Objective: To develop modular software to assess angular impulse and to determine the effect of a reduced dataset on the net angular impulse acting at the L5/S1 joint. Background. With the prevalence and incidence of lower back pain increasing annually, accurate assessment of physical job demands is needed. Many lab based approaches exist to measure the moments acting on the lower back, but require advanced and sensitive testing equipment. Of the methodologies currently used in industrial settings, most require significant contributions of time or money to be implemented. There is a need for cost and time effective methods to record a worker’s kinematic data over their whole shift. Methods: Twelve participants performed 12 consecutive lifts under five lifting conditions: SQ00 (squat 0kg); SQ04 (squat 4kg); SQ10 (squat 10kg); FP04 (fast squat 4kg); ST04 (stoop 4kg). Kinematic data of the upper limbs, head, and trunk was recorded with external load data and kinetic analysis was performed by implementing an extension of the Hof (1992) method called the lined-segment engine (LSE) to calculate the angular impulse (N•m•s) acting on the L5/S1 joint. Results: The LSE was sensitive to changes in load, lifting speed, and lifting posture (p < 0.05). There was no difference in dynamic, quasi-static, or static models when calculating angular impulse, but there was a difference in the L5/S1 angular impulse when the upper limbs were removed from the dynamic LSE model (p < 0.05). Conclusion: The LSE requires further refinement, but could be a generic approach to kinetic calculations. A scaled no-arms model for calculating the angular impulse acting on the low back could be used to assess field based lifting studies with 5.8% error. / Thesis (Master, Kinesiology & Health Studies) -- Queen's University, 2013-08-03 15:05:03.257

Spine needle injections are widely applied to alleviate pain and to remove nerve sensation through anesthesia. Current treatment is performed either blindly having no image guidance or using fluoroscopy or computed tomography (CT). Both CT and fluoroscopy guidance expose patients to ionizing radiation. Alternatively, ultrasound (US) guidance for spine needle procedures is becoming more prevalent since US is a non-ionizing and more accessible image modality. An inherent challenge to US imaging of the spine is the acoustic shadows created by the bony structures of the vertebra limiting visibility. It is challenging to use US as the sole imaging modality for intraoperative guidance of spine needle injections. However, it is possible to enhance the anatomical information through a preoperative diagnostic CT. To achieve this, image registration between the CT and the US images is proposed in this thesis. Image registration integrates the anatomical information from the CT with the US images. The aligned CT augments anatomical visualization for the clinician during spinal interventions. To align the preoperative CT and intraoperative US, a novel registration pipeline is presented that involves automatic global and multi-vertebrae registration. The registration pipeline is composed of two distinct phases: preoperative and intraoperative. Preoperatively, artificial spring points are selected between adjacent vertebrae. Intraoperatively, the lumbar spine is first aligned between the CT and US followed by a multi-vertebrae registration. The artificial springs are used to constrain the movement of the individually transformed vertebrae to ensure the optimal alignment is a pose of the lumbar spine that is physically possible. Validation of the algorithm is performed on five clinical patient datasets. A protocol for US data collection was created to eliminate variability in the quality of acquired US images. The registration pipeline was able to register the datasets from initial misalignments of up to 25 mm with a mean TRE of 1.17 mm. From these results, it is evident that the proposed registration pipeline offers a robust registration between clinical CT and US data. / Thesis (Master, Computing) -- Queen's University, 2013-08-19 12:50:54.521

Overloading of the back can cause instability such that buttressing the instability is a primary objective of many of the leading edge therapeutic approaches. However, a challenge lies in determining the location of the instability or the least stable vertebral joint. A mathematical analysis, based on a commonly used approach in engineering for determining structural stability, has been developed for the lumbar spine. The purpose of this investigation was to determine the feasibility of a method for mathematically locating potential areas of instability within a computer-based model of the lumbar spine. To validate this method, the eigenvector from the stability analysis was compared to the output from a geometric equation that approximated individual vertebral joint rotational stiffness with the idea that the entry in the eigenvector with the largest absolute value would correspond to the vertebral joint and axis with the lowest stiffness. Validation of the eigenvector was not possible due to computational similarities between the stability analysis and the geometric rotational stiffness method. However, it has been previously demonstrated that the eigenvector can be useful for locating instability, and thus warrants future study. Determining the least stable vertebral joint and axis can be used to guide proper motor pattern training as a clinical intervention. It was also shown in this investigation that an even distribution of fascicle force and stiffness generated stability. This supports the idea that well-coordinated efforts of muscle activation are beneficial for improving stability of the lumbar spine.

