The need for the development of a rigorous analytical model of the lumbar spine to clarify the role of mechanical factors in low-back disorders has long been recognized. In response to this need, a general three dimensional nonlinear finite element program has been developed as part of this work and has been applied to the analysis of a lumbar L(,2-3) joint including the posterior elements. The analysis accounts for both the material and geometric nonlinearities and is based on a representation of the nucleus as an incompressible inviscid fluid and of the annulus as a composite of collagenous fibres embedded in a matrix of ground substance. The facet articulation has been accounted for by treating it as a general moving contact problem. The ligaments have been modelled as a collection of nonlinear axial elements. The geometry of the finite element model is based on in-vitro measurements. / The response of the joint under single compression, single flexion, single extension and also under flexion or extension combined with compression and sagittal shear has been analyzed for both the normal and degenerated states of the nucleus. Validity of the model has then been established by a comparison of those predictions which are also amenable to direct measurements. The states of strain and stress in different components of the lumbar joint have been thoroughly studied under all the foregoing loading conditions. / Those elements of the joint predicted to be vulnerable to mechanical failure or damage under the above types of loading have been identified. These results have been correlated with the lumbar joint injuries reported clinically. Furthermore, some joint injury mechanisms and degeneration processes have been proposed and the supporting clinical evidences have been presented.

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Spinal adaptive response in the frontal plane was investigated in relationship to pelvic unleveling during gait. Kinematic data were collected from 10 healthy adult subjects (5 male, 5 female) for walking and running on the treadmill at self-selected speeds. Spine and pelvic kinematic patterns and ranges of motion (ROM) were investigated with gender, speed and slope as factors. Speed and slope had the greatest impact on changes in the amplitude of the spine's kinematic patterns. Interaction effects were seen for speed and slope for the ROM, particularly of the greater trochanter (p < .047), PSIS (p < .011) and for the shoulders (p < 0.077). Gender presented more changes in the pelvic kinematics than the spine's kinematics. A significant trend in the females of greater ROM for T8 with increases in speed and slope was shown (p < 0.001). From this study it was concluded that speed, slope and gender were significant factors that affect the spine's ability to adapt to pelvic unleveling. In all conditions there was a coupled relationship found between the thoracic spine, lumbar spine and pelvis. In particular there was an oppositional movement found within the spine such that as the lumbar spine had convexity towards the swing leg then the thoracic spine had the opposite convexity. Hence, these factors are important when assessing posture and biomechanics of running and walking.

Aims: The primary physiotherapeutic aims of the study were to validate a manual physiotherapy evaluation technique in the assessment of cervical biomechanical dysfunction, and to test the effectiveness of a manual physiotherapy treatment technique in the correction of cervical biomechanical dysfunction. The primary educational aims were to test the effectiveness and safety of a therapeutic exercise programme for the correction of biomechanical dysfunction as well as the effectiveness of a neck rehabilitation programme for improving neck muscle strength. Design: A four group experimental design with three pre-test - post-test groups and a control group was used for the investigation. Sample: The subjects were South African schoolboy rugby players between the ages of 15 and 18 years. Groups I and 2 presented with biomechanical dysfunction of their cervical spines, Group 3 had no biomechanical dysfunction of their cervical spines and the players of Group 4, the control group, presented with or without biomechanical dysfunction of their cervical spines. Each group consisted of 25 players. Method: Group I received manual physiotherapy with x-rays before and after treatment. Groups 2 and 3 performed a therapeutic exercise programme, with before and after x-rays, and Group 4 received no intervention between their sets of x-rays. Following the second set of x-rays all the players from Groups I, 2 and 3 performed the neck rehabilitation programme after which a third set of x-rays were taken. Results: The results validated the manual physiotherapy evaluation technique. The manual therapy treatment technique used in the treatment of Group I showed highly significant improvements in cervical biomechanical function. Results for Group 2 following the therapeutic exercise programme showed moderate practically significant improvements in cervical biomechanical dysfunction. The therapeutic exercise programme for the correction of biomechanical dysfunction was found to be very safe with only small significant changes in x-ray measurements (Group 3). The results of the control group showed a negative trend of small statistical significance. A highly significant improvement in cervical circumference as moderate significant improvement in biomechanical function was found following the neck rehabilitation programme. Conclusion: It could therefore be concluded that the manual physiotherapy evaluation technique for motion segment analysis was indeed valid in determining biomechanical dysfunction of the cervical spine. The manual physiotherapy treatment technique as well as the therapeutic exercise programme for the correction of biomechanical dysfunction was found to be effective in the correction of cervical biomechanical dysfunction. It could further be concluded that the therapeutic exercise programme was safe to be performed by players without biomechanical dysfunction. The neck rehabilitation programme was effective in improving cervical circumference as well as cervical biomechanical function. / Thesis (Ph.D. (Education))--North-West University, Potchefstroom Campus, 2005.

