊκή μοίρα χρησιμοποιούνται ως δεδομένα εισόδου για την ανάλυση του Ο5 σπόνδυλο με το λογισμικό μηχανικής ανάλυσης πεπερασμένων στοιχείων ANSYS. Συνοψίζοντας, η συνεργασία των δύο λογισμικών αποδείχθηκε εφικτή και πρόσφορη. Στην παρούσα μεταπτυχιακή εργασία αναπτύχθηκε η βασική τεχνογνωσία ως προς την χρήση του λογισμικού Anybody Modeling System και την συστηματοποίηση της διασύνδεσης του με το λογισμικό Ansys με αποτέλεσμά να αποτελεί την βάση για περαιτέρω εργασίες. / The conduction of biomechanical studies on models with the aid of computers is currently at an advanced stage. In this essay, the central position is hold by two software categories. In the first category are classified various software of biomechanical simulation of the human body and in the second category are classified the software for the finite element analysis. In this Master Thesis was made an attempt to explore the cooperation of these two kinds of software. For this reason, two commercially available softwares were selected. The biomechanical simulation was performed using the Anybody Modeling System software and the finite element analysis was performed using the Ansys Multiphysics software. In the first chapter the use of the Anybody software was presented. More specifically, those elements that implement a model of the human body (segments, joints, muscles, ligaments) as well as studies that can be performed i.e. the kinematics and dynamics studies were discussed in details. The inverse dynamics study has been characterized as the main feature of the software allowing to explore the resulting forces and torques developed in a body during the in advance described movement. The second chapter includes a detailed description of the anatomy of the spine. After the anatomical description the biomechanical approach is presented, analyzing each individual component from engineering point of view as well as their functionality. The third chapter describes the construction of a model of the spine in the Anybody software that is subjected to flexion, extension, lateral bending and rotation along with the results. Finally, in the fourth chapter the data that produces the inverse study namely the loads applied to the L5 vertebra during each movement performed by the lumbar spine are used as input data for the mechanical analysis of L5 vertebra with the finite element analysis software ANSYS. As a conclusion, the collaboration of these two software programmes proved to be feasible and appropriate. In this master thesis the basic knowledge in the use of software Anybody Modeling System has been developed and an interface with the software Ansys has been built thus forming the basis for further work.