The neuromuscular response to prolonged lumbar flexion has recently been extensively studied in felines but has not been examined in humans. Animal studies suggest that prolonged lumbar flexion disturbs neuromuscular control of paraspinal muscles. This disturbance was linked to creep deformation of passive spinal tissues. Past research indicates that disturbance of paraspinal reflexes may limit spinal stability. The current study aimed to examine this behavior in humans. We hypothesized that prolonged lumbar flexion will disturb paraspinal reflex behavior in human subjects. Reflex behavior was quantified following a fifteen minute period of static flexion. There was a trend suggesting an increase in reflex magnitude after flexion (p = 0.055). This trend was only significant in female subjects (p < 0.003). Increased reflex following flexion was associated with a transient period of EMG hyperexcitability similar to felines. A second study was performed to quantify reflex behavior and creep deformation during flexion and recovery. Results indicated that creep occurred during prolonged flexion (p < 0.001). Reflexes were inhibited following flexion (p < 0.03). Both creep deformation and paraspinal reflex (p > 0.05) failed to exhibit significant recovery during the length of the test. Inhibited paraspinal reflexes may contribute to spinal instability and risk of low back pain for workers using flexed postures, due to the inability of the neuromuscular system to coordinate an appropriate muscle response following an unexpected loading event. Future studies must examine appropriate work/rest intervals for workers using flexed postures to limit reflex disturbance from prolonged ligament strain. / Master of Science

Falls from heights are the fourth leading cause of occupational injury and fatality in the United States. In particular, construction workers such as roofers are often exposed to high risk environments. Recent research has reported that a leading cause of falls among workers is a loss of balance. Therefore, in moving towards reducing the number of occupational falls, further investigation of balance and factors that influence postural control is necessary. The effect of neuromuscular fatigue has been addressed by many investigators; however, few studies have examined the effect of localized fatigue in muscles not located in the lower extremities. Because low back fatigue is so prevalent during manual labor, this investigation determined to study the effects of lumbar extensor fatigue on balance. Chapter 1 includes a complete review of current literature addressing the effects of muscular fatigue on measures of balance. Chapter 2 details an initial investigation of lumbar extensor fatigue on center of pressure (COP) based measures of postural sway and examines the effect of fatiguing rate. Chapter 3 examines the effects of different levels of lumbar extensor fatigue and expands on the previous investigation by examining center of mass (COM) movement and incorporating additional measures of postural control. The results of these investigations indicate that lumbar extensor fatigue affects both COP and COM measures of postural sway, and might also lead to an increased reliance on feedforward postural control mechanisms. These findings contribute to understanding of effects of fatigue on balance and may aid the future design of interventions aimed at fall prevention. / Master of Science

Thesis (MMed (Surgical Sciences. Orthopaedic Surgery))--University of Stellenbosch, 2010. / Objective: This research paper reports on the radiographic outcome of unstable thoracolumbar injuries with short segment posterior instrumentation as standalone treatment; in order to review rate of instrumentation failure and identify possible contributing factors. Background: Short segment posterior instrumentation is the treatment method of choice for unstable thoracolumbar injuries in the Acute Spinal Cord Injury Unit (Groote Schuur Hospital). It is considered adequate treatment in fracture cases with an intact posterior longitudinal ligament, and Gaines score below 7 (Parker JW 2000); as well as fracture dislocations, and seatbelt-type injuries (without loss of bone column - bearing integrity). The available body of literature often states instrumentation failure rates of up to 50% (Alanay A 2001, Tezeren G 2005). The same high level of catastrophic hardware failure is not evident in the unit researched. Methods: Sixty-five consecutive patients undergoing the aforementioned surgery were studied. Patients were divided into two main cohorts, namely the “Fracture group” (n=40) consisting of unstable burst fractures and unstable compression fractures; and the “Dislocation group” (n=25) consisting of fracture dislocations and seatbelt-type injuries. The groups reflect similar goals in surgical treatment for the grouped injuries, with reduction in loss of sagittal profile and maintenance thereof being the main aim in the fracture group, appropriately treated with Schantz pin constructs; and maintenance in position only, the goal in the dislocation group, managed with pedicle screw constructs. Data was reviewed in terms of complications, correction of deformity, and subsequent loss of correction with associated instrumentation failure. Secondly, factors influencing the aforementioned were sought, and stratified in terms of relevance. Results: Average follow up was 278 days for the fracture group and 177 days for the dislocation group (all patients included were deemed to have achieved radiological fusion – if fusion technique was employed). There was an average correction in kyphotic deformity of 10.25 degrees. Subsequent loss in sagittal profile averaged 2 degrees (injured level) and 5 degrees (thoracolumbar region) in the combined fracture and dislocation group. The only factor showing a superior trend in loss of reduction achieved was the absence of bone graft (when non-fusion technique was employed). Instrumentation complications occurred in two cases (bent connection rods in a Schantz pin construct with exaggerated loss in regional sagittal profile, and bent Schantz pins). These complications represent a 3.07% hardware failure in total. None of the failures were considered catastrophic. Conclusion: Short segment posterior instrumentation is a safe and effective option in the treatment of unstable thoracolumbar fractures as a standalone measure.