This study is a prospective longitudinal outcome study investigating the presence of response shift in disease and generic functional outcome measures in 105 patients undergoing spinal surgery. The then-test method which compares pre-test scores to retrospective pre-test scores was used to quantitate response shift. There was a statistically significant response shift for the Oswestry Disability Index (ODI) (p=0.001) and the Short Form-36-PCS (p=0.078). At three months, seventy-two percent of patients exhibited a response shift with the ODI. Fifty-six and 21 percent of patients exhibited a response shift with the SF-36 physical and mental component scores respectively. When accounting for response shift and using the minimal clinically important difference, the success rate of the surgery at 3 months increased by 20 percent. The presence of response shift has implications for the measurement properties of standard spinal surgery outcome measures including the effect size of treatment and the number of responders to treatment.

Recent studies have demonstrated that an acute, low dose of ketamine, a non-competitive NMDA receptor antagonist, provides rapid and sustained antidepressant effects in patients with major depressive disorder. Studies in rodents have shown that the antidepressant properties of ketamine are due to an increase in dendritic spine density in the cortex. Our goal was to determine whether these effects are specific to ketamine and whether they are dependent on dose, drug regimen and brain region. We observed that the effects of ketamine on spine density were dependent on dose and drug regimen and were also brain region specific. In addition, MK-801, another NMDA receptor antagonist, did not demonstrate the same effects on spine density as ketamine. Furthermore, genetic NMDA receptor hypofunction significantly reduced spine density. Our studies demonstrate that while acute ketamine treatment leads to an increase in cortical spine density, chronic administration has opposite and potentially detrimental effects.

This study is a prospective longitudinal outcome study investigating the presence of response shift in disease and generic functional outcome measures in 105 patients undergoing spinal surgery. The then-test method which compares pre-test scores to retrospective pre-test scores was used to quantitate response shift. There was a statistically significant response shift for the Oswestry Disability Index (ODI) (p=0.001) and the Short Form-36-PCS (p=0.078). At three months, seventy-two percent of patients exhibited a response shift with the ODI. Fifty-six and 21 percent of patients exhibited a response shift with the SF-36 physical and mental component scores respectively. When accounting for response shift and using the minimal clinically important difference, the success rate of the surgery at 3 months increased by 20 percent. The presence of response shift has implications for the measurement properties of standard spinal surgery outcome measures including the effect size of treatment and the number of responders to treatment.

Recent studies have demonstrated that an acute, low dose of ketamine, a non-competitive NMDA receptor antagonist, provides rapid and sustained antidepressant effects in patients with major depressive disorder. Studies in rodents have shown that the antidepressant properties of ketamine are due to an increase in dendritic spine density in the cortex. Our goal was to determine whether these effects are specific to ketamine and whether they are dependent on dose, drug regimen and brain region. We observed that the effects of ketamine on spine density were dependent on dose and drug regimen and were also brain region specific. In addition, MK-801, another NMDA receptor antagonist, did not demonstrate the same effects on spine density as ketamine. Furthermore, genetic NMDA receptor hypofunction significantly reduced spine density. Our studies demonstrate that while acute ketamine treatment leads to an increase in cortical spine density, chronic administration has opposite and potentially detrimental effects.