A dissertation submitted in partial compliance with the requirements for a Master's Degree in Technology: Chiropractic, Durban Institute of Technology, 2006. / This research study was designed in the form of a quantitative, non-experimental, empirical clinical survey. Objectives: 1) To determine the period prevalence (1 January 1997 – 31 December 2004) of congenital cervical spine anomalies. 2) To determine if there is any association between the presenting clinical features and the congenital cervical spine anomalies in general. 3) To determine if there is any association between the presenting clinical features and individual congenital cervical spine anomalies. 4) To compare subjects presenting clinical features with reported clinical features from literature. / M

The main object of study in this thesis is branching Brownian motion, in which each particle moves like a Brownian motion and gives birth to new particles at some rate. In particular we are interested in where particles are located in this model at large times T : so, for a function f up to time T , we want to know how many particles have paths that look like f. Additive spine martingales are central to the study, and we also investigate some simple general properties of changes of measure related to such martingales.

BACKGROUND: The psoas major is an important muscle that is part of the iliopsoas complex, which is also known as the hip flexor and contains a major web of nerves called the lumbar plexus. The location of the lumbar plexus within the psoas muscle has been studied on cadaveric dissections previously, particularly with respect to the location of the L4 nerve root but the effect of posture on psoas morphology has not previously been studied. Hip flexion along with the potential changes in spinal alignment while in an upright sitting position may cause significant changes in the positioning and geometry of the psoas and may also change the orientation of the lumbar plexus within the muscle. Current controversy exists in determining patient suitability for Lateral Lumbar Interbody Fusion (LLIF) based on psoas morphology. Oblique and trans-psoas approaches have become a popular minimally invasive lumbar fusion technique in recent years. Lumbar plexus injury, particularly L4 nerve root injury, is a known potential complication of the oblique and trans-psoas approach and may be minimized by careful assessment of the psoas anatomy preoperatively. Quadriceps weakness as a result of L4 nerve root injury is a known potential complication of the trans-psoas approach and may be minimized by careful assessment of the psoas anatomy preoperatively. Patients may present with a sitting MRI rather than supine MRI, however, the effect of posture on the geometry of the psoas muscle, and therefore of the lumbar plexus, has not been previously reported. METHODS: We conducted a retrospective review of a single-spine surgeon practice over a 6-month period to identify patients who had undergone MRI of the lumbar spine for evaluation of degenerative spinal pathologies. Male and female patients were included if aged between 18-90 years presenting with degenerative lumbar spinal pathology between 2015-2016, and excluded if they had previous lumbar fusion, scoliosis, diagnosed with neuromuscular disease, were skeletally immature or had intrinsic abnormalities of the psoas muscles (e.g. tumor, infection or trauma). The anteroposterior (AP) dimension of the psoas muscle was measured at each disc space from L1 to L5 and compared to the AP dimension of the intervertebral disc, as measured at the inferior vertebral endplate. The AP psoas:disc ratio was then calculated and compared between patients undergoing sitting and/or supine MRIs. RESULTS: With a total of 269 patients, 113 of them were male and 157 were female. 209 patients were identified with supine-, and 60 patients with sitting- MRIs, of which 13 patients had undergone both sitting and supine MRIs (BOTH group). A propensity score match (PSM) was performed for patients undergoing either a supine or sitting MRI to match for age, BMI and gender to produce two groups of 43 patients. In the BOTH and PSM group, the sitting MRIs displayed significantly higher AP psoas:disc ratio compared with the supine MRIs at all intervertebral levels except L1-L2. The largest difference observed was a mean 32-37% increase in sitting AP psoas:disc ratio at the L4-L5 disc in sitting MRIs compared to supine MRIs in the BOTH group (range 0-137%). CONCLUSIONS: The psoas muscle and the lumbar plexus became anteriorly displace in sitting MRIs, with a greater effect noted at caudal intervertebral discs. This may have implication in selection suitability for LLIF and intra-operative patient positioning.

Advancements in computational power and micro-imaging has allowed the creation of finite element (FE) models on a microstructural level that can represent complex skeletal structures. These µFE models can analyze the structural integrity of individual trabeculae and may be used to model the impact of complex pathologies on skeletal stability. This thesis aims to: 1) optimize the histological identification of microdamage in healthy and mixed metastatic whole rat vertebrae, 2) quantify trabecular level stress and strain using µFE models and deformable registration generated from µCT data and 3) evaluate stress and strain in µFE models comparing undamaged regions with areas of mechanically induced microdamage. This novel technique allows the histological identification of microdamage in whole vertebrae with accurate alignment to 3D μCT data sets. In the μFE models, significantly higher stresses and strains were found in areas of damaged bone in both healthy and metastatically involved vertebrae.