Neuroplasticity has been researched in many different ways, from the growing neonatal brain to neural responses to trauma and injury. According to recent research, neuroplasticity is also prevalent in the ability of the brain to repurpose areas that are not of use, like in the case of a loss of a sense. Specifically, behavioral studies have shown that deaf humans (Bavalier and Neville, 2002) and cats have increased visual ability, and that different areas of the auditory cortex enhance specific kinds of sight. One such behavioral test demonstrated that the dorsal zone (DZ) of the auditory cortex enhances sensitivity to visual motion through cross-modal plasticity (Lomber et. al., 2010). Current research seeks to examine the anatomical structures responsible for these changes through analysis of excitatory neuron dendritic spine density and spine head diameter. This present study focuses on the examination of DZ neuron spine density, distribution, and size in deaf and hearing cats to corroborate the visual changes seen in behavioral studies. Using Golgi-stained tissue and light microscopy, our results showed a decrease in overall spine density but slight increase in spine head diameter in deaf cats compared to hearing cats. These results, along with several other studies, support multiple theories on how cross-modal reorganization of the auditory cortex occurs after deafening

Sex differences in bone mass and size are thought to contribute to the greater incidence of vertebral fractures in women. While these sex differences are widely recognized, the relative contributions of bone mass, bone density, and bone size to the differences in vertebral strength and fracture risk between men and women have not been fully delineated. Furthermore, it is unknown whether the roles of each of these factors in determining vertebral strength change differently with age in men and women. We studied the bone content, density and geometry as well as vertebral loading and the factor of risk of the L3 vertebra in a sample of prepubertal males and females. Our first aim was to assess differences in vertebral bone dimensions, bone density, vertebral loading patterns and fracture risk, as measured by the factor of risk, in prepubertal children. Our second aim was to determine whether pre-pubertal growth affects the geometry and density of L3 differently in boys and girls. We measured vertebral dimensions, cross-sectional area and volumetric BMD of the third lumbar vertebral body in 93 prepubertal children (54 boys and 39 girls), using dual-energy X-ray absorptiometry scans obtained in the posterior-anterior and lateral projections. We also employed basic biomechanics to estimate vertebral loading during upright standing and forward bending. Bone strength and loading data were used to assess sex differences in the factor of risk in prepubertal children. Twenty children (11 boys and 9 girls) were assessed at baseline and seven months later to examine the effects of growth on bone size and vBMD. At baseline, boys and girls were similar for age, height, weight and calcium intake. L3 width and depth were 6.7% and 5.8% greater in boys than girls, respectively (P<0.001 and P=0.01, respectively). In contrast, vertebral height was 3.5% greater in girls than boys (P= 0.04). While vertebral loading was similar between sexes, stresses on the spine were 12.2% lower in boys during upright standing and 12.0% lower in boys during forward bending at both 50° and 90°, as compared to girls (P<0.001, P<0.01 and P<0.01, respectively). The factor of risk was similar between boys and girls under each loading condition. During growth, changes in vertebral size and density were not different between boys and girls. Our results indicate that even prior to puberty, sex differences in vertebral size contribute to differences in vertebral stress during standing and forward bending. Furthermore, before the onset of puberty, growth does not result in disparate changes between sexes. / Graduation date: 2004

There have been many advances in surgical residency education and similar interest exists in fellowship education. This study evaluated perceptions among spine surgeons about the specific competencies required for successful spine surgical fellowship training, and then compared these perceptions to clinical practice. Firstly, a questionnaire was administered to spine fellow trainees and academic spine surgeons across Canada in order to identify the cognitive and technical skills required for successful spine fellowship training. Fellowship trainees and supervisors had similar perceptions on the relative importance of specific cognitive and technical competencies. Differences in perceptions were found when comparing surgeons based on background residency specialty training (orthopaedic surgical or neurosurgical). Secondly, using administrative data, a retrospective study assessed volumes, surgeon characteristics, and outcomes for surgery of the degenerative lumbar spine in Ontario between 1995 and 2001. Neurosurgeons were found to perform more decompressions, and more total procedures, than orthopaedic surgeons with similar outcomes.