Approximately 80% of the population will experience low-back pain within their lifetime. Significant research efforts have focused on compressive loading as an injury mechanism that could lead to low-back pain and injury. However, the influence of shear loading, and its relationship to vertebral tissue tolerances as well as modulating factors for these tolerances have not been studied as extensively. The primary objective of this thesis was to produce a series of investigations that begin to determine the roles of different modulating factors such as posture, compression, bone density, bone morphology, and repetitive load magnitude on measured vertebral joint shear failure tolerances. The thesis comprises four independent studies using in vitro mechanical testing, imaging modalities, and finite element modeling. Each of the in vitro studies within this thesis used a validated porcine cervical model as a surrogate for the human lumbar spine. The first study employed in vitro mechanical testing to investigate the combined roles of flexion/extension postural deviation and compressive load on the measured ultimate shear failure tolerances. Peripheral quantitative computed tomography scans of the pars interarticularis and measurements of vertebral bone morphology were used in the second investigation along with in vitro mechanical testing to identify the morphological characteristics that can be used to predict ultimate shear failure tolerances. The influence of sub-maximal shear load magnitude on the cumulative shear load and number of loading cycles sustained prior to failure were investigated with in vitro mechanical testing in the third study. Finally, a finite element model of the porcine C3-C4 functional spinal unit was used to investigate the plausibility of hypotheses, developed from previous research and the findings of the first investigation for this thesis, surrounding alterations in measured ultimate shear failure tolerances as a function of changes in facet interaction. Results from the first investigation showed that there was no statistically significant interaction between postural deviation and compressive force on ultimate shear failure tolerance. However, ultimate shear failure tolerance was reduced (compared to neutral) by 13.2% with flexed postures, and increased (compared to neutral) by 12.8% with extended postures. Each 15% increment (up to a maximum of 60% of predicted compressive failure tolerance) in compressive force was met with an average 11.1% increase in ultimate shear failure tolerance. It was hypothesized that alterations in flexion/extension posture and/or compressive force altered the location for the force centroid of facet contact. These changes in the location of facet contact were hypothesized to produce subsequent changes in the bending moment at the pars interarticularis that altered the measured ultimate shear failure tolerance. The three leading factors for calculating of measured ultimate shear failure tolerance were the pars interarticularis length for the cranial vertebra, the average facet angle measured in the transverse plane, and cortical bone area through the pars interarticularis. A bi-variate linear regression model that used the cranial vertebra’s pars interarticularis length and average facet angle as inputs was developed to nondestructively calculate ultimate shear failure tolerances of the porcine cervical spine. Longer pars interarticularis lengths and facets oriented closer to the sagittal plane were associated with higher measured ultimate shear failure tolerances. Fractures observed in this investigation were similar to those reported for studies performed with human specimens and also similar to reported spondylolitic fractures associated with shear loading in humans. This provided additional evidence that the porcine cervical spine is a suitable surrogate in vitro model for studying human lumbar spine mechanics. Altered sub-maximal shear load magnitude create a non-linear decrease in both the number of cycles and the cumulative shear load sustained prior to failure. These findings suggested that estimates of cumulative shear load should assign greater importance to higher instantaneous shear loads. This was due to an increased injury potential at higher instantaneous shear loads. Cumulative load sustained prior to failure was used to develop a tissue-based weighting factor equation that would apply nonlinearly increased weight to higher shear load magnitudes in estimates of cumulative shear load. A finite element model of the porcine C3-C4 functional spinal unit was created, and simulations were performed using similar boundary conditions as the comparable in vitro tests, to assess the plausibility of the moment arm hypothesis offered within the first investigation of this thesis. Moment arm length between the force centroid of facet contact and the location of peak stress within the pars interarticularis was increased for flexed postures and decreased for extended postures. Alterations in moment arm length were larger for postural deviation than compressive force, suggesting a secondary mechanism to explain the observed increase in shear failure tolerance with higher compressive loads from the first investigation. One such possibility was the increase in the number of contacting nodes with higher compressive forces. Alterations in moment arm length were able to explain 50% of the variance in measured ultimate shear failure tolerances from the first study. Thus, the finite element model was successful in demonstrating the plausibility of moment arm length between the force centroid of facet contact and the pars interarticularis as a modulator of measured ultimate shear failure tolerance. This thesis has developed the basis for understanding how failure of the vertebral joint exposed to shear loading can be modulated. In particular, this thesis has developed novel equations to predict the ultimate shear failure tolerance measured during in vitro testing, and to determine appropriate weighting factors for sub-maximal shear forces in calculations of cumulative shear load. Evidence presented within this thesis also provides support for the long-standing moment arm hypothesis for modulation of shear injury potential.

Cervical spine injury can range from minor to severe or fatal, where severe injuries can result in incomplete or complete quadriplegia. There are close to 45,000 Canadians currently affected by paralysis due to traumatic spinal cord injury (tSCI) with an estimated 1700 new cases each year. The majority of tSCI occur in automotive collisions, and current methods for injury prediction are limited to predicting the likelihood for occupant injury but lack the detail to predict the specific injury and location at the tissue level. This research focused on major injuries associated with high impact automotive collisions such as rollover type collisions. Although whiplash is an injury commonly associated with automotive collisions, it was not considered for this study based on the low risk of neurological impairment. The goal of this study was to develop a cervical spine segment finite element model capable of predicting severe injuries such as ligament tears, disc failure, and bone fracture. The segment models used in this study were developed from previous cervical spine segment models representative of a 50th percentile male. The segment models included the vertebrae, detailed representations of the disc annulus fibres and nucleus, and the associated ligaments. The original model was previously verified and validated under quasi-static loading conditions for physiological ranges of motion. To accomplish the objectives of this research, the original models were modified to include updated material properties with the ability to represent tissue damage corresponding to injuries. Additional verification of the model was required to verify that the new material properties provided a physically correct response. Progressive failure was introduced in the ligament elements to produce a more biofidelic failure response and a tied contact between the vertebral bony endplates and the disc was used to represent disc avulsion. To represent the onset of bone fracture, a critical plastic strain failure criterion was implemented, and elements exceeding this criterion were eroded. The changes made to the material models were based on experimental studies and were not calibrated to produce a specific result. After verifying the modifications were implemented successfully, the models were validated against experimental segment failure tests. Modes of loading investigated included tension, compression, flexion, extension and axial rotation. In each case, the simulated response of the segment was evaluated against the average failure load, displacement at failure, and the observed injuries reported in the experimental studies. Additionally, qualitative analysis of elevated stress locations in the model were compared to reported fracture sites. Overall, the simulations showed good agreement with the experimental failure values, and produced tissue failure that was representative of the observed tissue damage in the experimental tests. The results of this research have provided a solid basis for cervical spine segment level injury prediction. Some limitations include the current implementation of bone fracture under compressive loads, and failure within the annulus fibrosus fibres of the disc should be investigated for future models. In addition to material model modifications, further investigation into the kinetics and kinematics of the upper cervical spine segment are important to better understand the complex interactions between the bone geometry and ligaments. This would give insight into the initial positioning and expected response in subsequent models. Future research will include integrating the current segment-level failure criteria into a full cervical spine model for the purpose of predicting severe cervical spine injury in simulated crash scenarios, with future applications in sports injury prevention and protective equipment.