Advancements in computational power and micro-imaging has allowed the creation of finite element (FE) models on a microstructural level that can represent complex skeletal structures. These µFE models can analyze the structural integrity of individual trabeculae and may be used to model the impact of complex pathologies on skeletal stability. This thesis aims to: 1) optimize the histological identification of microdamage in healthy and mixed metastatic whole rat vertebrae, 2) quantify trabecular level stress and strain using µFE models and deformable registration generated from µCT data and 3) evaluate stress and strain in µFE models comparing undamaged regions with areas of mechanically induced microdamage. This novel technique allows the histological identification of microdamage in whole vertebrae with accurate alignment to 3D μCT data sets. In the μFE models, significantly higher stresses and strains were found in areas of damaged bone in both healthy and metastatically involved vertebrae.

Low back pain is highly prevalent in the developed world, with 80% of the population being affected at some point in their lives. Herniation, a common injury to the intervertebral disc, is characterized as the posterior migration of the nucleus pulposus through the layers of the annulus fibrosus. Various risk factors have been associated with the development of disc herniation, but the mechanisms are largely not understood. For example, exposure to vibration has been linked to the occurrence of herniation, yet our understanding of this association is not clear. It is hypothesized that vibration cyclically loads the tissues of the intervertebral disc until failure occurs as a result of fatigue. Tissues at risk of fatigue failure may include the intra-lamellar matrix, the connective tissue found between collagen fibres within a single lamella, and the inter-lamellar matrix, the connective tissue found between adjacent lamellae. In order to determine the mechanistic link between vibration and herniation, a firm understanding of the properties of the intervertebral disc as well as the intra and inter-lamellar matrices are of utmost importance. Further, it is important to determine these properties under physiological loading scenarios. This thesis consists of five studies, which have each provided a unique piece to the intervertebral disc herniation puzzle in order to better understand this mechanistic link. First, it was discovered that annular tissue is subject to significantly higher stresses and is stiffer under biaxial strain as compared to uniaxial strain. Biaxial strain is more representative of the in vivo loading scenario and provides more accurate information regarding scenarios that the annulus can tolerate and those that can result in injury. It was also revealed that, when strained at physiological strain rates (up to 4%/sec), these mechanical properties do not change such that they are independent of strain rate. Therefore, when strained at varying rates akin to voluntary movement, the annulus is not subject to higher stresses or altered stiffness. Second, the effect of vibration, an acknowledged risk factor for herniation, was examined on the mechanical properties of the intra and inter-lamellar matrices. It was discovered that vibration altered these matrices such that they were more extensible and strained to greater magnitudes, yet did not reach higher stresses before failing. It was hypothesized that this increased extensibility was due to damage to elastin, as elastin assists in minimizing tissue deformation and helps tissues recover from tensile strain. The final study assessed the effect of exposure to vibration on the development of disc herniation. The initiation of herniation was observed in a significantly greater number of intervertebral discs exposed to vibration as compared to a control condition. Although epidemiological studies had documented a correlation between exposure to vibration and herniation, this was the first study to conclude that exposure to vibration is in fact a mechanical risk factor for the development of herniation and increases the incidence of herniation. Further, based on the findings of the mechanical properties of the intra and inter-lamellar matrices, and in particular the observed 15-20 times greater failure strength of the intra as compared to inter-lamellar matrix, it would appear that the inter-lamellar matrix, and thus delamination, may be the weakest link in the herniation pathway. This thesis has uncovered new information regarding physiological mechanical properties of the annulus. Further, new information regarding the intra and inter-lamellar matrices was obtained, improving our understanding of the healthy disc. Last, by subjecting the disc to a known risk factor for herniation, hypotheses were generated regarding the initiation and progression of disc herniation, specifically related to the roles of the intra and inter-lamellar matrices.