There have been many advances in surgical residency education and similar interest exists in fellowship education. This study evaluated perceptions among spine surgeons about the specific competencies required for successful spine surgical fellowship training, and then compared these perceptions to clinical practice. Firstly, a questionnaire was administered to spine fellow trainees and academic spine surgeons across Canada in order to identify the cognitive and technical skills required for successful spine fellowship training. Fellowship trainees and supervisors had similar perceptions on the relative importance of specific cognitive and technical competencies. Differences in perceptions were found when comparing surgeons based on background residency specialty training (orthopaedic surgical or neurosurgical). Secondly, using administrative data, a retrospective study assessed volumes, surgeon characteristics, and outcomes for surgery of the degenerative lumbar spine in Ontario between 1995 and 2001. Neurosurgeons were found to perform more decompressions, and more total procedures, than orthopaedic surgeons with similar outcomes.

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Background: Clinical ergonomic advice for sitting posture has been inferred from anthropometry theory and physiology studies. Qualitative observation of posture has been used to argue that postures are too flexed, too extended, too static, too mobile, require insufficient muscle activity or require too much. In other fields of healthcare, evidence is progressed from basic science to clinical trials before an intervention is prescribed, but postural advice has been prescribed from basic science without quantitative studies of postural behaviour. Spinal neuromuscular control can predict development of low back pain, it is affected by spinal pain, and can be trained, but studies examining these variables rarely measure the spinal position of their test subjects. There is a need for more detail of how spinal positions affect regional muscle activity. Study Objectives: The overall aims of this thesis were to quantify sagittal spinal postures in sitting for comparison within and between subjects and tasks, and to detail paraspinal and abdominal muscle activity associated with sitting postures. The studies quantified regional spinal curves in - Study I: typical posture behaviour during a computer task in comparison with standing, - Study II: postures that are achievable in sitting, - Study III: the regional muscle activity associated with sitting postures that have been clinically advocated as ‘ideal’, - Study IV: cohorts with and without a history of low back pain for comparison of regional muscle activity. Results and Conclusions: For clinical trials quantifying postural behaviour, the postural variation within subjects and task conditions in Study I demonstrated the importance of measurement over a prolonged period and subjects performing relevant tasks (as opposed to brief measures such as radiography that have been the standard for posture assessment). The use of surface tracking to quantify regional spinal curves and sagittal balance establish a foundation to investigate the effect of interventions on posture behaviour (eg. chair geometry, posture training, task variables and subject cohorts). Study I also showed that typical sitting posture for a computer task was more flexed at the thoracolumbar spinal region than when subjects deliberately ‘corrected’ their sitting posture, and both sitting postures were flexed at the lumbar region relative to standing. Study II showed that most subjects were unable to sit with spinal curves like those adopted in standing unless facilitation and feedback were provided, although these curves have been clinically advocated as ‘ideal’ posture. If clinical theories about ‘ideal’ sitting posture are correct, then teaching individuals the awareness of spinal position or skill to adopt these postures could be as important for workplace health and safety as other variables such as design and adjustment of office furniture. Study III showed three upright sitting postures that have been clinically advocated as ‘ideal’ were distinguished by incremental changes in activity of the lumbar multifidus muscles. In Study IV, individuals with a history of low back pain showed more incremental activity at the longissimus thoracis muscle to achieve the same sitting postures. If particular postures are shown to be ‘ideal’ in clinical trials, then training for these postures may need to focus on muscular strategies as well as spinal position. The distinct differences in regional muscle activity observed with spinal curves and subject cohorts (Studies III and IV) imply that studies of spinal neuromuscular control should measure or control spinal curves during testing. If spinal posture were controlled, the flat posture (flat surface from ~T5 to sacrum) would have the advantages of being achievable, commonly used in sitting and easily assessed. The flat posture also demonstrated the lowest muscle activity of the upright sitting postures examined, which may improve accuracy of determining muscle activity onset/offset used as an outcome measure for interventions, distinguishing cohorts or as a predictor for low back pain occurrence.