General body discomfort increases over time during prolonged sitting and it is typically accepted that no single posture can be comfortably maintained for long periods. Despite this knowledge, workplace exposure to prolonged sitting is very common. Sedentary occupations that expose workers to prolonged sitting are associated with an increased risk of developing low back pain (LBP), disc degeneration and lumbar disc herniation. Given the prevalence of occupations with a large amount of seated work and the propensity for a dose-response relationship between sitting and LBP, refining our understanding of the biomechanics of the lumbar spine during sitting is important. Sitting imposes a flexed posture that, when held for a prolonged period of time, may cause detrimental effects on the tissues of the spine. While sitting is typically viewed as a sedentary and constrained task, several researchers have identified the importance of investigating movement during prolonged sitting. The studies in this thesis were designed to address the following two global questions: (1) How do the lumbar spine and pelvis move during sitting? (2) Can lumbar spine movement and postures explain LBP and injury associated with prolonged sitting? The first study (Study 1) examined static X-ray images of the lower lumbo-sacral spine in a range of standing and seated postures to measure the intervertebral joint angles that contribute to spine flexion. The main finding was that the lower lumbo-sacral joints approach their total range of motion in seated postures. This suggests that there could be increased loading of the passive tissues surrounding the lower lumbo-sacral intervertebral joints, contributing to low back pain and/or injury from prolonged sitting. Study 2 compared external spine angles measured using accelerometers from L3 to the sacrum with corresponding angles measured from X-ray images. While the external and internal angles did not match, the accelerometers were sensitive to changes in seated lumbar posture and were consistent with measurements made using similar technology in other studies. This study also provided an in-depth analysis of the current methods for data treatment and how these methods affect the outcomes. A further study (Study 3) employed videofluoroscopy to investigate the dynamic rotational kinematics of the intervertebral joints of the lumbo-sacral spine in a seated slouching motion in order to determine a sequence of vertebral motion. The pelvis did not initiate the slouching motion and a disordered sequence of vertebral rotation was observed at the initiation of the movement. Individuals performed the slouching movement using a number of different motion strategies that influenced the IVJ angles attained during the slouching motion. From the results of Study 1, it would appear as though the lowest lumbar intervertebral joint (L5/S1) contribute the most to lumbo-sacral flexion in upright sitting, as it is at approximately 60% of its end range in this posture. However, the results from Study 3 suggest that there is no consistent sequence of intervertebral joint rotation when flexing the spine from upright to slouched sitting. When moving from standing to sitting, lumbar spine flexion primarily occurs at the lowest joint (i.e. L5/S1); however, a disordered sequence of vertebral motion the different motion patterns observed may indicate that different joints approach their end range before the completion of the slouching movement. In order to understand the biomechanical factors associated with sitting induced low back pain, Study 4 examined the postural responses and pain scores of low back pain sufferers compared with asymptomatic individuals during prolonged seated work. The distinguishing factor between these two groups was their respective time-varying seated lumbar spine movement patterns. Low back pain sufferers moved more than asymptomatic individuals did during 90 minutes of seated work and they reported increased low back pain over time. Frequent shifts in lumbar spine posture could be a mechanism for redistributing the load to different tissues of the spine, particularly if some tissues are more vulnerable than others. However, increased movement did not completely eliminate pain in individuals with pre-existing LBP. The LBP sufferers’ seated spine movements increased in frequency and amplitude as time passed. It is likely that these movements became more difficult to properly control because LBP patients may lack proper lumbar spine postural control. The results of this study highlight the fact that short duration investigations of seated postures do not accurately represent the biological responses to prolonged exposure. Individuals with sitting-induced low back pain and those without pain differ in how they move during seated work and this will have different impacts on the tissues of the lumbar spine. A tissue-based rational for the detrimental effects on the spinal joint of prolonged sitting was examined in Study 5 using an in vitro spine model and simulated spine motion patterns documented in vivo from Study 4. The static protocol simulated 2 hours of sitting in one posture. The shift protocol simulated infrequent but large changes in posture, similar to the seated movements observed in a group of LBP sufferers. The fidget protocol replicated small, frequent movements about one posture, demonstrated by a group of asymptomatic individuals. Regardless of the amount of spine movement around one posture, all specimens lost a substantial amount of disc height. Furthermore, the passive range of motion of a joint changed substantially after 2 hours of simulated sitting. Specifically, there were step-like regions of reduced stiffness throughout the passive range of motion particularly around the adopted “seated flexion” angle. However, small movements around a posture (i.e. fidgeting) may mitigate the changes in the passive stiffness in around the seated flexion angle. The load transferred through the joint during the 2-hour test was varied either by changing postures (i.e. shifting) or by a potential creep mechanism (i.e. maintaining one static posture). Fidgeting appeared to reduce the variation of load carriage through the joint and may lead to a more uniform increase in stiffness across the entire passive range of motion. These changes in passive joint mechanics could have greater consequences for a low back pain population who may be more susceptible to abnormal muscular control and clinical instability. Nevertheless, the observed disc height loss and changes in joint mechanics may help explain the increased risk of developing disc herniation and degeneration if exposure to sitting is cumulative over many days, months and years. In summary, this work has highlighted that seated postures place the joints of the lumbar spine towards their end range of motion, which is considered to be risky for pain/injury in a number of tissue sources. In-depth analyses of both internal and external measurements of spine postures identified different seated motion patterns and self-selected seated postures that may increase the risk for developing LBP. The model of seated LBP/discomfort development used in this thesis provided evidence that large lumbar spine movements do not reduce pain in individuals with pre-existing LBP. Tissue-based evidence demonstrated that 2 hours of sitting substantially affects IVJ mechanics and may help explain the increased risk of developing disc herniation and degeneration if exposure to sitting is cumulative over many days, months and years. The information obtained from this thesis will help develop and refine interventions in the workplace to help reduce low back pain during seated work.